The History of Neuroscience in Autobiography

VOLUME 7

The History of Neuroscience in Autobiography

VOLUME 7

Edited by Larry R. Squire

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Contents

Previous Contributors

Preface to Volume 1

Preface to Volume 7

Floyd E. Bloom

Joaquín Fuster

Michael S. Gazzaniga

Bertil Hille

Ivan Izquierdo

Edward Jones

Krešimir Krnjević

Nicole M. Le Douarin

Terje Lømo

Michael M. Merzenich

John Wilson Moore

Robert Y. Moore

Michael I. Posner

Peter H. Schiller

Gordon M. Shepherd

Robert H. Wurtz

Index of Names

Previous Contributors

Volume 1

Denise Albe-Fessard

Julius Axelrod

Peter O. Bishop

Theodore H. Bullock

Irving T. Diamond

Robert Galambos

Viktor Hamburger

Sir Alan L. Hodgkin

Herbert H. Jasper

Sir Bernard Katz

David H. Hubel

Seymour S. Kety

Benjamin Libet

Louis Sokoloff

James M. Sprague

Curt von Euler

John Z. Young

Volume 2

Lloyd Beidler

Arvid Carlsson

Donald Griffin

Roger Guillemin

Ray W. Guillery

Masao Ito

Martin Larrabee

Jerry Lettvin

Paul MacLean

Brenda Milner

Karl Pribram

Eugene Roberts

Gunther Stent

Volume 3

Morris H. Aprison

Brian B. Boycott

Vernon B. Brooks

Pierre Buser

Hsiang-Tung Chang

Claudio A. Cuello

Robert W. Doty

Bernice Grafstein

Ainsley Iggo

Jennifer Lund

Edith and Patrick McGeer

Edward R. Perl

Donald B. Tower

Patrick D. Wall

Wally Welker

Volume 4

Per Andersen

Mary Bartlett Bunge

Jan Bures

Jean Pierre G. Changeux

William Maxwell (Max) Cowan

John E. Dowling

Oleh Hornykiewicz

Andrew F. Huxley

JacSue Kehoe

Edward A. Kravitz

James L. McGaugh

Randolf Menzel

Mircea Steriade

Richard F. Thompson

Volume 5

Samuel H. Barondes

Joseph E. Bogen

Alan Cowey

David R. Curtis

Ennio De Renzi

John S. Edwards

Mitchell Glickstein

Carlton C. Hunt

Lynn T. Landmesser

Rodolfo R. Llinás

Alan Peters

Martin Raff

Wilfrid Rall

Mark R. Rosenzweig

Arnold Bernard Scheibel

Gerald Westheimer

Volume 6

Bernard W. Agranoff

Emilio Bizzi

Marian Cleeves Diamond

Charles G. Gross

Richard Held

Leslie L. Iversen

Masakazu Konishi

Lawrence Kruger

Susan E. Leeman

Vernon B. Mountcastle

Shigetada Nakanishi

Solomon H. Snyder

Nobuo Suga

Hans Thoenen

Preface to Volume 1

Before the Alfred P. Sloan Foundation series of books began to appear in 1979, the scientific autobiography was a largely unfamiliar genre. One recalls Cajal’s extraordinary Recollections of My Life, translated in English in 1937 and the little gem of autobiography written by Charles Darwin for his grandchildren in 1876. One supposes that this form of scientific writing is scarce because busy scientists would rather continue to work on scientific problems than to indulge in a retrospective exercise using a writing style that is usually outside their scope of experience. Yet, regardless of the nature of one’s own investigative works, the scientific enterprise describes a community of activity and thought in which all scientists share. Indeed, an understanding of the scientific enterprise should in the end be accessible to anyone, because it is essentially a human endeavor, full of intensity, purpose, and drama that are universal to human experience.

While writing a full autobiographical text is a formidable undertaking, preparing an autobiographical chapter, which could appear with others in a volume, is perhaps less daunting work and is a project that senior scientists might even find tempting. Indeed, a venture of this kind within the discipline of psychology began in 1930 and is now in eight volumes (A History of Psychology in Autobiography). So it was that during my term as President of the Society for Neuroscience in 1993 to 1994, I developed the idea of collecting autobiographies from senior neuroscientists, who at this period in the history of our discipline are in fact pioneers of neuroscience. Neuroscience is quintessentially interdisciplinary, and careers in neuroscience come from several different cultures, including biology, psychology, and medicine. Accounts of scientific lives in neuroscience hold the promise of being informative and interesting, and they could be a source of inspiration to students. Moreover, personal narratives provide for scientists and nonscientists alike an insight into the nature of scientific work that is simply not available in ordinary scientific writing.

This volume does have a forerunner in neuroscience. In 1975, MIT Press published The Neurosciences: Paths of Discovery, a collection of 30 chapters in commemoration of F. O. Schmitt’s 70th birthday, edited by F. Worden, J. Swazey, and G. Adelman. The contributing neuroscientists, all leaders of their discipline, described the paths of discovery that they had followed in carrying on their work. While writing in the style of the conventional review article, some authors did include a good amount of anecdote, opinion, and personal reflection. A second, similar volume, The Neurosciences: Paths of Discovery II, edited by F. Samson and G. Adelman, appeared in 1992.

In any case, neuroscience writing that is deliberately and primarily autobiographical has not been collected before. This project, The History of Neuroscience in Autobiography, is the first major publishing venture on the Society for Neuroscience after The Journal of Neuroscience. The book project was prepared with the active cooperation of the Committee on the History of Neuroscience, which serves as an editorial board for the project. The first chairperson of the committee was Edward (Ted) Jones; its members were Albert Aguayo, Ted Melnechuk, Gordon Shepherd, and Ken Tyler. This Group compiled the names and carried out the deliberations that led to the first round of invitations. In 1995 Larry Swanson succeeded Ted Jones as chair of the committee, and as we go to press with Volume 1 the committee members are Albert Aguayo, Bernice Grafstein, Ted Melnechuk, Dale Purves, and Gordon Shepherd.

In the inaugural volume of the series, we are delighted to be able to present together 17 personal narratives by some of the true pioneers of modern neuroscience. The group includes four Nobel Laureates and 11 members or foreign associates of the National Academy of Sciences, USA. The contributors did their scientific work in the United States, Canada, England, Australia, France, and Sweden. It is difficult to imagine a finer group of scientists with which to inaugurate our autobiographical series. The autobiographical chapters that appear here are printed essentially as submitted by the authors, with only light technical editing. Accordingly, the chapters are the personal perspectives and viewpoints of the authors and do not reflect material or opinion from the Society for Neuroscience.

Preparation of this volume depended critically on the staff of the book’s publisher, the Society for Neuroscience. The correspondence, technical editing, cover design, printing, and marketing have all been coordinated by the Society’s Central Office, under the superb direction of Diane M. Sullenberger. I thank her and her assistants Stacie M. Lemick (publishing manager) and Danielle L. Culp (desktop publisher) for their dedicated and skillful work on this project, which was carried out in the midst of demands brought by the first in-house years of the Society’s Journal of Neuroscience. I also thank my dear friend Nancy Beang (executive director of the Society for neuroscience) who from the beginning gave her full enthusiasm to this project.

Larry R. Squire
Del Mar, California
September, 1996

Preface to Volume 7

This seventh volume of The History of Neuroscience in Autobiography includes 16 chapters by senior neuroscientists. The authors tell about the experiences that shaped their lives; the teachers, colleagues, and students with whom they worked; and the scientific work that has absorbed them during their careers. Their stories relate a lifetime of investigation and discovery. We are particularly fortunate to be able to include a contribution from Edward (Ted) Jones, who passed away on June 6, 2011.

Volume 7 was prepared with the advice of the Publications Committee of the Society for Neuroscience, which serves as editorial board for the project. With input from the Committee, from the Council of the Society for Neuroscience, and from many others, names were compiled for this volume.

At the Society for Neuroscience, Suzanne Rosenzweig (Director, Scientific Publications) assisted with the project. Although the volumes are official publications of the Society for Neuroscience, Oxford University Press has been a partner in the project since 2008 and has coordinated the technical editing, printing, and marketing. One year after publication, the contents of this volume will be posted on the Society’s Web site, under Publications, where one can also find the 89 autobiographical chapters that appeared in the first six volumes. The work proceeded under the capable direction of Craig Panner (Executive Editor, Neuroscience and Psychology at Oxford University Press), Kathryn Winder (Assistant Editor), Karen Harmon (Senior Production Editor), and Smitha Raj (Project Manager). I hope readers will find Volume 7 as interesting and useful as the earlier volumes.

Larry R. Squire
Del Mar, California
March, 2011

Floyd E. Bloom

BORN:

Minneapolis, Minnesota

October 8, 1936

EDUCATION:

Southern Methodist University, A.B., cum laude (1956)

Washington University, School of Medicine, M.D., cum laude (1960)

APPOINTMENTS:

Intern and First Year Assistant Resident, Ward Medical Service, Barnes Hospital, St. Louis (1960–1962)

Research Associate, NIMH at St. Elizabeths Hospital (1962–1964)

Yale University, USPHS Special Postdoctoral Fellow in Anatomy (1964–1966); Assistant Professor Pharmacology, Anatomy, and Psychiatry (1966–1967); Associate Professor (1968)

Chief, Laboratory of Neuropharmacology, Division of Special Mental Health Research Programs, NIMH (1968–1975); Acting Director Division of Special Mental Health Research Programs (1973–1975)

Director, Arthur V. Davis Center for Behavioral Neurobiology, The Salk Institute (1975–1983)

The Scripps Research Institute (1983–present) Director Division of Preclinical Neuroscience and

Endocrinology (1983–1989); Chairman Department of Neuropharmacology (1989–2005); Professor Emeritus (2005–present)

HONORS AND AWARDS (SELECTED):

President, Society for Neuroscience (1976–1977); American College of Neuropsychopharmacology (1988–1989); Research Society for Alcoholism (1991–1993)

A. Cressy Morrison Award (1971)

Arthur S. Flemming Award (1972)

National Academy of Sciences (1977)

Institute of Medicine (1982); Council (1986–1989)

Doctor of Science, hon. caus., Southern Methodist University (1983)

Doctor of Science, hon. caus., Hahnemann University, Philadelphia (1985)

Doctor of Science, hon. caus., University of Rochester, New York (1985)

Distinguished Fellow, American Psychiatric Association (1986)

Foreign Member, Royal Swedish Academy of Sciences (1989)

American Philosophical Society (1989)

Doctor of Science, hon. caus., Mt. Sinai School of Medicine, New York, NY (1996)

Honorary Doctor of Science, Thomas Jefferson University, Philadelphia (1997)

Doctor of Science, hon. caus., Washington University (1998)

Rhoda and Bernard Sarnat International Prize in Mental Health, Institute of Medicine (2005)

Floyd Bloom began his biomedical research career with investigations of the conduction properties of single isolated axons, and he transitioned to single neuron pharmacology in the early applications of microiontophoresis. Bloom was among the first to study neurotransmitter systems at the anatomical, physiological, and pharmacological levels beginning with the noradrenergic innervation of cerebellum, hippocampus, and cerebral cortex. He was one of the first neurobiologists to utilize modern molecular biological techniques to identify, functionally characterize, and map brain specific genes. Recognizing the value of computers in neuroscience, he pioneered their application to neuroanatomic investigations and the development of neuroanatomic databases. His work has found considerable applicability to many enigmatic disorders of the nervous system, such as the addictive states, the dementias, and the major psychoses. From 1995 to 2000, he was Editor-in-Chief of Science.

Floyd E. Bloom

Introduction

The reason I agreed to write this autobiographical review of my scientific career was to be able to recognize publicly the many mentors and colleagues who helped me succeed at so many of the endeavors I chose to pursue. I hope to identify the key events and the stand-out individuals and recall what I can about the critical decision points along the way. I consider myself a physician-scientist, who followed some minor deviations into molecular and cellular neuroscience in the middle of my hands-on period of bench work. For the last decade or two, I have worked less with my hands and more as a lab leader and statesman for my areas of neuroscience. I shall endeavor to avoid what Sigmund Freud referred to as the mendacity of most autobiographical works, while enjoying the brief retrospective of summarizing my career.

Background and Schooling

My earliest memory as a child was listening to Franklin Delano Roosevelt on the radio addressing Congress with the declaration of war on Japan the day after their attack on Pearl Harbor. I had turned 5 years old just a couple of months earlier, but the look on my parents’ faces told me this was an extremely important event. Three days later, we declared war on Germany and Italy, and my parents told me this was World War II. The home we lived in was not ours, but rather the home of Andrew and Catherine Johnson, a plumber and his wife who had been willing to take boarders into their home in suburban Minneapolis. Catherine was my surrogate mom, while both my parents worked in two small pharmacies a few blocks away.

My dad was the first member of his family to complete a college education, and his three brothers and two sisters did likewise, which was quite an accomplishment for their father who supported the family working as a freight handler for the railroad. Two of my dad’s brothers followed his lead to become pharmacists, and the third became a dentist. My mom, who had been born in Russia and immigrated to America at the age of 9, came from an even poorer family and had to go work before she finished high school. When they married, they considered themselves too poor to start a family and waited 7 years before I was born. Their patterns of hard work, long hours, and scrupulous honesty in business matters were my gold standards of behavior. My dad had wanted to go to medical school and, whether he had the grades to make it there he never really said, but he viewed pharmacy as a close alternative and thought highly of the medical profession his whole career.

As I entered elementary school, I can dimly recall selling War Savings Stamps, marching with my classmates in parades to raise money for War Bonds, and using rationing stamps for grocery items. Within a year, my dad’s dentist brother enlisted in the Navy and was assigned to the First Marine Division. On weekends my dad would take me to see the war newsreels to try to spot Uncle Harvey doing dental work in Guadalcanal after the beach head there had been established. The only real war hardship I recall was from gasoline rationing, which curtailed our regular Sunday automobile trips with my dad’s parents to a point where there was barely enough time to hear the whole Jack Benny show and a part of Fred Allen on the car radio before we were back home.

After World War II ended, my dad sold his two stores, and we took some very long car trips through the Dakotas and Montana. When we returned to Minneapolis, my dad decided to join his next younger pharmacist brother Stanley in Dallas; Uncle Stanley had moved there in the final days of the war and from his perspective Dallas could use another good drug store. The youngest pharmacist brother, Jerry, came along to work in my dad’s store. In 1946, we moved to a new house in a new city. I was devastated to leave all my friends behind and face a whole new class of students that I didn’t know at all. Dallas in the summer was extremely hot. My mom’s brother-in-law, Uncle Abe, who also lived in Dallas ran what I think now was a war surplus store that sold fixtures and furniture to small businesses. That first summer, I worked for him assembling metal stools with screws that got so hot in the Texas sun that I couldn’t pick them up.

When I started school that fall at Stonewall Jackson Elementary, it quickly became apparent to my teachers that everything they were about to instill in me in the fifth grade in Dallas, I had already learned in the fourth grade in Minneapolis. As a result, I was advanced a half year, into a much smaller group of students who either because of their birthdays or prior failures were set back from the annual classes. I stayed a half-year out of synch with my age peers for the rest of my public education, graduating high school in the winter of 1953.

I cannot pass over the 6 years of junior high (Alex Spence Junior High) and high school (Woodrow Wilson High School) because those years shaped both my mind and my body. In junior high, my pubertal growth spurt came early among my male classmates and for the eighth grade, I was suddenly a big fellow. I tried out for and made the football team, playing left guard on defense, although not very well. When we started into ninth grade in high school, all my classmates had had their growth spurts, and it was clear that I would no longer be competitive in football. However, as that first spring rolled around, and students were trying out for the baseball team, Coach Helms, who taught business accounting, asked me to become the freshman team student manager (also known pejoratively as a “water boy”), an assignment I readily accepted because it was clear I had little promise as a player.

Becoming student manager was probably the best move I could ever have made. When, after a month of practice, we still had all the baseballs, towels, and bats, Coach Helms began to think I could also do the job for the junior varsity, and then asked me back to do that for the varsity team the next year. I ended up with three letters in baseball, which also gave me entry to the manager position for our school’s football team, where I ended up with two more letters before graduation. That senior year was really very exciting because our football team won the Dallas city Championship, and then went two more rounds to the state semifinals. I made a lot of good friends among the athletes and got to know the cheerleaders pretty well too. I never lost a jersey.

For my senior English class, I decided to do a report based on a survey of the student managers at about 18 big-time colleges, writing them a series of questions to pose problems I had encountered as a manager for our high school team. Surprisingly, at least to me, more than a dozen replies came in and I recall that my English teacher and Coach Riley, the head coach of the football team, were very impressed. I finished second in my class, although I thought my grades in algebra, chemistry, and physics should have been weighted more heavily than the home economics and accounting classes that the valedictorian took.

My high school did not have career counseling, but they did provide some guidance in the form of aptitude tests. My test scores were interpreted to mean that I should pursue subjects like public relations, advertising, or journalism and avoid hard science and mathematics. Before passing that valuable information on to my parents, I first did some research and found that the closest School of Journalism that was highly regarded was the University of Missouri. I had an admissions application mailed to me and when it arrived I informed the folks. My dad’s reaction was that the idea was interesting and, as soon as I finished medical school, I could pursue any career I wanted to. Having worked as a helper in my dad’s pharmacy throughout my teenage years, I knew a lot of doctors that he served and admired many of them. So we went on to plan B.

Coach Riley was said to have been a member of the 1935 Rose Bowl team from Southern Methodist University, and he suggested not only that I apply there, but that he would back me to become a student manager for their football team. In those days, applying to SMU meant going over and paying my starting tuition—no SATs, no interviews, no essays, just money. Once I was accepted for admission to the winter term in 1954, I decided to wait until the fall to see how I did with my premed classes before talking to anyone about being a collegiate sports manager. It’s good that I waited, because the first class I took to complete my medical school application requirements was Physics, and the only course I could get into was Physics for Engineers. While I had done well in algebra and geometry in high school, calculus had not been offered. Unfortunately for me, the Physics for Engineers course relied heavily on calculus-based formulas, and I was very lucky to get through the course with a C, giving myself quite a grade point average handicap as I edged toward medical school.

Fortunately, one of the courses I did really well in was German, and after I got my first A, I decided to double up on German courses and ended up with a major in German Literature. That, plus good grades in all my chemistry and biology courses and the rest of my curriculum, helped me get my grade point average up to 3.6. In fact I was so proficient in German that I renewed my contact with athletics and became a tutor to the members of the varsity basketball team in 1955—the first year that SMU made it to the NCAA final four. One of my students was the All-American Center, Jim Krebs. By going to school every summer, and taking evening courses at the downtown branch of SMU (Dallas College), I was able to take the Medical Course Aptitude Tests in order to apply to medical school in the fall of 1955 for admission in the fall of 1956, completing my B.A. degree by August 1956, 2½ years after entering.

The main gatekeeper for all premed students at SMU was our Organic Chemistry Professor, Harold Jeskey. Next to Coach Riley, he was the most important mentor of my young career. He used to lecture in a long brown chemist’s lab coat and always wore a bright red four-in-hand tie except on the days when he gave exams when the tie was black (see Fig. 1.1). His lectures were more than organic chemistry—every reaction he described included some of the history of the chemist who created it, and the philosophy of the applications to which the reaction had already been put, always delivered with sly humor and always without any notes at all.

Because I did well in the first half of his course, Dr. Jeskey wrote very positive letters of support for my medical school applications and in the spring of 1956 I was accepted to Washington University in St. Louis. Washington University even then was a highly ranked medical school, and with my SMU classmate Alan Eberstein, we were only the third and fourth SMU students ever to be accepted there. Dr. Jeskey remained a loyal supporter of my career and, when I returned to Dallas on holidays, I made it a point to visit with him as did all his “boys” as he liked to call us. In 1967, the Red Tie Society of former Jeskey students started an endowed scholarship in his name, and that effort grew into the Jeskey Chair in Chemistry and a 98-seat Jeskey Lecture Hall in 2001. Although he retired from teaching in 1987, Dr. Jeskey continued to tutor freshman medical students in biochemistry at the University of Texas Southwestern Medical Center until his death in 2006 at the age of 94. Interestingly, in his final years he and my former Coach Riley lived in the same facility for senior citizens. His red tie is the reason that when ever I have an important talk to give, I feel insecure unless my bow tie contains a lot of red. I’ll mention the reason for the bow ties and the mustache later.

Fig. 1.1    Professor Harold A. Jeskey, R. S. Lazenby Professor of Chemistry at Southern Methodist University, 1912–2006, as photographed in 2005. Photo courtesy of Southern Methodist University.

My Years in St. Louis (1956–1962)

In the fall of 1956, married to my high school sweetheart, I packed my clothes, books, and a new microscope into a trailer and moved to St. Louis to begin medical school. The experience of learning about the biology of human health and disease at the level of intensity to which I was exposed was exhilarating, and the quality of the faculty was astounding. The first person I encountered on the day I walked up to store my microscope was a fragile older lady struggling to open the sliding safety door of the elevator—I later learned that she was Dr. Gertie Cori, a Nobelist, with her husband Carl. He later lectured us in their Cori cycle of energy movement from muscle to liver and back to muscle. An hour later, I met a second faculty member, Professor Sam Clark, who chatted with me amiably for a while and then encouraged me to get interested in advancing knowledge by pursuing the big questions with the best chance of getting clarifying answers—a lesson that has remained uppermost in my career pursuit of research.

However, in 1956, neuroscience as a field did not yet exist. We studied neuroanatomy in one course (for which Rita Levi-Montalcini came over from the undergraduate campus to describe her nerve growth factor), neurophysiology in another, and eventually neuropharmacology (led by Oliver Lowry, whose paper on the assay for protein is the most cited publication ever) in yet another. We were exposed to neurology (led by James O’Leary and Bill Landau) and psychiatry (led by Eli Robins, Sam Guze, George Winokur, and George Murphy) in two separate clinical clerkships. Although none of us students realized it at the time, the psychiatry group at Washington University was probably the most interesting because, under Robins leadership, their practice of psychiatry began to approach mental illness as medicine approached any other physical disease, using hard diagnostic and epidemiological criteria and the underlying preclinical science. Their work eventually led to the Diagnostic and Statistical Manual of Mental Disorders, used today throughout the world. On top of that, Robins also lectured us on the chemistry of neurotransmitters as freshmen in the neuroanatomy course.

However, my point of departure from all this excellence almost came in the neurophysiology section of the physiology course. The lectures in this course came after our daily lunch break, and the postprandial diversion of blood from brain to gut was not conducive to close scrutiny of the details being presented. To top off that physiological diversion, the detailed description of the recently reported Hodgkin-Huxley equations explaining how ion flow could result in the nerve action potential was totally developed in calculus, my once and continuing nemesis. Again, I passed, but only barely. After the exam, the lecturer for this section of the course, Professor Gordon Schoepfle, invited me into his laboratory for the summer to repeat the experiments of Hodgkin and Huxley so I could better understand the importance of these principles. Dr. Schoepfle was the last postdoctoral fellow of Nobelist Joseph Erlanger, who had described the properties of the compound action potential with the first laboratory oscilloscope. When I went into the Schoepfle lab that summer, there on his bench top was the axon wet chamber that Erlanger and his Nobel partner Herbert Gasser had used for their recordings. I was awestruck.

Schoepfle had developed his own method of studying ion flow in axons, the single air gap isolated node of Ranvier prepared from a microdissection of the frog sciatic nerve. He had hand-built his apparatus out of Plexiglas and a jeweler’s lathe to perform this analysis. After we went through those experiments watching action potential properties undergo dynamic shifts with changes in the ionic content of the physiological saline solutions, we went on to study Schoepfle’s main interest, the energy requirements of these ion movements. That summer’s work earned me co-authorship on a publication in the American Journal of Physiology and an invitation to return the next summer, which led to two further publications. As a senior, I was invited to be an Assistant Instructor in the Pharmacology course and to help prepare animals for the laboratory experiments. This gave me the chance to sit at lunch as Dr. Lowry listened to the faculty present progress reports on their work; while listening, he would compute the statistics in his head and tell them how many more animals they needed to make those differences meaningful. I was also able to do some independent work with local anesthetics from which I was able to assemble a research thesis between Physiology and Pharmacology that earned me a Cum Laude when I graduated.

Even now, some 50 years after graduating, I am blessed to recall many highlights from those 4 years of massive learning. In the Microbiology and Immunology course, led by Arthur Kornberg, we synthesized DNA and never realized how cutting edge this enzymatic reaction was. The next year, Kornberg took most of the Department with him to Stanford University’s new Medical School, including his postdoctoral fellow, Paul Berg. A year later Kornberg was awarded the Nobel Prize for his DNA studies, and in 1980 Paul Berg achieved the same recognition in Chemistry for his pioneering work in recombinant DNA. In our class, we drew each others’ blood and found out that more than half the class had already been exposed to the poliomyelitis virus before we took our first doses of the Salk vaccine. That part of the course was taught by Mel Cohn whom I encountered again two decades later when I joined the faculty at The Salk Institute.

Although medical school was probably as hard mentally as anything I had ever tried to do, my classmates were always ready to find the humorous side of student life. Early in our matriculation, we were asked to elect class officers but, since we had only just met each other, very few people knew more than 3 or 4 of the 85 members of the class—all men except for 5 women. One of those nominated for class vice president was Sam Farley; he didn’t win, but both in biochemistry and histology, his name became well known because after the exams the professors would ask the class to please urge “Mr. Farley” to come in for a conference (he never even seemed to come to class) so some tutoring could be offered to help with his failing grades. His exam books were often found with no answers at all. At the end of the year, many of us were surprised to learn that in fact Sam Farley didn’t exist at all, but was a hoax. Nevertheless, he stayed with us in spirit throughout the 4 years, and in our junior year when we were challenged to create an entertainment for the senior class and the faculty, our class did a parody of My Fair Lady that we called My Fair Farley, in which the Professor of Medicine wagered he could take anyone off the streets and make a passable Washington University medical student out of him. Those lyrics were a riot. When we graduated in 1960, Dean Edward Dempsey awarded Sam Farley his medical degree “sine laude,” and the class cheered. Recently, at the 50-year reunion of our graduating class, we voted unanimously to recommend to the Chancellor that Sam Farley be appointed a University Professor Demeritus.

The high point of the senior year was our clerkship on the Ward Medical Service, where we worked in teams of two pairs of students as subinterns on a very busy, very intense more-or-less public ward in Barnes Hospital. I found that if I wore a bow tie, I could draw the blood samples on my patients without blocking my field of view the way a long tie would when I leaned down, and I have stayed with that style of cravat ever since. Barnes Hospital was the elite medical service for the entire Midwest, and doctors whose patients’ illnesses could not be diagnosed or treated by them would routinely send their patients here. Since I aspired to an internship in internal medicine, I opted to take this clerkship early in my senior year so that I could ask my professors for letters of recommendation when applying in the late fall and winter for internships and residencies.

In my team of four were Paula Clayton, who went on to a distinguished career in academic psychiatry, later serving as President of the Psychiatric Research Society (1977–1978), the American Psychopathological Association (1981), and the Society of Biological Psychiatry (1986–1987); Mark Abramowicz, who trained in pediatrics at Boston Children’s Hospital and went on to become the Editor-in-Chief of the very highly regarded Medical Letter on Drugs and Therapeutics, and their several handbooks that prep physicians for the board exams and continuing medical education; and Louis Miller, elected to membership in the National Academy of Sciences for his work in malaria and defining the molecular receptor by which the parasite invades red blood cells, and who is currently the chief of the Laboratory of Parasitic Diseases at the National Institute of Allergy and Infectious Diseases.

With such comrades I also had to do well and I must have, for early in 1960, after completing my tour of interviews on the East Coast for possible internship posts at the University of Rochester, Yale, and Duke, Dr. Carl Moore, the Bixby Professor of Medicine, called me into his office on the eve of turning in our choices for preferred hospitals. He puffed on his pipe and stared at me in silence with a slight smile on his face, and he said that he hoped I had enjoyed my clerkship in medicine and that I was serious about going on to be trained in internal medicine. When I assured him I was, he said that they would like to include me in their choice of interns, and if I were also to rate Barnes as my number 1 choice, I would be assured of being selected. I was bowled over. Never had I imagined that I would be offered such an opportunity. I celebrated for the rest of the spring by taking my wife to Nassau and lying on the beach for 6 weeks to rest up for the next 2 years.

The internship year on the Ward Medical Service contrasted with the Private Medical Service, because all the attending physicians on the Ward Service were full-time academic faculty, and they were very serious and rigorous about teaching the house staff how to diagnose, treat, and otherwise manage whatever patients were admitted to our service. We were on call every other night for the entire year except for our 2 weeks of vacation, and for the 3 months when we worked in the outpatient clinics. My service routinely covered 18–20 patients, and it was not a rare day when 5 or more new patients were admitted. Learning how to handle all the various tests and evaluations in a fluid manner to keep hospitalizations to the minimum was an intense experience. I was very fortunate to be supervised in my initial weeks by a very wise but mild-mannered resident, Dr. Richard Aach, who would guide me mentally through the various diagnostic steps in the workup of each patient, and in such a way that I would be led to the best next step and think of it as my own insight. He also subtly guided me into setting up the testing in a logical manner so that every evening at our rounds we could determine what had been learned to confirm or alter our management of the patient.

Truly, that year was an exhausting but exhilarating experience, one which I am so pleased to have undertaken, and without which I may never have understood what I was capable of doing under the pressures of life and death. My most memorable case was a 16 year-old girl who had been seen in the dermatology clinic for a wart on the sole of her foot and had been given a month’s supply of Bismuth tablets. When it was time to come back for her first checkup, she realized she had not taken her pills as she was supposed to have and took all the rest of them at once. Her kidneys turned off and, when she was admitted to my ward, she was in early renal failure. Artificial kidney machines were not yet available, and we treated her with round-theclock intraperitoneal dialysis, infusing liters of sterile saline into her abdominal cavity, then after 2 hours lowering the bottles to drain out the fluid, now containing the urea, creatinine, and other catabolites that the kidneys should have filtered into the urine. After about a week of these treatments, her kidneys started to function again, and she walked out of the hospital healthy, but with that wart still on her foot. My intern partner on this vigil was William A. Peck from the University of Rochester, who went on to become the Dean of the Washington University School of Medicine.

In the spring of 1962, we lost one of our second-year residents who had been called into military duty because of the Berlin Crisis, early in President Kennedy’s term of office, and the Chief Resident J. Russell Little assigned me to take on his responsibilities. The Doctors Draft laws then in effect meant that a physician could be drafted into military service at any time up to the age of 45. This meant that, if one hoped to be able to complete an internship and residency uninterrupted by military service, additional effort needed to be expended. In my case, because of my Uncle Harvey, the Naval dentist, I had during college enlisted in the “Ensign 1999” program, which meant I would be commissioned an Ensign in the Naval Medical Corps when admitted to medical school and that I would get longevity credit going all the way back to my graduation from high school. While this seemed like an excellent step before I got into medical school, by the time I was a third-year student, the Navy began urging me to decide which Naval Hospital I wanted for my postgraduate education. By that time, although still inexperienced in the ways of academic medical training, I realized that my better opportunities were in academic hospitals, and not military hospitals. Thanks to Morris Odoroff, husband of my dad’s oldest sister (and the statistician for the first research studies showing the link between cigarette smoking and lung cancer), I was able to transfer my commission from the Navy to the U.S. Public Health Service at a moment when the Navy thought they had all the doctors they needed.

The spring of 1961 saw me off to the National Institutes of Health (NIH) to compete for a Research Associate post, the kind of external achievement that Dr. Moore and the Department of Medicine regarded as one of their criteria for deciding which of the five first-year residents would be invited back for one of the three second-year residency slots and a chance to become Chief Resident in Medicine in the third year of postinternship training. Going to NIH was initially going to be just a matter of going through the steps, because Dr. Schoepfle had arranged for me to work as a Research Associate with one his well-known contemporaries, Dr. Abraham Shanes. Shanes had just published a Pharmacological Reviews paper on the mechanisms of action of local anesthetics, the topic of my medical school thesis. When I arrived for my interviews, my pockets stuffed with photos of my research data, I was immediately bothered by the fact that Dr. Shanes was not on the list of NIH investigators I was scheduled to see.

When I got a brief break, I called Shanes, introduced myself, and asked whether he understood why I had not been scheduled to interview with him given that he and Schoepfle had a tacit agreement to take me. He paused and then said, “Oh, I’ve been meaning to call you. I’m leaving the NIH in a couple of months.” It turned out he had been diagnosed with cancer and wanted to earn a better salary for a year or two, not knowing what his future might be.

Of course, now I was dumbfounded as to what to do. Dr. Robert Berliner, who was then the head of the NIH Intramural Program and in charge of the Research Associate selection process, saw my distress and suggested I consider taking a taxi (more than $40 in those days) to St. Elizabeths Hospital in southwest Washington, DC, where the National Institute of Mental Health (NIMH) had established “some sort of neuropharmacological entity.” When I got there, I had the good fortune to be interviewed by Joel Elkes, the Director of the Clinical Neuropharmacology Research Center at St. Elizabeths. Elkes had been an early analyst of myelin, using X-ray diffraction, and so he was quite interested in my studies of single frog axons. After our chat, he took me to meet Gian-Carlo (Nino) Salmoiraghi, the head of the Section on Neurophysiology, an Italian M.D., who after the war and after service treating tuberculosis patients in the Red Cross, had done a Ph.D. in Neurophysiology at McGill University before coming to Washington. After he and I chatted pleasantly and favorably, I returned to St. Louis in a somewhat better frame of mind, and I was even more relieved to get a letter a few days later inviting me to accept a Research Associate slot with him for 2 years, from 1962 to 1964. Both Elkes and Salmoiraghi have been mentors to me ever since, and I was able to complete my 2 years of Internal Medicine training at Barnes, knowing that after NIH I could be in the competition for a second-year residency slot. That spring, I audited a calculus course on the undergraduate campus and finally began to understand what higher mathematics was all about.

St. Elizabeths Hospital (1962–1964)

When I first met Nino Salmoiraghi, his experimental focus had been to characterize with intracellular electrode recordings the neurons in the cat medulla that fired with inspiration and expiration and, having identified them, to give intra-arterial injections of drugs that would enhance or antagonize acetylcholine, then the only chemical considered for a role as a central neurotransmitter. It was tedious work of a kind I had never done, having spent my whole brief research life pithing frogs and taking out their sciatic nerves.

When I reported for duty in July 1962, Salmoiraghi was developing his own version of single-cell brain neuropharmacology, using an assembly of five fused microcapillary tubes, four grouped around a central tube, then drawn in the molten state to a common tip. Then, manually and under microscopic visualization, the tip was tapped on the end to fracture the sealed ends. When lucky, a new tip was created with five open channels. After opening the tip, the barrels were filled with solutions of chemicals to be tested, and then centrifuged at high speed to drive the solutions down into the tips of the pipets. With this device, measuring less than 5 micra at the tip, the assembly could be driven into the brain, the center barrel being used as a conventional extracellular recording electrode. Three of the other four barrels contained solutions of candidate natural substances to be tested as “putative” neurotransmitters, or solutions of drugs that would block the receptors that had been characterized for these putative agents. Since most such natural substances and their related drugs were either cations or anions in solution, the drugs could be ejected from the tip in an almost volumeless delivery by passing the proper polarity of current into the drug barrel. Salmoiraghi’s design employed the fourth barrel as a neutralizing current so that whatever polarity was used to eject the drugs would result in a zero net charge difference at the tip that was recording from the neuron being tested.

It seemed like a great system, a developmental effort that only the NIH’s Intramural Research Program could undertake with its instrument shop infrastructure and relatively limitless resources. Similar systems of microiontophoresis had been developed in Australia, Canada, and the United Kingdom without the use of the neutralizing control barrel, setting up grounds for differing results and scientific competition.

In the atmosphere of the NIMH Intramural Program, the biggest buzz had been the Catecholamine Hypothesis of Depression, promulgated by the Director of the Intramural Program, Seymour Kety, and one of his senior Fellows, Joseph Schildkraut. Their hypothesis in its simplest form was based on one of the founding principles of what today we call “biological psychiatry,” namely that drugs that affected human and experimental animal emotion in similar ways did so because of their similar neurochemical effects. The leading example in the early 1960s was the Indian antihypertensive drug reserpine. When given to animals, their hypokinetic and hypersedated demeanor was coupled with loss of both brain serotonin and norepinephrine. When depressed patients were examined, they showed loss of catecholamine catabolites in both their urine and in their cerebrospinal fluid. At the time I was a House Officer at Barnes, the Journal of the American Medical Association had published several studies from Europe indicating that patients treated for their hypertension with reserpine were showing increased frequency of suicide attempts.

When depressed animals and depressed patients were given monoamine oxidase inhibitors to slow catabolism of the amine, both groups showed improved emotional status and increased physical activity. A third piece of confirming evidence was that when the reserpine-treated subjects were given amphetamine or L-dihydroxyphenylalanine (L-DOPA), the precursor of norepinephrine, activity and levels of emotion were elevated, but there was no recovery when given 5-hydroxytryptophan, the precursor of serotonin. The hypothesis was that depression was the result of hypofunctioning brain norepinephrine circuits, while mania—the emotional opposite of depression—was the result of too much activity in norepinephrine circuits.

The only problem was that the evidence required to establish that norepinephrine was a neurotransmitter in the brain as it was in the sympathetic autonomic nervous system did not exist, and it was unclear from the neurochemical assays on grossly dissected brain regions where in the brain such synapses might be. So my first assignment was to use the microiontophoresis method to probe the hypothalamus, then considered to be the main central relay site for regulation of the autonomic nervous system, and characterize the actions of norepinephrine there.

The species of choice for single-cell recordings at that time was the cat, as cats could tolerate prolonged neurosurgical procedures to expose the regions of the brain or spinal cord that one sought to examine. Cats could also tolerate prolonged hypothermia, and that allowed the slowing of brain metabolism and the maintenance of good brain activity. Most of the John Eccles work on spinal physiology was done in cats that were very hypothermic. However, in the cat, the use of the five-barrel microelectrode assembly presented a major problem for studies on the hypothalamus—while narrow at the common tip and perhaps a centimeter or more above the common tip, the glass assembly quickly widened. To reach the hypothalamus from above was virtually impossible and would have created fatal major wounds in the overlying cortex and thalamus.

I therefore set about exposing the base of the cat brain through the roof of the mouth and pharynx. Several cats later, with the basic procedure working, I was able to collect data on maybe 50 neurons in the cat hypothalamus, divided into three anteroposterior levels, in which roughly one-third of the neurons showed their spontaneous discharge rates to be depressed when norepinephrine was applied, another one-third of neurons fired faster, and the final third did not respond at all. These data were uninterpretable, and we never published them except as an abstract for the Federation of American Societies for Experimental Biology, then known as FASEB, that met annually in Atlantic City to bring biochemists, physiologists, and pharmacologists together.

Although disappointed that my hard work in self-taught neurosurgery was for naught, two events occurred that helped rescue my productivity. A German physiologist, Rudolph Von Baumgarten, who was an expert in the physiology of the rabbit olfactory bulb—a much more easily accomplished dissection—came for my second summer. Soon we had healthier, more active animals to study, and a visible pathway—the lateral olfactory tract (LOT). Now we could stimulate, and thereby identify, our recording targets as mitral cells when the neurons we were recording from were antidromically activated by stimulation of the LOT. Here the responses were much more consistent, with norepinephrine uniformly depressing spontaneous activity and prolonging the depression that followed the antidromic stimulation. Even though we had no way to identify that norepinephrine-containing fibers innervated the mitral cells, we were able to put together consistent enough data to publish two reports on the system.

The second major event that brightened my early experiences with single-cell neuropharmacology was the decision by Erminio Costa, the Deputy Chief of the Bernard Brodie lab in the National Heart Institute, to come to St. Elizabeths several times a month and work with us, first on the pharmacology of norepinephrine in the rabbit olfactory bulb, and later on the early investigations of dopamine in the cat caudate nucleus. With his many contacts in the pharmaceutical industry, Costa was able to give us head starts on the pharmacological dissection of the receptor subtypes for the norepinephrine, dopamine, and acetylcholine responses. He taught me more pharmacology than I ever knew and mentored me throughout my career.

To connect back to the Catecholamine Hypothesis of Depression, we also investigated rabbits during the first 4 hours after treating them with large doses of reserpine, the idea being that if norepinephrine fibers were activated when we stimulated the LOT, those effects should be greatly diminished when the reserpine depleted the nerves of their norepinephrine content. The problem that arose in these experiments, as might be expected given the antihypertensive effects of reserpine, was that the anesthetized rabbits would go into shock about 2–3 hours into the reserpine treatment period. Tired of losing whole days of work, I devised a means to harvest the blood from the just expired rabbit, anticoagulate it, and then use that blood to keep the next rabbit alive long enough to test for the loss of the norepinephrine effect, and that we did see.

While Costa was of great help in those rabbit olfactory bulb experiments, his interest then was in assessing what dopamine did. Although there had been an initial assumption that dopamine in the brain was present only as a precursor to norepinephrine, Costa pointed out that in the caudate nucleus of the cat, rat, and rabbit, there was a very high level of dopamine but virtually no norepinephrine. So we proceeded to study the effects of dopamine in the anesthetized cat caudate. We included acetylcholine in one of the iontophoresis barrels as well because the caudate was rich in the acetylcholine metabolizing enzyme, acetylcholinesterase, and by presumption acetylcholine was a strong candidate transmitter there. But nothing of value is ever easy.

To our chagrin, putting electrodes into the cat’s caudate detected very few spontaneously active neurons. Interpreting that neuronal quietude as potentially the result of the general anesthesia, we switched from ether to chloralose to barbiturates, all with the same result. As a last gasp, we implemented an unanesthetized preparation by using electro-cautery through the inferior colliculi to isolate the forebrain, including the caudate and overlying cortex, from the brain stem, where the intact autonomic and respiratory systems could maintain the animal once the starting anesthetic wore off. Sure enough, when we attempted to record in these “cerveau isolé” preparations, there was much better spontaneous activity in the caudate.

These neurons were often excited by acetylcholine and depressed by dopamine (and by norepinephrine, but we assumed the two catecholamines were similar enough that the same receptors could recognize both). One short burst of dopamine could extend for many minutes the excitatory effects of acetylcholine. The paper we wrote emphasized that when we gave the decerebrate cats general anesthetics, the acetylcholine effect would go from excitatory to inhibitory. Of greater interest in retrospect is that implementing the decerebration almost certainly severed the ascending dopamine fibers innervating the caudate, thereby releasing them from the dopamine afferent effects. This paper for the Journal of Pharmacology and Experimental Therapeutics gave me a good qualifying start for eventual membership in the Pharmacology Society, my first professional society.

This last burst of productivity greatly elevated my interests in single-cell neuropharmacology, and the review I wrote for Science with Salmoiraghi, and the review article that Salmoiraghi, Costa, and I were invited to do for the Annual Reviews of Pharmacology made me start to wonder whether I really wanted to go back to patient care or take another path forward. Reluctantly, I returned to St. Louis and told Dr. Moore I had decided not to continue with my residency training. He asked with some consternation what I intended to do instead, and I said I wanted to work out chemical methods to visualize synapses containing norepinephrine so I could be certain that I was aiming the 5-barrel micropipets at the right target neurons. Although I suspect he was skeptical that I could accomplish that, he wished me well and often wrote me to comment on the papers I wrote.

In the final weeks I spent at St. Elizabeths, I applied for a special fellowship to undertake training in electron microscopy and histochemistry with Professor Russell Barrnett at Yale. Since it was too late to start a new series of experiments at St. Elizabeths, I decided to see if I could learn some of the rudimentary methods of electron microscopy by becoming a guest worker in the NIH Campus laboratory of Professor Keith Richardson, head of the Section on Neurocytology. He agreed I could come over, and he walked me through the details of brain perfusion fixation, dissection for electron microscopy, orientation of the tissue blocks for embedding in epoxy plastics, and how to make glass knives from whole sheets of glass in order to do ultramicrotomy to acquire the less than 1000 Angstrom thick sections that could be placed on copper grids and examined in the electron microscope.

Richardson had been the head research assistant in the neurocytology laboratories at University College London before coming to the NIH. Because he was one of the few Section heads who didn’t have a doctoral degree, he called himself “Professor Richardson” in the NIH Directory. (Julius Axelrod was another until he got his degree a few years before his Nobel Prize). These weeks of training were quite enjoyable, and they showed me a major strategic advantage that neurocytology provided over physiology: In physiological experiments, the investigator was obliged to stay with the animal until enough valid data had been obtained to warrant the nonrecovery surgery of early neurophysiology. But in neurocytology, once you had your material to examine, you could turn off the microscope and nothing was lost; the investigator could come back hours or days later and restart the analysis as though nothing had ever intervened.

In addition to teaching me the fundamentals of electron microscopy, Richardson had been one of the first people to examine tissues of the peripheral autonomic nervous system. He had observed that immersion fixation with a mixture of osmium tetroxide and potassium dichromate produced sympathetic nerve fibers containing synaptic vesicles with dense granular cores, rather than the electron lucent synaptic vesicles that epitomized the nerve terminals at the neuro-muscular junction where acetylcholine was the recognized neurotransmitter. Then just before I left NIH for Yale, Richardson published a report in Science with Julius Axelrod and Lincoln Potter showing a second method for detecting norepinephrine by ultrastructural autoradiography of nerve terminals in the pineal exposed to ³H-norepinephrine; there the sympathetic nerves actively transported the norepinephrine into the nerve terminals, where it was stored in the synaptic vesicles. I was eager to test these approaches in the brain.

The Yale Experience (1964–1968)

My 4 years at Yale were another highly enjoyable period of learning, productive research, and growing confidence on what rigorous investigation could reveal, especially when the protocol seemed to have been followed exactly as planned but the results came out quite different than had been anticipated going in. I had been attracted to Professor Russell Barrnett in the Yale Department of Anatomy because of his finding that glutaraldehyde could provide an alternative fixative to the typically employed “formalin,” with better structural preservation and retention of enzymatic activity suitable for performing enzyme histochemistry on the fixed tissues. Tissue fixation generally had been considered the result of protein denaturation through exposure to alcohols, ethanol, or methanol. Formalin was a mixture of formaldehyde and methanol. By dissolving formaldehyde powder in heated buffers, one could obtain nearly pure formaldehyde solutions that were an excellent fixative that formed carbon-carbon bonds across proteins, but some enzymes such as acetylcholinesterase were badly affected. Glutaraldehyde and an even longer dialdehyde, hydroxyadipaldehyde, retained intracellular structural details and also preserved enzymatic activity by linking across broader domains of the enzyme proteins. Then after the first fixation, and after the enzymatic histochemical reaction had been run, the tissues could be secondarily “postfixed” with osmium and appeared in the electron microscope just like the same tissue would have if fixed only in osmium.

Working with Russ, as he was known to all trainees, students, and fellow faculty, I was introduced to a very creative environment. We decided to pursue two goals in parallel: I would use glutaraldehyde as a prefixative to localize acetylcholinesterase in the brain, starting by working out the proper fixation and incubation details with the eel electroplax, and in the second series of work, I would use glutaraldehyde as a prefixative and try to replicate Keith Richardson’s studies on autonomic nerve endings detected by dichromate and osmium. If either or both lines were successful, we could then carry that protocol to the brain. The eel electroplax tissue was kindly provided by the laboratory of Professor David Nachmansohn at Columbia University College of Physicians and Surgeons, but watching the lab technicians harvest the tissue was a bit “shocking,” and not just because these were electric fish. The tech would reach into the tank, lay the eels (some of which were 5 feet long originally), cut off a 4- or 5-inch long segment, hand it to me to dissect and immerse in the jars of glutaraldehyde I had brought up with me on the New Haven railroad, and then cauterize the blood vessels on the eel’s side with a soldering iron, before throwing the eel back into the holding tank.

Both of my initial projects succeeded on the trial tissues, and I got my first publication in the Journal of Cell Biology on the EM localization of acetylcholinesterase in the electroplax. My studies of the vas deferens, in which the reaction product of the small granular vesicles seen after glutaraldehyde-dichromate fixation was absent if the animal had been treated with drugs to block synthesis or storage of norepinephrine, became my first Nature paper.

That same year, I was invited by Seymour Kety to participate in a 2-day meeting at the Neuroscience Research Program (NRP) in Brookline, Massachusetts, that would examine the evidence for biogenic amines as neurotransmitters in the central nervous system. There I met for the first time, the principal founder of the NRP, Francis O. Schmitt, with whom I developed an immediate rapport. We both worked in electron microscopy, although he was a pioneer developer of the device, and we both had ties to Washington University in St. Louis, where he had been a graduate student in physiology and later a faculty member, before becoming the first Professor of Biology at MIT. Also participating in this meeting was Kjell Fuxe, representing the Hillarp-Falck-Carlsson laboratories at the Karolinska Institute and Lund University, the foremost practitioners of the freeze-dry formaldehyde-induced fluorescence method. This group had begun to map all three monoamine systems (norepinephrine, dopamine, and serotonin) in the rat brain. At the beginning of their studies, their data were regarded skeptically by the classical neuroanatomists because none of the pathways they described had ever been seen by the traditional silver stain or postlesion degeneration metal stains on which most detailed circuitry in the brain had been based. This meeting was an outstanding event for me because I was able to meet and develop relationships with many of the leading scientists in the field of synaptic transmission and assess my competition up close.

In my second year at Yale, George Aghajanian, a graduate of the Yale Psychiatry residency program, returned from his military service at the Edgewood Arsenal and joined me in the quest to see the norepinephrine synapses in brain. George had close ties to Daniel X. Freedman, a Professor of Psychiatry, and I was invited to join them whenever Danny was in town to discuss recent papers in the brain research literature that might be relevant to psychiatry.

As I was now nearing the end of my NIMH Special Fellowship, I had to decide what to do and where to go next. Because of Russ and Danny, in 1966 I was invited to join the Yale Faculty as an Assistant Professor appointed jointly in Anatomy, Psychiatry, and Pharmacology, where one of Danny’s close collaborators, Nicholas Giarman was the senior figure in Neuropharmacology.

I learned a great deal from all three of these gentlemen and their Departments. From Russell, I learned that teaching histology, while readily accomplishable, was not something I found rewarding. As the new appointee, even though I was on a Research Career Development Award that was supposed to give me 90% of my time for research, I was assigned the parts of the histology course no one else wanted. I found it took me 6 or 7 hours to prepare my lectures and slides for every hour I was assigned to teach, and this made it very hard to get to my research program.

Fortunately, Russ traveled a lot and to keep his lab assistant Carolyn Lee occupied, he lent her to me. Because she had trouble reading my handwriting, I was given one of my best discoveries in the Yale years. Searching for reagents that might selectively label catecholamines, I had devised a protocol to try ethanolic phosphotungstic acid, a reagent that had been used to emphasize synaptic specializations with osmium fixation. Carolyn followed my protocol precisely, but when I thin sectioned the blocks and put them in the microscope, all I saw were the pre- and postsynaptic specializations, because I had neglected to say “and then postfix with osmium.” George Aghajanian and I used this “E-PTA” method to follow the development of synapses in the cerebral cortex and showed that hypothyroidism could slow that rate. Carolyn later went to medical school and entered private practice in Cleveland.

From Nick, I learned not only how to create a happy lab group, but how to build a group. The Chairman of Pharmacology at Yale was Arnold Welch, and the department he built was composed of faculty members who had been his or other senior faculty members postdoctoral fellows. Nick’s lab was built the same way, with the better graduate students staying to be postdocs, and the better postdocs being invited to join the faculty as junior members. I generally followed a similar course in recruitment and hiring and learned the hard way that when I didn’t do it that way, the results were suboptimal. For Nick’s introductory course to first year pharmacology graduate students at Yale, he enlisted two of the other Yale Pharmacology faculty, Jack Cooper and Bob Roth, and me to give a few of the lectures. When he died tragically in the aftermath of a terrible automobile accident, Jack, Bob, and I took our lecture notes to write, and dedicate to Nick, the first edition of the Cooper, Bloom, and Roth irreverent paperback text The Biochemical Basis of Neuropharmacology, which has lasted through eight editions at Oxford University Press and has reemerged as Introduction to Neuropsychopharmacology with Les and Sue Iversen as co-authors.

From Danny, I learned a great deal of people assessing and managing, as well as an unfailing love of learning and life. I served on my first Study Section with Dan as the Chairman, who kept the discussions focused on the science and not the applicant, and who would tolerate no commentary that was irrelevant to the evaluation of the proposal. In my third year at Yale, Danny agreed to become the Chairman of the Department of Psychiatry at the University of Chicago and within a year had offered both George and I appointments. Traveling to Chicago and seeing where we would have been obliged to live, I knew I could not commit my wife and two young children to the South Side Kenwood area, despite the progressive school at the University they could have attended. After a suitable and respectful period of deliberation, both George and I opted to stay in New Haven. Thanks to Danny, the Yale Psychiatry Department was awarded a training grant in the biological sciences, and George and I were hired to do the teaching of the residents, an opportunity that connected me with David Kupfer when he was a resident, and with his mentor Tom Detre, before they left to reinvigorate Psychiatry at the University of Pittsburgh. But Danny remained a friend and mentor for his next 30 years, and he was my best man when I married Jody Corey in 1980.

Nevertheless, the offer from Dan had served to awaken my thoughts as to what I really wanted to do and where I wanted to do it. With my Career Development Award I had 5 years of assured funding that I could take with me, and the pressures of teaching were still impeding the time I could devote to research. The one medical student who chose to do a thesis project with me, Stuart Schorr, helped me broaden my knowledge of the histology of the pancreas by detecting autonomic nerves to the islets that were not described in our textbooks. Stuart went into the practice of pediatrics in Seattle. I found that kind of bench-side teaching much more to my liking as it also allowed me to see research progress at the same time. After declining an opportunity at Case Western Reserve, I was still uncertain where my future lay.

However, the collaborations with George Aghajanian were highly successful. For one of our early projects, we decided we should try to use the method of Potter, Axelrod, and Richardson, namely EM-Autoradiography of terminals that accumulated ³H-norepinephrine. Undoubtedly we were stimulated by a lecture at Yale by Jacques Glowinski, a postdoctoral fellow in Axelrod’s lab who with Les Iversen had characterized the uptake, distribution, and metabolism of the catecholamines after intraventricular injection. Les described many of my collaborations with him in Volume 6 of this autobiographical series, and the three of us have remained close friends for the past half century.

While George and I figured we could work out the intraventricular injection part, neither of us had ever done EM-autoradiography. A search of the literature identified Professor Beatrix Kopriwa at McGill University, and I wrote her to ask if I might visit for 2 or 3 days to learn the method. She agreed, but she noted that it was a complex and lengthy procedure that might take a bit longer to learn. She was correct, of course, but I figured after watching her for 3 days that it would still take trial and error in my lab to get it right. So George and I plunged ahead and developed autoradiographs of thick sections a week after making our first intraventricular injections. We selected the paraventricular nucleus of the hypothalamus as it was close to the third ventricle and, as I knew from my early work at St. Elizabeths, it was known to be rich in norepinephrine. The light microscopy of thick sections developed for autoradiography after a couple of weeks showed that the neuropil of the paraventricular nucleus was studded with grains. Two months later we developed the thin-section autoradiographs and successfully transferred onto EM grids the thin celloidin membranes bearing the thin sections coated with the now-developed emulsion. To verify that the grains we saw over nerve terminals were selectively localized, we did stereological comparisons of the area occupied by all nerve terminals, and the area occupied by nerve terminals with large granular vesicles, with the area occupied by dendrites, glia, and blood vessels. More than 90% of the grains were over the large dense vesicle nerve terminals, which was less than 5% of the area we surveyed.

Highly pleased, we wrote our paper to submit to Science, where the Potter, Axelrod, and Richardson paper had been, and decided to leave the manuscript alone for the weekend and then submit it after we read it cold again on Monday. We left it on the corner of my desk. But when we came in on Monday morning, the paper was gone. Horrified, we concluded that maybe it had been knocked off the desk and into the trash by the janitor, and we spent several hours opening the collected trash baskets and finally found our paper and the envelope ready to send off. It was accepted.

George and I were then invited to develop a joint laboratory in the newly completed Connecticut Mental Health Center that had been built on the north edge of the medical school campus on land purchased for the project by the State of Connecticut. We went to the FASEB meetings in Atlantic City that spring looking to buy the equipment we would need, including an electron microscope. Prowling the halls of the Exhibits, we came to the Karl Zeiss exhibit and their new model, the EM-9. Mr. Rudolph Partsch, who identified himself as the Director of Microscope Development, offered to show us what it could do—quite a feat since most electron microscopes were housed in completely darkened rooms, and here we were in the bright lights of the Exhibit Hall. As he completed his demo, he asked us if we were now prepared to make a purchase, and at exactly that moment, the public address system announced that the Exhibit Hall would be closing for the day in 15 minutes. We responded to Mr. Partsch that if he could disassemble the microscope, insert a fresh filament, and get the electron beam aligned to the screen before the Hall closed, we would seriously consider it. He did. Six months later we had our Zeiss microscope in our new labs.

In the spring of 1968, I was contacted by my old boss, Nino Salmoiraghi, to see if I might be interested in returning to St. Elizabeths. He informed me that the Director of the National Institute of Mental Health, Stanley Yolles, was forming a new administrative unit to be called the National Institutes of Mental Health, soon to be joined by the National Institute of Drug Abuse, and the National Institute of Alcoholism and Alcohol Abuse, and that our former Clinical Neuropharmacology Research Center was now the Division of Special Mental Health Research, within which would be the Laboratory of Neuropharmacology. He suggested I could form a Section for which I proposed the title Cytochemical Neuropharmacology, and of course the benefits of Intramural Program budget support at a level far above what I could ever have hoped for on my grants. Furthermore, there would be 26 vacant positions that I could fill as I saw fit. He also implied that since he would be very busy as Division Director, that I would for all practical purposes be directing the Laboratory of Neuropharmacology. Lastly, he played a trump card in stating he was pretty certain that Erminio Costa, our former collaborator, would be joining the division to create the Laboratory of Preclinical Psychopharmacology. It took me a very brief time to recognize that this was an undeniable invitation, and I accepted.

In an effort to keep me at Yale, Russell and Nick nominated me for promotion to Associate Professor, to which I responded somewhat curtly that if they really wanted me to stay they should make me a postdoctoral fellow again. It was momentarily attractive because Yale had hired Paul Greengard to the Pharmacology Department, and his work on the roles that cyclic adenosine monophosphate might be playing in synaptic signaling was becoming very interesting. The promotion did come through in the last month I spent at Yale, but I was committed to new horizons with a return to St. Elizabeths Hospital.

St. Elizabeths Again (1968–1975)

A number of disturbing events happened in the spring and early summer of 1968—the Tet offensive in Viet Nam led to Lyndon Johnson declaring that we couldn’t afford both guns and butter and that he was eliminating all vacant government positions effective July 1. That posed a serious problem for the three young women I had hired in New Haven to be research technicians in the new labs in DC. I found these women through Mildred Gordon, a mid-40s graduate student in Russ’s labs, who taught Biology at the Connecticut College for Women (now Connecticut College), one of the “little Ivies,” when I asked her if any of her graduating biology seniors might want a job in Washington. Three came for interviews, and I hired all three. When Johnson decided to cancel all vacant positions, they were able to get to Washington to sign in before the end of June, so I only lost 23 vacancies. One of those three, Elena Fasano Crawford, still works with me, and she has been a co-author and technical guidance guru for every one of my fellows and visitors for the past four decades.

Then in April, on one of my visits to assess the lab remodeling, Washington, DC underwent rioting following the assassination of Martin Luther King Jr., and still more civil unrest after the assassination of Robert Kennedy in June. Since the laboratories at St. Elizabeths were located in southwest Washington, DC, just across the Potomac River from National Airport, there was no chance that anyone I would hire would choose to live anywhere near there. We were also told to expect to be at St. Elizabeths for no more than 2 or 3 years, because there would be a new campus for the National Institutes of Mental Health in Colombia, Maryland, a new community being developed half way between DC and Baltimore on the far northeast side of DC. The advice on where to pick a home was to go to Montgomery County, the upscale community that included the NIH and Naval Medical Center, as it would be a much shorter drive. My choice was to reside in Rockville, close to the Capitol Beltway and the NIH Campus. The Colombia Campus was never built.

When I arrived in my new laboratories and office, things were much more conveniently arranged than when I had worked at St. Elizabeths the first time. Then the labs were in the basement, and the offices were on the fifth floor. Now my office and those of the staff and fellows were all together on the first floor, and our new and old labs nearly adjacent as well as in the basement. I was now responsible for three permanent staff members who had been hired by Salmoiraghi: Forrest W. Weight, who had taken my Research Associate slot when I departed for Yale and then spent 2 years in Sweden learning intracellular recording in the cat spinal cord; and two invertebrate neurophysiologists, Anthony Gorman and Maurizio Mirolli. Had I been able to use the 23 positions that were a part of my invitation agreement, the two invertebrate neurophysiology groups would have been tolerable. Now, however, they looked to me much like resources that needed redirection, and I made clear to them that their present budgets were as much as they would ever be.

Fortunately, I did have six postdoctoral colleagues, three of whom were ready for their second and final years: John Connor who had been studying the caudate nucleus and went on to become a Professor of Physiology at Penn State University, Jim Couch who did the first iontophoretic investigation of the serotonin neurons of the raphe nuclei and went on to become the Chairman of Neurology at the University of Oklahoma School of Medicine, and John Crayton who had been doing electron microscopy with Dr. Mirolli but who was eager to learn some electrophysiology. John went on to a residency in Psychiatry with Daniel Freedman in Chicago, but for his last year in St. Elizabeths he collaborated with one of the new fellows, Roger Nicoll, who had worked at St. Elizabeths with Salmoiraghi as a medical student from the University of Rochester on the rabbit olfactory bulb after I left. Returning now after getting his M.D. degree, Roger wanted a new preparation and so he and John Crayton started anew on the paraventricular nucleus of the hypothalamus, using my old para-esophageal exposure, and another first year fellow, Jeffrey Barker, came over from the Neurological Institute to join them. Roger has had a spectacular career and is now a member of the National Academy of Sciences at UC San Francisco, a leader in the field of long-term potentiation and its pertinent synaptic plasticity, and has been awarded the 2010 Neuroscience Prize of the National Academy of Sciences. Jeffrey stayed at NIH, eventually becoming Chief of the NINDS Laboratory of Neurophysiology.

In addition to those good people, the two with whom I worked the most closely for the next several years were Barry Hoffer and George Siggins. Barry had been at St. Elizabeths as a medical student from the University of Rochester during my second summer at St. Elizabeths and began to learn some of the methods of microiontophoresis research. After completing his M.D. and Ph.D. degree work in Rochester, Barry was ready to come back. Joining us was George Siggins, the last new fellow selected by Salmoiraghi before moving to his new position. Siggins had done a Ph.D. at Boston University in pharmacology, and was especially skilled with fine control of his fingers, no doubt a byproduct of his highly practiced musical talent on a variety of stringed instruments. When I knew I would be coming back to St. Elizabeths, and that Barry would be one of my new Fellows, I wrote to him proposing we look for the target of the norepinephrine innervation of the cerebellar cortex, the brain region he had studied for his thesis, and perhaps in that era, the best understood cellular system in the brain. Siggins, after meeting Barry, opted to join with us.

Not knowing where the norepinephrine fibers to the cerebellum would make their synapses, our initial studies were focused on seeing what norepinephrine would do to neurons whose identity could be determined through their discharge patterns. The most pertinent neuron was the Purkinje cell, the main efferent neuron of the cerebellar cortex that fired in rapid (∼ 60Hz) single spikes occasionally interrupted by a complex spike caused by discharge of the climbing fiber to each Purkinje cell. Using a method that Barry and his Rochester colleague Don Woodward developed, measuring the interval between spikes instead of the overall average rate of firing, we were surprised to see that what norepinephrine did was to increase the number of interspike intervals longer than 125 msec but without affecting the response to the climbing fiber or the median single spike discharge pattern.

While Barry and George were busy testing the neurons of the cerebellar cortex, I was trying to bring the tricks I had learned at Yale to bear on determining the synaptic target in cerebellum for the norepinephrine fibers. Doing freeze-dry formaldehyde-induced fluorescence histochemistry in Washington, DC, in the hot humid summer was hopeless, and we needed to know sooner than that. The autoradiographs of sites of ³H-norepinephrine accumulation seemed to target Purkinje cell apical dendrites, so we proceeded under that assumption, aided by a new tool that allowed for somewhat more immediate feedback—localization of degenerating terminals 8 hours or 1 week after intracisternal injection of the selective noradrenergic neurotoxin, 6-hydroxy-dopamine. Within a few months, the Purkinje cell was confirmed as the norepinephrine target cell by all three approaches.

Barry and Siggins went on to characterize the effects of norepinephrine on these neurons, observing that the effects of iontophoretic norepinephrine could be blocked with a beta-receptor antagonist. This led them immediately to evaluate whether the effects of norepinephrine could be mediated by cyclic adenosine monophosphate (cAMP), a process being intensively investigated throughout the NIH, including in the labs of our neighbors in the Costa lab. With their pharmacological support, we observed that cAMP replicated the effects of norepinephrine, and that the effects of norepinephrine were prolonged by drugs that inhibited the enzyme phosphodiesterase that catabolized cAMP. We published these observations in a series of papers in Science, and then in 1971, in three back-to-back comprehensive papers in Brain Research to confirm the anatomy, physiology, and pharmacology of the adrenergic innervation of the cerebellar cortex. That summer we presented these data at the International Physiology Congress and at a satellite meeting in Basel organized by Leo Hösli. I had a 15-minute presentation that, with questions from John Eccles and his wife, went on for over an hour before Dom Purpura who was chairing called a break. During the break, Bill Douglas, a Professor of Pharmacology I knew at Yale, suggested that I ask Eccles if he wasn’t the same person who once held that synapses were all electrical.

This was a propitious time to have convergent evidence for the function of specific brain circuits, for 1971 was the inaugural year for the Society for Neuroscience. I served on the Program Committee for that first meeting in Washington, DC, and then as Assistant Program Committee Chairman for the second meeting in Houston that a few less people attended, causing concern that perhaps such an endeavor was premature. However, by 1973, when the third meeting was held in San Diego, the President, Walle Nauta, instructed me as Program Committee Chair to apologize to the audience at the Presidential Symposium for the lack of space in the presentation rooms—The Society had rapidly grown to exceed the capacity of the San Diego Town and Country Convention Center. At any rate, without further interruption of the career narrative, the Society continued to grow at an average annual rate of around 7% for more than three decades.

To resume our progress path, the next two major advances came through friends. At Washington University, Dr. Charles Parker and one of his Fellows, Jim Wedner, a former Barnes medical resident, had developed an immunoassay for cAMP. I asked Jim whether he might come to Washington and see if we could develop an immunohistochemical assay to detect cAMP formation and binding, and it worked to our amazement. With George and Barry we then worked out a means to do this in living animals, taking frozen biopsies of the exposed cerebellum before and after activation of the noradrenergic afferents.

That step worked too, but it benefited from what I had learned on a quick visit to Kjell Fuxe, Tomas Hökfelt, and Lars Olsen at the Karolinska Institute. This visit was immediately after my microsabbatical with Les Iversen when we localized GABA uptake sites, and the announcement that Axelrod and von Euler had won the Nobel Prize along with Bernard Katz. Our very happy Swedish colleagues told me that they had been able to trace the origin of the noradrenergic nerve fibers to the cerebellum, the hippocampal formation, and cerebral cortex to a nucleus in the pons named the locus coeruleus. It had that name because in primates the neurons in this nucleus exhibit a blue pigment. I immediately faxed that information back to Barry and George, and when I returned they asked, “Where’s that?” We found it, and stimulated it, and reproduced the effects we had observed for iontophoretic norepinephrine.

In achieving relatively long duration intracellular recordings from Purkinje cells before, during, and after stimulation of the locus coeruleus, Siggins confirmed what we had seen with intracellular recordings and iontophoretic administration of norepinephrine: The neuron hyperpolarized, but the membrane resistance increased, as did the size of the climbing fiber postsynaptic potential. This was a most unusual combination of results, and we hypothesized that the intracellular mediation of the norepinephrine effect by cAMP led to modification of active ion channels, subsequently known as the “Hyperpolarizing Cyclic Nucleotide” effect.

At this point, the question uppermost in my mind was to determine when the neurons of the locus coeruleus would discharge in an awake behaving animal. The choice at that time was still the cat, given their tolerance for neurosurgical procedure, and their very thick skulls permitting movable microelectrode assemblies to be mounted and supported. We tried this with two fellows, Nai-Shin Chu who recorded cat locus coeruleus neurons in unrestrained awake cats, and Yung-Shi Sheu, who did the same experiment recording from raphe neurons. However, because the neurochemistry of these nuclei was heterogeneous, unlike the case in rat, monkey, or human, these results were difficult to interpret.

Meanwhile, Jean Lauder used the autoradiographic thymidine birthdating method she had employed for her thesis at Purdue to define the moments during gestation when the locus coeruleus and other monoamine neurons underwent their final cell division relative to the neurons we had begun to define as their synaptic targets. Virginia Pickel, Story Landis, and Menahem Segal performed a series of experiments to confirm the efferent trajectories of the locus coeruleus with orthograde and retrograde tracer methods. Virginia and Menahem did a heroic experiment, defining by selective transection the cerebellar peduncle through which the norepinephrine fibers entered the cerebellum, and then showing that partial transection of one superior cerebellar peduncle not only activated axonal sprouting of norepinephrine within the cerebellar cortex, it also stimulated similarly intense sprouting within the hippocampal formation. Virginia went on to become the leading U.S. practitioner of electron microscopic immunohistochemistry, identifying with different-sized gold particles two or three antigens in a given field of view.

Menahem did a series of experiments on the hippocampus and the interactions with the locus coeruleus that replicated what we had found in cerebellum, and then examined the interactions in awake behaving rats, similar to the work he had done with Jim Olds at CalTech for his Ph.D. thesis. Menahem’s crowning observation to me was that the stimulation of the locus coeruleus could amplify whatever synaptic messages were operating on the hippocampal neurons: If an environmental signal was inhibiting, then that signal with locus stimulation enhanced the inhibition. If the signal were paired with food and the hippocampal neuron accelerated, signaling food with locus stimulation enhanced the activation. If the signal came to be meaningless through extinction, the locus coeruleus stimulation did not change the firing. These studies and the results we observed on membrane properties during the actions of norepinephrine or the locus were then confirmed in studies that Barry did with Don Woodward, showing again that either excitation or inhibition could be enhanced by the locus. They termed this effect “neuromodulation.” I preferred to call it “enabling,” which sounded to me like a more precise description of this contextual enhancing effect.

When Steve Foote joined the lab from his thesis studies with Hans-Lukas Teuber at MIT, and lent his expertise in training and recording from awake behaving monkeys, he observed even greater complexity in the norepinephrine response effect. His observations were based on the spontaneous activity of neurons in the auditory cortex before and after responding to the playing of a natural squirrel monkey vocalization; here, norepinephrine reduced the background activity and enhanced the vocalization response, thereby increasing the signal to noise ratio of the acoustic response. Menahem rapidly rose through the ranks at The Weizmann Institute and has been a leading neuroscientist there. Steve remained with us throughout the years at St. Elizabeths and joined us when we moved west, which I shall describe in the next section. Working with Steve on a part of this project, and also with Barry, was Bob Freedman. After his time with us, Bob completed a psychiatric residency with Daniel Freedman at the University of Chicago and then established himself at the University of Colorado, where he has been Chairman of Psychiatry and is the current Editor-in-Chief of the American Journal of Psychiatry.

When our colleagues in Sweden reported an even better method for visualizing norepinephrine and dopamine, using glyoxylic acid instead of the freeze-dried formaldehyde procedure that was so problematic in Washington, Elena Crawford and I refined the approach to work with cryostat sections, which were far easier to control than the vibratome sectioning procedure used by the Swedes. Story Landis, then finishing her Harvard Ph.D. thesis with us, applied the norepinephrine localizing methods to her cerebellar mutant mice, confirming anatomically and electrophysiologically with George Siggins and Steve Henriksen that the NE fibers and responses followed the Purkinje neurons, wherever they came to lie in the cerebellar cortex. Her subsequent career has also been distinguished, becoming the chairperson of the Department of Neurobiology at Case Western Reserve, and now the Director of the National Institute for Neurological Disease and Stroke. Bob Robinson came to us in the middle of his psychiatry residency at Johns Hopkins, specifically to work on two problems that he had observed in his patients: the weight gain after treatment with antipsychotics, and the inappropriate euphoria he observed after certain frontal right-sided cerebral infarctions. The rats were not a good subject for the former question, but he has pursued the latter subject for most of his career, serving as well as Chairman of Psychiatry at the University of Iowa.

Having already noted why I wear bow ties, some readers may be interested in why I have a mustache. When my daughter celebrated her ninth birthday, her wish was for a roller skating party, and I reserved the Gaithersburg Roller Skating rink for her and nine of her friends. After we had arrived and the girls were on the rink, the manager asked if I wouldn’t like to have a pair of skates to join them. Knowing my inner klutziness, I declined, but the manager persisted, saying that since I had rented the whole rink for the day, my skates would be on the house. I said, “If I try to skate, I’m going to break a leg.” The manager said, “Nonsense.” So I put on a pair of roller skates and tried the rink. Not more than 10 steps later, I felt myself falling and threw my right foot out to try to regain balance. As I did, I heard a sound like a thin pencil breaking, and I knew I had broken my leg at the ankle. I did a very good job of that, fracturing the tibia, the fibula, and the calcaneous bones, for which the orthopedic surgeon put me in a long leg cast for 6 months and warned me I might never be able to walk without a limp. I recovered fully but, while my leg was in the cast, I grew the mustache so I could see something growing. I later completed three Honolulu marathons without a limp, and the mustache has become one of my biomarkers.

Two other achievements during the St. Elizabeths period merit inclusion, both derived from Neuroscience Research Program (NRP) meetings that I attended. Les Iversen and I organized a meeting on “Neuropeptides and Amino Acids as Neurotransmitters.” The participants included Susan Leeman who had just reported that Substance P, an inhibitory material found in acetone extracts of the gut by Ulf Von Euler in 1934 was actually a 12-amino acid peptide. Roger Guillemin attended and described the isolation of two hypothalamic releasing factors that when chemically characterized and replicated synthetically were also shown to be peptides, thyrotropin releasing hormone, and somatostatin, a 14–amino acid peptide that blocked the actions of growth hormone releasing factor and was interfering with its isolation. While most of the attendees were quite willing to consider that neuropeptides could be transmitters, there was much skepticism that amino acids such as glutamate or aspartate could so function because the argument went, how could a neuron segregate the amino acids it needed for protein synthesis from those it might reserve for synaptic signaling. Gammaamino butyrate (GABA) was considered an exception.

The meeting with Guillemin opened a new door. Shortly after that I was approached by Frederic de Hoffman, the President of The Salk Institute, who inquired whether I might consider moving our group and, if so, what would I estimate to be the cost of moving and establishing a new lab. I had been asked that question several times before, and my stock answer was at least $5 million. That usually ended the inquiries, but de Hoffman just paused briefly and said, “Let me get back to you on that.” A week later, he called me again and said he thought he might be able to do that, and if I would commit to coming he would get right to work on it.

The second NRP meeting of note was one organized by Sol Snyder of Johns Hopkins that brought together a highly competitive group of investigators who were attempting to isolate an endogenous brain factor that acted in bioassays as though it were a congener of morphine. While the evidence was quite impressive that such a factor existed, its chemical nature remained elusive. At the meeting Hans Kosterlitz and John Hughes stated that they knew what the factor was but because of its importance couldn’t tell us. A few weeks later, Avram Goldstein, a leading opiate researcher and the Dean of Molecular Pharmacology at Stanford University, invited me to give a summarizing discussion at the end of the First International Narcotics Research Club meeting, where the atmosphere was filled with intrigue on the nature of what all agreed would be called “endorphins” (endogenous morphine).

These peptides were really starting to attract my interest, and since we had answered most of our original questions on the circuits and functions of norepinephrine in the brain, I felt it was time to take a new direction. Salmoiraghi had resigned as Director of the Division in 1973 to become Commissioner of Mental Health Research for the State of New York, and I had been made Acting Division Director. That was acceptable for awhile, and I enjoyed hosting visiting dignitaries such as Roger Egeberg, the Assistant Secretary for Health in Nixon’s Department of Health, Education and Welfare, and Charles Edwards, the Commissioner of the Food and Drug Administration when they came to see our labs (see Fig. 1.2). But it was clear that if I remained the Acting Director, I would soon be made the Director. In November of 1975, I resigned my position at St. Elizabeths Hospital and, with my daughter and son, began our move west to The Salk Institute.

The Salk Institute (1975–1983)

After I committed to Dr. De Hoffman that I would come if he could raise the funds to build the new labs to my specifications and equip them, I had to study a whole new profession: lab architecture. Scientists rarely get to design the labs they will occupy because most often the person who designed the labs just left (or they wouldn’t be empty), and you are given the old space. At Salk we had the chance to really plan how we would use our 8000 square feet of empty space.

Fig. 1.2    The author as Acting Director, Division of Special Mental Health Research, National Institutes of Mental Health hosting Roger Egeberg (second from left) then Assistant Secretary for Health, and Charles Edwards (far right) then Commissioner of the Food and Drug Administration and soon to be Assistant Secretary for Health. Erminio Costa, Chief Laboratory for Preclinical Psychopharmacology is second from right.

In the months before we were to make the move, after I had assessed which lab members I would invite to come with me, The Salk Institute sent out the lab architect Donald Reeves to come up with some plans. Don stayed 3 or 4 days, carefully photographing the selected lab personnel doing their routines in our existing labs, and then went back to San Diego to create floor plans. When he came back to me, it was clear that while he got some things that needed to be adjacent to be efficient, other details of his plan were just not right. The biggest constraint is that we were budgeted for one PDP-11 computer, but we had hoped to have four labs undertaking electrophysiological recordings, and they all needed to be close enough to that computer to acquire and then analyze the data.

Don came back twice with plans that to me were still conventional and not quite as efficient as I thought they could be. After the last cycle, when I showed him what the remaining problems were, he threw up his hands in frustration and said, “I give up. What you need is a lab shaped like a Kodak Carousel.” To which I responded, “Let’s pursue that.” We sketched a computer center, with the electrophysiology rooms as pie-shaped wedges facing into the center. We placed the neurochemistry areas where they would have maximum illumination from the large windows, and the microscopy areas where they could be shielded from the light (see Fig. 1.3). There were only two problems. The first was a financial decision as to whether we would have another lab door or more memory for our computer. The lab doors at The Salk were specially casted stainless steel doors and hinges and in 1975 they were priced at $5000 a door. I opted for the memory, which cost the same then for 8 kilobytes of random access memory.

The second problem was that having such an unconventionally configured space broke one of the spatial principles that Jonas Salk had worked out with his architect Louis Kahn: that the labs should be very flexible and nothing should be regarded as permanent. For that reason, every lab floor had an interstitial floor above and below, so that any new requirement for gas, vacuum, water, or special plumbing could be installed at any location in any lab anytime. Before de Hoffman was willing to submit the “carousel” plans to a construction estimate, it would be necessary for me to get Jonas’s approval. I had started off with a very warm relationship with Jonas, and he had taken the time to interview me before I was invited to join the faculty, so I felt his evaluation of our proposed plans would be given an objective evaluation. I laid out the plans on the table in the conference room next to his office and showed him why this was ideal for the various parts of the lab I wanted to create. He stared at the plans silently for a considerable time and then looked up and said, “That Louis Kahn, such a genius. His plans allow for anything.” Construction proceeded.

The labs were to be constructed next door to Roger Guillemin’s lab, on the ground floor of the south building at Salk. When I went to visit the space after the final plans had been approved, Reeves and his assistant Dean Amantea had chalked out on the floor the placement of the walls for the offices, the central computer, the pie-shaped electrophysiology labs, and all the other rooms; when I entered they were playing the music from Stanley Kubrick’s movie 2001: A Space Odyssey, and they told me our labs-to-be bore a strong similarity to level 5 of the Starship Enterprise. That became a kind of underlying theme for the new labs, formally named the Arthur Vining Davis Center for Behavioral Neurobiology, to recognize the support of the Arthur Vining Davis Foundation in its construction. In fact, we named our weekly journal and scientific progress meetings “STARTREC” that stood for Special Thursday AM Training, Research, and Education Conferences.

Fig. 1.3    Room layout of the Arthur Vining Davis Center for Behavioral Neurobiology, the author’s laboratories at The Salk Institute, 1976–1983. The central computer core is labeled with an asterisk. The author’s office was in the lower left corner.

Every faculty member and every trainee was required to make presentations of what they were doing and, if they weren’t yet in possession of data to present, they had to present a paper from the literature. They were video taped both in making their presentations and as members of the audience asking questions of the speakers. Those tapes were often the subject of the STARTREC meetings as well, to improve how to deliver a scientific presentation and how to behave as members of the audience.

The science in the new labs was also both an extension of what we had been doing at St. Elizabeths Hospital and new endeavors. Realizing we had to get substantial grant support before our starting dowry was consumed, I spent most of my days trying to determine what we could do to be competitive. A first focus was to investigate comprehensively the effects of lithium treatment on the functions of the locus coeruleus and its efferents, feeding the animals with Li-containing food pellets (Bill Shoemaker had been trained in the Department of Nutrition at MIT) and for long periods of time, since the antimania effects took 2–3 weeks to be observed in patients. Lithium had the great advantage that it was not metabolized, and brain and blood levels were easily measured. The grant was funded after a site visit by big-time neuroscientists who came out to see what we had built.

When I had arrived at The Salk, and before my labs were ready, I began a collaboration with Roger Guillemin, who had by now gotten interested in the endogenous opioids. As I was driving from DC to California, the paper by Kosterlitz and Hughes appeared in Nature defining what they termed enkephalins as two pentapeptides, differing only in whether the C-terminal was a leucine or methionine. A friend of Guillemin’s at UC San Francisco’s Hormone Research Laboratory, C. H. Li, had been studying a pituitary peptide, β-lipotropin, and Guillemin creatively incubated this peptide with brain homogenates, isolated the proteolysis fragments, and, having identified them, synthesized them as pure materials. Whenever his colleague Nick Ling would synthesize one of these long endorphins, I would take them to the labs of a close friend at UC San Diego, David Segal, who graciously let me use his lab space, and we would test the peptides for behavioral effects after intracisternal injections following brief ether anesthesia. The astounding result was that the 31–amino acid fragment, β-endorphin, was extraordinarily potent, inducing hypothermia and a rigid catatonic posture for hours at what we thought were extremely low doses, an effect that was almost immediately reversed with naloxone, the classical opiate antagonist. With these observations, we had a Science paper before my new labs were ready to occupy.

To describe in any detail all of the exciting science we were able to explore at The Salk would take more space than this entire essay and, since all of those observations were promptly published, the results are all “out there.” But, given that the lithium grant had gone well, and that the opioid peptides seemed like the coming hot item, we used the exact same application and substituted opioid peptide for lithium, adding mapping and reward analysis as well. By this time, George Koob had joined us from his postdoctoral period with the Iversens, lending substance to the term “behavioral” in the Center’s name. F. O. Schmitt paid a visit to the delight of all (see Fig. 1.4).

Shortly after his visit, I was called by Ed Evarts who was then the immediate Past-President of the Society for Neuroscience, who wanted to know if I would agree to be nominated for President in the 1976 election cycle. I had been Secretary for 3 years by then and had declined to run when I had been invited to do so in 1975 because of the move west. This time I agreed, and a few months later, was told that I had been elected. For my Presidential Symposium at the 1977 annual meeting, I was able to get a grant from the Arthur Vining Davis Foundation to rent a television satellite ground station for the Public Broadcast TV channel in Anaheim, and I got permission from the NIH to use their National Library of Medicine television studio to do a bicoastal true satellite meeting with Julius Axelrod and Marshall Nirenberg in Bethesda, communicating interactively with the audience and the panel in Anaheim (see Fig. 1.5). We also had Tom Bryant, Chief of Staff to Mrs. Carter, President Carter’s wife, to report on the then ongoing President’s Commission on Mental Health. To me this was (and is) the best of scientific meetings, and it predicted a time when we may not need to travel, although we haven’t gotten there yet.

Fig. 1.4    Francis O. Schmitt visits the Davis Center founding staff in June 1978. Pictured left to right are as follows: (Back row) George F. Koob, Klaus Liebold, Nancy Callahan, Ed French, George Siggins, Steve Foote, Walter Zieglgänsberger, Bill Shoemaker, Joe Rogers, Leonard Koda, Steve Henriksen; (front row) Viveca Lindefors, Elena Crawford (then Battenberg), Dora Games, Raana Asad, Francis O. Schmitt, and the author.

Back to the scientific program, we also began to explore with George Koob the results obtained by workers in The Netherlands claiming that the subcutaneous injection of the posterior pituitary hormone vasopressin had the ability to enhance learning and memory. With Aaron Ettenberg, Derek van der Kooy, Michel LeMoal, and George, we found this claim to be a misinterpretation and showed that the learning effect could be blocked by antagonists that didn’t enter the brain. Later with Scott Deyo and Bill Shoemaker, we showed that the amounts that did enter the brain after subcutaneous injection were extremely small.

Fig. 1.5    Video image from the Presidential Symposium of the 1977 Society for Neuroscience meeting, from the Anaheim Convention Center. Pictured in front row (left to right): Max Cowan, Robert Doty, Masao Ito, and Francis O. Schmitt. Also visible James McGaugh (behind Doty), Robert Moore (behind Ito), and Michael Bennett (behind Moore).

While I was fascinated with these neuropeptides, Steve Foote began a series of arduous experiments attempting to record from the locus coeruleus of awake behaving monkeys. Our NSF grant application to fund this work was rejected with the assertion from the reviewer that “nothing useful will ever be learned by recording from the locus coeruleus!”. Steve also used orthograde and retrograde tracers to work out the efferent projections of the locus coeruleus with Sandra (Sandy) Loughlin. Other work on identifying norepinephrine in the hilus of the dentate gyrus was accomplished by Leonard Koda, and my first UC San Diego neuroscience graduate student, Jesse Shulman, who was also the stepson of Robert Galambos, a Professor of Neurosciences at UCSD. Jesse started a postdoctoral fellowship with Les Iversen but decided bench work may not be his calling. He then did broadcasting from the combat of the first Persian Gulf War for CBS radio and later became a consultant for biotech investing in London. Jean Rossier and Alejandro Bayon worked out many of the regional differences and neuroendocrinological specificities between the peptides of the pro-endorphin series, and those of the pro-enkephalin family. Jean has become a distinguished neuroscientist in France, but Alejandro and his family died tragically in a plane crash in Nepal.

Working with Jesse, Sandy, and with some of the other students and postdocs helped me generate my two most-often asked questions when we were reviewing data, and they almost always were greeted with a blank stare. The first was, “Now that you know that, what does it mean and what can you now do?” The second question was, “What is the thesis of your thesis?” Students almost never could come up with an overriding question that encompassed their body of work but rather generated a series of observations with limited connectivity. Part of my mentoring attitude was to get them to see where their smaller pieces of observation fit into a larger picture of our neuroscience.

The whole lab was transformed in 1977, when Ernest Noble, the Director of the National Institute of Alcoholism and Alcohol Abuse, came to visit and proposed that instead of an RO-1 on alcohol actions at the neuronal level, I apply for an Alcohol Research Center. This much larger grant would allow me to bring in collaborators from other parts of the Salk faculty such as Hyam Leffert, who had developed ways to grow pure hepatocytes in culture, and Helen Neville, a neuropsychologist interested in cortical plasticity. When the Center was funded, we applied for a Training Grant, and with that we could hire six postdoctoral fellows a year, further expanding the range of experiments we could pursue. Almost all of them turned out to be rich veins of discovery.

The group of fellows we had in 1980 were particularly noteworthy for their zeal and subsequent productivity. The group included Joseph Rogers, now Director of Research for the Sun City Research Foundation; Pierre Magistretti, Director of the Brain Mind Institute at Ecole Polytechnique Federale in Lausanne and a former President of the Federation of European Neuroscience Societies; and John Morrison, formerly the Chairman of the Department of Neuroscience and now Dean of Basic Sciences and the Graduate School of Biological Sciences at Mount Sinai School of Medicine. Their studies on the localization of neuropeptide fibers in aging and Alzheimer brains gave us our first opportunity to apply our methods to human brains, and Pierre’s work with John exposed the intersections between norepinephrine fibers and those containing Vasoactive Intestinal Polypeptide. Pierre also showed that VIP and norepinephrine could both activate cAMP synthesis, another hint at an enabling mechanism. Pierre’s work for his thesis at UC San Diego set the stage for his career-long pursuit of astrocyte-neuronal exchanges in energy metabolism and for the first advances in the molecular mechanisms underling functional magnetic resonance imaging.

Two more events must be included in this abbreviated overview of the years at The Salk. Gary Jones had been a graduate student with the famous experimental psychologist Jim Olds at CalTech, who had also been Menahem Segal’s mentor. Jim was well known for his discovery of the internal reward pathways of the lateral hypothalamus and intracranial self-stimulation. When Jim died tragically while swimming in the Pacific, CalTech gave Gary the option to go to any lab he wished to complete his CalTech Ph.D. After considerable looking about, he opted to come with us at The Salk, and he chose for his project to record from locus coeruleus neurons in the awake behaving rat, a task that seemed as daunting as Steve’s efforts in the monkey, given the tiny size of the nucleus in a rat and the fact that their spontaneous locomotion made it almost impossible to record one unit long enough to try to define its environmental repertoire. Thankfully, Gary’s girlfriend Stephanie Aston made little leather hammocks that Gary trained the rats to lie still in, reinforced by flavored milk when they did. Gary became Aston-Jones when they married, and his thesis was published in two classical papers on locus coeruleus physiology in the first volume of the Journal of Neuroscience.

By this time, Steve Foote’s efforts in the monkey had paid off, and we were able to report that in both species, locus coeruleus neurons in awake, behaviorally responsive animals responded to novel events in the environment of any sensory modality, that they were most active when the animal was alert and focused on the environment, and slowed progressively with inattention, stopping completely during rapid eye movement sleep.

Gary has persisted with this problem, and his 2005 Annual Review of Neuroscience paper with Jonathon Cohen of Princeton establishes a far richer and more profound explanation of the locus coeruleus than I would ever have imagined we would know. Steve pursued the effects of corticotropin releasing factor on the locus coeruleus with Rita Valentino, and he later moved his labs to UCSD before he joined the Extramural Research Program of the National Institute of Mental Health. He quickly rose to become the Director of the Neuroscience Branch before taking an early retirement.

In early 1979, Rob Milner joined our lab from Gerald Edelman’s labs at The Rockefeller University, specifically to try to develop monoclonal antibody technology to enrich our studies of the neuropeptides. As he was developing these approaches with a Visiting Scholar from Israel, Ilana Gozes, a paper appeared in Nature from the Kyoto laboratory of Professor Numa showing that with cloning technology it was possible to determine the entire amino acid sequence of the common precursor of β-lipotropin and the adrenocorticotrophic hormone, ACTH, from the messenger RNA extracted from a dozen pituitary glands. Moreover, in analyzing the sequence of this precursor, they uncovered a third repeat of the melanocyte stimulating hormone that they proposed as a new signaling molecule waiting to be characterized.

I took this issue to my friend Richard Lerner at The Research Institute of the Scripps Clinic, only about three blocks away, and asked him why we couldn’t use a similar approach to find as yet undiscovered neuropeptides in the brain. He thought that was a crazy but possibly fruitful line and introduced me to his new postdoc, Greg Sutcliffe, who had just completed his Ph.D. at Harvard in the labs of Wally Gilbert by sequencing the most used cloning vehicle, the pBR322 plasmid. We agreed to a collaboration, and Greg and Rob did the work while Richard and I dreamed of the results.

By now, the growth of our group was making our 8000 square foot laboratory feel tight, and with the grant success that we had accumulated, our group could move with a lot less risk than when we left the NIH in 1976. I began to look around and accepted some invitations to visit. The search was made more pressing by the gossip that some of the professors at The Salk didn’t think alcohol research was a fitting topic for the Institute. When the colleagues at Scripps heard of this, Richard and his boss, Frank Dixon, suggested I consider moving around the corner. When I took them seriously and really started to explore the opportunity, the more exciting it seemed to be—we might now be able to carry our results from experimental animals to humans. But Dr. De Hoffman was incensed to think I would abandon what he had helped me create. While I was entitled to take with me all of the equipment I had purchased on my grants, I had no basic right to the equipment that he had purchased to get us started. Therein lay a year’s worth of negotiations, until it was agreed I could buy the start up equipment, since it was unlikely to be used by anyone else at Salk. In November, 1983, Nature ran a News Item saying “Bloom Moves South,” but they had mistaken the Research Institute of Scripps Clinic for the Scripps Institute of Oceanography; and we moved the three blocks north. As soon as we left, our Salk “carousel” labs were completely dismantled and refitted as conventional labs.

Leaving The Salk was a mixed emotional affair because I had made a lot of friends while there, and almost all of them remained my friends after the move. It had been a great place to receive visiting scientists, and we were pleased to get to know better some of the world’s leading scientists. The Iversens came at least three times in the summers and helped us work out in vitro peptide release assays. Kjell Fuxe and Torgny Svensson both spent winters from the Karolinska, with Kjell mostly playing tennis, while Torgny helped us recognize that alpha receptors in the cerebellum also played a role in the norepinephrine effects there. Guy Chouvet came from the Jouvet sleep labs in Lyon to work with Steve Henriksen, as did Alim (Ben) Benabid, a neurosurgeon from Grenoble who wanted to examine thalamic stimulation techniques—the start of deep brain stimulation as a treatment. The Salk was our home when I was elected President of the Society for Neuroscience, when I was elected to the National Academy of Sciences, and when I married Jody Corey. But it was time to move on.

The Scripps Years (1983 to the Present)

Given that I have spent the last 27 years at The Scripps Research Institute, it goes without saying that only the most superficial coverage of the research carried out here by my many colleagues is possible. We moved from The Salk during the Christmas break of 1983. Thanks to the hard work of the fellows like Charles Chavkin, Jakie McGinty, Jorge Mancillas, Lisa Giovanneli, and Franco Vaccarino, the labs were back in full operation quickly. These new labs were now divided into four separate working areas—neurohistology for light and electron microscopy with John Morrison and visits from Steve Foote; neurophysiology with George Siggins, Steve Henriksen, and Donna Gruol; neurochemistry with Rob Milner; and behavioral pharmacology under George Koob.

Our overall lab group was called the Division of Preclinical Endocrinology and Neuroscience, a part of Ernest Beutler’s Department of Clinical Medicine; the “endocrinology” term allowed us to be supported from two endowments under Beutler’s control. It was the first time we had any hard moneys we could count on since our startup days at Salk, and it was put to good advantage equipping the labs since we now had more than 50% more space than we had had previously. The four research groups now more or less ran their own shows, allowing the faculty to mature, but we maintained our training grant, the Alcohol Research Center, and the STARTREC sessions that were the main training vehicle.

For the first 6 years at Scripps, our more notable achievements were in undertaking highly detailed maps of the monoamine systems in nonhuman primate, a move pioneered by John Morrison with strong support from Steve Foote. With his fellows Mike Campbell and David Lewis, Morrison and Foote made detailed maps of the cortical regions, documented the interregional innervation density differences, and applied the latest methods of circuitry tracing to define the target neurons. After 2 years, David was recruited to the Psychiatry Department at the University of Pittsburgh, where he has just been appointed Chairman. With Ana de Lima, John Morrison defined with serial reconstructions the immunohistochemically defined serotonin terminals in cortex and the very tiny zones of synaptic specializations they possessed. Such an approach was necessary if one wanted to see those specializations that many others had denied existed.

When John had been a graduate student at Johns Hopkins, he had been in a serious automobile accident that traumatized his cervical spine, and the head-down position used to examine tissues in a microscope severely exacerbated his neck pains. This struck me as an unnecessary burden to place on my collaborator, and so we invested in an effort to modernize microscopic analysis by using high-definition video capture of images, and stepping motors to move the slides. This allowed us to do quantitative mapping and stereological analysis, for which Warren Young was able to write highly effective software. These investments earned us a berth in the Human Brain Mapping project when the brain-centric Institutes at NIH recognized they needed something to compare to the investment that had been made in the Human Genome Project.

John was also a major supporter in the project that Rob Milner and I undertook with Greg Sutcliffe, namely to employ differential and subtractive mRNA cloning to identify genes that were expressed in the brain but not in other tissues. From the calculations based on the first hundred or so such genes, Greg estimated that well over half of the mammalian genome could be either brain specific or brain enriched. There were so many brainspecific genes that, to gain a toehold, Greg and Rob started playing one brain region against another, using John’s knowledge of the primate brain regions and their higher but different degrees of cellular specialization—frontal versus motor versus visual cortex, for example. When such genes were identified with Greg’s help, we would seek to develop either antibodies to fragments of the proteins they encoded or to use in situ hybridization to map them out. This effort was supported by a Program Project grant in which Rob, Greg, John, and I each had component projects.

In my unit, we concentrated on technical developments that would allow the mapping of new brain-specific gene expression sites more quickly and more completely. The original approach had been to try to raise antibodies against synthetic fragments of the newly discovered gene product. But even when coupled to highly foreign proteins like keyhole limpet hemocyanin, antibodies with titers high enough and avidity high enough failed to be acceptable for immunohistochemistry. In 1989, Gustave Jirikowski came to work with us on a Heisenberg Fellowship and brought with him an excellent monoclonal antibody to Bromo-deoxyuridine, a tag that could be incorporated into in situ hybridization probes, and then localized with Gustave’s antibody. His studies led us to find that for some neurons, such as the magnocellular hypothalamic neurons, mRNA was found in axons and increased there with demands on the system, like water deprivation. His studies with Pietro Sanna (who came to us with the recommendation of Rita Levi-Montalcini) and Dominique Maciejewski-Lenoir also demonstrated an uptake by neurons of some selected mRNAs, a finding that remains to be replicated, but to me was one of enormous potential. Marisela Morales and Alain Trembleau developed methods to bring in situ hybridization to even higher resolution using multiple oligonucleotide probes and fluorescent labeling. Marisela collaborated with scientists at The Salk to map out and define the population of interneurons bearing the 5HT-3 receptor, the only monoamine receptor not to be a G protein–coupled receptor. Marisela is now a tenured scientist at the National Institute of Drug Abuse, and Alain was recently appointed at College de France.

In Rob’s unit, the focus initially was on myelin and astrocytes, and his trainees Cary Lai and Klaus Nave each acquired exemplary observations that have launched distinguished careers—Klaus as Director of the Max Planck Institute for Experimental Medicine at the University of Göttingen, and Cary as Professor of Neuroscience and Genetics at the University of Indiana. Rob left us to become Chairman of Neuroscience at the Penn State University School of Medicine. In Greg’s Unit, the effort was focused on finding brain-region selective gene expression, and such genes were found to be abundant. The apex of this emerged from studies of hypothalamically enriched gene expression, one of which on initial in situ hybridization was clearly localized to a bilaterally symmetrical nucleus that was near to but was not the paraventricular nucleus. Sequencing revealed this gene to encode a secretin-like peptide and, since it was in the hypothalamus, Greg named it hypocretin. Interestingly, these neurons have a limited efferent circuitry, one of their targets being the locus coeruleus. The hypocretin neurons seem to play a role in a variety of vegetative functions, including appetite, blood pressure, and sleep. Mutations of the peptide or its receptor have been reported to cause narcolepsy, and drugs based on the peptide are being developed to treat the disease.

Although John was trained in neuroanatomy, my knowledge of circuitry was loosely based on what I had learned in medical school, supplemented by many trips to the library. Every time we identified an interesting new brain-specific gene, and John and I attempted to map it out, a new complete analysis from olfactory bulb to spinal cord was required. It frustrated me to have to look up so many circuits so many times. Then the thought occurred to me that maybe I could create a database of the known circuitry, transmitters, and receptors. I could then attribute to the circuits the cellular and system properties they were thought to regulate, and the behaviors in which they were thought to participate, so that when the next new one came along we could gain insight just from the mapping. After all, in neuroscience “Where?” is a very important question. This line of reasoning led to many attempts to employ computer databases, but none that were available to me could handle the known complexity of real brains, that is, until Hypercard was released by Apple. On a trip home from a meeting at NIH, I bought the software, read the manual, and sketched out the major organization of the database that Warren Young and I later published as the Brain Browser (several years before there were Internet browsers). Although Brain Browser was not a real database, it was an easy-to-use, intuitive way to organize information about the brain’s circuitry that has never been replicated. It is now obsolete since Apple did not maintain the program to work with current operating systems.

Another very large program of research came our way when the National Institute of Mental Health put out a request for proposals to develop research centers to study the basis for the effects of HIV infection on the brain. While other NIH Institutes had invested heavily in this area of work, the NIMH had not, and now they wanted to catch up. We at Scripps had considerable assets in this area, with several noted virologists who had been studying viruses known to attack the nervous system (Mike Oldstone and his colleagues Jay Nelson and Michael Buchmeier) and another investigator, John Elder, who had been one of the first to identify the comparable retroviral disease in cats, the feline immunodeficiency virus. In addition, we had Tom Edgington and his colleagues who were expert in the cellular and molecular aspects of inflammatory reactions. We competed, and we were funded in one of the largest grants to that point that had ever come to Scripps. As a reward, we were designated the Department of Neuropharmacology and given the entire first floor of a new research building that Scripps had leased on the eastern part of our campus. At this point we had grown to more than five times the space we had occupied at The Salk Institute.

Science (1995–2000)

While all was going quite swimmingly in the laboratory on virtually every front, I began getting “feeler” messages inquiring whether I had any interest in becoming Editor-in-Chief at Science, the weekly magazine of general science owned and operated by the American Association for the Advancement of Science (AAAS). It is one of the two most widely read journals in the world, with a subscriber list perhaps four times that of the other such journal, Nature. Daniel Koshland, who had been the Editor-in-Chief, had announced his retirement, and the Board of the AAAS had formed a search committee. Although I had made a previous arrangement with Elsevier Publishers to take on the Chief Editorship of their five journals in Brain Research (Brain Research, Molecular Brain Research, Developmental Brain Research, Cognitive Brain Research, and Brain Research Reviews), the opportunity to work at Science was too important to dismiss, and so I expressed a sincere interest.

At the Society for Neuroscience meeting in the fall of 1994, the Science news reporter Marcia Barinaga and I were chatting, and I asked her what the status of the Editor search was. She told me she thought I was the choice, although no one had said anything to me. Then in December that year, Rich Nicholson, the Executive Officer of AAAS, asked if he could fly in from Washington to speak to me, and he offered me the job. I flew up to see Dan Koshland at Berkeley to begin to understand what I had to learn, and I asked him how much of my time I should set aside to do the job. He told me he thought I could do it in about 25% of my time. That seemed reasonable, and I thought the easiest way to gain 25% of my time back for this new opportunity was to relinquish being Director of the Alcohol Research Center. George Koob agreed to take it on. After enough delay to indicate I had thought seriously about it, I agreed to accept the AAAS offer, effective July 1. However, since I didn’t want to live in Washington, DC, where AAAS and Science are based, there was a sizable chunk of budget that had been set aside for the new Editor’s moving expenses that could now be reinvested.

In the spring of 1995, Ellis Rubinstein, the head of the News Department at Science, came to Scripps to start briefing me about the job’s responsibilities, the internal politics of the organization, the decisions that were going to have to be made, and the opportunities that lie ahead. In February, I went to Washington to meet some of the 200 staff members and get a feel for the work ahead. My introduction was facilitated greatly by Monica Bradford, who was then the Managing Editor and responsible for the review and production of the elements in the original research and research commentary parts of Science. Although most scientists, if asked why they read Science, would respond that it was for the science, the magazine covered all of science but had the space to publish only 15 articles a week. Thus, most issues would have very little to offer any given field. In reality, the front half of the magazine, carrying the global news of science and the scientific community, had something for everyone. The one weak spot to me was the Book Reviews section, which chose to review books that to me were less than appealing and that were often divisive, pitting one philosophy of science against another. I resolved to see how this might be improved.

The Editor-in-Chief at Science is there primarily to represent the academic scientific community when it comes to resolving disputes between authors and reviewers, helping the review editors render fair and prompt decisions about submittals, but rarely helping the news side see broader perspectives on some issues being covered. In the scientific disciplines, the original research submittals were handled by 18 or so editors with Ph.D. degrees in the fields that were their responsibility. The review process installed by Dan Koshland employed a Board of Reviewing Editors—known to the staff as the BoRE—who had the current expertise of an active bench scientist (I had been one of the BoRE in neuroscience). Each week BoRE members were FedEx-ed a packet of submittals and asked to comment on them under the proposition: If the results claimed in this paper were true, would that be significant and important enough to be a Science paper? If the answer were yes, what scientists would make the best reviewers? Those comments were supposed to be returned by fax, or by e-mail for those who did it, within 48 hours.

The original research editors would send their papers out for review, nudge the reviewers for their decisions, then make a tentative decision and once a week present their current portfolio to the other editors to gain group support for an acceptance, given that they were all competing for the constrained space of the weekly table of contents. Original research editors were working either in Washington, DC, or in the European office based in Cambridge, England, so the entire meeting was a teleconference, which either the Editor-in-Chief or the Managing Editor would chair. From what I learned, these meetings were frequently quite intense events that could evoke anger and sour working relations.

Armed with these early insights into the operations, when I reported for duty in July, I was faced with an unexpected immediate need for a decision: It seemed that the estimated costs of the paper used to print the magazine were going to be raised above budget, and the costs of the postal and air deliveries for the weekly issues were also going up. However the AAAS was a nonprofit organization, so this also meant it was a no-loss organization. Where in the magazine’s budget would I propose to trim the extra sums needed?

Searching about, I learned that in Koshland’s last year, the editors had looked closely at ways to start transmitting Science over the Internet but, knowing that he would leave, those ideas had been put on hold. As we began to think about the possible budget shortfall, we received a request to meet with John Sack and Mike Keller from Stanford University’s library, who were developing an electronic publishing service named HighWire Press, aimed initially at nonprofit societies with journals. We were immediately captivated, and after a demo and a lot of discussion, despite the upfront costs incurred, we were on board. In October of 1995, Science went online, the third journal to do so after the Journal of Biological Chemistry and the Journal of Neuroscience. Once that decision had been taken, the door opened on what the online journal should and could be. We resolved from the beginning that Science online would be more than just a digital version of the printed magazine, but would offer tools for scholars that could empower the dissemination of knowledge.

Before this new job in Washington, it used to be said that the two things you never wanted to watch being made were sausages and laws. To that, after my experiences, I would add a weekly science magazine. Plans for properly filling the pages, and placing the ads—necessary for support of the magazine and the society—extend weeks into the future. The ability to lay out the original research articles in the no-space-is-wasted format that Science employs will look even harder when one knows that, unless all the authors approve and return their galley proofs on time, that the space designated for one article cannot exactly be filled by any other. All of these problems and more came into play when it became necessary to expand the weekly workflow to convert the text and graphics into the hypertext markup language (HTML) that is used to present information on the World Wide Web, and that in 1995 was not exactly well understood. Then we eventually came to realize that, while putting the journal online might reduce the cost of dissemination, it did not lessen the costs of production and that creating the software to implement the tools for scholars that the Editors and I creatively flung at our readers could become quite costly.

Rather than dwell on the enormous number of issues that arose and were solved, I will just note that the book review section was changed, and a new way for each original research editor to handle the submittals in his or her field was found. As the most senior of those editors, Mrs. Eleanore Butz, used to point out, the best papers came when the editors spoke to the leaders in their fields of coverage to find out what exciting new data they had heard about and got that author to consider sending his or her work to Science. She called this “shmoozing.” It was her view that if they waited for the papers to come in on their own, the best would go elsewhere and it was much too late. Of the matters I was pleased to have had more than a hand in, the creation of Science’s NextWave and the Science signal transduction knowledge environment (STKE) are right at the top of the list.

Science’s NextWave as an online-only publication started even sooner than the time when Science itself went online. It was based on an idea brought to me by Ellis and one of his news editors, John Benditt, that we should do something for graduate students and postdoctoral fellows who were trying to determine what they should do with their scientific education when they grew up, and maybe even help graduate students select the areas where they might work. That site, now combined with the Science employment opportunities in Science Careers, is supported by graduate universities and educational systems globally and has been warmly received by students and faculty, especially those who may have grown dissatisfied with their current line of work.

Science’s STKE was another opportunity for an online information system to emerge. Our editors found that the same principal signal transduction pathways were often being pursued in many different experimental systems and in each one, the various components had different names and those communities rarely spoke to each other. The STKE was conceived as a way to portray graphically these signal transduction pathways and allow species-specific terminology to be compared and contrasted. Those connection maps can be seen today, and the reviews and special articles that illuminate the pathways are still leaps and bounds ahead of any other summarizing system for signal transduction. I note that in the past year, the STKE has also begun to publish original research in the area of signal transduction.

In my final year as Editor-in-Chief, Science did a “Pathways of Discovery” series as special coverage of the calendrical transition into the next millennium, portraying the pathways of discovery across all of science from quantum physics to cosmology and from genomics to atmospheric sciences. For each topic covered, distinguished scientists reviewed what they saw as the major past heuristic accomplishments along the intellectual pathways of that field and then attempted an extrapolation into the future from discoveries unfolding then. My inspiration for this series arose when my wife and I visited the original site of the Hong Kong University Medical School where the Hong Kong Radiological Society had erected a display of how Roentgen’s observations on the physics of X-ray led to the development of medical imaging, and it then occurred to me to document how the 20th century was filled with examples of advances in one field of science creating opportunities for advances in many other fields. My neuroscience mentor, F. O. Schmitt, often pointed out how the neurosciences frequently exploited advances in other fields to move ahead. My editors at Science agreed and we moved ahead with this plan.

To help lay out our year of Pathways essays, Science’s editors assembled a graphical timeline of major past events and agents of discovery. These timelines served as convenient simplifications of the spectacular and progressive accumulation of insight and understanding scientists have achieved. In my editorial announcing these plans I invoked a visual metaphor of this progress as an intricate circulatory system with multiple ever-finer branchings that often interconnect with other parts of the nexus. While science has indeed become a process of continuous specialization, each new capillary of investigation contributes to the overall understanding. Each new branch of science can open wondrous new opportunities while posing societal challenges that will require vigilance and insightful management. For me, the most remarkable conclusion to emerge from this exercise was the realization that in the millennium we were about to leave, humanity’s knowledge of its place in the universe had moved from St. Thomas Aquinas’s view that knowledge was of two types—that which man could know and that which was “higher than man’s knowledge” and not to be sought through reason—to the belief begun with Newton’s Principia that our universe and all within it are indeed knowable.

After 4 years of being Editor-in-Chief, I had grown weary from the time spent commuting between California and Washington, DC. I also recognized that this was not the final post I wished to hold and asked to be replaced after my fifth year on the job. In my final editorial, of the 50 or so that I wrote, I offered some reflections on the interesting times (in the Chinese sense of the term) through which we had traveled. It was my good fortune to witness truly amazing discoveries and achievements. Among those that remain most intensely etched in my mind are the evidence for possible life on Mars, the Bose-Einstein condensate, the emergence of nanotechnology, the expanding universe, the basis for nearby planetary chaos, and remarkable archaeological insights into human origins. Equally thrilling to recall are the whole bacterial and plant genomes already sequenced, as well as C. elegans, Drosophila, and soon the human genome; the atomic coordinates of complex molecules such as cytochrome C, erythropoietin, immunoglobulin enfolding its antigens, and the potassium channel; the chemokines and their receptors through which HIV infects; numerous new regulatory peptides and markers of oncogenic vulnerability; the cloning of whole animals; the isolation of adult totipotent stem cells; and many, many more. As a life scientist, I always shuddered when the popular press found the articles about bones and rocks more interesting than the insights into biology and medicine.

Unquestionably, those 5 years were most vividly epitomized by the ascent of the Internet and the significant changes that it was and still is imposing on scholarly publishing, as well as on almost every other aspect of our society. I concluded by noting that Science will likely continue to refine and evolve these adaptations as new and better means of communication emerge. I eschewed technology that merely intensifies the information glut faced by scientists because the Internet makes possible such accelerated information access. Mountainous collections of information, unorganized, unanalyzed, and uncategorized, become useful only when experts take over and interpret the mountains with perspective. Drawing knowledge from information remains an overarching goal for Science.

Current Activities and Conclusions

Returning to my responsibilities at Scripps, I found myself with no grants, no postdoctoral fellows, and no active research except for that being done in the Alcohol Research Center and the Neuro-AIDS Center, and even there I was not current with recent developments. I knew that I dare not try to write new grants, for surely among those grants’ peer reviewers would be authors whose papers had been rejected while I was at Science, and scientists do take those things personally. I therefore looked for other ways to apply my experience.

Greg Sutcliffe had by now started a biotech company, Digital Gene Technology, based on work done in his labs to make the high throughput comparison of specific mRNAs much more sensitive and accurate than the gene array technologies of the time, and he invited me to serve on his scientific advisory committee. This committee was charged with evaluating proposals from academic labs to take up some unused capacity in their assay systems, and to popularize what the technology could do. My comment after many of those reviews was that if you can identify this unique gene whose expression is changed by this perturbation, then the next goal should be to map it. After repeating that assertion innumerable times, the CEO, Greg’s brother Bob, said to me, “What don’t you start a company to do that?” It seemed like a great idea and, with his help, we raised the funds to launch Neurome, Inc., to develop high throughput means to map and compare gene expression in mouse transgenic models of human neurological diseases, to spot the earliest sites of neuropathology, and to use that information to assess the ability of a therapeutic intervention to halt or reverse the pathology.

The founders with me were my colleagues John Morrison and Warren Young. Through a variety of contracts with Elan Pharmaceuticals, we were able to study their mouse model of amyloid accumulation as a form of Alzheimer disease. This mouse model incidentally had been developed by Dora Games, one of the original research technicians at the Davis Center labs at The Salk (see Fig. 1.4), who had then gone to graduate school and obtained a Ph.D. Our Neurome scientists, Jeff Redwine, John Reilly, Ron Broide, and Chi-Cheng Wu, developed excellent stereological quantification methods that grew into compelling and comprehensive quantitative documentation that, in this mouse model, the earliest changes in synapses and dendritic spines occurred in the outer molecular layer of the dentate gyrus weeks before any amyloid accumulations were detectable. Work on different mouse models resulted in a contract with Wyeth Pharmaceuticals, intended to lead up to a therapeutic intervention study, and work with Merck seemed to have gone well enough to support the in-licensing of an antistroke medication. Nevertheless, because the bubble had long since burst in biotech, sufficient financing was impossible to arrange, and Neurome was forced to close in 2006. Nevertheless, the thrill of discovery and applying new quantitative methods to discern the earliest pathological changes in the brains of mice expressing the familial form of Alzheimer disease allowed me to take another swing at the application of neuroscience to neurological disease. It was not the science that failed here but the lack of proper business training that allowed me to make managerial mistakes that might have been avoided and allowed the company a longer life.

My activities have now turned mainly to consultation and the offering of advice. At the 2004 meeting of the Society for Neuroscience, my colleagues created for me a massive “Bloom Science Family Tree” that illustrated how those who had been trainees with me, then trained others, who trained others, and so on for four generations, and encompassing more than a thousand scientists. Having mentored that stream of discoverers, I have to admit to a feeling of some self-satisfaction.

Today, I serve as a Trustee for Washington University in St. Louis and chair their National Council for the School of Medicine. I completed 3 years on President Bush’s Presidential Council on Bioethics, and I am in my third year as a member of the Independent Citizens Oversight Committee for the California Institute of Regenerative Medicine (the Proposition 71 Stem Cell initiative).

These transitions in my role as a scientist have not gone unnoticed. I liken my evolution to the progression of the workers in Vannevar Bush’s quarry of science essay, “Science Is Not Enough.” He conceives of knowledge as an edifice that once existed and whose parts have been scattered, hidden, and buried, awaiting scientists to find them and reassemble an organized science. He identifies some workers in this quarry as “those content to dig away, unearth odd blocks, pile them up for others to view and caring not whether they fit in now” and others as “those who sit by and give advice, and those who just sit.” But he also describes “those men of rare vision who can grasp well in advance just the block that is needed to advance construction rapidly and can tell by some subtle sense where it will be found.” I feel I was once one of those men of rare vision, and occasionally still am. Perhaps some readers may be inspired by what my colleagues and I were able to find and reassemble, and gain confidence to move along their own chosen paths.

Selected Bibliography

Original Research

Aghajanian, G.K., and Bloom, F.E. Electron-microscopic autoradiography of rat hypothalamus after intraventricular ³H-norepinephrine. Science, 153: 308–310, 1966.

Arnsten, A.F.T., Segal, D.S., Janowsky, D.S., Judd, L.L., Hillyard, S.T., Neville, H.J., and Bloom, F.E. Naloxone augments electrophysiological signs of selective attention in man. Nature, 304: 725–727, 1983.

Aston-Jones, G., and Bloom, F.E. Activity of norepinephrine-containing locus coeruleus neurons in behaving rats anticipates fluctuations in the sleep-waking cycle. J. Neurosci., 1: 876–886, 1981.

Aston-Jones, G., and Bloom, F.E. Norepinephrine-containing locus coeruleus neurons in behaving rats exhibit pronounced response to non-noxious environmental stimuli. J. Neurosci., 1: 887–900, 1981.

Aston-Jones, G., Foote, S., and Bloom, F. Low doses of ethanol disrupt sensory responses of brain noradrenergic neurones. Nature, 296: 857–860, 1982.

Bayon, A., Koda, L., Battenberg, E., and Bloom, F.E. Redistribution of endorphin and enkephalin immunoreactivity in the rat brain and pituitary after in vivo treatment with colchicine or cytochalasin B. Brain Res., 183: 103–111, 1980.

Bayon, A., Rossier, J., Mauss, A., Bloom, F.E., Iversen, L.L., Ling, N., and Guillemin, R.In vitro release of [5-methionine] enkephalin and [5-leucine]-enkephalin from the rat globus pallidus. Proc. Natl. Acad. Sci. U.S.A., 75: 3503–3506, 1978.

Benabid, A.L., Henriksen, S.J., McGinty, J.F., and Bloom, F.E. Thalamic nucleus ventro postero-lateralis inhibits nucleus parafascicularis response to noxious stimuli through a non-opioid pathway. Brain Res., 280: 217–231, 1983.

Bloch, B., Brazeau, P., Ling, N., Bohlen, P., Esch, F., Wehrenberg, W., Benoit, R., Bloom, F., and Guillemin, R. Immunohistochemical detection of growth hormone releasing factor in brain. Nature, 301: 607–608, 1983.

Bloom, F., Battenberg, E., Rossier, J., Ling, N., and Guillemin, R. Neurons containing β-endorphin in rat brain exist separately from those containing enkephalin: Immunocytochemical studies. Proc. Natl. Acad. Sci. U.S.A., 75: 1591–1595, 1978.

Bloom, F., Segal, D., Ling, N., and Guillemin, R. Endorphins: Profound behavioral effects in rats suggest new etiological factors in mental illness. Science, 194: 630–632, 1976.

Bloom, F.E. Science as a way of life: Perplexities of a physician-scientist. Science, 300: 1680–1685, 2003.

Bloom, F.E., Algeri, S., Groppetti, A., Revuelta, A., and Costa, E. Lesions of central norepinephrine terminals with 6-OH-Dopamine: Biochemistry and fine structure. Science, 166: 1284–1286, 1969.

Bloom, F.E., and Aghajanian, G.K. An electron microscopic analysis of large granular synaptic vesicles of the brain in relation to monoamine content. J. Pharmacol., 159: 261–273, 1968.

Bloom, F.E., and Aghajanian, G.K. Fine structural and cytochemical analysis of the staining of synaptic junctions with phosphotungstic acid. J. Ultr. Res., 22: 361–376, 1968.

Bloom, F.E., and Barrnett, R.J. Fine structural localization of acetylcholinesterase in the electroplaque of the electric eel. J. Cell Biol., 29: 475–496, 1966.

Bloom, F.E., and Barrnett, R.J. Fine structural localization of noradrenaline in nerve ending vesicles of the autonomic nervous system. Nature, 210: 599–601, 1966.

Bloom, F.E., and Battenberg, E.L.F. A rapid, simple and more sensitive method for the demonstration of central catecholamine-containing neurons and axons by glyoxylic acid induced fluorescence: II. A detailed description of methodology. J. Histochem. Cytochem., 24: 561–571, 1976.

Bloom, F.E., and Iversen, L. L. Localizing 3H-GABA in nerve terminals of rat cerebral cortex by electron microscopic autoradiography. Nature, 229: 628–630, 1971.

Bloom, F.E., and Schoepfle, G.M. Kinetics of procaine-acetylcholine antagonism. Am. J. Physiol., 204: 73–76, 1963.

Bloom, F.E., Battenberg, E.L.F., Milner, R.J., and Sutcliffe, J.G. Immunocytochemical mapping of 1B236, a brain specific neuronal polypeptide deduced from the sequence of a cloned mRNA. J. Neurosci., 5: 1781–1802, 1985.

Bloom, F.E., Costa, E., and Salmoiraghi, G.C. Analysis of individual rabbit olfactory bulb neuron response to microelectrophoresis of acetylcholine, norepinephrine and serotonin synergists and antagonists. J. Pharmacol., 146: 16–23, 1964.

Bloom, F.E., Costa, E., and Salmoiraghi, G.C. Anesthesia and the responsiveness of individual neurons of the cat’s caudate nucleus to acetylcholine, norepinephrine, and dopamine administered by microelectrophoresis. J. Pharmacol., 150: 244–255, 1965.

Bloom, F.E., Hoffer, B.J., and Siggins, G.R. Studies on norepinephrine-containing afferents to Purkinje cells of rat cerebellum: I. Localization of the fibers and their synapses. Brain Res., 25: 501–521, 1971.

Bloom, F.E., Hoffer, B.J., Battenberg, E.F., Siggins, G.R., Steiner, A.L., Parker, C.W., and Wedner, H.J. Adenosine 3,’5’-monophosphate is localized in cerebellar neurons: Immunofluorescence evidence. Science, 177: 436–438, 1972.

Bloom, F.E., Stone, T.W., and Taylor, D.A. Responses of identified cerebral cortical neurones to cyclic GMP and cyclic AMP. J. Physiol., 246: 103–104, 1974.

Broide, R.S., Redwine, J.M., Aftahi, N., Young, W., Bloom, F.E., and Winrow, C.J. Distribution of histone deacetylases 1–11 in the rat brain. J Mol Neurosci., 31(1): 47–58, 2007.

Chavkin, C., Bakhit, C., Weber, E., and Bloom, F.E. Relative contents and concomitant releases of prodynorphin/neoendorphin-derived peptides in rat hippocampus. Proc. Natl. Acad. Sci. U.S.A., 80: 7669–7673, 1983.

Chu, N-s. and Bloom, F.E. Norepinephrine-containing neurons: Changes in spontaneous discharge patterns during unrestrained sleeping and waking. Science, 179: 908–910, 1973.

de Lecea, L., Kilduff, T.S., Peyron, C., Gao, X.-B., Foye, P.E., Danielson, P.E., Fukuhara, C., Battenberg, E.L.F., Gautvik, V.T., Bartlett, F.S., Frankel, W.N., Pol, A.N., Bloom, F.E., Gautvik, K.M., and Sutcliffe, J.G. The hypocretins: Hypothalamus-specific peptides with neuroexcitatory activity. Proc. Natl. Acad. Sci. U.S.A., 95: 322–327, 1998.

DeCamilli, P., Ueda, T., Bloom, F.E., Battenberg, E. and Greengard, P. Widespread distribution of Protein I in the central and peripheral nervous system. Proc. Natl. Acad. Sci., 76: 5977–5981, 1979.

Deyo, S.N., Shoemaker, W.J., Ettenberg, A., Bloom, F.E., and Koob, G.F. Subcutaneous administration of behaviorally effective doses of arginine vasopressin change brain AVP content only in median eminence. Neuroendocrinology, 42: 260–266, 1986.

Elmasion, R., Neville, H., Woods, D., Schuckit, M., and Bloom, F. Event-related brain potentials are different in individuals at high and low risk for developing alcoholism. Proc. Natl. Acad. Sci. U.S.A., 79: 7900–7903, 1982.

Ferron, A., Siggins, G.R., and Bloom, F.E. Vasoactive intestinal polypeptide acts synergistically with norepinephrine to depress spontaneous discharge rate in cerebral cortical neurons. Proc. Natl. Acad. Sci. U.S.A., 82: 8810–8812, 1985.

Foote, S.L., Aston-Jones, G., and Bloom, F.E. Impulse activity of locus coeruleus neurons in awake rats and monkeys is a function of sensory stimulation and arousal. Proc. Natl. Acad. Sci. U.S.A., 77: 3033–3037, 1980.

Fox, H.S., Gold, L.H., Henriksen, S.J., and Bloom, F.E. Simian immunodeficiency virus: A model for Neuro AIDS. Neurobiol. Dis., 4: 265–274, 1997.

Freedman, R., Foote, S.L., and Bloom, F.E. Histochemical characterization of the neocortical projection of the nucleus locus coeruleus in the squirrel monkey. J. Comp. Neurol., 164: 209–232, 1975.

Gautvik, K.M., de Lecea, L., Gautvik, V.T., Danielson, P.E., Tranque, P., Dopazo, A., Bloom, F.E., and Sutcliffe, J.G. Overview of the most prevalent hypothalamusspecific mRNAs, as identified by directional tag PCR subtraction. Proc. Natl. Acad. Sci. U.S.A., 93: 8733–8738, 1996.

Granholm, A-C., Backman, C., Bloom, F., Ebendal, T., Gerhardt, A., Hoffer, B., Mackerlova, L., Olson, L., Soderstrom, S., Walus, L.R., and Friden, P.M. NGF and anti-transferrin receptor antibody conjugate: Short and long-term effects on survival of cholinergic neurons in intraocular septal transplants. J. Pharmacol. Exper. Therapeutics, 268: 448–459, 1994.

Hoffer, B.J., Siggins, G.R., and Bloom, F.E. Studies on norepinephrine-containing afferents to Purkinje cells of rat cerebellum: II. Sensitivity of Purkinje cells to norepinephrine and related substances administered by microiontophoresis. Brain Res., 25: 523–534, 1971.

Hoffer, B.J., Siggins, G.R., Oliver, A.P., and Bloom, F.E. Activation of the pathway from locus coeruleus to rat cerebellar Purkinje neurons: Pharmacological evidence of noradrenergic central inhibition. J. Pharmacol. Exp. Therap., 184: 553–569, 1973.

Iversen, L.L., and Bloom, F.E. Studies of the uptake of 3H-GABA and 3H-Glycine in slices and homogenates of rat brain and spinal cord by electron microscopic autoradiography. Brain Res., 41: 131–143, 1972.

Iversen, L.L., Iversen, S.D., and Bloom, F.E. Opiate receptors influence vasopressin release from nerve terminals in rat neurohypophysis. Nature, 284: 350–351, 1980.

Iversen, L.L., Rossor, M.N., Reynolds, G.P., Hills, R., Roth, M., Mountjoy, C.J., Foote, S.L., Morrison, J.H., and Bloom, F.E. Loss of pigmented dopamine-β-hydroxylase positive cells from locus coeruleus in senile dementia of Alzheimer’s type. Neurosci. Lett., 39: 95–100, 1983.

Jacobsen, J.S., Wu, C.C., Redwine, J.M., Comery, T.A., Arias, R., Bowlby, M., Martone, R., Morrison, J.H., Pangalos, M.N., Reinhart, P.H., and Bloom, F.E. Early-onset behavioral and synaptic deficits in a mouse model of Alzheimer’s disease. Proc. Natl. Acad. Sci. U.S.A., 103(13): 5161–5166, 2006.

Jirikowski, G.F., Sanna, P.P., and Bloom, F.E. mRNA coding for oxytocin is present in axons of the hypothalamo-neurohypophysial tract. Proc. Natl. Acad. Sci. U.S.A., 87: 7400–7404, 1990.

Jirikowski, G.F., Sanna, P.P., Maciejewski-Lenoir, D., and Bloom, F.E. Reversal of diabetes insipidus in Brattleboro rat after intrahypothalamic injection of vasopressin mRNA. Science, 255: 996–998, 1992.

Koda, L.Y., Schulman, J.A., and Bloom, F.E. Ultrastructural identification of noradrenergic terminals in rat hippocampus, unilateral destruction of the locus coeruleus with 6-hydroxydopamine. Brain Res., 145: 190–195, 1978.

Lai, C., Brow, M.A., Nave, K-A., Noronha, A.B., Quarles, R.H., Bloom, F.E., Milner, R.J., and Sutcliffe, J.G. Two forms of 1B236/myelin-associated glycoprotein (MAG), a cell adhesion molecule for postnatal neural development, are produced by alternative splicing. Proc. Natl. Acad. Sci. U.S.A., 84: 4337–4341, 1987.

Landis, S.C. and Bloom, F.E. Ultrastructural identification of noradrenergic boutons in mutant and normal mouse cerebellar cortex. Brain Res., 96: 299–306, 1975.

Le Moal, M., Koob, G.F., Koda, L.Y., Bloom, F.E., Manning, M., Sawyer, W.H., and Rivier, J. Vasopressor receptor antagonist prevents behavioural effects of vasopressin. Nature, 291: 491–493, 1981.

Loughlin, S.E., Foote, S.L., and Bloom, F.E. Efferent projections of nucleus locus coeruleus: topographic organization of cells or origin demonstrated by threedimensional reconstruction. Neuroscience, 18: 291–306, 1986.

Malfroy, B., Bakhit, C., Bloom, F.E., Sutcliffe, J.G., and Milner, R.J. The brain specific polypeptide 1B236 exists in multiple molecular forms. Proc. Natl. Acad. Sci. U.S.A., 82: 2009–2013, 1985.

McGinty, J.F., Henriksen, S.J., Goldstein, A., Terenius, L., and Bloom, F.E. Dynorphin is contained within hippocampal mossy fibers: Immunochemical alterations after kainic acid administration and colchicine-induced neurotoxicity. Proc. Natl. Acad. Sci. U.S.A., 80: 589–593, 1983.

Miller, F.D., Naus, C.C.G., Higgins, G.A., Bloom, F.E., and Milner, R.J. Developmentally regulated rat brain mRNAs: Molecular and anatomical characterization. J. Neurosci., 7: 2433–2444, 1987.

Morales, M., and Bloom, F.E. The 5-HT3 receptor is present in different subpopulations of GABAergic neurons in the rat telencephalon. J. of Neurosci., 17(9): 3157–3167, 1997.

Morales, M., Battenberg, E., de Lecea, L., Sanna, P.P., and Bloom, F.E. Cellular and subcellular immunolocalization of the type 3 serotonin receptor in the rat central nervous system. Mol. Brain Res., 36: 251–260, 1996.

Morrison, J.H., Foote, S.L., Molliver, M.E., Bloom, F.E., and Lidov, H.G.W. Noradrenergic and serotonergic fibers innervate complementary layers in monkey primary visual cortex: An immunohistochemical study. Proc. Natl. Acad. Sci. U.S.A., 79: 2401–2405, 1982.

Morrison, J.H., Rogers, J., Scherr, S., Benoit, R., and Bloom, F.E. Neuritic plaques of Alzheimer’s patients contain somatostatin immunoreactivity. Nature, 314: 90–92, 1985.

Nave, K-A., Lai, C., Bloom, F.E., and Milner, R.J. Splice site selection in the proteolipid protein (PLP) gene transcript and primary structure of the DM-20 protein of CNS myelin. Proc. Natl. Acad. Sci. U.S.A., 84: 5665–5669, 1987.

Nicholson, J.L., and Bloom, F.E. Ontogeny of monoamine neurons in the locus coeruleus, raphe nuclei and substantia nigra of the rat. I. Cell differentiation. J. Comp. Neurol., 155: 469–482, 1974.

Nicoll, R.A., Siggins, G.R., Ling, N., Bloom, F.E. and Guillemin, R. Neuronal actions of endorphins and enkephalins among brain regions: A comparative microiontophoretic study. Proc. Natl. Acad. Sci., 74(6): 2584–2588, 1977.

Nimchinsky, E.A., Young, W.G., Yeung, G., Shah, R.A., Gordon, J.W., Bloom, F.E., Morrison, J.H., and Hof, P.R. Differential vulnerability of oculomotor, facial, and hypoglossal nuclei in G86R superoxide dismutase transgenic mice. J. Comp. Neurol., 416: 112–125, 2000.

Oyler, G.A., Higgins, G.A., Hart, R.A., Battenberg, E., Billingsley, M., Bloom, F.E., and Wilson, M.C. The identification of a novel synaptosomal-associated protein, SNAP-25, differentially expressed by neuronal subpopulations. J Cell Biology, 109: 3039–3052, 1989.

Pickel, V.M., Krebs, W.H., and Bloom, F.E. Proliferation of norepinephrinecontaining axons in rat cerebellar cortex after peduncle lesions. Brain Res., 59: 169–179, 1973.

Pickel, V.M., Segal, M., and Bloom, F.E. A radioautographic study of the efferent pathways of the nucleus locus coeruleus. J. Comp. Neurol., 155: 15–42, 1974.

Pickel, V.M., Segal, M., and Bloom, F.E. Axonal proliferation following lesions of cerebellar peduncles. A combined fluorescence microscopic and radioautographic study. J. Comp. Neurol., 155: 43–60, 1974.

Polich, J., and Bloom, F.E. P300 from normal and adult children of alcoholics. Alcohol, 4: 301–305, 1987.

Polich, J., Burns, T., and Bloom, F.E. P300 and the risk for alcoholism: Family history, task difficulty, and gender. Alcoholism: Clin. Exp. Res., 12: 248–254, 1988.

Redwine, J.M., Kosofsky, B., Jacobs, R.E., Games, D., Reilly, J.F., Morrison, J.H., Young, W.G., and Bloom, F.E. Dentate gyrus volume is reduced before onset of plaque formation in PDAPP mice: A magnetic resonance microscopy and stereologic analysis Proc. Natl. Acad. Sci. U.S.A., 100: 1381–1386, 2003.

Reilly, J.F., Games, D., Rydel, R.E., Freedman, S., Schenk, D., Young, W.G., Morrison, J.H., and Bloom, F.E. Amyloid deposition in the hippocampus and entorhinal cortex: Quantitative analysis of a transgenic mouse model. Proc. Natl. Acad. Sci. U.S.A., 100: 4837–4842, 2003.

Robinson, R.G., and Bloom, F.E. Changes in Posterior Hypothalamic self-stimulation following experimental cerebral infarction in the rat. J. Comp. Psych. Physiol., 92(5): xx-xx, 1978.

Robinson, R.G., Shoemaker, W.J., Schlumpf, M., Valk, T., and Bloom, F.E. Effects of experimental cerebral infarction in rat brain: Catecholamines and behaviour. Nature, 255: 332–334, 1975.

Rogers, J., Siggins, G.R., Schulman, J.A., and Bloom, F.E. Physiological correlates of ethanol intoxication, tolerance, and dependence in rat cerebellar Purkinje cells. Brain Res., 196: 183–198, 1980.

Rogers, J., Silver, M.A., Shoemaker, W.J., and Bloom, F.E. Senescent changes in a neurobiological model system: Cerebellar Purkinje cell electrophysiology and correlative anatomy. Neurobiol. Aging, 1: 3–11, 1980.

Rogers, J., Wiener, S.G., and Bloom, F.E. Long-term ethanol administration methods for rats: Advantages of inhalation over intubation or liquid diets. Behav. Neural Biology, 27: 466–486, 1979.

Rogers, J., Zornetzer, S.F., and Bloom, F.E. Senescent pathology of cerebellum: Purkinje neurons and their parallel fiber afferents. Neurobiol. Aging, 2: 15–25, 1981.

Rossier, J., Bloom, F.E., Guillemin, R. Stimulation of human periaqueductal gray for pain relief increases immunoreactive β-endorphin in ventricular fluid. Science, 203: 279–281, 1979.

Rossier, J., Rogers, J., Shibasaki, T., Guillemin, R. and Bloom, F. Opioid peptides and alpha-MSH in genetically obese (ob/ob) mice during development. Proc. Natl. Acad. Sci., 76: 2077–2080, 1979.

Rossier, J., Vargo, T., Minick, S., Ling, N., Bloom, F. and Guillemin, R. Regional dissociation of β-endorphin and enkephalin contents in rat brain pituitary. Proc. Natl. Acad. Sci. U.S.A., 74(11): 5162–5165, 1977.

Ryabinin, A.E., Melia, K.R., Cole, M., Bloom, F.E., and Wilson, M.C. Alcohol selectively attenuates stress-induced c-fos expression in rat hippocampus J. Neurosci., 15: 721–730, 1995.

Schoepfle, G.M., and Bloom, F.E. Effects of cyanide and dinitrophenol on membrane properties of single nerve fibers. Am. J. Physiol., 197: 1131–1135, 1959.

Segal, David S., Browne, Ronald G., Bloom, Floyd, Ling, Nicholas, Guillemin, Roger. β-endorphin: Endogenous Opiate or Neuroleptic? Science, 198: 5411–414, 1977.

Segal, M., and Bloom, F.E. The action of norepinephrine in the rat hippocampus: I. Iontophoretic studies. Brain Res., 72: 79–97, 1974.

Segal, M., and Bloom, F.E. The action of norepinephrine in the rat hippocampus: II. Activation of the input pathway. Brain Res., 72: 99–114, 1974.

Segal, M., and Bloom, F.E. The action of norepinephrine in the rat hippocampus. III. Hippocampal cellular responses to locus coeruleus stimulation in the awake rat. Brain Res., 107: 499–511, 1976.

Segal, M., and Bloom, F.E. The action of norepinephrine in the rat hippocampus. IV. The effects of locus coeruleus stimulation on evoked hippocampal unit activity. Brain Res., 107: 513–525, 1976.

Shorr, S.S., and Bloom, F.E. Acino-insular cells in normal rat pancreas. Yale J. Biol. Med., 43: 47–49, 1970.

Shorr, S.S., and Bloom, F.E. Fine structure of islet-cell innervation in the pancreas of normal and alloxan-treated rat. Z. Zellforsch., 103: 12–25, 1970.

Siggins, G.R., Battenberg, E.F., Hoffer, B.J., Bloom, F.E., and Steiner, A.L. Noradrenergic stimulation of cyclic adenosine monophosphate in rat Purkinje neurons: An immuno-cytochemical study. Science, 179: 585–588, 1973.

Siggins, G.R., Hoffer, B.J., and Bloom, F.E. Cyclic 3’5’ adenosine monophosphate: possible mediator for the response of cerebellar Purkinje cells to microelectrophoresis of norepinephrine. Science, 165: 1018–1020, 1969.

Siggins, G.R., Hoffer, B.J., and Bloom, F.E. Studies on norepinephrine-containing afferents to Purkinje cells of rat cerebellum: III. Evidence for mediation of norepinephrine effects by cyclic 3,’5’-adenosine monophosphate. Brain Res., 25: 535–553, 1971.

Siggins, G.R., Hoffer, B.J., Oliver, A.P., and Bloom, F.E. Activation of a central noradrenergic projection to cerebellum. Nature, 233: 481–483, 1971.

Siggins, G.R., Oliver, A.P., Hoffer, B.J., and Bloom, F.E. Cyclic adenosine monophosphate and norepinephrine: Effects on transmembrane properties of cerebellar Purkinje cells. Science, 171: 192, 1971.

Stone, T.W., Taylor, D.A., and Bloom, F.E. Cyclic AMP and cyclic GMP may mediate opposite neuronal responses in the rat cerebral cortex. Science, 187: 845–847, 1975.

Sutcliffe, J.G., Milner, R.J., Bloom, F.E., and Lerner, R.A. Common 82-nucleotide sequence unique to brain mRNA. Proc. Natl. Acad. Sci. U.S.A., 79: 4942–4946, 1982.

Sutcliffe, J.G., Milner, R.J., Shinnick, T.M., and Bloom, F.E. Identifying the protein products of brain-specific genes with antibodies to chemically synthesized peptides. Cell, 33: 671–682, 1983.

Travis, G.H., Naus, C.G., Morrison, J.H., Bloom, F.E., and Sutcliffe, J.G. Subtractive cDNA cloning and analysis of primate neocortex mRNAs with regionallyheterogeneous distributions. Neuropharmacology, 26: 845–854, 1987.

Trembleau, A., and Bloom, F.E. Enhanced sensitivity for light and electron microscopic in situ hybridization with multiple simultaneous non-radioactive oligodeoxynucleotide probes. J. Hist. Cytochem., 43(8): 829–841, 1995.

Trembleau, A., Morales, M., and Bloom, F.E. Aggregation of vasopressin mRNA in a subset of axonal swellings of the median eminence and posterior pituitary: Light and electron microscopic evidence. J. Neurosci., 14: 39–53, 1994.

Van Orden, L.S., Bloom, F.E., Barrnett, R.J., and Giarman, N.J. Histochemical and functional relationships of catecholamines in adrenergic nerve endings: I. Participation of granular vesicles. J. Pharmacol., 154: 185–193, 1966.

Wedner, H.J., Hoffer, B.J., Battenberg, E., Steiner, A.L., Parker, C.W., and Bloom,

F.E. A method for detecting intracellular cyclic adenosine monophosphate by immunofluorescence. J. Histochem. Cytochem., 20(4): 293–295, 1972.

Weiss, F., Lorang, M.T., Bloom, F.E., and Koob, G.F. Oral alcohol self-administration stimulates dopamine release in the rat nucleus accumbens: Genetic and motivational determinants. J. Pharmacol. Exper. Therap., 267: 250–258, 1993.

Wu, C-C., Chawla, F., Games, D., Rydel, R.E., Freedman, S., Schenk, D., Young, W.G., Morrison, J.H., and Bloom, F.E. Selective vulnerability of dentate granule cells prior to amyloid deposition in PDAPP mice: Digital morphometric analyses. Proc. Natl. Acad. Sci. U.S.A., 101: 7141–7146, 2004.

Yang, T., Gallen, C.C., Schwartz, B., and Bloom, F.E. Noninvasive somatosensory homunculus mapping in humans by using a large array biomagnetometer. Proc. Natl. Acad. Sci. U.S.A., 90: 3098–3102, 1993.

Zieglgansberger, W., French, E.D., Siggins, G.R., and Bloom, F.E., Opioid peptides may excite hippocampal pyramidal neurons by inhibiting adjacent inhibitory interneurons. Science, 205: 415–417, 1979.

Reviews and Texts

Bloom, F.E. The Gains in Brain Are Mainly in the Stain. In The Neurosciences: Paths of Discovery. Worden, F.G, Swazey, J.P., and Adelman, G., Eds. MIT Press, Cambridge, 1975, pp. 211–227.

Bloom, F.E. The role of cyclic nucleotides in central synaptic function. Rev Physiol. Biochem. Pharmacol., 74:1–103, 1975.

Bloom, F.E. To spritz or not to spritz: The doubtful value of aimless iontophoresis. Life Sci., 14(10): 1819–1834, 1974.

Cooper, J.R., Bloom, F.E., and Roth, R.H. The Biochemical Basis of Neuropharmacology. Oxford University Press, Oxford, 8th Edition, 2003, p. 405.

Moore, R.Y., and Bloom, F.E. Central catecholamine neuron systems: Anatomy and physiology of the dopamine systems. Annu. Rev. Neurosci., 1: 129–169, 1978.

Moore, R.Y., and Bloom, F.E. Central catecholamine neuron systems: Anatomy and physiology of the norepinephrine and epinephrine systems. Annu. Rev. Neurosci., 2: 113–168, 1979.

Joaquín Fuster

BORN:

Barcelona, Spain

August 17, 1930

EDUCATION:

University of Barcelona, M.D. (1953)

University of Granada, Ph.D. (1967)

APPOINTMENTS:

Assistant and Associate Researcher, Anatomy and Psychiatry, University of California at Los Angeles (1960–1963)

Visiting Scientist, Max-Planck Institute, Munich, Germany (1962–1964)

Member, Brain Research Institute, UCLA (1961–present)

Member, Neuropsychiatric Institute, UCLA (1962–present)

Research Anatomist and Psychiatrist, UCLA (1963–1967)

Professor of Psychiatry, UCLA (1967–2002)

Professor Emeritus of Psychiatry (2002–present)

HONORS AND AWARDS (SELECTED):

Career Investigator Award, NIMH, 1960

Senior Scientist Award, NIMH, 1990

Ojemann Lecturer, University of Iowa, 1995

Member of Honor, Spanish Royal Academy of Medicine, 1997

Signoret Prize, University of Paris, 2000

Fyssen International Prize, Paris, 2000

Doctor “Honoris Causa,” University of Alicante, Spain (2004)

Goldman-Rakic Prize for Cognitive Neuroscience, NARSAD (2006)

George Miller Prize, Cognitive Neuroscience Society (2007)

Doctor “Honoris Causa,” Autonomous University of Madrid (2009)

Geschwind Lecturer, Harvard University (2009)

Woolsey Lecturer, University of Wisconsin (2010)

American Academy of Arts and Sciences (2010)

Segerfalk Lecturer, University of Lund, Sweden (2010)

Joaquín Fuster has devoted his research career to the cognitive neuroscience of the cerebral cortex. His principal contributions have been to the physiology of the frontal lobe in cognition. He was the first to discover “memory cells” in the prefrontal cortex, and later in the temporal and parietal cortices. These cells and their connections form cortical networks that, when activated, constitute the functional substrate of working memory, an executive function essential for goal-directed behavior, language, and reasoning. Studies of those networks in the well-defined experimental conditions of working memory are making it possible to characterize the organization of long-term memory and its dynamics in the perception/action cycle. These studies substantiate the new network paradigm of cortical memory that Fuster has proposed.

Joaquín Fuster

Barcelona

Everybody loves Barcelona, for its light, its architecture, its art, its food, and its people—Cervantes has Don Quixote call the town “the archive of courtesy.” Nestled in northeastern Spain between the Mediterranean and a low mountain range, the capital of Catalonia has been for centuries the main commercial and cultural gate to Spain, from land and sea. Catalan is a separate and distinctive language, now with a rich literature, which is closer to French than it is to Spanish; it derives from the vernacular Latin spoken by early merchants along the Via Augusta, the coastal route that linked Rome with Hispalis (Sevilla) and Gades (Cádiz) in the south of the Iberian Peninsula.

Barcelona is one of the most progressive European cities. The Spanish industrial revolution began there, notably with textile mills—as in England. With expanding industry and commerce, the end of the 19th century brought great wealth to the city, and an exceptionally enlightened and philanthropic bourgeoisie. With prosperity also came a large proletariat and periodic civil unrest, especially acute in recessions. Bakunin, the notorious Russian anarchist, made Barcelona one of his favorite venues. The Spanish Civil War (1936–1939), like other national cataclysms in Europe, was a direct result of the lingering Great Depression that began in Wall Street, not of ideologies, class wars, or nationalisms (Basque, Catalan, or other).

In wealthy Barcelona, all kinds of cultural institutions flourished: the University with its prestigious professional schools, the Music Conservatory, the Opera House (Teatro del Liceo), second to none in the world, the School of Fine Arts, literary assemblies of all sorts, and several technical schools. Pompeu Fabra, the foremost Catalan grammarian—my wife’s great-uncle— was an engineer; hence, his Catalan Dictionary is better for technical terms than the Dictionary of the Spanish Royal Academy of Language. Today there is a technological university named after him. All those institutions, coupled with the cosmopolitan cultural climate that a large harbor promotes, made Barcelona the permanent or temporary home for scores of famous artists, among them Ramón Casas, Pablo Picasso, Pau Casals, Salvador Dalí, and Joan Miró. The most distinguished Barcelonese of them all was undoubtedly Antoni Gaudí, the pioneer of modernist architecture, who greatly inspired Gropius, Le Corbusier, and Frank Lloyd Wright, among many others. Medicine was one of the thriving professions. The Medical School had always a prestigious faculty that trained many world-renowned medical scientists and physicians. Cajal was chairman of Histology in Barcelona for 5 years (1887–1892). According to himself (Cajal, 1923), there he made his most important scientific contributions, including the neuron theory.

I was conceived on the last month of the Roaring Twenties, on the year in which Barcelona hosted the World Exposition (1929). I have never attempted to associate the events surrounding my birth with the future course of my life—except for the fun of “what if.” The reality was, however, that after those events the world economy went downhill and Spain entered a long depression, followed by a terrible 3-year war and 40 years of dictatorship. These were hardly favorable conditions for a young man to enter a scientific career. In any case, it was written in the stars—or genes—that this one, the oldest of five siblings, would become a doctor, like others in the family.

Indeed, my family was steeped in medical tradition. I have lost count of the number of physicians in our last four generations—somewhere between 15 and 20, several in academia. Included in the list are my grandfathers, my father, my brother, and my son. My maternal grandfather, Professor Carulla, was a truly remarkable person. A man of humble origin who by humble jobs paid his way through pharmacy and medical schools at the University of Barcelona, of which, after a distinguished career as professor of medicine, he eventually became the Rector (president), and founder of the Medical School Hospital. Throughout his career he was consumed by a burning interest in education at all levels. Even while occupying the highest academic post in higher education, my mother told me, he would travel from village to village in the Pyrenees, sometimes on mule-back, inaugurating elementary schools (“here it all begins,” he used to say). For his accomplishments, the king Alfonse XIII made him marquis. They say he was slated to become Spain’s minister of education when he died, in 1923.

On that same year my father graduated from medical school (so did my father-in-law). After a brief stint in forensic medicine, my father decided to enter psychiatry. Following his training in that specialty, he served in several public mental-health institutions in Barcelona; eventually he would become the director of two of them in succession. After the Spanish Civil War, and a brief political clearance, for he had served in the medical corps of the army of the Republic (the losers), my father opened a small private psychiatric hospital in a large home that we rented in the outskirts of Barcelona. It was in the early 1940s and thus I was about to enter puberty. For reasons that had to do as much with economics as with quality control (my mother was a keen overseer of the business), our family lived with the patients, with whom we shared kitchen, dining table, and a sumptuous garden. It was a peculiar arrangement for us children, which for me lasted into late adolescence. I know another neuroscientist, Torsten Wiesel, who lived through an almost identical experience in his father’s psychiatric hospital up in Sweden. For my part, I have frequently told my psychiatric residents—tongue-in-cheek, of course— that I started my residency at an early age, and under a superb attending physician. . . .Indeed, my father, who in due time became university chairman, was widely reputed to be one of the best teachers of psychiatry in Spain.

Feelers from Tyrol

After medical school and more formal psychiatric training, my interests began to focus on the brain. I was in Innsbruck (Austria), undergoing some of that training, when the “brain bug” bit me hard. The bug piggybacked on my learning of English, which I was doing on the side to enlarge my knowledge of languages (I am more or less proficient in six). I became fond of practicing my new language reading issues of the Journal of Neurophysiology in the University of Innsbruck library. There I stumbled on the papers of H. W. Magoun and his colleagues on the reticular formation of the brain stem and its role in arousal. I was utterly fascinated by the subject and promptly discovered in my mind all kinds of psychiatric implications of it. With my poor English and zero experience with animal research, my understanding of the methodology was sadly deficient. I felt it was good enough, however, to pose a reasonable research question to H. W. Magoun, and even to dare asking for his tutelage to try to find the answer. Two excerpts of my correspondence with him illustrate my youthful impudence and naïveté, as well as his indulgence. I print them here because they undoubtedly constitute my first practical step into a research career.

Innsbruck, 8.6.1954

Dear Professor Magoun,

. . . . . .Quite convinced of the importance of the role of the brain stem reticular formations in the psychological and somatic manifestations in the circular mental diseases, I would be interested in undertaking some investigation work in order to study the function of those reticular formations in the maniac [sic] and melancolic [sic] states. Would it be possible, for instance, to measure with oscillography the latency, the speed and other characteristics of the EEG “arousal response” in both kinds of patients? . . .Could I work here [at UCLA] under your direction?. . .

Los Angeles, 9.9.1954

Dear Dr. Fuster:

The program of investigation under way in Los Angeles is almost completely. . .on the electrical activity of the brain of experimental animals. However, many aspects of the work are of interest for psychiatry. . .Should you be interested in devoting a year to this kind of activity, we should be happy to have you with us. . . . .

Very sincerely yours,

H. W. Magoun, Professor and Chairman

That was good news. I did not leave Austria, however, without attempting to do some preliminary research on mood and “reticular formations.” There is an old psychophysical test called the Klopftest or Tapping Test.

It measures the ability of an individual to maintain a rhythm by finger-tapping it on a table after having heard it from a metronome. I believe I reasoned that depressed patients would slow down the rhythm, whereas manic patients would accelerate it. This makes some sense by transposing to finger-tapping what patients of the two kinds do with psychomotor activities, including speech. Now, the reasoning with regard to arousal systems gets a little more tenuous. In any case, I proceeded with my low-cost project after having assembled what I thought was a reasonable sample of patients on the wards of the Innsbruck university hospital. Halfway through the testing, however, I learned for the first time that in research things do not always turn out as expected. On the patients I had examined until then, the anticipated correlation simply did not materialize, at least by using my pedestrian statistics, which I reckoned were sufficient for the purpose. I have never forgotten my shock when, at that point, my next test subject, a severely depressed patient, submitted himself to the procedure and, after hearing the standard rhythm, finger-tapped without the least deviation from that standard. He happened to be a member of the Zagreb Symphony Orchestra! That did it. Before redesigning the study, which I thought required at the very least the control of the musical education of each subject, I finished my fellowship and went back to Spain.

Del Amo Fellow to UCLA

Back in Barcelona, and encouraged by Magoun’s letter, my first priority was to find a fellowship to come to America. I found the perfect one: a Del Amo Fellowship. Don Gregorio Del Amo (1858–1941) was a physician from northern Spain (Santoña) who, after graduating from Madrid University, went to Uruguay, and later Mexico, to practice medicine. In 1887 he came to Los Angeles, where he ultimately settled and married the daughter of Domínguez, a wealthy Spanish “hacendado.” This gentleman owned the historical Rancho San Pedro (royal endowment from Charles IV), a huge property encompassing what is now occupied by several cities between the Los Angeles River and the Pacific Ocean, including most of current metropolitan Los Angeles. After becoming by inheritance the owner of the property, oil was discovered under it, in enormous quantities. Thus, Dr. Del Amo became a multimillionaire from the oil and land development revenues of the Del Amo Estate Company, which he founded. In 1906 he ceased to practice medicine to devote all his energies to business, which extended into banking (Union Bank). He also became a philanthropist, patron of the arts, and diplomat (General Consul of Spain in San Francisco). But never does a physician turned-something-else abandon completely his interest in medicine. Thus, Dr. Del Amo devoted much of his money to the advanced education of physicians. In 1929 (a year significant to me for another reason), he established the Del Amo Foundation in cooperation with the University of California at Los Angeles (UCLA), the University of Southern California (USC), and the University of Madrid. Its mission was to provide Spanish and Californian medical graduates with the means (fellowships) to carry out advanced studies as foreign visitors in those universities. In 1955, armed with Magoun’s letter, and after a couple of interviews in Madrid (with Jaime, the son of Dr. Del Amo, and a lawyer administrator of the Foundation), I was awarded a Del Amo Fellowship and travel money to the United States.

I crossed the Atlantic in the Conte Biancamano, a liner originally built in Scotland for the Italian Line, which during World War II had been seized by the U.S. Navy, converted into the SS Hermitage, and used for troop transport to European shores. One February day in 1956, 10 years after being stripped of guns and refurbished, the Conte Biancamano came to New York from Barcelona once more, this time with me on board. It was cold in the Great Apple, though not freezing as on the day before, during the boat’s stopover in Halifax, where none of the good Canadian whiskey could be had to warm up, for it happened to be Election Day in Nova Scotia. In New York I took a plane almost immediately for sunny California.

I was received at the old LAX airport by Tom Haley, a UCLA neuropharmacologist, who was a good friend of Spain, of the Del Amo’s, and of several other investigators in Magoun’s cohort, which spanned across several departments. Tom Sawyer, the well-known neuroendocrinologist, was now the Chairman of Anatomy, and my first boss at UCLA. Through his office and the Foreign Student Housing office I was procured living quarters at a 5-minute walk from campus: a room in the home of a German professor of geography who was well traveled and spoke good Spanish ($50/month with breakfast).

The Reticular Formation

Robert (“Bob”) B. Livingston, a professor of physiology originally from Yale (Fulton Laboratories) was my first scientific chaperon at UCLA. Bob was one of (“Tid”) Magoun’s collaborators in the discovery of the role of the brain-stem reticular formation in arousal. He procured me a lab in a temporary building (5F) near the recently constructed medical school and hospital complex. Assorted research and clinical facilities that for whatever reason did not fit in the new building were accommodated there. It was a curious place. Because years before 5F had served as the provisional Religious Conference Center of the university, it had a monastic structure, with a central quadrangular courtyard (“cloister”) surrounded by corridors and outlying rooms (“cells”). Now it housed a hodgepodge of university facilities, none of which nowadays would be probably approved by any conceivable accreditation board: the outpatient psychiatric department with the Psychiatry chairman’s office, an electronics shop, an animal vivarium with rodents, cats, and monkeys, a couple of psychoanalysts’ offices, a biochemistry lab, a steno pool, two neuropharmacology labs, a sociologist’s office, and a couple of small rooms near one of the entrances for this neophyte researcher from Spain.

In one of the two rooms assigned to me there was a Wisconsin General Test Apparatus (WGTA) for monkeys that two of Bob’s medical students had used for a behavioral study on visual discrimination, which eventually was designed to include neurophysiological research. It was supported by grants to H. W. Magoun, Bob Livingston, and Don Lindsley, professor of psychology, who was another member of the interdisciplinary Magoun’s cohort. When I came, the two students were busy with their classes and it seemed to me that the monkey-behavior part of the project was still poorly defined in anybody’s mind (I never read the grants). Anyway, the students were commissioned to teach me how to handle monkeys, which to that date I had only seen at zoos. They did that and also taught me the essentials of behavioral testing in the WGTA. Obviously catering to my interests and those of the group, I was being groomed for behavioral electrophysiology on monkeys, which no one else had yet done at UCLA. Now, more than a half century later, I still wonder how it had been possible that a young medical graduate with little more than good intentions, a few ethereal ideas, and a clinical nonresearch education was entrusted with that much responsibility— and given such a great opportunity. I think this would be now inconceivable anywhere. Perhaps my mentors were swayed by my “reticular enthusiasm,” my coming from the country of Cajal, or my psychiatric training; in the “monastery” (so was 5F referred to in jest), the department of psychiatry, my specialty, was situated down the corridor from my lab. Of course, there may have been several reasons why the psychiatric connection worked in my favor. One of them was political, or epistemological if you will. Norman Brill, the chairman of psychiatry, like most every other chairman of psychiatry in the country at that time, was a “devout” Freudian psychoanalyst. A few months before, Percival Bailey, the dean of American neurosurgery (and father of one of Magoun’s assistants), created a furor by lambasting psychoanalysis in front of the American Psychiatric Association. I suppose this young Spanish psychiatrist offered a little encroachment of the brain into psychiatry or a little “rapprochement” between brain science and psychiatry. It may have been both, for eventually Brill became my boss, and a good one at that.

The reality was that, in 1956, shortly after my arrival I had at my disposal a decent lab, a WGTA, an oscilloscope, a brain stimulator, and a bunch of monkeys. As to what to do with all that, and how to do it, it was left pretty much to my own wits. It seemed, however, that some kind of research on brain-stem reticular systems was expected from me, though it was left up to me to design it. (Of course, I had no trouble with that expectation!) Fortunately, in 5F, I encountered for the first time the key to academic success in the West: the spirit of “enlightened individualism” that David Starr Jordan, the first president of Stanford University, had brought to the West Coast at the beginning of the century and that, ever since, reigns in all the academic institutions of this coast, from Vancouver to the Mexican border. That spirit encourages you to do freely what you want without command or supervision if you do it well, and if you avail yourself to others for mutual help and to serve a worthy common cause. This deviates a little from the European–Eastern U.S. model.

Before I ventured into physiology with carte blanche and minimal but expandable infrastructure, I decided to develop a more sophisticated test than the visual discrimination tests customarily conducted with the WGTA. Those were too crude for any neurophysiological metrics. My objective was to stimulate the midbrain reticular formation and thereby to facilitate some kind of fine and difficult perceptual performance. The issue in my mind was the reticular “control” of attention. My reasoning went like this: if its arousal system were stimulated in the wake state, an animal would have that extra arousal to be more alert and to better perform difficult discriminations.

In my search for a suitable behavior, I turned to touch, more precisely active touch (haptics). With a saw, a hammer, and nails, I modified the WGTA for tactile discriminations. In my new paradigm, the experimental animal had to reach with one hand above and beyond a wooden partition into a plastic bag hanging out of sight on the other side of the partition, palpate geometric objects in it, and choose one for reward. Throughout the procedure the monkey and the tester could not see each other. Soon I was disappointed to realize that stereometric discriminations by touch were very difficult for monkeys to learn, much more so than visual ones. Eventually I would learn that auditory discriminations are even more difficult.

Then, one day, one particular subject started to perform haptics at 100% level, all of a sudden though a little more slowly than in previous days; the animal’s reaction time had gotten longer. Aha! I thought to myself, the learning curve is steeper than the books say, and the critical factor is “deliberation. . .”. Not quite trusting my reasoning, I installed a little strategic mirror that allowed me to see the monkey though he could not see me in the dark. Discovery: on every trial, before reaching, the animal peeped through a nail hole in the partition, a leftover from my remodeling of the apparatus. That way, he could visualize the position of the objects in the transparent bag before reaching into it. He was using vision after all! It was the second methodological failure of my scientific career (the first had been with the Croatian musician). There would be others, and I would learn something from each and every one. That one taught me that monkeys were a lot smarter than I thought.

A Tachistoscope for Monkeys

Everybody, including my monkeys, was telling me to use vision to study attention. Then I remembered having read in a psychology book, back in Spain, that the tachistoscope was an excellent instrument to test visual attention in the human. Could I build a tachistoscope for monkeys? It seemed a worthwhile challenge. But then, my monkeys were accustomed to visually discriminating pairs of objects presented simultaneously side by side on a tray in the WGTA. What if on every trial I cut the time of exposure of the objects to a fraction of a second, around the threshold for discrimination? I could make a tachistoscope out of the WGTA!

But there were a few problems. Obviously, I could not use a movable wood screen to limit the exposure; then also, how would I get the animal to compare two objects rapidly without shifts of gaze that would limit my control? I interposed a one-way screen between the monkey and the objects— and myself. Then the electronics technician in 5F built a light source (gas-filled tube) with length of illumination controllable down to the millisecond. I would illuminate the objects for a few milliseconds and let the animal choose the one on the right or on the left by sticking either hand through one of two trapdoors. I would make one of the objects the “correct” (rewarded) one and change the position of the two objects at random between right and left. After experimenting with several pairs of objects, I chose a couple of white objects that looked very much alike and served me well: a cone and a 12-sided pyramid of similar proportions (about 2 inches in height and 3 inches in base diameter). To the human observer, at minimal exposure (3–5 ms), the two objects looked identical, the pyramid exactly like the cone. I made of the cone the correct object for the monkey on every trial. As for the difficulty to visualize both objects simultaneously in a split-second, the monkey solved that for me: on hearing the warning sound before the flash lit the objects, he would look to the side of the screen where one of the objects was to appear. If it turned out to be the cone, he would launch his hand through the corresponding trapdoor and retrieve the morsel of apple under it. If it turned out to be the pyramid, he would reach with the other hand through the other trapdoor, inferring, correctly, that the cone was there with the piece of apple underneath. As expected, the trained animal made more errors as the exposure (flash) became shorter, and his reaction time became longer.

Five months after my arrival in UCLA, I had achieved my behavioral paradigm to test visual attention in the monkey. Now the goal was to stimulate the reticular formation during tachistoscopic performance. There was one serious environmental problem, however: noise, for my lab was not soundproof. Experiments on attention required complete silence or masking noise. I used the latter, but sometimes it did not suffice, because the corridor had a wooden floor and high heels were fashionable at that time with lady patients and secretaries. Thus, I conducted most of my experiments at night, on the weekend, or after-hours.

Electrodes had to be implanted in the brain, and I needed help to do it. I had never operated on animals and did not know how to use a stereotaxic instrument. No one was doing stereotaxic surgery on monkeys at UCLA. Fortunately, at the collegial request of Bob Livingston and Tom Haley, the Killams came to my rescue. Keith and Eve Killam were two neuropharmacologists of Magoun’s team who were doing drug research on reticular systems in “chronic” cats. They had extensive experience in stereotaxia with cats and rabbits. Not with monkeys. Yet, with the help of Olszewski’s monkey stereotaxic atlas, my first monkey was operated on in the Killams’ lab. Under Nembutal anesthesia, several bipolar electrodes were implanted straight down into the midbrain and anchored to the skull. I took plenty of notes, for the next monkey was to be done by me in my lab, though under Keith’s supervision.

Thus, finally I was ready to test my hypothesis. Would the electrical stimulation of the mesencephalic reticular formation make, as I predicted, my monkeys more alert, more attentive, to discriminate shapes briefly illuminated?

This time, after much toil, things seemed to turn out as predicted without major methodological problems. At long exposures, nothing happened; the animal had no problem discriminating the objects whether the electrical stimulus was on or off. At brief exposures (10–40 ms) under reticular stimulation, however, the animal made fewer errors and the electronic circuitry of the apparatus showed that its reaction time was shorter than without stimulation. In summary, the monkey saw better and reacted more quickly. That was my frequent observation with current intensity of 100–300 μA. Currents higher than that produced the contrary—disruptive—effects. Mild stimulation of other brain locations did not have the facilitating effect of the stimulated tegmentum of the mesencephalon.

Understandably, the data were welcome by my mentors but, as for anything apparently too good to be true, there were skeptics (“too much arousal,” somebody said incredulously; I thought the same thing myself). I endeavored to make sure the initial data were reliable, adding monkeys to the study and consulting with many experts at UCLA, especially psychologists and statisticians. I would not publish anything about the matter until I was convinced beyond a reasonable doubt. I did not reach that point until the summer of 1957, with half a dozen monkeys. Then I decided to publish a preliminary report.

At about that time, the Department of Psychiatry offered me a research position, which I readily accepted. Lindsley, from Psychology, sent me a graduate student, Art Uyeda, a Nisei American, to help me consolidate my study and gather more data. I taught him how to handle monkeys and how to use my tachistoscope. That was helpful, for soon I was to leave the country for a while with an important mission.

With things going my way, I left my lab in Art’s hands and went back to Barcelona to marry Elisabeth, my long-time girlfriend. Also, I would use the occasion to consult with my father before packing definitively for the States to continue my research career. He supported the plan, though at first reluctantly, because with it he was to lose his psychiatrist son, whom he had done so much to train. He was, however, an open-minded liberal man with great confidence in biological psychiatry and nothing but contempt for the meager state of basic science under Franco’s regime, even though clinical research and specialties, including psychiatry, continued to prosper in Barcelona, as they always had. Since Cajal, neuroscience’s forte in Spain was, of course, neuroanatomy. Before the war, there had also been outstanding Catalan physiologists (Pi i Sunyer, Folch i Pi, Duran-Reynals . . .), some working on the brain and establishing prestigious schools around themselves. After the war, however, Cajal had died and many of his disciples (Lorente de Nó, Del Río Hortega, Achúcarro, among others) had emigrated to the Americas, and so had the physiologists. My father considered carefully my circumstances and, finally, with his characteristic firmness and conviction said to me laconically: “Go!”

A less determined acquiescence came from the Del Amo family, whose fellowships assumed, if not required, one’s return to the home country to practice what he or she had learned abroad. My breach of expectation, if not contract, required upon my return to Los Angeles a lengthy explanation to Mr. Eugenio Cabrero, the secretary of the Foundation, who for the purpose invited me to lunch in the stodgy Athletic Club on 7th Street, near Union Bank—of which I believe the Del Amo family were majority owners at that time.

Debut in Science

At UCLA I was received with open arms, if nothing else because, despite my scientific immaturity, I was considered a kind of interdisciplinary bridge builder—and the only person potentially able to bring to fruition the monkey-behavior aspect of a Magoun-Livingston-Lindsley grant.

One year after my return, around the birth of our first child, Lisa, my first paper in Science (Fuster, 1958) was published: “Effects of Stimulation of Brain Stem on Tachistoscopic Performance.” No other publication, other than perhaps years later the report on the discovery of memory cells, had such an impact on the course of my career. It was the first demonstration, in the behaving monkey, of a psychophysical effect of brain stimulation. Eventually, with the coauthorship of Dr. Uyeda, the phenomenon would be published with the complete results on a total sample of 14 monkeys (those were the days!). That work opened my access to federal funding, which at one level or another, I have maintained to the present day. My first federal grant was a Career Investigator Grant of the National Institute of Mental Health. The agency liked to support young biologically oriented psychiatrists. My Science paper eventually became a classic and was cited in several texts of physiological psychology (e.g., by Morgan, and by Thompson).

Anyhow, the tachistoscope lent itself nicely to pharmacological studies on visual attention and perception. Magoun’s group included several neuropharmacologists to advise me on it. Because of the reported actions of lysergic acid on those functions in the human, and as an inducer of a model psychosis, I got a shipment of LSD-25 from Sandoz to test it on our monkeys performing the task. The substance produced deficits that were remarkable only for the minuteness of the doses necessary to produce them (single-digit microgram-range). Because the drug was a hallucinogen, Magoun arranged the visit to my lab by a famous LA resident writer, Aldous Huxley (The Doors of Perception). He came with his no less famous brother, Julian, who was visiting from the United Kingdom. I can still see the slim, tall, almost blind Aldous inspecting my monkeys at close range. All carried Spanish names of California places and towns: “Francisco,” “Diego,” “Jacinto,” . . . I was introducing them to him, one by one, when we came to a little fellow with a large conical cement implant with electrodes on his head. Aldous looked at him closely, with curiosity and, before my pronouncing his name, he said in his gentle manner and British accent: “This must be San Luis Obispo, I suppose. . .”

Shortly after that, in Basel (Switzerland), a Sandoz scientist jumped to his death into the Rhine; a fellow scientist had surreptitiously laced his coffee with LSD. That led to an enormous scandal and a lawsuit against Sandoz (even though Sandoz’s Hoffman, the discoverer of the drug’s effects, had used it on himself). Coming on top of the disclosure of illegal experiments by secret agencies on both sides of the Iron Curtain, that incident contributed decisively to the embargo of the drug even for research purposes. By the time of my LSD publication (Fuster, 1959), I had used on my monkeys probably one of the last shipments of the substance from Sandoz Basel to the United States.

My more important agenda, however, was to clarify the mechanism by which reticular activation facilitated vision. Where in the nervous system did that facilitation take place? Whereas Cajal and Granit had found some slim evidence of centrifugal fibers from the brain stem to the retina, there was no clear physiological evidence of centrifugal output to the retina; in any event, it seemed unlikely that my phenomenon was mediated at the periphery of the visual system. Because monkeys were already then expensive, I decided to conduct my study of the matter on rabbits.

My monkey research continued at 5F, but the rabbit research proceeded in T-67, another temporary building, this one on the grounds of the Brentwood VA Hospital one mile away from campus. T-67 was a long (100 ft) hemicylinder of corrugated metal on stilts, adjoined orthogonally in the middle by another, shorter, hemicylinder. The building, which structurally had little more than the metal shell and a wooden floor (again!), had served for the housing and care of wounded soldiers from the War of the Pacific. Now, in 1959, it was on loan from the VA to UCLA Anatomy. In the long section of the building there were four labs along a narrow side-corridor, and in the middle section (the stem of the “T”) a couple of rooms for animals (cats and rabbits). I shared the makeshift lab-suite with three other neuroscientists: Carmine Clemente, John Green, and Ross Adey. The animal facility was manned by “Smithy,” a jovial and efficient black Texan who was always in debt with all of us—albeit usually for modest amounts.

A Remote-Control Microdrive for Behavioral Neuroscience

In T-67, I dedicated myself to investigating in the rabbit the effects of electrical reticular stimulation on the responses of visual structures to optic stimuli. The question was, Where in the visual system did the reticular facilitation (“super-alertness”) work? My project was to approach the question in striate cortex and the lateral geniculate body, the two major components of the central visual system. I was to use microelectrode single-cell recording and evoked field-potential recording. The animal had to be awake and comfortable. That was accomplished by placing it in a soft restraining hammock, which I designed, and by prior stereotaxic surgery under general anesthesia (Professor Sawyer, in Anatomy, had developed an excellent stereotaxic atlas for the rabbit). The purpose of the surgery was to implant electrodes in the reticular formation and visual structures, and a pedestal for a microelectrode carrier.

I designed and constructed the microelectrode carrier with the help of a precision machinist who had a lathe in his private West LA garage. It was a hydraulic microdrive with remote control, unlike anything available on the market at that time. Mine was destined to be the first microelectrode drive to be used for cognitive neuroscience in the behaving monkey. But first I was to use it in the rabbit. Herbert Jasper in Canada, without the benefit of remote control, had been the first to record single-unit spikes from the brain of monkeys performing simple conditioned movements (Jasper et al., 1958). Eventually, in the monkey, my system would offer me the advantage of advancing the microelectrode from afar without disturbing the animal’s behavior with my presence.

The visual stimuli I used on my rabbits were far from ideal for testing the effects of attention on visual nerve cells. To assess visual neural responsiveness I used diffuse retinal illumination with light flashes. I was thus likely to miss any effect of attention on the reactions of cells to spatial contrast, so important for the assessment of visual attention. I did know, however, from the works of Hubel and Wiesel, in accord with the retinal works by Kuffler and Granit, that lateral geniculate and cortical cells with a central receptive-field response to “on” or “off” showed a comparable, though weaker temporal-contrast response to diffuse light-on or light-off. This response, I hoped, would be enough to reveal a cell’s center-field characteristics and thus be sufficient to assess the effects of alertness, if not attention, without necessity to control eye position and the receptive field responsiveness of each cell. It was an indirect way to assess effects of alertness on the cells’ physiology without characterizing their feature-response properties. It should work reasonably well to test the physiology of the tachistoscopic effect, which was essentially based on temporal contrast anyway.

Johnnie Green taught me how to make metal microelectrodes and how to record with them. The results of reticular stimulation on a sample of striate cortical cells were quite convincing: in almost one-third of them, trains of mild electrical stimulation of the reticular formation produced cell-firing changes that mimicked the effects of light. Thus, “light-on” cells were excited by reticular stimulation, whereas “light-off” cells were inhibited by that electrical stimulus. Furthermore, when the electrical stimulus was made to coincide with the light, the effects of the two reinforced each other. Those effects—mimicking and synergy—provided an apparent explanation for the facilitating effects of reticular stimulation on tachistoscopic perception in the monkey. The increased alertness from that kind of brain-stem stimulation enhanced the temporal contrast in primary visual cortex; temporal contrast was, after all, at the foundation of tachistoscopic acuity.

That work was the subject of my second paper in Science (Fuster, 1961), in which I also used the opportunity to present my microelectrode recording method. At about that time, my good friend Fernando Reinoso-Suárez, chairman of Anatomy in Granada (Spain), was visiting with me on sabbatical for a few months. Together we embarked on a side-project to investigate the cortical synchronizing effects of reticular lesions. In Spain, as in several European countries, physicians are granted their medical license at the termination of medical school. They are not granted their doctorate, however, until they complete a short curriculum of advanced studies, conduct thesis research, and defend it before a tribunal in a Spanish university. Since I had already taken my doctorate classes before leaving for the States, Professor Reinoso offered me the possibility of using the work published recently in Science as the thesis material, expanded and translated, and of defending it in Granada. Thus, I eventually obtained my Ph.D. in neuroscience.

The rabbit reticular-stimulation project on visual evoked potentials was conducted in collaboration with Richard Docter, a psychology postdoctoral fellow (Fuster and Docter, 1962). We employed three methods to manipulate the activation of the reticular formation of the brain stem: electrical stimulation or amphetamine to enhance it, and a barbiturate to depress it. We stimulated the visual system with strobe flashes and measured the amplitude of potentials evoked by them. Our most consistent finding was the arousal related changes in the amplitude of secondary (late, 150-300-ms latency) potentials in visual cortex. Similar potentials have been shown by other investigators to be enhanced in the human during visual attention. Likewise we found them parametrically enhanced by reticular activation and diminished by reticular depression.

It seemed thus quite clear that the facilitation of tachistoscopic acuity by stimulation of the mesencephalic reticular formation was exerted at the cortical level, not at the thalamic level or below. Only one other group of investigators, to my knowledge, had shown reticular influences on the visual physiology of the visual cortex. That was the group of Professor R. Jung and his colleagues in Freiburg, Germany. The influences they had demonstrated—in the cat—originated in the so-called thalamic diffuse reticular system, presumed to be the upward extension of the midbrain homonymous system. One of the members of that group was Otto Creutzfeldt, who was about to open a neurophysiology lab at the Max-Planck Institute for Psychiatry in Munich. In a short visit to UCLA in 1961, he and I got together and concluded that both could benefit from collaborating in his new lab. It appeared to me a splendid opportunity to acquire further expertise in visual physiology with a gifted pupil of Jung in a rich and brand-new setting.

Neuroscience Building Boom at UCLA

Indeed, at that time I felt I needed new lab quarters and further training in neurophysiology. Fortuitously, the Medical School and the Medical Center at UCLA were rapidly expanding, and neuroscience (the name did not yet exist) was undergoing a veritable explosion of new construction and facilities, particularly in all aspects related to mental health. There could not be a better place for a young research psychiatrist anywhere. At that time some of us benefited from a happy confluence of state and federal interests. The Department of Mental Hygiene of California, under Governor Edmund G. (“Pat”) Brown, was to greatly expand or build anew two neuropsychiatric institutes, one in San Francisco (Langley Porter, UC) and the other in the UCLA campus, attached to their respective medical centers. Our institute was to consist of two sections, one for patient care and the other for basic research of clinical interest (now called “translational”). At the same time, Magoun’s group was growing in size, productivity, and recognition. The group included investigators of several basic-science departments of the Medical School. They were attracting large amounts of money from the federal Public Health Service, especially the National Institute of Mental Health. And they were running out of research space in the new school.

After a series of high-level discussions and decisions involving the University and federal and state governments, of which I was never privy but could easily infer, the Brain Research Institute (BRI) was created, to be directed by Magoun, and the Neuropsychiatric Institute (NPI), to be directed by Brill. In effect, the NPI turned into the main quarters for the Department of Psychiatry, plus a mental hospital, with inpatient and outpatient facilities, and limited facilities for neurology and neurosurgery. The BRI, which had been originally conceived as the research part of the state’s NPI (with too few of us wagging its tail!), turned into a full-fledged neuroscience institute. Both would eventually consist of 10-floor adjacent towers annexed to the Medical Center. With the addition of the Reed Neurological Institute and the Stein Eye Institute, the entire UCLA medical complex would become the second largest building in the United States in floor surface (the Pentagon was the first). At the time of their creation, the University supported both institutes, NPI and BRI, with modest funding, mainly for faculty and staff. But the bulk of their funding came from the California Department of Mental Hygiene for the first and federal grants for the second.

Four of us, research psychiatrists, benefited substantially from the construction of the new buildings: Frederic Worden, Arnold Scheibel, Henry Lesse, and myself. The first two were to help me immensely with my academic and research careers at UCLA. Back in 1961, having become a member of the two departments, Psychiatry and Anatomy, and both institutes, NPI and BRI, the new buildings (I still have space in both), signified for me, a beginner in all relevant fields, a huge opportunity that I was ready to seize with zest. In the near future it signified an office in the NPI and a new monkey lab in the BRI.

The rabbit lab in T-67 was doomed anyway for another reason: the VA fire marshal came one day for a visit and, after declaring the building a “fire trap,” issued a preliminary eviction notice in advance of demolition. Since the BRI was not yet completed, the four of us UCLA “anatomists” with active projects in that place conferred to decide on the best delaying tactics to hold on to our labs until the BRI was available. I seem to remember that somebody remarked that the form from the fire marshal was printed in 1936, and someone else declared that the VA bureaucracy moved very slowly. We decided to stay put and watchful. A technician pinned a sign on the door of the vivarium: “SMITHY, if you see the wrecking ball coming, (1) pay all your debts, (2) let the animals loose on the field, and (3) run the hell out of here!” Two years later, when I came back from Germany, the building was still there and Smithy in hock.

Munich Max-Planck

Under the generous terms of the NIMH Career Investigator grant, the investigator was allowed to leave the home institution for a 1-year stay in another institution for advanced training. For me, that other institution was to be the Max-Planck Institute for Psychiatry in Munich. There I would join Otto Creutzfeldt in his new department of neurophysiology. Before leaving the States, however, I ensured my return. Then I found out that under the terms of a recent law, a foreign visiting scientist like me was required to spend 2 years abroad before being eligible to reenter the United States as an immigrant. The law was the response of the Eisenhower administration to the pleas by foreign governments to stem their brain drain to the United States. Fortunately, the law did not bar me from spending that time in other than my native Spain. The NIMH agreed to the extension of my allowed scholarly sojourn from 1 to 2 years, and the University to maintain for me both employment and research facilities during that time.

The Max-Planck Institut für Psychiatrie was a famous historical institution. Situated in Schwabing (in the Kraepelinstrasse, 2), a northern suburb of Munich, it had been built in 1928 to house the research institute founded by Kraepelin in 1917 and to accommodate the scientific facilities of the Nervenklinik of the University of Munich. A long series of prestigious luminaries of the nervous system and psychiatry had worked there: Alzheimer, Nissl, Brodmann, Bumke, among others. After the war, the institute had become one of the Max-Plancks.

When I arrived there, in the fall of 1962, Creutzfeldt was launching a visual neurophysiology program on cats and rabbits. I joined his group, which comprised Dieter Lux, Albert Herz, and Max Straschill, in a series of studies of the visual system designed to clarify the information processing characteristics of its neurons and their susceptibility to changes in arousal level. For me, it was an ideal setting for further training and for pursuing my interests. In cats, we probed the major stations of visual processing: the optic tract (retinal ganglion-cell axons), the lateral geniculate body, and the striate cortex. Two kinds of measurements were our major dependent variables in the three structures: spike frequency and interspike intervals (ISIs). The observations were made under three conditions: spontaneous unit discharge at rest, unit response to brief or sustained visual stimuli, and manipulation of arousal level pharmacologically.

On average, spontaneous discharge slowed down as we ascended the visual system with our microelectrodes. Units fired the fastest in the optic nerve, slower in the geniculate, and slower yet in striate cortex (Fuster et al., 1965a). Those units showed brisk optic responses in the optic tract and weak in striate cortex, with the geniculate cells somewhere in between. In other words, as we went up the visual system, the cells seemed progressively less responsive to external stimuli, and possibly required more specific stimulation in terms of the visual features that we were not testing. The most relevant finding (Herz et al., 1964) was the pervasive presence of interspike interval (ISI) distributions that in the normal resting state approached randomness (Poisson with a minimum interval and exponential decay). Brief visual stimuli induced sharp increases of firing frequency, within which the ISIs still conformed to random—Poisson—distribution but with shorter average intervals. Sleep and drowsiness, whether natural or drug induced, led to phasic activity and reactivity, with ISI distributions containing several modes and prolongation of average intervals. These findings were in accord with the general proposition that in sensory systems information processing is accomplished by changes in neuronal firing frequency, not by changes in spike pattern (that is, by nonrandomly firing units).

In the visual system of rabbits we were able to obtain, for the first time, intracellular records from brain neurons in the wake state or light anesthesia (Fuster et al., 1965b). That allowed us to characterize membrane potentials in those neurons at rest as well as in response to visual stimuli. We showed, also for the first time, that the magnitude of light-evoked membrane potentials (excitatory EPSPs as well as inhibitory IPSPs), in relation to light intensity, conformed well to a logarithmic function, and better yet to a power function. Thus, Stevens’ psychophysical power function appeared to describe reasonably well that relationship in visual-neuron synaptic potentials of the rabbit—though the exponent of the function differed somewhat from that observed in human psychophysical experiments.

Back to UCLA: “Limbic Arousal” in Perception

An immigrant with permanent resident status, with wife and two children, I came back to the States in October of 1964. All was well at UCLA. Art Uyeda had taken good care of the monkey lab and was completing the tachistoscopic project. With the new buildings constructed, that lab was now moved to the BRI and my office to the NPI. The rabbits in T-67 were to enter a new study, this one on limbic influences on the visual system.

In the mid-1950s, before he moved to Michigan and later Caltech, the Chicagoan psychologist James Olds stirred considerable interest at UCLA— where he spent 2 years—with his self-stimulation phenomenon: He had discovered (Olds and Milner, 1954) that rats liked to press switches to deliver, through implanted electrodes, current into their limbic structures, notably the hypothalamus and the amygdala. Olds and his group liked to talk about “pleasure centers” in those structures. Among the psychologists interested in self-stimulation were Professor Seward and his graduate student Art Uyeda, who did his thesis research on the reward value of self-stimulation using behaviorist methods. It was Art, later still working with me, who got interested in possible inputs from limbic structures into sensory systems. The issue made a lot of sense to us for two reasons in particular: (a) it is an undisputable fact that emotions alter perception, and (b) there was at that time growing evidence that some limbic structures, especially the amygdala, were involved in the evaluation of the motivational significance of sensory stimuli. Art was to help me strengthen that evidence in the monkey. But first, I wanted to approach the question of “limbic arousal” in a more affordable species than the monkey.

Together with Germán Sierra-Marcuño, a young visiting professor from the University of Santiago de Compostela (Spain), we endeavored to investigate in the rabbit the effects of electrical stimulation of limbic locations on the amplitude of visual evoked potentials (Sierra and Fuster, 1968). The most remarkable finding was an augmentation of the secondary—late— potentials in primary visual cortex by electrical stimulation of the amygdala.

These were the same potentials enhanced by stimulation of the reticular formation of the brain stem. Assuming that the effect reflected increased visual attention, it made sense that input from the amygdala, presumably related to motivation, should increase the cortical manifestation of visual attention.

Also with Sierra we explored in cats and rabbits the psychophysical function of visual potentials: amplitude as a function of light intensity (Fuster and Sierra, 1968). Here again, as in our microelectrode study at the Max-Planck, we found visual response related to light intensity by a power function. The exponent (steepness of curve), however, was quite low, in both lateral geniculate and visual cortex.

In the 1960s, little was known about the behavioral physiology of the amygdala in the monkey other than the effects of lesions of that limbic structure. Most striking among those effects was the so-called Klüver-Bucy syndrome (Klüver and Bucy, 1938), the peculiar behavior of animals that had undergone ablation of the temporal lobe, including the amydgdala in its core. Such animals appeared deprived of emotional feeling, hypersexual, and hyperphagic, prone to eat nonedible objects indiscriminately. From that, it was commonly assumed that the amygdala played a role in the biological value of objects and stimuli. We should expect, we thought, that the neurons in the normal amygdala would react to sensory stimuli that connoted some kind of biological motive. Here is where Art’s help would be decisive, among other things because of his strong interest to run limbic experiments on issues of reward and motivation. And now we had the means to drive microelectrodes into deep structures like the amygdala in behaving animals.

We trained monkeys to discriminate between visual stimuli associated with appetitive and aversive consequences: To the monkey, four rows of parallel horizontal lights meant (preceded) food reward; four columns of parallel vertical lights meant (preceded) irregularly a mild electric shock to the feet. Concomitant recording revealed the validity of our prediction. We found cells responsive to the visual stimuli in the amygdala, the hippocampus, and the piriform cortex. Cells responding differentially to the stimuli (“food” vs. “shock”) were particularly common in the amydgada. Indeed, in the basolateral amygdala many cells seemed attuned to the motivational significance of the stimuli (Fuster and Uyeda, 1971). In later years, the motivational role of the amygdala would become a big subject among researchers of emotional response in rodents and in human imaging. To my regret, few now cite our work with Art Uyeda (deceased), surely the first demonstration of the involvement of limbic units in emotional behavior. Happily, Joe LeDoux is one of those few.

Psychoanalysis

Another of the intellectual perks of the Career Investigator Award under the National Institute of Mental Health was the payment of tuition for psychoanalytic training. There were several socio-cultural-scientific reasons for this. In the early 1960s psychoanalysis permeated the zeitgeist of academia, Hollywood, and the press. It was considered a central part of the medical and psychological armamentarium to treat mental illness. It was also a lucrative profession practiced in and out of medical schools by an elite corps of European exiles, some of them disciples of Freud. Because most chairmanships in U.S. departments of psychiatry were psychoanalysts, many of them made psychoanalytic training de rigueur in the postgraduate education of psychiatrists. Besides and behind it all was a deep-seated desire on the part of the psychiatric community to legitimize psychoanalysis as a scientific discipline, thus defeating Popper’s dictum that it could never be such a discipline because it cannot be proven wrong.

Logically, psychoanalytic scholars were looking at brain scientists for help. It was against that background that NIMH decided it would be a good idea to train brain scientists in psychoanalysis. Coming from European psychiatric schools, however, where psychoanalysis never really caught on (my own father was decidedly a biological psychiatrist), I did not think much of that discipline. At the same time, I was fascinated with psychiatric phenomenology and with the writings of Karl Jaspers, though not so much by those of Sigmund Freud, who could also be considered a phenomenologist. In time, however, I began to see the intellectual merit in undergoing psychoanalytic training myself.

Thus, given the intellectual and financial opportunity I had (psychoanalytic training was very expensive), I presented myself to the Los Angeles Institute for Psychoanalysis, in Beverly Hills. I told its director, the late Ralph Greenson, that I wished to be admitted to his Institute. Of course, he would not grant my desire without prior scrutiny and consultation. He asked me right away for my motives. I told him that I was genuinely interested in that approach to the human mind. Besides, as a psychiatrist slated some day to train psychiatric residents at UCLA, I could not do without the lingua franca (not my term to him) of psychiatric discourse in my institution. Finally, I told him that, though I was a monkey neurophysiologist, I was truly hoping to find brain correlates of psychoanalytic constructs, and if in the process I found some personal psychic benefit, so much the better. I was not planning to become a full-fledged practicing psychoanalyst.

A few days later, Greenson invited me to his office. The Institute had admitted me for 3 years of formal training. Its admissions board had assigning to me, as personal analyst, one of the very best of their faculty, Hanna Fenichel, the widow of Otto Fenichel, himself Freud’s disciple who had written a classic on obsessive neurosis. Perhaps in that connection, the good humored Greenson asked me, “as one condition for admission,” to which I agreed, that one day I would come back to the Institute and reveal to its members the location of the superego in the brain.

Unquestionably, they delivered on their part of the bargain, and I learned a lot I did not know about myself (though some friends claimed it did not do me any apparent good). I did not deliver on my part of the bargain, however, though sometimes I think the superego cannot be too far from the frontal lobe.

The Frontal Lobe

In all honesty, my research on the frontal lobe, which was to practically fill my scientific life for at least four decades, had a scientifically dubious origin. It grew out of a technical achievement, not of the need to resolve a particular research problem—though it ended up doing just that, and more than one. With the help of Larry Ott, an engineer at Hughes Aircraft, I developed thermoelectric cooling probes that could be implanted on the cortical surface of monkeys to induce reversible inactivation or depression of the subjacent cortex. Thermoelectric pairs were then being used by NASA to cool down electronic parts with a tendency to heat up when operating in outer space. I suppose my probes were an example of the much-touted spin-off of space technology into biomedical research. They operated on the Peltier principle, that is, the temperature gradient created by passing electrical (DC) current through adjacent dissimilar metals. If we applied the cold side over the cortex and dissipated the heat at the other side into the atmosphere or running water, we could in effect establish a heat pump to cool the cortex.

Reversible lesions: wonderful! That would put in our hands the functional knockout power of ablation without its imponderable but very real drawbacks, such as secondary degeneration of cells and fibers away from the ablation site, irritation around the edges of the lesion, surrogate takeover of the abolished function by other structures, and so on. More than anything else, the cortical cooling not only would obviate those problems but also would afford the ultimate desideratum for the behavioral neuropsychologist: the ability to use an animal repeatedly as its own normal control. To be sure, as we soon found out, there were limitations to cooling also: sharp temperature gradients in the brain away from the probe, protracted inhibition after the cooling, and the danger of permanent lesion if temperature accidentally reached 0°C. These were some of the reasons why eventually we rarely cooled cortex below 10°C (controlled by subdural thermistors). At that temperature, cortical function could hardly be blocked but simply depressed. That would be useful enough.

In the entire neuropsychological literature on animal cognition, the deficit that monkeys show in short-term memory after frontal ablations is far and away the most consistent and predictable of all experimental deficits (Jacobsen, 1935). Is it a wonder that we should focus on it to test our cooling method? The advantage of reversibility could not be dismissed. Besides, the lateral cortex of the frontal lobe was readily accessible to our cooling probes.

It seemed that we should be able to turn that cortex “off and on” and, thus, short-term memory “off and on.” Traditionally, before anyone was concerned with the brain mechanisms of memory consolidation, the delayedresponse task and its variants were the time-honored tools to test short-term memory in the primate. And the delay-task deficit from frontal lesion was for many years almost Exhibit #1 of Physiological Psychology 101.

With time, of course, the operational definition of short-term memory by delay-task performance, and the unique frontal-lobe involvement in it, appeared increasingly simplistic. That kind of “operant,” “online,” “provisional,” or “temporary” short-term memory was eventually identified by cognitive psychologists as “working memory,” and the frontal lobe was subdivided into a variety of “modules” for functions other than, and in addition to, working memory. But at that time, in the late 1960s, the tempting opportunity to test frontal cooling on such a pristine task as delayed response was irresistible. Again, the experiment was not undertaken to test the validity of the classical finding of Jacobsen, but to test the usefulness of a functional cryogenic method for the behavioral neurophysiology of the monkey. For me, however, it turned out to be my entry into the mysteries of the frontal lobe. It opened my interest into that brain structure that is not the causal source, but certainly the cerebral enabler, of such lofty human faculties as language, creativity, and liberty.

At first, the issue was the role of the lateral prefrontal cortex in memory. With my first graduate student, Gary Alexander, we implanted a few monkeys with cooling probes on the frontal lobes and set out to test, this time reversibly, the Jacobsen effect. The result was nothing short of astonishing (Fuster and Alexander, 1970). The bilateral lowering of frontal temperature to 25°C—after all, no lower than ambient temperature—produced a consistent and reversible deficit in the classical delayed-response task. Under cooling, the monkey showed no overt sign of sensory or motor deficit and could perform the task without any problem if the delay, that is, the memory period, was short. When we prolonged the delay to 5 s or more, however, the monkey made more errors of performance than at normal temperature; and the deficit increased with the length of the delay.

Indeed, frontal cryogenic depression seemed to make the animals forget the cue or memorandum, which in that task was a spatial one. The lateral prefrontal cortex was clearly implicated in some kind of short-term memory. Later, with Dick Bauer, a postdoctoral psychologist from Montana, we proved that the dorsolateral prefrontal deficit from cooling could be obtained on a nonspatial (delayed matching-to-sample) as well as on the typical spatial delayed-response task (Bauer and Fuster, 1976). In due time, with Germán Sierra, Jr. we would show a prefrontal cooling deficit on auditory delayed response (Sierra-Paredes and Fuster, 2002).

It took some time before cognitive scientists experimenting with humans, notably Baddeley, in the 1980s would identify as “working memory” the kind of short-term memory tested by delay tasks in our monkeys (Baddeley, 1983). The capital difference between working memory and the short-term memory that is conventionally considered the gateway to long-term memory before consolidation, is that the former is memory utilized for a prospective action. This attribute is the reason why the prefrontal (“executive”) cortex is so important for it.

An Interlude with Woodpeckers

One day the late Phil May, a fellow psychiatrist in the UCLA faculty, came to me and blurted out a strange question: “Joaquín, why don’t woodpeckers have headaches?” For a moment I was taken aback, but knowing Phil’s British sense of humor and sharp intellect, I quickly regained my footing and after some laughter began to appreciate the seriousness of the question. “Phil, I don’t know, but I’m sure they don’t have headaches; otherwise they wouldn’t do all that hammering. It should be fun to find out how their brain is protected from all the shaking and smacking.” Then and there began one of the most fun projects of my research career: to study the structure and mechanical properties of the woodpecker’s brain and cranial vault.

Our first hurdle was funding, as usual. Everybody in the university found our inquiry amusing, original, and worthwhile, but there appeared to be no local resources for it. Federal money was a possibility. But then Congressman Dingell was already having his own fun scrutinizing government grants for trivial research. Furthermore, there was a protected-species issue. A letter of intent directed to the Navy to solicit help—to go on a Navy ship to Nicaragua in search of specimens—was summarily dismissed, presumably on the suspicion of boondoggle.

Eventually, we found a local source of specimens. Dr. Howell, a senior professor of zoology at UCLA, had a few woodpeckers in formalin that he was willing to donate for our project. A histology lab lent its services for a small recharge. On the whole, the overhead cost turned out to be quite modest and we decided to conduct most of the research on weekends. The results were remarkable in many respects. Before entering the skull of the little critter, we found the most bizarre structure of a tongue, the long thin muscular appendix by which the bird explores the depth of the boreholes it drills in trees searching for tiny insects. The tongue was inserted in the bone around the right nostril and wrapped in a dual coil of split branches around the ears; then its two branches rejoined into one that penetrated the floor of the mouth from underneath the jaw, and its extremity was snugly fit inside the mouth along the beak. We learned what some ornithologists had known for a long time, but we didn’t. By uncoiling and sliding over the skull, the tongue could be projected forward to an extraordinary length beyond the beak. Clearly the coiling and uncoiling of the tongue was an ingenious marvel of nature: a highly efficient method to store and use the long tongue. And, upon its contraction, to project it far and fast forward to dig into the wood.

The anatomy of the bird’s head had certain features that we thought of enormous mechanical importance for protecting the brain from injury:

(1) tight “packing,” with no empty or fluid-filled spaces of any significance (consultation with a postmaster confirmed that it could not be otherwise for maximum protection of the skull’s content from damage); (2) spongy bone at the base of the bill, to act on every impact as a shock absorber; (3) an internal crest of bone along the skull’s midline, between the two hemispheres—that bony crest, together with the bone on both sides of the skull, was to divert the lines of force away from the brain. Those structural features allowed us to speculate on the ideal structure of helmets to protect soldiers or motorists from frontal impact. With it all, we thought we had enough material for publication in a medical journal. Phil picked it: The Lancet, the premier medical journal in the United Kingdom. There, appeared our pride and joy, a paper entitled “Woodpeckers and Head Injury” (May et al., 1976). The editor and reviewers had been happy to accept it with minor revision, complete with a picture of a cross-section of the woodpecker’s head and a military helmet from the British Infantry in World War I. As can be imagined, our article generated an enormous amount of publicity worldwide. Eric Sevareid, in NBC’s Evening News, announced—in jest—the imminent probability that the government would implement new regulations on the making of helmets for motorists based on our findings in the woodpecker.

The dynamic aspects of woodpecker action were as interesting as the morphological ones. Their study, however, demanded high-speed photography and live birds in action. After contacting Walt Disney Studios, who were in possession of considerable footage of woodpecker hammering for their famous character, we decided to go on our own. We did so especially because commercial film clips, taken at 24 frames/s, did not lend themselves easily to digital analysis of the bird’s pecking at an impact velocity of 600–700 cm/s and deceleration nearly 1000 g!

Somehow we were addressed to a ranger in Placerita Canyon Park who had a pet woodpecker, uncaged, hammering away on a tree trunk in his office. The rattle of typewriter keys was sufficient to get the little critter pounding vigorously. With the ranger’s permission and the help of an expert cameraman, we took lots of high-speed film footage (2000 frames/s). By digital analysis of the film scans, frame by frame, we were able to reconstruct the action in computational terms. The most remarkable finding was that the bird hit the wood by rapid movements of the head, back and forth, with the beak always orthogonal to the surface of the wood, without any head rotation. This linear motion undoubtedly required an exquisite coordination of neck muscles, but it avoided whiplash and protected the brain from the kind of shearing forces that play havoc in the brains of boxers and motorists (May et al., 1979).

Working Memory: Memory Cells

Whereas my colleagues and I had managed to reversibly reproduce and better define the Jacobsen effect on delay tasks, we had made little progress in understanding the precise form of short-term memory disrupted by prefrontal lesion. As I said before, it was the research by cognitive psychologists experimenting on humans that defined it as working memory. In any case, nothing was known about the physiology behind that kind of memory or, for that matter, about the physiology of the prefrontal cortex. Clearly the data from lesions demanded the microelectrode study of that cortical region in animals performing working-memory tasks. To me, the most elementary questions were: What are the neurons of the prefrontal cortex doing while the animal performs one of those tasks? Could they possibly provide any indication that they engage in retaining the memorandum?

In the late 1960s, when I first dropped a microelectrode in the monkey’s frontal lobe, I felt like a paratrooper landing at night in no-man’s-land, where danger could come from all sides. Indeed, it was intellectually daring to venture with a microelectrode in “that part of the brain, the size of a fist, which nobody knew anything about”—in the words of a prominent neuroscientist of the time with a slight Canadian accent (David Hubel). I admit I was driven by a simplistic hypothesis in the midst of a fog of ignorance.

But then, expectedly, I struck gold—or so it seemed to me—and the hypothesis proved far from silly (Fuster and Alexander, 1971). I will never forget when I found the first cells that acted like “memory cells” (I had them so labeled for myself even before I found them!). Their distinctive feature was the sustained elevated discharge during the delay, the memory period of a delay task, while the animal had to retain the memorandum (Fig. 2.1). In my initial enthusiasm, however, I ignored the possibility that those cells might be encoding things other than the memorandum. In due time, we would learn from our work and that of many others—especially Japanese investigators, such as Niki and Watanabe—that my memory cells could encode other aspects of the task, such as the impending motor response, the expected reward at trial’s end, and the context in which the animal performed its task. We would learn with time that those cells I first discovered in prefrontal cortex were component elements of widely distributed cortical networks that encoded all the associated features of the delay task, a given cell attuned to one feature more than to others. I am now persuaded by the available evidence that those cells are indeed memory cells, but the memory they encode in their ensembles is not only the memory of the memorandum but also the memory of all that the animal has associated in the learning the task to test it.

With Gary Alexander (Fuster and Alexander, 1971), we found memory cells also in the nucleus medialis dorsalis of the thalamus, with which the prefrontal cortex is reciprocally and closely connected. This led to the reasonable hypothesis, which became the basis of Gary’s dissertation, that the memory cells of the prefrontal cortex, together with those of its thalamic projection nucleus, were part of the same short-term memory system. Based on that assumption, we were able to show that prefrontal cooling, in addition to impairing delayed response, led to a blunting of delay-cell activity in the nucleus, a suggestion of a working memory reverberating “loop” between prefrontal cortex and thalamus (Alexander and Fuster, 1973). As our exploration of cortical working memory expanded, I was to become increasingly convinced of the existence of such loops between prefrontal and other cortices. Gary, later at Hopkins, would empirically proposed similar loops through basal ganglia in motor programming (Alexander et al., 1992).

Fig. 2.1    Firing of a prefrontal cell during five delayed-response trials (test of spatial working memory). A horizontal bar marks the cue—memorandum—period, and an arrow the end of the delay (memory period) and the response of the animal. Note the persistent activation of the cell during working memory. From Fuster and Alexander (1971).

In the late 1980s, Pat Goldman-Rakic and her colleagues at Yale (Funahashi et al., 1989), after identifying prefrontal memory cells in a visuospatial delay task and performing elegant parametric studies with them, did much to publicly establish working memory as the primary function of memory cells. She was the most persuasive neuroscientist attributing to these cells the function that Baddeley had first described in the human (Baddeley, 1983).

Contributing from the beginning to my interest in the possible existence of working-memory cells in other cortices was the recognition that the memory activity of many prefrontal cells, while attuned to certain memoranda (e.g., right, left, red, green), was not specifically tuned to them nearly as much as it would be expected from sensory cells (Fuster, 1973; Fuster et al., 1982). Some were evidently tuned, regardless of memorandum, to executive and reward-related features of the task that were common to every trial in it (Quintana et al., 1988; Yajeya et al., 1988). It is true that these were especially concentrated in certain prefrontal domains: executive and working-memory cells in lateral cortex, reward cells in orbital cortex (Rosenkilde et al. 1981). But the apparently weak tuning of lateral prefrontal memory cells to the cue, which changed from trial to trial, led me to reason in this manner: Could it be that the memory of that cue was actually elsewhere, near sensory cortex and perhaps under prefrontal control, whereas prefrontal cells encoded mainly the memory of executive and reward-related features of the task? Given that in our experiments we were using visual memoranda such as colors, an obvious target for our microelectrodes was the inferotemporal (IT) cortex, a part of the posterior association cortex that lesion studies had shown to be important for visual discrimination and memory. Also its cooling, like that of lateral prefrontal cortex, was shown to induce a reversible deficit in visual delayed matching to sample for colors (Fuster et al., 1981), a visual working-memory task. Later, with Wes Ashford, another graduate student of mine (and psychiatric resident), we would substantiate by field-potential recording the inflow of visual information from visual to IT cortex (Ashford and Fuster, 1985).

As predicted, IT cells were much better at “remembering” colors than prefrontal cells (Fuster and Jervey, 1981, 1982). To be sure, the majority of IT cells did not respond to the sample cue in the color memory task, but many of those that did showed color-specific memory activity during the delay (Fig. 2.2). Evidently, these IT memory cells participated in neuronal ensembles, or networks, that received visual input and, at the same time, retained that input for as long as necessary in accord with the rule of the learned task. It did not appear far-fetched that those networks reached the prefrontal cortex, where they connected with executive and reward networks. It was also reasonable to think that, in turn, the prefrontal cortex reciprocated with some kind of top-down control to ensure in IT cortex the maintenance of attention on, or working memory of, the color of the cue or sample.

The soundness of the last couple of inferences was confirmed by cooling IT cortex and recording from prefrontal cortex, and vice versa, in the course of visual memory-task performance. We were able to correlate the predicted deficits in delayed matching to sample, from cooling either cortex, with the diminished memory discharge of cells in the other cortex (Fuster et al., 1985). Beyond that, the implied cortico–cortical interactions contributed to the network paradigm of cortical memory that was beginning to take shape in my mind.

In any case, my discovery of, and research on, memory cells in association cortices were the most stimulating incentives for writing my two books, The Prefrontal Cortex (1980) and Memory in the Cerebral Cortex (1995). Both these works are attempts to incorporate my novel findings in comprehensive reviews of established knowledge. The first, now in its foutth edition, has become a universal reference on the prefrontal cortex (Fuster, 2008).

Fig. 2.2    Firing of an inferotemporal (IT) cell during delayed matching-to-sample trials with color (test of visual working memory). The memorandum or sample is a color—red or green—appearing briefly on a central display disk at trial’s start. The animal has to retain that color through the delay or memory period, at the end of which the two colors—red and green—appear and the animal has to choose the sample color that started the trial. Though the sample color changes randomly from trial to trial, the cell’s activity rasters have been grouped in the upper figure by sample color. R: red sample; G: green sample. The frequency histograms in the lower figure average the cell’s firing separately during eight red- and green-sample trials. Note higher cell activity during red memory—and rapid return to baseline discharge despite second foveation of red color for choice (i.e., after working memory is no longer needed). From Fuster and Jervey (1982).

Haptics

In the 1970s and 1980s, the U.S. Navy was very much interested in retrieving the wreckage of the Titanic (which Ballard found in 1985 with Navy support). For that and other reasons, the Office of Naval Research (ONR) supported several university research projects bearing on robotics and artificial intelligence. Because at that time I was working with my monkeys on haptics (active touch or palpation, an essential component of robotics in submarine exploration), they were much more generous to me than they had been for the woodpecker project.

I came into haptics from two avenues. One was my search for memory cells in sensory cortices: haptic memory was as plausible in somatosensory cortex as visual memory was in IT cortex. The other avenue was more theoretical and, as it turned out, closely related to prefrontal function: the idea was growing in me that all cortices serve the broad and basic biological principle of the perception/action (PA) cycle, by which we adapt to the world that surrounds us. In goal-directed behavior, as in spoken dialogue, an external stimulus leads to an action, and that action engenders new stimuli, which in turn lead to new action, and so on. In the dialogue, of course, the environmental stimuli come from the interlocutor. That continuous cybernetic cycling of information through the brain and the environment is the essence of the PA cycle, which governs all goal-directed sequences of behavior, language, and reasoning. Haptic working memory is a means of closing the cycle at the top of the cortical hierarchy (somatosensory/prefrontal), whenever there are temporal discontinuities in the cognition and recognition of tactile information in the course of haptics. Here the “interlocutor” is the physical world of environmental objects.

Eventually, with two undergraduates, Waleed Shindy and Keith Posley, we would be able to show a reversible deficit of haptic working memory by cooling prefrontal cortex (Shindy et al., 1994); cooling parietal cortex would not result in a similar deficit presumably because somatosensory cortex lies mostly in the depth of the central sulcus and out of the reach of our surface cooling probes. However, with two postgraduates from Spain, Xavier Quintana and Javier Yajeya, we were able to induce changes in prefrontal unit activity in delayed response from cooling the same parietal cortex (Quintana et al., 1989).

All along before and during those cooling experiments, however, we made progress in our exploration of haptic memory in the somatosensory cortex by means of microelectrode recording. Another graduate student, Kevin Koch, found haptic memory cells in that cortex (Koch and Fuster, 1989). The most remarkable finding was that some of those cells were situated in the primary sensory cortex, emphasizing the fact that essentially haptics is a sensory-motor activity, in which the executive and somatosensory aspects of it are inextricable from one another. The microelectrode exploration of that cortex in monkeys discriminating and remembering objects by palpation culminated with my collaboration with graduate student and postdoctoral fellow Yong-Di Zhou, presently director of the Institute for Cognitive Neuroscience in East China University (Shanghai).

Something of general importance came out of my studies with Yong-Di, which was to impact my thinking about the network nature of cortical memory. Whereas John Maunsell (Maunsell et al., 1991) had found units in visual cortex that responded to the visual and tactile features of objects, we found them in tactile cortex (Zhou and Fuster, 1997, 2000). Clearly these cells associated vision with touch. They seemed to belong to broad neuronal networks that reached into visual and somatosensory cortices and associated sensory features cross-modally. We had observed similar cells in prefrontal cortex, these associating the spatial and optic features of visual stimuli used in memory tasks (Fuster et al., 1982), and then later, again in prefrontal cortex, cells that associated sounds with colors in a cross-modal memory task (Fuster et al., 2000).

The supramodal role of prefrontal networks had been previously supported in cross-modal cooling experiments. Having achieved the not easy task of training monkeys to discriminate objects by touch (without cheating as in 5F!) and to perform haptic memory tasks (DiMattia et al., 1990), we had been able to show deficits in these tasks by cooling lateral prefrontal cortex (Shindy et al., 1994). Especially noteworthy for us, in that it reinforced the cross-modal character of the prefrontal cortex, was the evidence of deficits induced by cooling this cortex on visuohaptic and haptic-visual working-memory tasks, where the animal had to memorize an object perceived by touch and recognize it by vision, or vice versa.

A Paradigm Shift in Cortical Memory

The cross-modal effects of prefrontal cooling, and the evidence of cross-modal cells in parietal and temporal cortex, among other findings, were slowly but surely leading me away from the conventional thinking of sensory physiologists about the role of the cortex in perception. Up until practically the end of the century, most of them were heavily influenced by the modular organization of visual cortex. Beyond this cortex, they thought, modules probably got bigger and specialized in ever more complex optic features. In the mind of some, hierarchical complexity meant that in higher cortex there would be some integrative neurons (“grandmother cells”) that would put all the sensory features of a percept together. No one really believed in that absurdity, but many endeavored to develop modular models of cognition, more or less parallel and more or less hierarchical, down to the computational and neuronal levels, all of them based on the sensory properties of visual stimuli. None of them, that I knew, dealt with neuronal integration of behaviorally associated stimulus properties.

In the 20th century the word network appeared often in the neuroscience literature on cortical cognition, but rarely with formal definition in neuronal terms. “Neural network” was an expression coming from information theory and artificial intelligence that penetrated the field of cognition in multiple attempts to model the dynamic connectivity of brain structures. But the concept of cognitive network (cognit, my expression) for representation of memory and knowledge in the cortex never quite entered cognitive neuroscience. The conspicuous absence of practically any network concept of cognition in the large compendium of The New Cognitive Neurosciences by Gazzaniga (2000) prompted my sharp critique of that book (Fuster, 2000), which I am sure did not make me many friends.

Actually, however, the general idea of cortical cognitive network had been proposed long ago by some brain theoreticians with regard to one cognitive function or another (Edelman and Montcastle, 1978; Mesulam, 1981; Bressler, 1995). The first proponent, and undoubtedly the most influential on my thinking, was Hayek, a famous economist (Nobel Prize 1974) who in his youth (1920s), while a student of psychology in Vienna, had written an insightful essay about perception that was to be published much later under the title of The Sensory Order (Hayek, 1952). In that essay Hayek prophetically envisioned the network concept of perception. Perception, according to him, consisted of the workings of a memory-constituted apparatus of dispersed but interconnected cortical neurons classifying the world as we sense it on the basis of prior experience. Memory and perception were inseparable in all respects (as Helmholtz had previously held). The key neural structures for both functions were assemblies of intersecting memory “maps” with common nodes. These “maps” (his unfortunate word for isomorphic networks without any relation to the well-known retinotopic maps) were formed by associative learning through facilitation of synaptic contacts by temporally coincident input stimuli. Hayek’s specific concept of the synaptic basis of learning and memory was akin to one of Hebb’s principles (Hebb, 1949). But his original cortical network concept of memory and perception anticipated by many years the use of methods for axon staining, the demonstration of the rich network-like connectivity of the primate cortex, and the identification of fiber tracts by functional imaging.

Four fundamental lines of evidence from our research led me to the conceptualization of a new reticular memory paradigm in the cortex based on Hayek’s concepts, a paradigm that at least in my mind was to supersede the modular paradigm that was a commonly held legacy of the 20th century. One line of evidence was the observation that the areas of the primate cortex with working-memory cells of a given sensory modality were, to judge from the effects of their lesion, known to be involved in long-term memory of the same modality. In the human, injuries of their homologous areas cause agnosias, amnesias, and discrimination deficits of the same modality. From there, the idea emerged that working memory is essentially a fragment of long-term memory updated for present usage.

The second line of evidence was that in practically any part of association cortex, including prefrontal, memory cells could be found that were attuned to several stimuli, whatever their modality, that had been associated by the animal in the learning of a working-memory task. What’s more, we had gathered evidence that the learning of a memory task was correlated with increased responsiveness of cells to its associated stimuli. These findings were most striking in our cross-modal memory experiments (Zhou and Fuster, 2000; Fuster et al., 2000; Zhou et al., 2007).

The third line of evidence derived from our study of the cellular mechanisms of working memory. Cell firing patterns in association cortex showed replicates and periodicities that were consistent with the concept of network reverberation as one of those mechanisms (Villa and Fuster, 1993; Zipser et al., 1993; Bodner et al., 1998, 2005; Verduzco-Flores et al., 2009).

The fourth line of evidence came out of our imaging studies. By means of positron emission tomography (PET) with neurologist Barbara Swartz and others, we were able to ascertain the joint cortical activation of large prefrontal and visual areas in humans performing a visual working-memory task (Swartz et al., 1995). Presently, with graduate student Allen Ardestani we are investigating the dynamic coherence in cortical networks of monkeys performing such tasks. We use an integrative methodology that includes the recording of multiple-unit discharge, local field potentials (LFPs), surface field potentials (SFPs), and near-infrared spectroscopy (NIRS). The recording of the last of these signals is a method for assessment of changes in cerebral blood-flow secondary to neuronal activity, a method that is relatively novel for the monkey (Fuster et al., 2005), and possesses high temporal resolution.

In my view, the emerging paradigm of cortical memory, which I first proposed in 1995 (Fuster, 1995; Fuster, 1997) and later in Cortex and Mind (Fuster, 2003) is receiving increasing support from the latest findings by innumerable investigations of working memory using the latest techniques of neuroimaging and electrocortical computation. I summarize that support in a recent review article (Fuster, 2009).

Central to the new reticular paradigm of memory is the concept of the cognit: a neural unit of knowledge or memory consisting in a cortical network of widely distributed neuronal assemblies. That network is formed, expanded, and modified by learning or experience. The component assemblies may consist of smaller networks representing discrete sensory or motor items of information in sensory or motor cortical modules. Cognits are formed by the temporal coincidence of sensory or motor inputs to those assemblies. In accord with the Hayek-Hebb principle (“cells that fire together wire together”), the representational assemblies or “netlets” concomitantly activated are united by synaptic modulation into larger associative networks that represent the composite of the simultaneous stimuli or inputs. A newly constituted cognit will be thereafter activated in its totality by activation of only one or a few of its component assemblies. Furthermore, two or more components of different cognits, when coinciding in time, will lead to the association of those cognits into higher and more abstract or complex cognits. Those will share common nodes of connectivity and representation.

We have known for a long time, as a result of studies of neuropsychology in patients with temporal-lobe injury (Squire, 1987), that for memory to form and consolidate in the neocortex, the hippocampus and probably other limbic structures need to intervene functionally. The synaptic mechanisms by with this occurs, however, are still poorly understood. Certain excitatory neurotransmitters, such as NMDA, are supposed to play a role in the underlying neural transactions. Whether electrical phenomena such as long-term potentiation also play a role remains a matter of debate. In sum, cognitive networks or cognits vary greatly in size and distribution, some of them straddling noncontinuous areas of the cortex. The cognitive code they represent is essentially a relational code, in which the information is defined exclusively by the relationships between component cognits or assemblies of neurons. It is a code irreducible to its parts, much as the code identifying visual percepts in Gestalt psychology. The idiosyncrasy of our knowledge and memory thus derives from the practically infinite combinatorial power of our 10 to 20 billion cortical neurons. Because of the heavy intersection and overlap of cognitive networks, one neuron or group of neurons practically anywhere in the cortex can be part of many memories or items of knowledge. The cortical networks constituting cognits are hierarchically organized, from the simplest and most concrete in sensory or motor cortices to the most complex and most abstract in the higher association cortices. Perceptual cognits are principally organized in posterior cortex, whereas executive cognits are principally organized in frontal cortex. All cognitive functions (attention, perception, memory, language, and intelligence) are based on neural transactions within and between cognits. There are powerful reciprocal connections between posterior and frontal cortices for the dynamic interactions between the two cognitive hierarchies in the perception/action (PA) cycle, which is the neural substrate for the organization of behavior, language, and inductive reasoning.

Memory of the Future

This is undoubtedly the most awkward oxymoron for the title of the last part of an autobiography. I have two quick explanations for it. First, the expression best characterizes the position of my favorite brain structure, the prefrontal cortex, in evolution and in the temporal organization of adaptive behavior. Secondly, the expression is at the crux of my current interests in the neurobiology of liberty and free will.

Once in 1984, my Swedish friend, the late David Ingvar, asked me to edit an issue of his journal, Human Neurobiology, to be dedicated in its entirety to the prefrontal cortex. I undertook my task with a great deal of interest, anticipating his contribution in particular, for he was a pioneer in the neuroimaging of the prefrontal cortex. That contribution did not take long to reach my hands. To my astonishment its title was “Memory of the Future.” I demurred. Indeed, it took me a while before I understood the paper and accepted it, as I eventually did pretty much as it was and with that title (Ingvar, 1985). It turned out that Ingvar had been the first to demonstrate the activation of the human prefrontal cortex during the ideation of plans of action and language. He saw in the human the prospective memory that I was still missing in my monkeys and in their memory cells.

After a couple of decades I have come to appreciate the wisdom of David’s expression perhaps even more than he himself did. For, much as in evolution, the prefrontal cortex “invents the future” based on the past. Executive memory is literally memory of action to adapt to the future. Evolution, with the prefrontal cortex in its vanguard, is the manifestation of the PA cycle at the population level. In both the individual organism and the population, that cycle uses the memory of the past to adapt both the organism and the population to their environment. The brain intervenes in the former, the genes in the latter.

Our freedom consists not only in our capacity to choose between alternative actions but also in our capacity to choose between alternative sources of past information to plan and guide those actions. The prefrontal cortex, at the apex of the PA cycle, enables both, the choice of information and the choice of future action. Just as the species carries in its genes the information it has acquired to adapt to its environment, the prefrontal cortex has at its disposal an enormous reservoir of acquired perceptual and executive memory to adapt to that environment. Moreover, in what is a veritable quantum change in evolution, the human brain has acquired two basic and characteristic capabilities, both in large part the purview of the prefrontal cortex: language and the capacity to predict. Both are intimately related with each other and allow us to preadapt, not only as individuals but also as a society. Both serve the memory of the future. Societal memory is the root of institutions, laws, and ethics. In all those personal and public endeavors our individual prefrontal cortex is the supreme enabler: enabler of what is already in the brain, in the form of either past or prospective memory or imagination. Most certainly, the prefrontal cortex is not the implicit “homuncular CEO” of some current accounts, a conceptual fallacy resulting from modular thinking that inevitably leads to an infinite regress.

Only the future provides meaning to our autobiography. I shall thus close this account of mine with a brief future perspective. Next week, I am supposed to deliver the annual Segerfalk Lecture at the University of Lund, where David Ingvar spent his last professional years. The lecture will be on the frontal lobe; I could not think of a better title for it than “Memory of the Future.” To the distant future, Elisabeth, my dear wife of 52 years, and I have made two significant contributions. One is a happy family with three children and six grandchildren. The other is a private legacy to the University of California. In recognition of the unstinting support I have received throughout my scientific career from this great institution, we have endowed it with a chair in Cognitive Neuroscience. The first holder of the Fuster Chair is Professor Susan Bookheimer, a renowned expert in brain imaging and a superb educator.

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Michael S. Gazzaniga

BORN:

Los Angeles, California

December 12, 1939

EDUCATION:

Dartmouth College, A.B. (1961)

California Institute of Technology, Ph.D. (1964/1965)

APPOINTMENTS:

Assistant/Associate Professor, Psychology; Chairman, Psychology; University of California, Santa Barbara (1967–1969)

Associate/Full Professor, Psychology; NYU (1969–1973)

Professor, Psychology; SUNY, Stony Brook (1973–1978)

Director, Division of Cognitive Neuroscience; Professor of Neurology and Psychology; Cornell University Medical College, NY (1978–1988)

Andrew W. Thomson, Jr. Professor of Psychiatry; Director, Program in Cognitive Neuroscience; Dartmouth Medical School (1988–1992)

Director, Center for Neuroscience; Professor of Neurology and of Psychology; University of California, Davis (1992–1996)

David T. McLaughlin Distinguished Professor; Director, Center for Cognitive Neuroscience; Dartmouth College (1996–2002)

Dean of the Faculty; Dartmouth College (2002–2004)

David T. McLaughlin Distinguished University Professor; Dartmouth College (2004–2006)

Director, SAGE Center for the Study of Mind; University of California, Santa Barbara (2006–present)

HONORS AND AWARDS:

Fellow of the Society of Experimental Psychologists (1982)

American Academy of Arts and Science (1997)

Ariens Kappers Medal for Neuroscience (The Royal Netherlands Academy of Arts and Science, 1999)

Institute of Medicine (2005)

Distinguished Scientific Contribution Award, American Psychological Association (2008)

Alexander von Humboldt Award, Germany (2008)

The Gifford Lectures, University of Edinburgh (2009)

Charles L. Branch Award, University of Texas, Dallas (2010)

Michael S. Gazzaniga carried out original studies of human brain laterality and function in split-brain patients, work that has rich implications for consciousness, free will, and the self. He introduced the term cognitive neuroscience, helped develop the discipline, and founded the discipline’s flagship journal. More recently, he has effectively written several books for a broad audience about brain and mind, showing generations of readers the human face of science.

Michael S. Gazzaniga

There is a foie gras served at a hideaway of a restaurant in Edinburgh that is sublime. I had had a double Scotch to celebrate completing my first of six Gifford Lectures and was beginning to feel normal again. Lectures always exhaust me, and I really don’t particularly want to see anybody at their conclusion. This night was different, however. Somehow the University knows about these matters and leaves you alone with your family to recap and savor the experience and honor, and to taste that magnificent city. As my wife, my daughter, and my sister assured me I had not made a fool of myself, we all soothed each other and submerged ourselves in what we all love the best: ideas, food, and drink—all with a twinkle in the eye.

I cannot separate my scientific life from my personal and nonscientific associations. Even though they are utterly different aspects of my time, each arena has helped sustain the other. While I like my evening cocktails, I prefer talking about ideas rather than what is on the sports page that day. This predilection has led my wife, Charlotte, and me into giving endless dinner parties over the years that have become a major part of our intellectual life. That impulse has served us well. My wife and I have had a grand life getting to know the minds of others.

Presenting the Gifford Lectures in 2009 was an enormous undertaking and over the course of 2 years of preparation, I discovered it was the mix of all of my friends, academics and nonacademics alike, that have colored my penultimate views on mind and brain issues. I came to realize how much we humans are the product of the entire milieu within which we live. A retrospective account of one’s scientific contributions, as if all things linearly developed from a single logical framework, is just plain wrong, at least for me. In what follows, I will attempt to talk not only about the scientific work accomplished but also the social and personal setting in which they occurred. I have had the privilege of knowing several great scientists and public personalities, and they all have influenced me in profound ways. As they say, if you play tennis, don’t play with a poor player. It brings your game down. I haven’t.

The Caltech Years

Let me roll the camera back to my graduate days at Caltech. After a challenging 4 years at Dartmouth College, little did I know that my social life at Dartmouth would become a more noteworthy achievement at that time than anything I ever accomplished academically. I was a member of the much fabled Animal House and played out my days as “Giraffe.” Actually, I was the nerd of the fraternity, preferring to spend more of my time working in the laboratory of the psychologist William B. Smith than drinking in the Alpha Delta Phi House basement. Smith had a passion for research and he had built a small lab on the top floor of McNutt Hall where we developed methods to measure eye movements. We worked together long into the night. Research was all new and exciting for me, and the first glimpse of the mystery of trying to figure out a mystery of Mother Nature became very real and compelling. While some of my dearest friends came from the Animal House, it also served to motivate one to do other things.

During the spring of my junior year I found myself reading a Scientific American paper by Roger Sperry on the mechanisms of neuronal specificity. It was a beautiful story, beautifully written, leading me to an idea. Caltech was close to my childhood home as it was to the home of the girl of my dreams who went to Wellesley. Maybe I could get a summer fellowship at Caltech and work on the problem of neural specificity, and see my girlfriend frequently. To shorten a long story, the job worked out, but the girlfriend didn’t.

That was the beginning of my love affair with Caltech. It all started by being surrounded by an institution and a faculty that projected high expectations. After 50 years, I remain convinced Caltech is the finest scientific institution in the world. When I was there, Linus Pauling was down the hall. Seymour Benzer joined the Sperry lab and his office was across from mine. We talked all the time. Richard Feynman had a way of popping into graduate student offices and asking them what they were doing. And of course my own mentor Roger Sperry was the most insightful and engaging of all. We talked for a couple of hours each day that summer and for my entire subsequent five graduate education years. It was a special relationship at the time.

When that glorious summer was over, I was not trained in developmental neurobiology, as I had expected, but rather in the beginnings of what was called psychobiology. The Sperry lab continued to do work on neural development, but its major focus was on split-brain animal work. During that summer I contributed to the enterprise by developing a method for reversibly anesthetizing half of a rabbit brain. I was hooked.

Inspired by the excitement of the ongoing animal research on split-brain cats and monkeys, I returned to Dartmouth College determined to go to back to graduate school at Caltech. I couldn’t help but become captivated by the question of what would happen to humans with callosal sections. During my senior year at Dartmouth I had the idea to try to retest a famous group of patients from Rochester New York who had had their callosum sectioned in the early 1940s in an attempt to limit their epileptic seizures to one half brain. The Akaelaitis’s patients seemed like the perfect opportunity to confirm the animal work. So during my spring break I arranged to visit them through the offices of Dr. Frank Smith , who at the time of the surgeries had been a resident.

I designed many experiments and exchanged letters with Sperry about the ideas and the plan. I applied to the Mary Hitchcock Foundation at Dartmouth Medical School and received a small grant to rent a car and to pay for my stay in Rochester. In the end I didn’t get to see the Rochester patients, even though my car was loaded with borrowed tachistoscopes from the Dartmouth psychology department. The effort to reveal the effects of callosal disconnection in humans would come later.

My decision to go to graduate school and to forego medical school was accepted by my father, but he was never thrilled with the idea. He was a remarkable surgeon and one of the founders of the first prepaid medical plan in American, the Ross-Loos Medical Group in Los Angeles. He was utterly devoted to the medical profession and genuinely thought it was the finest and only way on earth to spend one’s life. In the end he was pleased as one of my brothers and one of my sisters became physicians. The next question, of course, was would I get into Caltech. If one reads the qualifications for entrance, any normal person’s assumption would be that he or she had better make other plans. Somehow it worked out, in large part I am sure to being sponsored by Sperry.

As soon as I arrived, for my first day of graduate work, Sperry gave me my assignment. The split-brain experiments I had designed during my senior year at Dartmouth would finally be implemented, but on Caltech patients rather than Rochester patients. Soon enough, I was in the thick of an exciting and consuming project. That was 50 years ago. Before I knew it I was examining a robust and charming man, WJ, who was about to undergo cerebral commissurotomy, the so-called split-brain surgery, to control his otherwise capricious epilepsy. He was the sort of level-headed person to instill respect in a young, green, graduate student like myself.

Dr. Joseph E. Bogen was also there, a resident at the time, and the person who had critically reviewed the medical literature and was convinced that split-brain surgery would have beneficial effects. He enlisted Dr. P. J. Vogel, a professor of neurosurgery at the Los Angeles–based Loma Linda Medical School, who performed the surgery. My chore was to quantify the psychological and neurological changes, if any, in the way WJ behaved once the connections between his hemispheres had been sectioned.

The conventional wisdom suggested that nothing would happen. Andrew Akelaitis, 20 years earlier, had found that callosal section in human subjects produced no behavioral or cognitive effects. Karl Lashley had seized on this finding to push his idea of mass action and “equipotentiality” of the cerebral cortex; discrete circuits of the brain were not important, he claimed—only cortical mass. After all, he concluded, cutting the massive nerve bundle that connected the two halves of the brain appeared to have no effect on interhemispheric transfer of information.

The electrifying beginnings of the human work might have been predicted by dozens of experiments on animals. Study after study had shown that corpus callosum section profoundly altered brain function in cats, monkeys, and chimpanzees. Specifically, information presented to one brain hemisphere remained isolated in that hemisphere. It was as if dividing the great cerebral commissure produced an animal with two minds, neither of which was aware of the workings of the other. Ronald E. Myers and Sperry had already coined the term “split-brain” to describe such animals. Yet the idea that callosal section would produce a similar condition in humans seemed bizarre.

Preoperatively, WJ could name stimuli presented to either visual field or placed in either hand. With his eyes closed, he could understand any command and carry it out with either hand—in short, he was entirely normal. The stage was set ideally to investigate what would happen following the disconnection of his cerebral hemispheres. The scientific context and the time were right for us to ask the right questions: Could it be that a disconnected right hemisphere was as conscious as a disconnected left hemisphere? Could it be that a state of co-consciousness could be produced in a human being? Where would positive answers to either or both of those enquiries lead us?

When WJ returned for testing after surgery, I experienced one of those pivotal moments in life. First, and to no one’s surprise, the subject named and described normally stimuli that were presented to his left hemisphere. Then came the critical test: what would happen when information was flashed to his verbally silent and physically isolated right hemisphere? Akelaitis’s work predicted that the subject would describe the stimulus normally, because his studies suggested that the corpus callosum played no essential role in the interhemispheric integration of cerebral information. On the other hand, the animal work suggested that something interesting might emerge. As it happened, something interesting did emerge: the idea that splitting the human brain produced two separate conscious systems (Gazzaniga et al., 1962). It was a revolutionary idea, and 50 years later it is one that still needs study and clarification. The context for the work was established by my thesis (1965), which in turn was composed of a set of papers (Gazzaniga et al., 1963, 1965, 1967).

It is curious that, despite centuries of study and speculation about consciousness, there is no general agreement even about what the term means. If you asked 20 students of the problem to finish the sentence, “Consciousness is. . .,” 20 different definitions would result. Still, most of us would agree that the term refers to that subjective state we all possess when awake and to our feelings about our mental capacities and functions. As is typical with vast and ill-defined concepts, it is easy to offer simple examples of what it means to be conscious, but, at the same time, lifetimes of inquiry will not divulge the entirety of its nature.

My time at Caltech was unforgettable and enduring. My daily conversations and good times with Roger Sperry were priceless at both a scientific and personal level. It is because of that that his abandoning me once I left Caltech was especially difficult on me. As Mitch Glickstein was to observe recently, Sperry had a hard time sharing credit with his former students (Glickstein and Berlucchi, 2010). What can you do? There is no doubt in my mind he was the greatest brain scientist to ever live.

I still do research on these special patients and talk and write about the research all the time (Gazzaniga, 2000, 2005). While split-brain research has been a dominant influence on my life, it has not been the only influence. The reason is that I am a dreamer. I am always thinking about other things. My mind wanders. At my core, I suppose, I am hopelessly restless.

I assume the value in an effort such as writing this article for the autobiographical volumes is to expose students to the many ways one experiences a life in science. For me, the excitement and wonder of scientific discovery is indescribable. You have to go there and do it. It not only gives meaning to one’s own life, it gives meaning when reading about the discoveries of others and what they must have felt at the moment when, bingo, an insight is confirmed with hard experimental fact. In my case, this happened early in my career. What it did for me was clear the way to appreciate the life of the mind and mostly the minds of others. As a consequence of my early good fortune, I was never frantic to prove myself. Sheer luck played into a fast beginning, and I felt empowered to cultivate my general restlessness and venture into a wide range of issues. Of course, the other liberating reality was that split-brain research was thrilling when I began it and remains so today. There never is the sense of drudgery that can sometimes occur when something becomes routine. When you know your day job is rich and exciting, one can explore more one’s secondary interests.

As a consequence, I liked examining other social questions as well as scientific questions bubbling up from the new human studies and wanted to explore them in animal models. It seemed so natural, being surrounded by an active primate research laboratory. Sperry was approving, as he was a comparative biologist as much as anyone could be. It almost was expected of you to come at problems from a variety of approaches. I dove into animal research as well from the very beginning.

Animal Research

After my stint with rabbits as I described earlier, my first extended efforts were in trying to understand something about the neural mechanisms of a relatively simple sensory motor act, accurately reaching for an object. My colleague Colywn Trevarthen had cleverly invented a way to determine which hemisphere a split-brain monkey was attending through when solving a dual-task discrimination. I went after a simpler question. How does the left hemisphere control the left arm and hand following split-brain surgery? After all, hemisphere disconnection disrupted the flow of information from the sensory process of the left hemisphere to the motor systems of the right hemisphere, the hemisphere that had dominant control of the left hand. This issue arose immediately in our human split-brain work. Working with primates I could pursue it more aggressively (Gazzaniga, 1964).

The entire Sperry lab was contributing to the building of better and better automated behavioral testing devices for the rhesus monkey. We all had slightly different ideas on how to make them better. Trevarthen liked to transport the monkey from the room where it was kept into his own testing box/apparatus. I preferred to build a unit that could be attached to the back of the monkey’s home cage and to arrange that the discrimananda were presented automatically, sort of out the back door of the monkey cage. I built an elaborate automatic data recording system, a closed circuit TV for watching and all the rest.

Sometimes we had to resort to using monkey restraining chairs, while at other times we could test the animals in a large cage where we were able to limit sensory input to one eye or the other by using contact lenses. It was under these conditions I was able to spot a major mechanism used by monkeys to cross-integrate information from one hemisphere to the other following their split-brain surgery. Again, the question became, how does the left or right brain guide and control its ipsilateral hand? Sensory-motor information was easily integrated when both the sensory information and the motor information were being processed in the same hemisphere. But following split-brain surgery, how did the sensory information from one hemisphere get together with the motor mechanisms of the other?

It all became evident in the open cage testing. With one eye—say, the left eye—occluded by our opaque contact lens, the right eye and therefore the right hemisphere alone was seeing, as all the animals also had their optic chiasm split down the middle. I would hold up a tantalizing grape on the end of a stick and let the animal reach out for the grape and grab it with his right hand. The left hand was restricted in various ways. I also filmed the event using slow-motion photography.

It was in the films that it all became evident what was happening. The animal would get set and then stare at the food with the seeing eye. Because the sensory afferents from the head and neck project bilaterally, all the proprioceptive information available from the head and neck important in cueing position in space was coursing not only to the seeing hemisphere but also to the nonseeing hemisphere (Gazzaniga, 1966, 1969). The arm/hand would then go out to the correct point in space, even though there was no information about the third dimension of the object since no visual information had been communicated. As a consequence, the hand was not forming the appropriate anticipatory posture to grab the grape. Then quickly as the hand brushed by the grape, bumping into it—in a way, blindly—the hand would instantly adopt the correct posture for grabbing the grape. It all was an astounding cascade of self-cueing on how to appear as if the whole act was initiated as a whole piece from the beginning when it was not. Some planning, yes, followed by local control mechanisms.

The capacity for monkeys, for humans, indeed for even rats to adapt to challenge and self-cue themselves into completing their goals became a pervasive idea in our research and remains as one of the fundamental discoveries of how biological systems seem to keep it together. The goals are set at the highest level of nervous activity, and implementation is done in any way possible to complete the action.

The split-brain monkey work was exciting and the preparation was unbelievably powerful. With cross-cueing emerging as a big theme, it was natural enough to see whether emotional cues were also cross-integrated between the hemispheres. We figured out how to attach goggles to monkeys with each eye covered by a different colored filter, one red, one blue. In this way we could let the monkey view his cage through one eye by having the room lit in red. Then we could carefully turn the room light to blue, giving the other hemisphere a chance to see some additional information that would be emotionally arousing, such as a snake. Would that influence the red brain that was not able to see it? It did, of course, and that became the larger story about all the cues, coming from independent systems playing into the final action or behavior of an animal.

Another idea that was prominent at the time was the idea of using splitbrain animals in the following context. Keep one hemisphere completely intact and have the other open for systematic lesions in an effort to determine structure–function relationships. This overall strategy proved highly useful both in studying visuomotor coordination and in studying basic perceptual mechanisms. In one series of studies I wondered whether an isolated intact visual system might not actually see if it was disconnected from parietal and frontal cortex. Using the split-brain preparation, this was a possible experiment (Gazzaniga, 1966). One hemisphere was left completely intact while the other was lesioned to various degrees. Thus, as we lesioned more and more cortex in one isolated hemisphere, we could see whether there came a point where the animal could no longer perform a visual discrimination, even though the visual system was intact. To our surprise it worked and overall the experiments were consistent with Sperry’s view that “Perception is the preparation for response.”

I continued my interest in animal research during my postdoctoral years. When I left Caltech, I was fortunate enough to receive a fellowship to study at the Institute of Physiology in Pisa. I had come to know Giovanni Berlucchi when he had been a visiting fellow in Sperry’s lab. To know Giovanni is to love him, and he encouraged the fellowship to Pisa. The idea was that I was going to learn how to do neurophysiology and, by doing so, be enabled to study the actual neural code of the corpus callosum. While there, I also met Giacomo Rizzolatti and the three of us embarked on our journey to figure out the brain code (Berlucchi et al., 1967).

Of course, both Berlucchi and Rizzolatti went on to do groundbreaking neurophysiological research. I discovered in the process that the method was not for me. It took far too much patience and the capacity to spend dozens of hours sitting in one place. My restless ways triumphed, and I returned to studying patients.

It was not, however, before embarking on one last set of experiments in both rats and monkeys involving motivation. Upon returning to my new job at UCSB in 1966, I got to know David Premack. It is hard to think of a more important living psychologist than David Premack. As one considers our origins, our antecedents, our uniqueness as humans, it is Premack’s work that has guided us to so much of our current understanding of the way we are.

I met him when he was still carrying out his pioneering work untangling the morass of information that had painted a simple but incorrect picture of the nature of motivation. Behaviorism had developed a view of the learning animal as being motivated only by external contingencies and did not consider internal states and preferences. He turned the whole thinking about the nature of reinforcement on its ear by seeing beyond the easily observable and ascertaining, using the methods of science, the underlying secrets of what motivates animals, including us, to do anything. Seeing through easy explanations is his specialty.

In what later became known as the Premack Principle, he showed that what served as a reinforcer was reversible and could be predicted by the preference structure of an animal. Thus, a rat deprived of running would drink water if that gave it the opportunity to run. Conversely, if a rat was deprived of water, it would run in order to have the opportunity to drink. This is a powerful idea and it stuck with me. When I moved to NYU after early years at UCSB, Premack gave me one of his unique testing systems to test an idea I had. Would an adipsic rat, which is to say a rat that will not drink as the result of a lateral hypothalamic lesion, drink nonetheless if given the opportunity to run? If true, it would urge a more dynamic view of brain function and caution against the ever-growing tendency to see static models relating structure to function. In fact, we learned adipsic rats gladly drank if that is what they had to do to in order to run (Gazzaniga et al., 1974).

Premack was just starting his work on chimpanzee language and beginning to articulate the intellectual limits of our closest living relative and, in doing so, unearthing the factors that make us unique. He started with a particular chimp, Sarah. I know, as she lived down the hall from me for years when our time overlapped at UCSB. I don’t care for chimps. I have always found them too aggressive and bestial and quite frankly would walk in the other direction when Sarah approached with her trainer.

Nonetheless, following his work proved valuable again as the meta-language he developed for chimps proved useful in studying global aphasic patients, a project he and I did together with my graduate student Andrea Velletri Glass (Velletri-Glass et al., 1973).

I kept my animal research active until one cold day the NIH told me to pick my poison: either do animal research or human research, but not both. This came at a time when I had Richard Nakamura finishing up his thesis work on studying various memory phenomena in primates. My other student at the time was Joseph LeDoux. We were just beginning to launch a major set of studies on a new group of split-brain patients operated on at Dartmouth Medical School. The transition made sense and we complied. No more animal research for me, and LeDoux switched with me from monkey work to human studies.

Parallel Interest: Going outside Science

As I already mentioned, I had other interests in social issues. I had begun to question my social/political assumptions. During my undergraduate years, I had possessed all the normal interest for liberalism. In fact, I was a Catholic liberal, the worst kind; I believed that everything could be fixed and, if not fixed, forgiven. At some point, however, I started to think of liberalism as a cruel hoax. Things were not as mutable as the liberal activist must believe them to be. I was beginning to doubt fancy psychological theories of development and to become convinced that it is almost impossible to change anybody’s behavior in a serious way.

Anyway, some friends and I started something called the Graduate Committee for Political Education. We were tired of all the liberal speakers who got invited to Caltech. Where were the conservatives? We knew Caltech wouldn’t come along quickly or quietly, so we started our own group, rented a public auditorium in nearby Monrovia, and arranged for William F. Buckley, Jr. to give an evening lecture. I met Bill the day before at the home of his sister-in-law, who turned out to head the Red Cross and live in Pasadena. It was a pool-side lunch with, I will never forget, onion sandwiches. Now, have you ever had onion sandwiches? They are a delight, and Bill was quick to put me at ease, even at his boyish age of 36, and so we chatted about anything from his sister-in-law’s sandwiches to JFK. I remember using the word potentiate, which is a commonly used term in pharmacology, and his informing me that no such word existed in the English language. That was the last time that I was right in a dispute between the two of us that had to do with language.

That weekend, a friendship was born and survived over 50 years. Bill was naturally friendly and unflaggingly generous, though I believe he had no concept of the many implicit gifts he made to his friends. Most of my friends are in science, which is to say that they reflexively try to dissect assumptions on matters scientific. Yet as a group they tend to be painfully unable to apply those skills with wit to social and political agendas. When they do, the action tends to be tedious and joyless. Bill challenged everything, but always with a grin and with humor. His was a disposition that made it hard for others to rattle his resolve. He always was on top of things with the big picture. Experiencing that attitude about life served those who knew him in ways he was never able to appreciate.

Soon after the lecture in Monrovia, I discovered that there was a bit of Sol Hurok in me. After a couple of weeks of that evening’s great success, we decided to go big time. Why not arrange a series of debates on the American Constitution? Why not put out a book? Why not have fun? So I asked Bill if he would lead off such a series debating Steve Allen on the American Presidency. He said, “Sure.” Then I asked if he would write to Steve Allen since I didn’t know him. “Sure,” he said, adding that Allen’s wife, Jane Meadows, had grown up in Bill’s hometown. Bill wrote the letter, Steve said yes, and within a couple of weeks, I had arranged for two other debates. I had Robert Hutchins debating Bill’s brother-in-law, L. Brent Bozell, about the Supreme Court, and somehow I had arranged for James MacGregor Burns, one of JFK’s biographers, to debate Willmoore Kendall, the maverick conservative political theorist, on the Congress. I don’t know what I was thinking. A few weeks later, I realized I had signed contracts for auditoriums and speakers that totaled more than $10,000. The Graduate Committee for Political Education had $200 to its name.

On the morning of the debate, only 200 people had purchased tickets. Steve had taped his TV show the night before with Bill as a guest. They had warmed up for their debate about JFK, but the show wouldn’t air for 2 weeks. I was concerned about the lack of ticket sales and told Steve. Steve very matter-of-factly said, “Don’t worry, Mike—3000 people would show up to watch me play tiddlywinks.” As an aside, JFK was assassinated on the Thursday following the debate but before the taped show was to air. When that American tragedy occurred, both Steve and Bill saw to it that the show never aired.

As it turned out, 3300 people bought tickets that night, and two of them were Mr. and Mrs. Groucho Marx. Dozens of limousines and Rolls Royces pulled up for the big event to buy tickets for $2.75.

Backstage, Bill and his entourage waited in one room, and Steve and his waited in another. Since it was to be a debate, there would be prepared opening statements but, following those, the participants were to think on their feet. Bill Buckley did this better than anyone and, in that sense, it was an unfair match. But Steve had prepared as if for war. To guard against freezing up, he had prepared remarks for his rebuttal as well.

Out front, the crowd was boisterous. This was going to be the event of the century: Steve Allen, head of SANE, the movie-community chapter of the national antinuclear activist group, and Hollywood’s favorite liberal, pitted against William F. Buckley, American’s leading conservative, who was ready to tell the Soviets that we would nuke them if they made a false move. They were going to march through JFK’s foreign policy and examine it from Vietnam, to Cuba, to the Soviet Union. When the debaters took to the stage, the crowd rose to their feet and cheered them into battle. I walked to the very back of the auditorium, in a stunned state. What had I done? There were only two security guards.

The rest of the evening took care of itself. Here were two great showmen arguing their views. At one point, Buckley spotted Groucho Marx sitting in the front row. Sensing that the crowd needed a little jolt, he, without blinking, incorporated the opportunity into his rebuttal. He stared at Steve Allen and exclaimed, “Let’s face it, Steve, President Kennedy’s foreign policy might as well have been written by the Marx Brothers.” Now most folks hadn’t noticed his presence. Groucho stood up on cue, walked up on stage, strolled across to thunderous applause, and smoked his cigar all the while.

Bill was a pragmatist and, as such, he promoted the idea of legalizing drugs. His good friend Milton Friedman also promoted the idea, but more from his perspective of being a libertarian, something the conservative Bill Buckley was not. Bill’s position was that drugs were a plight and our policy was a disaster, so we had to find ways of fixing the situation. At one point, while he was preparing for a conference in Los Angeles, Bill started to grill me, which led to my own formation of opinions on the topic: “What do you know about drugs? What can you tell me about their action on the brain? Do you know anybody that has thought about the problem from the medical perspective?” I could see that I was about to learn a lot more about drugs than I already knew. I went to work on the problems, which turned out to be fascinating, and I eventually wrote the results of my work up for National Review in the form of an interview in 1995, which we conducted over e-mail. But that was only the beginning.

During all of this in 1990 Bill called one day to ask me to appear on Firing Line. “That’s television,” I said blankly. “Oh, you’ll be fine,” he replied, and, at length, I agreed and then proceeded to memorize every fact there is to know about drugs. That really wasn’t a very useful strategy, but it was the only one I could think of, and it was better than nothing. For weeks before the show, I pestered him with this or that question and went over in my mind how the show might go. Finally, the day arrived, and I went to a 23rd Street studio for the taping. In typical fashion, Bill was doing three shows in a row with 5-minute breaks in between. I went into the makeup room to wait for them to tape the two other shows, one of which featured the exiled King of Greece and the other, two English professors from Oxford talking about a book on Chaucer. Now, it was my turn to talk about drugs. Well, I survived and Bill was off to catch the shuttle to Washington. He had to give a speech that night.

A few years ago, I saw an article he wrote about his boyhood home, Great Elm in Sharon, Connecticut. His father had designed an exquisite indoor room, which was beautifully photographed for the article. I mentioned to Bill that I would love to see it someday. Within a few months, he arranged a rendezvous in Stamford, and we took the drive out to Sharon. It was a gorgeous fall Sunday, and when he picked me up at the train station, we took off immediately for what I thought was roughly a 20-minute drive. In fact, Sharon was almost 2 hours away, although somewhat shorter with Buckley driving. What a day. We hadn’t seen each other for quite awhile, so there was lots of catching up to do. I was telling him about various new findings on the brain and behavior, including the new survey finding that only 1.8% of the population was gay, as opposed to the often-claimed 10%. “Oh,” he said, “Do you believe that? I don’t, because if it were true, why I think I know every one of them.” You couldn’t get the wit out of him.

In all of this another friendship was born. Steve Allen became intrigued with my research and over the years we saw a great deal of one another. At one point he brought his family over to the laboratory at Caltech on a Sunday afternoon. He wanted to see how things were actually done. We talked for several hours and with his sharp wit and grace I found myself doing my first “outreach” of science education.

A few years later, when I was an Assistant Professor at the University of California, Santa Barbara, I had Psychology I duty (introductory psychology). One thousand students three times a week showed up at Campbell Hall. There is a bit of crowd control and mass motivation required when the numbers are this big. In short, one has to keep the students motivated. So I called Steve and asked if he would like to come up and give a lecture. . . . . gratis. He accepted in a flash and, as the lecture was at 8 am, he drove up the night before, stayed at a motel near the University, and showed up bright and early.

We had agreed he should talk about the creative process. I had arranged for a piano to be on the stage and the rest, as they say, is history. Steve was a man of many talents, songwriting being one of them. He told the story of what was behind his greatest hit, “Picnic.” Steve wrote the lyrics after receiving a call from the producer, and he wrote them in record time. As he looked back on it, he basically came up with a resource allocation model for creativity. Usually, he said, he would be asked to write a song with absolutely no constraints put on the assignment. In this case, the producer said, “I want you to write the lyrics to our movie theme that stars William Holden and Kim Novak and they will be dancing at a picnic.” As Steve pointed out, all his energies became focused on the task at hand. In the unconstrained situation, so much energy is lost trying to define the context and idea for a song, one is depleted by the time the actual task is apparent.

Steve Allen, Jr., his son, is a physician and we became quite close. He is hysterically funny and humane and he, like his father, was completely captivated by brain research. In fact, at one point I cooked up an idea of making a film about the brain and creativity. I had just moved to Stony Brook and, as part of a startup package, I had purchased a new Beaulieu 16 movie camera that allowed for sound to be recorded right on the film during filming. This made editing and production quite easy, or so I thought. While the camera was bought to use for my patient work, I took up the cause of making a science education film.

The camera, parabolic sound microphones, lights, and all the rest required several bags, all of them heavy or awkward to move around. I was undaunted, however, and proceeded to call Steve senior and ask if I could fly out to LA and film him as I fired at him questions about creativity. He couldn’t have been more agreeable, and off to LA I went.

I arrived at his home one Saturday morning and Steve was still lounging in his robe. I didn’t think people actually lounged in their robes except in the movies. Well, here we are. He walks me into his living room and suggests how I should set up the lighting, tripods, and all the rest. It all started to become surreal, and this little voice in me starts in: “What are you doing? Why are you bothering this guy in his robe? What are you going to do? Why aren’t you back at Stony Brook doing your research? Who do you think you are—Fellini?”

I was just about to leave, making some excuse, when Steve, said, “Looks like you are ready.” With that he starts to play one of his own compositions, This Could Be the Start of Something Big, and for a moment, I did think I was Fellini. The experience was exhilarating, and I vowed to take my gear everywhere to capture moments for the film. In fact, I took the gear to Paris a bit later, set it up in my hotel room at the Paris Hilton, threw open the window, and with the camera on automatic filmed myself standing in front of the window, with the Eiffel Tower in the background, and thought my second career was launched.

Oh my, we do crazy things. After filming riding up the Eiffel Tower and half of Paris, I went home, loaded up with my footage. With great anticipation I waited for it to come back from being developed, stuck it on my projector, and sat back to watch and savor my ingenuity. Let me simply say my escapade into filmmaking ended quickly. My favorite disastrous scene is in the hotel window. Because my camera was reading the light level of the bright Paris sky, the guy in the foreground looks like he is in a witness protection program and working with the CIA. Of course, one always looks for the silver lining. Steve looked terrific in his robe.

Of course, the real lesson in all of this is that human nature is a constant. We all get channeled into our little groups and tend not to keep active relationships outside of our academic world. That is a big mistake. Both Bill Buckley and Steve Allen taught me that all of us are trying to figure out the big picture. And both insisted on having fun while doing it. It was this experience that emboldened me to work on the President’s Council on Bioethics later in life. Tough, reasoned discourse with politically sophisticated minds from both the left and right motivated me to explore a range of social problems.

Moving to New York

One day I got a call from Leon Festinger. He had just moved to New York. Years before, while I was still a lowly assistant professor at UCSB and he was a famous Stanford professor, he had invited me to a seminar at his home. A mutual friend of ours at Stanford assured me that the seminar would be interesting, adding, “Oh, and Leon is really smart, Mike—you’d better prepare.”

This was one of Leon’s quirks: As he became acquainted with people in foreign fields, he offered them his gracious hospitality, assuming they would have something to say. And so it was that I sat down in an easy chair in his living room, with Leon about 3 feet from me, smoking his ever-present Camel, his students clustered behind him. Drinks were served, and we were off to the races.

Leon was not going to miss a single word of this neophyte’s remarks, and it turned out to be a glorious evening. There I was, with the smartest man in the world listening attentively to me talk about my experiments, and with deference at that. I would say that over the next 20 years or so, we talked about our own research programs no more than 5% of the time when we were together. What is it about discovering a true intellect that causes conversations to wander? Leon viewed and considered everything from a perspective informed not only by years of experience but also by enormous knowledge of almost every topic.

Anyway, Leon urged me to apply for a job at New York University and to move east. Eventually I did and for the subsequent 20 years was based in New York. First it was NYU, then Stony Brook, and finally Cornell Medical School. What was common to all those endeavors was my weekly lunch with Leon (Gazzaniga, 2006). I could not get enough of him, and we launched several intellectual ventures as well. Over the years we started study groups on behavioral economics with Stan Schachter. Leon and I also started a group studying human origins, his new passion, that deeply impacted my own thinking as well and which led to my last book, HUMAN.

New York University and Cornell Medical School

In New York I finally was able to study the neurologically damaged patient, which before had not been possible in Santa Barbara. Even though I had moved to the NYU Graduate School, the Medical School was close by and very welcoming. Before long, my student Andrea Velletri Glass and I were following up on an idea I had at Santa Barbara: Could a meta-language system that Premack had developed for chimps be used to communicate with patients who were globally aphasic? The results were striking. Patients, using artificial symbols that they had learned to associate with objects, actions, and descriptors could use these associations to describe actions carried out by the experimenter. It was like unlocking the secrets of a jailed mind (Veletri-Glass et al., 1973).

Over the years, the neurologic patient proved to be a rich source of information about the many ways the unconscious brain actively carries out critical operations that ultimately influence our conscious life. At Cornell Medical School we began to study our first patients with neglect. In one study Bruce Volpe, Joseph Ledoux, and I (1979) revealed that perceptual information presented in their neglected half space nonetheless influenced perceptual judgments in their opposite conscious visual field. This was unheard of at the time but slowly grew into a small cottage industry. Overall, the simple introduction of forced-choice techniques revealed the unshakable fact that cognitive capacity remained evident in patients and it was processed outside the realm of their conscious processes.

In a related observation, Gail Risse and I examined the limits of access that conscious processes have to memories when “secrets” were established in the right hemisphere of patients who temporarily had their left brain anesthetized. In this experiment, objects were placed in the patients’ functioning left hand and palpated while their left brain/right hand was asleep. Minutes later when the left brain woke up, the patients were first asked to verbally say what they had held in their left hands. They claimed to have no idea. Seconds later, however, the left hand, now awake and nonparetic, easily pointed to matching objects (Risse et al., 1978).

I have always been captivated by the wealth of knowledge that can be gained by studying patients with focal disease. Fred Plum and Jerry Posner at Cornell really encouraged this interest and in the good oldfashioned way. Just do it! So that is what my students and I did along with an entirely talented group of young neurology residents at Cornell, such as Bruce Volpe, Ruth Nass, John Dougherty, Jonathan Victor, and others. From NYU Graduate School to Stony Brook to Cornell, there were always studies going on with patients. We studied anmesics, patients with neglect (Volpe et al., 1979), blindsight (Fendrich et al., 1992; Wessinger et al., 1997), aphasia (Gazzaniga et al., 1973), motor disorders (Volpe et al., 1979), and more (see Nass and Gazzaniga, 1987). Perhaps our most extensive effort with neurologic focal lesioned patients was on the blindsight phenomeon.

Probing the Unconscious

When unconscious processes are occurring, it used to be thought they were mainly happening in subcortical structures. The split-brain patient has these structures intact and it was of great interest to us to determine which unconscious phenomenon might still be connected and which were not following cortical disconnection. A series of reports in the 1970s indicated that, even though a patient may not consciously see in a blind visual field of vision due to a cortical lesion, the patient’s hand might be able to respond to stimuli presented in the blind field. To explain this bizarre finding, dubbed blindsight, researchers proposed that the phylogenetically older parts of the midbrain were carrying out the task, not the cortex. We wanted to know more.

It is a fact that 98% of what the brain does, it does outside of conscious awareness. All of our sensory-motor activities are unconsciously planned and executed. As I sit here and type this sentence, I have no idea how the brain actually pulls off the task of directing my fingers to the correct keys on the keyboard. I have no idea how the bird, sitting on the outside deck, a glimpse of which I must have caught in my peripheral vision, just caught my attention, while I nonetheless continue to type these words. Furthermore, the same goes for rational behaviors. I am not aware of how the neural messages arise from various parts of my brain and are programmed into something resembling a rational argument. It all just sort of happens.

It is easy to see why very clever psychologists began to wonder whether formal cognitive psychology had missed the boat. Perhaps the challenge is to study that great platform of life, the unconscious. Larry Weiskrantz had coined the term “blindsight” to account for the remarkable phenomenon, the ability to see even though the visual cortex had been damaged or removed. Immediately following his original report of the phenomenon of blindsight, philosophers, psychologists, and neuroscientists became fascinated with the observation and with the possibility that a means to study the great mystery of the unconscious had been found.

As the early reports accumulated, we began to examine related issues in other types of brain-damaged patients. Damage to the parietal lobe of the brain, for example, causes strange symptoms to appear. If the damage occurs on the right side of the brain, most patients experience a phenomenon called neglect. Thus, when looking straight ahead, they deny seeing anything to the left of where they are looking, even though their primary visual system is perfectly intact. This fascinating region of the cerebral cortex generates a veritable constellation of exotic disruptions when it is damaged. Patients also frequently deny that they are ill, even though they experience weakness of the left hand and arm. When they are shown their left hand and asked whose hand it is, they claim that it certainly isn’t theirs.

When all of these behaviors are considered, it becomes clear that, somehow, the parietal lobe is involved with the attentional mechanism. Something is at work, distinct from the parts of the brain that simply represent visual information. Information is getting into the brain, but this process is occurring outside the realm of conscious experience. We showed this basic fact in a number of ways. In one study, we asked patients with neglect to judge whether two lateralized visual stimuli, one appearing in each visual field, were the same or different (Volpe et al., 1979). So a patient might see an apple in one part of his or her visual field and an orange in the other. Conversely, two apples or two oranges might be presented, one in each half visual field. The patients were able to perform this task accurately. However, when they were questioned as to the nature of the stimuli after a trial, they could easily name the stimulus in their right visual field but denied having seen the stimulus presented in their neglected left field.

These studies were the first in a long series that have now been carried out by several laboratories. Taken together, they show that the information presented in the neglected field could be used to make decisions, even though it could not be consciously described. A decision was correctly made that two objects were different, but the patient could only name one of them.

In the early 1980s, Jeffrey Holtzman began to study blindsight in my lab. We were fortunate to have a piece of equipment, the Purkinje eyetracker, which allowed for the very careful assessment of the position of the eye in relation to where a stimulus might appear, allowing for the precise presentation of stimuli within the scotoma.

We first studied a 34-year-old woman who had undergone surgery to clip an aneurysm in her right half brain. These nasty rats’ nests of vessels can break, causing severe brain damage, so when they are detected they are usually operated on. The surgery was expected to have the consequence of producing blindness in part of the patient’s vision, since damage would occur to her right occipital lobe, the brain area with the aneurysm. Sure enough, after surgery, there was what is called a dense left homonymous hemianopia. In other words, she couldn’t see to the left of a point she was looking at. Her magnetic resonance image (MRI) revealed an occipital lesion that clearly spared both extra-striate regions as well as the main midbrain candidate for residual vision, the superior colliculus. These intact areas should have been able to support many of the blindsight phenomena commonly reported.

This patient was truly blind, even though she had the brain structures intact that should support the phenomenon of blindsight. He studied her for months and got nothing. He wrote the work up and published it in one of the finest scientific journals (Holtzman, 1984). It met with deafening silence. Blindsight was too big an idea to be shot down by one experiment, even a great experiment beautifully executed. Jeff said, “Great Mike, I come to your lab to learn some new tricks and you know what I discover? Blind people are blind. That kind of brilliance ought to get me a job at Harvard.” Actually Jeff made a huge difference in the lives of all of us. No funnier man ever lived and, horrifically, his life was snuffed out as a young man. His work on attentional mechanisms are classics (Holtzman et al., 1981, 1982, 1985; see also Luck et al., 1989; Luck et al., 1991).

We left the problem alone for a few years until a new graduate student, Mark Wessinger, came along to the laboratory and we took up our interest again. Also, my colleague Bob Fendrich, a fellow student with Jeff, came to the lab. By this time, we had moved to Dartmouth Medical School and were calling upon a different kind of patient. Our first case was a woodsman from New Hampshire who had had a stroke that knocked out his right visual cortex (Fendrich et al., 1992). Nonetheless, he pursued life with vigor and was quite a marksman. Before studying what the woodsman’s brain could or couldn’t do in his blind visual field, Bob argued that we should do perimetry to discover where and how big the blind spot was. He, too, was an expert at managing the complex eye-tracking device, and Bob likes to start whatever he does at the beginning.

For these tests, we were also armed with a newly acquired image stabilizer, which allowed us to keep images steady on the retina despite any eye motion a patient might make. Our woodsman’s scotoma was carefully explored using high-contrast black dots on a white background. In fact, a whole matrix of dots was presented in an area of his scotoma. Hundreds of trials were presented over many testing sessions. It is always heart-warming to see the deep respect the average citizen pays to the increase of human knowledge. Once matters are explained to them, they are almost always enthusiastic participants.

The efforts paid off. In the sea of blindness, we found what we called a “hot spot,” an island of vision. In one small area, about 1-degree in diameter, the woodsman could detect the presence of visual information. Now if it was truly a 1-degree window, a 2-degree spot should not be detected. Even though a 2-degree spot is larger and under normal conditions would be easier to detect, he should not be able to see it because the black dot would be larger than the window. That is exactly what was found. The patient could not see the larger stimulus. Follow-up testing revealed that the patient could detect differences between light of different wavelengths in the “hot spot.” The technology was crucial for the success of the experiment—we were able to reveal the island of vision only because of the particular device we had for testing him, and very few researchers in the world had access to such equipment. Could it be that the island was the source of so-called blindsight?

None of this, of course, is to suggest that unconscious processes are not of constant and primary importance to our vision. It is yet another demonstration of the truth that most of what our brain does, it does outside of the realm of conscious awareness. I and my colleagues do reject, however, the proposition that, since blindsight demonstrates vision outside the realm of conscious awareness, it supports the view that perception can occur in the absence of sensation. Because the role of primary visual cortex is to process sensory inputs, advocates of this view have found it useful to attribute blindsight to alternative visual processing pathways. I submit that this formulation is unnecessary and implausible. It is commonplace to design demanding perceptual tasks where nonneurologic subjects routinely report low confidence values for tasks they are performing above chance. However, it is not necessary to propose secondary visual systems to account for such data, since the primary visual system is intact and fully functional.

The Dartmouth Split-Brain Cases: Discovering the Interpreter

The second decade of my professional life gave rise to the idea of modular concepts and the interpreter. By the 1970s, the passage of time had provided more studies and more patients, and the original nature of split-brain studies had been modified substantially. The field had drifted into thinking about different kinds of consciousness, and the notion that mind left dealt with the world differently than mind right was the major conclusion of studies during this era. Though interesting in its own right, this characterization of how each hemisphere processes information still begged the question of what consciousness actually was and how the brain enabled it to be experienced. In many ways, the work in the early 1970s was misleading.

Reports with chimeric stimuli found that split-brain patients favor the right hemisphere for “gestalt” stimuli and the left hemisphere for “analytical tasks,” and our hypotheses briefly took on a new direction. We began to argue that it wasn’t so much that there were separate conscious systems following commissure section but simply that each hemisphere possessed different cognitive duties. The earlier overcharacterization of left brain/ right brain function was short lived in the scientific community, but it has been annoyingly persistent in the popular press.

During the mid-1970s, a number of reports emphasized an additional feature of right hemisphere specialization. Brenda Milner and Laughlin Taylor reported superior performance in the right hemisphere on nonverbal tactile stimuli. Joseph LeDoux (1978) and I found the manipulations of a stimulus to be critical in bringing out right hemispheric superiorities. For example, right hemispheric superiority was revealed only in a block design test in which the patient manipulated the blocks to make the patterns required; in an equivalent, “match to sample” test, in which patterns were only visually inspected, right superiority disappeared. While these new observations were challenging enough to the simple view of hemispheric functioning and to ideas about dual consciousness, the new conceptual framework was even more antithetical to existing concepts about the unity of conscious experience. In brief, the new view suggested that the brain was organized in a modular fashion with multiple subsystems active at all levels of the nervous system, and that each subsystem could process data outside the realm of conscious awareness. These modular systems were fully capable of producing behaviors, mood changes, and cognitive activity. Such activities were in turn monitored and collated by a special system in the left hemisphere that I called the “interpreter” (Gazzaniga, 1985).

We first revealed the interpreter using a simultaneous concept test. In this type of test, the subject is shown two pictures—one exclusively to the left hemisphere and one exclusively to the right (Ledoux et al., 1977; Gazzaniga and Ledoux, 1978). The subject is then asked to choose pictures that are associated with those lateralized images from an array of pictures placed in full view in front of them. For example, a picture of a chicken claw is flashed to the right visual field, and a picture of a snow scene to the left visual field. Of the pictures placed in front of the subject, the obviously correct association is a chicken for the chicken claw and a snow shovel for the snow scene. Accordingly, subject PS responded by choosing the chicken picture with his right hand and the snow-shovel picture with his left. The left hemisphere, however, was aware only of the chicken-claw image, while the right hemisphere was aware only of the snow-scene image. When asked why he chose these items, his speaking left hemisphere replied, “Oh, that’s simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed.” The left hemisphere, observing the left hand’s response, interpreted that response only in the context of its own sphere of knowledge—a sphere that did not include information about the snow scene that had been presented to the right hemisphere.

In a related experiment, in the few patients with rightas well as lefthemisphere language, we lateralized written commands by presenting them tachistoscopically to the subject’s left visual field. In an example where the command was “laugh,” the patient laughed and, when asked why, replied, “You guys come up and test us every month. What a way to make a living!” If the command “walk” was flashed to the right hemisphere, the patient would stand up from his or her chair and start to leave the testing van. When asked where they were going, the left brain might say, “I’m going into the house to get a coke.” Again, the left hemisphere observes and interprets the actions of the isolated right hemisphere in order to create a verbal response.

At this point, our research had shown that there are many ways to influence the left brain interpreter, and we were still interested in determining whether emotional states presented in one hemisphere would have an influence on the affective tone of the other hemisphere. At this point we met VP, a dazzling 28-year-old woman with a keen sense of life who was a patient of Dr. Mark Rayport of the Medical College of Ohio. She is introspective about her medical history and articulate in expressing her feelings. When we first met her, her right hemisphere skills were limited to simple writing of answers and the capacity to carry out verbal commands. Flash the command “smile” to her right hemisphere and VP could do it. Ask her why she was smiling and her left hemisphere would concoct an answer. But 2 years later, VP’s right hemisphere could directly tell us why, because by then it had developed the capacity to talk. During the time when only her left brain could speak, however, we were able to set up mood states in her nontalking hemisphere and study whether the talking hemisphere was aware of the mood, and, if so, how it dealt with the induced mood. From all of the other studies, of course, it was clear that the left brain was not directly knowledgeable about the actual pictures or movies that had been shown to the right brain. But could it detect the mood?

Using a very elaborate optical computer system that detects the slightest movement of the eyes, we were able to project a movie exclusively to the left visual field. If the patient tried to cheat and move her eyes toward the movie image, the projector would automatically shut off. The movie her right hemisphere saw was about a vicious man pushing another man off a balcony and then throwing a fire bomb on top of him. It then showed other men trying to put out the fire. When VP was first tested on this problem, she could not access speech from her right hemisphere. When asked about what she had seen, she said, “I don’t really know what I saw. I think just a white flash.” I asked, “Were there people in it?” VP replied, “I don’t think so. Maybe just some trees, red trees like in the fall.” I asked, “Did it make you feel any emotion?” VP said, “Maybe I don’t like this room, or maybe it’s you, you’re getting me nervous.” Then VP turned to one of the research assistants and said, “I know I like Dr. Gazzaniga, but right now I’m scared of him for some reason.”

This experimental evidence merely illustrates a rather extreme case of a phenomenon that commonly occurs to all of us. Our mental systems set up a mood that alters the general physiology of the brain. In response, the verbal system notes the mood and attributes a cause to the feeling based on available evidence. Once this powerful mechanism is clearly demonstrated, given the complexity of real-life emotional stimuli, one cannot help but wonder how often we are victims of spurious emotional/cognitive correlations.

Although our split-brain subjects always possess at least some understanding of their surgery, they never say things like, “Well, I chose this because I have a split-brain and the information went to the right, nonverbal hemisphere.” Even patients who have exceptional IQs tend to view their responses as behaviors emanating from their own volitional selves. As a result, they incorporate those behaviors into theories to explain why they behave as they do. One can imagine that, at some point, a patient might be studied who would choose not to interpret such behaviors because of an overlying psychological structure that prevented the response. Or one can imagine a patient learning by rote what a “split-brain” is all about and why, therefore, a certain behavior most likely occurred. Such a circumstance would certainly complicate the role of the researcher, and such subjects might well not be able to offer explanations for their behaviors. There are occasions when a patient who is having trouble controlling his or her left arm due to a transient state of dyspraxia will tend to dismiss anything that he or she does under the direction of the right brain. This makes the simultaneous concept test inappropriate. In such situations, a single set of pictures is presented and only one hand is allowed to make the response. For example, the word pink is flashed to the right hemisphere and the word bottle to the left. Placed in front of the subject are pictures of at least 10 bottles of different colors and shapes, and the subject is required to respond using the right hand.

When this test was run on split-brain subject JW, on a particular day when he said that he could not control his left hand, he immediately pointed to the pink bottle with the right hand. When asked why he had done this, JW said, “Pink is a nice color.” In this case, JW responded to a stimulus that had been presented to his right hemisphere using his right hand, in defiance of our expectation that he would be unable to do so. When he was pressed to explain how he had done it, his left-hemisphere speech apparatus was unable to provide an explanation, and so the interpreter responded as best it could, claiming that the subject had made a simple aesthetic choice. It has been well established that the human brain follows a modular organization, and that those “modules” do manifest themselves through function-specific physical regions of the brain.

The precise nature of the neural networks that carry out those functions is less clear, however. What is apparent is that they operate largely outside the realm of awareness, and that they announce their computational products to various executive systems that result in behavior or cognitive states. Managing and interpreting all of this constant and parallel activity is the role of the left hemisphere’s interpreter module. The interpreter is of primary importance to our identity as human beings; it is what allows for the formation of beliefs, which in turn yield mental constructs that allow us to do more than simply respond to stimuli.

Developing a Field: The Birth of Cognitive Neuroscience

They used to say that Jack Benny, the world’s funniest man, was also the best audience; everyone loved to try out his stuff on Jack. If George Miller is in an audience, he is usually asleep. If he is the audience—that is, if you are one on one—he is the best. He analyzes constantly as you pour out your story. He asks probing questions and then, as you hear your own answers, and as those silly formulations bounce off his deadpan expression, you begin revising them. There is not much that is new in this world, and certainly not much new about the psychological nature of human beings. What passes for discovery these days tends to be an individual scientist’s rediscovery and reterming of some well-established phenomenon. Most of these “discoveries” are soon forgotten, but George knows all of them. So on the hundredth trip to the well, you are overjoyed to see a glimmer in his eye and to realize that perhaps there was something to your last idea.

We started exchanging stories in the late 1970s, mine about episodes in the clinic and his about new experimental strategies. I would tell him about patients with high verbal IQs who lacked a grammar school child’s ability to solve simple problems. He would tell me that psychologists do not yet have anything resembling a theory of intelligence or mind. He urged the continued collection of dissociations in cognition, as seen in the clinic, in the hope that a theory would emerge from these seemingly bizarre and scattered observations (see Hirst, 1993).

I took him on my rounds one day and showed him a variety of phenomena that ranged from perceptual disorders to language disorders. He had never seen anything like it and commented afterward that the neurologic patient was really what many psychologists were looking for. After all, he observed, psychologists try to test the brain’s limits by making college sophomores work fast or by presenting stimuli rapidly to provoke errors. In the clinic, the errors pour out of otherwise sound brains with little or no effort.

One patient we saw was a distinguished New York executive who had fallen down a staircase. He was reported to be globally aphasic, which means that he would not understand much, if anything, and would speak only a little. As we arrived in his room, the computer tomography technicians were fetching him for a scan, so George and I tagged along. The technician asked Mr. C. to slide over to the gurney, to which he replied, “Yes, sir.” Once positioned and rolling down the hallway to the scanner, he was asked about his comfort. “Are you feeling okay?” “Yes, sir,” said Mr. C. After arriving at the scanner, the technician slid the patient off the gurney onto the table and again asked if he felt all right. “Yes, sir,” said Mr. C. The scan was performed and Mr. C. was returned to his room. The technician, who was familiar with my studies, turned to me and asked why we were interested in this patient, as he felt there was nothing wrong with him. I turned to the patient and said, “Mr. C., are you the King of Siam?” “Yes, sir,” he replied with great assuredness. George grinned and observed that success is always grounded in simply asking the right question.

As we continued to consider how best to launch our new field, we talked about everything from neglect to neologisms during our evening rendezvous. It was on one of those evenings that we coined the term “cognitive neuroscience.” What we meant by cognitive neuroscience would emerge, slowly. We already knew that neuropsychology was not what we had in mind; tying specific functions to lesioned brain areas would not be our enterprise. The intellectual impoverishment of that idea seemed self-evident, especially with the advent of new brain imaging techniques that revealed the extent of the damage to the surrounding area following what had previously been thought to be focal damage.

Years have intervened, but the idea that neuroscience needs cognitive science has prevailed. The early imaging work of Marcus Raichle, Michael Posner, Steve Petersen, and others set the standard in this regard. So too, for the emerging field of human electrical recordings led by Steven Hillyard and his colleagues. The scientists in both these areas knew that the molecular approach, in the absence of the cognitive context, limits the neuroscientist to pursuing answers to biological questions in a manner not unlike that of the kidney physiologist. Although such approaches represent an admirable enterprise, when put in that light they make it impossible for the neuroscientist to attack the central integrative questions of mind-brain research. Cognitive neuroscience has now become something of a household word because of these advances and many others. The field now has its own journal, society, and conferences. In fact, the most highly attended meetings at the huge Society for Neuroscience convention are always on topics in cognitive neuroscience. In recent times, most of the presenting scientists are former members of the cognitive neuroscience summer institute.

Summer Institute in Cognitive Neuroscience

When the James S. McDonnell Foundation decided to fund the field of cognitive neuroscience, they set aside some funds for training. The event started out at Harvard and Stephen Kosslyn led the way. He did a fantastic job the first year and set a high standard. The plan has not changed much during the past 20 years. Every summer, 70 students from all over the world participate in a 2-week course that runs all day long. I don’t think there has been one failure.

The original group that cooked up this idea thought the Institute would move around from year to year from one campus to another. It turned out that was neither practical nor desirable. After Kosslyn’s launching, it fell to me to shepherd the program for the past 20 years. It has been one of the best experiences of my life. Where else can you have 30 top scientists come to town and lecture to 70 bright fellows? Where else can you have outstanding neuroscientists dissect human brains, report on clinical studies, and present basic science lectures on neuronal function capped off with a touch of cognitive theory? I hope it runs forever or at least until we have solved the mind/ brain problem.

The President’s Bioethics Council

In the fall of 2001, I received a call from Professor Leon Kass, the bioethicist from the University of Chicago. President George W. Bush had just appointed him to head up a new Council on Bioethics, and he wondered whether I might be interested in participating. We had all just been through the horror of 9/11 and not a person in America was not thinking about how to best serve and help our country. Naturally, I agreed, and I have never regretted the decision.

Nothing really prepares one for such assignments. When I took it on, I had never thought deeply about issues in bioethics. Dr. Kass assured me not to worry about that. It was to be a committee about bioethical issues, but not a committee of professional bioethicists. (In fact, most bioethicists are not scientists, but rather philosophers, theologians, and others interested in public policy on morality.) All points of view and varying kinds of expertise were wanted. I was supposed to help with issues in neuroscience.

Feeling a bit out of my league as I headed off to our first meeting, I told myself I would sit back and listen and learn. After all, bioethics was an area of study founded to monitor medical practices—from organ transplants to determining brain death. I am a Ph.D., not an M.D. If questions related to neuroscience came up, I’d be happy to supply the best information I could.

Those who have known me might be amused to hear that this was my intention; they won’t be surprised that as it turned out, I couldn’t keep quiet. We started with embryonic stem cell research, something that, to me, is an obviously needed field of study; yet many were opposed on issues that seemed to have nothing to do with bioethics or even science. It became clear to me that the beliefs we all hold can color our judgments on issues that should be considered independent of personal belief systems. Having made a career of trying to understand how the brain enables mind, I had some insight into how beliefs are formed, and I was none too thrilled to see the future treatment of debilitating diseases, let alone the future of our nation’s scientific research, being decided on the basis of such capriciousness. I soon found that neuroscience had much to say on issues of bioethics.

Around this time, the term “neuroethics” was coined by William Safire to describe “the field of philosophy that discusses the rights and wrongs of the treatment of, or enhancement of, the human brain.” In this sense, neuroethics is a spinoff of bioethics. The field of bioethics was developed and defined to take medical ethics further, as scientific findings became more advanced and needed more specialized philosophers thinking about the impact of science on things such as genetic engineering, reproductive science, brain death, and so on. Clearly, many of these traditionally bioethical topics can be looked at through the lens of neuroethics. One way to look at neuroethics is that any time a bioethical issue involves the brain or central nervous system, neuroethics should have a say.

But neuroethics is more than just bioethics for the brain. As the field develops, we need to expand its scope and its mission. Much of the discussion in neuroethics so far has, once again, been among nonscientists. It is time for neuroscientists to jump into the fray. I define neuroethics as looking at how we want to deal with the social issues of disease, mortality, lifestyle, and the philosophy of living, informed by our understanding of underlying brain mechanisms. Neuroethics should be an effort to come up with a brainbased philosophy of life (Gazzaniga, 2005).

Events

My passion for true and thoughtful interactions among scientists was solved by a simple social device. I started to organize small 10-person conferences on almost a yearly basis for about 10 years. Since I was a one-man show, my strategy was to pick a topic of great interest, pick a venue people loved to visit, and let each of them have a full half day to talk about their research. It worked. The venues included Venice, Barcelona, Paris, Kushadasi, Moorea, and Napa.

The meeting at Moorea provided a bit more than I hoped: I learned that appearances are everything. Moorea was an exquisite place, and I discovered that with various package deals a meeting in the South Seas cost less than one in Omaha. I have found such arrangements to be effective in getting first-class people to participate in a conference, usually after making only one phone call. Indeed, this meeting proved no different. What was different came subsequently. I took heat for the effort from various foundation chiefs who believed the exotic setting created the perception that the participants were not serious.

The participants were, in fact, stellar. Francis Crick, R. Duncan Luce, Gary Lynch, Ira Black, David Orton, Gordon Shepherd, Jon Allman, Geoffrey Hinton, Corey Goodman, Herb Killackey, and the indefatigable Leon Festinger. There was also a wonderful young foundation officer, Eric Wanner. We met each morning and afternoon. I converted my grass hut into the meeting room, and matters really began to rock. The topic was the biology of memory and both Lynch and Orton had prepared manuscripts before the meeting that served as a launch pad for discussion. To simply observe there were a variety of perspectives would be to miss the moment.

At another unforgettable meeting, one of those golden moments occurred. A group of us that included Stephen J. Gould met in Venice to think about evolution and the brain. For his presentation, Gould decided to make it a walking tour through San Marco Cathedral. There we were being lectured on adaptations and his spandrel theory beneath the very spandrels that triggered this idea in Gould. It was a moment to remember. A couple of years before we had also gathered in Venice to hear Gould, Changeux, Premack, Pinker, Singer, Lynch, and others discuss selection versus instruction theory. Everyone seemed to love those meetings. As for me, I wrote a book about the topic (Gazzaniga, 1994).

Developing University Programs

I truly detest academic committee meetings. Nowhere else has so much been said about so little. Early in my career I decided to basically not show up. Instead, when I thought a new academic goal was desirable I went out and did it but always with the support of kindred souls. That was how George Miller and I worked for years. The same system enabled me to build other programs at Dartmouth, Davis, and now UCSB.

After developing one of the first programs in cognitive neuroscience at Cornell Medical School, where I successfully constructed a large program project grant from the NINDS on a wide variety of behavioral neurologic problems that dealt with attention, perception, memory, and more, I decided to move to the woods of Vermont. My family was growing and our two-bedroom New York apartment was not doing the trick for us. Indeed, with so much of my time being spent on the Dartmouth series of patients, it made a lot of sense.

We loved our time at Dartmouth and in between two different stints, one at the medical school and one at the College, we moved to Davis to establish the UC Davis Center for Neuroscience. All of these assignments involved administrative duties as well as active research programs and the everpresent need to obtain funding. None of the successes of these programs would have been possible without this attitude—“Let Mike do it until he screws up. Then rein him in.” I am deeply grateful for all of my colleagues who let it all happen.

Enduring Issues and Thoughts

In the 1980s I became convinced that our understanding of consciousness is best enabled by placing the phenomenon in an evolutionary perspective. That context causes certain truths to emerge for me that give rise to the idea that, at its core, human consciousness is a feeling about specialized capacities. Throughout the development of split-brain research, one salient fact has remained: disconnecting the two cerebral hemispheres, while eliminating direct interaction between the halves of the cortex, does not typically disrupt cognitive and verbal intelligence. The left hemisphere remains the dominant cognitive entity following such surgery, and this dominance seems to be sustained not by the entire cortex but by specialized circuits within the left hemisphere. In short, the unique properties of the inordinately large human brain are engendered by its circuitry, not simply by its size. It is the accumulation of specialized brain circuits, then, that accounts for the human conscious experience.

Furthermore, our sense of being conscious never changes during the normal aging process. Taken together, these two views lead to the conclusion that what we refer to as “consciousness” is nothing more or less than a collection of feelings that we have about our specialized capacities. We have feelings about people and objects we interact with, and about our capacities to think, to believe, and to use language. In other words, consciousness is not a distinct system—it reflects the affective component of specialized systems that have evolved to enable human cognitive processes. Combined with the human inferential system, which seems to be limited to the left hemisphere, it empowers all sorts of mental activity. Our consciousness of those mental activities depends on our capacity to assign feelings to them, and that is what distinguishes human consciousness from everything else, including the electronic artifacts with which we surround ourselves.

Naturally, viewing consciousness as a myriad of feelings about specialized abilities predicts that the consciousness emanating from one hemisphere would differ radically from that emanating from the other. Whereas left-hemisphere consciousness would reflect what we refer to as normal conscious experience, right-hemisphere consciousness would vary as a function of the specialized circuitry that half-brain possesses. Mind left, with its complex cognitive machinery, can distinguish between the states of sorrow and pity, for instance, and it appreciates the feelings associated with each state. The right hemisphere does not possess the cognitive apparatus to create such distinctions and, as a consequence, its state of awareness is relatively low. Specific types of reduced right-hemisphere capacity, therefore, have specific implications for the states of consciousness of the subjects in which they are found.

Patients with a split brain without right-hemisphere language capability exhibit a limited capacity to respond to patterned stimuli that ranges from no capacity at all to the ability to make simple matching judgments at above-chance levels of performance (Sidtis et al., 1981). Patients who possess the capacity to make perceptual judgments that do not involve language do not exhibit the ability to make a simple same/different judgment within the right brain when both stimuli are lateralized simultaneously. In other words, when two simultaneously presented figures required the judgment “same,” the right hemisphere failed. This profile is commonly seen in all kinds of patients with a silent right hemisphere, and it seems to be independent of overall subject intelligence. This minimal-capacity profile stands in marked contrast to that of patients who possess right-hemisphere language. The right brain of these patients is responsive, and their overall capacity to respond to both language and nonlanguage stimuli has been well catalogued and reported.

In the East Coast series of patients we study, this observation includes the case of JW, whose right hemisphere has understood language and has had a rich lexicon throughout our association with him, as assessed by the Peabody Picture Vocabulary Test and other specialized tests. Until recently, however, JW could not generate speech from his right hemisphere (Baynes et al., 1992). Studies with VP and PS revealed that these patients were able to understand language and to speak from either half-brain. It would be reasonable to suppose that this extra skill would add to their right-brain capacities to think, which is to say to interpret the events of the world.

It turns out, however, that the right hemispheres of both patient groups are poor at making simple inferences (Gazzaniga and Smylie, 1984). The subjects were tested by being asked semantically to combine the content of two pictures that were presented one after the other to their left visual fields. Presented with a picture of a match and then a picture of a woodpile, for example, neither group was successful in deducing that a burning woodpile was the correct result. In another test, simple words were presented one after another to the subject’s left visual field, and the subject was instructed to choose the word that reflected the causal relationship between them from a list of six possible answers. The subjects also failed these trials, a typical one of which might consist of the words “pin” and “finger” being flashed to the right brain, the correct answer being “bleed.” Although the right hemisphere could always find a close lexical associate of a word that was given by itself, it could not perform the interpretive function necessary to recognize relationships between two words.

In this light, it is hard to imagine that the left and right hemispheres have similar conscious experiences. The right cannot make inferences and, as a consequence, is extremely limited in what it can have feelings about. The left hemisphere, on the other hand, constantly and almost reflexively labels stimuli, making causal inferences and carrying out a host of other cognitive activities. Recent studies have shown that the left brain carries out visual search tasks in a methodical manner, whereas the right hemisphere tends to perform haphazardly. The evidence surrounds us that the left hemisphere is predisposed to analyze and differentiate the workings of the world, whereas the right hemisphere simply monitors its surroundings (Phelps and Gazzaniga, 1992; Metcalfe et al, 1995).

I was recently asked by a Time Magazine reporter: “If we could build a robot or an android that duplicated the processes behind human consciousness, would it actually be conscious?” It is a provocative question and it is one that persists, especially as one tries to capture the differences between the spheres of consciousness that exist between separated left and right brains. Much of what I have written here has appeared before in other forums and, for students of split-brain research, is not all that new. Yet I find the way we all nuance our understanding of complex topics to be ever changing, as none of us holds the true answers in our hip pocket. I found myself answering the reporter with what I feel is a new twist. Underlying this question is the assumption that consciousness reflects some kind of process that brings all of our zillions of thoughts into a special energy and reality called personal or phenomenal consciousness. That is not how it works. Consciousness is an emergent property and not a process in and of itself—much like the taste of salt that is the emergent and unpredictable product of sodium and chloride coming together. Our cognitive capacities, memories, dreams, and so on reflect distributed processes throughout the brain, and each of those entities produces its own emergent state of consciousness.

Consider one fact. A human split-brain patient who has had the two halves of her brain disconnected from one another does not find that one side of the brain misses the other. Her left brain has lost all consciousness about the mental processes managed by her right brain, and vice versa. This is just as with aging or with focal neurological disease. When it comes to cognitive content, we don’t miss what we no longer have access to as opposed to missing capacity due to disruptions in more sensory-motor processes such as vision, hearing, and speech. The emergent conscious state arises out of each capacity. If they are disconnected or damaged, there is no underlying circuitry from which the emergent property arises. The thousands, if not millions, of conscious moments that we experience each reflect one of our networks being “up for duty.” When it finishes, the next one pops up and the pipe organ-like device plays its tune all day long. What makes emergent human consciousness so vibrant is that our pipe organs have lots of tunes to play, whereas rats, in contrast, have few. And the more we know, the richer the concert becomes.

Closing Thoughts

Ever since I heard a lecture a few years back by an astrophysicist who laid out the reasons why extraterrestrials must exist, I have wondered what they would think about us humans and the ideas we think we are studying. I recently wrote a short thought piece on the matter (Gazzaniga, 2010). In brief, it points out much of the type of neuroscience that has been done to date has not squared up with the large fact sitting in the room. The mind is an emergent phenomenon, generated by neurons alone that can in turn constrain its progenitors. A fancy way of saying this is that our field of neuroscience is at a choice point. No longer can we simply make observations at one level of organization. As Roger Sperry put it toward the end of his career, “Instead of an exclusive bottom-up microdeterminism, we substitute a bi-directional model adding a reciprocal top-down emergent or holistic form of downward control . . . . The emergent whole, that is, constantly exerts downward control over its parts.” I have arrived at the same place, and I only wish I were young enough to start over and tackle that issue.

I have only captured a small dimension of the personal, social, and intellectual forces that shaped my life and made it such a fine run. I have saved the best notes for last: my family. I have been married twice, both to fine people. The fruits of my marriage have delivered us six children, all of them bright, beautiful, funny, and hardworking. There never seem to be “teen problems” around our home. My wife Charlotte has for the past 33 years made sure no such downward mood swings could occur. In addition to being mother to her four step-children and our two own children, she never waivered one second with equal treatment under the rule that family is supreme. Somehow while doing this, she help cofound the Journal of Cognitive Neuroscience, ran the household, held the dinner parties, arranged for all the trips, ran experiments on patients, and drove our special motor home for patient testing.

To see one’s children grow and blossom, of course, is the joy of all parents. It is the wit that keeps a family together. A dinner conversation might go like this. Dad: “Hey kids, I am coming up with a new idea about brain organization, that it is modular.” Zazzy: “Modular? Dad, our eighth grade curriculum is modular. We have the English module, the math module. . .and so on. You are going to have to do better than that.” Dad: “Eat your vegetables.” Or while during my days on the Bioethics Council. . . Dad: “So ok, when does life begin?” Zack: “Only after an open field tackle.”

Life still goes on apace. Life is good.

Acknowledgments

Much of the foregoing has been collected together from other articles and essays I have written over the years. This too-long statement finds me aghast about whom I have not commented on more thoroughly. The literally dozens of colleagues that I have been close to will have to be thanked in another way. Most important, being in academics for 50 years allows one to train and to learn from dozens of outstanding colleagues. I want to at least note those that have made my life so fulfilling.

Jacopo Annese, Ph.D.

Abigail Baird, Ph.D.

Kathleen Baynes, Ph.D.

Paul Corballis, Ph.D.

Karl Doron, Ph.D.

Robert Fendrich, Ph.D.

Brett Foxman, M.D.

Andrew Francis, Ph.D., M.D.

Chadd Funk

Margaret Funnell, Ph.D.

Scott Johnson Frey, Ph.D.

James Eliassen, Ph.D.

Alan Gibson, Ph.D.

Pamela Greenwood, Ph.D.

Todd Handy, Ph.D.

Jeffrey Holtzman, Ph.D.

Jeffrey Hutsler, Ph.D.

David Johnson, Ph.D.

Marc Jouandet, Ph.D., M.D.

Alan Kingstone, Ph.D.

Kenneth Leslie, Ph.D.

Joseph LeDoux, Ph.D

William C. Lofuts, Ph.D.

Ruth Nass, M.D.

George R. Mangun, Ph.D.

Michael Miller, Ph.D.

Richard Nakamura, Ph.D.

Molly Colvin Putnam, Ph.D.

Kathleen Redington, Ph.D.

Patricia Reuter-Lorenz, Ph.D.

Jo Renn, M.D., Ph.D.

Gail Risse, Ph.D.

Matt Roser, Ph.D.

John Seamon, Ph.D.

John J. Sidtis, Ph.D.

Valerie Stone, Ph.D.

Mark Jude Tramo, M.D.

David Turk, Ph.D.

Betty Tuller, Ph.D.

Jack Van Horn, Ph.D.

Andrea Velettri-Glass, Ph.D.

Jonathan Victor, Ph.D., M.D.

Bruce T. Volpe, M.D.

C. Mark Wessinger, Ph.D.

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Gazzaniga, M.S., Risse, G.L., Springer, S.P., Clark, E., & Wilson, D.H Psychologic and neurologic consequences of partial and complete cerebral commissurotomy. Neurology 1975; 25, 10–15.

Gazzaniga, M.S., Sidtis, J.J., Volpe, B.T., Smylie, C., Holtzman, J., & Wilson, D. Evidence of para-callosal verbal transfer after callosal section: A possible consequence of bilateral language organization. Brain 1982; 105, 53–63.

Gazzaniga, M.S., Smylie, C.S., Baynes, K., Hirst, W., & McCleary, C. Profiles of right hemisphere language and speech following brain bisection. Brain and Language 1984; 22, 206–220.

Gazzaniga, M.S., Szer, I.S., & Crane, A.M. Modification of drinking behavior in the adipsic rate. Experimental Neurology 1974; 42, 483–489.

Gazzaniga, M.S., Van Patten, C., Fendrich, R., & Kutas, M. Neuropsychological correlates of callosal remnants in the human. Neurology 1989; 39, 942.

Gazzaniga, M.S., Velletri Glass, A., Sarno, M.R., &Posner, J.B. Pure word deafness and hemispheric dynamics: A case history. Cortex 1973; 9, 136–143.

Glickstein, M., Berlucchi, G. The Corpus Callosum: Mike Gazzaniga, the Caltech Lab and subsequent research on the Corpus Callosum. In P. A. Reuter-Lorenz, K. B. Baynes, G. R. Mangun,& E. A. Phelps (eds) The Cognitive Neuroscience of Mind, A Tribute to Michael S. Gazzaniga 2010; 3–24. MIT Press, Cambridge, MA.

Greenwood, P., Wilson, D.H., & Gazzaniga, M.S. Dream report following commissurotomy. Cortex 1976; 13, 311–316.

Greenwood, P., Wilson, D.H., & Gazzaniga, M.S. Dream report following commissurotomy. Cortex 1977; 13, 311–316.

Handy, T.C., Gazzaniga, M.S., & Ivry, R.B. Cortical and subcortical contributions to the representation of temporal information. Neuropsychologia 2003; 41, 1461–1473.

Handy, T.C., Miller, M.B., Schott, B., Shroff, N.M., Janata, P., Van Horn, J.D., Inati, S., Grafton, S.T., & Gazzaniga, M.S. Visual imagery and memory: Do retrieval strategies affect what the mind’s eye sees? European Journal of Cognitive Psychology 2004; 16, 631–652.

Handy, T.C., Schaich Borg, J., Turk, D.J., Tipper, C., Grafton, S.T., & Gazzaniga, M.S. Placing a tool in the spotlight: Spatial attention modulates visuomotor responses in cortex. NeuroImage 2005; 26, 266–276.

Handy, T.C., Tipper, C.M., Borg, J.S., Grafton, S.T., & Gazzaniga, M.S. Motor experience with graspable objects reduces their implicit analysis in visual and motor-related cortex. Brain Research 2006; 1057, 156–166.

Heinze, H.J., Mangun, G.R., Burchert, W., Hinrichs, H., Münte, T.F, Scholz, M., Gàs, A., Johannes, S., Scherg, M., Hundeshagen, H., Gazzaniga, M.S., & Hillyard, S.A. Combined spatial and temporal imaging of brain activity during visual selective attention in humans. Nature 1994; 372, 543–546.

Hirst, W. Conceptions of the Human Mind: Essays in Honor of George A. Miller. 1993; Routledge, London.

Holtzman, J. Interactions between cortical and subcortical visual areas: Evidence from human commissurotomy patients. Vision Research 1984; 24:8:801–814.

Holtzman, J.D., & Gazzaniga, M.S. Dual task interactions due exclusively to limits in processing resources. Science 1982; 218, 1325–1327.

Holtzman, J.D., & Gazzaniga, M.S. Enhanced dual task performance following callosal commissurotomy in humans. Neuropsychologia 1985; 23, 315–321.

Holtzman, J.D., Sidtis, J.J., Volpe, B.T., Wilson, D.H., & Gazzaniga, M.S. Dissociation of spatial information for stimulus localization and the control of attention. Brain 1981; 104, 861–872.

Hughes, H.C., Reuter-Lorenz, P.A., Fendrich, R., & Gazzaniga, M.S. Bidirectional control of saccadic eye movements by the disconnected cerebral hemispheres. Experimental Brain Research 1992; 91, 335–339.

Hutsler, J.J. & Gazzaniga, M.S. Acetylcholinesterase staining of human auditory and language cortices: Regional variation of structural features. Cerebral Cortex 1996; 6, 260–270.

Hutsler, J.J., Loftus, W.C., & Gazzaniga, M.S. Interindividual variation of regional cortical surface area asymmetries. Cerebral Cortex 1998; 8, 11–17, 1047–3211.

Johnson, J.D., & Gazzaniga, M.S. Cortical-cortical pathways involved in reinforcement. Nature 1969; 223, 71.

Johnson, J.D., & Gazzaniga, M.S. Interhemisphere imitation in split-brain monkeys. Experimental Neurology 1970; 27, 206–212.

Johnson, J.D., & Gazzaniga, M.S. Some effects of non-reinforcement in split-brain monkeys. Physiology and Behavior 1971; 6, 703–706.

Johnson, S.H., Corballis, P.M., & Gazzaniga, M.S. Within grasp but out of reach: Evidence for a double dissociation between reaching and grasping mechanisms in the left hemisphere. Neuropsychologia 2001; 39, 36–50.

Jouandet, M.L., & Gazzaniga, M.S. Cortical field of origin of the anterior commissure of the rhesus monkey. Experimental Neurology 1979; 66, 381–397.

Kingstone, A., & Gazzaniga, M.S. Subcortical transfer of higher-order information: More illusory than real? Neuropsychologia 1995; 9, 321–328.

Kingstone, A., Enns, J.T., Mangun, G.R., & Gazzaniga, M.S. Guided visual search is lateralized in split-brain patients. Psychological Science 1995; 6, 118–121.

Kingstone, A., Grabowecky, M., & Gazzaniga, M.S. Subcortical semantic processing: A failure to replicate in the callosotomized brain. Neuropsychology 1996; 9, 321–328.

Kosslyn, S.M., Holtzman, J.D., Farah, M.J., & Gazzaniga, M.S. A computational analysis of mental image generation: Evidence from functional dissociations in split-brain patients. Journal of Experimental Psychology: General 1985; 114, 311–341.

Kutas, M., Hillyard, S.A., & Gazzaniga, M.S. Processing of semantic anomaly by right and left hemispheres of commissurotomy patients: Evidence from eventrelated potentials. Brain 1988; 111, 553–576.

Kutas, M., Hillyard, S.A., Volpe, B., & Gazzaniga, M.S. Late positive event-related potentials after commissural section in humans. Journal of Cognitive Neuroscience 1990; 2, 258–271.

Ladavas, E., De Pesce, M., Mangun, G.R., & Gazzaniga, M.S. Variations in attentional bias in the two disconnected cerebral hemispheres. Cognitive Neuropsychology 1994; 11, 57–74.

LeDoux, J.E., Risse, G., Springer, S., Wilson, D.H., & Gazzaniga, M.S. Cognition and commissurotomy. Brain 1977; 100, 87–104.

LeDoux, J.E., Smylie, C.S., Ruff, R., & Gazzaniga, M.S. Left hemisphere visual processes in a case of right parietal symptomology: Implications for theories of cerebral lateralization. Archives of Neurology 1980; 37, 157–159.

LeDoux, J.E., Wilson, D.H., & Gazzaniga, M.S. A divided mind: Observations on the conscious properties of the separated hemispheres. Annals of Neurology 1977; 2, 417–421.

LeDoux, J.E., Wilson, D.H., & Gazzaniga, M.S. Block design performance following callosal sectioning: Observations on functional recovery. Archives of Neurology 1978; 35, 506–508.

LeDoux, J.E., Wilson, D.H., & Gazzaniga, M.S. Manipulo-spatial aspects of cerebral lateralization: Clues to the origin of lateralization. Neuropsychologia 1977; 15, 743–750.

Loftus, W.C., Tramo, M.J., Thomas, C.E., Green, R.L., Nordgren, R.A., & Gazzaniga, M.S. Three-dimensional quantitative analysis of hemispheric asymmetry in the human superior temporal region. Cerebral Cortex 1993; 3, 348–355.

Luck, S.J., Hillyard, S.A., Mangun, G.R., & Gazzaniga, M.S. Independent hemispheric attentional systems mediate visual search in split-brain patients. Nature 1989; 342, 543–545.

Luck, S.J., Hillyard, S.A., Mangun, G.R., & Gazzaniga, M.S. Independent hemispheric attentional systems mediate visual search in split-brain patients. Journal of Cognitive Neuroscience 1994; 6, 84–91.

Mangun, G.R., Plager, R., Loftus, W., Hillyard, S.A., Luck, S.J., Clark, V., Handy, T., & Gazzaniga, M.S. Monitoring the visual world: Hemispheric asymmetries and subcortical processes in attention. Journal of Cognitive Neuroscience 1994; 6, 265–273.

Metcalfe, J., Funnell, M., & Gazzaniga, M.S. Right hemisphere superiority: Studies of a split-brain patient. Psychological Science 1995; 6, 157–164.

Miller, M.B., Van Horn, J.D., Wolford, G.L., Handy, T.C., Valsangkar-Smyth, M., Inati, S., Grafton, S., & Gazzaniga, M.S. Extensive individual differences in brain activations associated with episodic retrieval are reliable over time. Journal of Cognitive Neuroscience 2002; 14(8), 1200–1214.

Nakamura, R.K., & Gazzaniga, M.S. Hemispherectomy vs. commissurotomy in the monkey: One hemisphere can be better than two. Experimental Neurology 1978; 59, 202–208.

Nass, R.D., & Gazzaniga, M.S. Lateralization and specialization of the human central nervous system. In F. Plum (Ed.), Handbook of Physiology 1987; 701–761. The American Physiological Society, Bethesda, MD.

Oppenheim, J.S., Skerry, J.E., Tramo, M.J., & Gazzaniga, M.S. Magnetic resonance imaging morphology of the corpus callosum in monozygotic twins. Annals of Neurology 1989; 26, 100–104.

Phelps, E.A. & Gazzaniga, M.S. Hemispheric differences in mnemonic processing: The effects of left hemisphere interpretation. Neuropsychologia 1992; 30, 293–297.

Phelps, E.A., Hirst, W., & Gazzaniga, M.S. Deficits in recall following partial and complete commissurotomy. Cerebral Cortex 1991; 1, 492–498.

Putnam, M.C., Steven, M.S., Doron, K.W., Riggall, A., & Gazzaniga, M.S. Cortical projection topography of the human splenium: Hemispheric asymmetry and individual differences. Journal of Cognitive Neuroscience 2009; epub

Putnam, M.C., Wig, G.S., Grafton, S.T., Kelley, W.M., & Gazzaniga, M.S. Structural organization of the corpus callosum predicts the extent and impact of cortical activity in the nondominant hemisphere. Journal of Neuroscience 2008; 28(11), 2912–2918.

Reuter-Lorenz, P.A., Nozawa, G., Gazzaniga, M.S., & Hughes, H.H. The fate of neglected targets: A chronometric analysis of redundant target effects in the bisected brain. Journal of Experimental Psychology, Human Perception and Performance 1995; 21, 211–230.

Risse, G., LeDoux, J.E., Wilson, D.H., & Gazzaniga, M.S. The anterior commissure in man: Functional variation in a multi-sensory system. Neuropsychologia 1975; 16, 23–31.

Risse, G.L., & Gazzaniga, M.S. Well-kept secrets of the right hemisphere: A carotid amytal study of restricted memory transfer. Neurology 1978; 28, 950–953.

Risse, G.L., LeDoux, J., Springer, S.P., Wilson, D.H., & Gazzaniga, M.S. The anterior commissure in man: Functional variation in a multi-sensory system. Neuropsychologia 1978; 16, 23–31.

Roser, M.E., Fugelsang, J.A., Dunbar, K.N., Corballis, P.M., & Gazzaniga, M.S. Dissociating causal perception and causal inference in the brain. Neuropsychology 2005; 19, 591–602.

Seymour, S.A., Reuter-Lorenz, P.A., & Gazzaniga, M.S. The disconnection syndrome: Basic findings reaffirmed. Brain 1994; 117, 105–115.

Sidtis, J.J., Volpe, B.T., Holtzman, J.D., Wilson, D.H., & Gazzaniga, M.S. Cognitive interaction after staged callosal section: Evidence for a transfer of semantic activation. Science 1981; 212, 344–346.

Sidtis, J.J., Volpe, B.T., Wilson, D.H., Rayport, M., & Gazzaniga, M.S. Variability in right hemisphere language function after callosal section: Evidence for a continuum of generative capacity. The Journal of Neuroscience 1981; 1, 323–331.

Sperry, R.W. A powerful paradigm made stronger Neuropsychologia 1998; 36, 1063–1068

Stein, B.E., Price, D.D., & Gazzaniga, M.S. Pain perception in a man with total corpus callosum transection. Pain 1989; 38, 51–56.

Turk, D.J., Banfield, J.F., Walling, B.R., Heatherton, T.F., Grafton, S.T., Handy, T.C., Gazzaniga, M.S., & Macrae, C.N. From facial cue to dinner for two: the neural substrates of personal choice. NeuroImage 2004; 22(3), 1281–1290.

Turk, D.J., Heatherton, T.F., Kelley, W.M., Funnell, M.G., Gazzaniga, M.S., & Macrae, C.N. Mike or me? Self-recognition in a split-brain patient. Nature Neuroscience 2002; 5(9), 841–842.

Van Horn, J.D., Grafton, S.T., Rockmore, D., & Gazzaniga, M.S. Sharing neuroimaging studies of human cognition. Nature Neuroscience 2004; 7(5), 473–481.

Velletri-Glass, A., Gazzaniga, M.S., & Premack, D. Artificial language training in global aphasics. Neuropsychologia 1973; 11, 95–103.

Volpe, B.T., Herscovitch, P., Raichle, M.E., Hirst, W., & Gazzaniga, M.S. Cerebral blood flow and metabolism in human amnesia. Journal of Cereb Blood Flow and Metabolism 1983; 3(suppl 1), S5–S6.

Volpe, B.T., LeDoux, J.E., & Gazzaniga, M.S. Information processing of visual stimuli in an extinguished field. Nature 1979; 282, 722–724.

Volpe, B.T., LeDoux, J.E., & Gazzaniga, M.S. Spatially oriented movements in the absence of proprioception. Neurology 1979; 29, 1309–1313.

Volpe, B.T., Sidtis, J.J., Holtzman, J.D., Wilson, D.H., & Gazzaniga, M.S. Cortical mechanisms involved in praxis: Observations following partial and complete section of the corpus callosum in man. Neurology 1982; 32, 645–650.

Wessinger, C.M., Fendrich R., & Gazzaniga M.S. Islands of residual vision in hemianopic patients. Journal of Cognitive Neuroscience 1997; 9, 203–221.

Wessinger, C.M., Fendrich, R., Ptito, A., Villemure, J.G., & Gazzaniga, M.S. Residual Vision with Awareness in the field contralateral to a partial or complete functional hemispherectomy. Neuropsychologia 1996; 34, 1129–1137.

Bertil Hille

BORN:

New Haven, Connecticut

October 10, 1940

EDUCATION:

Yale University, B.S. (1962)

The Rockefeller University, Ph.D. (1967)

APPOINTMENTS:

Fellow, Cambridge University, Physiological Laboratory, Cambridge, England (1967–1968)

Assistant Professor, University of Washington, Department of Physiology and Biophysics (1968–1971); Associate Professor (1971–1974); Professor (1974–present)

Wayne E. Crill Endowed Professor, University of Washington, Department of Physiology and Biophysics (2005–present)

HONORS AND AWARDS (SELECTED):

Kenneth S. Cole Award of the Biophysical Society Membrane Biophysics Subgroup (1975)

Mathilde Solowey Award in Neurosciences from NIH Foundation for Advanced Education in the Sciences (1976)

Member of NIH NINDS Physiology Study Section (1981–1984)

National Academy of Sciences, U.S.A. (1986)

Research Award from the McKnight Endowment Fund for Neuroscience (1988–1994)

3rd Annual Bristol-Myers Squibb Award for Distinguished Achievement in Neuroscience Research with Erwin Neher and Jean-Pierre Changeux (1990)

Columbia University Louisa Gross Horwitz Prize for outstanding basic research in Biology or Biochemistry with Clay Armstrong (1996)

1999 Albert Lasker Award for Basic Medical Research, with Clay Armstrong and Roderick MacKinnon (1999)

The 2001 Gairdner Foundation International Award with Clay Armstrong and Roderick MacKinnon (2001)

Institute of Medicine (2002)

Wayne E. Crill Endowed Professorship, Department of Physiology & Biophysics, University of Washington, Seattle (2005–)

Doctorate of Science, honoris causa, The Rockefeller University (2008)

Bertil Hille helped establish the concept of ion channels as membrane proteins forming gated aqueous pores. He showed that Na⁺ and K⁺ channels of axons can be distinguished by drugs such as tetrodotoxin and tetraethylammonium ion, and that their ionic selectivity can be understood by a limiting pore size, the selectivity filter, and by movements of ions through a series of saturable sites. He showed that local anesthetics enter Na⁺ channels in a statedependent manner. In later studies of modulation of ion channels by G protein–coupled receptors he distinguished two new signaling pathways. A fast, pertussis toxin-sensitive pathway turned on inward rectifier K⁺ channels and turned off Ca²⁺ channels by G protein Gβγ subunits. A slow, pertussis toxin-insensitive pathway turned off some K⁺ and Ca²⁺ channels by depleting the plasma membrane phosphoinositide PIP₂. Hille wrote the widely used textbook “Ion Channels of Excitable Membranes.”

Bertil Hille

This essay assumes that less senior readers might be more interested in what scientific life was like one and two generations ago and how ideas arose. The more recent science is a matter of published record and does not need as full repetition. My own trajectory illustrates, like those of many others, that serendipity and opportunity are as significant as careful planning in determining a career. People are not born to fill a certain role. Much happens during early development. We are molded and redirected by interactions with mentors and unexpected opportunities.

Parents

I was born into an academic family in New Haven, CT. My parents were Scandinavian immigrants, so my brother Harald and I are first-generation Americans, born just before the United States entered World War II. My father, C. Einar Hille (1894–1980), was a Yale math professor and scholar (Ph.D., Stockholm University, 1918) with many honors, including being elected to the U.S. National Academy of Sciences and the Royal Swedish Academy of Sciences. My mother, Kirsti Ore Hille (1906–2001), was energetic, intellectually and artistically gifted, and an avid reader of books. Her honors included several dozen engraved silver cups for taking first place in downhill slalom ski races in Norway. Her hands were often busy with crafts, including weaving. She encouraged conversation, scientific thinking, causal explanations, and the academic community. My father was fully occupied with higher mathematics, so my mother undertook most of the tasks of parenting and the household. At that time, professors were not as well paid as today, and we lived with some New England frugality, although always in the larger classic houses that could be rented within walking distance of the university—my father didn’t drive.

Early Education and Languages

During my first years, my father spoke Swedish and my mother Norwegian, the two languages being mutually understandable. Gradually our household shifted to English, but as is common among Europeans, my parents were polyglots who spoke and read German and French easily as well as fragments of other languages. Their English was interlaced with foreign phrases. It would be a rare dinner if we had not discussed the etymology and linguistics of several foreign expressions, and we had not finished with an encyclopedia, a dictionary, or an atlas on the table. My father gave his mathematical lectures in several languages. Later on, my mother became an article abstracter for the Quarterly Journal of Alcohol Studies, summarizing papers from the French, German, and Scandinavian. While we were children, my father had sabbatical and other leaves, which gave us a half year in Stockholm, Sweden, a full year in Nancy, France, and a half year in Mainz, Germany. European cities still were deeply scarred by damage from World War II. We crossed the Atlantic by ocean liner each time. In Europe, my brother Harald and I went to the public grade school, lycée, or Gymnasium, so we too received some classical European education in several countries. For several months in advance, 78 RPM records of language practice would be playing during dinner. Each European visit included several months of touring in our automobile (mother driving) to visit the best art museums, cathedrals, castles, and mathematicians. Our cars were small and without radios or heaters. We read aloud from the Guides Michelin, Baedeker’s, and Guides Bleus in several languages, and my parents, especially my father, explained which king was married to whom from where and who succeeded whom and intrigued or fought where. He had a deep fund of geography and history. On one of these trips when I was 12 years old, we were visiting German mathematicians and stopped at Wetzlar, where my parents secretly bought me a Leitz compound microscope including an oil immersion objective and a dissection kit. I got them on my next birthday. The same year, I was missing first-year Latin at home, so my brother (a year older) had to drill me in Latin verbs as we drove between castles of the Loire valley. Eventually, Harald also studied several Slavic languages and became a linguist and terminology expert in many languages. He still works with languages at the United Nations in New York.

We attended private schools—on scholarship. The Foote School was the grade school of choice for Yale professors’ children; thus, many of my classmates had an academic family background. The education, environment, and student body were supportive and excellent. Mrs. Hitchcock, the wife of a Yale School of Medicine professor, drilled into us a powerful, concise, Anglo-Saxon style of writing. I also became fond of drawing and water coloring. I liked the intersection of art and geometry and remember holding forth to my sixth grade class for an hour on two-point and three-point perspective and how correctly to turn a house plan into a full perspective drawing. With my dissection kit I held a demonstration of the inner organs of the frog complete with its heart beating in situ for somewhat reluctant friends. I collected butterflies, spread their wings, and pinned them with tiny labels into cigar boxes. Entomologist Professor Charles Remington across the street from our home at the Connecticut Agricultural Experiment Station kindly discussed collecting and showed me their many drawers of pinned and labeled type specimens.

When I was 13 years old, my mother decided that, like my brother and most graduates of the Foote School, I should be sent away to boarding school for 4 years to be taught essential American ways. Westminster School offered a strong traditional education to white boys in coats and ties, with outdoor sports led by the Masters and discipline entrusted to the older boys, the Sixth Formers. It followed the English style of many New England prep schools then. The motto was “with grit and grace.” I profited from Ashley Olmstead’s writing discipline, enjoyed singing in the choir (first soprano), and studied Latin and French literature. The formal science teaching was classical, yet still new and fascinating for me. Electrons went around atomic nuclei in stately and precise planetary Bohr orbitals. Biology taught morphology and taxonomy but not yet mechanisms. When Thomas Hooker and I finished the school’s math offerings and declared that we would try for the Advanced Placement Exam in mathematics in our final year, the teacher (for just the two of us) and we had to struggle with a quickly purchased calculus book since none of the three of us knew how derivatives or integrals worked. Collaboratively we made it. Today calculus is available in most high schools. Many of the boys at Westminster were from more moneyed classes and knew much more about machismo, girls, style, popular culture, alcohol, and tobacco. They were also physically more developed than me. I often felt shy, uncomfortable, and awkward in their company. In times of loneliness I retreated to the choir room and played the piano for a few hours. Our class was the first to have a black student, Booker T. Bradshaw, from Richmond, Virginia. He was strong in sports and excelled as a student. Although from an elite family, he felt out of place for other reasons. Booker and I were roommates and close friends for the last 3 years. He had a deep collection of jazz, country, and popular music. Later, Jack Partridge, my roommate at Yale, introduced me to bluegrass music.

Starting in a Lab

I have had the extraordinary good fortune to receive generous and supportive guidance at many stages in my scientific career. When I was 16 years old, I began working summers in the Yale Biology lab (1957). This was after my junior year at Westminster. Edgar J. Boell, the Chair of Yale Zoology and a close friend of our family, made good on a promise he had made years before. I was given a research project to study the respiratory function of the larval gills of the salamander Ambystoma tigrinum, an organism that Ross Harrison had pioneered for embryology decades before at Yale. Boell was the Ross

G. Harrison Professor of Zoology. I worked with those larval salamanders until 1962 when I graduated from Yale. For three summers, I measured their respiration volumetrically using the classical Warburg apparatus, a sort of shaking water bath with perhaps 20 gasometric manometer chambers holding one larva apiece. Ed Boell was an extremely supportive mentor, who introduced me personally to scientific culture and to each step of preparation and laboratory measurement. His warm enthusiasm for careful work and patient observation leading to reliable results was an excellent formative lesson and role model for a high-school apprentice.

Yale

In 1958 it seemed perfectly natural to go on to Yale (and become a zoologist), where my tuition would be free, and to apply to nowhere else. Extraordinary teachers included the memorable Vincent Scully in history of art, a real showman whose long wooden pointer slapped the two giant screens in an otherwise totally dark room as he paced on the elevated stage and orated loudly in dramatic sentences. He kept his audience of 800 (all boys) in rapt attention while expounding wonderful original ideas. I have often hoped to bring even just a fraction of his drama to my lecturing. I still enjoy art history. E. Robert Beringer teaching honors physics had a beautiful gift of explanation and wonderful homework problems. He made physics challenging and exciting to learn. I took most of the advanced undergraduate courses in zoology and enjoyed them all, from invertebrate zoology, comparative anatomy, up to biochemistry. Everything made sense through descent from a common ancestor and adaptation to the environment. Cell biology was a standout with R. Bruce Niklas, just one year after his Ph.D. on moving chromosomes. I also took all of the lecture courses for the Biophysics major and was strongly influenced by Harold J. Morowitz’s many biophysical and theoretical insights. His thinking about free energy, entropy, science, and Eyring rate theory became very useful to me more than a decade later. We read Schrődinger, “What Is Life.” Physical chemistry in the Chemistry Department was a beautiful combination of natural science with simple math. Could biology achieve that? All of those courses introduced exciting ideas that were new for me. One time, George von Békésy was invited to give a series of lectures in Zoology on the cochlea; perhaps it was the year before his Nobel Prize. A few of us undergraduates asked if he would have lunch with us. Naturally in our youth we would ask him what was the secret to success, and he told us, “I never decide that something is correct until I have shown it three ways!”

Although my zoology curriculum was mostly classical, in my senior year (1961–1962) we became aware of a turning point toward a new biology. I had been reading in past issues of my father’s collection of the Proceedings of the National Academy of Sciences (PNAS), including Linus Pauling’s proposals of the α-helix and the β-sheet, and started looking at the new-journal shelf in Zoology each week. In that year, François Jacob and Jacques Monod defined the lac operon and the lac repressor (Journal of Molecular Biology), Francis H. Crick and Sydney Brenner argued for a triplet code (Nature), and Marshal W. Nirenberg, Severo Ochoa, and competitors began uncovering the triplet codons one-by-one (PNAS). I was excited to report on those advances in the weekly Biology Club that five of us seniors held. There we also discussed amber mutants of Neurospora, the territorial calls of frogs, respiration in the turtle cloaca, and pigmentation of butterfly wings.

Part of my senior honors thesis was to measure and analyze the time course of uptake and clearance of 137Cs (as a K⁺ tracer) in intact Ambystoma larvae. I developed a several-compartment model description much like those of pharmacokinetics. Timothy Goldsmith, then a new faculty recruit, became my honors advisor. He would challenge me with exotic readings such as on the liquid-junction potential, in German (Henderson, 1907), and on the voltage clamp and the squid action potential (Hodgkin and Huxley, 1952). That was the first time I saw this kind of work. The squid axon papers were less than a decade old and still not fully accepted, because they seemed to biologists to be like, “give me ten parameters and I can make an elephant wag its tail.” I was hearing a distrust of modeling in biology from my zoology teachers and came away not sure whether that was a good way to go. I didn’t realize at that time that this would be a core of my future work.

Woods Hole

Four summers in Woods Hole also had an enormous formative influence. After my sophomore year at Yale, I spent some weeks at the Oceanographic Institution, WHOI, being a free crew member on oceanographic cruises, with jobs like collecting deep water samples with Nansen bottles, measuring the thermocline, making plankton tows, or assisting in pressing water for analysis out of cores as they were collected from the glacial clay deposits off the continental shelf. We had day watches and night watches around the clock. I spent the following summer in the undergraduate research program at WHOI measuring photosynthesis and photodamage by ultraviolet light on samples of intertidal algae. Our supervisor John W. Kanwisher, with his wife Joan and little girls (including future cognitive neuroscientist, baby Nancy Kanwisher), also needed crew for their new boat on weekends, so I learned to sail a gaff-rigged schooner. Mario R. Capecchi (of homologous recombination in mouse) was an undergraduate in the same small program that summer. Another summer and a half I worked with Roger D. Milkman at the MBL on heat-shock perturbation of posterior-crossvein development in Drosophila pupae. These measurements could be made very quantitatively and begged for a quantitative model, which we made with multiple Q₁₀s and numerous kinetic steps. I got a lot of practice in developing multicompartment models on a portable analog computer by myself. Reinforcing the concept that modeling may not be good for biology, the resulting manuscripts were rejected by seven journals and finally were published in the Biological Bulletin, but little cited. I still like that work! A final Woods Hole summer while I was in graduate school (1965) was spent in Harry Grundfest’s lab at the MBL, voltage clamping what seemed to be a voltage-gated chloride conductance in the weak electric organ of the skate, Raja erinacea. Michael

V. L. Bennett cosupervised my work. It fascinated me that this putative channel for chloride behaved kinetically so much like the well-known delayed rectifier K⁺ channels. It is abundant in the electric organ and could be followed up today.

Quite beyond the actual summer lab work, the MBL was a place of vigorous biological foment, a place to fill a curious mind with wonderful new ideas, a renaissance education in a cutting-edge science cafeteria. Everybody who was anybody was there in the summer and they were open to casual discussions of all of life science. Without being registered, I attended all the lectures of the physiology course, maybe twice, and some of the embryology and the invertebrate zoology courses. There I heard Matthew S. Meselson tell about the Meselson and Stahl experiment on DNA and Edwin J. Furshpan and David D. Potter explain about gap junctions in the crayfish and the Hodgkin-Huxley work. I attended all the Friday night lectures by great scientists and some Tuesday night “electrobiology” presentations, where Ichiji Tasaki and Harry Grundfest often challenged each other stridently. Together Yale and Woods Hole evoked a passion in me for a very broad range of sciences, although with little special focus. I learned that success in science would be to trace all natural phenomena back to the laws of physics and chemistry. Woods Hole may have been the “school” that contributed most to my appreciation of modern life sciences and a life of science. During this time I grew up physically, became self-confident, brash, and an outspoken “young Turk.”

The Rockefeller University: A Community of Scholars

Early in my senior year at Yale, Ed Boell told me he had written a letter to the Rockefeller Institute in New York to recommend me for graduate studies. I had not heard of it before (!), but as soon as I had my interview, there was no point in looking elsewhere. The interview began with the Dean, Frank Brink, Jr., who asked me what book I was carrying to read on the train. It was Biophysical Chemistry by John Edsall and Jeffries Wyman. I asked him if he knew of it. Fortunately, that book and its authors were well regarded at Rockefeller. I visited with Philip Siekevitz and Paul Weiss, brashly telling them my instant opinions on their specialties. Most of my day was spent shadowing Detlev Bronk, a biophysicist, the President of the University, and simultaneously the President of the U.S. National Academy of Sciences, ex-president of Johns Hopkins, and ex-Chairman of the National Research Council. He was fielding telephone calls from David Rockefeller, inspecting many parts of his campus, talking with his employees, and impressing his interviewee with his philosophy and scope. All of science has intellectual unity. Science is an international community of scholars.

Scientists should engage in science policy and public service. Bronk was proud that there was no need for or dependence on federal support for research at his elite institution. At the end he invited me to join their community of scholars. Irresistible! Dr. Bronk considered recommendation letters only from people he knew well. By this method in 1962 he selected 21 students for my class, six of whom eventually became members of the National Academy of Sciences: Wyatt W. Anderson, Anthony Cerami, Harvey F. Lodish, David D. Sabatini, Daniel W. Stroock, and me. It must be rare when such a collection of future scientists is so successfully chosen from undergraduate applicants!

Since 1901, the Rockefeller Institute for Medical Research had been at the forefront of what is now called biomedical research, conquering major diseases and greatly advancing the basic life sciences. In 1955, a graduate program was begun under the new President Bronk. The name was shortened first to The Rockefeller Institute and in 1965 to The Rockefeller University. In our time, there were many more faculty than students, the idea of formal teaching was unfamiliar to them, and our curriculum was self-determined. Everything was done with a style that eventually drew down the endowment. The students were pampered, made to feel like privileged scholars, and provided with an apparently unlimited budget for whatever we wanted to investigate. Faculty and students ate in the formal dining room, coats and ties required. At lunch the linear tables held 30 people, and you never knew whom you might sit down next to—sometimes even the President. I think our stipend was $2000 with an additional $1000 for intellectual and cultural enrichment.

I continued to read broadly from the weekly table of new journals, under the watchful eye of Antoine Lavoisier on the library wall. His stunning, life-sized seated portrait with Mme. Lavoisier standing by him painted by Jacques Louis David now hangs in the Metropolitan Museum of Art. Friday afternoon lectures provided a role model in how to present a scientific story. They were so grand and of such wide scope that it was hard to imagine ever achieving so much in a life’s work. Eclectic course offerings I took were extraordinary: cell biology (George E. Palade, Siekevitz, David J. L. Luck), a tutorial in biochemistry (Alfred E. Mirsky), chemical kinetics (David Mauzerall), theoretical organic chemistry and enzymology (Daniel E. Koshland), topics in physical chemistry including hyperchromicity of DNA, helix-coil transitions, properties of water, the hydrophobic effect, and regular solution theory (Walter J. Kauzmann visiting from Princeton), osmosis theory, electrochemistry, and the Nernst-Planck diffusion regime (Alexander Mauro), electricity and magnetism and thermodynamics (George E. Uhlenbeck), neurophysiology (Victor J. Wilson), Egyptian hieroglyphics (Samuel A. Goudsmit), humanism (Ludwig Edelstein), and more.

Among my own class I became especially close to Harvey F. Lodish, David I. Hirsh, Daniel W. Stroock, Alan B. Steinbach, and Alan M. Kapuler (who had initiated our Biology Club at Yale). Harvey had a B. S. in chemistry from Kenyon College. Within the first week, I declared that he needed to know some biology. “Fine,” he said, “do you have something I can read?” I gave him the 900-page Histology by Ham and Leeson. The next day he came back with the book, saying, “That was OK, do you have another?” Thus, he began to prepare himself for writing Molecular Cell Biology 23 years later. In my first month at Rockefeller, I met Frederick A. Dodge, in the dining room. He was a very senior graduate student. For his thesis he had worked with Bernhard Frankenhaeuser in Stockholm to develop a voltage clamp for single nodes of Ranvier of frog myelinated nerve fibers (Dodge and Frankenhaeuser, 1958, 1959) and then set it up in New York for further experiments. This was the first full duplication of the Hodgkin-Huxley program of separation of ionic currents, model fitting, and simulation of the action potential for the vertebrate phylum—indeed for anything other than the original squid giant axon. I could understand what he was telling me at dinner about the nodal Na⁺ and K⁺ currents, but despite his invitation to come up and see the lab, I was reluctant to get involved because of the lack of confidence in such model-oriented approaches I had absorbed from my Yale mentors. Other senior students at the time included Alan Finkelstein, David L. Baltimore, and Charles F. Stevens. I remember an hour-long heated dispute between Siekevitz and Baltimore in our cell biology course on whether the newly proposed concept of polyribosomes was just an artifact (Siekevitz) or correct (Baltimore). Chuck Stevens kindly transferred custody of the students’ analog computer to me and showed me how to use it. That was just the tool I needed to complete the modeling of Drosophila crossveins, so I took it to Woods Hole the next summer and could complete that project with Roger Milkman.

Technology

Technology plays a pivotal part in biophysical experiments. We used to say that if you could buy the apparatus commercially, the experiment already had been done. In 1960, while at Yale, I took a free course in how to use their digital computer, a whole building by itself full of the vacuum-tube 709 computer. The International Business Machines Corporation taught us for 3 hours each night, three nights in a row, a language they called FORTRAN. The 709 offered the first FORTRAN compiler. We each could enter a program on punch cards in a 5-minute time slot for practice. My program was on the order of: A = 1, B = 3, C = A + B, PRINT C, with appropriate formatting. After the 9 hours of instruction and debugging this program, I felt like an expert in computing! In 1963 at Rockefeller, I wandered into one of the lab rooms of H. Keffer Hartline (Nobel 1967 for lateral inhibition in the Limulus eye) where he had just installed the Rockefeller University’s first digital computer, a transistorized Control Data CDC 160A. It boasted a massive desk-like console with many associated racks of equipment, a 13-μs add time, 32K (total) magnetic core memory in an external box with noisy fans, and “fully solid state.” Their idea was to make it into a laboratory computer for recording on-line and analyzing responses of the Limulus eye. The electronics department was busy designing interface modules for analog-to-digital (A-D) and digital-to-analog (D-A) conversion, which could not be purchased off the shelf as they can today. Fred Dodge was also there. By now he was Dr. Dodge and an employee of IBM, with an affiliation with the Hartline lab. He and Bruce W. Knight were beginning to construct software that would eventually determine the transfer functions for eye responses to sinusoidal inputs of light or current. However, although Fred had programmed the nodal Hodgkin-Huxley calculations of his thesis using SICOM, a machine language for an IBM 650 drum computer at Columbia University, neither of them knew how to use the FORTRAN II compiler that had come with the CDC machine. I sat down and wrote the cross-correlations for them on the spot after they had explained the math to me.

For over a year at Rockefeller I had looked around at possibilities to study membranes, including electron microscopy of membrane complement lysis and the kinetics of the then new Na⁺-K⁺ ATPase activity. Finally Alex Mauro invited me to come to his lab to study the effect of D₂O on action potential propagation in the lobster circumesophageal giant axons. This was formally the President’s lab of biophysics that comprised Bronk, his Dean Brink, his Associate Dean Clarence M. Connelly (none of whom had research programs), Alex Mauro, and W. Paul Hurlbut. Alex had worked on a wide range of phenomena: muscle satellite cells (he discovered them), black widow spider venom, the Limulus ventral eye, theory of osmosis and filtration, Nernst-Planck theory, and cardiac pacemakers. Alan Steinbach joined the same lab and we were lab mates doing our theses in the same room. On the same floor was the lab of Hartline and Floyd Ratliff, studying lateral inhibition and photon responses of the Limulus lateral eye, as well as the University Electronics Department.

Alex Mauro was a very enthusiastic presence in the President’s lab with strong outspoken liberal emotions about the escalating Vietnam conflict, the civil rights movement, and social injustice. But he was not so interested in deciding what the research questions would be or in the practical aspects of setting up a lobster experiment. The whole lab was low key, and little lab research was going on. I am forever indebted to Fred Dodge for helping me get going several times that year, as he did for a generation of biophysics Ph.D. students. With the Faraday cage and extracellular wires or intracellular microelectrodes, D₂O slowed the propagation of the action potential, and the nearly intact lobsters accumulating in the freezer made wonderful bouillabaisse parties. I had started recording from nerve, but it was not clear where this project could lead.

By 1964 I had to take my oral qualifying exam, one of the few formal requirements. I don’t remember all the questions or even all the examiners, but I do remember Zanvil A. Cohn asking me to explain the functions of the liver and David Mauzerall asking for a formulation of enzyme kinetics in terms of irreversible thermodynamics. All this went well enough, but fortunately the committee determined that if I was hoping to be a biophysicist I had better know more about electronics. Although I could handle Ohm’s Law and the simplest cable equation, I had regarded electronics as in the realm of engineers and not for pure basic scientists like myself. Alex Mauro was assigned to rectify my deficit. He had worked at General Electric during World War II, and he took a book from his shelf to get me up to speed. It was a 500-page tome called The Pentode on the metal alloys, grid spacings, electron-cloud space-charge regions, optimal filling gases, and the ideal glass envelope for this type of high-gain vacuum tube, in short everything one might need to manufacture and design new ones. I did read this book from GE but still did not gain practical facility with electronics. Fortunately my real mentor and role model in this again was Fred Dodge. As I began to use them, the old oscilloscopes, stimulators, and amplifiers would break down, and Fred would pull them out, show me the circuit diagram, trace the waveforms until we found the problem, and then replace the part. I began to study circuit diagrams for my instruments and eventually was able to understand for example what every resistor, capacitor, and vacuum tube was doing in my Tektronix 565 dual-beam oscilloscope. I also became skilled in using the new transistorized operational amplifiers that began to appear on the market. By 1966 I had to use the soldering iron alone. Fred left for Bernard Katz’s lab in London (Nobel, 1970 for neuromuscular transmission) for postdoctoral study of the effects of low calcium on the endplate potential with Rami Rahamimoff. Despite this valuable practical education, I regret that I never acquired any depth in AC-circuit analysis or in de novo design of transistor circuits in the way that I later admired in Wolfgang Nonner and Fred Sigworth. Although my father was a mathematician who later wrote textbooks on complex variables and differential equations, I never gained adequate facility with these tools to read typical electrical engineering books.

The year 1964 was pivotal for me in yet another way. I married Merrill Burr, who was a couple of classes ahead of me at Rockefeller finishing her thesis work on chymotrypsin as Dan Koshland’s first graduate student. Ours has been a lasting and happy union. Shortly before we married I flew Icelandic Air to Luxemburg and hitchhiked alone to and around Greece visiting Classic Greek, Mycenaean, and Minoan archeological sites for a month—my last excursion as a bachelor.

After my oral exam, I asked Fred Dodge if I could learn to voltage clamp the node of Ranvier, the technique of Dodge and Frankenhaeuser. Maybe I could try modification of nerve functions with a more mechanistic readout. That was fun. A single myelinated fiber had to be teased from the others in a frog sciatic nerve trunk, sealed into a multicompartment chamber with Vaseline across partitions, and, when addressed with a rack full of vacuum tubes and power supplies, produced beautiful ionic current traces on the oscilloscope. The dissection with fine needles was difficult, since the largest frog nerve fibers were only 20 μm in diameter and could not be touched directly or stretched. Although I used that frog preparation in sole-authored papers for 15 years, I never achieved the manual skill shown, for example, by Robert Stämpfli or Wolfgang Nonner, whom I visited later in Homburg (Saar), Germany. Retrospectively, my talents seemed rather to be in recognizing and interpreting new phenomena, developing logical arguments and unifying hypotheses, and synthesizing novel stories simply and transparently.

Analysis of voltage-clamp records turned out to be slow. The oscilloscope traces were photographed by a Grass camera on long rolls of 35 mm film. They were projected from a photographic enlarger onto graph paper and traced by pencil. Then points were read off, baselines subtracted, currents separated, values transformed, and replotted onto semi-logarithmic paper to fit time constants. I wasn’t patient enough to spend a week analyzing an hour of recording and sought a faster way. By early 1965 Fred Dodge had the idea that Hartline’s computer might help. He taught me to program data sampling with hand-coded machine language (there seemed to be no macroassembler!), and this code was linked with a FORTRAN section. The code could not control the experiment, but it sampled sweeps online, synchronized by pulses from a ganged bevy of vacuum-tube Tektronix pulse generators. Initially the raw data had to be saved on long rolls of punched paper tapes, but later in the year the arrival of a large digital magnetic tape drive (as big as a closet) made possible a more compact and secure format. Dr. Hartline very generously conceded Saturdays for this activity unrelated to his lab. I could wheel my full rack of equipment and the temperature bath down to the Hartline lab and plug in on weekends. For my thesis and the next 15 years, all my personal experiments were done on Saturdays, and I still am in my office on many Saturdays. I got used to the full day of quiet that allowed me to focus entirely on doing experiments without interruption. Off-line analysis of the current records using a FORTRAN program I wrote could be done at lunch times or in evenings of other days when the computer was not in use. This was the first time that any voltage-clamp experiment was recorded and analyzed by a digital computer.

Graduate Research and Ion Channels

It is hard to reconstruct your state of thinking 45 years ago, but some notion comes from looking at my lab notebook. Once I had the new relatively highthroughput online system operational, my very first Saturday experiments (June 1965) before going to the Grundfest lab for the summer involved lidocaine, tetrodotoxin, and chlorpromazine, and in September, immediately after returning from Woods Hole, it was tetraethylammonium ion (TEA).

With tetrodotoxin and TEA it was clear at once that one drug was selective against Na⁺ currents and the other against K⁺ currents. While getting ready to do experiments, I had taken Koshland’s enzymology course, saw many attempts to identify residues in enzyme active sites, and began reading books about structure–activity relations for antagonists, partial agonists, and full agonists of various receptors. It seemed natural to suppose that the Na⁺ and K⁺ carrying systems (as Hodgkin and Huxley called them) of axons might also be investigated using the concepts that had been developed by enzymologists and pharmacologists. A question that no one at Rockefeller seemed to have any opinion on (or interest in?) was whether the ions were passing through pores and, if so, whether Na⁺ and K⁺ used the same pore or separate ones. Without any evidence, I was cockily sure that it was pores and that there were two kinds, which should be called Na⁺ and K⁺ channels. This would be the hypothesis of my work. Clay M. Armstrong, then a postdoc at the National Institutes of Health (NIH) with Kenneth S. Cole, already had been thinking along exactly the same lines; he began a beautiful series of papers on K⁺ channel block by axoplasmic TEA (Armstrong, 1966, 1968, 1969, 1971). We thought the same way and fed on each others ideas. Many others thought differently. For example, American biophysicists had published articles proposing that ions pass through cracks in the membrane, that K⁺-carrying inward rectifiers are carriers, or that Na⁺ and K⁺ pass through a single pore that goes through a graded change in diameter and selectivity during the action potential. In 1966 or 1967 at the Biophysical Society meeting, there was a “discussion-only” session on axon electrophysiology. Toshio Narahashi, the chair, announced that as a ground rule one could not use the word channel in this discussion. Clay and I objected (our abstracts even contained the word in the title). Finally, Narahashi conceded that channel could be used provided that no mechanistic connotation was implied! For at least 10 more years some people used the word channel even if they rejected the pore hypothesis.

For the thesis, I use voltage clamp to screen a very large number of the agents that had been reported to change the excitability or shape of action potentials and selected those that were best suited to argue for the separatechannel hypothesis (Hille, 1966, 1967, 1968a, 1968b). Tetrodotoxin and saxitoxin (obtained from Ft. Detrick) blocked Na⁺ currents selectively. My 1966 Nature paper states, “The sodium channels of the nerve are closed or clogged individually by the binding of the anaesthetic molecule to a complementary structure of the channel (p. 1222).” TEA and analogs blocked K⁺ currents selectively. TTX, STX, and TEA blocked as though entering the pore and binding to a single binding site that fully eliminated an aliquot of conductance rather than reducing current by gradual changes of gating. Raised extracellular Ca²⁺ shifted the gating of Na⁺ channels without changing K⁺ channel block by TEA, and adding the insecticide DDT seemed to keep Na⁺ channels open after they had opened (“foot-in-the-door” hypothesis) without changing K⁺ channel sensitivity to TEA. Acidic solutions blocked Na⁺ channels as if titrating a negatively charged acid group with a pKa of 5.2 that was essential both for conduction of ions and for the binding of TTX. Such a negative charge might attract permeating Na⁺ ions and would repel any anions from the pore. Twenty-five years later the amino acid sequences of voltage-gated Na⁺ channels were shown to have several acidic residues in the putative selectivity filter region, whose neutralization decreased TTX binding and ionic selectivity (e.g., Terlau et al., 1991). In 2010, we still await structural work to show how they are arrayed in three dimensions.

These well-cited thesis papers were written with little input or oversight from others. In retrospect it is evident that they should have been critiqued locally first and that they were recklessly submitted without the normal number of replications and with no indication of reliability. Fortunately the phenomena seem to have been mostly correct. On reading my thesis (1967) David Mauzerall (physical chemist) said that it was “typical of biophysicists” to think that every experiment will be the same as the last one so that statistics were not needed. Even looking back at the Hodgkin-Huxley papers, one sees that although they present tables with the results of several axons, only sometimes is there a mean, and there are no “statistics.” I have been fortunate in that once my lab got into experiments where we had to compare means, my students and postdocs brought enough basic statistical background to know how to do it.

Alex Mauro knew George Camougis and Bertil H. Takman of Astra Pharmaceuticals, the makers of lidocaine. One day he drove his two students, Alan Steinbach and me, to Worcester, Massachusetts, to visit Astra. This started a long useful relationship with Bertil Takman, who knew a vast array of compounds and analogs that had been explored in their studies of local anesthetic action and development. He had a fund of ideas that moved our work forward 10 years later. In 1966 he introduced us, for example, to membrane impermeant QX-314 that is now widely used to silence single neurons from the inside. It gave me respect for industrial research and medicinal chemistry.

My thesis papers and my thesis lab began my long happy association with the Journal of General Physiology (JGP). It was owned by the Rockefeller University, so President Bronk appointed the editor who usually sat in Bronk’s lab where I worked. Earlier editors had included Bronk, Brink, and Mirsky. While I was there, it was Associate Dean Clarence Connelly (1961– 1964), J. Woodland Hastings (1964–1966) at Harvard, followed by Paul F. Cranefield (1966–1995). Connelly was very sensitive to American usage. I still follow his preference that the present tense rather than the future tense be used to refer to a later part of a text (i.e., avoid the expression, this will be explained later) and his impression that “both” is greatly overused (it is meaningless to say, both A and B are identical).

In spring 1967 I defended my thesis and concluded with the following words, taken verbatim from my written lecture notes:

The different permeability mechanisms can be called the Na channels, the K channels, and the leakage channels. The sodium and potassium channels of nerves must be special structures inserted in the matrix of the cell membrane that provide diffusion paths tailored for specific ions. Almost every example of molecular specificity in biology involves the interaction of a protein with something. We have come to know that proteins are more versatile than other macromolecules in the variety of conformations that they may assume and in the kind of chemical moieties they offer. Their production is intimately tied to the genetic material and therefore their structure is most directly subject to the actions of natural selection and their synthesis most directly responsive to the activity of genes. I feel that the changes of ionic permeability of nerve membranes reflect the conformation changes of proteins that form the diffusion channels through the membrane. Somewhere in these channels, various amino acids are gathered in a constriction that is able to distinguish between Na⁺ and K⁺ ions. Biochemists could expect to find these [protein] molecules in the axoplasm and surface membranes. . . . . It would probably be feasible to use TTX binding as an assay for the Na channel proteins.

This was the channel manifesto that Clay and I were advancing each in our own way. Eleven years later, the first Na⁺ channel subunit was purified from electric organ on the basis of TTX binding (Agnew et al., 1978). In my thesis lecture I had used as one argument in favor of pores that the fluxes of Na⁺ in Na⁺ channels show no saturation and behave linearly, the independence principle of Hodgkin and Huxley (1952). Presciently, Fritz A. Lipmann (1953 Nobel for coenzyme A) asserted in the question period that, like enzymes, pores must also be able to saturate.

Finding a Job

During my last year, President Bronk arranged that I would be going to Cambridge, England, to work with Alan L. Hodgkin (1963 Nobel laureate for the basis of nerve action potentials). I was awarded a Helen Hay Whitney Fellowship for that. Hodgkin said he would tell me the research problem after I was there. The fellowship application asked how my proposed work would help in connective tissue diseases. I answered that connective tissues must have cell membranes and the squid giant axon was the best place to study them.

Because I would be out of the country for a year, I felt that it would be best to find a faculty job to return to at the end. My mentors arranged several visits. At Harvard Biology (George Wald and Keith R. Porter) I realized I would need more infrastructure (shops) than they had available. At Duke Zoology (Knut Schmidt-Nielsen) the dinner conversation with faculty and wives focused on whether any of them would be comfortable with inviting a black guest to dine in their house. I had a marathon West Coast tour visiting my mentors’ friends: UCSD (Robert B. Livingston and Theodore H. Bullock), UCLA (Wilfried F. Mommaerts), Berkeley (Robert I. Macey), University of Washington Seattle (Chuck Stevens, J. Walter Woodbury, Harry D. Patton), and my brother-in-law’s department of Biology at Simon Fraser University in Burnaby, Canada. UCSD was going to start its first medical class in the next year and seemed like a gamble since they had no idea what teaching responsibilities their faculty would have or even what departmental structure. I really did want to continue using an online computer connection to my experiments, and in 1967 a beginner could not imagine having one of his own. Mommaerts, Chair of Physiology at UCLA, was very charming and courted me then and several times afterwards; I asked if they had an online computer. They did, and he took me on a 30-minute hunt and finally located a dusty card-reader terminal in a dark corridor. Seattle’s Department of Physiology and Biophysics seemed the best. There already were excellent membrane biophysicists like Woodbury and Stevens. They had a machine shop, an electronics shop, a vigorous graduate program, and above all—the trump card—an online computer facility connected to physiological laboratories, and lots of computer savvy, all within the department. Furthermore, the Pacific Northwest seemed great, and Merrill, who had been there years before for a summer, thought it ideal. She was right. I was 26 and still had not defended my thesis, but I had a job!

Most institutions on this visit had said that of course they didn’t have jobs but I could visit anyway. Happily, jobs appeared. This was before job openings had to be advertised, and instead Chairs just would go to their dean after some interesting candidate had been identified—the old-boy network. Of all the places I visited, only Simon Fraser University in Canada offered to pay a portion of the airfare for this big trip. The University of Washington did not. When I was back in New York with job in hand, Harry Grundfest accosted me, “No! You are not going to that intellectual desert!” He was so wrong.

Postdoctoral Work in Plymouth

Merrill finished her postdoc with Severo Ochoa at NYU (determining the last codon for termination and purifying the first three bacterial initiation factors), I submitted the last two manuscripts of my thesis publications to the Editor of the Journal of General Physiology in the next room, and we flew to England. It was only my third airplane trip. Alan Hodgkin told me that my task would be to go to Plymouth to check out Ichiji Tasaki’s reports that squid axons could make action potentials in bathing media containing elevated Ca²⁺ and no Na⁺. They would be calcium action potentials. He would visit Plymouth only infrequently when he could get time away from his Cambridge duties, but he would be working on another project. Remembering that Tasaki’s axons had been internally perfused with an unusual medium containing 5 mM CsF and pronase dissolved in glycerol and water, I asked him what I would need for internal perfusion. He said I would not be perfusing. I asked then what kind of voltage clamp I should use to analyze the phenomenon. He said I would not be voltage clamping (indeed, they had no voltage clamp amplifiers) and that Mr. Cook, his very versatile assistant, would make a pair of cathode followers to measure potentials. When Mr. Cook laid out the parts for the followers, a full rack, several panels, four pentode vacuum tubes, four 45-V, four 9-V, and two 6-V batteries, and a collection of resistors, potentiometers, and cables, I commented that I knew how to make followers using the new field effect transistors (FETs) that would be no larger than your thumb. Mr. Cook responded that this circuit had been designed by Professor Bernhard Frankenhaeuser of Stockholm and could not be improved upon. I had much to learn about being an American postdoc in Professor Hodgkin’s lab.

Some of the faculty I eventually interacted with at Cambridge included Richard Adrian (skeletal muscle excitation-contraction coupling, later to be Lord Adrian, son of Edgar Lord Adrian), Ian M. Glynn (Na⁺/K⁺ ATPase), and Denis A. Haydon (lipid bilayers and gramicidin single channels). In the Hodgkin lab room in Cambridge where I was given a place to sit temporarily, there was a Faraday cage holding the three-microelectrode muscle fiber voltage clamp that had been used for the experiments of Adrian, Chandler, and Hodgkin (1970). W. Knox Chandler was at the next desk. He had been finishing the muscle clamp work that summer, and earlier (1962–1965) he had done perfused squid axon work with Hans Meves as Hodgkin postdocs. He was now projecting voltage-clamp data from films onto graph paper to take them back to New Haven for analysis on Yale’s 7090 (solid state now) computer. He came back each summer for this, as the films could not leave Cambridge. Mordecai P. Blaustein was in Hodgkin’s lab preparing for his second postdoctoral Plymouth season to finish characterizing the Na⁺-Ca²⁺ exchange process of the giant axon. In that banner year for Ca²⁺ transport, the Na⁺-Ca²⁺ exchanger was being discovered in squid in Plymouth (Baker et al., 1969) and in cardiac muscle in Berne (Reuter and Seitz, 1968), and the plasma membrane Ca²⁺ ATPase was being discovered in red blood cells in Berne (Schatzmann and Vincenzi, 1969). Note that in those days authors were listed alphabetically on articles in the Journal of Physiology (London); men usually used their initials, whereas women were required to use their full names! Hodgkin’s lab then was rounded out by Shigehiro Nakajima (visiting research fellow) and Peter Stanfield (research student), both working with electrical properties of skeletal muscle fibers.

In October, the squid-axon contingent moved to the Plymouth Marine Laboratory in Devon. There, when the weather permitted, commercial fisherman would bring a few squid for the scientists to the dock around 5 PM. They had already been decapitated and stored in Dewar flasks filled with sea-water ice slush, so they had to be dissected at once. The scientists worked until the morning. The squid were few, and it was evident when Hodgkin allocated them that the Hodgkin-Blaustein Na⁺-Ca²⁺ exchange project had very much higher priority than mine. When I did get one, it was also made clear that I should not bother them during their pressing work to learn what to do next. Fortunately in a few days, Trevor Shaw came from London and he kindly showed me the dissection. I was to use a plastic vertical chamber (made from the design of Huxley) and the double-spiral wire axial electrode. The axon hung vertically from a glass cannula tied into one end, and the long intracellular electrode was threaded through the cannula and down the fiber axis without touching the membrane. Making this delicate electrode could take days, winding two stiff wires in a spiral along a very thin glass rod and tacking them down all along with tiny dabs of shellac under a microscope. Fortunately a clever jig with a lathe-like screw held the parts and advanced the rod appropriately during construction. Despite all efforts, the axons made no action potentials in high-calcium solutions. That seemed understandable to me since they were not perfused with Tasaki’s exotic intracellular medium, which would eliminate all K⁺ currents by Cs⁺ block, chelate all Ca²⁺ by F–, enormously shift the voltage dependence of the Na⁺ channels and any Ca²⁺ channels by low ionic strength to allow excitability, and, we know now, remove inactivation from Ca²⁺-permeable Na⁺ channels by proteolysis.

What to do? The only way I knew to analyze the state of the membrane would be to voltage clamp. The next time Hodgkin visited Plymouth, I asked him if I could use a little of the $1000 he got with my fellowship to buy three operational amplifiers to make a clamp. They would cost £20 each (about 100 times what they cost today). He responded that it would be a bad investment: Someone had given the lab an operational amplifier some years before, and they “had never found a use for it.” I was bailed out again by Trevor Shaw when he came a few days later. Trevor was a very dear person. The Plymouth Marine Lab, of which he was a trustee, might be able to buy three amplifiers if I could convince him that someone else there could use them after I was done. It became apparent that almost no one in these circles, even their electronics technicians in Cambridge, knew what an operational amplifier was. As there were no squid, I gave Trevor a full evening tutorial, and he arranged for the purchase. I set out to construct the circuit. The Plymouth Lab had no electronics shop, but after World War II they were given a collection of obsolete radar sets that could be used to scavenge parts. (Hodgkin and Huxley had worked in radar design during the war, as had many other future electrophysiologists of that generation.) The resistors were as large as my little finger and used a different version of color coding from the convention I knew, but I could identify some. For the lack of a chassis, I hammered two rows of nails into a wooden board, a miniature Parthenon, and soldered the enormous components to their heads. There were no power supplies, so power was from batteries. It was grotesque, but it worked.

We had a period of gales when the fishing boats could not go out. Hodgkin had come and, looking for something to do while we waited, he asked to read the copy of my thesis that I had brought. It was 175 pages with a lot of discussion of channel ideas and speculations on the mechanisms of action of the many drugs I had tried. It also included some theoretical sections, including a calculation of ion fluxes and conductance through pores of assumed geometry as in the appendix of Hille (1968a). After reading, he flattered me by proposing that I should write a review article. I said I thought that I should gain more scientific maturity first, but later I learned that he must have passed the idea along to Denis Noble at Oxford. Another time Hodgkin described how exasperating it was to train American postdocs who take his good research ideas back to the States. Although I was feeling blamed, what he meant was that the United Kingdom had no postdoctoral support system. Had there been one, he could have trained 20 British postdocs during his career, and his good ideas would have taken root in the British Isles, enriching British science, a very valid argument for a change in national policy. During gales, I also wrote my first NIH R01 research grant to support my future lab in Seattle. I had no examples to work from, and there were no experienced Americans in Plymouth to give advice. England was going through a period of austerity, so when I asked Hodgkin about requesting an oscilloscope on my grant, he said he had thought about asking for one himself 5 years before, but then had thought better of it since perhaps someone else would be more deserving. In the end, I sent in a request for 3 years of support at a modest $18,000, $4000, and $4000, respectively. In those days the State of Washington paid 100% of our salaries and it was considered inappropriate to ask for salary on our grants.

Another American postdoc using squid giant axons that season was Lawrence B. Cohen. He worked for Richard Darwin Keynes (then Director of Babraham Animal Research Institute, just outside Cambridge). Much of Keynes’s life research had pursued the hypothesis that beyond the electricity that Hodgkin and Huxley had analyzed so successfully, one should be able to learn about mechanisms of excitability from other physical signals such as isotope fluxes, thermal changes, and light. He had obtained very important isotope flux results, including showing the quantity of Na⁺ and K⁺ ions passing the membrane during the action potential (Keynes, 1951), measuring single filing of K⁺ ions in K⁺ channels (Hodgkin and Keynes, 1955), and discovering basic properties of the Na⁺-pump (e.g. Caldwell et al., 1960). In Babraham, Larry Cohen had detected various optical signals in excited nerve bundles, so Richard had sent him to Plymouth to see whether the signals correlated with the action potential in squid giant axons. As Larry had done his thesis measuring the nucleotide-dependent viscosity of actin solutions, he was not yet at ease with electrophysiology or electronics. Hearing that I had made a voltage clamp and that my project was not going well, Richard Keynes persuaded Hodgkin (his thesis supervisor many years before) to let me join Larry’s optical project. We managed to voltage clamp the axon under crossed polarizers and found that the fast membrane birefringence signals tracked the changes of membrane potential within microseconds and almost linearly (Cohen et al., 1968). An added bonus was that Richard was very skilled at dissecting axons and threading the electrode. Whenever he was in Plymouth, we could save our energies for the midnight experiments. Richard had a facility for falling asleep (naps) at any time and in any place, and Larry and I often connected signal wires and passed instruments across his large seated frame after Richard fell asleep late at night with his feet up on the counter, effectively bisecting our tiny hushed laboratory cubicle. Once when we were alone, Larry confided that he believed that the $7000 American postdoctoral stipend we were each receiving was more than the pay of our famous British mentors.

Postdoctoral Work in Babraham

Merrill was very pregnant with our first child, and some weeks before the squid season was over we had to return to Cambridge to get settled before the birth. As our move approached, I asked Hodgkin if I might try my hand at the three-electrode muscle clamp in his laboratory. He said no, that nobody could touch the unused setup until the papers were published (3 years later). He announced that there was no laboratory space for me in Cambridge and I had better do a theoretical problem. Richard Keynes soon stepped in and proposed that I could continue to work with Larry at Babraham, which I did.

Back in Cambridge, it seemed prudent to get a telephone connection for Merrill to contact me from our row house in case labor was approaching. However, the authorities said that there were no extra phone lines in our area (a 20-minute walk from the Physiological Laboratory). If we were both medical doctors, we could take the phone from the flat down the street where there was only one doctor. Otherwise we would have to use the phone box in the next block like everyone else. Merrill tried that phone box and, finding the tones unfamiliar, she asked a passing 20-year-old to tell her if this was a ring tone or a busy signal. The passer-by apologized that she had never used a telephone and did not know. Although milk was delivered every day to our doorstep, we felt it would be useful to have a refrigerator in the kitchen.

The landlady didn’t think there could be a reason to have one but finally agreed that if we bought a small under-the-counter fridge, she would buy it from us when we left. Erik Darwin Hille arrived on a snowy night in early January. Two weeks later, Merrill started her postdoctoral work in chick bone development with Dame Honor B. Fell, who directed the Strangeways Laboratory.

While waiting for Larry to return from Plymouth I decided to read more about optics to be sure we understood what we were doing. Optics books were shelved in the Physics Library. First I had to write a letter to Professor Sir Neville Mott, the respected Chair of Physics (1977 Nobel laureate), to request his kind permission to enter. After a few days, a formal letter of entry arrived. I enjoyed reading physics again and came away with clearer criteria for our experiments.

In the next 8 months, Larry and I completed several studies on optical changes in the electric eel electric organ and in crab nerves. Electric eels were large and very costly. They had to be obtained through shady characters in the Amazon basin, who wanted prepayment and did not always deliver. In Grundfest’s lab I had seen Electrophorus used for many days by cutting a piece off the tail and cauterizing repeatedly, but in England the animal use laws required quickly dispatching the 150 cm fish before use. The tissue survived for only a few more hours. After we had used the available animals, Richard declared an end to the experiments, but one day A.V. Hill (of the Hill equation 1910, Nobel Prize1922) visited from London to see what was going on. He heard us lament that we had to stop our work since Richard did not want to buy more electric eels. Solemnly he pronounced that one should never change experimental animals in the middle of a successful series of experiments, and Richard was forced to buy us more in deference to this great hero of physiology—his uncle.

We characterized small changes in birefringence and light scattering during the action potential. Eventually I was discouraged to find that the optical signals did not seem a direct way to learn about the conductance mechanisms or ion channels of excitable membranes. Larry, on the other hand, devoted the rest of his career to light. Later at Yale, he exploited dyes to increase absorbance and fluorescence signals by up to six orders of magnitude, and by now it is common to use optical monitors of membrane potential and calcium in living animals and to use light to stimulate or silence neurons in the nervous system.

Richard Keynes extracted the $1000 that the Helen Hay Whitney Foundation had given Alan Hodgkin for expenses and kindly allowed me to take a trip. I made a pilgrimage to the node of Ranvier laboratories. At the University of Saarland (Homburg), Robert Stämpfli was a grandfather of the frog node of Ranvier. The Huxley-Stämpfli papers (1948–1951) and earlier ones from Ichiji Tasaki (1940–1944) had established saltatory conduction in brilliant experiments with single myelinated nerve. Stämpfli was an extraordinary dissector. Wolfgang Nonner, still a medical student, was developing compact transistorized amplifiers and a new method for voltage clamping single nodes (Nonner, 1969; to this day the ultimate). He had realized that the impedance properties of the preparation required frequencygain characteristics of the amplifier that increased at high frequency, quite the opposite from the simple roll-off of contemporary operational amplifiers. In Kiel, Hans Meves had just become the Professor, Werner Ulbricht was measuring the onand off-kinetics of TTX and TEA and the actions of veratridine, and I got to know Werner Vogel, who had just finished his Ph.D. In Stockholm, Bernhard Frankenhaeuser was low key and more interested in how to design a stimulator than in thinking about ion channels. The labs in Homburg and Kiel were warm and friendly places that I visited many times afterward.

A Beginning Faculty Member

In September 1968, we left our postdoctoral work after a year in England and flew to Seattle. The agreement with Harry Patton at the University of Washington was that my salary would be $14,000, a lab room would be found, I would teach like everyone else after a short grace period, and, for startup equipment, I could rummage in a room full of unused old Tektronix pulse generators and oscilloscopes. No special start-up funds were provided in those days. When I arrived, the lab room was not yet available (that happens to everyone), but I found in my new mailbox an envelope saying that my NIH grant was awarded. The NIH has been a steadfast source of support. That same grant continues now in its 42nd year. We bought one house, two cars, and a piano and were broke. Three months later our second son, Jon Trygve Hille, was born. Merrill soon started her third postdoctoral fellowship, now in echinoderm developmental biology. We were fully engaged. I was still 27.

The Department of Physiology and Biophysics was chaired by Patton, who had taken over from Theodore C. Ruch, the founding (1946) Chair. Ruch had become the first Director of the Regional Primate Center in the next wing. The department had special strength in cardiovascular physiology, neurophysiology, and biophysical thinking. The orientation was classical. About six labs experimented on anesthetized cats (central nervous system), four on anesthetized dogs (cardiovascular and respiratory), and four on awake monkeys in the Primate Center (central nervous system). Most of the faculty were contributors to the widely used textbook, Ruch and Patton, Physiology and Biophysics (later called Textbook of Physiology). In addition to teaching medical, dental, nursing, and pharmacy students, the department offered an intensive 2-year across-the-board physiology series for our graduate students. Ten new graduate students arriving each year and all the more senior ones were supported by five generous departmental training grants from the NIH. All students were to be able to teach every aspect of physiology “without embarrassing us.” There was a foreign language requirement for the Ph.D., which for some years I administered. By today’s standards, this was a large, demanding, old-school comprehensive disciplinary degree program that was extraordinarily successful.

The department had and continues to have an exceptionally friendly and supportive attitude. When I came, many of the faculty had been students or postdocs in the department. Other than my Chair, three faculty members were of greatest importance to me then. Chuck Stevens was a kindred spirit, turning then productively from neurophysiology to full-fledged biophysics of isolated neurons and frog neuromuscular junction under voltage clamp. He was pioneering fluctuation analysis with power spectra, making the first full Hodgkin-Huxley description of a spiking cell body, and determining the voltage-dependent open time of the nicotinic acetylcholine receptors of the neuromuscular junction. His tiny lab was full of excellent students and postdocs thinking well. Walter Woodbury was the senior membrane biophysicist steeped in the lore of impedance measurements (Cole), cables (Hodgkin and Ruston), and squid action potentials (Hodgkin and Huxley). Walt had learned Eyring rate theory from his mentor Henry Eyring and how to make intracellular recordings with glass electrodes from the inventor of the technique, Gilbert Ling. (Walt pulled pipettes over a Bunsen burner by hand.) He had worked on radar during the War. He did an extraordinary amount of teaching and ran the biophysics training grant. Walt had assembled his own LINC lab computer (at the MIT Lincoln Laboratory, together with Albert M. Gordon) and liked making equations, designing electronic devices, and above all helping others to move forward. He was a kind and generous mentor, still an inspiration to me. Finally, Theodore Kehl was director of an online computer facility, one of the few in the country. His group supplied me with laboratory computing power for 16 years until the personal computer revolution made it possible for everyone and every setup to have their own. They wrote enabling micro code and developed higher level languages anticipating spread sheets for data analysis; they designed interfaces and eventually minicomputers. I learned a lot about making digital circuits and programming through years of close interaction. The online computer across the hall from me was used for dog and cat experiments throughout the week, but it was made completely available to me for a long day of experiments every Saturday.

My doctoral studies and degree were called Life Sciences, and my classes had been dominated by a wide range of “pure” sciences. Science was abstract and undertaken for intellectual reasons, like playing chess. Through its adaptation to the environment, every organism offered unique puzzles worthy of investigation, and yet biology could recognize universal principles that held it all together. If research offered any benefits to society, they would emerge in due course but could not necessarily be predicted.

The University of Washington gave me my first experience in the culture of American medical schools. I encountered a more “applied” motivation. In this ideal, science was a quest to cure diseases of people. All other organisms were simply “models,” practical “systems” that could model a human problem. When I wrote the next chapter on active transport for the Textbook of Physiology, I described the Cambridge school’s classical experiments on squid giant axons. Professor Ruch asked me to use mammalian experiments instead. Science was divided. On our side of the street, the medical school side, funding came from the NIH, and across the street, the natural sciences side, from the National Science Foundation (NSF). Increasingly over the years we were asked to write in our proposals about the health and disease motivation of our work and to strive for “translational” impact from bench to bedside. For American society it is clear that Congress funds the NIH with enthusiasm because of the promise of longer and healthier lives. As biomedical scientists we are the beneficiaries of that vision, which has been much more generous for us than for life scientists funded by the NSF. Indeed, today I can think better about the potential health relevance of our research and can pass these ideas along to others. Still, rarely in my scientific life did I make major choices about my research direction because of their apparent health relevance.

In contrast to my experiences at The Rockefeller University, the department did not yet embrace the importance of molecular biology, biochemistry, and cell biology for functional understanding, a deficit in thinking and staffing first addressed by our third Chair, Wayne E. Crill, in the 1980s, and now fully changed after Stanley C. Froehner became the fourth Chair in 2001. Over the years, like many departments, ours became increasingly interdisciplinary, and our graduate program developed an emphasis on getting students quickly into the lab and not requiring so many disciplinary courses. Also, the number of training grant slots has dropped dramatically, so our departmental graduate program became smaller while interdisciplinary programs of Molecular and Cellular Biology and Neuroscience and Behavior grew.

Over the years our department has been fortunate to keep a strong ion channel and biophysical faculty. Fairly soon Chuck Stevens and Walt Woodbury left, but they were replaced by Wolfhard Almers and Peter B. Detwiler; Jonathan (Joe) Howard came; eventually Wolf and Joe left, but William N. Zagotta, Fred Rieke, Sharona E. Gordon, L. Fernando Santana, and Charles L. Asbury came, keeping us young and vigorous. Quite early, Edwin G. Krebs of Pharmacology brought in William A. Catterall, who replaced him eventually as Chair and brought in Bruce L. Tempel and Todd Scheuer. It has been wonderful to have these excellent colleagues and good friends. Between them and the strong intellectual descendents of Ed Krebs and Edmond H. Fischer (1992 Nobel laureates for the discovery of protein phosphorylation), there have always been people to provide intellectual and technical guidance as we ventured into new areas of signaling (Bill Catterall, Neil N. Nathanson, H. Stanley McKnight, Joseph A. Beavo, Daniel R. Storm). I was never tempted to go to another institution and never allowed any offers to be developed for more than a polite 10 minutes.

Ion Channel Biophysics: Starting with Permeation

In my empty laboratory room, everything was missing! Could I make a voltage clamp from operational amplifiers? Fortunately, operational amplifiers had not yet become integrated circuits so I could expose the inner printedcircuit board to remove the capacitative feedback elements that rolled off the frequency response and thus restore the bandwidth needed for a node clamp. This required no understanding of de novo transistor circuit design. Ted Kehl explained to me about the “new” digital large scale integrated (LSI) circuit chips with NOR gates, NAND gates, flip flops, and even decade counters. With these I designed my first digital circuit, a digital timer for the stimulator. Also light-emitting diodes (LEDs) were new in the toolbox, so I added a few to show when each pulse was active. Frankenhaeuser had shown me a stimulator he designed, and I could copy his analog output. A plate glass company had half-silvered glass I could use to make a mirror for photographing the oscilloscope with a Grass camera. And so it went in small steps, much aided by the skills and experience of our departmental electronics shop and machine shop.

I was lucky that Denis Noble as editor of the series Progress in Biophysics and Molecular Biology had asked me to write a review, undoubtedly at Hodgkin’s suggestion. This gave me a fun task to interleave with the slow assembly of equipment. My essay “Ionic Channels in Nerve Membranes” (1970) addressed two questions: “(1) Do several permeant ions share a common pathway through the membrane or are the pathways for different ions different? (2) Is the ionic permeability a diffuse property of broad areas of membrane or is it located in discrete specializations?” I argued for discrete Na⁺, K⁺, and leak channels and attempted to calculate plausible limits on single-channel conductance. Not everyone agreed fully with the thesis: to his helpful stylistic comments on a draft of the chapter, Kenneth S. Cole added a note, “I am worried that you may be pushing some of your channel arguments pretty far.” This was my first review and my first book chapter. I learned that I like to write reviews and that multiauthored book chapters appear in print only a distressingly long time after the original deadline.

For the first 15 years in Seattle, my work was unabashedly membrane biophysics. Every new lab seems to get started too slowly. My first research project was to determine the conductance of a single Na⁺ channel by looking for a reported quantization of the subthreshold voltage responses of the node of Ranvier. It was a total disaster and made me despair of ever succeeding in research. For a year I could see apparent quantization in histograms that in the end I found was what you could get with a random number table!

Then I moved to the mechanisms of ionic selectivity. Could one learn about the pore by probing it with different ions? Several papers had described the permeability to NH₄⁺ both in Na⁺ and K⁺ channels, and Chandler and Meves (1965) had measured the alkali ion selectivity of the Na⁺ channel in squid axons. Papers by Tasaki and others had shown that nerve fibers could conduct action potentials in Na⁺-free solutions containing organic cations such as guanidinium. (He presented such work as refuting Hodgkin’s “Na⁺ theory” of action potentials.) I felt that before one could speculate about permeation mechanisms, one should identify every ion that went through and several similar ions that did not. Maybe then, as in studies of the active site of enzymes and drugs, one could postulate some steric and chemical properties of the pore. Within a few years, I found 11 cations were clearly permeant in Na⁺ channels, and 4 in K⁺ channels of the node of Ranvier. Strikingly, every cation with a methyl group was impermeant. Thus, in Na⁺ channels “big” hydroxyguanidinium, (NH₂)₂C⁺NHOH, was permeant, whereas “little” methylammonium (CH₂NH +) was not! Using molecular models and reading about alkali metal crystal radii and the length of hydrogen bonds, I proposed in a series of papers that the Na⁺ channel offers an oblong 3.1 x 5.1 Å slit to permeating cations lined by hydrogen-bond-accepting oxygen atoms acting as surrogate water molecules (e.g., Hille, 1971). I called this the “selectivity filter.” Graduate student Donald T. Campbell and I developed a new voltage clamp method for frog skeletal muscle that used the same vaseline gap setup as the nodal clamp (Hille and Campbell, 1976). For dissection, it required only snatching a short segment of one muscle fiber from the muscle with watchmakers forceps. The ionic selectivity of the muscle Na⁺ channel was identical to that of the node (Campbell, 1976), although we now know that the Na⁺ channel is coded by a different gene. Similarly, Bezanilla and Armstrong (1972) and I (1973) proposed that the K⁺ channel is a round 3.0–3.3 Å hole lined with oxygens. The K⁺ channel prediction was elegantly confirmed by the first K⁺ channel crystal structure from Roderick MacKinnon (Doyle et al., 1998), but for the Na⁺ channel there are still no structures after almost 40 years. Now we know of many Na⁺ and K⁺ channel genes. All these channels show remarkable near identity in selectivity sequence, reflecting a strong conservation of the selectivity filter.

In selectivity studies, one can define the relative permeability of two cations, either from the reversal potential in a biionic experiment or from comparison of the magnitude of the currents the ions can carry. Hodgkin and Huxley’s (1952) independence principle states that these two measures would be equivalent, but in my measurements they were not. Apparently ions did not move independently. I wrote, “[Some] organic cations may leave the pore more slowly than sodium ions do. Slow leaving could explain the reduction of currents below the size expected from the independence principle . . . for the cation might ‘tie up’ the channel so long that other ions are prevented from entering” (Hille, 1971). We began to recognize a subtle gradation from permeant ion to blocking ion. Extending this idea, I found that even Na⁺ ions could saturate the pore at high enough (nonphysiological) concentrations (Hille, 1975).

Ann M. Woodhull, my first graduate student, revisited my earlier observation that extracellular protons could block the Na⁺ channel pore and discovered that the block was relieved by depolarizing the membrane potential further. This was well fitted by an Eyring rate theory model in which extracellular protons were hopping into a binding site, the acid group, within the pore with rate constants that depended on the membrane potential (Woodhull, 1973). While protonated, the pore was not Na⁺ permeable. The model became very widely used, cited 1330 times. The idea was that, since the acid group was part way through the pore, the protons would experience a small fraction of the membrane potential drop in getting to it. Ann’s results put the acid group 25% across the membrane field from the outside. It was natural therefore to go on to describe saturation, block, and the deviations from independence for permeant ions by similar hopping models. An Eyring rate theory model with three Na⁺ “sites” and four barriers in a row in the permeation pathway, gave a reasonable fit to the deviations from independence (saturation) for Na⁺ channels when only one ion was allowed in the pore at a time (Hille, 1975). Although a general rate-theory description of diffusion had been presented years before by Eyring and his colleagues (including Woodbury), the new features of our models were judiciously placed barriers and wells, combined with saturability of permeation sites. Other early biophysical work in my lab was done by graduate students Rosalia Ridaura, Shing-Yan (Bill) Chiu, Michael D. Cahalan, Kenneth R. Courtney, and Bruce C. Spalding and by postdoc Ted B. Begenisich.

At this time our family took a sabbatical year in Germany. I joined Robert Stämpfli’s lab at the University of Saarland. Our two boys went to a German elementary school and Merrill used the library to prepare grant proposals for her new faculty position in Zoology at the University of Washington. In a fun collaboration with Robert Stämpfli, Wolfgang Nonner, Berthold Neumcke, and Franco Conti from Italy, we measured the singlechannel conductance of the Na⁺ channels of the node of Ranvier by stationary fluctuation analysis (Conti et al., 1996). We got 7–9 pS. The method required measuring the noisy small stationary currents remaining after a few hundred milliseconds of depolarization, calculating their power spectral density, subtracting a background noise spectrum, and fitting the remainder to the sum of Lorentzian power spectra predicted from a HodgkinHuxley-like description of the macroscopic currents. It was an interesting exercise. Fortunately the others were in full mastery of the analytical and theoretical sides of the study, and Robert Stämpfli dissected all the nodes. Five years later Franco and Wolfgang and I could get together in Seattle where we measured nonstationary fluctuations from K⁺ channels and, by extensive autocorrelation analysis, Wolfgang was able to extract kinetic details of several K channels in the node (Conti et al., 1984).

Hodgkin and Keynes (1955) had done isotopic K⁺ flux experiments in Sepia axons, which they interpreted in terms of a K⁺ channel pore that contained several K⁺ ions in a row, moving in single file. Wolfgang Schwarz and I modeled this more complicated “long-pore” effect with a multi-ion hopping model, again using a saturable rate theory (Hille and Schwarz, 1978). It reproduced the results of Hodgkin and Keynes (no surprise) and went on to show that such a multi-ion pore could be blocked with exceptionally steep voltage dependence by an internal ion that cannot cross the outermost barrier. This gave further credence to the earlier brilliant hypothesis of Clay Armstrong (1969) that inward rectifier K⁺ channels are pores that are blocked by an impermeant TEA-like particle coming from the cytoplasm when trying to pass outward K⁺ current. Only in the late 1980s were cytoplasmic Mg²⁺ and organic polyamine compounds shown to be the endogenous voltage-dependent blockers underlying inward rectification. As a sign that the channel hypothesis was still not universally accepted in 1978, our theoretical paper had difficulty in the review process. Before it was finished, there were five reviews, three of which were negative for numerous reasons: Theoretical work “did not belong in the Journal of General Physiology”; it “does not unify a number of disparate findings into a single theoretical framework . . . rather it attempts to support a molecular notion of a potassium channel”; the arguments were “salesmanship” and “uncritical”; evidence that the delayed rectifier is a multi-ion pore “is thin, almost to the vanishing point”; the inward rectifier is probably a carrier and “the argument that inward rectifier channels are pores because delayed rectifier channels are likely to be pores has no force and should be deleted.” Fortunately, the editor, Paul F. Cranefield, accepted the paper with relatively small modifications. This paper has been cited 660 times. A few years later, graduate students Andrew (Andy) L. Blatz studied proton block of inward rectifiers and Paul J. Pfaffinger studied regulation.

We moved to permeation in ligand-gated ion channels. Postdocs David J. Adams and Terry M. Dwyer heroically measured reversal potentials for 75 (!) cations at the nicotinic acetylcholine receptor channel at the frog neuromuscular junction. They found that 40 cations have a permeability relative to Na⁺ that is larger than 0.1 (Dwyer et al., 1980; Adams et al., 1980). The pore was large, 6.5 x 6.5 Å. With such a large pore, the small alkali metal cations would rarely touch the walls in passage and the channel accepts them all with little discrimination. Postdocs Jorge Sanchez, John A. Dani, and Detlef Siemen continued with competition among slow permeant ions in the nicotinic acetylcholine receptor. With a smaller subset of ions, graduate student Jian Yang found that the selectivity of the 5-HT₃ (serotoningated) receptor channel closely matches that for nicotinic receptors (Yang, 1990). Today we know that nAChRs and 5-HT₃ receptors have very close sequence similarity, and that more generally, the postsynaptic excitatory and inhibitory neurotransmitter-gated channels all seem to have relatively wide, poorly selective pores. We still lack high-resolution crystal structures of open postsynaptic channels, so the pore sizes estimated from permeation have not been tested directly. In our last channel-characterizing studies, Paul S. Taylor determined the ionic selectivity of snail A-current channels, Karl Woll studied a high-conductance Cl– channel, Steven Barnes described Ca²⁺-activated Cl– channels and hyperpolarization-activated Ih channels in salamander rod photoreceptors (Barnes and Hille, 1989), and Lonnie P. Wollmuth characterized the ionic selectivity and block of those Ih channels (Wollmuth and Hille, 1992; Wollmuth, 1994)—now called HCN channels.

Ion Channel Biophysics: Pharmacology

In my Ph.D. thesis, I considered drugs worth studying because they would inform about the channels I wanted to understand. There were already spectacular results from Clay Armstrong. We continued this approach in Seattle. Some examples are given here.

Early on, when it was discovered that myelinated axons could be loaded with TEA in the cytoplasm by cutting the ends of the fibers in the desired internal solution (Koppenhöfer and Vogel, 1969), Clay Armstrong called to suggest that we should use his TEA analogs to show that the TEA receptor I had studied (Hille, 1967) was inside the axon rather than outside as I had thought. We had a couple of very enjoyable weeks together in Seattle, and I continued a few more experiments afterward. The upshot was that at the inner mouth of the nodal K⁺ channel there was indeed a TEA receptor guarded by the activation gate that duplicated all the properties seen in the squid (Armstrong and Hille, 1972). Thus, for this channel too the activation gate is on the cytoplasmic end. However, on the outside there was another TEA receptor not seen in squid that did not depend on gating. This is the one I had studied before. We now know that K⁺ channels differ widely in their TEA affinity at the outer TEA site, depending on whether there is a ring of four tyrosines (highest affinity) or other residues in the mouth.

Many people in the lab studied local anesthetic action on Na⁺ channels (Gary R. Strichartz, Ken Courtney, Wolfgang Schwarz, Phillip T. Palade, and me). Again we were greatly helped by Bertil Takman who suggested key lidocaine analogues. Gary, my first postdoc, discovered that membraneimpermeant quaternary derivatives such as QX-314 applied inside the axon via the cut end blocked Na⁺ channels best with large depolarizations (Strichartz, 1973). The phenomena suggested that Na⁺ channels have an activation gate at the cytoplasmic mouth that reveals a large inner vestibule with a local anesthetic binding site, just as Clay had deduced before for TEA in K⁺ channels. Evidently, Na⁺ and K⁺ channels shared significant structural similarities. With ionizable amine local anesthetics, we found the phenomenon of use-dependent block, a growing accumulation of blocked channels during repetitive depolarizations. It arises when the local anesthetic is driven into its receptor within the pore by depolarization and is slow to escape afterward. Using pH changes and analogs of different hydrophobicity, I concluded that local anesthetics approach their binding site in the channel vestibule along two paths, the hydrophilic path found by Gary for charged species when the gates are open and a hydrophobic path sneaking perhaps from the lipid right through the substance of the channel into the vestibule even when the gates are closed (Hille, 1977a). By exploring various voltage protocols, I also found another dependence on gating. The local anesthetics had higher affinity for inactivated channels than for noninactivated ones and thus made inactivation more likely (Hille, 1977b). These ideas were dubbed the modulated receptor hypothesis and have been cited ∼1400 times. Interesting medical implications became apparent to me only after the experiments were over: the use-dependent block meant that local anesthetics would block high-frequency firing (as during a noxious stimulus) much better than low-frequency firing; and the modulated receptor meant that related molecules used as cardiac antiarrhythmics would beneficially prolong the refractory period of cardiac muscle, eliminating premature firing of action potentials. The latter idea was made clear in a closely similar model of antiarrhythmics given in a review by Hondeghem and Katzung (1977). These medical implications were said to be instrumental in my election 25 years later to the Institute of Medicine.

Michael Cahalan (1975) studied action of a Centruroides scorpion venom on Na⁺ channels. Depolarization promoted a reversible modification of activation gating that shifted the voltage dependence of activation in the hyperpolarizing direction by an enormous 40–50 mV without changing inactivation gating. Thus, activation and inactivation gating can be severely decoupled. Again the drug–receptor interaction depended on the gating state of the channel—foot in the door. In the end, as with many other scorpion venoms, the axon fires excessively, which can produce pain, exhaustion, and arrhythmias. Now we understand that scorpion toxins bind directly to the extracellular side of one of the Na⁺ channel voltage sensors.

Ann Woodhull, Bert I. Shapiro, and I (Hille et al., 1975) revisited shifts of the voltage dependence of activation in Na⁺ channels due to divalent ions (Hille, 1968a). We measured shifts under a wide range of extracellular divalent ions, pH, and ionic strength and argued that all changes could be understood as the electrostatic effects of solution cations interacting with the local negative surface potential of the membrane (an idea that traces back to A. F. Huxley) and binding to surface acidic groups. We successfully modeled all the shifts with a full Gouy-Chapman-Stern surface-potential theory from colloid chemistry, including surface charges, ion atmospheres, and binding. Our work was inspired by a clever compact paper with the same variables studying activation of K⁺ channels in the node from our Leningrad colleagues Galina Mozhayeva and Alexander Naumov (Mozhayeva and Naumov, 1970). Clay Armstrong never accepted biasing voltage sensors by surface potentials. Instead he favored models with discrete binding complexes on the ion channel protein and no electrostatic component. I imagine that both mechanisms apply. They have conceptual overlap. Today one would model these effects as occurring on individual voltage sensors.

As a last exercise in gating pharmacology, we returned to the Na⁺ channel openers, veratridine, pyrethroids, DDT, and batrachotoxin. Graduate student Jeffry B. Sutro, postdocs Steve Barnes and Mark D. Leibowitz, and visiting faculty Jürgen R. Schwarz contributed to a story that these “toxins” all modify Na⁺ channels in a reversible use-dependent manner. A foot-inthe-open-door step severely shifts the voltage dependence of activation gating and shuts down inactivation such that the channels remain open (but with lowered conductance) vastly longer than normal after a brief opening depolarization (summarized in Hille et al., 1987). Thus, insects die of DDT and pyrethroid poisoning because of a continuous massive discharge of their nervous system. They may lie on their backs thrashing their limbs to exhaustion.

On Writing

My channel biophysics period culminated in writing a book on ion channels. Writing numerous review articles and several book chapters had confirmed the painful delays experienced when waiting for other authors. I had taught medical students the basics of nerve and synapse. I had taught graduate students, both in basic biophysics and in an advanced course that changed topics every year and had included whole quarters on, for example, gating currents, lipid bilayers, pore theory, or calcium signaling. I had a grant, was a professor, and was serving 4 years on an NIH Study Section. Inspired also by my father, who had written 13 mathematics texts in his lifetime, I decided I was ready to write. My training in biology had made me uneasy with the direction that channel biophysics was taking. Did it matter for biology whether a Na⁺ channel has 8 gating states or 31? Why was channel biophysics out of the mainstream and usually written in an electrical and mathematical language inaccessible to biologists? When biochemically minded people had tried to approach ion channels, they often were not aware of the wonderful things that were already known and the precise vocabulary that we had developed. Couldn’t one make this field I loved more understandable and summarize the extensive body of knowledge in simpler language, so more people would be excited and interested to bring the techniques and concepts of their discipline to bear on the ion channels? Would this allow a new era of advances in ion channel genetics, evolution, development, cell biology, protein chemistry, structure, neurobiology, and disease?

Writing the original Ionic Channels of Excitable Membranes book (1984) took 3 hard years. Each chapter would introduce only a few fundamental concepts, getting progressively deeper. I wanted to base the story on the original observations and the original data records. The information would not be comprehensive but rather clear and correct, yet it would form a baseline from which professional training could continue. Electrical words, including conductance, and equations would be minimized. There would be no integrals or Laplace and Fourier transforms, and even algebra would be minimal. There would be no technical information on how to do electrical experiments, series resistance, or electrodes. The examples would be those I thought could survive indefinitely. I had realized that some fields were looked down upon because the investigators could not agree, so I eschewed controversy. I wanted readers from all countries, so I stuck to a basic AngloSaxon English. My goal was to write a paragraph a day. A chapter would have to be divided if it took more than an hour to read out loud. I wanted readers to feel the satisfaction of reading a whole chapter in a day without giving up—and to find it interesting. Many colleagues made good suggestions on drafts, and even my mother ruthlessly removed superfluous words.

The next two editions of my book (1992 and 2001) again took 3 full years to write. Each time the literature had grown more than three-fold. There were 7000 papers on ion channels by 1984, 30,000 by 1992, and 100,000 by 2001. The first time, personal computers were in their infancy and the first word processors were appearing only at the end, so my dedicated, precise, enthusiastic, and invaluable secretary, Lea M. Miller, typed the whole thing by hand numerous times. The next two times, Lea could use a word processor. Only for the last edition did we have the great advantage of easy e-mail and Pubmed and could the publisher Andy Sinauer set type automatically from the digital files. I am very grateful to Andy for full trust on the direction and content of what I wrote, although in retrospect I wish someone had noticed that the last edition became inordinately long. It no longer allowed a quick, cover-to-cover read. The last edition had a revised title, Ion Channels of Excitable Membranes, at Christopher Miller’s urging. He even organized a vote at a Gordon Research Conference about “ion” versus “ionic.” The vote was overwhelmingly in favor of ion! Still needed today would be a short book for introductory teaching that is much more basic than my first edition.

Writing the book led to a new status. I became recognized by many as the author of their text rather than as a practicing scientist. It also led to more invitations and changes in my alliances. I was elected to the National Academy of Sciences. After I was asked to give a Presidential Lecture (1984) and a Grass lecture (1989) to the Society for Neurosciences, I finally moved from thinking of myself solely as a membrane biophysicist to adding the label neuroscientist. Only then did I become a member of the SfN and begin to go to their meetings as well as those of the Biophysical Society.

As an aside on writing, I mention authorship. In an older tradition that was common in physiology and in British laboratories, Ph.D. students worked by themselves and published by themselves. It was true of my own thesis, and I have tried to make this possible for most of my own students as well. They acknowledged my help and my grants, and that was enough. However, as research has become increasingly interdisciplinary, we have often had to add names from other laboratories for tools and data provided. In those cases, I have added my own name as well. For 15 years, my own papers were also largely sole-authored as they represented work done by me on Saturdays in an otherwise empty laboratory. However, eventually I stopped direct research, and very fine postdocs became an extension of my personal research. Then my name would be at the end. I have continued programming, data analysis, and model building but not actual work with the cells. When someone in my lab has contributed to a paper from a lab of an untenured faculty member, I try to keep my name off the paper, as it confuses the subsequent review for tenure to see the name of a more senior principal investigator and to not to be sure whether the junior or the established author should take credit for the writing, insights, and discoveries.

People often lump scientists and engineers into a language-deprived category. High verbal scores qualify people for the humanities and the arts. Wrong. Writing grants, articles, e-mails, reports, and evaluations of grants, manuscripts, and people as well as reading or editing what other people write account for the majority of my day. I would say that writing is power. It is a skill that can be sharpened by study and practice and becomes a lot of fun. Read books of style. Read good writing and think about what makes it good rather than just the content. One needs to parse sentences, paragraphs, and essay structures in the same way that we critique science. If you don’t want to do it alone, there are courses and editors for people at any level of accomplishment. The sooner you start, the better you get and the more you enjoy it. Some people have writer’s block and would rather do an experiment than write it up. They should remember that all of our support comes from taxpayers, foundations, and companies who don’t care about doing experiments for fun; they want only the published, accessible, peer-reviewed results, often for the benefit of society. The contract is not met without the final vetted writing. In our lab, writing the paper becomes a significant learning experience in research.

G Protein–Coupled Regulation of Ion Channels

While the book was being written, the biophysics scene changed dramatically. Three major breakthroughs had occurred in 1981 and 1982: the patch clamp invented by the Neher-Sakmann lab (Hamill et al., 1981), the IBM personal computer, and the first ion channel cloning (Noda et al., 1982). The patch clamp meant that reliable voltage-clamp records could be obtained in any cell type. No longer did one need special giant cells. Even the central nervous system and somatic tissues became accessible. I built four patch clamps early on, but soon they could be bought off the shelf from several manufacturers. Within 15 years, over 10,000 patch clamps had been sold, all capable of recording the conformational changes of single ion channel proteins in the submillisecond time frame. All users could forget about how electronic circuits are designed. The IBM PC meant that every investigator and setup could have a capable computer—every day of the week. Our lab, particularly postdocs Mark D. Leibowitz and Donald W. McBride, wrote good online data acquisition systems for the PC combining C and BASIC languages, which we used for 15 years at each clamp setup. However, again before the decade was over, everyone was buying excellent commercial acquisition and analysis software bundled with their patch clamp. Quantitative electrophysiology became accessible to the masses both in academia and industry. With the later advent of the Microsoft Windows operating system, the style of real-time programming we had been using in Microsoft DOS became obsolete. Some channel biophysicists stopped programming for themselves. Cloning of channel subunits meant that the chemical information we had inferred so indirectly began coming out in quantity, and, later, that many people turned from adult differentiated nerve and muscle to expression systems using transfection in cell lines to study their favorite ion channel in isolation. Eventually patch clamp could be done in high-throughput, 96-well plates.

I was eager to start in new directions of research that might be more biological. We stumbled into a new area quite by accident. In the older vein, I had suggested to graduate student Paul Pfaffinger that he consider a thesis on the properties and pharmacology of inward rectifier K⁺ channels. It was characteristic that I selected problems in part because nobody else was doing them at the time. I haven’t liked to work in competitive areas. Since this was 1984, still before the cloning of K⁺ channels, it was necessary to find a suitable excitable cell, so I sent Paul to visit Neil N. Nathanson in Pharmacology, who was doing pharmacological work on chick atria. We learned that Neil’s lab was using isotopes of K⁺ to test whether muscarinic agonists increased K⁺ permeability via a receptor coupled to a G protein. I knew little about G protein–coupled receptors (GPCRs), which at the time were just emerging as a concept, but we were sure that patch clamp would be a clearer way to study the K⁺ permeability change. At that time, the physiologists who had studied the acetylcholine-activated inward rectifier of heart were suggesting that the muscarinic receptor was mechanistically like the nicotinic receptor, a channel, but taking 100–200 ms instead of <1 ms to open in response to acetylcholine. Indeed, according to nice experiments by Soejima and Noma (1984), no intracellular diffusible second messenger was involved.

Neil tutored us in the basics, and soon in a wonderful collaboration, Paul showed that GTP was needed and a pertussis-toxin-sensitive G protein (Gi) coupled the muscarinic receptor to the channel (Pfaffinger et al., 1985; also Breitweiser and Szabo, 1985), challenging the prevailing view of cardiac electrophysiologists. A couple of years later Diomedes Logothetis, in David Clapham’s lab, showed that the G protein βγ subunits were the membranedelimited direct signal between receptor and channel in this signaling without a cytoplasmic second messenger (Logothetis et al., 1987). This was one of the first clear examples of signaling by Gβγ subunits, so novel that it met with resistance. The ion channel was soon dubbed GIRK (G protein–coupled inward rectifier K⁺ channel, now the Kir3 channel family).

Paul Pfaffinger’s discoveries were made so fast that he still needed a thesis project. Perhaps he could generalize our conclusion to another K⁺ channel controlled by a muscarinic receptor. He turned to the suppression of the noninactivating M-current in sympathetic neurons by muscarinic and other agonists (Brown and Adams, 1980). As he found, however, this was hardly parallel to the cardiac example. The channel was turned off rather than on by muscarinic agonists. The inhibition and recovery were much slower. He showed that a G protein and GTP were clearly involved, but it was not pertussis toxin sensitive. Around that time, muscarinic receptors were cloned and it became evident that they are all GPCRs. The M₁, M₃, and M₅ receptors couple through the G protein later called Gq, whereas the M₂ and M₄ receptors couple through pertussis toxin-sensitive Gi/Go. The GIRK channel was activated by cardiac M₂ receptors, and the M-current on the other hand was suppressed by neuronal M₁ receptors. It took us another 15 years to elucidate the mechanism of M-current suppression.

We had become hooked on a new direction of research involving GPCRs and ion channel modulation. We left the frog node of Ranvier for good and soon switched to rodent neurons with an eye to the greater medical “relevance” of mammals. Whole-cell patch clamp became our technique of preference. Out of a lingering affection for frogs, I still give each departing lab member a frog statuette from places like Mexico, China, or Africa, where they are properly revered.

It was a little unnerving to go from a field that is as precise and well studied as channel biophysics to a new much more biochemical field that was just emerging and had no precise answers, but it has been very satisfying and productive. By good fortune, a generous mid-career grant from the McKnight Foundation allowed us to retool our lab toward the new patch clamp methods and to get plausible experience for federal support. We could write that disorders of monoamine GPCR agonists are considered major contributors to Parkinson disease, schizophrenia, and depression, that many drugs of psychiatry and drugs of abuse act on GPCR signaling, and that GPCRs control our mental state—although we still worked with only a single cell at a time. Our group became larger. Because of the interdisciplinary nature of the new work, our papers tended to have more authors. People who worked in the lab on these problems included Paul Pfaffinger, Mark D. Leibowitz, Martha M. Bosma, Ken Mackie, Laurent Bernheim, Alistair Mathie, David J. Beech, Mark S. Shapiro, Felix Viana, Jiuying Zhou, Lonnie P. Wollmuth, Duk-Suh Koh, David E. Garcia, Jeffry B. Isaacson, John P. Roche, Humberto Cruzblanca, Byung-Chang Suh, Lisa F. Horowitz, Wiebke Hirdes, Keith W. Dilly, Jane E. Lauckner, Jill B. Jensen, Björn H. Falkenburger, Eamonn J. Dickson, and Martin Kruse.

While we were leaving channel biophysics for receptor signaling, Merrill was also moving from the classical sea urchin to the newer zebrafish. We admire scientists who can pursue a single problem to exquisite depth in a long career, yet sometimes it is good to change. The old problem really may be finished, or it may seem no longer as scientifically interesting as some new problems—or perhaps the problem would advance better with fresh perspectives of other minds. It is also personally refreshing and exciting to think about new challenges.

Cell Biology of G Protein Signaling

When we switched to mammalian neurons, we began to follow up on published observations that voltage-gated Ca²⁺ channel currents could be reduced by a variety of GPCR agonists (Dunlap and Fischbach, 1978; Marchetti et al., 1986). We and others found a dozen receptors that could decrease the N-type Ca²⁺ channel currents of all large superior cervical ganglion cells (Hille, 1994). Their action took <1 s to develop and was almost as fast to reverse. Many were pertussis-toxin sensitive and insensitive to intracellular Ca²⁺ chelators. One lesson from this was that each individual neuron is likely to have a large repertoire of different GPCRs coupled to some common effectors, as Roger Nicoll had argued (Nicoll et al., 1990). In the end, the rapid inhibition was another direct Gβγ action, this time on Ca²⁺ channels, with no cytoplasmic intermediates (Herlitze et al., 1996; also Ikeda, 1996).

In a parallel line of study, Ken Mackie came to our lab during his fellowship training for Anesthesiology. We soon heard about the identification of a new GPCR common in the brain for cannabinoids, later called the CB₁ receptor. It inhibited adenylyl cyclase, so we guessed it should be able to inhibit Ca²⁺ channels and activate GIRK channels like other Gi/Go-coupled receptors. Furthermore, like the stunning success story of one decade before with opiate receptors, maybe endogenous agonists would be discovered and a new field would blossom. As anadamide was announced, Ken confirmed the predictions for Ca²⁺ and GIRK channels, giving the first electrophysiological mechanism for endogenous cannabinoid actions (Mackie and Hille, 1992; Mackie et al., 1993; together cited >800 times). The field took off, and Ken with it. Ken remained as faculty in Anesthesiology for many years, so we could share and publish many fun studies together. His lab adopted molecular biological approaches quickly and gave us a lot of help in working with the constructs we wanted to express.

Continuing with the sympathetic ganglion neurons, we and others also recognized four receptors that decreased currents in three ion channels: Nand L-type Ca²⁺ channels and M-type K⁺ channels (Hille, 1994). These actions took 10 s and were slow to recover. They were blocked by Ca²⁺ chelators inside the cell but were not pertussis toxin sensitive. This slow pathway, as we called it, had to wait another decade to be understood.

A key technical breakthrough came when the genes underlying M-current were finally identified as KCNQ2 and KCNQ3. Mark Shapiro in our lab quickly set them up in a mammalian cell expression system with coexpressed M₁ muscarinic receptors (Shapiro et al., 2000). At last we could study M-current modulation in cells that were readily transfected, and we could dispense with using animals. We returned to elucidating the signaling of the slow pathway from M₁ receptors to KCNQ K⁺ channels. For a couple of decades, several labs had asked in vain, what is the inhibitor of the KCNQ channels in this pathway. Fortunately, postdoc Byung-Chang Suh realized that this might be the wrong question. He proposed instead that the channels might turn off because of the destruction of a channel activator. Stimulation of M₁ receptors is communicated to Gq, which in turn activates the enzyme phospholipase C (PLC). PLC then cleaves the rare plasma membrane phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP₂). Suh’s hypothesis was that the channels need PIP₂ as a cofactor to function and the depletion of this lipid during receptor activation turns them off temporarily until PIP₂ is resynthesized. This notion seems to be correct: channels turn off when PIP₂ is depleted, and they require PIP₂ resynthesis to recover (Suh and Hille, 2002; Suh et al., 2006). These discoveries were made possible because we could use an expression system, but the reviewers asked that they be verified in “real” neurons.

In my early career it was hard work to keep an audience focused on ion channels as proteins and to explain that the lipid bilayer is just a passive supporting dielectric insulator that allows channel proteins to do their jobs. Now I began to read and lecture about the importance of phosphoinositide phospholipids! In reviewing the literature, we realized that many plasma membrane proteins are sensitive to the level of PIP₂ (Suh and Hille, 2005). Donald W. Hilgemann had pioneered with a report that one cardiac ion channel and one ion transporter required PIP₂ to function (Hilgemann and Ball, 1996). We showed that regulation by receptors in neurons could be explained this way. As biophysicists, we developed quantitative kinetic descriptions with informative models that included the known biochemical steps of G protein signaling and phosphoinositide metabolism (Suh et al., 2004; Jensen et al., 2009; Falkenburger et al., 2010a, b). We became lipocentric. We added confocal microscopy and a wide range of fluorescent probes, including pairs of probes for measuring molecular proximity by fluorescence resonance energy transfer (FRET). This has been an unexpected and satisfying shift of direction. The cell biology of phosphoinositide signals is a fascinating subject in its own right.

Biophysical Excursions into Other Fields

Biophysical methods, especially those resulting from the patch-clamp revolution, can contribute to many outstanding problems in cell biology. Our lab has had a significant number of publications in several overlapping nonneuronal fields: (1) anterior pituitary endocrinology, (2) sperm activation, (3) calcium signaling, and (4) regulation of exocytosis. Some would say this shows lack of focus, but the problems are all approachable by similar methods and the questions are ones that in my dilettante undergraduate and graduate biology training were of great interest to me.

Our endocrine signaling studies included postdocs, Martha M. Bosma, Amy M. Tse, Frederick W. Tse, Akiko Iwata, James B. Herrington, Alexander P. Naumov, Solveig Hehl, and Andre Golard, and graduate student Julia Billiard. Most of this work was related to reproductive biology and done during a long and very satisfying association with other investigators in an NICHD-funded population center concerned with male contraception. This goal was one that I could readily identify with, given the enormous overpopulation of our planet. In good collaborations with Wolf Almers downstairs, we learned ratiometric measurements of calcium dyes and measurements of exocytosis by membrane capacitance increases, bringing me back to my postdoctoral days of photometry with photomultipliers. One experimental approach to contraception is to stop release of the gonadotropins LH and FSH from the anterior pituitary. We decided to analyze the GPCR signaling underlying gonadotropin release. Amy Tse set up identification of pituitary gonadotropes from dissociated rodent pituitaries. We traced the intracellular events during stimulation by gonadotropin-releasing hormone (GnRH). In brief, the GnRH receptor acts through Gq to stimulate phospholipase C (PLC), generating inositol trisphosphate (IP₃) and diacylglycerol. The IP₃ releases Ca²⁺ from intracellular stores in an oscillatory manner, with plasma membrane Ca²⁺ channels making almost no contribution to the Ca²⁺ signal (Tse and Hille, 1992). The Ca²⁺ stores are only partly emptied and then refill in each cycle (Tse et al., 1994). At the high point of each cycle of a Ca²⁺ oscillation, a hundred secretory granules containing the hormones LH and FSH are secreted by exocytosis (Tse et al., 1993). Thus, the secretion from an individual cell occurs in repeated little bursts, 15–20 s apart. The secretion is further potentiated by protein kinase C activated by the diacylglycerol (Zhu et al., 2002). During each Ca²⁺ elevation, the cell hyperpolarizes (via KCa channels) and it secretes. With the exception that the exocytosis is Ca²⁺ regulated, this pathway is in almost all respects quite unlike that which regulates secretion in neurons. This made me more interested in the cell biological differences between neurons and other secretory cells. To my surprise when we tested how growth hormone releasing hormone (GHRH) releases growth hormone from somatotropes, another class of anterior pituitary endocrine cells, there was little in common with the gonadotrope story. It was a little more like that in a neuron. The mechanism involved synthesis of cAMP, phosphorylation of some target channel, depolarization of the cell, Ca²⁺ entry via voltage-gated Ca²⁺ channels on the plasma membrane, and Ca²⁺ regulated exocytosis (Naumov et al., 1994). In the same cells, the famous pertussis-toxin-sensitive inhibitory actions of somatostatin could be explained by hyperpolarization due to opening of GIRK channels and simultaneous inhibition of adenylyl cyclase due to Gi.GTP.

Gradually we realized that regulation at the pituitary would at best take months to stop and to restart male fertility, so we then turned more directly to the physiology of spermatozoa. The team spearheaded by Donner F. Babcock included Gunther Wennemuth, Andrew J. Harper, Anne E. Carlson, Sonya M. Schuh, and Lindsey A. Burnett with significant collaborations with other labs providing knockout mice. Many experiments were based on a new technique that Donner established to get time-lapse movies of the flagellar beat and to analyze the flagellar waveform quantitatively. They studied factors in the female tract that can activate the flagellar beating of sperm, which include bicarbonate, adenosine, and catecholamines. They found that a soluble (not membrane) sperm adenylyl cyclase (SACY) and protein kinase A were essential both in this activation of beating and in enhancing Ca²⁺ entry in response to alkaline depolarizing solutions. Although sperm seemed to have immunoreactivity for numerous kinds of standard voltage-gated Ca²⁺ channels, the Ca²⁺ entry evoked by depolarization required instead a unique sperm Ca²⁺ channel, CatSper, discovered in David E. Clapham’s lab. The slow transition of sperm to hyperactivated swimming some time after ejaculation also required the CatSper channel. Perhaps such findings can contribute to future approaches to family planning and fertility.

Finally, our calcium signaling and exocytosis work has been done by Dok-Suh Koh (and his several Korean students), Donner Babcock, Jim Herrington, YoungBae Park, Edward J. Kaftan, Ronald F. Abercrombie, Gunther Wennemuth, Tao Xu, Liangyi Chen, and Joseph G. Duman, with good collaboration from Toan T. Nguyen in pancreatic duct epithelium. One line of work concerned Ca²⁺ clearance from the cytoplasm after a modest load. Using chromaffin cells, we found to our surprise that 80%–85% of the Ca²⁺ load disappeared in seconds into the mitochondria, from which over a minute or two it was transported back into the cytoplasm while the plasma membrane transporters gradually exported it from the cell (Babcock et al., 1997). We wondered whether mitochondria are always the most powerful Ca²⁺ clearance mechanism. In comparing a number of different cell types, we found that the fastest clearance could be via mitochondria (chromaffin cell), via the intracellular SERCA pump (pancreatic β-cell), both (gonadotrope), or via the plasma membrane transporters (sperm). Apparently, each cell is specialized for a different agenda. Another line we pursued was stimulation of exocytosis in the absence of Ca²⁺ signals (Hille et al., 1999). In some secretory epithelia, the physiological regulation of exocytosis is primarily through receptors that stimulate protein kinase A and protein kinase C without the Ca²⁺ rise that is so prominent in neuronal synapse. The resulting phosphorylation also potentiates Ca²⁺-induced secretion (Zhu et al., 2002; Jung et al., 2010).

A Life of Academic Science

We are lucky to be academic scientists since we get to think all day about questions that fascinate us, we direct ourselves, we interact continuously with smart and like-minded people, and we are invited to travel to many fascinating parts of the globe. This addictive job comes with responsibilities. For research, we need to run a responsible and reliable research group that publishes its discoveries after suitable critical review and is accountable for where the money went. For teaching, we need to offer classes that inspire students and communicate the concepts, process, and content of our science. For administration, we need to help academia and the institutions of science and government to provide a system, finances, and facilities for research and education, for the improvement, prosecution, dissemination, and use of science in our society.

The high standards of today’s science are maintained by peer review. Peer review is key to the success we have and to our feeling of relative autonomy—academic freedom. It should be vigorously defended and responsibly executed. After we have benefited from funding of our research proposals and publication of our papers for a while, we owe our peers our best judgment by serving on review panels and editorial boards. Sometimes the requests come in too early. I suggest junior scientists accept only a single session of study section to learn more about what makes proposals successful and to gain some confidence in the peer review system. Then, I would stay away until the lab is well established and you have tenure before committing to a several-year term. It is hard work. I first served a full term on an NIH study section in 1980-1984. The success rate was high then, but I favored a more elitist approach with more money going to the most productive and trendy scientists and less to those whose science was being done well but just seemed less exciting. However, subsequently I realized that the scientists I would have cut off were specialists, even sleepers, in some field that suddenly became necessary and important for a new development. For example, when molecular biology discovered new genes to test, certain seemingly esoteric biophysical assays became the best way to study their roles, and valuable science was rapidly advanced. Natural populations are strongest if they offer a wide range of genetic variation to adapt to changing conditions. I conclude similarly that the scientific enterprise is strongest if a broad range of specialties is maintained that can be called on as science advances. Equally, a review committee is strongest when it has a variety of viewpoints. Later I served for many years on the Scientific Advisory Boards of the Biomedical Scholars program of the PEW Charitable Trusts and of the Investigators Program of the Howard Hughes Medical Institute. These programs were oriented more toward supporting the best investigators rather than some specific project. These boards were very satisfying to serve on because of the high quality of the science, the investigators, the members of the Board, and often the venue.

Another debt that we owe is in mentoring. By the time we reach seniority, many people have helped us greatly along the way. Early on, we are supervisors of those who work in our laboratories, and our orientation is typically, how can I get the most progress out of them for my advancement? Later we need to pay back more fully, with a new attitude: My job definitely is to advance the career of each person in the lab but also, where possible, to assist faculty colleagues. The university often does not provide much of a contract, if any, to its employees, but I would say that it acquires an unwritten obligation to each new junior faculty member. The faculty member should provide research, teaching, and other service, and the university should make every effort to facilitate growth and nurture careers and satisfaction of its junior faculty. Junior faculty are expected to do many things they were not trained to do, things that we senior faculty have seen endless times. It is easy for us to provide guidance and suggestions on these familiar topics to relieve the stress. Soon the junior faculty grow into stronger senior faculty.

The public thinks of universities, especially state universities like mine, as institutions that exist to teach students. We may be promoted on the basis of published research, but we are hired and paid to teach. This is a major role of professors. Fortunately, the subjects we teach are usually directly interesting to us and the rewards of imparting understanding, sophistication, and success to junior minds are great. Teaching is taking students from wherever they are to a higher level. I am best at lectures. The effective lecture has to be a form of entertainment: interesting, relevant, understandable, and snappy. It must be progressive, developing concepts in a logical order. I count on needing 12 hours to make a completely new lecture, so it can’t be done on the fly while already giving the course. Fortunately today, PowerPoint keeps a good record of what you did that is easily edited so next year is much easier. For research seminars, I see the same criteria of theatre, progressivity, and so forth, but the subject can go further because of the sophistication of the audience. Nevertheless, I like to assume as little specialized knowledge as possible. Define terms, explain abbreviations, use them minimally, and bring people up to speed with some didactic development. Stick with points that are needed to get to the punch line. Too many opaque professional talks are given that could have been understood and would have been interesting to everyone had the speaker only taken care to bring them on board. It seems that many people develop their style in lab meetings where maybe everyone already knows what you are talking about. I treat research lectures very much like teaching lectures. Finally, both in lectures and in publications, the slides and figures are important. They need clarity, visibility, simplicity, and grace—even beauty if possible. In our lab we rehearse lectures and fine-tune graphics.

Science is a world activity. In every country people are thinking deeply and refining our body of knowledge. We are invited to many places where we are warmly accepted by colleagues we have not met before. For example, for me significant early visits were associated with the 1972 IUPAB International Biophysics Congress in Moscow. I went to the three great Soviet laboratories of ion channel biophysics: Boris I. Khodorov in Moscow, Galina N. Mozhayeva with Alexander P. Naumov in Leningrand (now St. Petersburg), and Platon G. Kostyuk with Oleg A. Krishtal in Kiev, Ukraine. Through the later dissolution of the Soviet Union (1991), the mass emigration of many Soviet scientists, and the disastrous drop of their economy and support for science, these three labs continued to train extraordinary scientists. Their heads have remained apparently as active as ever, still leading their groups today with the highest standards and vigor well after they passed their 80th year. Their perseverance in adversity and continued accomplishment as octogenarians are lessons in the strength of the human mind and of a life in science. I have gotten to know and respect these scientists and many others. They exemplify the spirit of scientists around the world.

Like the arts, science needs patrons to support it, and fortunately our society has supported science generously for 60 years. Where would the arts and humanities be now had they been as highly regarded by governments! Unlike the arts, science is a collective and incremental activity. We can easily name dozens of individual artists, authors, and philosophers of each of the last five centuries and say that we have seen, heard, or read their original works. However, nobody but a historian reads science done 100 years ago, and as ideas are refined each decade, we do not remember the past contributors. Peer review that I praised before is a critical process that constantly looks for deficits in every new work. If we do not remember the contributors and we are used to finding faults, where is the recognition for the scientists? We must all remember to praise now. Especially as we become more senior, it is our turn to remember to give encouragement, to highlight good research, to credit our sources, and to nominate people for awards and honors. Every paper will be improved upon by someone else tomorrow, but that is not a reason to criticize the previous authors. It just means that the scientific method is healthy and science continues to progress as it must.

A significant part of academic life is family and what happens outside the workplace—the Greek idea of a balanced mind and body. As cell scientists, Merrill and I do enjoy discussing lectures and ideas we have heard, and we do a lot of reading and writing at home. But very important are hiking, backpacking, snowshoeing, skiing, going to concerts and art exhibits, bird watching, gardening, and other activities that we often did with our sons as they were growing up, but now also with our grandsons. Erik became an actuary, and Trygve, a chemical engineer. They each have a wonderful spouse and each a son. The generations continue.

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Ivan Izquierdo

BORN:

Buenos Aires, Argentina

September 16, 1937

EDUCATION:

University of Buenos Aires, M.D. (1961)

University of Buenos Aires, Ph.D. (1962)

APPOINTMENTS:

Assistant Research Anatomist, UCLA (1964)

Assistant Professor of Pharmacology, University of Buenos Aires (1965)

Professor of Pharmacology, University of Córdoba (1966)

Professor of Pharmacology, Federal University of Rio Grande do Sul, Brazil (1973)

Professor of Physiology, Escola Paulista de Medicina, Sao Paulo (1975)

Professor of Biochemistry, Federal University of Rio Grande do Sul, Brazil (1978)

Professor of Neurology and Chairman of the Memory Center, Pontifical Catholic University of Rio Grande do Sul, Brazil (2004–present)

HONORS AND AWARDS (SELECTED):

Odol Prize for Junior Scientists, National Research Council of Argentina (1965)

Honorary Professor, Universities of Buenos Aires (1991) and Córdoba (2006)

Antonì Esteve Prize, Antonì Esteve Foundation, Barcelona (1992)

Rheinboldt-Hauptmann Prize, University of Sao Paulo (1993)

Basic Medicine Award, Academy of Sciences of the Developing World (1995)

City of Porto Alegre Medal for outstanding services to the community (1996)

Decorations: Great Cross, Order of Scientific Merit, (1996) and Order of Rio Branco (2007), both from the Government of Brazil, and Medal of Merit, State Legislature of Rio Grande do Sul (2009)

John Simon Guggenheim Award (1997)

Açorianos Literary Prize, the City of Porto Alegre (1999)

Memorial Lectures: J.A. Izquierdo (1999), O. Orias (1999), A. Thomson (1999), M.R. Covian (2000), J. Flood (2000), R. Caputto (2000), C.P. Duncan (2001), S.C. Ferguson (2009) and H-J. Matthies (2010)

Lifetime Awards: State Research Foundation, Porto Alegre (2001), International Neuropsychiatric Association (2005), Brazilian Neuroscience Society (2007)

Honorary Citizen of Porto Alegre (2003)

International Neuroscience Symposium for my 70th birthday, Curitiba (2007)

Doctor Honoris Causa, Federal University of Parana, Curitiba (2007), and University of Cordoba (2011).

Foreign Associate, National Academy of Sciences, U.S.A. (2007)

Member, Academy of Sciences of the Developing World (2007)

Creation of the Ivan Izquierdo Research Prize, Clinic Hospital of Porto Alegre (2007)

Conrado Wessel Prize in General Science, Conrado Wessel Foundation (2008)

Premio Ciudad Capital: Ciudad de México (2009)

Premio Almirante Alvaro Alberto (National Science Prize), Brazil (2010)

Ivan Izquierdo and his coworkers demonstrated the main molecular steps of memory consolidation for one-trial avoidance and other tasks in the hippocampus and other brain areas, the separation of short- and long-term memory, and the main mechanisms of extinction and memory persistence. Izquierdo trained over 90 graduate students, and established memory research and set up several centers of excellence in neuroscience in both Brazil and Argentina.

Ivan Izquierdo

I was born in Buenos Aires in 1937. My mother, Margarita Gobic, had come from Croatia in 1913 at the age of 3. My father, Juan Antonio Izquierdo, came from a family who had arrived in 1806 from Barcelona.

My parents, my sister Mitzy, and my Croatian grandfather, Agustin, were major influences in my life. Another major influence was the city of Buenos Aires, where in 1937 one-third of the population had been born in Europe and nearly all the rest were descendants of European immigrants. A touch of Indian ancestry was taken for granted among those of us with Spanish roots. So it was a mongrel city, truly cosmopolitan, in which it was impolite to label anybody as a foreigner; Spaniards, Italians, Uruguayans, Bolivians, and Paraguayans were viewed as locals. The most famous tango singer Carlos Gardel had been born in Toulouse; some of the country’s best soccer players had played for Italy in the 1934 and 1938 World Cups (and won); American, European, and Mexican pop songs were popular alongside the tangos. My mother sang many of these songs beautifully.

My grammar school taught in Spanish in the morning and in English in the afternoon. It was one of the many bilingual schools in town. In 1950 I entered the Colegio Nacional de Buenos Aires, a high school attached to the University of Buenos Aires and whose teachers included prominent intellectual figures. At that time the country was drifting toward a dictatorship, but the school remained a beacon of democracy. It instilled in me an interest in world culture, science, literature, and above all, political decency.

I keep contact with my sister and with friends from my teenage days. We were born in the last years of general tolerance in a country that was soon to plunge into dictatorships and decades of political turmoil. A Paradise lost.

Borges

In the late 1930s and early 1940s, Argentina was home to many major European artists and intellectuals who came because of political or ethnic persecution at home. Among them, Manuel de Falla, Roger Caillois, Witold Gombrowicz, Jiménez de Asúa, some of my best high school teachers, several friends, and Cajal’s disciple Pío del Rio Hortega, who planted the seeds of neuroscience in Buenos Aires with another exile, Christofredo Jakob.

The writer, Jorge Luis Borges, was a towering influence over the ebullient local cultural life of those days. He saw life as “a game with shifting mirrors” and had the strong suspicion that what we call reality may be as deceiving as Berkeley and Hume had thought it was. I was introduced to Borges’s literature by my father and by my high school Spanish teacher Antonio Pagés Larraya. My interest in memory research and, of course, in literature, owes a lot to Borges. He raised or answered some of the most serious questions on memory, like: “When we remember something, do we remember the thing itself or just the last time we remembered it?” He demonstrated that perfect memories are impossible in a short story published in 1944, Funes the Memorious: Funes could recall an entire day of his life, but for this he needed another entire day of his life to the last second, which is of course absurd. In other stories Borges postulated games with time and memory, the incorporation of the memory of others, and a world in which memory is believed not to exist.

Borges’s notion of a constantly mutant reality (the mirrors that shift) helped me deal with the vertiginously changing world that was beginning about the time I was born. I attended many lectures by Borges at a place called the Free Institute of Superior Studies during my high school years, and I talked with him many times about Robert Louis Stevenson or Joseph Conrad or about Nazism as a monster implanted in the womb of a culture that had given us Goethe, Beethoven, and Heine. Borges’s views antedated those of Ingmar Bergman (The Serpent’s Egg, 1977) by a quarter of a century. I am still haunted by the possibility that similar monsters can be born anywhere, any time. Life painfully taught me that they do.

Medical School and the Apple of Research

I entered the University of Buenos Aires Medical School in 1955. Three months later a military coup toppled the government of General Perón. The new generals in charge promised a rapid return to full democracy, which ended up being neither rapid nor full. In the university the consequences of the coup were immediate and largely beneficial. The university, like most in Argentina in those days, was federal. Several professors who had been ousted by the fallen regime came back, including the most important scientists of Argentina: the 1947 Nobel Prize winner Bernardo Houssay (who discovered the regulation of glucose metabolism by pituitary and other hormones), Luis Leloir (who was to receive a Nobel Prize in 1970 for his landmark work on the role of sugar nucleotides in carbohydrate synthesis), Eduardo Braun Menendez (the discoverer of the renin-angiotensin system and its role in hypertension), and Eduardo De Robertis (who discovered neurotubules and then synaptic vesicles and their contents and had been in exile in nearby Uruguay). These four men would have a large influence in my life. Leloir, perhaps the only genius I have ever known, was a very modest man and taught me the importance of not thinking too much of oneself (no creérsela, as they say in Argentina). That is one of the most important things I ever learned.

In Medical School teaching improved overnight: The new professors actually lectured about things that they were doing, or that had been discovered by people they knew. Braun Menéndez rushed into the classroom one morning and told the students that his friend Vincent du Vigneaud had just won a Nobel Prize for determining the structure of oxytocin.

Many students were attracted by the possibility of working with the famous masters or their disciples. Research had become the apple to bite. So I went to see Professor Houssay in December 1956, right after my Physiology exam, with a research idea of my own. He received me at 6:30 in the morning, we talked briefly, and he told me to come back on January 2. My research career started that day. Houssay was a short, soft-spoken man who gave the right impression of wielding a great authority. He had created a school of Physiology that produced excellent research-oriented professors all over Latin America. My research project proved wrong, but I had bitten the apple for the first time and enjoyed the taste. Houssay believed that young students inclined to science should try different fields before deciding on a definitive one, and he introduced me to Roberto Mancini, an excellent endocrinologist in the Institute of Anatomy chaired by De Robertis in the Medical School. I joined Mancini’s lab for the next 2 years (Mancini et al., 1957) and learned a lot from him. He was a kind man with a sharp mind, a great endocrinologist, and a superb scientific writer.

On to Neuroscience

De Robertis and his associates Hersch Gerschenfeld and David D. Sabatini visited the lab often to see their friend Mancini and talked with enthusiasm about their own work. Sabatini taught me a lot about the power of education. His idol and role model was Domingo Faustino Sarmiento, a President who in one term of office (1868–1874) reduced Argentina’s illiteracy rate from 90% to near 0%. This was the foundation of a fantastic development that lasted one century and attracted millions of immigrants.

In 1958, encouraged by Houssay, Mancini, and De Robertis, I decided to move on to neuroscience. The research carried out in the De Robertis lab required many consecutive hours of work, which was beyond my possibilities as a medical student. So he advised me to work with my father, who was his friend. My father had begun a scientific career late in life and did acute experiments on the autonomic system that began and ended on the same day.

In many ways it was fun working with my father, even though we disagreed about almost everything that a father and a 21-year-old son usually disagree about. But we had many good moments, and working together was good for the two of us. We discovered that stimulation of the central end of the sectioned vagus nerve briefly increases sympathetic tonus (Izquierdo et al., 1959), which 40 years later was shown to influence memory consolidation by Robert Jensen and his group. We also described a stimulant effect of pyrogallol on duodenal motility due to rebound cholinergic activation (Izquierdo and Izquierdo, 1961), which would be the subject of my Ph.D. thesis. In those years the University had a joint M.D./Ph.D. program in order to absorb the large number of students interested in research.

There was to be a Brazilian parenthesis: In late 1958 I met Miguel Covian, an Argentine neurophysiologist from the School of Medicine of Ribeirao Preto, University of Sao Paulo. He gave a very impressive seminar in the Medical School on brain control of the endocrine system. My friends Franco von der Walde, Claudio Suárez, and I asked him if we could spend part of that summer vacation in his lab. He agreed and kindly offered us to sleep in the lab if we wanted. So the three of us spent 2 months that year in Covian’s Department of Physiology, living cheap, working hard, and enjoying it a lot. Everybody there was extraordinarily nice to us, including professors Cesar Timo-Iaria, Ricardo Marseillan, Jose Antunes, and Eduardo Krieger, who taught us a lot. I returned the following year for 2 more months. My two trips to Ribeirao Preto reaffirmed my intention to work in neuroscience; and made me fall in love with Brazil, its people, its music, and its joie de vivre.

In Buenos Aires, I saw De Robertis frequently. Through reading and talking with him, I was becoming strongly interested in learning and memory. This was not his field, but he felt a Platonic love for it. In 1959, José “Pepe” Segundo, a top specialist in learning and memory and a friend of De Robertis from his days of exile in Uruguay, visited him in Buenos Aires. Pepe invited me to visit his electrophysiology lab in Montevideo, 1 hour away by plane, where he and his group studied regional brain electroencephalography (EEG) in cats during a variety of conditioned reflexes. I visited Segundo’s lab many times and spent the winter vacation of 1960 working with his disciple, César Galeano. Shortly before that, Pepe Segundo had joined the University of California at Los Angeles’s (UCLA) Brain Research Institute (BRI).

In 1961 I set up a cheap and simple conditioned reflex lab in the Pharmacology Department of the School of Pharmacy in the University of Buenos Aires, and I worked in it under the advice of Cesar Galeano (Izquierdo and Östman, 1961). In the mornings I attended the excellent Electroencephalography Service of the Military Hospital, where I learned a lot about clinical neuroscience with Abraham Mosovich, a man of great kindness and wisdom, who was the only civilian head of a service in that hospital.

My thesis was approved in early 1962. I applied for, and was awarded, a postdoctoral fellowship from the University of Buenos Aires to work with Pepe Segundo at UCLA. The fellowship began in May 1962.

Go West, Young Man

Before traveling to the United States I made two little trips to nearby Porto Alegre, Brazil, that would change my life. In the first, in January 1962, I met Ivone de Moraes, who was then 19 and as lovely as she is now. In the second trip, in April, on the way to Los Angeles, I asked her to marry me. As will be seen, 1 year later we did marry and I went back to Los Angeles with her. We have just celebrated our 47th wedding anniversary.

Pepe Segundo’s lab at UCLA was a happy and active place. Pepe had three research groups in the same lab: one was with Nicolas Buendia, Larry Stensaas, and Curt Bell, who worked on unit recordings from the reticular formation; another was with George Moore and Don Perkel, who did intracellular recordings in Aplysia and studied the role of firing patterns in the transmission of messages in the abdominal ganglion.

The third group was with Germán Sierra from Spain, Wanda Wyrwicka from Poland, and me. Wanda was a disciple of Jerzy Konorski, the discoverer of Type II or instrumental conditioning. Wanda, Germán, and I implanted cats with chronic electrodes through which we recorded neocortical and hippocampal EEG and delivered arousing stimuli to the periaqueductal gray. These were used as unconditioned stimuli (USs) and were paired with tones as conditioned stimuli (CSs) during different phases of sleep. We established conditioned arousal during slow-wave and rapid eye movement sleep, first as a classical and then as an instrumental conditioned response, lasting weeks (Izquierdo et al., 1965). But we could not tell whether regions in the brain distant from our recording sites had been “awake” at the time of the CS-US pairings. This problem is intrinsic to all research on learning during sleep and has proven to be insurmountable till this day. It is simply impossible to monitor every cell group and determine whether it is “asleep” or not during sleep, or to know what being asleep means for a small group of brain neurons.

In October 1962 there was the famous Cuban Missiles Crisis that took the world to the brink of a nuclear war. The crisis drew me close to John D. Green, who had been to me just a brilliant neuroscientist till then, and became a good friend from then on. He and I were both foreigners, were very scared, and had no family nearby. So we talked and talked about our fears and hopes, usually over long dinners while the ominous alarm siren sounded in the distance. The Cuban crisis fizzled out before the end of 1962, so I went back to Porto Alegre, married Ivone, and after a few days in Buenos Aires and New York, we settled in Westwood Village where UCLA is. Once back, I finished my work with Pepe Segundo and moved to John Green’s lab. John had invited me to work with him upon my return to UCLA.

There was no other period of my life in which I learned more about research than in the 15 months I worked with John Green. His meticulous way of obtaining and analyzing data left a profound impression on me and changed my own way of working forever. We wanted to study homo- and heterosynaptic facilitation and postsynaptic potentiation in a search for putative bases of learning such as had been proposed by Albert Fessard shortly before; long-term potentiation (LTP) was yet to be discovered. We did intracellular recordings from hippocampal pyramidal cells in vivo. Green had tried hard to get them with Curt von Euler and others and failed, whereas recently both Eric Kandel and Sir John Eccles had succeeded very neatly, using rods of plastic or glass making slight pressure on the alveus in order to keep it from moving with respiration. Green refused to use pressing feet because they changed the polarity and shape of evoked potentials in the CA1 region, so could alter their relationship to unit activity. I was able to confirm those field potential shifts a few years later with Beatriz Vásquez in Córdoba (Izquierdo and Vásquez, 1968). In 1964 the practical result was that Green and I did penetrate a number of cells from cat CA1 without using pressing feet, but they survived too little to be of any use. (Hippocampal slices were also not yet known).

So we moved on to motor neurons in the spinal cord. Two other postdocs joined our team: Maria Candelas Bravo, from Spain, and Emilio Décima, from Argentina. Sir John Eccles himself visited the lab on his way to the 1963 Nobel Prize and gave us plenty of advice as to how to set up the spinal cord preparation. We worked hard for several months till we finally felt we were on the verge of getting good results. But we tried to do too many things with each cell every time we got one; most cells did not survive our successive attempts to record homo- and heterosynaptic facilitation and posttetanic potentiation in sequence.

In February 1964 my son Juan was born in UCLA. John Green enjoyed visiting him at our home. We had long chats with Ivone about life, Mozart, and the Beatles, who had just visited Los Angeles. John, in his Oxonian way, found their music “rather lively.”

In March 1964 my fellowship from the University of Buenos Aires was about to end, and the UCLA Department of Anatomy, through the good offices of Pepe Segundo, John Green, John French, and Carmine Clemente hired me as Assistant Research Anatomist. This opened the possibility of staying in UCLA indefinitely since, as they told me, the following step could be a formal appointment as an Assistant Professor. So easy it was to get a job at a major university in the United States in those heady days, when the Americans thought they had a scientific gap to close with the Russians.

Ivone and I pondered what to do next. The School of Pharmacy of the University of Buenos Aires was offering me an Assistant Professor position. However, Argentina was in a state of disarray, having suffered another recent military coup that failed, in the middle of an economic crisis. We felt that the right thing to do (noblesse oblige) was to return to that University anyway, in return for the fellowship it had given to me during more than 2 years. So we left UCLA and went back to Argentina in May 1964.

The experiments with John Green on homo- and heterosynaptic interactions were never finished. He died of a heart attack shortly after his marriage a few months later, and Décima, Bravo, and I dispersed. In 1967 I returned to the subject in Córdoba, Argentina, using evoked potentials in the rat hippocampus (Izquierdo and Vásquez, 1968).

The University of Córdoba

Back in Buenos Aires I received my first graduate student, Alicia Merlo. She and I set up a brand-new state-of-the-art, but elementary, electrophysiology lab where we did a nice, detailed study of the projections of the medial forebrain bundle (Izquierdo and Merlo, 1966). We also worked on the effect of peripherally injected catecholamines and cathecol-O-methyl transferase inhibitors on avoidance learning (Merlo and Izquierdo, 1967), which was pioneering at the time.

In 1965 the National Research Council of Argentina gave me my first award: The Odol prize for junior scientists. Bernardo Houssay presided over the ceremony, and the prize was given to me by Eduardo De Robertis.

In January 1966 my second son, Carlos Eduardo, was born in Buenos Aires.

Meanwhile, a new, highly promising scientific center was being established in the second oldest university in the Americas, the National University of Córdoba, founded in 1613 in the center of Argentina. The dean of its School of Chemistry, Ranwel Caputto, a famous neurochemist just arrived from Oklahoma and a disciple of Luis Leloir, invited me to join his School as a Full Professor of Pharmacology. I accepted right away.

In June 1966, Ivone, Juan (2 years), Eduardo (5 months), and I left for Córdoba in a little Renault Dauphine full of luggage. The day we traveled, once more a military coup overthrew a president in Argentina. But now this deposed president was a gentle, old, decent, highly democratic man, and the general who took over soon proved to be just another authoritarian figure. We had no radio in the car, so we learned about the coup only when we stopped at a hotel that night, near Córdoba.

In Córdoba my first job was to discover where could I get someone to sign my appointment as a Professor. The Rector of the University was the personal doctor of the deposed president and was away in Buenos Aires taking care of his illustrious patient. Numbers 2, 3, and 4 in the line of succession were somewhere else too. After a few days of anxiety, number 5 eventually came up and signed my appointment. My second job in Córdoba was to find lab space. For reasons I will never know, my appointment as a Professor of Pharmacology did not imply that there should be any physical space associated with it. The Department of Pharmacology was an imaginary entity straight out from the world of Borges, perhaps an entelechy. Through the generosity of Caputto and the neuroendocrinologist Samuel Taleisnik I was allowed to use an excellent electrophysiology lab in the latter’s private research institute. It had been set up for somebody who had just left the country.

There, with Beatriz Vásquez, Antonia Gladys Nasello and Erna Marichich, we carried out significant work on the regulation of hippocampal electrical activity by extracellular potassium (K⁺). We put to test John Green’s posthumous hypothesis, sketched out in a 1964 article in Physiological Reviews, that hippocampal electrical activity could be self-regulated at different functional levels by [K⁺]o accumulating in the very restricted extracellular space of CA1, particularly in the stratum radiale, where apical dendritic shafts run parallel and close to each other for long distances. We studied this using two approaches, both in vivo: (1) to instill onto the surgically exposed hippocampus drugs known to enhance (veratrine) or inhibit (tetraethylammonium) spike-dependent K⁺ release (Izquierdo and Izquierdo, 1967); (2) to perfuse the alveus under no hydrostatic pressure (I still felt allegiance to John Green’s abhorrence of pressing feet) with isotonic solutions of different K⁺ concentrations that would equilibrate with [K⁺]o . Green had predicted that at a certain [K⁺]o level there would be a predominance of synaptic enhancement that would underlie both facilitation and posttetanic potentiation, due to a depolarization-induced promotion of Ca²⁺ entry into synaptic terminals; and that above those levels, first the preepileptic phenomenon called “spike complications” (actually envelopes of apical dendritic spikes) and then full-fledged seizures would occur. We succeeded in validating Green’s K⁺ hypothesis (Izquierdo, 1967; Izquierdo and Vásquez, 1968; Vásquez et al., 1969; Nasello et al., 1969; Izquierdo and Nasello, 1970; Izquierdo et al., 1971). The precise levels of [K⁺]o that enhanced synaptic transmission and those that trigger seizures were determined later by Jan Bures and his group in Prague with K⁺ sensitive electrodes, which we had no possibility of getting in Córdoba.

Meanwhile, we had hired Otto A. Orsingher as an Associate Professor in the Department. He came from several years at the Istituto Superiore di Sanità, in Rome, where he had worked with the Nobel Prize winner, Daniele Bovet, and had become a friend of James L. (Jim) McGaugh. I knew Prof. Bovet from my Buenos Aires days; he regularly visited family there and every time he came he also visited me. He was the archetype of a kindly wise man.

Otto and Jim were to become two of my best friends. Otto introduced me to Jim’s recent method to study the effect of drugs on memory consolidation by injecting them right after training, rather than before. Jim understood consolidation as a relatively short-lasting, postacquisitional process through which recently learned information is consolidated into memories (McGaugh, 1966).

In 1969, I met Jim McGaugh in a symposium in Buenos Aires. We got along together very well from the beginning, and our now long-standing friendship started, fittingly, with a touch of humor. I was translating questions raised by the audience to his presentation, and translating back his responses to the public. At some point, in response to one question, Jim said: “Nothing could be finer.” I quipped “Than to be in Carolina”; and right away we sang the third line of that song together and became friends for life. We have a similar attitude toward life, in which humor plays a major role.

Beginning in 1969, Otto, I, and others carried out a number of experiments using posttraining drug injections to study consolidation. We described posttraining memory-enhancing effects of amphetamine, nicotine, and atropine (Evangelista and Izquierdo, 1971, 1972). Otto and I carried out a study of rats inbred for their low performance in a shuttle avoidance task, which we then thought was linked to hippocampal dysfunction but is now known, instead, to result from a high level of anxiety in the animals. We established the memory-depressant (Fulginiti and Orsingher, 1970) and anticonvulsant (Izquierdo and Nasello, 1973) properties of Cannabis compounds.

But life was beginning to become difficult in Córdoba. In 1968 a popular uprising sparked by police brutality lasted several days and the toll was 14 dead, all civilians. The first night of the uprising, soldiers camped in front of our building thought that there were snipers in the terrace, so they shot at our walls during interminable hours. Ivone, our two kids, and I slept in a corridor just because it was two walls away from the street instead of one, and so stray bullets were less likely to hit us. After that, tensions subsided for some time, but urban guerrilla groups began to proliferate all over the country, including Córdoba. Our Department, being in the ground floor, was easy to invade. One week 5 different activist groups occupied the Department, each to be expelled in the evening by the police through the use of force. Our students were scared, all of us were taken hostages for hours, and some of the invaders threatened to kill all the rats and destroy all the equipment, which they said was used to produce results for imperialism. Otto and I had to negotiate each day the release of the hostages, as well as our own safety and that of the animals, first with each invading group and then again with the police. Then, almost every night, bombs resounded all over the city. Córdoba has ceased to be the “bucolic” place Ivone and I had looked for a few years before. However, we loved it so much that we stayed there as long as we could.

In July 1973 right after I had finished talking over the phone with a friend, it rang again and a harsh voice told me that if I insisted to talk with darn Bolsheviks like the person I had been talking with (actually, a moderate center-left biophysicist), they would kill me and my whole family. Ivone and I almost immediately decided to leave Argentina. There were several political murders every day in the country, and both terrorist and paramilitary groups were rampant; so the phone threat could not be taken lightly. The old Paradise had indeed been lost. The option as to where to go was obvious: Ivone’s parents lived in relatively nearby Porto Alegre, and although Brazil was also under military rule, at least there were no shootings, bombs, or death threats there. Furthermore, Ivone’s father was terminally ill, and we thought it decent to accompany him during the last few months of his life. Our children adored him and he was a great friend of mine. Our idea was to stay in Porto Alegre for a few months and then eventually migrate to the United States.

Porto Alegre and Then São Paulo

So we packed, sold everything we could not pack, and traveled to Porto Alegre. Again, we did not dare to look back because tears would have been too many. My last Ph.D. student in Córdoba had been Mario Tannhauser, from Porto Alegre, who arranged for me a contract in the Federal University of Rio Grande do Sul, starting in August. I was hired as a Professor of Pharmacology. We did not know then that Porto Alegre was to be our home town. Clearly, there were signs of a political opening in Brazil, which according to its rulers, was to be “slow and gradual.” But it was an opening after all; quite the opposite of the rapid and violent shutdown that was taking place in Argentina.

It was easy to adapt to southern Brazil: Its lifestyle is very much like that of Argentina. Ivone was born in Porto Alegre and I knew the city well. Brazilians are more optimistic than Argentines, and they are more adept to laissez passer, which makes life easier. Now that years have gone by, I find the differences have smoothed out. Perhaps that is the result of the enormous exchange of people between the two countries in the past 30 or 40 years. Actually, cultural and behavioral differences over most of the world have smoothed out.

Initially, the prospects for doing research in Porto Alegre were dim. Except for a few scattered laboratories, the university had almost no tradition of research and a generalized dislike for it. I carved a space at the Physiology Department and did carry out some research work in it, so I could finish some neurochemical work I had initiated in Córdoba (Gattoni and Izquierdo, 1974). I again set up an elementary learning lab, where I studied the effect of several drugs (Izquierdo, 1974a, b) and the effect of maturation (Izquierdo et al., 1975) on pseudoconditioning of rats in a shuttle box.

Ivone’s father died in early 1974. Soon after that, I was invited to take a position at the prestigious Escola Paulista de Medicina, an isolated federal medical school in São Paulo with a long and solid tradition in research. So in January 1975 we moved there. The Dean of the Biosciences School in Porto Alegre, Tuiskon Dick, promised that he would create the conditions for me to return, at the most in 2 or 3 years. He did not accept my resignation and gave me an indefinitely long leave of absence instead, in the hope I would return.

So in January 1975 I took my new position at the Department of Physiology in the Escola Paulista in São Paulo. This was a research-oriented place as I had gotten accustomed to since my days at UCLA, Buenos Aires, and Córdoba. Immediately a few excellent graduate students joined me in my brand-new, but primitively equipped lab: Esper Cavalheiro, Lia Prado de Carvalho, Lineu Calderazzo, and Romeu Schutz. We decided to give continuity to the work on pseudoconditioning and to study its eventual role as a component of shuttle box avoidance conditioning. We reasoned that as there was an identifiable Pavlovian stimulus-pairing component and a separate avoidance contingency component in that form of learning (Rescorla and Solomon, 1967; Izquierdo, 1976), there could well be a pure “drive” or pseudoconditioning factor too, superimposed on the associative components, as suggested by my good friend Wanda Wyrwicka, with whom I exchanged abundant correspondence on this. I had in fact just described neurochemical correlates of pseudoconditioning, so it had a biological substrate of its own.

We trained rats in a shuttle box using acoustic stimuli as CSs and footshocks as USs, and we studied several control training modes: one in which tones and footshocks were interspersed randomly (pseudoconditioning), another in which they were paired on every trial regardless of responses (Pavlovian mode), and another one in which the CS-US interval was varied at random but USs were given only when there had been no shuttling to the last CS (avoidance contingency). We studied the effect of many drugs and several brain lesions on the four behavioral paradigms. Some treatments selectively affected the pseudoconditioning or “drive” component, others affected the Pavlovian component, and others the avoidance component (Izquierdo and Cavalheiro, 1976; Cavalheiro and Izquierdo, 1977; Schutz and Izquierdo, 1979). So we added one more factor, “pure drive” or pseudoconditioning, to the Pavlovian and the avoidance components of shuttle behavior studied by Rescorla.

Meanwhile, the discovery of LTP by Tim Bliss in 1973 opened up new possibilities for the biological study of consolidation, and LTP was immediately regarded as a memory model. We had continued to work on the effect of posttraining treatments on memory consolidation. In São Paulo we found that agents that released catecholamines peripherally could strongly affect consolidation (Gozzani and Izquierdo, 1976; Rachid et al., 1977). We were among the first to report brain noradrenaline and dopamine changes in brain regions after aversive training (Schutz et al., 1979).

In addition, our laboratory studied some effects of acute and chronic ethanol on behavior, the EEG, and hippocampal RNA (Prado de Carvalho and Izquierdo, 1977, 1978; Prado de Carvalho et al., 1978). I was to go back to this field several years later, while visiting Jim McGaugh’s laboratory, where we found that the amnesic effect of repeated alcohol intoxication could be overcome by muscarinic agonists given systemically (Brioni et al., 1989).

In 1977, Tuiskon Dick, still Dean of the School in which I had worked in Porto Alegre, made good on his promise to create the conditions so that I could eventually return to that city. He gave me a list of equipment and supplies that he could make available for my group and offered to hire some of my current collaborators. Since both my wife and I longed for the less hectic life of Porto Alegre, and now that there seemed to be a possibility to continue my research at a decent level there, we said yes. The return to Porto Alegre was a big challenge: I would have to set up research from scratch in a place where there was virtually none in my field. Dick’s offer had caught me by surprise since I had arranged to spend 6 months with Hymie Anisman in Ottawa. So off to Ottawa we went for part of 1978, and later that year we moved from São Paulo back to Porto Alegre.

Ottawa and Then Porto Alegre

In Carleton University in Ottawa, Hymie and I studied the role of brain catecholamines in different forms of avoidance behavior (Izquierdo et al., 1979), and I also did some research with my old friend César Galeano in Michel Chrétien’s lab in the Institute de Récherches Cliniques of Montreal, a great place. We tried to study memory consolidation in mice carrying tumors that secreted pro-opiomelanocortin, the precursor protein to MSH, ACTH, and β-endorphin. We worked a lot and came out with the impression that consolidation and/or retrieval was hampered in those animals, but we had no good controls; regular mice not implanted with tumors were inadequate for that purpose, and so were mice with other kinds of tumors. Michel gave me an ampule of naloxone as a symbolic present and expressed his hopes that it could help me find some physiological role for endogenous opioids on learning and memory back home.

On the way back, Ivone, Juan, Eduardo, and I drove to Florida and spent several days with my good friend Steve Zornetzer in Gainesville. Steve had taught Esper Cavalheiro in São Paulo how to establish status epilepticus in rats by electrical stimulation of the hippocampus, and Esper then converted this into a new procedure to study that phenomenon using peripheral pilocarpine injections instead of electrical stimulation. Esper spent some years in France with Robert Naquet developing his research on epilepsy, and then returned to the Escola Paulista, where he introduced his new line of work, became chief of our old lab, and received world recognition for his discoveries in the field of temporal lobe epilepsy.

In Florida, overlooking an alligator pond, Steve Zornetzer discussed with me his new ideas on endogenous state dependency. He suggested that memories acquired and/or consolidated in a given neurohumoral/hormonal state should be best retrieved when the animal was in a similar state again. This would explain why in a situation of fear we do not readily recall alimentary behaviors but rather strategies to cope with fear, and why in situations of sexual excitement we recall sex rather than hunger or fear.

The Opioids

The return to the Federal University in Porto Alegre in early 1978 was one clear example of how things can change rapidly in countries with a high metabolic rate like Brazil. I was reallocated to the Department of Biochemistry, where I found some people interested in research. Dick had purchased much of the equipment we needed, and now there was even grant support, mostly from a State Agency. None of this had been there 4 years before.

While my new lab was being set up, I decided to test the posttraining effect of the naloxone given to me by Michel Chrétien on memory consolidation of shuttle avoidance and habituation to a tone. I found a large memoryenhancing effect with the drug in the two tasks, which could be reversed by morphine, which was amnestic on its own. My paper was immediately accepted (Izquierdo, 1979) and appeared more or less simultaneously with one by Jim McGaugh and his group showing the same in an inhibitory avoidance task, and a month after one by Michaela Gallagher describing a similar effect with intra-amygdala infusions. So it appeared that there could be a physiologic amnesic role for endogenous opioids. Among the collaborators of Jim’s paper was Beatriz Vásquez, my former graduate student from Córdoba, who was now married to an American and living in California.

I set up a group to study the opioid story in more detail. Maria Angelica Carrasco from Chile, Renato Dias, and the current Rector of that University, Carlos Alexandre Netto, were in that group, among others. Following Gallagher’s lead, we placed a bet on the amygdala and found that systemic naloxone increased cAMP levels in that area (Dias et al., 1979); so the amygdala became a putative site of action. Soon afterward, we found that the memory-facilitating effect of naloxone was due to the release of dopaminergic and noradrenergic mechanisms from tonic inhibition by endogenous opioids (Izquierdo and Graudenz, 1980). Right away, we found that at least two endogenous opioids, leu-enkephalin and β-endorphin, caused retrograde amnesia both for avoidance and habituation learning (Izquierdo et al., 1979), so the two were potential candidates for the purported “amnesic” role of opioids (Izquierdo, 1981). We found that different forms of behavioral training caused a sudden reduction of brain β-endorphin levels that lasted 3–6 hr and was interpretable as due to a release of the peptide (Izquierdo et al., 1980). At the same time, other laboratories were beginning to find that the effects of the enkephalins on memory were probably peripheral in origin, so the endorphins became better candidates as brain modulators than the enkephalins, so we concentrated on brain β-endorphin.

My good friend Béla Bohus in David de Wied’s lab in the Netherlands had shown that β-endorphin and other endorphins given prior to testing enhanced retrieval (see references in Izquierdo, 1982). I figured that perhaps Steve Zornetzer’s ideas on state dependency could apply to opioid effects. Brain β-endorphin could be acting posttraining in order to induce a state from which memories would become dependent, and naloxone would act by reducing this dependence. We subsequently found that this was the case (Izquierdo, 1980, 1981, 1989, 1991; Izquierdo and Netto, 1985) and so discovered endogenous state dependency for β-endorphin. In the early 1980s we extended the endogenous state dependency hypothesis to the posttraining amnestic effect of ACTH and the catecholamines at high doses (Izquierdo and Dias, 1983; Izquierdo, 1984, 1989).

The release of brain β-endorphin caused by training resulted from the novelty of the training procedure (Netto et al., 1985). Consequently, the presentation of a novel experience (a new environment, a new task, etc.) prior to retention testing enhanced retrieval, presumably by the release of brain β-endorphin, and this effect was counteracted by naloxone. This effect was observed in rodents (Izquierdo and McGaugh, 1985; McGaugh and Izquierdo, 1987) and in humans (Izquierdo and Chaves, 1986).

The opioid peptide story or stories made a big impact and our 1979 naloxone paper immediately became one of the most cited papers in the field of memory modulation. For a long time, naloxone was the most widely studied memory facilitating drug ever, in more tasks and species, including humans, than any other substance (see Izquierdo, 1991a).

Other findings of the 1980s were the effects of posttraining intracerebroventricular histamine on memory consolidation (Almeida and Izquierdo, 1986), which we have revisited recently (Da Silva et al., 2006); the peripheral origin of some of the effects of ACTH and adrenaline on memory (Almeida et al., 1983), and the finding with Larry Cahill and Jorge Brioni that posttraining diazepam, by interfering with the retroactive interference caused by other behaviors, could actually enhance the memory consolidation of avoidance learning (Cahill et al., 1986). This effect was reproduced in humans (Chaves et al., 1990) and may be related to some of the anxiolytic effects of benzodiazepines.

The Beginning of Something New

Toward the end of 1988, in a small Neuroscience symposium near Montevideo I met Jorge Medina, the last disciple of De Robertis, who had died in April that year, and was now in charge of the old master’s lab. Medina gave a talk on the presence of endogenous benzodiazepine-like compounds in the brain. He and I had lunch after his talk and we decided to work together on the benzodiazepine story. We became friends from that moment on. Through the years our friendship has grown and grown. In January 1989 I visited his lab for the first time, and we decided to start a collaboration uniting the two labs. We both felt that the opioids had already given us all they could give as memory modulators, that central and peripheral catecholamines and acetylcholine were already being studied by too many groups, so why not give the putative endogenous benzodiazepines a try. We thought that they might give us a handle into GABAA receptor–mediated control of memory consolidation, and that this could lead us eventually into the core mechanisms of memory. I had looked at the putative core mechanisms of memory with awe from a distance, as Jim McGaugh had done, over many years. I had felt that the field was not ripe yet for study, since so much of what was published on glutamatergic transmission and LTP had been hypothetical so far, and the eventual role of LTP in memory formation itself seemed difficult to prove. But, Jorge Medina and I now thought, perhaps endogenous benzodiazepine-like molecules could turn out to be a hitherto unsuspected powerful tool for the study of memory formation, entering through the back door of GABAergic transmission.

Jorge and his group and I and my group got together and decided to face the music of endogenous benzodiazepines and dance. At that time, for the first time in years, I had funds; Brazilian support of scientific research had increased a lot since 1973. Over the years, often with sudden oscillations that leave you breathless (and penniless), it continued to improve. One important collateral benefit of the association between Jorge’s lab and mine is that often when one of the two had no funds, the other did; so it has been great for survival.

The first experiments Jorge and I did were quite simple. The systemic administration of flumazenil (an antagonist of the benzodiazepine central-type receptor) or of n-butyl-beta-carboline (an inverse agonist at that receptor) enhanced, and that of the benzodiazepines diazepam or clonazepam depressed, acquisition of one-trial inhibitory avoidance. Flumazenil reversed the effect of the agonists. Flumazenil and the beta-carboline also enhanced retention of habituation to a sound (Izquierdo et al., 1990a,b). The findings suggested an inhibitory modulation of memory formation by endogenous benzodiazepine-like ligands acting on GABAA receptors in the brain.

Next, we studied the levels of endogenous benzodiazepine immunoreactive substances in the amygdala. Stepping down from the training platform decreased those levels and the ensuing footshock decreased it further. The simplest interpretation was that the immunoreactive substance(s) were released from storage sites by training. Pretraining intra-amygdala flumazenil enhanced memory consolidation (Izquierdo et al., 1990a). This further suggested an inhibitory role of endogenous benzodiazepines in memory formation. We then showed that the GABAA Cl– channel blockers, Ro5–4864 and picrotoxin given ip., icv., or into the amygdala caused memory facilitation, and that the specific blocker of the Ro5–4864 (and benzodiazepine) sensitive site of the GABAA receptor, PK11195, canceled the effect of Ro5–4864 on memory, but not that of picrotoxin (Da Cunha et al., 1991).

Then we reported that both habituation to a novel environment and inhibitory avoidance cause abrupt falls of brain regional levels of benzodiazepine-like molecules and that memory of the two tasks can be enhanced by intracerebral flumazenil microinjection. Stepping down from the platform and receiving a small footshock reduced benzodiazepine-like substance levels substantially in cerebral cortex, amygdala, septum, and especially in hippocampus as compared with untrained rats. The immediate posttraining bilateral intrahippocampal (but not intraseptal or intra-amygdala) injection of flumazenil at very low doses enhanced the retention of habituation; the drug enhanced retention of inhibitory avoidance when given into any of the three structures (Wolfman et al., 1991).

At this point, Medina and I were invited to write a review article on endogenous benzodiazepines and memory for Trends in Pharmacological Sciences (Izquierdo and Medina, 1991) and to edit a book on the subject of endogenous benzodiazepines (Izquierdo and Medina, 1993). We had found a new set of down-regulators of consolidation, the putative endogenous benzodiazepines, which could be placed side by side with β-endorphin and other substances as major modulators of memory. But given the difficulty to further characterize them chemically, and the strong possibility that the catecholamines, serotonin, and acetylcholine were much more important modulators, the field sort of fizzled out. There was no possibility of using flumazenil clinically as a memory enhancer in humans because the drug was found to be anxiogenic (Da Cunha et al., 1993). It is clinically used, however, to clear up the cognition deficit seen in liver insufficiency, in which the metabolism of endogenous benzodiazepine-like compounds is impaired (see Izquierdo and Medina, 1993).

We were left with a handle on GABAA receptors as strong modulators of memory consolidation, which is what we had been looking for. Meanwhile, progress on the various parallel and serial molecular processes triggered by glutamatergic receptors and involved in LTP had become substantial all over the world (see Izquierdo, 1993 for references).

The Real Thing

Jorge Medina and I finally found the courage to attack the core mechanisms of memory formation. Our strategy was very simple: We tested the effect on memory consolidation of bilateral infusions into CA1 in live, behaving animals of all the drugs that were being or had been tested by others on CA1 LTP in slices (see Bliss and Collingridge, 1993). We studied receptor agonists and agonists, drugs that affected the levels of second messengers, and stimulants and inhibitors of a variety of enzymes, mostly protein kinases, given at various posttraining intervals. In addition, we assayed the binding characteristics of the receptors, the levels of the second messengers, and the activity of the enzymes at the same posttraining intervals. The task chosen was one-trial inhibitory avoidance, then the most widely used in learning studies. It is acquired in a few seconds, so the moment of the initiation of its posttraining consolidation period can be readily determined, uncontaminated by the consolidation of further trials or the retrieval of preceding trials (Izquierdo and Medina, 1997; Izquierdo et al., 2006).

The time seemed finally ripe for the study of memory consolidation in the hippocampus and related brain areas. First, the hippocampus was now generally acknowledged to be the major site of posttraining consolidation (see Squire, 1987; Izquierdo and Medina, 1995, 1997; McGaugh, 2000 for references). Second, there was now a good electrophysiological model to guide our study: LTP, whose underlying mechanisms were beginning to be unraveled (Bliss and Collingridge, 1993). LTP involves long-lasting changes of synaptic strength that, in CA1, rely first on glutamate receptor activation, followed by that of a sequence of protein kinases many of which cross-talk with each other, and then by gene activation and protein synthesis.

We thought that the search for the actual occurrence of LTP during memory consolidation, which seemed to worry most investigators up to the early 1990s (Izquierdo, 1993; Bliss and Collingridge, 1993), was less important than the search for the biochemical steps of memory consolidation itself. In 1991–1992, too little was known about the molecular processes of consolidation and almost nothing about their timing in the posttraining period; but a lot was beginning to be known about LTP. If the sequence of molecular events of consolidation in CA1 turned out to be similar to that of local LTP, then they would be easier to interpret in terms of synaptic changes, regardless of whether actual LTP can or cannot be detected during consolidation. (As will be seen, it can).

As had been the case with LTP (see Bliss and Collingridge, 1993; Izquierdo, 1993; Izquierdo and Medina, 1995 for references), our approach to the study of the biochemical basis of memory formation in the hippocampus and elsewhere was mostly pharmacological, using localized microinfusions of drugs with specific molecular effects (enzyme inhibitors, neurotransmitter agonists or antagonists, etc.). But for us it was also important to measure the activity and/or levels of those substrates at various times after training; that is, we wanted to know not only the nature but also the time course of the changes. Such biochemical measurements are usually not done in LTP studies, chiefly because these are carried out in slices. Since we used whole, behaving animals in order to measure memory directly, we were also able to carry out biochemical determinations in the hippocampus during various phases of memory formation directly (Izquierdo and Medina, 1997; Izquierdo et al., 2006). The importance of establishing the time course of each biochemical step studied was because we needed to compare the pharmacological and biochemical measures not only with each other but also with those known to occur in LTP (Izquierdo et al., 2006). The use of genetically manipulated animals was impractical because in them the changes are permanent and we were keen on the determination of time courses of reversible changes. Conditional knockouts or virus-transported proteins were not available in those days.

Over 200 students and collaborators were to participate in this work over the next 20 years. Those with whom I published more papers were Martin Cammarota, Lia Bevilaqua, Ramon Bernabeu, Luciana Izquierdo (the wife of my son Juan), Monica Vianna, Claudia Wolfman, Lina Levi de Stein, Daniela Barros, Joao Quevedo, Carlos Alexandre Netto (currently Rector of the Federal University at Porto Alegre), Roger Walz, Marino Bianchin, Jorge Quillfeldt, Diana Jerusalinsky, Marcia Chaves, Claudio Da Cunha, Juliana Bonini, and Janine Rossato. One of them, Claudia Wolfman, who died very young, had attended the same high school I did, but 25 years later; so we shared many memories a quarter of a century out of phase. She was a great friend.

From Neurotransmitters to Early Genes

Our first two papers on the molecular basis of memory consolidation were on the neurotransmitters involved in that process, and they ended up coming out in the same issue of Behavioral and Neural Biology (Izquierdo et al., 1992; Jerusalinsky et al., 1992). In the first we showed that immediate posttraining bilateral infusion of the glutamate NMDA receptor antagonist, AP5, into the dorsal CA1 region of the hippocampus, the basolateral amygdala, or the medial septum caused retrograde amnesia for inhibitory avoidance and for habituation learning in rats. The medial septum and basolateral amygdala are two major connections of the hippocampus. Similar effects were obtained with scopolamine, muscimol, and timolol. On the contrary, glutamate, oxotremorine, and noradrenaline caused retrograde memory facilitation. This indicated that glutamate NMDA, cholinergic muscarinic, and β-noradrenergic receptors were necessary for memory consolidation of the two tasks immediately after training in the three structures, and that GABAA receptors inhibited it. In the second paper we studied the posttraining time course of the amnestic effect of AP5 and of the glutamate AMPA receptor blocker, CNQX, given into CA1, the basolateral amygdala, and the entorhinal cortex. We found that AP5 was amnesic when given into any of the three structures only shortly after training, but CNQX was amnesic when given up to at least 3 hr posttraining in the one-trial avoidance task. The results with the time course of the NMDA and the AMPA receptor blocker were reminiscent of work carried out on CA1 LTP by my good friend Klaus Reymann, from Magdeburg (see Izquierdo, 1993). Subsequently we found a very protracted posttraining time course of 3H-AMPA binding to hippocampal cells (Cammarota et al., 1995), in agreement with data in the literature on other hippocampus-dependent tasks (see references in Izquierdo and Medina, 1995, 1997). The immediate posttraining role of metabotropic glutamate receptors in consolidation was then ascertained first through the intrahippocampal administration of a nonspecific antagonist (Bianchin et al., 1994) and years later through the use of specific antagonists (Bonini et al., 2003).

Importantly, our findings were compatible with the widespread idea that LTP or a very similar process could underlie memory consolidation, and in addition agreed with those of many others available at that time on a key involvement of muscarinic cholinergic and β-noradrenergic receptors in the modulation of memory formation in the areas studied (see Izquierdo and Medina, 1997; Izquierdo et al., 2004, 2006; Prado et al., 2006 for references).

Soon afterward, we found that blockade of the posttraining hippocampal synthesis of the so-called retrograde messengers linked to cGMP-dependent kinase (Bernabeu et al., 1997b), CO (Fin et al., 1994; Bernabeu et al., 1995), and NO (Fin et al., 1995), and blockade of the platelet-activating factor (Izquierdo et al., 1995) disrupted memory consolidation. This suggested a role of the three messengers in memory consolidation in hippocampus (Medina and Izquierdo, 1995). This was to be expected from the fact that all of them enhance glutamate release (see Medina and Izquierdo, 1995; Bernabeu et al., 1997a). We have recently extended this role of NO to the basolateral amygdala (Zinn et al., 2009). The NO mechanism in amygdala is linked by a β-noradrenergic mechanism to the expression of the multifaceted brain-derived neurotrophic factor (BDNF) and is involved in consolidation of object recognition memory (Furini et al., 2009).

Following the steps of my good friend Aryeh Routtenberg, we investigated the role of hippocampal protein kinase C in memory consolidation of the one-trial step-down avoidance task. The postinduction administration of inhibitors of this enzyme family hinders the establishment of long-lasting LTP (see references in Izquierdo, 1993). In accordance with this, we observed that the infusion of inhibitors of this enzyme into CA1 caused retrograde amnesia; the effect was maximum 30 min posttraining and then declined over the next 2 hr (Jerusalinsky et al., 1993). Activity of the enzyme, and phosphorylation of its substrate, the presynaptic protein GAP-43, followed a similar time course, with a peak 30 min posttraining and then a decline (Bernabeu et al., 1995). The main PKC isoform involved was later identified as being PKCβ1 (Paratcha et al., 2000). More recently we described a role for PKC in memory consolidation also in amygdala and parietal cortex (Bonini et al., 2005).

Then we studied the involvement of hippocampal calcium calmodulin kinase II (CaMKII) in memory consolidation. The enzyme had been found to play a crucial role in the early phase of CA1 LTP in part mediated by phosphorylation of the AMPA-sensitive GluR1 (Bliss and Collingridge, 1993). Infusion of the CaMKII inhibitor KN62 into CA1 or the basolateral amygdala in the first couple of hours after inhibitory avoidance training caused retrograde amnesia; the effect was lower if infusions were delayed 1 or 2 hr (Wolfman et al., 1994). Time- and training-dependent increases in CaMKII activity correlated with GluR1 phosphorylation were reported at about the same time for LTP and for one-trial avoidance (see Cammarota et al., 1998).

Next, we turned to the cAMP-dependent protein kinase (PKA) in hippocampus. This enzyme had been shown by Kandel and his coworkers to be important for the phosphorylation of the constitutive transcription factor CREB, a step crucial for the establishment, 2–4 hr after induction, of LTP (see Izquierdo and Medina, 1995, 1997). Phosphorylated CREB is a molecular marker of consolidation processing and novelty detection (Viola et al., 2000; Izquierdo et al., 2001). We found a peak of hippocampal PKA activity immediately after one-trial avoidance training, followed by a second peak 2–6 hr later. Both peaks correlate with increases in cAMP levels (Bernabeu et al., 1996), with the requirement of hippocampal D1 receptor activation, and with peaks of pCREB levels (Bernabeu et al., 1997a). The existence of the two peaks agreed with previous findings by Hansjürgen Matthies and his collaborators in the 1960s, and with our own later finding, of two simultaneous peaks of gene expression (Igaz et al., 2002) and both anisomycin- (Quevedo et al., 1999) and rapamycin-sensitive protein synthesis (Slipczuk et al., 2009).

Then we studied the participation of the hippocampal extracellularly regulated kinase (ERK) system in consolidation. As had been the case with PKA, the involvement of the ERK system in the establishment of LTP had also been established before—in this case by David Sweatt and his group in Texas. Inhibitors of the enzyme that converts ERK1 into ERK2 infused at different times after training in CA1 caused retrograde amnesia for the avoidance task (Walz et al., 1999, 2000; Alonso et al., 2002b). Cammarota et al. (2000) showed that the posttraining increases of CaMKII, PKC, PKA, and ERK2 triggered by one-trial avoidance learning required the previous activation of NMDA receptors in CA1 at the time of training. The ERK activity increase that follows behavioral training in the hippocampus is related to the aversive component of the tasks (Alonso et al., 2002a, b).

We demonstrated a role in consolidation for a variety of other kinases as well, at different times after training: phosphoinositide 3-kinase (Barros et al., 2001), the N-terminal Jun kinase (Bevilaqua et al., 2003a); Src-kinase (Bevilaqua et al., 2003b), and the p38 kinase (Rossato et al., 2006). In all cases their role and its time course were similar to those reported for LTP (see the last three mentioned papers for references).

We also showed that, again much like in LTP, nerve growth factor (NGF) and particularly BDNF are important for memory consolidation, the former in the hippocampus (Walz et al., 2000) and the latter both in the hippocampus (Alonso et al., 2002) and the parietal cortex (Alonso et al., 2005); in the former for both short- and long-term memory and in the latter only for long-term memory consolidation.

We found that the early genes Fos, Jun, Src, Elk, Fra-1, and zif268 are all produced in the hippocampus after training in the one-trial avoidance task (Cammarota et al., 2000; Paratcha et al., 2000). The findings fitted with those of others in other tasks (see Izquierdo and Cammarota, 2004).

Meanwhile, a Major Change

In May 2003 I reached my 25 years of service at the Federal University and retired. Fortunately I received an offer from the Pontifical Catholic University of Rio Grande do Sul (PUCRS). It was the kind of offer one cannot refuse: They wanted me to install a brand new Memory Center, so they offered to build a new set of laboratories and asked me to bring my current collaborators to work with me. So I accepted, and through the good offices of the Catholic University the transition was very smooth and we were all able to keep on working more or less as usual while the complex process of moving went on. A bit like the last part of Haydn’s “Farewell” symphony in which the musicians leave one by one but the music goes on. Here we did leave, but we were moving to another orchestra just a few blocks away. The smoothness of the move was guaranteed by the efforts of Lia Bevilaqua and our invaluable technician and factotum, Daniela Montenegro Cardoso (wife of my son Eduardo). The students (Janine Rossato, Juliana Bonini, Julia Clarke, Ramon Lima, Weber Da Silva, Cristiano Köhler) and our two postdocs (Martin Cammarota, Lia Bevilaqua) came along.

The Memory Center of PUCRS was officially inaugurated in 2004. By early 2005 the transition had been completed, and all our research activity has been since then carried out at the Memory Center of the Pontifical Catholic University. I was appointed Full Professor of Neurology at the Catholic University Medical School and head of the new Center. Martin Cammarota was shortly afterward appointed Associate Professor and vice-director of the new unit. More recently Lia Bevilaqua and Janine Rossato were also appointed Associate Professors, and we were given funds for four postdoctoral fellows in the new lab.

On with the Show

During this transition, with my good friends Ricardo Brentani and Vilma Martins, from the Ludwig Institute of São Paulo, we showed that posttraining activation of PKA and the ERK pathway requires binding of the physiological prion protein to laminin (Coitinho et al., 2006) and to the stress inducible factor I (Coitinho et al., 2007), which may be among the hitherto unknown physiological roles of the physiological prion protein (Linden et al., 2008). The knockout of this protein in mice or the action of an antibody against it in rats results in memory impairments visible only after the age of 8–9 months (Coitinho et al., 2003).

With my friends Marco and Vania Prado, now in the Robarts Research Institute of the University of Western Ontario, we examined the deficits of learning and memory in mice unable to express the vesicular acetylcholine transporter (Prado et al., 2006).

In the new lab we investigated the effect of a number of drugs that influence CaMKII, ERK, and PKA activity when given at various times posttraining on retention of the one-trial task (Rossato et al., 2004; Bonini et al., 2005; Bevilaqua et al., 2005). We found that although the effects are qualitatively similar across brain structures (basolateral amygdala, entorhinal cortex, parietal cortex), their time course is different in each one of them. So these other brain structures probably also participate in consolidation using the various signaling pathways studied, but in sequences different from those of CA1 LTP (Izquierdo et al., 2006).

We found that synchronously with the two peaks of transcription-dependent, anisomycin-sensitive protein synthesis in CA1, two parallel peaks of mTOR-mediated translation are also required in the hippocampus for memory consolidation of both the one-trial avoidance task (Bekinschtein et al., 2007) and an object recognition task (Myskiw et al., 2008). The m-TOR-mediated translation occurs mostly at dendrites making use of preexisting mRNAs, is regulated by BDNF and mediates the synthesis of GluR1, essential for memory formation (Slipczuk et al., 2009).

Thus, step by step, over 15 or so years we have shown that memory consolidation of one-trial avoidance and other tasks uses the CA1 region of the hippocampus and involves the same steps that have been described for local LTP in the same sequence and with the same time course (Izquierdo and Medina, 1997; Izquierdo et al., 2006). In addition, we showed that other brain regions are also involved, among them the basolateral amygdala, the medial septum (Izquierdo et al., 1992), the entorhinal cortex (Izquierdo et al., 1995, 1997; Ardenghi et al., 1997), and the anterodorsal and medial prefrontal cortex (Izquierdo et al., 2007). Several of the molecular changes that occur in CA1 and are also seen in the basolateral amygdala depend on the previous activation of NMDA receptors in the former and on that of noradrenergic β-receptors in the latter (Cammarota et al., 2008). In CA1 but not in the other regions the mechanisms of consolidation are similar to those of CA1 LTP (Izquierdo et al., 2006), and indeed LTP of the CA3-CA1 Schaeffer collaterals pathway was described that same year during the consolidation of one-trial inhibitory avoidance by Whitlock et al. (2006) and in trace eyeblink conditioning by Gruart et al. (2006). Furthermore, LTP of the CA3-CA1 synapse carried out prior to training occludes acquisition of the eyeblink task and others. These findings were extended recently to a nonaversive task, object recognition, whose consolidation also requires the CA1 region (Clarke et al., 2010). This last finding points to a general role of the molecular chain of events of LTP in the processing of memory consolidation in CA1 and was obtained in collaboration with José María Delgado-García’s group in Seville.

So we have identified the main molecular events underlying memory consolidation in CA1 in live, behaving animals and found them to be very similar to those of LTP in hippocampal slices. This, of course, can be taken to endorse the numerous postulations of LTP as a (if not the) substrate of memory, particularly hippocampal LTP (see Bliss and Collingridge, 1993; Izquierdo and Medina, 1995; Whitlock et al., 2006 for references). However, we still do not know if the similarities between the biochemistry of LTP and memory consolidation in CA1 simply reflect the fact that both processes require a similar molecular chain of events leading to synaptic strengthening, or indicate instead a role of actual LTP in memory formation. The occurrence of LTP at the CA3-CA1 synapse seen during consolidation could be a side effect of the molecular changes, rather than a causally related phenomenon. Obviously other brain areas that consolidate memories use different processes and/or different forms of LTP for this, inasmuch as their posttraining biochemistry is different from that of CA1 (i.e., entorhinal, parietal, and cingulate cortex, etc.; Izquierdo et al., 2006).

Short- and Long-Term Memory

Memory can be measured in the first few minutes or hours after acquisition, or many days or even years later. Is it the same memory trace at the early and the late measuring periods? In other words, are short- and long-term memory (STM, LTM) parts of a single process, or is each of them a different form of memory? William James raised this fundamental question in his famous book Principles of Psychology (1890), in which he actually termed them primary and secondary memory. STM has long been known to decline fast and to be labile; LTM supposedly contains less information but is much more stable (although this view has been highly contested in the past 10 or 20 years).

Many people grew accustomed to thinking that memories begin as short term and are then transformed by new proteins or something else into longterm memories. But if this were so, a suppression of STM should necessarily prevent LTM from taking place. This is not the case in clinical observations. Indeed, a failure of short-term memory with preserved long-term memory is typical of delirium, and it has been reported in patients with neocortical lesions (Warrington and Shallice, 1969).

We studied the dichotomy between STM and LTM in detail in a series of articles that began with a note in Nature in 1998. To make a very long story short, over the years we reported that 11 different drug treatments given into either hippocampus or entorhinal cortex selectively block the shortterm memory of one-trial inhibitory avoidance measured 1.5 or 3 hr after training without affecting the LTM for the same task in the same animals, and another 15 treatments affect both memory types differently (i.e., they enhance STM and depress LTM, or do not affect one of the two but strongly affect the other; Izquierdo et al., 1998, 1999, 2000, 2001; Vianna et al., 1999). Besides, we were able to extricate in relative detail the separate involvement of discrete signaling systems, such as the PKA (Vianna et al., 1999) and the ERK pathways in the hippocampus in both STM and LTM (Igaz et al., 2006). Depending on the time at which inhibitors or stimulants of the enzymes are infused, they can separately affect one or the other memory type by actions on different substrates (Vianna et al., 1999; Izquierdo et al., 2000, 2001).

We have thus shown that the STM that lasts up to 3 hr and the LTM that lasts days or weeks involve two distinct, parallel but essentially separate processes. There are several types of STM, however; one of them lasts a few seconds or minutes and is used as working memory (see Izquierdo et al., 2001, 2007), and others last several hours and are often called intermediate memories. A comparative analysis of these other STM types is desirable, but the limits between them are tenuous and that analysis is difficult (Izquierdo et al., 2007).

Does the Long-Term Trace Travel?

In most accounts of memory, declarative memories are supposed to depend on the hippocampus for a limited period of time, after which the neocortex can support memory on its own (Squire, 1987).

In a study that became instantly popular because it superficially appeared to fit with that notion, we found that the AP5- and muscimol-sensitive mechanisms thought to be responsible for the onset of memory consolidation of inhibitory avoidance enter into play in hippocampus and amygdala right after training, 30–60 min after training in the entorhinal cortex, and 60–180 min after training in the posterior parietal cortex (Izquierdo et al., 1997). More recent research suggests that different molecular systems involved in consolidation enter into play at different times in the first 3–6 hr that follow one-trial avoidance training in different brain areas (Bonini et al., 2003; Izquierdo et al., 2006). Retrieval of this task can be blocked by CNQX given into any of the four structures 1 day after training, or into entorhinal or parietal cortex but not hippocampus or amygdala 1 month later, or into the parietal cortex but not in the other three regions 2 months later (Izquierdo et al., 1997).

Perhaps memory traces do not “travel,” but are recorded in rapid sequence or simultaneously in multiple sites, possibly using different biochemical processes in each; and then some of the sites lose importance over time, because of disuse, aging, or other factors. The different persistence of the traces in different sites may account for what many regard as its “traveling” from one site to another over time.

Extinction Learning

In recent years, attention was drawn to consequences of retrieval upon memory (see Vianna et al., 2001; Cammarota et al., 2005). It had been known since Pavlov (1927) that repetition of conditioned stimuli without reinforcement leads to extinction, which is a learned inhibition of retrieval. If animals or humans, after having been trained to associate a given set of stimuli (CS) with another set of stimuli (US), are presented repeatedly with the CS alone, omitting the US, they learn to associate the CS with the lack of US. The new association (CS–no US) replaces the former CS–US association, and subjects learn to inhibit performance of the original conditioned response.

Knowledge of the mechanisms of extinction is important both for physiology and for clinical practice. Extinction is widely used, often under the name of “exposure therapy” for the treatment of the posttraumatic stress disorder and other forms of fear-related memory disturbances (Izquierdo et al., 2008); patients are reexposed to aspects of a traumatic experience but without the fear or the consequences originally associated with it. So in 2001 we began to study the possible role of the hippocampus, basolateral amygdala, and entorhinal cortex in extinction of the one-trial avoidance task, and the participation therein of signaling pathways, gene expression, and protein synthesis.

We clearly established that the initiation of extinction stems directly from retrieval, indeed from some of the molecular substrates of retrieval: It is blocked by a single hippocampal infusion of an NMDA receptor antagonist; or of inhibitors of PKA, CaMKII, and ERK; or of inhibitors of gene expression or protein synthesis given right before or after the first of several retrieval sessions (Vianna et al., 2001, 2003; Szapiro et al., 2003; Cammarota et al., 2004, 2005). Hippocampal PKA and ERK participate in the retrieval process (see Izquierdo et al., 2006). They are, of course, also necessary for the original consolidation (see earlier). Importantly, all these systems are required for extinction at the time of retrieval, but not minutes or hours later; therefore, they do not operate in sequence in extinction as they do in consolidation, but rather more or less simultaneously. Several of the same molecular processes (NMDA receptors, protein synthesis, PKA, and CaMKII) also play a key role in extinction in the basolateral amygdala (Vianna et al., 2004) and in the entorhinal cortex (Bevilaqua et al., 2006).

So we added several brain structures to the map of brain regions that control extinction and showed some of the molecular events involved in each. In all likelihood, extinction depends on the operation of different areas for different types of memory, and these act in concert in order to acquire the inhibition of the original learned response (see Izquierdo et al., 2008). Importantly, we established that extinction effectively is initiated by retrieval of the memory-to-be-extinguished, and it uses molecular processes involved in retrieval itself (Vianna et al., 2001, 2003; Szapiro et al., 2003; Cammarota et al., 2004, 2005; Bevilaqua et al., 2006). In some particular tasks other brain regions may play a role in extinction, such as for example the insular cortex in conditioned taste aversion, a task that depends highly on that area (see references in Izquierdo et al., 2007; Quirk and Mueller, 2008).

Importantly, we also observed that, in the rat, an increase in the time of exposure to the lack of a footshock in an inhibitory avoidance extinction setting (i.e., the “no-US” component of the task) enhances extinction to the point of uninstalling a fear-motivated memory (Cammarota et al., 2003). This is of course directly applicable to exposure therapy.

Besides extinction, we also studied the more recently described process of reconsolidation that also originates from unreinforced retrieval, particularly if this is carried out shortly after the original training (Bevilaqua et al., 2010). After some difficulty in obtaining it in inhibitory avoidance (Izquierdo and Cammarota, 2004; Cammarota et al., 2004), we succeeded in detecting reconsolidation in tasks in which it had not been described before (object recognition, spatial learning), and its dependence on hippocampal protein synthesis (Rossato et al., 2006, 2007). The conditions under which extinction predominates over reconsolidation or vice versa are not yet known; except that the latter is not seen in test sessions carried out more than 2–5 days after the last training session.

Memory Persistence

Some LTMs may last just a day or two, and others may persist for many weeks or for a lifetime. In some cases the long persistence is accounted for by the degree of emotional arousal at the time of consolidation (McGaugh, 2000); that is, we all remember where we were and whom we were with when the 9/11 attacks occurred or when John Kennedy was shot. But in many cases persistence might have other causes: Many of us remember Ohm’s Law or the Pythagoras theorem from high school regardless of their low emotional content.

In one of my periodical visits to Jorge Medina’s lab, in 2006, we discussed the possibility that there could be some mechanism hours or days after memory consolidation that would ensure the persistence of some memories for a long time, independently of retrieval. So we talked it over with our common friend Martin Cammarota, who had obtained his Ph.D. with Jorge and has been in my lab since 2002. Subsequently we carried out a series of experiments in both labs in order to investigate putative mechanisms of persistence.

Our first findings in this new line came out in late 2007 (Bekinschtein et al., 2007a) and early 2008 (Bekinschtein et al., 2008b). We found that anisomycin given bilaterally into the CA1 region of the rat hippocampus 12, but not 9 or 24 hr, after one-trial inhibitory avoidance training greatly impaired memory of the task measured 7 but not 2 days later. The same effect was obtained using an antibody against BDNF instead of anisomycin. Thus, intact protein synthesis, possibly that of BDNF, is needed in CA1 12 hr after training in order for memory to persist beyond 2 days and for at least 1 week (Bekinschtein et al., 2007b). This is 6 hr after posttraining consolidation is officially complete (McGaugh, 2000; Izquierdo et al., 2006).

The administration of human recombinant BDNF into CA1 12 but not 9 or 24 hr after training stimulated memory persistence beyond 2 days and overcame the deleterious effect of anisomycin or the antibody on memory persistence. In addition, we observed an increase of BDNF immunoreactivity in CA1 12 but not 9 or 24 hr posttraining that could be prevented by a BDNF-related antisense oligonucleotide but not by a missense oligonucleotide. The effects of BDNF on persistence depended on the phosphorylation of ERK1 and correlated with the enhanced expression of c-Fos and zif-268 24 hr after training. Inhibition of the synthesis of BDNF 12 hr after training by an antisense oligonucleotide impairs memory persistence beyond 2 days (Bekinschtein et al., 2008). These results added to several others on the effects of BDNF on memory obtained in our laboratories (see Alonso et al., 2005; Bekinschtein et al., 2008a) and pointed to a role of this substance in memory persistence as a major effect.

What triggers the release of BDNF that occurs in CA1 12 hr after training that enhances memory persistence beyond 2 days? Some observations in humans suggested that it could be a dopaminergic mechanism acting about12 hr after learning. After the age of 40 years, normal subjects remember correctly the name and the two main actors of a movie seen incidentally on TV 2 days before, but not those of a movie seen 7 days before; this forgetting was overcome by a low dose of the dopaminergic drug, methylphenidate (Izquierdo et al., 2008).

So we investigated the possible role of activation of the ventral tegmental area (VTA), a dopaminergic nucleus that innervates the CA1 and other areas of the brain (see references in Izquierdo et al., 2008 and Rossato et al., 2009). Infusion of the D1 dopamine receptor antagonist SCH23390 into CA1 12 hr, but not immediately or 9 hr, after one-trial avoidance made rats amnestic for this task 7 or 14, but not 2 days, after training with a 0.8 mA footshock. The effect was counteracted by intrahippocampal BDNF. In animals trained with a 0.4 mA footshock the memory did not last more than 2 days in controls but lasted 7 or 14 days in those treated with intrahippocampal infusions of the D1 agonist, SKF38393. In animals trained with a 0.8 mA footshock there was, and in those trained with 0.4 mA footshock there was not, an increase of hippocampal BDNF levels; the former was enhanced by SKF38390 and depressed by SCH23390. Stimulation of the VTA with NMDA 0 or 12 hr posttraining caused similar effects to those of BDNF or SKF38393 given into CA1. Inhibition of glutamate receptors with AP5 given into the VTA immediately or 12 hr posttraining had similar effects to those of intrahippocampal SCH23390 or anti-BDNF administration. Thus, the persistence of long-term memory depends on activation of VTA-hippocampal dopaminergic connections and can be specifically modulated by manipulating this system at definite time points (Rossato et al., 2009). The VTA probably detects saliency of the data to be memorized (see Izquierdo et al., 2008; Rossato et al., 2009).

An additional, possibly related mechanism that regulates memory persistence occurs at 24 hr after training in the hippocampus: It involves the synthesis of various postsynaptic proteins in hippocampus (Bekinschtein et al., 2010) triggered by a late wave of c-Fos 12 hr posttraining (Katche et al., 2010). Data suggest this late event is linked to the dopamine regulated BDNF mechanism discussed earlier.

The VTA, BDNF, and c-Fos-dependent mechanisms of persistence are independent of sleep: They have been observed in animals trained in the morning or in the evening; that is, at the beginning or the end of the rat’s sleep cycle (Bekinschtein et al., 2007b, 2008b, 2010; Rossato et al., 2009; Katche et al., 2010).

The findings noted in this section explain why some consolidated memories persist longer than others that had been similarly acquired and presumably consolidated. They point to the existence of one or more late postconsolidation mechanisms regulating memory persistence (Medina et al., 2008). These mechanisms can legitimately be viewed as the links between the initial consolidation process as defined by McGaugh (1966, 2000), which is now often called cellular consolidation, and the process that maintains long-term memory over weeks, months, or years, which is sometimes called systems consolidation (see Katche et al., 2010 for references). Cellular consolidation takes place in the hippocampus for many memories (see Clarke et al., 2010) and lasts a few hours (Izquierdo et al., 2006). Systems consolidation is believed to take place in the neocortex and to last weeks, months, or years (see Squire, 1987; Izquierdo et al., 1997). It is convenient for the duration of memory that the processing of the original memory trace persists long enough in the hippocampus so as to permit the initial steps of systems consolidation in the neocortex (Medina et al., 2008; Katche et al., 2010).

In addition, the findings commented in this section throw some light into the well-known fact that after 40 years of age—not necessarily in old age—we remember not-so-important things for a shorter time than we do when young. This may be a boon for a useful cognitive life. Perhaps to forget where we parked our car last Friday helps to remember where we parked it today. Perhaps to forget about last week’s TV movie may help us concentrate on the results of the experiment we did last week or the business we have to do tomorrow. There must be a reason why world leaders are usually not chosen among those below 40 in fields involving some sort of intellectual endeavor, from science to business and politics. Maybe it is useful to forget the not-so-important memories of a few days ago and concentrate on what really matters, including “the big picture.” Borges said so much in Funes the Memorious: “One needs to forget in order to make generalizations, in order to think.”

It seems that memory persistence is a postconsolidational phase that involves several distinct events in the hippocampus 12 hr after acquisition, dopaminergic activation by fibers coming from the VTA and hippocampal BDNF expression and ERK-mediated mechanisms, and c-Fos production; 24 hr posttraining, there is a new round of learning-related Fos-triggered protein synthesis. It also seems clear that the phase of memory that determines persistence is very important and that without it consolidation (or eventually reconsolidation) would be of little consequence in the long term. The obliteration of the persistence phase by dopamine blockers, or by an antibody against BDNF given into CA1 (Bekinschtein et al., 2008; Rossato et al., 2009), or of an antisense oligonucleotide that blocks c-Fos expression (Katche et al., 2010), 12 hr posttraining, effectively cancels the memory that had been acquired and consolidated. It becomes as if it had never existed.

Looking Back

While my work went on, Ivone’s life and mine were changing slowly, but at a faster pace than we were conscious of. The two boys grew, became adults, got married, and had their own children, who are now our dear grandchildren, Francisco, Felipe, Maria Eduarda, and Mauricio. Their mothers are like two daughters for us.

We visited many lands and made many friends. Actually, one of the assets of being a scientist is, in my opinion, the large number of good friends one can make along the way.

My life has been intense and complex, and it involves many ties with many people. So, perhaps like everybody else, I became a complex embroidery of thoughts, reasonings, beliefs, and feelings that have their origin outside of me. I owe a lot to many of the persons mentioned in this text. The avatars of Argentine, Brazilian, and world politics no doubt had a big influence too, even though I stayed clear of them as much as I could.

I was invited to many meetings all over the world and received over 50 major national or international prizes and distinctions. In 2007 I was elected as a foreign associate of the National Academy of Sciences, which I view as one of the highest distinctions I ever received, together with my appointments as Doctor Honoris Causa of the University of Paraná and Honorary Professor of the Universities of Buenos Aires and Córdoba.

I participated a lot as advisor to the two major financing agencies of Brazil, the Financiadora de Projetos and the National Research Council, and to the large cohort of scientists who articulated the current very extensive program of fellowships for graduate studies of Brazil. This program turned Brazilian science from the almost secret practice of a few into an endeavor of thousands. Once we get rid of the last remnants of amateurism and bureaucratism, Brazilian science and in particular neuroscience will grow fast. I am also advisor to scientific agencies of 20 countries of the Americas, Europe, and Asia. I am very proud of being one of the initiators and managers of the Brazil-Argentina agreements on Science & Technology, which has now become a large structure. I was assigned to this job because of the success of my long collaboration with Jorge Medina’s lab, the longestlasting and most productive joint scientific project between the two countries ever (Izquierdo, 2008).

So I was an Argentine neuroscientist during the first half of my life and a Brazilian neuroscientist during the second half. Legally, I have the two nationalities, which makes me glad for having been able to install memory research and good neuroscience centers in the two countries and thus contribute to their scientific development.

There Are More Things

This autobiography would be incomplete if I did not mention the key role that literature and music have played in my life. I have always been an avid reader and enjoy the sound and often the fury of words. I have written literature sporadically since 1950 and regularly since 1991. I published two books on memory for the lay public, as well as several books of essays and short stories in Spanish and in Portuguese. Writing began as a hobby; now it is a need.

Music has always been important for me. Beethoven, Mozart, Ellington, and Reinhardt play a major role in my life. Going to the opera, to concerts, or to the Spanish zarzuelas with our parents was a big thing for my sister and me during childhood. Now, Ivone and I sing pop songs regularly in a club in our neighborhood—she much better than I. We both had some formal training in music: I studied classic guitar between the ages of 7 and 18, and she studied the piano and practiced singing. After I entered medical school I never found the daily hours of training I would have needed to play the guitar reasonably well, and I felt frustrated. But now my grandson Felipe plays much better than I ever did. Every now and then he stays at our home over the weekend and Ivone and I wake up softly in the middle of the night with some beautiful music by Bach, Sor, or Tárrega coming from the living room. That is as close to heaven one can get while still alive. That, and talking about life with my loved ones, including some I used to play with on the floor (alas!) so few years ago.

Selected Bibliography

Alonso M, Bekinschtein P, Cammarota M, Vianna MR, Izquierdo I, Medina JH. Endogenous BDNF is required for long-term memory formation in rat parietal cortex. Learn Mem 2005;12:504–510.

Alonso M, Vianna MR, Depino AM, Mello e Souza T, Pereira P, Szapiro G, Viola H, Pitossi F, Izquierdo I, Medina JH. BDNF-triggered events in the rat hippocampus are required for both short- and long-term memory formation. Hippocampus 2002a;12:551–560.

Alonso M, Viola H, Izquierdo I, Medina JH. Aversive experiences are associated with a rapid and transient activation of ERKs in the rat hippocampus. Neurobiol Learn Mem 2002b;77:119–124.

Ardenghi P, Barros D, Izquierdo LA, Bevilaqua L, Schröder N, Quevedo J, Rodrigues C, Madruga M, Medina JH, Izquierdo I. Late and prolonged memory modulation in entorhinal and parietal cortex by drugs acting on the cAMP/protein kinase A signaling pathway. Behav Pharmacol 1997;8:745–751.

Barros DA, Mello e Souza T, Choi H, DeDavid e Silva T, Lenz G, Medina JH, Izquierdo I. LY-294002, an inhibitor of phosphoinositide 3-kinase given into rat hippocampus impairs acquisition, consolidation and retrieval of memory for step-down inhibitory avoidance. Behav Pharmacol 2001;12:629–636.

Bekinschtein P, Cammarota M, Igaz LM, Bevilaqua LR, Izquierdo I, Medina JH. Persistence of long-term memory storage requires a late protein synthesis- and BDNF-dependent phase in the hippocampus. Neuron 2007a;53:261–267.

Bekinschtein P, Cammarota M, Izquierdo I, Medina JH. BDNF and memory formation and storage. Neuroscientist 2008a;14:147–156.

Bekinschtein P, Cammarota M, Katche C, Slipczuk L, Goldin A, Rossato JI, Izquierdo I, Medina JH. BDNF is essential to promote persistence of long-term memory storage. Proc Natl Acad Sci USA, 2008b; 105:2711–2716.

Bekinschtein P, Katche C, Slipczuk L, Gonzalez C, Dorman G, Cammarota M, Izquierdo I, Medina JH. Persistence of long-term memory storage: New insights into its molecular signatures in the hippocampus and related structures. Neurotox Res 2010;14: Epub ahead of print.

Bekinschtein P, Katche C, Slipczuk L, Igaz LM, Cammarota M, Izquierdo I, Medina JH. mTOR signaling in the hippocampus is necessary for memory formation. Neurobiol Learn Mem 2007b;87:303–307.

Bernabeu R, Bevilaqua L, Ardenghi P, Bromberg E, Schmitz P, Bianchin M, Izquierdo I, Medina JH. Involvement of hippocampal D1/D5 receptor - cAMP signaling pathways in a late memory consolidation phase of an aversively-motivated task in rats. Proc Natl Acad Sci USA 1997a;94:7041–7046.

Bernabeu R, Levi de Stein M, Princ F, Fin C, Juknat AA, Batlle A, Izquierdo I, Medina JH. Evidence for the involvement of hippocampal CO production in the acquisition and consolidation of inhibitory avoidance learning. NeuroReport 1995;6:516–518.

Bernabeu R, Schmitz P, Faillace MP, Izquierdo I, Medina JH. Hippocampal cGMP and cAMP are differentially involved in memory processing of an inhibitory avoidance learning. NeuroReport 1996;7:585–588.

Bernabeu R, Schröder N, Quevedo J, Cammarota M, Izquierdo I, Medina JH. Further evidence for the involvement of a hippocampal cGMP/cGMP-dependent protein kinase cascade in memory consolidation. NeuroReport 1997b;8:2221–2224.

Bevilaqua LR, Bonini JS, Rossato JI, Izquierdo LA, Cammarota M, Izquierdo I. The entorhinal cortex plays a role in extinction. Neurobiol Learn Mem 2006;86:192–197.

Bevilaqua LR, Da Silva WC, Medina JH, Izquierdo I, Cammarota M. Extinction and reacquisition of a fear-motivated memory require activity of the Src family of tyrosine kinases in the CA1 region of the hippocampus. Pharmacol Biochem Behav 2005;81:139–145.

Bevilaqua LR, Kerr DS, Medina JH, Izquierdo I, Cammarota M. Inhibition of hippocampal Jun N-terminal kinase enhances short-term memory but blocks long-term memory formation and retrieval of an inhibitory avoidance task. Eur J Neurosci 2003a;17:897–902.

Bevilaqua LR, Medina JH, Cammarota M, Izquierdo I. Memory consolidation induces N-methyl-d-aspartic acid receptor and Ca(²⁺)/calmodulin-dependent protein kinase II-dependent modifications in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor properties. Neuroscience 2005;136:397–403

Bevilaqua LR, Rossato JI, Medina JH, Izquierdo I, Cammarota M. Src kinase activity is required for avoidance memory formation and recall. Behav Pharmacol 2003b;14:639–652.

Bianchin M, Da Silva RC, Schmitz PK, Medina JH, Izquierdo I. Memory of inhibitory avoidance in the rat is regulated by glutamate metabotropic receptors in the hippocampus. Behav Pharmacol 1994;5:356–359.

Bliss TV, Collingridge GL. A synaptic model of memory: Long-term potentiation in the hippocampus. Nature 1993;361:31–39.

Bonini JS, Cammarota M, Kerr DS, Bevilaqua L, Izquierdo I. Inhibition of PKC in basolateral amygdala and posterior parietal cortex impairs consolidation of inhibitory avoidance memory. Pharmacol Biochem Behav 2005;80:63–67.

Bonini JS, Rodrigues L, Kerr DS, Bevilaqua LR, Cammarota M, Izquierdo I. AMPA/ kainate and group-I metabotropic receptor antagonists infused into different brain areas impair memory formation of inhibitory avoidance in rats. Behav Pharmacol 2003;14:161–166.

Brioni JD, JL McGaugh JL, Izquierdo I. Amnesia induced by short-term treatment with ethanol: Attenuation by pre-test oxotremorine. Pharmacol Biochem Behav 1989;33:27–29.

Cahill L, Brioni JD, Izquierdo I. Retrograde memory enhancement by diazepam: Its relation to anterograde amnesia, and some clinical implications. Psychopharmacol 1986;90;554–556.

Cammarota M, Barros DM, Vianna MR, Bevilaqua LR, Coitinho AS, Szapiro G, Izquierdo LA, Medina JH, Izquierdo I. The transition from memory retrieval to extinction. An Acad Bras Cienc 2004;76:573–582.

Cammarota M, Bernabeu R, Levi de Stein M, Izquierdo I, Medina JH. Learning-specific, time-dependent increases in hippocampal Ca²⁺/calmodulin-dependent protein kinase II activity and AMPA GluR1 subunit immunoreactivity. Eur J Neurosci 1998;10:2669–2676.

Cammarota M, Bevilaqua LR, Ardenghi P, Paratcha G, Levi de Stein M, Izquierdo I, Medina JH. Learning-associated activation of nuclear MAPK, CREB and Elk-1, along with Fos production, in the rat hippocampus after a one-trial avoidance learning: Abolition by NMDA receptor blockade. Mol Brain Res 2000;76:36–46.

Cammarota M, Bevilaqua LR, Medina JH, Izquierdo I. Retrieval does not induce reconsolidation of inhibitory avoidance memory. Learn Mem 2004;11:572–578.

Cammarota M, Bevilaqua LR, Rossato JI, Lima RH, Medina JH, Izquierdo I. Parallel memory processing by the CA1 region of the dorsal hippocampus and the basolateral amygdala. Proc Natl Acad Sci USA 2008;105:10279–10284.

Cammarota M, Bevilaqua, LR, Barros DM, Vianna MR, Izquierdo LA, Medina JH, Izquierdo I. Retrieval and the extinction of memory. Cell Mol Neurobiol 2005;256:465–474.

Cammarota M, Paratcha G, Levi de Stein, M, Bernabeu, R, Izquierdo, I, Medina, JH. B50/GAP43 phosphorylation and PKC activity are increased in rat hippocampal synaptosomal membranes after an inhibitory avoidance learning, Neurochem Res 1997;22:499–505.

Cammarota, Bevilaqua LR, Kerr DS, Medina JH, Izquierdo I. Inhibition of mRNA and protein synthesis in the CA1 region of the dorsal hippocampus blocks reinstallment of a conditioned fear response. J Neurosci 2003;23:737–741.

Cammarota, Izquierdo I, Wolfman C, Levi de Stein, M, Bernabeu, R, Jerusalinsky, D, Medina, JH. Inhibitory avoidance training induces rapid and selective changes in 3[H]-AMPA receptor binding in rat hippocampal formation. Neurobiol Learning and Memory 1995;64:257–264.

Cavalheiro EA, Izquierdo I. The effect of hippocampal and neocortical spreading depression on four different behavioral tasks in rats. Physiol Behav 1977;18:1011–1016.

Chaves MLF, Izquierdo I. Previous exposure to a novel experience enhances retention performance in two simple memory tests in humans. Braz J Med Biol Res 1986;19:211–219.

Chaves MLF, Pezzin S, Jardim CP, Izquierdo I. Diazepam inhibits retroactive interference in humans; a pretreatment with naltrexone does not alter this effect. Braz J Med Biol Res 1990;23:417–421.

Clarke J, Cammarota M, Gruart A, Izquierdo I, Delgado-García JM. Plastic modifications induced by object recognition memory processing. Proc Natl Acad Sci USA 2010;107:2652–2657.

Coitinho AS, Freitas AR, Lopes MH, Hajj GNM, Roesler R, Walz R, Rossato JI, Cammarota M, Izquierdo I, Martins VR, Brentani RR. The interaction between prion protein and laminin modulates memory consolidation. Eur J Neurosci 2006;24:3255–3264.

Coitinho AS, Lopes MH, Hajj GNM, Rossato JI, Freitas AR, Castro CC, Cammarota M, Brentani RR,, Izquierdo I, Martins VR. Short term memory formation and long term memory consolidation are enhanced by cellular prion association to stress inducible protein I. Neurobiol Dis 2007;26:282–290.

Da Cunha C, Huang CH, Walz R, Dias R, Koya R, Bianchin M, Pereira ME, Medina JH, Izquierdo I. Memory facilitation by posttraining intraperitoneal, intracerebroventricular, and intraamygdala administration of Ro5–4864. Brain Res 1991;544:133–136.

Da Cunha C, Wolfman C, Levi de Stein, M, Ruschel, AC, Izquierdo, I, Medina, JH. Anxiogenic effects of the intra-amygdala injection of flumazenil, a benzodiazepine receptor antagonist. Functional Neurol 1992;7:401–405.

Da Silva WC, Bonini JS, Bevilaqua LR, Izquierdo I, Cammarota M. Histamine enhances inhibitory avoidance memory consolidation through a H2 receptor-dependent mechanism. Neurobiol Learn Mem 2006;86:100–106.

De Almeida MAMR, Izquierdo I. Memory facilitation by posttraining histamine administration. Arch Int Pharmacodyn Ther 1983;283:193–198.

De Almeida MAMR, Kapczinski F, Izquierdo I. Memory modulation by posttraining intraperitoneal, but not intra-cerebroventricular, administration of ACTH or epinephrine. Behav Neural Biol 1983:39:277–283.

Dias RD, Carrasco MA, Souza DO, Izquierdo I. Effect of naloxone, haloperidol, and propranolol on cyclic 3’5’ adenosine monophosphate content of rat amygdala. Eur J Pharmacol 1979;60:345–347.

Evangelista AM, Izquierdo I. Effects of atropine on avoidance conditioning: Interaction with nicotine and comparison with N-methylatropine. Psychopharmacol 1972;27:241–248.

Evangelista AM, Izquierdo I. The effect of pre- and post-trial amphetamine injections on avoidance responses of rats. Psychopharmacol 1971;20:42–47.

Fin C, Da Cunha C, Bromberg E, Schmitz PK, Bianchin M, Medina JH, Izquierdo I. Experiments suggesting a role for nitric oxide in the hippocampus in memory. Neurobiol Learn Mem 1994;63:,113–115.

Fin C, Schmitz PK, Da Silva RC, Bernabeu R, Medina JH, Izquierdo I. Intrahippocampal but not intra-amygdala infusion of an inhibitor of Heme-oxygenase, causes amnesia in the rat Eur J Pharmacol 1994;271:227–229.

Fulginiti S, Orsingher OA. Effects of Cannabis sativa on learning in rats. Pharmacol 1970;3:337–344.

Furini CR, Rossato JI, Bitencourt LL, Medina JH, Izquierdo I, Cammarota M. Beta-adrenergic receptors link NO/sGC/PKG signaling to BDNF expression during the consolidation of object recognition long-term memory. Hippocampus 2009;19: Epub ahead of print.

Gattoni RC, Izquierdo I. The effect of conditioning and pseudoconditioning on hippocampal and neocortical RNA. Behav Biol 1974;12:67–80.

Gozzani JL, Izquierdo I. Possible peripheral adrenergic and central dopaminergic influences in memory consolidation. Psychopharmacol 1976;69:109–112.

Gruart A, Muñoz MD, Delgado-García JM. Involvement of the CA3-CA1 synapse in the acquisition of associative learning in behaving mice. J Neurosci 2006; 26:1077–1087.

Igaz LM, Vianna MR, Medina JH, Izquierdo I. Two time periods of hippocampal RNA synthesis are required for memory consolidation of fear-motivated learning. J Neurosci 2002;22:6781–6789.

Igaz LM, Winograd M, Cammarota M, Izquierdo LA, Alonso, M, Izquierdo I, Medina JH. Early activation of extracellular kinase signaling pathway in the hippocampus is required for short-term memory formation of a fear-motivated task. Cell Mol Neurobiol 2006;26:987–1000.

Izquierdo I, Ardenghi PG, Barros DM, Bevilaqua LR, Izquierdo LA, Medina JH, Mello e Souza T, Pereira P, de Souza MM, Vianna MR. Consolidation of short- and long-term memory. In Gold PE, Greenough WT, eds. Memory Consolidation: Essays in Honor of James L. McGaugh. Washington, DC: American Psychological Association 2001;59–112.

Izquierdo I, Barros D, Mello e Souza T, de Souza MM, Izquierdo LA, Medina JH. Mechanisms for memory types differ. Nature 1998;393:635–636.

Izquierdo I, Beamish DG, Anisman H. Effect of an inhibitor of dopamine-beta-hydroxylase on the acquisition and retention of four different avoidance tasks in mice. Psychopharmacol 1979;63:173–178.

Izquierdo I, Bevilaqua LR, Lima RH, Clarke JR, Da Costa JC, Cammarota M. Extinction learning: neurological features, therapeutic applications, and effect of aging. Fut Neurol 2008;3:133–140.

Izquierdo I, Bevilaqua LR, Rossato JI, Bonini JS, Medina JH, Cammarota M. Different molecular cascades in different sites of the brain control consolidation. Trends Neurosci 2006;29:496–505.

Izquierdo I, Bevilaqua LR, Rossato JI, Lima RH, Medina JH, Cammarota M. Age-dependent and age-independent human memory persistence is enhanced by delayed posttraining methylphenidate administration. Proc Natl Acad Sci USA 2008;105:19504–19507.

Izquierdo I, Cammarota M, Medina JH, Bevilaqua LR. Pharmacological findings on the biochemical basis of memory processes: A general view. Neural Plast 2004;11:159–189.

Izquierdo I, Cammarota M. Zif and the survival of memory. Science 2004;304:829–830.

Izquierdo I, Cavalheiro EA. Three main factors in rat shuttle behavior: Pharmacology and sequential entry in operation during a two way avoidance session. Psychopharmacol 1976b;49:145–157.

Izquierdo I, Da Cunha C, Huang CH, Walz R, Wolfman C, Medina JH. Posttraining down-regulation of memory consolidation by a GABA-A mechanism in the amygdala modulated by endogenous benzodiazepines. Behav Neural Biol 1990;54:105–109.

Izquierdo I, Da Cunha C, Medina JH. Endogenous benzodiazepine receptor ligands and memory modulation. Neurosci Biobehav Rev 1990;14:419–424.

Izquierdo I, Da Cunha C, Rosat R, Jerusalinsky D, Ferreira MBC, Medina JH. Neurotransmitter receptors involved in post-training memory processing by the amygdala, medial septum and hippocampus of the rat. Behav Neural Biol 1992;58:16–26.

Izquierdo I, Dias RD. Memory as a state dependent phenomenon: Role of ACTH and epinephrine. Behav Neural Biol 1983;38:144–151.

Izquierdo I, Fin C, Schmitz PK, Da Silva RC, Jerusalinsky, Quillfeldt JA, Ferreira MBC, Medina JH, Bazan NG. Memory enhancement by intrahippocampal, intra-amygdala, or intra-entorhinal infusion of platelet-activating factor. Proc Natl Acad Sci USA 1995;92:5047–5051.

Izquierdo I, Graudenz M. Memory facilitation by naloxone is due to release of dopaminergic and beta-adrenergic systems from tonic inhibition. Psychopharmacol 1980;67:265–268.

Izquierdo I, Izquierdo JA. A note on the effect of pyrogallol on duodenal motility. J Pharm Pharmacol 1961;12:743–746.

Izquierdo I, McGaugh JH. Effect of novel experiences on retention of inhibitory avoidance behavior in mice: The effect of previous exposure to the same or to another experience. Behav Neural Biol 1987;47:109–116.

Izquierdo I, Medina JH, eds. Naturally Occurring Benzodiazepines—Structure, Distribution and Function. Chichester: Ellis Horwood, 1993.

Izquierdo I, Medina JH, Vianna MR, Izquierdo LA, Barros DM. Separate mechanisms for short- and long-term memory. Behav Brain Res 1999;103:1–11.

Izquierdo I, Medina JH. Correlation between the pharmacology of long-term potentiation and the pharmacology of memory. Neurobiol Learn Mem 1995;63: 19–32.

Izquierdo I, Medina JH. GABAA receptor modulation of memory: the role of endogenous benzodiazepines. Trends Pharmacol Sci 1991;12:260–265.

Izquierdo I, Medina JH. Memory formation: the sequence of biochemical events in the hippocampus and its connection to activity in other brain structures. Neurobiol Learn Mem 1997;68:285–316.

Izquierdo I, Merlo AB. Potentials evoked by stimulation of the medial forebrain bundle. Exp Neurol 1966;14:144–159.

Izquierdo I, Nasello AG, Marichich ES. The dependence of hippocampal function on extracellular potassium levels. Curr Mod Biol 1971;4:35–48.

Izquierdo I, Nasello AG. Effects of cannabidiol and of diphenylhidantoin on the hippocampus and on learning. Psychopharmacol 1973;31:167–175.

Izquierdo I, Nasello AG. Pharmacological evidence that hippocampal facilitation, posttetanic potentiation, and seizures may be due to a common mechanism. Exp Neurol 1970;27:399–409.

Izquierdo I, Netto CA. The role of β-endorphin in memory regulation. Ann NY Acad Sci 1985;444:162–167.

Izquierdo I, Östman R. Conditioning to cessation of a buzzer in one session. Med Exp 1961;5:433–436.

Izquierdo I, Quillfeldt JA, Zanatta MS, Quevedo J, Schaeffer E, Schmitz PK, Medina JH. Sequential involvement of hippocampus and amygdala, entorhinal cortex and parietal cortex in the formation and expression of memory for inhibitory avoidance in rats. Eur J Neurosci 1987;9:786–793.

Izquierdo I, Salzano F, Thome F, Thaddeu RC. Shuttle conditioning and pseudoconditioning in weanling and in adult rats. Behav Biol 1975;14:361–366.

Izquierdo I, Souza DO, Dias RD, Carrasco MA, Perry ML, Eisinger S, Elisabetsky E, Vendite DA. Beta-endorphin causes retrograde amnesia and is released from the rat brain by various forms of training and stimulation. Psychopharmacol 1980;70:173–177.

Izquierdo I, Vásquez BJ. Field potentials in rat hippocampus: Monosynaptic nature and heterosynaptic posttetanic potentiation. Exp Neurol 1968;21:133–146.

Izquierdo I, Wyrwicka W, Sierra G, Segundo JP. Établissement de reflexes conditionnés de trace pendant le sommeil naturel chez le chat. Actual Neurophysiol 1965;6:277–296.

Izquierdo I. β-Endorphin and forgetting. Trends Pharmacol Sci 1981;3: 455–457.

Izquierdo I. Different forms of posttraining memory processing. Behav Neural Biol 1989;51:171–202.

Izquierdo I. Effect of β-endorphin and naloxone on acquisition, memory, and retrieval of shuttle avoidance and habituation learning in rats. Psychopharmacol 1980;69:111–115.

Izquierdo I. Effect of drugs on the spike complication of hippocampal field responses. Exp Neurol 1967;19:1–10.

Izquierdo I. Effect of naloxone and morphine on various forms of memory in the rat: Possible role of endogenous opiate mechanisms in memory consolidation. Psychopharmacol 1979;66: 199–203.

Izquierdo I. Effect on pseudoconditioning of drugs with known central nervous activity. Psychopharmacol 1974b;38:259–266.

Izquierdo I. Endogenous state dependency: Memory depends on the relation between the neurohumoral and hormonal states present after training and at the time of testing. In Lynch G, McGaugh JL, Weinberger NM, eds. Neurobiology of Learning and Memory. New York: Guilford Press, 1984, 333–350.

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Edward Jones

BORN:

Upper Hutt, New Zealand

March 26, 1939

EDUCATION:

University of Otago Medical School, M.B., Ch.B. (1962)

Oxford University, D.Phil. (1968)

University of Otago Medical School, M.D. (with distinction) (1970)

APPOINTMENTS:

House surgeon, Tauranga Hospital, New Zealand (1963)

General practitioner, Auckland, New Zealand (1964)

Demonstrator and Assistant Lecturer, Department of Anatomy, University of Otago Medical School (1964–1965)

Nuffield Dominions Demonstrator, Department of Human Anatomy and St. John’s College, and Lecturer, Balliol College, Oxford University (1965–1968)

Lecturer and Associate Professor, Department of Anatomy, University of Otago Medical School (1969–1971)

Associate Professor and Professor, Department of Anatomy and Neurobiology, Washington University (1972–1984)

Professor and Chairman, Department of Anatomy and Neurobiology, University of California, Irvine (1984–1998)

Director, Neural Systems Laboratory, Frontier Research Program, RIKEN, Japan (1988–1996)

Distinguished Professor of Psychiatry and Social Sciences and Director, Center for Neuroscience, University of California, Davis (1998–2009)

Distinguished Professor Emeritus, University of California, Davis (2009–present)

HONORS AND AWARDS (SELECTED):

Symington Prize, Anatomical Society of Great Britain and Ireland and the Queen’s University, Belfast (1968)

Rolleston Prize, Oxford University (1970)

Cortical Discoverer Award, Cajal Club (1989)

M.D. (honoris causa), University of Salamanca (1997)

President, Society for Neuroscience (1998–1999)

Henry Gray Award, American Association of Anatomists (2001)

Karl Spencer Lashley Award, American Philosophical Society (2001)

Original member, Thomson Scientific/ISI Highly Cited Researchers Database (2001)

Member, National Academy of Sciences, U.S.A. (2004)

Edward Jones’s work on the structure and function of the central nervous system is distinguished by enormous breadth and scope, both intellectually and technically. He has made seminal contributions to understanding the circuitry, cellular properties, and basic organizational plans of the cerebral cortex and thalamus, their development, functional interrelationships, plasticity, and pathology. His early work laid the foundations for the understanding of cortical connectivity, and he was the first to attempt to unravel the intrinsic circuitry of the cerebral cortex using electron microscopy. His was the first modern systematic classification of cortical interneurons, and in subsequent work his studies of their chemical characteristics form a basis for all subsequent studies. His book “The Thalamus” is one of the most cited publications in neuroscience. He is also a distinguished historian of neuroscience.

Edward Jones

When I was growing up I had no idea that one day I would find myself a successful scientist, a long-term citizen of another country, and writing my autobiography. It was a series of fortuitous circumstances, the advice of three key individuals, and some pieces of remarkably good luck that took me first into medicine and then into science.

New Zealand

I was born in New Zealand. The original family members had arrived there between 1850 and 1880 during the active phase of government-assisted immigration that followed British colonization. They had their origins in Northern and Southern Ireland, in Wales, England, and German Poland. The Joneses were the Northern Irish. They had been there from the time of the Ulster Plantation of 1610, the source of all the sectarian violence that has troubled Northern Ireland ever since. All of the family members were farm laborers or workers in the woolen mills of Gloucestershire. Initially, many of them did quite well in New Zealand, especially those who became dairy farmers, producing butter and cheese for a secure market in Britain. But families that were too large and periods of depression in the agricultural industry led to a decline in the fortunes of many of them so that by the time of my birth my branch of the family, while by no means destitute, was relatively poor. Neither my father nor my mother had more than an elementary school education, and throughout most of my time at home he worked as a bartender and she as a housemaid. A failed venture into shop keeping left us penniless, without a home and living with my maternal grandmother and her three unmarried daughters in a two-bedroom government-subsidized house. And I never saw again my other grandmother, my father’s mother, who had lived with us and taught me to read and write at an early age. Between the ages of 10 and 13, until my parents got back on their feet, I was essentially a foster child, dependent for food and shelter on the kindness of a succession of uncles and aunts who had little enough themselves. My parents would eventually become managers of a series of small, brewery-owned country hotels, but that was after I had left home.

Children are resilient and I didn’t think much about the precariousness of my childhood existence but, looking back, apart from being unable sufficiently to express my debt of gratitude to those kind uncles and aunts, I cannot help but wonder at how I managed to get onto a trajectory that would take me first to medical school and then to a career in science. The New Zealand educational system, which was free, certainly helped and, despite the uncertainties of my youth, I was able to obtain an uninterrupted education throughout my high school years.

I spent my adolescent years in the provincial town of New Plymouth and during the early years of that period when I had no home to call my own, I was fortunate in having a small circle of friends with whom, after school and on weekends, I would roam the sparsely inhabited countryside surrounding the town, mostly by bicycle. We spent a good deal of time on beaches, along the banks of rivers, and rambling in the small stands of native “bush” that had escaped the deforestation of the 19th century when the province of Taranaki of which New Plymouth was the capital was transformed into the farms that today make up one of the most productive dairying areas of the world. Some of my friends were extremely knowledgeable about native plants and animals and from them I learned a lot. Perhaps it was at this time that the seeds of a later abiding interest in biology were sown. Perhaps contributing also was the time that I spent on an uncle’s farm, where I learned to milk cows and manage the horses that were still being used at hay-making time.

I obtained my high school education at a good school, the New Plymouth Boys’ High School, an all-male institution as the name indicates. Although dominated by rugby football, as all New Zealand boys’ schools were, it had a solid academic reputation as well. I played my share of rugby (we were all made to) but I was drawn early to the academic side. Seemingly paradoxically, I excelled in English and Latin on the one hand and in geography and biology on the other. But in those days the latter two subjects were disciplines requiring a degree of skill at writing descriptions of maps and biological organisms or communities, and I discovered that I had a flair for descriptive writing that I hope I have retained to this day. As to the paradox, I could never really see the difference between putting into words what I was visualizing on a map or in a tide pool and writing a critique of a passage in Paradise Lost or The Divine Comedy. The term “descriptive” has negative overtones in today’s science, but all science is descriptive. No one could argue that the Human Genome Project was anything but that. Where the word is used in a negative sense today, it is really being used as a synonym for “unfashionable.”

I was never very good at math or physics and, although over the years I have taught myself statistics and have in fact done a lot of quantitative work, I remain mathematically weak. One of my early Ph.D. students, Steve Wise, on graduating presented me with a little book entitled How to Teach Yourself Arithmetic. (His other gift was a bull whip.) As a believer in the developmental plasticity of the brain, I am convinced that in brain development the early expression of verbal and written skills, such as I had exhibited under the tutelage of my grandmother, gives them dominance over that intuitive mathematical skill that the human brain normally develops and to which teachers of mathematics direct their teaching. In a math examination, I always seemed to spend my time trying to decipher the written sense of a question rather than jumping intuitively, as my school fellows did, to the requisite formula for working it out.

The decision to go to University came late, toward the end of my last year in high school. It was a decision of some moment. No member of my family had ever attended University and my mother, as a child of the working class, was against it on the grounds that I would be taking myself out of that class. Expense was not an issue, for one of the remarkable things about New Zealand in those days and continuing even today is that University education was essentially free. Passing an entrance examination assured that the fees were paid and spending a fifth year in high school gave one a modest living allowance as well. A strong desire to continue learning, coupled with a certain competitive instinct, aroused by the realization that many of my classmates whose abilities were less than my own were going on to University, persuaded me that this was the right thing for me to do as well. The decision to try for entry into Medical School was in part also determined by that competitive instinct, for Medicine was reputedly then the hardest University course. Yet I was still drawn to English literature and the classics. It was around this time that I had discovered the “Penguin Classics,” the paperback collection of translations of classical Greek and Latin as well as French, German, and other literature. In reading these works, I was strongly attracted to the idea of studying the humanities. It was a respected teacher of English at the high school who, knowing of my penchant for both literature and biology, persuaded me to go to Medical School, pointing out that a degree in English or the Classics limited one’s opportunities to just these disciplines, whereas a degree in Medicine permitted one to pursue just about anything that one chose. For me, that turned out to be excellent advice and to that teacher I owe a great deal.

There was only one Medical School in New Zealand in those days: at the University of Otago in Dunedin, located in the southern part of the South Island. To gain entry, one had to spend 1 year studying Zoology, Physics, Chemistry, and Organic Chemistry at any one of the four New Zealand Universities and at the end of that year sit a competitive examination in which the top scorers qualified for one of the 100 places in the first-year medical class. There were in fact 120 places but 20 were reserved for the 20 students who invariably failed the first-year course and were given one chance to continue their studies. I was fortunate to gain one of the coveted places. One of the consequences of entry into Medical School after only 1 year in University was that most of us were quite young. I and two other members of the entering class had not yet turned 19.

The Otago Medical School was a very traditional one with the whole of the first year and two of the three terms of the second year devoted to Anatomy, Physiology, and Biochemistry with an examination—written, practical, and oral—covering all of the material at the end. It was very demanding in the amount of learning required, and I doubt that any modern medical student would handle it without complaint. Most of us did handle it, but it was still possible to fail and be dismissed from the School. The Anatomists, led by Bill Adams, were exceptionally good teachers, although in 1958 they had not yet heard of the structure of DNA, revealed some 5 years previously. Biochemistry was still at the level of the Krebs cycle, to the elucidation of which the Professor, Norman Edson, had made significant contributions in his younger days. He opened his lecture on bile with the words: “Omnes Gallia in tres partes divisa est,” at which fully 50% of the class laughed. Enough of us had previously had sufficient Latin to recognize the opening lines of Caesar’s Gallic War. A modern medical class would undoubtedly ask if it were to be on the exam. There was some excellent neurophysiological research going on in the Department of Physiology under the leadership of Archie McIntyre. Archie had succeeded John Eccles in the chair which Eccles had held from 1944 to 1951 when he left to take up his position as founding Professor of Physiology at the new John Curtin School of Medical Research at Canberra in Australia. The first intracellular recordings from spinal neurons, the work for which Eccles in 1963 was awarded the Nobel Prize, were obtained in Dunedin. Eccles was remembered more for his irascibility than for his scientific achievements. Many years later, at a meeting in the Vatican, in introducing me to an audience, he described himself and me as being the only two neuroscientists who had been to Purgatory and back because we had both been on the faculty of the University of Otago. It was an unkind remark, but it reflected the difficulty that we both had had in setting up and maintaining a productive laboratory in one of the remotest medical schools in the world.

Early on I developed an affinity for Anatomy, not because of any abiding scientific interest but because of the discipline required in writing a clear and accurate description, using a standard terminology, of what I was seeing in the dissections in gross anatomy or under the microscope in histology. Putting visual observations into words, which has always been one of my strong points, was a skill honed in those early years. Coupled with it was a capacity for the visual representation of data, which stemmed from the drawings of cells and tissues observed under the microscope. Whenever I come across them today, I never fail to be amazed by the quality of those early drawings, made without the benefit of a camera lucida. Writing objectively and drawing accurately are not skills that are very much in vogue in science today, where the favored vehicles of scientific publication encourage superficiality, a gushing approach, and a liberal use of the Royal plural, and where the visual representation of data is usually confined to a couple of postage stamp-sized micrographs made mostly from laser confocal images that even if they could be seen are tokens, largely devoid of content.

After entering the clinical years of the medical course, of which there were three, I continued to teach anatomy to the first-year students, giving something like 50 tutorials a year to half the class. It seems a lot now but it did not seem unduly arduous at the time and it gave me experience in making oral presentations long before most of my colleagues. Again, the discipline of giving accurate verbal descriptions of the bones and other body parts was a challenge that I enjoyed meeting. For me, the clinical years were less interesting than the preclinical, I think, in large part because there were far too many students for the limited number of patients, Dunedin being quite a small city. There wasn’t enough hands-on experience for my liking, and I found it irksome to have to thrust myself into a position in which I could examine someone with an interesting condition. Pharmacology and Pathology, which might have been expected to hold some interest for one with a strong predilection for basic science, never attracted me. The first was still in a very primitive state in which every neurotropic drug was held to exert its effect by operating on “the reticular formation,” a nebulous part of the brain which I could never find described in morphological terms, and the second still in some kind of Victorian dark age.

During my years in medical school, my modest government bursary was insufficient to cover all my living expenses, so I was obliged to work in the vacations in order to supplement it. I was not alone in this. Many of my classmates were in the same position, and the majority of us worked at manual laboring jobs that offered temporary employment. Over the years, I worked collecting and stacking hay bales, on construction sites, and for three periods underground in a coal mine. I also served time as a bartender in the rough little village in which the mine was located. It was during these vacation jobs that I developed a lasting bond with working men and women that has always served me well in interactions with workers and trades people. I also acquired skills that have been useful in home remodeling projects.

I never regretted having to work so hard to pay my way through Medical School, although there were times when I would have loved to have spent a protracted period of time reading and writing or, even better, to have worked in a lab. Perhaps surprisingly, if I had worked in a lab it would not have been in Anatomy but in Physiology where, as I mentioned earlier, the Department in Dunedin had a strong tradition of neurophysiology and an active research program through which a significant number of medical students passed, some taking a bachelor’s degree before returning to Medical School and some not returning at all but going on instead to a scientific Ph.D. Perhaps it was at that time that I began to become dimly aware that the forefront of medical science was no longer in Anatomy but in more experimental disciplines. As I write that, I realize that, unconsciously, I was already headed for an academic rather than a practicing medical career.

I was still reading widely, far outside the field of medicine, and especially in the classics. In one of my final examinations I can recall writing the answer to a question on syphilis from the perspective of Voltaire and his character, Dr. Pangloss, who in Candide lost his nose to the disease. I don’t know what the examiner made of that, but I did not fail. Although penicillin had been introduced some 15 years earlier, syphilis was still with us then, mostly in its tertiary form. One of my patients in my final examination was a tabetic and, when confronted with a case of dementia, we were inclined to think first of general paresis of the insane, then of senile dementia and virtually never of Alzheimer’s disease, which was considered to be exceedingly rare. It was through my continuing fascination with the 15th-century French writer François Rabelais that I met the second person who was to be influential in helping me shape my future career. I had first encountered Rabelais as a schoolboy in J. M. Cohen’s Penguin Classics translation and had discovered in his irreverent and amusingly scatological writing not only the very essence of humanist ideals but also a mine of Renaissance medical information that probably formed the foundation of my later studies in medical and especially neuroscience history. It was through Rabelais that I met Erich Geiringer whose knowledge of the old French work was far greater than my own and who had a broad perspective on the history and culture of medicine that I and many of my classmates found fascinating. We had never met with such erudition or the cosmopolitan worldview that accompanied it. It was not to be found among our teachers in provincial Dunedin.

Geiringer had fled Vienna at the time of the Anschluss and completed his medical training at Edinburgh. He had come to Dunedin as a research fellow in the Department of Medicine. His experience of Nazi persecution in Austria had given him a determination to confront any form of authoritarianism, and this was always nascent in the provincial medical environment such as existed in Dunedin. The consequence was that he was always in trouble with the administration of the Medical School. When reprimanded by the Dean for visiting patients in the wards without wearing a white coat, his response—that Napoleon’s physician, Jean-Nicolas Corvisart, had once been barred from La Charité for failing to wear a frock coat—was probably met with bewildered incomprehension. Not surprisingly, Geiringer soon left the Medical School to enter private practice and for the rest of his life he remained a prominent critic of New Zealand cultural attitudes and a thorn in the side of the New Zealand medical profession. Geiringer, like that high school English teacher before him, gave me the confidence to believe that a career in medicine was by no means incompatible with a satisfying intellectual life. We remained close friends until his death in 1995 and I cherish his memory.

We all spent the final vacation between the fourth and the final year in Medical School as clinical assistants at hospitals around New Zealand, and it was in these hospitals that most of us obtained our first in-depth clinical experience, often with a considerable degree of responsibility. Then we moved into the final year, which was spent at one of the four teaching hospitals at Dunedin, Christchurch, Wellington, and Auckland. There, we gained a good deal more clinical experience in preparation for returning to Dunedin for the final examination and for the award of the degree of Bachelor of Medicine and Bachelor of Surgery (M.B., Ch.B.). Toward the end of my last year in Medical School, I had more or less made up my mind that I wanted to make a career in academic medicine and probably in basic science. With only one medical school in the whole country, there was obviously no clear route to this and so I felt it expedient to acquire the qualifications that would enable me to practice medicine in the event that my ambition was unrealizable. Knowing that, I determined to get as much clinical exposure as possible in the shortest time and took up a house surgeon’s (intern’s) position at a relatively small but extremely busy provincial hospital. There were only three of us on the house staff, and we had what was probably too much individual responsibility. Every third weekend from Friday evening until Monday morning, one of us was in charge of the entire hospital. There were senior staff that we could call on, of course, but we were expected to do as much as possible ourselves from the emergency room to the operating room and the inpatient wards. I didn’t make too many mistakes, but those that I did make remain with me to this day. Most of the minor surgery devolved on us junior staff and in repairing wounds, and removing, probably unnecessarily, numerous appendices and tonsils, I gained skills that have served me well throughout my career. It was this that told me that if a slot was not available for me in basic academic medicine, I could probably make a satisfactory career for myself as a surgeon.

It was while at that provincial hospital that I had my first opportunity to write a research paper and to see it published. One day I had admitted a 17-year-old Maori man suffering from inoperable cancer of the stomach, and when I walked to the other end of the hospital I discovered in another ward his 21-year-old cousin who had been admitted with the same terminal condition. Initial enquiries revealed that one of their sisters in her 20s had in the recent past died of the same disease, and after further enquiries it became clear that the local Maori community and some of the older doctors in the region knew that many other members of the family had been afflicted with this terrible, early-onset disease for more than a century. The older members of the family, if they could be persuaded to discuss it, which they often weren’t, thought that they were afflicted with a curse while the younger, better educated members were more inclined to blame a European, a Scot, who had married into the family in the 1830s. I was able to identify as many as a dozen cases of this early-onset cancer in the wider family and realized that this was a family at genetic risk for the disease. I wrote it up for publication in the New Zealand Medical Journal under the title of “Familial Gastric Cancer.” There it lay, I thought forgotten, until many years later, in 1998, I was reminded of it when one of my postdoctoral fellows came into my office waving a copy of Nature and congratulating me on my status as a gastroenterologist. In that issue of Nature, Drs. Parry Guilford and Anthony Reeve of the University of Otago and their team of doctors and family members reported that they had identified the mutant gene that was the cause of this cancer. The authors very generously acknowledged my having brought it to light. By that time as many as 25 other members of the family, all at a young age, had been diagnosed with the disease and some had even had elective gastrectomies in an effort to avoid it. Despite my postdoc’s irreverent remarks, I can take comfort in the fact that the mutated gene encodes for a cadherin and is thus a member of a gene family that is also expressed in the nervous system.

Apart from the cancer family, the other high point of my hospital year was my marriage to Sue, who has been with me ever since. She is a remarkably patient person who has always been willing to follow me along whatever new path I took and to make the best of whatever circumstances we found ourselves in at its end.

After leaving the hospital and spending a short time as locum tenens of a solo general practice, I was able to return to the University of Otago Medical School but, as there was no academic position in sight, I entered a program in which prospective surgeons spent a year as “demonstrators” in the Anatomy Department while preparing for the primary examination of the Royal Australasian College of Surgeons. For most of them, passing the examination and further clinical work gave them a Fellowship of the College and a stepping stone to a job in the United Kingdom, where they would sit the examinations for the Fellowship of the Royal Colleges of Surgeons at London or Edinburgh. Having one of these fellowships was a key requisite if one wanted to practice as a surgeon in New Zealand or Australia. It seemed to me that by starting out in the Anatomy Department I would be able to follow this same route if an academic position could not be realized.

I never did take that primary examination. As the year wore on, I found myself not only teaching the medical students their anatomy and histology but also more and more in helping the aspiring surgeons prepare for an examination which, for the amount of detail that it required, could be positively terrifying. In my second year, when I had been given a temporary assistant lectureship in Anatomy, I began to do some research. During my first year I had in fact written a short paper on a set of muscular anomalies found in one of the cadavers, interpreting them in developmental terms. It was a paper that might have graced any 19th-century anatomy journal, but it gave me an opportunity to exercise my talents for description and it did find a place in a respectable, if old fashioned, journal. More important, it led me to read about muscle and its innervation and to the muscle spindle, the low-threshold stretch receptor of striated muscle, whose pattern of sensory and motor innervation was then being revealed anatomically, not without a modicum of controversy, in the laboratories of David Barker at Durham and Ian Boyd at Edinburgh. The physiology of the primary sensory endings had long been known from the work of Sherrington and that of the motor innervation by the work of Hunt and Kuffler at the Rockefeller University and later by that of Peter Matthews at Oxford, but the manner in which the two physiologically distinct classes of fusimotor fibers ended on the little nuclear bag and nuclear chain muscle fibers of the spindle was still a source of argument.

I commenced my muscle spindle work on the lumbrical muscles of the forepaw. Then and still now I could not believe that these tiny muscles, stretched from the tendons of the long flexors of the fingers to those of the extensors could have much to do with generating even fine movements of the fingers. They had to be a form of stretch receptor and that seemed confirmed by their having one of the densest concentrations of muscle spindles of all the muscles in the body. The species I used was the brush-tailed possum (Trichosurus vulpecula), chosen for its ready and free availability. It was a pest that had been introduced from Australia, and trappers from whom I obtained specimens were paid to help eradicate it. They never did. It is still a major pest that continues to eat its way through the forests. With little or no advice, I began staining the muscles with methylene blue and teasing out whole spindles with their innervating nerve fibers, using hedgehog quills mounted on sticks, the sharpest points that I could find. (The European hedgehog was another introduced species that had become a pest in New Zealand). In retrospect, I realize that I was doing something that few others were doing at that time, although the isolated muscle spindle was later to become a standard preparation in physiology. Using the methylene blue stain had its moments: in order for the stain to be effective in staining neural elements it must be applied in an oxygen-rich environment. Exposing the tissue to air while applying the stain was the traditional way of doing this, but I sought to do better by bubbling an oxygen/carbon dioxide mixture through the staining solution while perfusing it through the aorta. You can imagine what happened when the flask containing the perfusate and suspended above the laboratory bench burst under the applied pressure of the gas. If it got on your skin, you realized why it was called a “vital stain.” It could not be removed until the keratinocytes that had been stained by it were turned over. And a white shirt was ruined.

I generated some very pretty preparations of muscle spindles and was able to prepare two papers from the work that were published in the Journal of Anatomy and in The Anatomical Record. In one of them I was convinced that the bag and chain intrafusal fibers could indeed be innervated by the same fusimotor fiber, in agreement with Barker but at variance with Boyd. What I realized later was that in order to put this study on a more solid footing, I should have been directly demonstrating the sensory or motor character of the numerous nerve fibers innervating the spindle by selectively cutting the dorsal or ventral roots of the spinal nerves from which they arose. There was rarely any doubt about identifying the annulo-spiral endings of the Group IA primary afferent fiber, but the distinction between the terminals of the thinner Group II fibers and those of the fusimotor fibers was not always clear in normal preparations. Eventually, I suspect, I would have come around to doing rhizotomies and the surgery involved would not have presented any difficulties for me. But in the absence of advice, it did not happen and something intervened to cut short my muscle spindle days.

Oxford

Halfway through that second year, a piece of exceptional good luck came my way, a piece of good fortune that I still marvel at. I was offered the opportunity to take up a fellowship at Oxford University. The fellowship was called a Nuffield Dominions Demonstratorship and had been endowed by William Morris, Lord Nuffield, one of the founders of the British automobile industry. It was offered to young medical graduates from the old colonies of Australia, New Zealand, and South Africa—not to those from Canada because Canadians didn’t buy British cars. It gave appointees the opportunity to spend up to 3 years working in an Oxford clinical or basic science department and came with a generous stipend and travel allowance. Initially, I was somewhat overawed by my good fortune and wondered if I would be capable of performing up to the standards of one of the greatest Universities in the world, but I was encouraged by others who had been previous holders of the award, and it was from those who had spent their years in the Department of Human Anatomy at Oxford that I was directed to that department and to working with the third person who played a profound role in helping me shape my future career: Dr Thomas P. S. Powell.

Tom Powell, informed of my wish to work with him, wrote accepting me into his laboratory and telling me that he would have me work on the connections of the somatosensory cortex. I wrote back thanking him but admitting that I knew little about the somatosensory cortex or its connections and asking for advice as to what I should read in advance. Back came the reply, 2 weeks later and on one of those flimsy blue “aerograms” that were the chief means of international correspondence, there being no Internet in those days and international telephone calls prohibitively expensive, at least from New Zealand. It said: “Read nothing until we see the results of the first experiment.” It was appropriate advice because virtually nothing had been written up to that time on the connectivity of any part of the cerebral cortex. The little work that had found its way into the literature had been carried out with the old Marchi technique that had long been out of favor mainly for its inability to stain finely myelinated and unmyelinated fibers, or with strychnine neuronography in which every part of the cortex seemed connected to every other part.

The lack of connectivity data did not mean that the cerebral cortex was otherwise neglected. By this time the primary motor and sensory areas of many mammals, including those of the human, had been mapped by the stimulation or evoked potential techniques in animals, primarily by Clinton Woolsey and his students. Vernon Mountcastle, in using the single-unit technique, had discovered the cortical column in the cat’s somatosensory cortex and he and Tom Powell (the two had worked together during Powell’s sabbatical in 1958) had extended this work to the somatosensory cortex of the macaque monkey, relating the selective responses of neurons to deep or cutaneous stimuli to their locations in different cytoarchitectonic areas of the postcentral gyrus. David Hubel and Torsten Wiesel had commenced their ground-breaking work on the cat’s visual cortex, some of the subcortical connections of which were beginning to be mapped anatomically by the Nauta technique. But there was clearly a need for systematic, in-depth studies of the connectivity of individual, functionally defined areas of the cortex.

I didn’t entirely follow Tom Powell’s advice. I attempted to read the papers that were then emerging from his laboratory on the connections of the hippocampus, but I have to confess that I found them virtually incomprehensible. I had simply not studied central nervous system (CNS) anatomy at that level of resolution before. But I made a note of the writing style and saw how I could emulate it. If Tom recognized that the draft of our first paper was written in imitation of his style, he did not admit it.

Arriving with Sue in England in late December of 1965, both she and I were struck, as probably many visitors from the old colonies were, that what we had absorbed in our British-oriented education but never experienced now acquired relevance. There were the long rows of terrace houses that we had never seen, the babies taking the air on even the coldest afternoons by being placed in their prams in “the area,” the shilling in the gas meter that was the sole means of keeping warm, the first squirrel scampering across the snow-covered ground as we enjoyed our first English breakfast. (Unlike virtually all other northern hemisphere vermin, the squirrel had never been successfully introduced into New Zealand). The buildings of Oxford were just being cleaned of their centuries of accumulated grime, and the beautifully warm Cotswold stone of the Colleges was emerging to be seen at its best.

The day after our arrival in Oxford, I visited the Department of Human Anatomy and met Tom Powell and his colleague of more than a dozen years, Max Cowan. Both were to have a significant influence over my future career. Tom had trained as a neurosurgeon before joining Sir Wilfrid Le Gros Clark, the head of the Department of Human Anatomy in 1951. Max had come from South Africa in the middle of his medical student years to complete his degree at Oxford and to work also in Le Gros Clark’s department. Le Gros had retired by the time I arrived in Oxford, being replaced by another distinguished British scientist, Geoffrey Harris, so I can only claim indirect descent from one of the most famous of all neuroanatomists. Working together from 1953, Tom and Max had initially used the retrograde degeneration technique and normal silver staining to work out the connections of the hippocampus and striatum—to the extent that these could be unraveled with what, in comparison to later techniques, were low-resolution techniques. In the years prior to my arrival in Oxford, the two had turned to the recently introduced Nauta technique, a method for visualizing neural connectivity by the selective silver staining of axons and their terminal ramifications undergoing Wallerian degeneration as the result of surgical destruction of their cells of origin. The great advantages of this technique were not only that it stained degenerating axoplasm and thus both myelinated and unmyelinated fibers but also that it did so against a clear background from which the staining of all other, normal axons was suppressed. It was from use of this technique that those papers on the hippocampus that I had found incomprehensible came. Max had recently returned from a sabbatical year in the Department of Anatomy at Washington University, where he had learned electron microscopy, and during the same period Tom had introduced the method at Oxford, after conferring with George Gray and others at University College London.

It was a good time to be commencing a career in what was to become neuroscience. Thanks to improvements in the Nauta technique, it was now possible to use it in what may be regarded as a high throughput manner to investigate circuitry in the CNS. And the introduction by Karnovsky in 1965 of the mixed formaldehyde/glutaraldehyde fixative for electron microscopy now made it possible to perfuse an animal and obtain well-fixed tissue from any part of the brain or spinal cord. Prior to that, adequate preservation of ultrastructure could only be obtained by dicing the tissue into tiny pieces and immersing them in osmium tetroxide or, for the cerebral and cerebellar cortices, dripping osmium tetroxide onto their surfaces. Perfusion with the mixed aldehydes temporarily stabilized cell membranes and intracellular organelles so that a desired brain region could be accurately removed and later be postfixed by osmium tetroxide, thus preserving lipids and other macromolecules permanently. Although there were attempts to perfuse with osmium, these rarely worked and it was decidedly hazardous as well.

At my first meeting with Tom and Max, Tom told me: “You can join any College that you like—mine is St. John’s.” It was clear what my choice should be, so I went to meet the Senior Tutor at St. John’s, walked with him to the Sheldonian Theatre where he exchanged a few Latin phrases with the Vice Chancellor and I became an advanced student and a candidate for the D.Phil. As an advanced student, I was entitled to wear a gown somewhat longer than that worn by the undergraduates and when, after Max’s return permanently to the United States, I inherited his Lectureship at Balliol College, I was entitled to wear an even longer one and to enjoy dining rights.

Even though all of us, Tom especially, taught extensively, the Powell lab was a hive of experimental activity. Beginning with me were Joel Price, a Rhodes Scholar who had just completed his undergraduate degree; Janet Kemp, who had just returned from a period in Walle Nauta’s laboratory at MIT; and Geoffrey Raisman, who had just returned to the lab after completing his medical degree. It was the custom in Oxford to take time off to do the D.Phil degree in the 2 years between the basic and clinical years of the medical curriculum and Geoff had had a very productive time during that period when he did all that work on the hippocampus that had so perplexed me. Over the years, many other students passed through Tom Powell’s lab in this way, all of them producing high-quality work. Some went on to become successful neuroanatomists in British and foreign Universities, but the majority of the graduates of his lab became leaders of British medicine in fields as diverse as pathology, ophthalmology, infectious disease, and military medicine.

Joel Price began working on the connectivity of the olfactory bulb in the rat, Janet Kemp on the corticostriatal projection, and I on the connections of the somatosensory cortex, first in the cat and later in the monkey, all of us using a combination of the Nauta technique and electron microscopy. Geoff Raisman commenced working on the electron microscopy of fornical and other inputs to the septum and after he had succeeded to Max’s University Lectureship and Fellowship of Pembroke College, and left to form his own independent lab, this turned into one of the first studies of synaptic plasticity in the brain.

The Nauta work and the electron microscopy proceeded in parallel. The first involved the placement of lesions in the cerebral cortex or thalamus to cause the degeneration of the efferent and afferent axons of the cortex that could then be selectively stained. The second was a combination of both normal morphology and degeneration-based identification of the terminals of the pathways revealed with the Nauta technique. I was soon making most of the surgical lesions and for the Nauta studies I also usually cut the sections, stained and mounted them. For the electron microscopic studies, Tom’s long-standing technician, Ron Brooke, cranked out long runs of thin sections on a regular basis for all of us. This was an exciting time for the electron microscopy of the CNS. As mentioned earlier, the introduction of fixation by perfusion with mixed aldehydes greatly facilitated access to well-fixed tissue from any part of the brain, and new features of neural ultrastructure were emerging on a regular basis. The synapse had, of course, been recognized at the electron microscope level much earlier and, in fragments of cortex fixed directly in osmium tetroxide, George Gray had been able to demonstrate the ultrastructure of the dendritic spine in the cerebral cortex and the presence of two kinds of synapse in which the pre- and post- synaptic membranes were thickened asymmetrically or symmetrically. He called them Type I and Type II, respectively. The duality was not something that all electron microscopists of the nervous system were then prepared to accept, thinking the two forms of synapse to be no more than the two ends of a continuum. However, it has stood the test of time and represents one of the most fundamental features of CNS organization. Every session on the electron microscope seemed to yield a new set of images that required identification, and I can recall always bringing to those morning coffees and afternoon teas, which were a regular feature of the Powell lab, a file of unusual electron micrographs for discussion and argument. There were often surprises such as the appearance of a cilium on a cortical neuron, but others were much more relevant and formed part of the mounting knowledge base of CNS fine structure: confirmation of Gray’s two synaptic types; pedunculated and sessile dendritic spines, invariably with one asymmetrical synapse and occasionally a symmetrical one on each; the identification of pyramidal and nonpyramidal cell somata by their different complements of synapses, those on the former being all symmetrical and those on the latter a mixture of both types; the peculiar membrane undercoat that allowed the initial segment of the axon to be identified; the recognition of the presence of synapses on the initial segment, which at first was hard to believe; in the thalamus, structures that looked like dendrites but which contained synaptic vesicles and made synaptic contacts. Perhaps most dramatic of all was the growing recognition, stemming from Uchizono’s work on the cerebellar cortex, that in aldehyde-fixed material, the synaptic vesicles of boutons making asymmetrical synaptic contacts remained spherical while those contained in terminals making symmetrical synapses flattened and became ovoid. Because Uchizono had made his observations in a structure in which he could identify that the asymmetrical/round vesicle synapses were made by excitatory neurons and that the symmetrical/flattened vesicle synapses were made by inhibitory neurons, the implication was that in the cerebral cortex, too, excitatory and inhibitory synapses might be identifiable by the same morphological features. Acceptance of this as another fundamental principle of neural ultrastructure also came slowly and it was not until Marc Colonnier, in a paper containing a fold-out plate with 100 synapses illustrated side by side, demonstrated the clear bimodality of structure, that it became recognized.

We were not alone in making the observations on normal tissue. There were several other laboratories, notably those of Alan Peters and Sanford Palay, simultaneously publishing similar findings. What we spearheaded was the application of degeneration techniques positively to identify the origins of the synapses that we were observing in the cortex and thalamus. Marc Colonnier while working at University College London had shown that, if the cortex was undercut and the animal left to survive for a few days, synaptic terminals in the overlying cortex whose axons had been cut underwent a distinct reaction characterized by increased electron density, shrinkage, and astrocytic engulfment. Colonnier and Guillery in London and Szentágothai and his students in Budapest had also shown that the terminals of the optic tract in the lateral geniculate nucleus, degenerating as the result of tractotomy could also be identified by electron microscopy, although here the appearance was one of remarkable neurofilamentous hyperplasia. The two forms of terminal degeneration initially caused some confusion until it gradually became clear that it was mainly the large terminals of thick axons in subcortical structures that underwent the initial neurofilamentous reaction before passing to the electron-dense phase that terminals of thinner axons such as those in the cortex directly underwent.

For Tom Powell and me, the ability to recognize degenerating synapses at the electron microscopic level gave us the opportunity to make lesions in the sources of the axonal pathways that we were identifying light microscopically with the Nauta technique, and to determine the nature of their terminations in the cortex or thalamus of the cat. After my departure from Oxford, Tom and his students were to extend this work to the cortex of the monkey with highly productive results. From our electron microscopic studies on the somatosensory cortex, there emerged a lengthy series of papers that took up a whole issue of the Philosophical Transactions of the Royal Society. The terminations of ipsilateral corticocortical and commissural fibers and of thalamocortical fibers were identified, and I think it came as a surprise to many that most of these terminations, especially those of the thalamocortical fibers, were on dendritic spines of pyramidal cells. At the time the view of cortical connectivity was a remarkably simplistic one, namely that afferent fibers ended on some nebulous form of “stellate” or “granule” cell that transferred the input to the pyramidal cells, the output cells of the cortex. Anyone reading Cajal would have recognized that the afferent inputs were to a large extent focused on pyramidal cells and that the collaterals of pyramidal cell axons formed a set of intracortical connections that was far denser than those formed by the ascending axons of layer IV stellate cells. Unfortunately, nobody was reading Cajal at that time. It was inevitable that we should extend our studies to the terminations of corticothalamic fibers in the thalamus, and out of them emerged the first evidence for the extremely large number of synapses formed by these thin fibers and the concentration of their terminals on the second- and third- order dendrites of the thalamocortical relay cells. In comparing the fine structure of the ventral posterior nucleus of the thalamus with that of the medial and lateral geniculate nuclei, we found that they were organized along similar lines, in the cat dominated by the peculiar, glial-ensheathed glomeruli in which the large terminal of a subcortical afferent fiber, making contact with the proximal dendrite of a relay cell, lies surrounded by terminals that would later prove to be the presynaptic dendrites of inhibitory interneurons.

The electron microscopic studies were obviously informed by the studies going on in parallel at the light microscopic level with the Nauta technique.

When we commenced these studies, the corticocortical and commissural connections of the cerebral cortex were virtually virgin territory. Some work had been done on the subcortical projections of the motor and visual cortex, including in the case of the latter, by Laurence Garey who had recently left Tom Powell’s lab to complete his clinical work and who would eventually return, but there was virtually nothing on other areas and no work with the Nauta technique had been done at all on the thalamocortical projection. As our work advanced, it became clear that we were not alone in recognizing the deficiency of knowledge about the corticocortical and commissural connections of the cortex. Adrian Morrison and Hans Kuypers with Deepak Pandya were soon found to be doing similar work, the first on the cat and the second two on the monkey.

Out of my 3 years of work with the Nauta technique on the somatosensory cortex of the cat and monkey, there emerged a number of principles that have stood the test of time and work with higher resolution techniques. They are now so well established that they may seem commonplace, but at the time they were new. Homotopic and heterotopic connections across the corpus callosum was one of the first when it was recognized that the primary somatosensory cortex of one side not only projected to its homolog on the contralateral side but also to the contralateral second somatosensory area. Specificity of ipsilateral corticocortical connections was another: the primary somatosensory area did not project widely but very specifically to the second somatosensory area, to the primary motor cortex and to anterior parietal cortex (area 5). There was also topographic specificity in the sense that different parts of the body representation in the primary somatosensory area only projected to corresponding parts of the motor or second somatosensory representations, and a similar topography observed in area 5 implied that it too would have a representation of the body surface that matched that in the primary area. When we turned to making tiny, needlepoint lesions in the postcentral gyrus of monkeys, we were also able to show that a small part of the body representation did not project locally much beyond its own representation, and we were able to show differences in the connections of areas 3, 1, and 2 that made up the primary somatosensory area as defined by evoked potential and single-unit mapping. We observed a similar topographic specificity in the corticothalamic projection, not only in that it projected back only to the thalamic nucleus from which the cortical area received input, in the case of the somatosensory area, the ventral posterior nucleus, but also that the body topography seen in the intracortical connections was also preserved in this connection as well.

As the last step in the sequence of studies on the connectivity of the somatosensory cortex, we made stereotaxically localized lesions in the ventral posterior nucleus of cats and monkeys and traced the degenerating thalamocortical fibers to their target. Here, the same kind of organization based on body topography was also revealed. But it was also evident that the projection to areas 1 and 2 in the monkey was substantially less dense and made up of finer fibers than that to area 3. On the basis of past work with the retrograde degeneration technique, this might have been interpreted as implying that the projection to areas 1 and 2 would be made up of branches of fibers projecting to area 3. In the language of Rose and Woolsey, derived from their observations of the differences in the severity of retrograde degeneration ensuing from cortical lesions, the projection to area 3 would be an essential projection and that to areas 1 and 2 a sustaining projection. I was never comfortable with this interpretation since it seemed to fly in the face of Mountcastle and Powell’s evidence for the modality specificity of inputs to areas 3, 1, and 2. It was only many years later that I was able to confirm that separate thalamic cells projected to the cytoarchitectonic areas of the postcentral gyrus, including to the subdivisions of area 3, areas 3a and 3b, which had in the meantime been revealed as the recipients of low-threshold muscle spindle and cutaneous inputs, respectively.

At this time, the generality of corticothalamic projections was only just becoming apparent. Long before, some had even doubted their existence or thought them confined to certain thalamic nuclei only, but with our work and that of others in the field it soon became evident that all areas of the cortex projected back to the thalamus. What remained unclear was whether a given cortical area projected back only to the thalamic nucleus from which it received its afferent input. As the work on the somatosensory cortex progressed, we were able to analyze in parallel the brains with lesions of the visual and auditory cortical areas of the cat, the first prepared by Laurence Garey and the second by Irving Diamond who had spent a brief sabbatical in the Powell laboratory in the months preceding my arrival in Oxford. The results of this analysis served to confirm many of the principles that were emerging from the work on the somatosensory area and out of it came a paper on “Interrelations of Striate and Extrastriate Cortex with the Primary Relay Sites of the Visual Pathways,” which became a so-called citation classic, and in the papers from the auditory cortex there came a “principle of reciprocity” of corticothalamic and thalamocortical connectivity. This principle stressed that the projection from a small patch of cortex terminated only in the part of the thalamic relay nucleus that contained the cells projecting to that patch. The principle stood for many years and served as a means of deducing thalamocortical connectivity when direct observation of thalamocortical fibers was not feasible. Only with the emergence in the 1990s of higher resolution techniques for tracing individual corticothalamic fibers to their terminations in the thalamus did it become evident that the extent of the corticothalamic projection from a column of cortex could exceed that of the set of thalamic cells providing input to that column.

In using the degeneration-based Nauta technique, we and others were always aware of what was called the “fiber of passage problem,” that is, the fear that some or all of the axonal degeneration stained and taken to indicate the projection of cells in a nucleus or cortical area could have ensued from interruption of fibers arising from cells in another region and passing through the region of cells lesioned, thus giving rise to a false-positive result. This was less of a problem in the cortex where, by simply stripping off a square of pia mater, one could devascularize the underlying cortex without causing significant damage to the deeper white matter. Making lesions of the thalamus was another matter. Stereotaxis was, of course, well known and had been used for years in neurophysiological experiments, and there were reliable stereotaxic atlases of the cat thalamus by Jasper and Ajmone-Marsan and of the monkey thalamus by Olszewski. But obviously, in relying on axonal degeneration to chart the cortical projections of a thalamic nucleus, there was the fear that the passage of an electrode through overlying cortex, white matter, and other nuclei would cause sufficient damage to lead to a spurious result. As a consequence, the study of thalamocortical connections lagged behind that of structures that lay on the surfaces of the cerebral hemisphere, cerebellum, spinal cord, or brainstem. We thus sought approaches to the thalamus that would permit an electrode to enter the ventral posterior nucleus without traversing other thalamic nuclei and minimizing damage to structures overlying the thalamus. It was here that our surgical skills became useful. In the cat, we found that we could introduce an obliquely angled, horizontal electrode that entered the ventral posterior nucleus from behind and laterally, avoiding the cortex and all other nuclei— providing, that is, that we first removed the tentorium cerebelli, which in the cat is bony. That required some skill because there was always a danger of tearing the lateral venous sinus and that would mean the end of the experiment. For the monkey, with a large temporal lobe, this approach was not feasible, so we introduced the electrode horizontally through the visual cortex and superior colliculus, first ascertaining by control passages of an electrode that we could identify the degeneration ensuing from any damage to these structures.

Determining the actual terminations of a set of degenerating axons was another source of contention, because the Nauta method that most neuroanatomists were using at that time undoubtedly did not stain degenerating terminal boutons. As a consequence, we quickly learned that if certain individuals were likely to review our papers, we had to speak of “preterminal” not “terminal” degeneration in describing the pattern of termination of a set of degenerating axons. This has always seemed an unnecessarily pedantic circumlocution to me, for the staining of ramifying degenerating axons, which was readily distinguishable from that of the degenerating parent axons, surely betokened termination in the region in which they lay. Even later, when new variants of the Nauta technique, notably that of Fink and Heimer, were confirmed by correlative electron microscopy to be staining degenerating terminals, there were still holdouts against the use of “terminal degeneration.” It all seems curiously irrelevant now.

Analyzing degenerating terminals at the electron microscope level also had its vicissitudes. I have mentioned the confusion briefly engendered by the appearance of the electron-dense and the neurofilamentous reactions in the terminals of cut axons, but here there could be other problems as well. Initially, few if any of us realized just how quickly terminals could degenerate, be phagocytosed, and disappear. You had to find the optimal survival time and this varied for different fiber systems. It could be remarkably short in fine-fibered systems. Failure to recognize this and, finding no degeneration of terminals in the dorsal horn 4 or more days after sectioning the dorsal roots of the spinal cord, led some to announce that these fibers did not terminate in the dorsal horn. Where would modern studies of pain mechanisms be if that had held up? It was only when other investigators used survival times as short as 24 hours that the terminations of the fine dorsal horn afferents were revealed. The terminals of thicker fibers degenerated over a longer time course but not too long. Finding no degeneration of terminals in the lateral geniculate nucleus after removal of an eye 2 weeks previously, and still finding none after increasingly longer survival periods, led others to announce that the use of terminal degeneration at the electron microscopic level was an unreliable method for studying connections.

Twenty-three full-length papers emerged from my productive 3 years in Tom Powell’s laboratory. If a reader thinks, however, that my whole life during that time was spent at the lab bench, he or she would be wrong. At least once a month Sue and I would make our way to London or to Stratford-upon-Avon and attend a performance of the National Theatre or Royal Shakespeare Company. In those days it was possible to see Olivier, Gielgud, Guinness, and most of the younger actors and actresses who later came to dominate the British and international stage for less than 5 shillings (a quarter of a pound). And every Sunday was spent exploring the English countryside with its often charming villages, old churches, and pubs. It is something that many years later Sue and I continue to enjoy on our visits to England and Wales. It was during our time in Oxford that our daughter, Philippa, was born, delivered at the Radcliffe Infirmary by no less a person than the Regius Professor of Obstetrics and Gynaecology, John Chassar Moir himself.

I was also haunting the Bodleian Library, where one could obtain from the stacks any book ever published in Britain and most of those published elsewhere, and where in the Radcliffe Science Library one could still see on open shelves all the volumes of the Philosophical Transactions of the Royal Society. I also spent time in the bowels of the library of the Royal Society of Medicine in London seeking out old medical works. My focus was on the development of ideas about sensation and perception and out of this came my first major historical paper on the rise of ideas about the sense of position and movement, highlighting the contributions of Henry Charlton Bastian, the coiner of the term kinesthesis.

Sue and I also managed to take one lengthy European trip each year. British restrictions on the export of currency at that time permitted us to take only £50 each. We traveled in a small car and slept in campgrounds in an even smaller tent that the German campers used to bring their children to laugh at. In the course of these trips, in addition to visiting the major centers in France, Germany, Austria, Scandinavia, the Netherlands, and Italy and some more remote ones such as the Dalmatian coast and the Norwegian fjords, I had my first experience at giving seminars when I paid visits to the Departments of Anatomy at Oslo and Rotterdam, the Max Planck Institut für Hirnforschung at Frankfurt, and the Brain Research Institute at Zürich. In those places, I enjoyed the hospitality of Alf Brodal, Hans Kuypers, Rolf Hassler, and Konrad Akert. Prior to my talk in Frankfurt, Hassler took me aside and, knowing I was a New Zealander, asked me if I could speak in Colonial rather than Oxford English since he felt that the audience would understand it better.

New Zealand Again

It was with considerable sadness that Sue and I and our young daughter said goodbye to Oxford and England. Under the terms of the Nuffield Demonstratorship, holders were expected to return to their own countries for 5 years (in my case reduced to 3 years). It was essentially a gentlemen’s agreement and many individuals in fact broke it and remained in Britain. I could have done so as well but felt that I had a responsibility to the Department of Anatomy in Dunedin which in my absence had promoted me to a permanent position and whose Faculty had been so supportive of me in obtaining the Nuffield award. In any case, Sue and I thought that we would eventually find our way back to Oxford. That was not to be.

We ended our days at Oxford, as I had begun mine, in the Sheldonian Theatre, where, sitting on those excruciatingly uncomfortable hard benches in its upper tier, we heard a concert by Sviatoslav Richter, the concluding work of which, the “Pictures at an Exhibition,” was played in the manner that only he could. We departed soon after. On our way back to New Zealand we were generously entertained in St. Louis by Max and Margaret Cowan. Max, after 2 years at the University of Wisconsin, Madison, had recently assumed the Chair of Anatomy at Washington University. Little was I to know that one day I, too, would find myself a member of its faculty. Sue and Philippa went on separately to New Zealand, and I embarked on a 3-week tour of U. S. universities, giving seminars at several of them. The hospitality that was extended to me by such people as Irving Diamond at Duke, David Bodian and Vernon Mountcastle at Johns Hopkins, James Sprague at the University of Pennsylvania, Ray Guillery at Madison, Torsten Wiesel at Harvard, and Larry Kruger at UCLA was exceedingly generous, and my talks with Irving Diamond and Torsten Wiesel in particular were later to help persuade me that my family and I could adapt satisfactorily to life in a culture which at that time was essentially foreign to us. In the course of this peripatetic tour, I was flattered to be offered faculty positions at two of the prestigious institutions mentioned, but I declined them, feeling that I had a commitment to New Zealand and still convinced that eventually I would find my way back to the United Kingdom. How things might have been different had I accepted, I do not know.

The 3 years that I spent back in New Zealand were productive ones despite a heavy teaching load and the relative isolation from the rest of the scientific world. It is hard to imagine now a scientific environment where journals arrived by surface mail 3 months after their publication and where many routine laboratory supplies, mostly obtained from Britain, took a similarly protracted time course before delivery. Commonly, chemicals obtained in this way arrived in poor condition. Glutaraldehyde, for example, arrived with a pH of close to 3, much of it having been oxidized to glutaric acid and requiring lengthy passage through activated charcoal for purification.

I was eventually able to obtain most of the equipment that I needed for light and electron microscopy, including a new Philips electron microscope, one of only two in New Zealand at that time. But in the early days I had to make do with a number of items that were really quite out of date. I may have been the last person routinely to have cut thin sections with a prototype model Cambridge-Huxley ultramicrotome in which a lever was elevated and then allowed to drop in order to cut the sections. After a year, thanks to a small grant from the New Zealand Medical Research Council, I was able to buy a modern Porter-Bum model. The necessity in the early days for making do with ancient equipment had its amusing side. Needing a sliding microtome for cutting frozen sections, I applied to the chief technical officer in the Anatomy Department—he was called the Steward. He took me to a room that seemed filled with Victorian junk and extracted from it a classic AO sliding-block microtome, a beautiful old instrument but clearly past its prime. Thereupon the following exchange took place: Jones: “It’s a bit old, isn’t it?” Steward (drawing himself up to his full height): “This was bought for Dr. Denny Brown in 1923.” Derek Denny Brown, like myself, had started out in that Anatomy Department before moving to Oxford to work with Charles Sherrington and then on to the United States, where he became Professor of Neurology at Harvard Medical School. There seemed little to be gained in pointing out that this was the year in which Denny Brown had retired from Harvard. It was only later, after a visit to the medical history museum at Melbourne University in Australia where the same instrument had pride of place in its own case and beneath spotlights, that I learned that mine had in fact been built in 1909 and that it had been bought secondhand for Denny Brown! Apprised of that, the Dean of the Medical School bought me a new sliding microtome.

The last paper from the Oxford years was written after my return to New Zealand. Prior to leaving Oxford I had analyzed the brains in which I had made the cortical lesions in monkeys that permitted Janet Kemp to define the topography of the corticostriatal projection. These lesions were scattered across the greater part of the surface of the hemisphere and involved both primary and secondary sensory and motor areas and many association areas as well. From these brains it was possible to define the chains of cortico-cortical connections (now called hierarchical) leading away from the primary areas and across the association areas, with eventual convergence of pathways emanating from somatosensory, auditory, and visual cortex in areas of the frontal and temporal lobes. It was one of the first studies of its type, for investigations of the association cortex lagged even further behind those of the primary areas. I wrote it up as “An Anatomical Study of Converging Sensory Pathways in the Cerebral Cortex” and sent it off to Tom Powell. Now Tom had an unusually Calvanistic approach to publication and felt that if, as in this case, he had not sweated over the analysis of the results, as he invariably did with all his students, then he did not qualify to be an author. He, therefore, suggested that we submit it over my name only. I, naturally, demurred so he submitted it to Brain but accompanied it by a personal letter to the Editor, Denis Williams, apologizing for submitting yet another lengthy study and saying that it would be the last for some time. In a couple of weeks, back came the following note from Williams: “Dear Tom, Your importunity softens me, but the prospect of years of silence for the price of acceptance seems to me a bargain. The paper will appear as it stands . . . . . . . . . ” I wish one could negotiate publication that easily today. The paper was duly published; it became one of our most widely quoted papers and one still sees it referenced in studies of higher order processing in the cerebral cortex.

In New Zealand I continued the same themes that I had followed in Oxford, using the axonal degeneration-based techniques to pursue thalamic and cortical connectivity of the areas intercalated between the visual, auditory, and somatosensory areas of the cat, work which led to a lengthy monograph on the organization of the suprasylvian gyrus of the cat in which, among other things, areas 20 and 21 were identified for the first time. There were also studies of cortical and thalamic connections in my old animal friend the brush-tailed possum, a member of the class of diprotodont marsupials in which the absent corpus callosum is replaced by the remarkable fasciculus aberrans joining the two internal capsules across the top of the anterior commissure. In the thalamus of this animal we were able to dispel the myth that in animals low on the supposed evolutionary scale, the three great sensory pathways converged to a considerable extent in the thalamus. They definitely did not and in fact the possum ventral posterior nucleus, in containing barreloids that project to barrels in the somatosensory cortex, is comparable to that of the mouse. In this work I was joined by Chris Heath, a recent medical graduate who would later, like me, go as a Nuffield Dominions demonstrator to Oxford where he worked in the University Laboratory of Physiology with Charles Philips defining the Group I afferent input to area 3a of the monkey.

At the electron microscopic level, the chief focus was on the structure and connectivity of the medial geniculate nucleus and the source of its input, the inferior colliculus. It was from this work that the commonality of afferent terminal organization in the thalamic sensory relay nuclei that we had recognized at Oxford was further confirmed. In this work I was joined by Tony Rockel, like Chris Heath another recent medical graduate and one who would go on to Oxford to work with Tom Powell. In the course of this work they described what for a long time became a recognized principle of cerebral cortical organization, namely the uniformity of cell numbers in columns extending through the thickness of the cortex, regardless of species. Although it has never been entirely ruled out, the weight of evidence now seems to be that this may not always be correct.

It was during the work on the inferior colliculus that I put into practice an approach that I had become convinced in Tom Powell’s lab was essential if we were further to unravel the internal circuitry of any brain region. Electron microscopy, although at the synaptic level of organization, had too narrow a field of view and could not readily reveal the cell-to-cell connections, especially those that formed the chain of connections leading from input to output. It is an issue that still exercises the minds of neuroscientists, especially those who work in the cerebral cortex, and for which there is no easy solution short of the sheer brute force reconstruction of millions of thin sections or the painstaking intracellular injection of dyes into cells and the reconstruction of the synapses made by their axons in serial electron micrographs. In attempting to deal with this issue in those early days it became clear to me, and to a number of other neuroanatomists of the time, that it was necessary to reexamine the cells of the CNS and, armed with the new knowledge derived from electron microscopy, to try to understand where each type fitted into the circuitry of the regions in which they were located. To do this, we turned to the old Golgi technique, which was still the only method available for visualizing CNS neurons in their entirety. Tony Rockel had a real flair for the Golgi technique and, as I watched him building up the picture of cellular organization, including the peculiar stacks of lamellae that form the basis for the tonotopic organization of the central nucleus, I realized that it was this technique that had to be applied if we were ever to construct a circuit diagram of the cerebral cortex. I had already determined that in the next phase of my research, which I knew would have to be conducted outside New Zealand, I would return to the fine structure of the cerebral cortex and use the Golgi technique to inform what I would be seeing at the synaptic level.

St. Louis

As time passed in New Zealand, it became increasingly clear that a return to an underpaid junior post at Oxford would not be realistic and I turned my attention to the United States and to Max Cowan, who was happy to offer me a faculty position in his new department at Washington University. In preparation for the move, I wrote my first National Institutes of Health (NIH) grant application from New Zealand. It was funded after my arrival in the United States and was continuously renewed for the next 37 years. If I should have expected some recognition from the National Institute of Neurological Disorders and Stroke (NINDS), the NIH Institute that had funded the grant, of this long-standing support when I chose not to renew the grant, I would have been mistaken.

The family, now made up of Sue, myself, Philippa, and our son, Christopher, who had been born in Dunedin, set out for St. Louis in January 1972 and arrived there soon after. The first year there was not a happy one. Within days of our arrival, Max announced that he was leaving for another university, which was disconcerting to say the least. He never did leave but his flirtation with this and other universities went on throughout my first year; it was most unsettling to his entire faculty and not conducive to the development of good relations among them.

I commenced working, as I had planned, on the classification of neurons in the somatosensory and motor cortex of the squirrel monkey, using the Golgi technique. Making these studies in a monkey was a fortunate choice because, as the different cell types began to become evident, it was much easier to match them to the types that Cajal had originally described in the cortex of another primate, the human, and cell types that had not been seen since Cajal’s day began to emerge. In the intervening years, most Golgi studies of the cortex had been carried out on rodents and cats in which the cortical neurons are less stereotyped than in primates and in which certain forms may even be absent. I can take credit, I am told, for rediscovering the double bouquet cell that Cajal had thought was unique to the human. I shall never forget my amazement in watching the long bundle of axon collaterals appear as I drew the first of these cells with the camera lucida. The bundle gradually filled up a series of panels of tracing paper that extended from the microscope continuously over the floor of my office and out into the laboratory. Comparing these cells with the large basket cells, the neurogliaform cells, and the chandelier cells which Cajal had never seen (probably because he invariably used material from infants in which their distinctive morphology is not yet developed) convinced me that it was possible to make a classification of cell types that could serve as a basis for developing a circuit diagram of the cortex. I was not alone in this. Others, such as Jennifer Lund, Alan Peters, and Janos Szentágothai and his students, working on the visual cortex of monkeys, rats, and cats, respectively, had all recognized this as well.

In my first classification of cortical neurons in the monkey, I stressed that they fell into two classes: those with substantial numbers of dendritic spines and those without. Among the first group were the pyramidal neurons, all of whose axons left the cortex, and the small spiny neurons of layer IV with their strongly recurrent axon branches extending upward into supervening layers as far as layer I. I could never persuade myself to call these spiny stellate neurons, as people were doing in the visual cortex, for in the areas that I was looking at they were drawn into an elongated form with a lengthy ascending dendrite. Lorenté de Nó in the mouse called them star pyramids. It was these cells that led me to insist that cortical neurons should be divided into pyramidal and nonpyramidal forms and not into pyramidal and stellate forms; this quickly caught on.

Apart from the small spiny neurons of layer IV, all the other nonpyramidal neurons of the cerebral cortex were essentially aspiny and this has subsequently been shown to be a hallmark of cortical GABAergic interneurons. They all differ in size, in configuration of the dendritic tree, and especially in their axonal ramifications. Among them, six stereotyped forms could be recognized in the monkey. These I called Types I through VI, the large basket cells being Type I, the double bouquet cells Type II, and so on. The small spiny cells of layer IV, being interneurons as well, were referred to as Type VII. Much later, like the pyramidal neurons, they were shown to be glutamatergic and excitatory. My use of a Type classification rather than the colorful terms applied to the cortical neurons by Cajal and others got me into trouble for, when at a meeting in Germany in describing my types and referring to the use of the older terms by Szentágothai as reflecting the usage of a classical middle European romantic, he retorted by saying that in referring to the neurons as mere types, I was attempting to reduce the brain to a piece of classic British understatement. He won, and we continue to use the older, morphologically descriptive names.

I hadn’t planned on doing any further connectional work of the type that I had carried out in Oxford and Dunedin. Indeed, in completing the monograph on the suprasylvian gyrus of the cat I can remember remarking to Chris Heath: “Well, that’s the last of the great connection tracing studies.” How wrong I was. Before my arrival in St. Louis, an autoradiographic technique, based on the axoplasmic transport of radioactive amino acids which, after injection around the cell bodies of neurons were converted into macromolecules and transported to the terminals of the axons, had been devised. A number of different laboratories had been involved in perfecting the technique, among them those of Anita Hendrickson, Steven Edwards, and Max Cowan. It offered many advantages over the Nauta techniques for the tracing of connections, not the least of which was its freedom from the “fiber of passage problem” since axons, even if they took up the radiolabeled amino acids, did not possess the metabolic machinery that would allow them to convert the amino acids into the macromolecules that were the form in which the radioactivity was retained after aldehyde fixation. Then, shortly after my arrival in St. Louis, Jennifer Lavail in San Francisco and Krister Kristensson and Lars Olson in Stockholm recognized that the phenomenon of retrograde axoplasmic transport could be harnessed as a technique for studying connectivity. Here, protein molecules, notably horseradish peroxidase (HRP), which could be visualized by a simple enzymatic reaction and had previously been used as a marker for extracellular space at the electron microscopic level, after being injected into the terminal field of a set of axons, would be taken up by those terminals, transported in their parent axons backward to their cell bodies of origin, and thus serve as a marker for connections. The opportunity to apply these two new techniques was too good to miss, even though it distracted me somewhat from my principal objective of unraveling the circuitry of the cerebral cortex. I commenced work with the autoradiographic technique on thalamocortical connections in monkeys, work in which I collaborated very successfully with Harold Burton and in which we charted the outputs of nuclei around the caudal pole of the ventral posterior nucleus that were thought to form components of the central pain pathways, with observations on the projections of the nuclei of the pulvinar and of the medial geniculate complex as well. Out of this work came a very comprehensive parcellation of the cortical areas on and around the insula and the observation that it was only in the granular, primary sensory areas of the cortex that thalamic afferents ended in layer IV. In nonprimary and association areas they ended only in the deeper part of layer III and even in the granular areas the terminations in layer IV extended well up into layer III. Surprisingly, this observation has never entered into the consciousness of the majority of neuroscientists and we still hear of layer IV as being the terminal layer for all thalamocortical projections.

The autoradiographic technique also permitted me to restudy the cortical connections of areas 3, 1, and 2 in the postcentral gyrus, confirming many of my earlier observations made with the Nauta technique and to make new ones. Among the latter was the surprising finding that areas 3a and 3b did not project forward to the motor cortex but back into areas 1 and 2 from which the somatosensory projections to the motor cortex emanated.

In applying the HRP technique I made the unexpected discovery that the intralaminar nuclei of the thalamus projected not only to the striatum, as Tom Powell and Max Cowan had shown with retrograde degeneration techniques, but also to the cerebral cortex. Tom and Max had discounted this, seeing the modest cellular degeneration that occurred in the intralaminar nuclei after cortical lesions as a form of anterograde transneuronal atrophy consequent upon the loss of corticothalamic fibers. Others, notably Marion Murray, had disagreed, seeing the cellular reaction as truly retrograde in character and thus indicative of a cortical projection. When I showed Max Cowan the retrogradely labeled cells in the intralaminar nuclei after the first injection of HRP in the cortex, his response was a single word and it was uncharacteristically profane. Others, notably Herbert Jasper, who had felt that a widespread cortical projection from the intralaminar nuclei to the cerebral cortex formed part of a cortical arousal system, were delighted.

Working in the main with my first American student, Steve Wise, we mapped the laminar distribution of the cells of origin of the corticocortical, commissural, and subcortical projections of the somatosensory and motor cortex in the monkey, and Steve used both autoradiography and HRP to map out the connections of the somatosensory cortex in the rat much as I had earlier done using the Nauta technique in the monkey. Steve also carried out our first studies on the development of thalamocortical and commissural connections in the rat, studies that were to continue at the hands of Mary Kay Floeter, Karen Valentino, David Schreyer, and Isobel Scarisbrick. I myself focused on the reticular nucleus of the thalamus, plotting out its two-way innervation by the collaterals of thalamocortical and corticothalamic fibers passing through it and its output to the nucleus of origin in which these fibers begin or end, a pattern that forms one of the bases of thalamocortical function. This is one of my earlier papers that continues to be widely referenced.

While all this was going on, I became more and more convinced of two things. First, that it was imperative to localize the origin and terminations of axons as demonstrated anatomically in relation to the physiologically recorded properties of their nuclei or areas of origin and termination. Second, that it was necessary to present the visual evidence for origins and terminations in specific nuclei or areas in wide-field, low-magnification photomicrographs that unequivocally identify the nucleus or area as regions with defined anatomical identities. I was firmly convinced of the latter when, during my first year in St. Louis, I joined Alvin Berman of the University of Wisconsin, Madison, in preparing an atlas of the cat forebrain that was published in what publishers call an elephant folio. The huge 16-inch by 18-inch photomacrographs were made as contact prints from large glass plates that had been exposed on an old horizontal optical bench of the type used by neuroanatomists of bygone years for illustrating brain cytoarchitecture. Ever since, I have made a specialty of photomacrography, first optical and later digital, and some of my current work, as we shall see, continues to involve this.

The value of photomacrography of this kind can be seen in the comprehensive study that Chisato Asanuma and I, working in collaboration with Thomas Thach and using the autoradiographic technique, made on the terminations of the major afferent pathways from the spinal cord, dorsal column nuclei, deep cerebellar nuclei, globus pallidus, and substantia nigra in the ventral nuclear complex of the monkey. This work enabled us to say, by contrast with the prevailing view, that the terminations did not overlap and where they ended in the same nuclei, as with the spinal and deep cerebellar inputs, they interdigitated rather than converged. This was not a view that pleased all; and our redrawing of some of the borders between nuclei drew ire as well. I have never ceased to be amazed at how so many of my colleagues, mostly electrophysiologists, seem to conceive of the monkey thalamus as a series of pages from Olszewski’s atlas. Had they read his text, they would have seen that where we were drawing new borders they were in regions where he regarded his divisions as “provisional.” Gradually, I am pleased to say, our divisions have become generally accepted. When later, Giorgio Macchi and I and then Tatsuo Hirai and I in our atlas of the human thalamus, attempted to extend our nomenclature to the human thalamus, thus rationalizing the different nomenclatures that had been applied to experimental primates and humans, we experienced similar resistance mainly from European sources from whence the human nomenclature had sprung. I am pleased to say that, here also, our rationalization of the nomenclature has begun to catch on in neurosurgical circles.

As to neurophysiological techniques, I have always used them in the service of neuroanatomy, not the reverse in which a trivial piece of anatomy is appended to a neurophysiological study in order to satisfy an editor or a review panel. I gradually taught myself neurophysiology and reinforced it during a brief sabbatical at Monash University, Australia, working with David Tracey in the laboratory of Robert Porter with whom I had overlapped in Oxford. Using single- and multiunit recording techniques, David Friedman and I were able to produce a high granularity map of the body surface in the monkey ventral posterior nucleus and to show from tiny injections of radioactive amino acids that its central cutaneous core projected to areas 3b and 1 while the anterior part of its shell region, which received inputs from low-threshold muscle afferents, projected to area 3b, and the posterodorsal part, in which neurons were activated by less clearly definable deep stimuli, projected to area 2. Other work, carried out on the thalamus of the cat with intracellular recording and injection techniques, enabled Chen-Tung Yen and me to recover for anatomical analysis thalamocortical neurons defined in terms of their sensory inputs, one of the few studies of its type ever carried out.

The latter years at Washington University were the early years of what was to become called chemical neuroanatomy. This was the era when immunocytochemistry was being perfected and when the growing availability of antibodies to neuroactive substances made it possible to study the chemical properties of neurons and neuronal pathways in terms of their neurotransmitters and other neuron-specific molecules. It was the availability of an antiserum to glutamic acid decarboxylase (GAD), the enzyme involved in GABA synthesis, that led us back to the cerebral cortex. Working in collaboration with Caroline Houser and James Vaughn, we showed that all the nonspiny neurons of the monkey cortex and their synapses were GABAergic. Soon after that, Stewart Hendry and I were able to show that a small population of GABA cells in superficial layers of the cortex and in the white matter underlying it was also immunoreactive for various neuropeptides, notably cholecystokinin, substance P, or neuropeptide Y.

University of California, Irvine

I left Washington University to take up the position as chair of the Department of Anatomy at the University of California, Irvine. It was soon to become the Department of Anatomy and Neurobiology but, it being in the University of California, this name change was not accomplished without vehement argument. It was a small department that could be easily administered and this gave me plenty of time to continue to pursue experimental studies. Although it required some academic building at first, the department was soon generating more research grant income than any other department in the medical school; it was eleventh among anatomy departments nationwide and in the UC system second only to UC San Francisco, whose anatomy department had more than three times the faculty. I was obviously very proud of this, but it was a terrible indictment of the clinical departments at UC Irvine.

At UC Irvine the work on the chemical characterization of neurons in the monkey cortex continued. We were fortunate, thanks to the generosity of Piers Emson, to be among the first laboratories to have access to antibodies to the calcium-binding proteins, parvalbumin and calbindin, and in using these we could for the first time divide the GABAergic, nonspiny neurons of the cerebral cortex into subtypes. Those such as the large basket cells and the chandelier cells expressed parvalbumin while those such as the double bouquet cells expressed calbindin. A key member of my laboratory in carrying out this work was Javier DeFelipe from the Cajal Institute in Madrid, who identified the remarkable, candle-like terminals of the chandelier cells as ending on the axon initial segments of pyramidal cells and the regular minicolumnar arrangement of the bundles of double bouquet cell axons as they descended through the cortex, ending in the inhibitory synapses that I had seen so long ago on some of the dendritic spines on the side branches of apical and basal dendrites throughout the thickness of the cortex. At the same time, Stewart Hendry in the lab was demonstrating the activity-dependent down-regulation of GAD immunoreactivity and up-regulation of the alpha subunit of Type II calcium/calmodulin-dependent protein kinase (CAMII kinase) immunoreactivity in ocular dominance columns of the monkey visual cortex deprived of input by removal of or injection of tetrodotoxin into an eye. Later, when molecular techniques were introduced into the lab, Deanna Benson was to show, using in situ hybridization histochemistry, that these changes were the result of down- or up-regulation of gene expression. The monocularly deprived monkey visual cortex became one of the best models for the demonstration of activity-dependent changes in gene expression and Stewart Hendry, Molly Huntsman, and Brahim Tighilet were to use it extensively in demonstrating the effect of lack of afferent activity on expression of glutamate, neuropeptides, the subunits of the GABA-A receptor, the subunits of ionotropic glutamate receptors, and other subunits of Type II calcium/calmodulin-dependent protein kinase. Fengyi Liang extended this work by using an epilepsy model. We were also able to show that the alpha subunit of CAMII kinase was only expressed in glutamatergic neurons of the forebrain. Xiao-Bo Liu confirmed this electron microscopically by showing its presence at glutamatergic synapses and its absence at GABAergic synapses in the cerebral cortex, hippocampus, and thalamus.

Physiological work was going on in parallel with all this anatomical work. George Huntley mapped the monkey motor cortex by microstimulation and showed, using injections of tracer at defined sites in the representation of a structure such as a finger that such a site has horizontal intracortical connections, formed by the collateral axons of pyramidal cells in layers II and V, which spread throughout the hand representation and thus form a substrate for the recruitment of motoneurons projecting to the many different muscles engaged in any movement. We also continued our intracellular staining of neurons and axonal terminations in the cat thalamus. This work, carried out by Chris Honda, Harry Schwark, Tatsuo Hirai, and Chen-Tung Yen, resulted in the only preparations of injected medial lemniscal axons that have ever been acquired, and the injected cells, in being taken to the electron microscopic level by Xiao-Bo Liu, furnished some of the few preparations in which the synaptic geography of thalamic neurons has been delineated in a quantitative manner. Liu and Richard Warren complemented this work on the thalamic relay cells by a study in which the labeled axons of cells in the reticular nucleus were traced to their terminations in the ventral posterior nucleus and showed that their synapses formed a far greater proportion of the inhibitory synapses on relay cells than did those of the intrinsic interneurons. We followed this up by demonstrating that the synapses of corticothalamic collaterals dominated the inputs to the reticular nucleus and that in the ventral posterior nucleus they ended predominantly on relay neurons rather than on interneurons.

At around the same time, Aric Agmon joined the lab and introduced us to the oblique thalamocortical slice from the mouse that he and Barry Connors had developed and to patch clamp recording in vitro. This preparation enabled Aric and Richard Warren to demonstrate, along with other labs, how the interconnected thalamo-cortico-thalamic network could generate low-frequency oscillations, dependent upon the low-threshold calcium conductance in relay cells and the interaction between the inhibitory reticular nucleus input to these cells and the reentrant excitation of reticular cells by the collaterals of the cortically projecting axons of the relay cells. Later, in the same in vitro preparation, Peyman Golshani, my last M.D., Ph.D. student, would show that the corticothalamic input to the reticular nucleus is up to three times more powerful, as measured by the recording of unitary excitatory postsynaptic currents, than that to the relay cells, even though the inputs are formed by branches of the same axons, an effect that we showed depends upon the expression of up to three times as many GluR4 subunits of the ionotropic glutamate receptor at the synapses in the reticular nucleus. Aric Agmon was also brilliantly to exploit the thalamocortical slice preparation in studying the ingrowth of thalamocortical fibers into the somatosensory cortex during development in the mouse, showing that this occurred as directed growth and elaboration of terminations rather than as an early diffuse ingrowth with later withdrawal of so-called exuberant branching.

By this time, autoradiography had been phased out as a neuroanatomical tracer and newer tracers had come on the scene, notably the fluorescent dyes for retrograde tracing, wheat germ agglutinin conjugated HRP for anterograde and retrograde tracing, and Phaseolus vulgaris leukoagglutinin (PhAL) for anterograde tracing. These we exploited in studies of spinal and medial lemniscal inputs to the monkey thalamus and in revisiting thalamic projections to the postcentral gyrus, mostly in work carried out with Estrella Rausell. One of the discoveries from the application of immunocytochemical staining of the monkey thalamus for the calcium-binding proteins was that relay cells in that thalamus were either parvalbumin or calbindin immunoreactive and that nuclei differed in the proportions and distributions of each cell type. In tracing lemniscal and spinal pathways to the thalamus, we found that they ended in complementary fashion, the lemniscal fibers around parvalbumin cells and the spinal and spinal trigeminal fibers around calbindin cells. Moreover, when we looked at the cortical projections of the two classes of cells, we found that the parvalbumin cells projected in topographic order to layer IV and deep layer III of the somatosensory cortex, while the calbindin cells projected diffusely over adjacent areas and ended only in more superficial layers. It was a pattern that we were to find repeated in other thalamic nuclei and their cortical projections and it was from this that my theory of a specifically innervated and projecting thalamic core and a diffusely innervated and projecting thalamic matrix was developed.

The concept of activity-dependent cortical plasticity was beginning to make itself felt in the laboratory and, unlike most specialists in the field, I found it hard to believe that the representational plasticity that one sees in the somatosensory cortex after section of peripheral nerves or amputation of a digit or part of a limb could be due entirely to intracortical mechanisms. Remembering from my work with Tom Powell that deafferentation of CNS neurons commonly led to transneuronal effects, even to degeneration, I was convinced that if these were occurring at lower relay centers such as the dorsal column nuclei and thalamus then they would be projected upward to the cortex and reinforce or even induce the representational changes that were occurring there. It also seemed to me that we were too focused on the point-to-point topography in the cortical projections of individual thalamic cells and that, if we looked at the projection of the population of thalamic cells that received input from, say, a finger, this would outline a much larger cortical domain so that, if an adjacent part of the representation were deactivated, then inputs in these widespread projections that had previously been suppressed would be revealed and serve as a basis for expansions of the map of an intact finger into that previously occupied by an amputated one. It was not a view that many would accept. To give it support we had to prove that there was widespread overlap in the thalamocortical projection and that withdrawal of part of this projection would not lead to a silent area in the cortical map. So with Estrella Rausell we showed using anterograde transport of differently colored fluorescent dyes injected into defined parts of the thalamic representation of the body surface that the projection emanating from 0.1 mm3 of the thalamus could subtend as much as 20 mm2 of the cortex, with extensive overlap of inputs from different parts of the thalamic representation. Then with Paul Manger, who had mapped the representation of the face and intraoral structures for the first time at high density in the somatosensory cortex, we began to make a series of lesions of increasing size in the thalamus, after which we examined the cortical map with multiunit recording arguing that, because of the overlap in the thalamocortical projection, smaller lesions would have little effect upon the map but that as they increased in size parts of the map would drop out, perhaps being replaced by expanded representations of adjacent parts.

We found in support of our hypothesis, but with considerable surprise at its extent, that we could destroy as much as 25% of the hand representation in the ventral posterior nucleus before the cortical representation of the hand began to shrink. Our view that deprivation of sensory inputs would have effects upon lower centers would be magnified by the divergence of projections from these centers to the next higher center and thus onto the cortex received vindication when, thanks to Tim Pons, we were given the brains of a number of the so-called Silver Spring monkeys that had survived for up to 20 years after sustaining dorsal rhizotomies of all the nerves innervating the upper limb. In these animals, in which multiunit mapping had revealed an expansion of the intact face representation into the silenced upper limb representation in the somatosensory cortex and thalamus, Tim Woods and I showed that there was a progressive transneuronal atrophy of the cuneate and external cuneate nuclei and of the upper limb region of the ventral posterior nucleus, with some but by no means huge loss of neurons in both sites; in the thalamus the atrophy led to collapse of the face representation into that formerly occupied by the upper limb representation. From this we argued that, as deafferented neurons were undergoing transneuronal atrophy, they would likely be withdrawing their axons from higher centers and that this would promote expression of hitherto silent inputs from adjacent, unaffected regions, with expansion of the cortical map of those regions. This was, of course, conjecture but later, in experiments carried out on monkeys surviving for 2 or more years after section of the cuneate fasciculus at the first cervical level, Alessandro Graziano and I were able to show directly by anterograde labeling of the axons of atrophying cells that they did indeed undergo loss of terminal branches and reductions in the number and size of their terminal boutons in both the thalamus and cortex. I anticipate that after 20 years, as in the Silver Spring monkeys, this effect would have been even greater.

My years at UC Irvine were characterized by other activities, some of them nonscientific. My arrival there coincided with the publication of the first edition of my book The Thalamus, which to my surprise became one of the most referenced works in neuroscience. I have to confess that I wrote it in order, as I said at the time, to get the thalamus out of the way so that I could concentrate on the cortex. Indeed, at that time and over ensuing years Alan Peters and I were editing a series of books entitled Cerebral Cortex that attempted to bring knowledge of the cortex in review form to the neuroscience community. But as a reader of the foregoing will have observed, I was drawn more and more into the thalamus, and this attraction was enhanced by my growing association with two of the most talented thalamic neurophysiologists of modern times, Mircea Steriade and Rodolfo Llinás. With them I developed close friendships and enjoyed recurrent battles over interpretations of data. The battles go on with Rodolfo but those with Mircea sadly ended when he died. With them I wrote one book and with Mircea and a third talented neurophysiologist, David McCormick, we wrote and edited a two-volume work entitled Thalamus that was only superseded when the second edition of my own The Thalamus was published in 2007.

The middle of my UC Irvine period was highlighted by publication of a translation that Javier DeFelipe and I made of all Cajal’s works on the cerebral cortex. Javier translated the Spanish into what I can only describe as an intermediate language, which I converted into a form of English that I hoped would capture some of the character of Cajal’s orotund style while maintaining readability; and I struggled my way through translations of various French and German publications in which some of Cajal’s work had appeared. Every word was fought over. I never became fluent in Spanish but I learned sufficiently to be able, when having an honorary M.D. conferred upon me by the University of Salamanca, to give the first and last parts of my acceptance speech in Spanish, at the conclusion of which the rector complimented me— on my English! Javier and I also edited and reworked Raoul May’s earlier translation of Cajal’s Degeneration and Regeneration of the Nervous System. This was done mainly during 1989 when I spent a brief sabbatical as visiting fellow at my old Oxford College, St. John’s, in a year in which I helped my old mentor and friend, Tom Powell, into retirement. Since then, Javier and I together or individually have published a number of works on Cajal, whom I have come to see not only as a great observer but as one who unerringly was able to extract fundamental biological principles from his observations, while also recognizing his huge capacity for self-promotion, uncommon in his era but which would do credit to any modern would-be Nobel prize winner. I have never been particularly comfortable with that sort of thing, perhaps on account of my upbringing in a determinedly egalitarian corner of empire.

During 8 years of my UC Irvine days, I was also the part-time director of a laboratory in Japan. With Masao Ito and Keiji Tanaka, mine was one of the three labs of the Frontier Research Program at the RIKEN Institute that quickly expanded and eventually grew into the RIKEN Brain Research Institute. I would travel to Japan three or four times a year, invariably spending at least one long period of a month there when I would bring a team of former students and postdocs, invariably including Marco Molinari, who had worked with me at UC Irvine, and some of his Italian colleagues, notably Elizabetta dell’Anna and Mariella Leggio, and we would work hard at neuroanatomical studies of the monkey auditory cortex. In the course of these, the duality of the parvalbumin and calbindin thalamocortical projection systems was again substantiated and a comprehensive chemoarchitectonic map, with correlative single-unit mapping, was produced. Tsutomo Hashikawa, my deputy, was the mainstay of this work, while Yasuo Kawaguchi carried out his important work on cortical interneurons distinguished not only by the expression of one or other of the calcium-binding proteins but also on the basis of their tonic or burst-firing properties, the first study of its kind. A third member of the team was Hisayuki Ojima who, in his intracellular studies of neurons in the cat auditory cortex, demonstrated the widespread distribution of intracortical and subcortical branches of layer V corticothalamic cells and the highly focused nature of the collaterals and thalamic terminations of the layer VI corticothalamic cells.

At the end of my days at UC Irvine, I was elected President of the Society for Neuroscience and took up that position after I moved to be Director of the Center for Neuroscience at UC Davis. The year of my Presidency coincided with the end of the Congress-mandated Decade of the Brain, during the course of which the NIH budget had been more than doubled. A feature of my Presidency was the meeting that the Society organized at the National Academy of Sciences building in Washington, DC, that, apart from allowing us to highlight the contributions that had been made to the understanding of the brain by showcasing some of the Society’s best speakers, was attended by prominent individuals who had helped shape the Congress’s policy toward science and medicine and included the late Senator Edward Kennedy, a number of Congressmen and women, and the actor Christopher Reeve. The latter part of my Presidency was less satisfying. It was becoming clear that all was not well in the central office and that radical changes would have to be made. But doing this precipitately would have placed the success of the annual meeting, upon which the Society’s financial survival depended, in jeopardy. I, therefore, elected to proceed slowly and it took two subsequent presidents before the problems were solved, and a new administration put in place, with the effect that the Society is flourishing and is a far more professional organization that it had been in the past.

University of California, Davis

I was recruited to UC Davis and its Center for Neuroscience by the persuasive powers of my long-standing friend and occasional collaborator, Leo Chalupa. There, I experienced a highly supportive administration that was determined to move the university ahead in the field of neuroscience and to do it in a manner that integrated neuroscientists across the College of Biological Sciences, the School of Medicine, the College of Letters and Science, and other smaller entities. I was given the opportunity to add 10 more faculty to the Center, which had been founded mainly as a cognitive and systems-oriented center by another old friend, Michael Gazzaniga, and to add the dimensions of cellular, molecular, and developmental neuroscience. Given sufficient resources of laboratory space and startup funds, I was able to compete effectively with other, perhaps better known institutions and to recruit some of the finest younger neuroscientists, all of whom are now rising to their peak years and are bringing recognition to UC Davis in the way that those who had the confidence to appoint me would have wished.

Much of the research that has been carried out in my lab at UC Davis has been a continuation of that commenced at UC Irvine and I have already mentioned some of it. Increasingly, chemical neuroanatomy has become molecular neuroanatomy as we have looked at patterns of expression of genes involved in the major neurotransmitter systems of the brain and in its development, with recent forays into the discovery of genes, often of unknown or unexpected function, that determine the phenotype of neurons and of nuclei in the thalamus and of areas of the cerebral cortex. This is work that has been conducted primarily by Karl Murray and Prabhakara Choudary, working at times in collaboration with Leo Chalupa. There has been one last foray into the field of connectional neuroanatomy when Alessandro Graziano and I carried out a series of experiments in monkeys that debunked the view that all the fibers arising from pain and temperature-specific neurons in the dorsal horn of the spinal cord terminate in a tiny, calbindin-immunoreactive nucleus at the caudal end of the thalamus, a nucleus that no one else, including me, has ever seen.

As I have grown older, my research program has become less expansive than in the past and is now focused in two areas. One of these involves a remarkably successful consortium made up of scientists and clinicians at UC Irvine, UC Davis, the University of Michigan, Stanford University, Cornell-Weill Medical College, and the HudsonAlpha Research Institute. Generously funded by the Pritzker family and by the NIH, it focuses upon discovering genes that confer susceptibility to schizophrenia, major depression, and bipolar illness and on their expression patterns in normal and diseased brains. Thanks to the efforts of Dr. William (Biff) Bunney and his staff at UC Irvine, the consortium has built up one of the most thoroughly characterized human brain banks in the world, and we have spent a good deal of time in developing methods for ensuring that the tissue from brain slices frozen at autopsy can be recovered at a level of histological quality that rivals that obtainable in experimental animals. The consortium has also, through years of often frustrating effort, developed guidelines that determine to what extent the process of death (the agonal state) will interfere with the validity of gene expression profiling. The brain bank had its origins at UC Irvine, where Biff Bunney and I had collaborated on a number of projects, the most important of which, carried out by Schahram Akbarian in my lab, revealed the consistent down-regulation of expression of GAD in superficial layer neurons of the dorsolateral prefrontal cortex in the brains of schizophrenics, an observation that, unlike many in the field of schizophrenia research, has been replicated many times. Since then, with Huda Akil, Jack Barchas, Richard Myers, Alan Schatzberg, and Stanley Watson and their teams, Dr. Bunney and I have pursued many avenues of moleculargenetic research into the bases of these complex but important diseases. Results for us, as for all others in the field, have been frustrating and it seems clear that what were once thought to be powerful techniques that would help us unravel causes and effects have proven to be inadequate. Nevertheless, newer generation of techniques of increasing analytical power are being introduced all the time and one can expect some breakthroughs in fundamental knowledge to emerge from them soon.

The rest of my research time is now being spent in developing Web-based atlases of brain structure and connectivity at high resolution for the neuroscience community, visible at http://www.brainmaps.org. In these, which cover many species, mammalian and nonmammalian, but with a special focus on monkeys, serially sectioned brains are presented at a resolution matching that obtainable with the best microscopes and zoomable in real time from low magnification to one in which individual neurons can be visualized at a resolution of 0.4 microns per pixel. We are continuing to add to this extensive database, notably in collaboration with Harvey Karten, one of the most broadly knowledgeable neuroanatomists that I know, and are slowing bringing to it the serially sectioned brains of monkeys in which anatomical tracers have been injected into functional areas of the cerebral cortex. In these, scientists can determine for themselves patterns of connections and reinterpret older descriptions made with less satisfactory techniques. Because so few connectional studies are being made now, even though it is a time when those on the cerebral cortex can be extremely valuable for interpreting the results of functional imaging studies, it seems important to make this kind of material widely available. Unfortunately, only a relatively small number of experimental brains can be provided. It is a pity that the slide collections of the older generation of connectional neuroanatomists have never been archived in accessible form. Sadly, when most old neuroanatomists retire, their slide collections are consigned to the nearest dumpster. I once offered to retrieve some of the best collections, digitize the sections, and make them available on our Web site. It would have required some resources of course but when I made overtures to NIH about it providing those resources, my approach met with studied indifference.

Looking Back

Over the years, as a reader will have seen, I have had the privilege of being able to pursue many different avenues of personal scientific interest. I have never felt constrained by any particular experimental model, brain area or technique. One of the most flattering remarks made about me in one of those tedious reviews that we in the University of California must routinely subject ourselves to was: “He’s the last person left who can work on any part of the brain.” I am not sure that that is entirely true anymore but it once was, probably because of all that teaching that I had had to do early on in all areas of anatomy. I have even managed to produce papers on the hippocampus, that structure that so puzzled me when I was starting out and trying to read Tom Powell’s papers. In casting such a wide net as I have, I hope that I have made some small contributions to fundamental knowledge and that I have given value to those agencies, public and private, that have had the confidence to provide me with the funding necessary to pursue my multifaceted research career. I could not have done any of this without the help of a succession of students and postdoctoral colleagues, many of whom I have attempted to name in the foregoing, nor without the dedicated and expert assistance of a number of skilled technicians, particularly Bertha McClure in St. Louis and Phong Nguyen in California. Most of all, I could not have done it in the absence of the understanding support of a devoted wife and family, which now includes three growing grandchildren.

Do I regret the path not taken, the one that might have led me to a career in literature or the classics? Not a bit. That English teacher of so many years ago was right: I have had unparalleled opportunities to pursue many areas of personal interest both inside and outside the field of science. But the second edition of The Thalamus does commence with Ovid and end with Euripides. And it is the Times Literary Supplement that, in the face of Sue’s complaints, I read at the breakfast table, not Science or Nature.

Selected Bibliography

Agmon A, Yang LT, O’Dowd DK, Jones EG. Organized growth of thalamocortical axons from the deep tier of terminations into layer IV of developing mouse barrel cortex. J Neurosci 1993;13:5365–5382.

Akbarian S, Kim JJ, Potkin SG, Hagman JO, Tafazzoli A, Bunney WE, Jr., Jones EG. Gene expression for glutamic acid decarboxylase is reduced without loss of neurons in prefrontal cortex of schizophrenics. Arch Gen Psychiatry 1995;52:258–266.

Asanuma C, Thach WT, Jones EG. Distribution of cerebellar terminations and their relation to other afferent terminations in the ventral lateral thalamic region of the monkey. Brain Res Rev 1983;286:237–265.

Benson DL, Isackson PJ, Gall CM, Jones EG. Differential effects of monocular deprivation on glutamic acid decarboxylase and type II calcium-calmodulin-dependent protein kinase gene expression in the adult monkey visual cortex. J Neurosci 1991;11:31–47.

Benson DL, Isackson PJ, Hendry SH, Jones EG. Differential gene expression for glutamic acid decarboxylase and type II calcium-calmodulin-dependent protein kinase in basal ganglia, thalamus, and hypothalamus of the monkey. J Neurosci 1991;11:1540–1564.

Benson DL, Huntsman MM, Jones EG. Activity dependent changes in GAD and preprotachykinin mRNAs in visual cortex of adult monkeys. Cerebral Cortex 1994;4:40–51.

Berman AL, Jones EG. The Thalamus and Basal Telencephalon of the Cat. A Cytoarchitectonic Atlas with Stereotaxic Coordinates. Madison, University of Wisconsin Press, 1982.

Burton H, Jones EG. The posterior thalamic region and its cortical projection in New World and Old World monkeys. J Comp Neurol 1976;168:249–301.

Choudary PV, Molnar M, Evans SJ, Tomita H, Li JZ, Vawter MP, Myers RM, Bunney WE, Jr., Akil H, Watson SJ, Jones EG. Altered cortical glutamatergic and GABAergic signal transmission with glial involvement in depression. Proc Natl Acad Sci USA 2005;102:15653–15658.

Crick F, & Jones EG. The backwardness of human neuroanatomy. Nature 1993;361:109.

DeFelipe J, Jones EG. Cajal on the Cerebral Cortex. An Annotated Translation of the Complete Writings. New York, Oxford University Press, 1988.

DeFelipe J, Hendry SH, Jones EG. Visualization of chandelier cell axons by parvalbumin immunoreactivity in monkey cerebral cortex. Proc Natl Acad Sci USA 1989;86:2093–2097.

DeFelipe J, Hendry SH, Hashikawa T, Molinari M, Jones EG. A microcolumnar structure of monkey cerebral cortex revealed by immunocytochemical studies of double bouquet cell axons. Neuroscience 1990;37:655–673.

DeFelipe J, Jones EG. Cajal’s Degeneration and Regeneration of the Nervous System. New York, Oxford University Press, 1991.

DeFelipe J, Jones EG. Santiago Ramón y Cajal and methods in neurohistology. Trends Neurosci 1992;15:237–246.

Diamond IT, Jones EG, Powell TP. The projection of the auditory cortex upon the diencephalon and brain stem in the cat. Brain Res 1969;15:305–340.

Evans SJ, Choudary PV, Neal CR, Li JZ, Vawter MP, Tomita H, Lopez JF, Thompson RC, Meng F, Stead JD, Walsh DM, Myers RM, Bunney WE, Watson SJ, Jones EG, Akil H. Dysregulation of the fibroblast growth factor system in major depression. Proc Natl Acad Sci USA 2004;101:15506–15511.

Garey LJ, Jones EG, Powell TPS. Interrelationships of striate and extrastriate cortex with the primary relay sites of the visual pathway. J Neurol Neurosurg Psychiat 1968;31:135–157.

Golshani P, Liu XB, Jones EG. Differences in quantal amplitude reflect GluR4-subunit number at corticothalamic synapses on two populations of thalamic neurons. Proc Natl Acad Sci USA 2001;98:4172–4177.

Graziano A, Jones EG. Widespread thalamic terminations of fibers arising in the superficial medullary dorsal horn of monkeys and their relation to calbindin immunoreactivity. J Neurosci 2004;4:248–256.

Hashikawa T, Rausell E, Molinari M, Jones EG. Parvalbumin- and calbindin-containing neurons in the monkey medial geniculate complex: differential distribution and cortical layer specific projections. Brain Res 199;544:335–341.

Hayes SG, Murray KD, Jones EG. Two epochs in the development of gamma-aminobutyric acidergic neurons in the ferret thalamus. J Comp Neurol 2003; 463:45–65.

Heath CJ, Jones EG. Interhemispheric pathways in the absence of a corpus callosum. An experimental study of commissural connexions in the marsupial phalanger. J Anat 1971;109:253–270.

Heath CJ, Jones EG. The anatomical organization of the suprasylvian gyrus of the cat. Ergeb Anat Entwicklungs 1971;45:3–64.

Hendry SHC, Hockfield S, Jones EG, McKay R. Monoclonal antibody that identifies subsets of neurons in the central visual system of monkey and cat. Nature 1984;307:267–269.

Hendry SHC, Jones EG, DeFelipe J, Schmechel D, Brandon C, Emson PC. Neuropeptide-containing neurons of the cerebral cortex are also GABAergic. Proc Natl Acad Sci USA 1984;81:6526–6530.

Hendry SHC, Jones EG, Emson PC. Morphology, distribution, and synaptic relations of somatostatin- and neuropeptide Y-immunoreactive neurons in rat and monkey neocortex. J Neurosci 1984;4:2497–2517.

Hendry SHC, Jones EG. Reduction in number of immunostained GABAergic neurones in deprived-eye dominance columns of monkey area 17. Nature 1986;320:750–753.

Hendry SHC, Schwark HD, Jones EG, Yan J. Numbers and proportions of GABA-immunoreactive neurons in different areas of monkey cerebral cortex. J Neurosci 1987;7:1503–1519.

Hendry SHC, Jones EG. Activity-dependent regulation of GABA expression in the visual cortex of adult monkeys. Neuron 1988;1:701–712.

Hendry SHC, Jones EG, Emson PC, Lawson DE, Heizmann CW, Streit P. Two classes of cortical GABA neurons defined by differential calcium binding protein immunoreactivities. Exp Brain Res 1989;76:467–472.

Hirai T, Schwark HD, Yen CT, Honda CN, Jones EG. Morphology of physiologically characterized medial lemniscal axons terminating in cat ventral posterior thalamic nucleus. J Neurophysiol 1988;60:1439–1459.

Hirai T, Jones EG. A new parcellation of the human thalamus on the basis of histochemical staining. Brain Res Rev 1989;14:1–34.

Huntley GW, Jones EG. Relationship of intrinsic connections to forelimb movement representations in monkey motor cortex: a correlative anatomic and physiological study. J Neurophysiol 1991;66:390–413.

Huntsman MM, Isackson PJ, Jones EG. Lamina-specific expression and activity-dependent regulation of seven GABAA receptor subunit mRNAs in monkey visual cortex. J Neurosci 1994;14:2236–2259.

Huntsman MM, Leggio MG, Jones EG. Nucleus-specific expression of GABA(A) receptor subunit mRNAs in monkey thalamus. J Neurosci 1996;16:3571–3589.

Jones EG. Familial gastric cancer. N Z Med J 1964;63:287–296.

Jones EG. Pattern of cortical and thalamic connexions of the somatic sensory cortex. Nature 1967;216:704–705.

Jones EG, Powell TPS. The commissural connexions of the somatic sensory cortex in the cat. J Anat 1968;103:433–455.

Jones EG, Powell TPS. The ipsilateral cortical connexions of the somatic sensory areas in the cat. Brain Res 1968;9:71–94.

Jones EG, Powell TPS. The projection of the somatic sensory cortex upon the thalamus in the cat. Brain Res 1968;10:369–391.

Jones EG, Powell TPS. The cortical projection of the ventroposterior nucleus of the thalamus in the cat. Brain Res 1969;13:298–318.

Jones EG, Powell TPS. Electron microscopy of synaptic glomeruli in the thalamic relay nuclei of the cat. Proc R Soc Lond B 1969;172:153–171.

Jones EG, Powell TPS. An electron microscopic study of the mode of termination of cortico-thalamic fibres within the sensory relay nuclei of the thalamus. Proc R Soc Lond B 1969;172:173–185.

Jones EG, Powell TPS. Synapses on the axon hillocks and initial segments of pyramidal cell axons in the cerebral cortex. J Cell Sci 1969;5:495–507.

Jones EG, Powell TPS. Morphological variations in the dendritic spines of the neocortex. J Cell Sci 1969;5:509–529.

Jones EG, Powell TPS. Connexions of the somatic sensory cortex of the rhesus monkey. I. Ipsilateral cortical connexions. Brain 1969;92:477–502.

Jones EG, Powell TPS. Connexions of the somatic sensory cortex of the rhesus monkey. II. Contralateral cortical connexions. Brain 1969;92:717–730.

Jones EG, Powell TPS. Connexions of the somatic sensory cortex of the rhesus monkey. III. Thalamic connexions. Brain 1970;93:37–56.

Jones EG, Powell TPS. Electron microscopy of the somatic sensory cortex of the cat. Parts 1–5. Philos Trans R Soc Lond B 1970;257:1–11; 13–21; 23–28; 29–43; 45–62.

Jones EG, Powell TPS. An anatomical study of converging sensory pathways within the cerebral cortex of the monkey. Brain 1970;93:793–820.

Jones EG. The development of the “muscular sense” concept during the nineteenth century and the work of H. Charlton Bastian. J Hist Med Allied Sci 1972;27: 298–311.

Jones EG, Leavitt RY. Retrograde axonal transport and the demonstration of nonspecific projections to the cerebral cortex and striatum from thalamic intralaminar nuclei in the rat, cat and monkey. J Comp Neurol 1974;154:349–377.

Jones EG. Varieties and distribution of non-pyramidal cells in the somatic sensory cortex of the squirrel monkey. J Comp Neurol 1975;160:205–267.

Jones EG. Some aspects of the organization of the thalamic reticular complex. J Comp Neurol 1975;162:285–308.

Jones EG, Burton H, Porter R. Commissural and cortico-cortical “columns” in the somatic sensory cortex of primates. Science 1975;190:572–574.

Jones EG, Hartman BK. Recent advances in neuroanatomical methodology. Annu Rev Neurosci 1978;1:215–296.

Jones EG, Friedman DP. Projection pattern of functional components of thalamic ventrobasal complex on monkey somatosensory cortex. J Neurophysiol 1982;48:521–544.

Jones EG, Friedman DP, Hendry SHC Thalamic basis of place- and modality-specific columns in monkey somatosensory cortex: a correlative anatomical and physiological study. J Neurophysiol 1982;48:545–568.

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Jones EG. GABAergic neurons and their role in cortical plasticity in primates. Cereb Cortex 1993;3:361–372.

Jones EG. Santiago Ramón y Cajal and the Croonian Lecture, March 1894. Trends Neurosci 1994;17:190–192.

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Jones EG. Cortical development and thalamic pathology in schizophrenia. Schizophrenia Bull 1997;23:483–502.

Jones EG, Dell’Anna ME, Molinari M, Rausell E, Hashikawa T. Subdivisions of macaque monkey auditory cortex revealed by calcium-binding protein immunoreactivity. J Comp Neurol 1995;362:153–170.

Jones EG, Manger PR, Woods TM. Maintenance of a somatotopic cortical map in the face of diminishing thalamocortical inputs. Proc Natl Acad Sci USA 1997;94:11003–11007.

Jones EG, Pons TP. Thalamic and brainstem contributions to large-scale plasticity of primate somatosensory cortex. Science 1998;282:1121–1125.

Jones EG. Making brain connections: neuroanatomy and the work of TPS Powell, 1923–1996. Annu Rev Neurosci 1999;22:49–103.

Jones EG. Cortical and subcortical contributions to activity-dependent plasticity in primate somatosensory cortex. Annu Rev Neurosci 2000;23:1–37.

Jones EG. The thalamic matrix and thalamocortical synchrony. Trends Neurosci 2001;24:595–601.

Jones EG. William Maxwell Cowan 1931–2002. Nature Med 2002;8:911.

Jones EG, Woods TM, Manger PR. Adaptive responses of monkey somatosensory cortex to peripheral and central deafferentation. Neuroscience 2002;111:775–797.

Jones EG, Rubenstein JLR. Expression of regulatory genes during differentiation of thalamic nuclei in mouse and monkey. J Comp Neurol 2004;477:55–80.

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Jones EG. Calcium channels in higher-level brain function. Proc Natl Acad Sci USA 2007;104:17903–17904.

Jones EG. Brain maps and modern phrenology. Brain 2008;131:2227–2233.

Jones EG. The Thalamus, Second Edition. Cambridge, Cambridge University Press, 2010.

Kosaki H, Hashikawa T, He J, Jones EG. Tonotopic organization of auditory cortical fields delineated by parvalbumin immunoreactivity in macaque monkeys. J Comp Neurol 1997;386:304–316.

Lenz F, Casey FL, Jones EG, Willis WD. The Human Pain System. Experimental and Clinical Perspectives. Cambridge, Cambridge University Press, 2010.

Li JZ, Vawter MP, Walsh DM, Tomita H, Evans SJ, Choudary PV, Lopez JF, Avelar A, Shokoohi V, Chung T, Mesarwi O, Jones EG, Watson SJ, Akil H, Bunney WE, Jr., Myers RM. Systematic changes in gene expression in postmortem human brains associated with tissue pH and terminal medical conditions. Hum Mol Genet 2004;13:609–616.

Liang F, Jones EG. Differential and time-dependent changes in gene expression for zif268, CaM kinase II, GAD, NMDA and AMPA receptor subunits in tetanus toxin-induced focal epilepsy. J Neurosci 1997;17:2168–2180.

Liu XB, Honda CN, Jones EG. Distribution of four types of synapse on physiologically identified relay neurons in the ventral posterior thalamic nucleus of the cat. J Comp Neurol 1995;352:69–91.

Liu XB, Warren RA, Jones EG. Synaptic distribution of afferents from reticular nucleus in ventroposterior nucleus of cat thalamus. J Comp Neurol 1995;352:187–202.

Liu XB, Jones EG. Localization of alpha type II calcium calmodulin-dependent protein kinase at glutamatergic but not gamma-aminobutyric acid (GABAergic) synapses in thalamus and cerebral cortex. Proc Natl Acad Sci USA 1996;93:7332–7336.

Liu XB, Jones EG. Predominance of corticothalamic synaptic inputs to thalamic reticular nucleus neurons in the rat. J Comp Neurol 1999;414:67–79.

Liu X-B, Coble J, van Luijtelaar G, Jones EG. Reticular nucleus-specific changes in 3 subunit protein at GABA synapses in genetically epilepsy-prone rats. Proc Natl Acad Sci USA 2007;104:12512–12517.

Macchi G, Jones EG. Toward an agreement on terminology of nuclear and subnuclear divisions of the motor thalamus. J Neurosurg 1997;86:670–685.

Manger PR, Woods TM, Jones EG. Representation of the face and intraoral structures in area 3b of the squirrel monkey (Saimiri sciureus) somatosensory cortex, with special reference to the ipsilateral representation. J Comp Neurol 1995;362:597–607.

Manger PR, Woods TM, Jones EG. Plasticity of the somatosensory cortical map in macaque monkeys after chronic partial amputation of a digit. Proc R Soc Lond B 1996;263:933–939.

Mikula S, Trotts I, Stone JM, Jones EG. Internet-enabled high-resolution brain mapping and virtual microscopy. Neuroimage 2007;35:9–15.

Molinari M, Dell’Anna ME, Rausell E, Leggio MG, Hashikawa T, Jones EG. Auditory thalamocortical pathways defined in monkeys by calcium-binding protein immunoreactivity. J Comp Neurol 1995;362:171–194.

Muñoz A, Huntsman MM, Jones EG. GABA(B) receptor gene expression in monkey thalamus. J Comp Neurol 1998;394:118–126.

Murray KD, Choudary PV, Jones EG. Nucleus- and cell-specific gene expression in monkey thalamus. Proc Natl Acad Sci USA 2007;104:1989–1994.

Ojima H, Honda CN, Jones EG. Characteristics of intracellularly injected infragranular pyramidal neurons in cat primary auditory cortex. Cereb Cortex 1992;2: 197–216.

Peters A, Jones EG (Eds) Cerebral Cortex, Volumes 1–14. New York, Plenum Press, 1984–1999.

Popken GJ, Bunney WE, Jr., Potkin SG, Jones EG. Subnucleus-specific loss of neurons in medial thalamus of schizophrenics. Proc Natl Acad Sci USA 2000;97: 9276–9280.

Rausell E, Bae CS, Viñuela A, Huntley GW, Jones EG. Calbindin and parvalbumin cells in monkey VPL thalamic nucleus: distribution, laminar cortical projections, and relations to spinothalamic terminations. J Neurosci 1992;12: 4088–4111.

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Steriade M, Jones EG, McCormick DL. Thalamus. Volumes 1 and 2. New York, Elsevier, 1997.

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Yen CT, Conley M, Jones EG. Morphological and functional types of neurons in cat ventral posterior thalamic nucleus. J Neurosci 1985;5:1316–1338.

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Krešimir Krnjević

BORN:

Zagreb, Croatia (Yugoslavia)

September 7, 1927

EDUCATION:

Edinburgh University, M.B., Ch.B. (1949)

Edinburgh University, B.Sc. (Hons) (1951)

Edinburgh University, Ph.D. (1953)

APPOINTMENTS:

Postdoctoral fellow,and Assistant Professor, University of Washington (1954–1956)

Postdoctoral fellow, Australian National University (1956–1958)

Principal, then Senior Principal Scientific Officer, Babraham Institute, Cambridge, UK (1959–1964)

Visiting Professor, Physiology Department, McGill University, Montréal (1964–1965)

Director, Anaesthesia Research Department, McGill University (1965–1999)

Chairman, Department of Physiology, McGill University (1978–1987)

Joseph Morley Drake Professor of Physiology, McGill University (1978–2001)

Emeritus Professor of Physiology, McGill University (2001–present)

HONORS AND AWARDS (SELECTED):

Beit Memorial Fellow (1952–1954)

Chief Editor: Canadian Journal of Physiology and Pharmacology (1972–1978)

Fellow Royal Society of Canada (1975)

Alexander Forbes Lecturer Marine Biology Labs, Woods Hole, Mass. (1978)

President Canadian Physiological Society (1979)

Council Member, International Union of Physiological Sciences (IUPS) (1983–1993)

Honorary Member, Croatian Pharmacological Association (1983)

Gairdner International Award (1984)

Officer of the Order of Canada (1987)

Jasper Lecturer Canadian Association for Neuroscience (1989)

Honorary President, Almae Matris Croaticae Alumni, Québec (1990-present)

Corresponding Member, Croatian Academy of Arts & Sciences (1992)

Wilder Penfield Prize, Government of Québec (1997)

Kershman Lecturer, Eastern EEG Association (1998)

Spiridion Brusina Prize, Croatian Natural Science Association (2001)

Krešimir Krnjević was a pioneer in the identification of brain neurotransmitters, notably such previously unsuspected endogenous amino acids as glutamate for excitation and GABA for inhibition, and a slow muscarinic excitation by acetylcholine (ACh). Also in showing that cholinergic fibers to cortex originate from the basal forebrain; and that ACh enhances cortical activity by reducing K conductance (GK), an unprecedented mechanism of modulation, which could be counteracted by an equally novel hyperpolarizing action of cytoplasmic Ca ions, mediated by increased GK. Resulting opposite shifts in cortical activity were proposed as possible mechanisms of consciousness and anesthesia.

Krešimir Krnjević

The Past Is a Foreign Country*

For me, this is both metaphorically and literally true: though I was born in Croatia, most of my life I have resided elsewhere. Albeit far from unique— numerous thousands of Europeans of the pre–World War II generations were uprooted—my situation had its own special features, which governed the course of my life and scientific career. In a sense, I was a precursor. Most of the millions who were “displaced” during that disastrous first half-century moved after 1933 when the Nazis got into power in Germany. My first exile began earlier, in 1930, when, as an infant, I was smuggled out of Yugoslavia.

My father, Juraj, was a great patriot, who devoted his life to his Croatian people and the Croatian Peasant Party—founded by an inspiring leader, Stjepan Radić, whose teaching he never ceased to promote through many decades of exile. As a child, I saw my father as a stern and demanding figure; but later, he earned my unqualified love and respect for his outstanding qualities: a strong will, tempered by an open mind and unselfish integrity, and total lack of interest in money. My doting mother, Nada, was an unending source of love and tenderness. She had a sunny and affectionate nature, as well as boundless energy, only partly expended in skiing and mountain climbing in neighboring Savoie (including Mont-Blanc). From my parents, I inherited both energy and optimism, which have served me well throughout my life.

I was born in Zagreb on September 7, 1927. By 1930, after the assassination of Stjepan Radić in the parliament in Belgrade and the advent of King Alexander’s dictatorship, some leaders of the now outlawed Croatian Peasant Party (including my father) left the country. They wanted to convince major European powers of the need to restore democracy in Yugoslavia. So he went to Geneva, the seat of the League of Nations (the prewar equivalent of the United Nations). At the age of 2½, I was taken by my aunts from Zagreb to the Italian border—then at Rijeka—across which I ran, unhindered by the border guards, to my mother, waiting for me on the other side. We lived in Geneva for the next 10 years, and there I had my first education, up to the end of primary school. At home my parents always talked to us in Croatian, but my sister Biserka (5 years older) and I grew up speaking French. This remained our standard language of communication, long after we’d left Geneva.

Even in Switzerland, life was far from easy for a political exile: with so many unemployed during those depression years, we were allowed to stay in Geneva on the condition that my father take up no gainful employment. But access to the lake or mountains was free. My parents were enthusiastic hikers. So every Sunday, we all walked 3 miles to the French border and then up the 4000-foot-high Mt. Salève. As a child, I had mixed feelings about the obligatory Sunday hike, but I grew to love mountains. We led a very quiet life and my schooling was uneventful. Summers I spent at an inexpensive holiday camp, run by our Catholic parish; neither father nor mother went to church, but I attended the catechism classes every Saturday. The Swiss phase of my life, generally calm and happy, like that blessed country, ended just as the European war was about to start. Alarmed by the quickly deteriorating European situation, in the summer of 1939 the Belgrade government reluctantly granted Croatia a near-autonomous status as the Croatian Banovina. We could now return to Zagreb. Having to leave Geneva and my friends was hard enough for me: far more upsetting was leaving my mother behind. My parents’ separation (and ultimate divorce) was the deepest psychological trauma of my childhood.

Our arrival in Zagreb, on September 1, was an astounding event. At the railway station, the returning exile was welcomed by thousands—an occasion for many bouquets, speeches, and ovations, all in amazing contrast to our very quiet life in Geneva. We also discovered a large family of numerous uncles, aunts, and cousins, all making us feel warmly welcome. But at school, the early weeks were stressful, my rudimentary spoken Croatian being of little help when trying to cope with a rich and complex grammar. Within a few months, however, my sister and I were settling in this new, privileged existence. Though we missed Geneva’s lake and mountains, Croatia offered an admirable, largely unspoiled, long Adriatic coast and islands, perhaps the finest in Europe. Sometimes I wonder, how different would my life have been if we had remained there? Would I have become an engineer, my greatest wish at the time? More likely, we would not have survived the takeover of Croatia by the Ustashi (extreme nationalists) after the German invasion of April 1941. As a prominent politician, strongly favoring the Western Allies, my father (and his children) would be early targets for liquidation. As it was, a bomb thrown into our house by Ustashi in December 1940 blew up within a few feet of me. I was seriously shaken but physically unharmed.

Another page was turned as we again went into exile in April 1941. When the German army invaded the country, my father agreed to be the Croatian vice-premier in the new Yugoslav government, getting ready to leave for Greece. A long and hazardous drive took us to Sarajevo (where I first experienced aerial bombing by the much feared Stukas); then over the mountains of Bosnia and Hercegovina to Nikšić in Montenegro. Nikšić had an airfield from which we were to fly to Athens. Though we had to hug uncomfortably close to the Albanian mountains to avoid Italian fighters, our flight—in a bomber of the Yugoslav air force—should have been straightforward; it was cut short when, needing to refuel, we crash landed at a British air base in Agrinion, in northern Greece. Our luck held: albeit shaken, we were unhurt; but the journey had to continue overland, very slowly, first to Patras and then Athens. After the intense cold and snow-covered mountains of Bosnia and Albania, we marveled at the warmth and the blossoming orange trees in the streets of still peaceful Athens—the Germans were yet to reach Greece. A few days later, a slow flight took us from the Pireus to Crete, Alexandria, and then Cairo, where the unwelcoming Egyptian authorities immediately sent us off by the night train to Port Said, in the British-controlled Canal Zone. Our stay there, for a week or so, was followed by a long train ride to Jerusalem, where the Yugoslav government-in-exile finally reconvened, in an old monastery on the road to Bethlehem. In spite of the war and other hazards in Palestine, there was much to enthrall a young boy. Visiting the Holy sights or floating in the Dead Sea; and later, back in Cairo, riding a camel and climbing the great pyramids (as one could in those days) seemed like a great adventure.

But then, Biserka and I had to part from our father. Only the most senior members of the government could be flown to England; so all the other Yugoslavs went to Suez, to board the Strathaird, about to sail for South Africa. After a pleasant 2-week journey, we reached Capetown, where boarding schools were found for Biserka and myself. Thus began my third “incarnation” (as it were), now in the English-speaking world. Thanks to rapid progress, I finished my accelerated high school education before the end of 1943: with a very mixed bag of knowledge—in history for example, where 17th-century Dutch Cape settlers floated above medieval Croatian kings and an even deeper layer featuring William Tell’s crossbow and apple. Apart from my introduction to English, that school’s most significant and lasting impact was in the realm of music, for which I must thank a wonderfully empathic teacher, Valerie Norman, whose infectious enthusiasm and inspiring approach to piano playing aroused a passion for music that has never flagged. Life in Capetown was an interlude of peace and comfort. White people were privileged in South Africa, especially in Cape Province, with its temperate climate, rugged mountains, and splendid beaches: they enjoyed a high standard of living based, of course, on a shameless exploitation of the black majority. The few who thought about it seriously knew this could not go on forever. But most people accepted it as a gift from heaven. In any case, surely it would outlast their lives. . . .

Early in 1944, we left for England. Our mainly cargo boat (SS Sarpedon) reached Freetown (in Sierra Leone) without hindrance from the U-boats infesting the approaches to the Cape of Good Hope. We continued on to Liverpool, traveling very slowly but more safely in the middle of a large convoy.

Altogether, the voyage lasted 6 weeks. Nowadays, this would seem absurdly long and, surely, excessively boring. Not so. A surprisingly well-stocked library was available (where I first came across the Origin of the Species). Free to roam about the ship, I always had something to do or look at: the never-ending play of sun (or moon)-light on waves, the flying fish; at night the fluorescent spray and the ghostly sight of other ships gliding silently alongside. All males took turns at watching for enemy aircraft; and everyone attended the frequent lifeboat drills.

Arriving in a much battered Liverpool felt as if we were landing on another planet. The cold damp weather of early spring, the bomb-blasted ruins all about the landing area and Queen Street station, and the lean undernourished look of the local people could hardly present a greater contrast to the Land of Cockaigne we had left behind in Southern Africa. The train ride to London was interrupted several times by a vicious air raid, one of the last of the “conventional” bombardments. In London, we were issued gas masks, as well as coupons for food and clothing that were strictly rationed, and from then on, whenever I traveled anywhere in Britain, I had to report to the police at a backdoor entrance prominently labeled “Aliens, Firearms, and Dangerous Drugs.”

As a child, I wanted to become an engineer. By this time, however, my interests had broadened: indeed, everything seemed exciting. But my father, remembering my long interest in engineering, had made arrangements to see people at a Cambridge college, Peterhouse. Not long after our arrival, we all went to Cambridge. It was agreed that Biserka—who had finished 1 year of university in Capetown—would go to Newnham, a college for women. Having no Latin—at that time an absolute requirement for admission to Cambridge—and being rather young (16), I was advised to learn some Latin and return the following year. To wait a whole year seemed to me a dreadful imposition. Instead, I opted for medical studies in Edinburgh, where the separate Scottish system had no Latin requirement for admission. After some additional coaching in chemistry and physics during the summer, I passed the first MB exam in the autumn and began my medical studies in October 1944.

Though far from secure—those marvels of the latest German technology, the V1 and V2 bombs kept up round-the-clock suspense—life in London was amazingly rich in cultural events, in spite of wartime restrictions. That summer, I seldom missed any of the lunch-hour concerts at the National Gallery. There was plenty more chamber music at the Wigmore Hall. And, after the concerts, as soon as some paintings returned to 2-3 undamaged rooms at the National Gallery, visual arts came as another revelation. Because they were so few, one could get to know the pictures really well, undistracted by the thought of dozens more rooms to visit. My father had rented a house in Chelsea—during the war, plenty were available and inexpensive—so I had a base from which to explore London, to which I was to return regularly during vacations.

Life in Edinburgh was rather different. Getting away from the V1’s and V2’s was a relief, but there was a sobering dourness about the city. Long before the festivals ushered in a cultural renaissance, there was little in the way of music, modern art, or theater, and no cinemas were open on Sundays. On the other hand, the town was always there, offering a wonderful variety of stone buildings and entrancing prospects. Throughout the 10 years that I spent in Edinburgh, I never tired of exploring the crooked streets below the Castle and the classically laid-out squares and crescents of the New Town. Edinburgh is an extraordinary architectural success—surely the loveliest city in Britain, and among the finest in Europe.

The first 2 years of our studies were mainly devoted to anatomy: especially the systematic dissection of the human cadaver to which I was assigned, together with 4–5 other students. Our focus was sharpened by frequent “spot” exams: what sequence of many structures would be penetrated by a needle inserted at this or that point? We were kept on our toes also by the frequent appearance of the already venerable E. B. Jamieson—the grand old man of Edinburgh anatomy—who, wearing a little black cap, shuffled about the dissecting room, asking pointed questions. By contrast, physiology was much harder to grasp. Unlike anatomy, it seemed to lack firmly established facts. The physiology teachers failed to inspire much enthusiasm, and they had some difficulty in controlling a very unruly crowd of young students, only recently freed from school discipline.

The clinical subjects, and especially regular exposure to patients, soon had a sobering effect. Unlike any other, medical training offers an accelerated schooling in life and many of its problems, as well as an exceptional variety of highly regarded and monetarily well-rewarded employment. Though I worked quite seriously, much time went into exploring music, including moderately successful attempts at playing the piano. Mozart was a particular favorite. In view of Mozart’s prodigious output, Sacheverell Sitwell (1936) had commented that no one could hope to hear even half the works listed in Köchel’s catalogue. This spurred me to listen to every (for me) new piece by Mozart, played mostly on the BBC’s Third Programme: before I left Edinburgh, I could boast of having crossed out over two-thirds of the 626 items in the catalogue.

I also greatly enjoyed weekend climbing trips, as a member of the University Mountaineering Club, to the Highlands and, less often, the Lake District—the rudiments of rock climbing I’d picked up during summer visits to my mother in Geneva (from my step-father, Francis Marullaz, a great alpinist, who had conquered at least once every 4000 meter peak in Europe). My studies proceeded satisfactorily to their conclusion in 1949, by which time I was just old enough to become a registered medical practitioner. In those less exacting days, there was no requirement for further hospital experience (internship). So I could have joined some practice or even gone off as a ship’s doctor—as some of my colleagues did. When my closest friends enrolled in residency training, I was at first tempted to continue in a clinical career but then decided that I would concentrate on research.

Why did I make that choice? I enjoyed working with patients. That part of medicine very much appealed to me. What I did not like so much was the medical hierarchy, the deference to the established chiefs, having to conform to certain patterns of behavior and accepting the power games involved in climbing up the professional ladder. By contrast, in research I could contribute to new knowledge as a member of a relatively small, but worldwide community of scholars. This was better suited to my temperament, as well as my situation: having been uprooted several times from several countries and cultures, I felt a greater natural affinity for a career where one’s performance counted more than one’s provenance. Where could I train as a researcher? I went to the Physiology Department (in Edinburgh) and spoke to Philip Eggleton, the acting Head (to the Eggletons we owe the discovery of phosphocreatine, when both husband and wife were studying muscle metabolism in A. V. Hill’s laboratory at University College). As always, he was very helpful. Though he mentioned the limited number of academic jobs then available, he did not try to discourage me. When he asked what field of research I was interested in, I replied that studies of the brain, especially how to bridge the chasm between brain physiology and psychology, seemed of particular interest. He thought both fields were becoming ripe for serious moves in that direction. As it turned out, we were somewhat overly optimistic. That happened to be the year (1949) when Donald Hebb’s The Organization of Behavior was published (a book now much-cited); only several decades later did neurophysiologists begin to take a serious interest in cognitive processes and most psychologists see the relevance of synaptic events.

Before I could start my Ph.D. research, I had to complete 2 years of an Honors B.Sc. program. Apart from physiology lectures and labs, my other major topic was psychology, taught mainly (and rather effectively) by the head of the department, James Drever. This introduced me to such topics as motivation, learning, gestalt, and statistics that I hadn’t thought about much before. It was a stimulating experience. For a lab project, David Whitteridge—the new Head of Physiology who had just come from Oxford— suggested that I try to record from vagal relay cells inthe cat’s nodose ganglion. He had spent much time recording afferent signals from the lungs and heart, as “unitary” responses in fine strands laboriously dissected from the vagus. Microelectrodes might be a useful alternative. With acid-sharpened sewing needles—insulated except at the tip—I did manage to record some single units from the nodose. Albeit feasible, this method was probably not much less trouble than the alternative, and as far as I know, was not widely adopted. Nevertheless, when written up, this project qualified me for a Goodsir Memorial Bursary.

First Steps in Research

David Whitteridge had been present at the 1948 CNRS conference (in France) at which Hodgkin and Huxley’s ground-breaking analysis of the squid nerve action potential was first presented to an international audience. The notion that Na ions played a crucial role was fiercely challenged by the Spanish-American neurophysiologist Rafael Lorente de Nó, emphasizing that peripheral nerves kept in Na free solutions conducted action potentials for many hours in the absence of any Na ions. In reply to the objection that desheathed nerves rapidly become inexcitable when Na ions are removed, Lorente de Nó contended that such desheathed nerves are not in a physiological state. It occurred to Whitteridge that the issue might be resolved by perfusing the nerve through its blood supply, thus bypassing the sheath. He proposed that I make this the topic of my Ph.D. research.

Before starting experiments, I spent several months putting together electrophysiological equipment. Apart from a Cossor oscilloscope, no commercial equipment was available. So, with cheap army-surplus material— resistors, capacitors, and vacuum tubes—circuits from C. J. Dickinson’s indispensable manual (1949), a soldering iron, and, especially, the inestimable advice of Whitteridge’s electronics technician (“Jock” Austin), even a raw student could produce the needed items in a relatively short time. Perfusing a frog’s leg via the descending aorta posed no major problem. Within a few weeks, Whitteridge’s idea proved correct: action potentials in the sciatic nerve disappeared after only a few minutes of Na-free perfusion. High concentrations of K⁺ also rapidly blocked conduction, whereas uncharged molecules s such as acetone, acted about equally quickly when applied to the intact nerve or by arterial perfusion. Clearly, a lipid-permeable barrier prevented rapid diffusion of ions into or out of the nerve trunk. One possible objection remained. Could perfusion be more effective because a high density of capillaries greatly reduced diffusion distances within the nerve trunk? Indeed, when stained with a dye, the capillary supply proved far richer than might be expected in a simple nerve. Knowing the mean intercapillary distance and the rate of action potential block during perfusion, my calculations showed that faster internal diffusion could not account for the very rapid block seen when nerves were perfused with Na-free solutions. Having only a high-school knowledge of mathematics, I spent a great deal of time over the complex Bessel functions that describe diffusion in cylindrical coordinates. I was somewhat put out when, at my PhD oral, Phillip Eggleton, jotting a few numbers on the proverbial back of an envelope, in few minutes confirmed the general validity of my elaborate calculations—much to Whitteridege’s amusement.

The preparation and results were first presented in a Demonstration at a Physiological Society meeting in Edinburgh (July 1952)—owing to my habitual procrastination, too late to be cited by Hodgkin at the July 1952 Cold Spring Harbor Conference (he had shown interest in my preliminary results, which countered Lorente de Nó’s objections). These findings were published in my first article, in the Journal of Physiology (1954). In a complementary study, I found that the diffusion barrier is probably the perineurium, which forms a continuous layer of epithelium (and not as previously thought the much looser epineuriuim), Indeed, the perineurium seemed analogous to, and possibly of similar origin as, the arachnoid cover of the central nervous system (CNS). These studies were written up for my Ph.D. thesis. The external examiner William Rushton (of Cambridge University), commented that this was not the way he would have tackled the problem but was otherwise quite positive. Thus ended my experiments on frog nerves. But my expertise came in handy some 50 years later, at McGill, when supervising undergraduates measuring conduction velocity in frog sciatic nerves; which I still do this regularly—my only postretirement teaching.

Two other related projects were completed in Edinburgh. One was a follow-up on Na⁺ fluxes out of mammalian nerve trunks, in collaboration with Jack Dainty (of the Biology Department). Having worked during the war as a physicist at the Chalk River Nuclear station in Canada, Dainty was now using radioisotopes to measure ion fluxes from seaweed. Sending the resulting paper to the Journal of Physiology was a salutary experience. It came back with a searching critique, signed by Andrew Huxley, who pointed out that, because extracellular Na⁺ is so abundant, in our calculations we needed to take into account a significant reverse influx of labeled Na⁺. The other project also dealt with effects of Na⁺ deficiency on neural function. For this, I teamed up with two old friends, colleagues from medical school, Peter Aungle (training to becoming a psychiatrist) and Robert Kilpatrick (who went on from internal medicine to the General Medical Council and ultimately the House of Lords). More ambitiously, we now had humans as subjects. We wanted to see whether salt deprivation could lower the concentration of Na⁺ [Na⁺] sufficiently to induce detectable changes in nerve and muscle function. Both our heroic volunteers (who remained good friends, even after their ordeal) put up with a punishing regime of a virtually Na-free diet and regular sessions in a sauna—to maximize Na loss by sweating. Thanks to remarkably effective Na homeostasis, however, plasma [ Na⁺] dropped only minimally (the greatest reduction in one subject was by only 10%), but the large loss of body water resulted in a substantial rise in plasma [K⁺] and, even more alarmingly, in blood viscosity. A battery of tests of nerve and muscle function—including central reaction time and electroencephalogram (EEG)—showed no significant changes except, in the subject with the largest drop in plasma [Na], a significantly longer nerve refractory period. A dramatic highlight of these experiments came on the last day: having thoughtlessly taken an anchovy sandwich at a party, our subject had returned for an additional session in the sauna before undergoing the usual intensive tests. Sitting in a chair, in my lab, when the high-frequency nerve stimulation approached its peak, he suddenly collapsed to the floor. For a minute, we thought we had killed him (and deprived his children of a loving father). Very fortunately, he soon recovered. Such brash, minimally safe-guarded experiments could not be done so easily now. There is much to be said for ethics committees.

Following recommendations from Whitteridge and Eggleton, I was awarded a Beit Memorial Fellowship. It was a relief to be no longer in need of any financial help from my father. With no possibility of free political activity under Tito, in spite of the offer of a good pension, he refused to return to Yugoslavia and remained in London. Having no steady income, he lived very modestly in Clapham, writing articles for a Croatian emigrant newspaper in Canada. Ever an optimist, he was convinced that the communist regime would end, sooner or later. For over 40 years, apart from regular visits to Canada, he lived in London, but not quite long enough to see his dream of a free Croatia come true. He died in 1987, aged 92, on the eve of the collapse of the Soviet system.

Departure from Edinburgh

At the 1953 Montreal International Physiological Congress, Whitteridge had been much impressed by scientists from Seattle. Albeit loath to leave Edinburgh, acting on his advice that I would benefit from exposure to a different research environment, I wrote to Ted Ruch, head of Physiology and Biophysics at the new medical school in Seattle. With the dynamic Vahé Amassian (a Cambridge and Middlesex graduate) already on his staff, Yale- and Oxford-trained Ruch thought highly of British education. He offered me a position as Assistant Professor. After spending a full decade in Edinburgh, before leaving for Seattle in September 1954, there were many things to settle. Foremost was getting married to Jeanne, at the Dominican chapel in George Square. Jeanne Bowyer had a checkered history, somewhat like mine. Born in Penang, Malaya, of an English physician and an Irish mother, she went to school in Scotland. In December 1941, with mother and sister, she had to flee Singapore as Japanese troops moved rapidly down the Malaysian peninsula. Their Dutch ship took them to Batavia and then Sydney, where they stayed several years. When she’d completed her schooling, they traveled to Durban, to join other members of her father’s family, resident in Natal. Meanwhile her father, who had been superintendant of the main hospital in Singapore, was interned by the Japanese and died as a result of maltreatment. A few years later, Jeanne came to Edinburgh to study social work. After the wedding, we flew to Dublin for a brief honeymoon (and a memorable dinner at Jammet’s). An immigrant visa that would allow Jeanne to work in the United States required a last-minute visit to the consulate in Glasgow (she benefited from her birth in Penang, the subquota for non-Malays from Malaya being undersubscribed). And then we were on our way to London and Southampton, where we boarded the Queen Elizabeth. As the ship was about to sail, I posted my sciatic nerve histology paper to John Passmore, the editor of the Quarterly Journal of Experimental Physiology.

In New York, we were welcomed by my father’s Croatian friend, Bogdan Raditsa (writer and former diplomat, then teaching European history at Fairleigh Dickinson University) and his wife Nina, the daughter of the Italian liberal and antifascist, Gugliermo Ferrero). Once again I felt as if we’d landed on another planet. New York in October was far warmer than it had been at mid-summer in Edinburgh—the strange sight of steam issuing from manhole covers made the heat seem even more oppressive. But the highlight of our first evening was a party at the Hamburgers (Phillip Hamburger was prominent writer for the New Yorker), It was a noisy affair, loud with argumentative New Yorkers going on about the forthcoming November elections. Much was shouted about “Charlie” Wilson’s alleged “What’s good for General Motors is good for the country” and “that bum Bender. . . . ” What could we say when we were asked what people in Scotland thought about the elections. We could only try to be polite, and were probably thought to be rather stupid.

After a brief detour to Washington, to greet old friends from Zagreb, Dr. Maček—the exiled president of the Croatian peasant party and his family, whom I had last seen in March 1941 before driving off to Sarajevo— we boarded the train for Chicago for the first leg of our 4-dayrailway journey to Seattle. The air-conditioned train was welcome after hot and humid Washington, waiting for a tornado that also caused major flooding at Union station in Chicago. Having a few hours to spare before the departure of the train for Seattle, we wandered off along the Lakeshore and into the Art Institute We were thrilled to see, quite unexpectedly, Seurat’s Afternoon at La Grande Jatte, well-known to us from illustrations in R. Wilenski’s splendid book (my introduction to modern art ). Our ‘roomette’ on the Milwaukee Road train provided both comfort and privacy. Spectacular scenery could be viewed from the “scenic dome” or the glass-surrounded end-compartment. Watching the moon reflected in the Mississippi or the moonscape of copper mining at Butte (Montana) was both exciting and disorienting. Not much trace of old Europe here.

At the end of the long transcontinental journey (soon superseded by much faster but far less interesting flying), we were greeted by Vahé Amassian, smoking a fat cigar and driving a large, bright red Oldsmobile convertible— all in sharp contrast to his very English accent and manner (St Paul’s school and Cambridge). We enjoyed his company, but not for long. Though of British nationality, as a single man, at the peak of the Korean War he could not escape the draft. From the station, he drove us to the Meany Hotel (“every room a corner room”!) in the University district, near the University of Washington campus. At the Medical School, we were introduced to Ted Ruch. He had brought to Seattle several colleagues from Yale, as well as the Yale teaching system: once a week, each staff member headed a “discussion” group of 10–12 students, so everyone had to attend all the lectures to be able to deal with all aspects of physiology. Another rule was that no one lectured on a topic related to his or her own research. I was assigned digestion. This was all very sensible, but it was unduly time consuming and certainly very different from physiology teaching in Edinburgh, where all the lectures were given by Whitteridge himself. I wonder how long the Yale system survived as the department’s contingent of dynamic researchers grew by leaps and bounds.

There were other curious features. Before taking up my appointment as assistant professor, I had to sign a statement that I would not take part in activities that might undermine the government of the United States. Each month, when picking up our checks, everyone had to sign a sheet listing all the staff members and their respective salaries—displayed for all to see in the departmental office; this was to ensure that everyone was physically present in the department. The students were neatly dressed and well-behaved, males with crew cuts, girls in skirts and bobby socks; they were attentive in class and often asked questions—quite unlike the rowdy young Scots. The University Bookstore sold mainly T-shirts and sports equipment, with only a few shelves of books on display at the back, mainly standard textbooks. The central role of sports in the life of the university became even more blatant when Robert Oppenheimer—invited to give a series of lectures to the physicists—was refused access to the campus by the president of the university, on the grounds that Oppenheimer had lied to the U.S. government. Everyone (including the city) being passionately involved in the far more important question whether the coach of the poorly performing Huskies should be given the boot, there was little concern on the campus (the football coach was fired by the Board of Regents; but, soon after ran successfully for the position of Vice-Governor of the state of Washington. . .). Such was academic life in the mid-1950s. Of course, student uprisings during the next decade led to radical changes. When I visited Seattle in the 1970s, the students wore tattered jeans, and had long and disheveled hair and beards; several bookstores actually full of books had sprouted, and I felt sure no university president could safely indulge in arbitrary decisions.

Seattle is splendidly situated: between Puget Sound and Lake Washington with mountains ranging on both east and west sides. It was like a return to Geneva, with the added bonus of the beautiful cone of Mt. Rainier glistening in the fall sunshine—though everyone assured us that once the rain began, it would be invisible for 6 months. In some ways, this was better than Switzerland with its overcrowded trails. We hiked or snowshoed—in winter the only way of getting around mountains covered by 30–40 feet of snow. If more than half-mile from the highway, one had the vast expanse of mountain all to oneself. We also skied, at Snoqualmie, Stevens Pass, Mt. Baker, or Mt. Rainier (at Paradise Valley). In these ventures we were often accompanied by friends such as Eric Stein—a biochemist from Geneva, working with another friend, Eddy Fischer (also with a Swiss background)— or Goran Bauer (orthopedic surgeon and bone researcher from Lund) and their wives. During the summer, we swam or sailed on Lake Washington; or tried (unsuccessfully!) to dig for clams on a Pacific beach; and ventured further afield to the Blue Mountains of eastern Oregon. The crowning achievement was to climb Mt. Rainier, leading on my rope Eric Stein and the enterprising Dean of the Medical School, George Agaard—by the regular route, not difficult but a long slog up the snowfields. We duly signed our names in the book kept at the summit near the edge of the crater. A longer drive took us to Montana and Wyoming (including Yellowstone). Another journey, to Canada—to celebrate Christmas with Croatian friends on Vancouver Island—was less successful. At Vancouver airport, the official pointed out that my student visa was good for only one entry to the United States: he’d be happy to let us into Canada, but I would not be able to return to Seattle without getting a new U.S. visa—which usually required at least several weeks. If the cost of the return flight posed a problem, he could have us “deported” from Canada, but this would feature permanently in the official record. Somewhat dejected, we flew back to Seattle on the same plane.

All this activity was not conducive to research. The 2 years in Seattle were the least productive of my career. Ted Ruch’s expectations were disappointed. Working with my own rig, I shared a large lab space with Dexter Easton, who was trying very hard to isolate a single muscle fiber with its innervation intact. He wanted to confirm decisively his belief that muscle action potentials were smaller at the end-plate owing to interference by action potentials in adjacent fibers, rather than shunting of membrane currents by transmitter action—as proposed by Katz and Fatt. Bernard Katz was so incensed that soon after, he wrote a paper for the Journal of Physiology devoted solely to a systematic demolition of Dexter’s thesis.

For my own research, I decided to record from the cat’s cerebral cortex. First, I tried to make intracellular recording easier by eliminating vascular pulsations: the blood supply to the brain was detoured into a glass chamber containing air that would absorb the pulsations before the blood was returned to the carotids. This very bloody procedure, described only in an abstract, yielded a few, not very impressive intracellular recordings. Of greater interest were marked ontogenetic changes in the cortical response evoked by paw stimulation. In very young kittens, the large primary response was reversed, being positive instead of negative as in mature animals. These data, confirmed by later observers, were never submitted for publication.

We Travel across Another Ocean

How did I come to leave Seattle for Canberra? In 1955, Stanley Bennett (head of Anatomy at the University of Washington) organized a symposium on synaptic mechanisms. Bennett and Eduardo de Robertis (in exile from Peron’s regime in Argentina) had recently discovered synaptic vesicles. With Eccles, Frank, Fuortes, Kuffler, Hunt and Lloyd attending, this was a particularly successful event—though it was sad to see David Lloyd so obdurate in refusing to accept Eccles’ new findings about spinal inhibition. Jack Eccles was in top form, presenting also the new data on Renshaw cells and the evidently cholinergic nature of recurrent inhibition. I had met Eccles when he visited Edinburgh, but we got better acquainted in Seattle where gave him some penicillin injections to treat a bad cold. Much impressed by his talks, I was happy to accept his offer of a visiting fellowship. So, in September 1956, we sailed from Vancouver on the Orient line’s Orcades. A thoroughly enjoyable voyage—including delightful 1-day stops in Honolulu, Fiji, and New Zealand—got us to Sydney by early October. We arrived on a Saturday morning, too late to have all the luggage off the ship before all the stevedores departed for the Randwick Park races. We took the train for Canberra on Monday. At Canberra station, we were greeted by Jack Eccles, who drove us to our residence at the Australian National University.

There wasn’t much to Canberra in 1956. After some minutes, I asked our host when we would reach downtown. His reply was: “We’ve just passed it.” The main institution in Canberra was the Parliament. Members of parliament would come for the parliamentary sessions, staying at the only hotel, and return to Sydney or Melbourne as soon as the sessions were over. The Australian Institute for Advanced Studies was the pet project of the Prime Minister, Robert Menzies, who established its statutes and financial basis. It had started only a decade or so earlier. Eccles, who was Australian, had gone to Oxford to work with Sherrington and remained there till the end of the 1930s. He returned to his homeland, to the Kanematsu Institute in Sydney, to which he brought B. Katz and S. Kuffler to form a celebrated team; but then went to New Zealand to become the head of the Physiology Department at Dunedin. His pioneering intracellular findings in spinal motoneurons overturned his long and vehement opposition to chemical transmission, especially at central synapses. For a philosophical underpinning to his conversion, he was much indebted to the Austrian logical positivist Karl Popper—also in Dunedin at that time—who believed that science advances by the refutation of wrong hypotheses. Eccles remained in Dunedin until he was offered the position at the new universityn in Canberra. For the first few years, he and the visiting Paul Fatt worked in temporary huts—by no means unproductively—while the new John Curtin School of Medical Research was being constructed. Soon after our arrival, Ricardo and Mela Miledi also came, from Mexico. As Eccles was busy recording from chromatolysed motoneurons (with Ben Libet), Ricardo and I joined David Curtis in a study of short-latency excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in sacral motoneurons. According to David Lloyd, short-latency contralateral inhibition could be demonstrated in sacral segments even if the inhibitory signal was elicited well after the excitatory one. This he took as clear evidence that the inhibitory pathway was monosynaptic, not disynaptic as postulated by Eccles. Our results were clear. The mean latency of IPSPs was significantly longer, by some 0.75 ms, in keeping with Eccles’ findings in lumbar motoneurons. These experiments were completed within a month or two. At this point, lacking the equipment needed to continue with the spinal cord, Ricardo and I were invited by Bill Liley to use his lab and equipment: he had finished his work on neuromuscular transmission in the diaphragm and was now writing his Ph.D. thesis. Moreover, he showed us how to dissect the phrenic nerve and diaphragm from rats, anesthetized with ether. Invariably, having mounted the preparation in the recording chamber, Bill would sit back, light a cigarette, and, unthinkingly, drop the match into the nearest bucket—into which he had earlier disposed the large wad of ether-soaked cotton-wool. The fireworks were impressive.

Neither Ricardo nor I had worked on the neuromuscular junction. Taking turns at doing experiments, our collaboration proved most enjoyable and productive. Though we worked together for less than a year, it resulted in seven publications. There were several highlights. By stimulating the phrenic nerve after cutting all but one axon, we were able to show (for the first time) that a single motor unit is scattered quite widely over the diaphragm. We obtained direct evidence that failure of neuromuscular transmission can occur presynaptically, probably at points of axonal branching, and that in fatigued muscle, adrenaline exerts its beneficial actions at several, pre- and postsynaptic sites. By careful placement of a microiontophoretic electrode, and releasing only minute amounts of acetylcholine, we could evoke responses comparable in time course to end-plate potentials. Extracurricular adventures included skiing between eucalyptus trees in the Snowy Mountains and a vividly memorable inland excursion via Hunter, Booligal, and Wilcania to Cobar, and then over the Blue Mountains to Sydney and back to Canberra. Owing to the severe shaking induced by endless miles of corrugated tracks, by the time we reached Cobar, my ancient Standard Tourer was coming apart. The radiator was leaking badly, the front wheels had nearly come loose, and the chain brakes were minimally functional. The front axle, held by only one remaining screw, had to be fixed before we left Cobar. The brakes were less of a concern, the landscape being utterly flat and the roads free of traffic most of the way. But we had some narrow escapes when we had to cross the Blue Mountains and later, near Sydney, at intersections with traffic lights. Sleeping out under the wonderfully starry Australian sky and seeing clouds of budgerigars, parrots, and cockatoos, as well as many small and large lizards, emus, and of course kangaroos, more than made up for the hazards.

During the second year in Canberra, apart from some experiments on salivary glands with Anders Lundberg, I worked mainly with Eccles on intra-axonal recordings of dorsal root potentials. Several components of these large responses had been reported by various authors, including Matthews and Lloyd. Our detailed analysis laid the basis for Eccles’ subsequent studies on presynaptic inhibition. Another interesting finding was presynaptic axonal hyperpolarization following tetanic stimulation: in keeping with the idea that a larger action potential releases more transmitter from the nerve endings, this could explain the well-known posttetanic potentiation.

Working with Eccles was a most refreshing experience. Always a full participant in experiments, though he let us do the bulk of the dissection, he insisted on preparing himself the fine filaments of dorsal and ventral roots for stimulation. He sat at the controls at the stimulator and the camera throughout experiments that often went into the early hours of the morning. Blessed with a remarkable memory, and drawing on his wide knowledge of neuroscience, he was ever ready to discuss new findings and ideas. His enthusiasm when embarking on a new experiment was like that of a child with a new toy. Though not outstanding as an original thinker, his vast energy, industry, and uncanny ability in grasping the significance of new concepts or techniques, and using them in his own thinking and investigations, were the foundations of an exceptionally successful research career, crowned by the well-deserved awards of a knighthood in 1958 and a Nobel Prize in 1963.

Both our sons were born in Canberra, as was the Miledis’ only son Rico. When Eccles heard us worrying about the babies, he commented: “Wait till they grow up. Then you’ll have something to worry about.” Having nine children of his own, he spoke with the voice of experience. In most respects, life in Canberra, with little to distract one from work, was ideal for research. But one felt very far from the really interesting parts of the world. So rather than take up some possible posts in Australia, after meeting with John Gaddum during his visit to Canberra, I was happy to accept his offer of a job at Babraham—where he had recently moved from Edinburgh, to become the new Director of the ARC Institute. So we turned yet another page.

Another Long Sea Voyage

Our departure, late November 1958, didn’t run smoothly. Till the last hour, I was closeted with Eccles, selecting material for figures for the paper on posttetanic hyperpolarization, which I had insisted on writing. When I got home, I found my wife in tears, with so much remaining unpacked, and the babies howling. So we were too late to catch the afternoon train to Sydney— to the dismay of our colleagues assembled at the station to say goodbye. The delay was of no other consequence as our ship, the Blue Funnel line’s Helenus, carrying mainly cargo and some two dozen passengers, was coming to Sydney only 2–3 days later. Sailing along the Great Australian Bight, accompanied by an albatross, went smoothly. So did the journey across the Indian Ocean, enlivened by flying fish and dolphins and achingly lovely sunsets. Our first port of call was Aden. The pleasantly warm conditions persisted along the Red Sea; but ceased sharply as we entered the Mediterranean—we could no longer wander about the decks in shorts and sandals. When we saw Etna glimmering at sunrise and sailed through the straits of Messina, we knew we were back in Europe. How could I also not be excited seeing Stromboli erupt at regular intervals as we passed the Ionian Islands? Stromboli had featured so prominently at the end of one of my favorite Jules Verne books, Journey to the Centre of the Earth. At our next stop, in Genoa, my mother was at the dock, eagerly waiting to see us and the very new grandchildren. Albeit under continual rain, treading the old paving stones of the ancient republic felt like a return to my true home. Though the Mediterranean had been chilly, much worse was to come after Gibraltar. The notorious Bay of Biscay fully lived up to its reputation. Buffeted by fierce wind and mighty waves, we rolled and pitched until even hardened travelers—such as we thought ourselves—were unwontedly queasy.In London, my father had arranged some accommodation for us in Putney. We didn’t know that we were in a flat owned by the parents of Alec Bangham—who was going to be a helpful colleague at Babraham. Alec’s father, an expert on coal, prophetically condemned the burning of coal as a mere source of energy. Unluckily for us who had just arrived from Australia, it was a bitterly cold winter. In Babraham, the house that had been allotted to us on the Close was so cold that the pipes froze and we had no running water. The landscape around Babraham was very beautiful, all the trees glistening with hoar frost in the bright sunshine. But, for the first few days, with two babies to look after, we all suffered.

Though in principle devoted to research on general animal physiology, Babraham was in effect becoming a thriving center of brain research. Gaddum, was especially interested in neuropharmacology. He brought down from Edinburgh Marthe Vogt, a fine scientist, who had collaborated with Dale and Feldberg in ground-breaking studies of cholinergic transmission, but whose learned, but somewhat dryly delivered lectures were largely-wasted on the raw Edinburgh students. She was now probing energetically monoaminergic mechanisms in the brain. Even more familiar was Catherine Hebb, who had been one of my teachers in the Edinburgh Physiology Honors Course. The younger sister of Donald Hebb, she had left McGill to work with De Burgh Daly in Edinburgh. Her particular interest was the role of choline acetyltransferase in the synthesis of acetylcholine (ACh). New to me were Victor Whittaker—whose pioneering isolation of synaptosomes revolutionized neurochemistry—and Rex Dawson, an expert on phospholipids, at that time considered very stable constituents of cell membranes, little involved in ongoing cell function. Dawson’s work on inositol phosphates contributed to Berridge and Irvine’s discovery, 20 years later, of IP3’s pivotal role as second messenger. Not mincing his words, he told me that physiology had run its course and that the future belonged to biochemistry. – which of course I denied, unprophetically.

Acetylcholine in Muscle

At first, I continued with experiments on the phrenic-diaphragm preparation. In Canberra, we had shown that EPP-like responses can be evoked with minute quantities of ACh; but these were still much greater than previous estimates of ACh release in ganglia. Perhaps the gap might be narrowed by measuring ACh released in the diaphragm by stimulation at a low frequency. In collaboration with Jim Mitchell—who did the bioassays—we observed a mean release of 0.12 pmole of ACh per impulse, corresponding to only 10–17 mole per phrenic nerve ending. This was only marginally less than the amounts of ACh with which we had produced EPP-like responses in Canberra, in the same muscle. We also measured ACh diffusion in agar gels and used those data when analyzing the time course of ACh diffusion out of the diaphragm; and also in a study of ACh release from microeletrodes to get an estimate of the transport number of ACh during iontophoresis.

Transmitters in the Cerebral Cortex

In late February 1961, John Phillis and his wife arrived from Australia with their two infant boys (one only 6 weeks old). Here he was, full of bounce and vigor, eager to get on with experiments. Eccles had recommended that he should stay with the frog spinal cord—on which he had been working in Canberra. My proposal that we continue iontophoretic experiments that I had started in the cat’s cortex was much more to his liking. We were both young and energetic, and had excellent technical support from Keith Legge as well as good workshop facilities. Three experiments (usually ending in the early hours of the morning) per week, alternated with days when data were analyzed and fresh electrodes were prepared for the next experiment. Working with five-barrelled micropipettes, of the type developed in Canberra, we soon began an exhaustive survey of the cerebral cortex, looking for transamitter-like actions. Having four channels available for testing different substances, we were able to move ahead quite fast. Over the next 2 years, we applied a very wide range of compounds—but especially those occurring naturally in the brain—on some 4000 units, recorded in the cerebral and cerebellar cortex, mostly in anesthetized cats, as well as some rabbits and monkeys, and some unanesthetized “ cerveaux isolés.” By far the most impressive effects were the fast excitation and inhibition produced by amino acids and the slower excitation by ACh.

ACh: A Transmitter in the Cerebral Cortex?

Within 4 months of John’s arrival, we had tested ACh on 1374 cortical neurons. Of these, 200 showed excitation, characterized by a slow onset and prolonged after-discharge. Responsive neurons were found in all areas of cortex, mainly in deeper layers. A subliminal action was often revealed by superimposing ACh release on weak excitation by glutamate. As initial tests of atropine seemed to block equally effectively glutamate-evoked firing, initially we thought that, albeit not nicotinic (nicotine had no consistent effect), this was not a muscarinic action. When we discussed these results with Gaddum, he questioned this conclusion. Were we applying too much atropine and so eliciting a nonspecific block of firing? Repeating the tests with lower concentrations of atropine (as well as other agents) indeed confirmed a muscarinic mechanism. Its slow time course of action was very much in keeping with the classical descriptions of peripheral (parasympathetic) muscarinic mechanisms. Bearing in mind previous evidence that ACh is released in the cerebral cortex by K.A.C Elliott, F.C. MacIntosh, and H.H. Jasper (all working independently at McGill), our ACh-sensitive neurons were likely to have a physiological role in cortical function. But where did the cholinergic innervation come from? The cortex itself, or some deeper region? With my colleagues Catherine Hebb and Ann Silver, we found that choline acetyltransferase, normally plentiful in cortex, disappeared from a gyrus isolated in situ by undercutting. So the cholinergic axons must have a subcortical origin.

Ascending Cholinergic Pathways

To locate cholinergic pathways and cells, Ann Silver and I made a detailed analysis of the distribution of acetylcholinesterase (AChE) in the cat’s brain. The results were unequivocal. Large fiber tracts such as the callosum or the internal capsule showed no AChE staining; but numerous fine fibers traveling toward the cortex did, and so did large groups of neurons situated in the deepest part of the forebrain. In the large brain of mature cats, however, we could not follow stained fibers all the way from the base of the forebrain. But in cat embryos and foetuses, we could readily identify ChE-stained cells migrating from the germinal epithelium to cluster in the deeper part of the pallidum and the substantia inominata; and, from these cells, sharply stained fibers growing toward, and ultimately invading, the previously quite unstained cortex. Along the medial wall of the hemisphere, a similar projection of fibers originated from the strongly stained medial septal region.

These findings were fully in agreement with those of Shute and Lewis’s in the rat’s brain—pursued independently in the Cambridge Anatomy department. In view of the known fluctuations in ACh release according to sleep and wakefulness, we boldly speculated that the observed ascending pathway, by facilitating neuronal firing in the cortex, might play a role in generating “consciousness.” The characteristic ACh-induced after-discharges seemed particularly significant in the light of Libet’s observation on patients undergoing neurosurgery: when their thalamus was stimulated electrically with single shocks, they felt nothing, however strong the stimulation; but they became conscious of even weak shocks applied repetitively for at least

0.5 second. Many scientists—including Adrian, Morrison, Dempsey, Bremer, and Jasper—had noted a correspondence between after-discharges in sensory cortex and wakefulness. But why would such repetitive activity lead to “consciousness”? A simple (no doubt simplistic) explanation could be that repetitive firing elicits the changes in synaptic efficacy needed for learning. If consciousness required the continual formation and retrieval of memories, it might well depend on the activity of ascending cholinergic pathways.

Amino Acid Transmitters

Unlike ACh, long suspected of playing a major role as transmitter in brain, amino acids were not viewed as candidates for such function. They did not fit the then current expectations. For example, the high concentration of glutamate and related amino acids in the brain seemed to argue against this notion. In any case, glutamate was a major constituent of proteins; it was involved in metabolic reactions related to the Krebs cycle and removed potentially toxic ammonium produced by metabolism. Clearly, amino acids belonged to biochemistry. For pharmacologists, another important negative feature was the absence of any relevant bioassays.

L-Glutamate

Albeit present throughout the animal kingdom, glutamates’s many-fold signaling functions came to light only after the discovery of its potent action in the mammalian CNS (in 1960). In a vast study of seizures induced by various chemicals, Hayashi (with some 100 collaborators) found that glutamate was one of the most potent. But he concluded that glutamate could not be the “excitatory transmitter” (Hayashi, 1959). On the other side of the Pacific, at Caltech, Van Harreveld was comparing the effects of various agents extracted from cerebral cortex on spreading depression in rabbit cortex and on muscle contraction in the crayfish. In both preparations, L-glutamate had the strongest action, though aspartate and D-glutamate were also very potent in cortex (but not crayfish). So Van Harreveld (1959) proposed that L-glutamate, released from depolarized cells, could be a major factor in the propagation of cortical spreading depression but made no suggestion as to its possible function in crayfish muscle. Meanwhile, on yet another side of the Pacific, in Canberra, Curtis, Phillis, and Watkins were recording the effects of various amino acids applied to spinal neurons by iontophoresis from microelectrodes. In 1960, they reported a marked, but “nonspecific” excitatory action of L- and D-glutamate and aspartate. Thus, by the end of the 1950s, there was a consensus that glutamate strongly excites many central neurons but was unlikely to be a synaptic transmitter.

Within a few weeks after starting our experiments , it became obvious that glutamate was outstanding as excitant of cortical neurons. As we first reported to the Physiological Society (in September 1961), L-glutamate strongly excited virtually all neurons in the cerebral (and cerebellar) cortex—in good agreement with Van Harreveld—much as in the spinal cord, except that D-glutamate was far less effective. Apart from some nonendogenous sulphonated derivatives, none of the numerous other agents tested (including monoamines, which were mostly depressant) had such a fast, quickly reversible and easily reproducible action. With optimal electrode positioning, a brief burst of firing could be elicited by very short pulses of iontophoretic current (lasting only 20 ms), which would release only some 50 fmole of glutamate, much less than the average amount of glutamate present in brain cells. From the time course of evoked firing, the calculated effective glutamate concentration was about 100 μM—in good agreement with threshold values of 100–200 μM later observed in olfactory cortex (by Misell and Richards, in 1979) and not much higher than Van Harreveld’s estimate of 35 μM for crayfish muscle.

In all respects, L-glutamate’s action was very much like the fast nicotinic action of ACh in muscle and sympathetic ganglia. The unique combination of a very high concentration in the brain—ensuring a ready supply for release—and its high excitatory potency made L-glutamate an obvious candidate for the role of fast synaptic transmitter. One counterargument, the absence of an extracellular catabolic enzyme—analogous to AChE at cholinergic junctions—was irrelevant, because glutamate was known to be avidly taken up by brain cells, a mechanism of removal that has proved to be the most common for other transmitters. Another supposed negative feature, that glutamate strongly excites spinal Renshaw cells, which are activated by recurrent cholinergic axons, ignored their possible innervation by glutamatergic fibers; or, what could not then be suspected, that cholinergic axons might also release glutamate as a cotransmitter. At any rate, I was convinced that L-glutamate was probably the main excitatory transmitter in the CNS.

One aspect of glutamate’s action, which later proved of great clinical importance, completely eluded us: its “excitotoxic” action. Indeed, we emphasized as an attractive features of glutamate the apparent absence of any noxious effect: neurons could be excited either repeatedly or continually for many minutes without causing any obviouse harm—which seemed in keeping with its proposed role as physiological transmitter. So when Olney began reporting (in 1967) that the ingestion of mono sodium glutamate’(MSG’) caused neuronal degeneration, we at first greeted his papers with disbelief. That an excess of transmitter might be deleterious seemed paradoxical. This lesson taught me the importance of controlling for long-term effects of bioactive agents.

GABA and Inhibition

The arrival of Ernst Florey, a young Austrian zoologist, in California, in 1953, was a crucial event in the history of synaptic inhibition. He came to work in the laboratory of the Dutch zoologist Wiersma, who had been studying the properties of a sensory organ in crayfish muscle, recently discovered by a Polish zoologist (Alexandrowicz) working in Plymouth (England). This multinational research took an unexpected turn when Florey found that an extract from bovine brain (“Factor I”) strongly inhibited the firing of this sensory neuron. In the next act, the scene shifted to Montreal, to KAC Elliott’s neurochemical laboratory at the Neurological Institute. After testing on the crayfish preparation all agents known (at the time) to be present in the brain, Bazemore, Elliott, and Florey found that GABA (identified as a major constituent of brain in 1950 by Roberts and Frankel and two other groups) was the most effective. This finding established GABA as possible inhibitory agent in crustacean muscle. Could it also be an inhibitor in the CNS of vertebrates? Spurred by Florey and MacLennan’s report that topically applied Factor I depressed spinal transmission, Curtis’s group in Canberra tested GABA on single spinal neurons. Indeed, GABA strongly inhibited all neurons, but this action, like that of glutamate, was dismissed as nonspecific. This was the general opinion at the first Inhibition and GABA Symposium (organized by Eugene Roberts in1959), when John Phillis and I began our experiments on cortical neurons.

Of the many agents we tested, only GABA and a few related omega amino acids (such as beta-alanine) consistently had a powerful, but quickly reversible inhibitory effect on cellular firing throughout the cortex and cerebellum. Even very brief applications of GABA could inhibit firing. In contrast to the spinal cord, however, where Curtis et al. had observed comparable effects of glycine and GABA, glycine was much less potent in the cortex. Bearing in mind that GABA is normally present in the brain in high concentration, we concluded that GABA was likely to be the natural transmitter at inhibitory synapses in the cortex and cerebellum, and probably other parts of the CNS.

After John Phillis’s return to Australia in September 1961, Mirjana Randić (a visitor from Zagreb), Donald Straughan, and I began to explore inhibition in the cortex, comparing GABA’s action with natural inhibition.

In these extracellular recordings, inhibition was elicited on a background of controlled unit firing induced by glutamate. This enabled us to observe the inhibitory action of various inputs, both quickly and reproducibly, and on many more cells than could be recorded intracellularly. Our most striking finding was that inhibition was the predominant responses to activation of every pathway tested, including the afferent thalamo-cortical, recurrent pyramidal (evoked by antidromic stimulation)and transcallosal. With stronger stimulation, firing could be interrupted for up to 200 ms. When stimulating the cortical surface, inhibition was evident throughout all cortical layers, over a horizontal distance of 1 cm, albeit restricted to the stimulated gyrus. Such powerful and widespread inhibition ran counter to a long held belief that synaptic inhibition was absent from the cortex. Though its long duration was compatible with a long-lasting chemical transmitter action— comparable to that of GABA—we could not detect a selective block of inhibition by various convulsants. Our failure to recognize picrotoxin- or metrazol-induced intense excitation as due to block of inhibition was a glaring mistake. Knowing that picrotoxin suppresses both inhibition and the effects of GABA in crustacean muscle, we should have tested it more carefully. As when initially testing atropine on ACh’s action, we misjudged the effects of large doses of antagonists and strong stimulation. Picrotoxin’s anti-GABA action in the vertebrate CNS was to be shown only a few years later by my first graduate student at McGill. Which raises the question: how did I come to McGill?

Why Did We Leave Babraham?

At Babraham, my research was progressing well. Life was quiet, but Cambridge with its Arts Theater and Cinema was only a few miles away. London was also easily accessible for weekend visits. In many ways, this was an ideal situation for getting on with one’s work. Scientifically we were far from isolated. I went to most of the near-monthly meetings of the Physiological Society, often driving to outlying parts of the country with my old Canberra friend, Ricardo Miledi (by then well into his long and productive collaboration with Bernard Katz at UCL). I also regularly attended the Hardy club meetings in Cambridge, at one of which Francis Crick presented his great DNA story. In 1964, I was promoted to a more senior position at Babraham and also became a U.K. citizen—up to that time my status as “Displaced Person” had not obviously hindered my career. I suspect that few (if any) other countries would be as open-minded in this respect. So why did we leave for Canada? Quite by chance. At a meeting in London, Ben Delisle Burns proposed that I spend a year at McGill as Visiting Professor during his impending sabbatical leave. I could use his office and lab and do a bit of teaching. When I discussed this idea with Jeanne, she agreed that, after nearly 6 years at Babraham, it could be a pleasant “sabbatical” change.

My employers raised no objections. By September 1964, we were on our way, sailing on the Empress of Britain, to Montreal. Awaiting us at the dock were the Head of Physiology at McGill (Frank Campbell MacIntosh, generally known as “Hank”) and Andrě Grolimond, my earliest friend, from the very first schooldays in Geneva. Andrě had emigrated to Canada, first to British Columbia, where he’d met his wife Joan, and then gradually moved east: he was now in Montreal, working for Hoffmann-La Roche.

Things had started well. We were renting Ben Burns’ house on Victoria Avenue in Westmount, conveniently situated within walking distance from a school for the boys and a short drive from the McGill campus downtown. Life in Montreal was an altogether new and exciting experience. Neither Jeanne nor I had ever lived in a really large city. We knew London quite well, but only as visitors. In Montreal, we were in a vibrant metropolis, with many theaters, cinemas, galleries, and plenty s of music—so much that one could not see or hear more than a small fraction of what was available (the mark of a rich cultural center). For me especially, the mixture of French, English, and American influences was exhilarating. Though we were not fully aware of it, Quebec was in the middle of its “Quiet Revolution,” which utterly changed a previously conservative, inward-looking, and church-dominated society. More evident were preparations for the world exhibition, EXPO 67, for which highways, a metro system, and even a new island were being built. The winter was cold but often sunny, and summer really hot. Montreal is unusually well situated, with numerous skiable hills in winter and warm lakes in summer, mostly within an hour’s driving. My particular favorite was Mont St. Hilaire, rising from the flat St. Laurent’s valley, one the seven Monteregian hills produced by lava outflows and the only one still preserving the ancient forest that originally covered the whole region. It had been bequeathed to McGill to preserve its character as a pristine nature reserve. Only 20 km away, it offered many fine trails for short or long hikes as well as an attractive lake.

The Physiology Department was on the main campus, in the Biology Building—opened in the1930s by Sherrington. No goats and sheep about, as at Babraham but rather a bustling city. From the window in Ben’s lab, looking south over the trees of the campus, in late afternoon I was dazzled by the sight of a very handsome skyscraper (Place Ville Marie), its glass and aluminum surface illuminated by the setting sun. In spite of so many distractions, I kept busy. There was much to write up from experiments at Babraham and some teaching. There was also a rich fare of seminars on many topics— especially at the Neurological Institute (where Penfield was still active). GABA was a major focus of activity, with Elliot, Jasper, and van Gelder still trying to make sense of conflicting evidence. The year passed quickly.

Wanting me to stay at McGill, Hank MacIntosh maneuvered the faculty into offering me the Research Chair in Anesthesia—which had remained open since the departure of Gordon Robson. I was attracted by this position, independent of either Anesthesia or Physiology and having no teaching obligations. With it came the prospect of substantial laboratory space in the new Medical Sciences Building, nearing completion on th the lower slope of Mt. Royal. Some disturbing news from Babraham decided the issue. Concerned by the proliferation of basic neuroscience at Babraham, the authorities advised everyone that research must focus on farm animals. With the choice of directed research on one hand and a research group of my own on the other, I accepted the post in Anesthesia Research.

We had to return to Babraham for a few months to sort out the formalities and pack our belongings. By the end of the summer, Jeanne and the boys were again sailing on to Montreal, while I flew to Budapest to attend a meeting. For my wife, moving into the newly purchased house in Westmount was a challenging experience. In the empty rooms, water had to be boiled in an electric frying pan borrowed from new friends. Things were not made easier by my having to travel again, this time to Japan for the 1965 International Physiological Congress.

Visiting Japan was both exciting and disconcerting. On my first day, heavily jet-lagged, I wandered off to see the sights. Needing a meal I stopped at a restaurant with outdoor seating in the park near the Imperial Palace. With the menu displayed concretely in the window, as very life-like plastic models in full color, ordering food was easy enough. Loudspeakers relayed a Brahms symphony as I struggled with chopsticks, picking at what I thought would be an appropriate local dish. Then I noticed that the Japanese at neighboring tables were all eating spaghettis and risottos with forks and knives. But they were too polite to pay overt attention to the foreigner. Looking forward to an admirable collection of Japanese art, I walked to the museum in Ueno Park. Instead of numerous beautiful screens, or at least plenty of fine woodcuts, the large rooms were virtually empty, except for the odd vase—the very antithesis of the great European collections, with minimal wall visible between the paintings. By contrast, the Kabuki theater more than lived up to expectation: an engrossing auditory and visual experience, combining grand costumes, very stylized acting, and wonderful music. I was mesmerized and could have stayed another hour beyond the regular 4-hour performance. Equally fascinating, but on much larger scale, were the temples and gardens of Kyoto. Perhaps the most unsettling event in Japan occurred on my last night in Tokyo, when I stayed in a traditional inn— recommended by guidebooks as a uniquely Japanese experience. After an early meal in my sparsely furnished room, sitting on a tatami mat, and facing the prospect of a long evening with nothing to read, I turned on the not at all traditional looking television set. To my amazement, before the screen came on, I heard someone speaking quite unmistakable Croatian. Was I hallucinating in these strange surroundings, or was it the sake that I had drunk with my meal? The explanation was much simpler. Lovro Matešić, the conductor of the Hamburg opera and on tour in Japan, was being interviewed during the intermission. A most curious coincidence.

Scientifically, the Congress was very satisfying. The cerebellum was coming into its own: Masao Ito’s masterly demonstration that Purkinje cells are inhibitory revolutionized people’s thinking about the cerebellum and inhibitory neurons—which could no longer be considered as exclusively local interneurons. The impressive research performed by Ito and his collaborator over the next decades fully deserved recognition by a Nobel award—as I proposed in the 1980s when asked to make a recommendation. This never came. The workings of the Nobel committee remain unfathomable. It was interesting to see in the flesh such venerable Japanese scientists as Hayashi and Kato—the author of the monograph The Microphysiology of Nerves, in which he described, in colorful English, his intricate studies on single nerve fibers and incidentally stated that he would not hire as technician anyone unable to master within 20 minutes the technique of single fiber dissection. My main involvement at the Congress was in a symposium on synaptic transmitters at which I stressed the importance of amino acids as presumptive transmitters throughout the CNS. I never wavered from this belief.

In Montreal, I was joined by my first postdoctoral fellow. Susan Schwartz had just completed her graduate studies at Albert Einstein under the supervision of Vahé Amassian. She had been analyzing patterns of firing of various types of sensory afferents and wished to follow up by looking at transmitter actions on the second-order neurons in the cuneate neucleus. Before doing any experiments, we had to obtain and assemble a minimum of electrophysiological equipment. Albeit impressively shielded, the recording rooms on the 12th floor in the new McIntyre Centre, were quite empty. With the help of Keith Legge—my excellent technician; he had come from Babraham to join us—we scrounged around and borrowed odd items. Within a few weeks, we were able to start experiments.

First on my priority list was to try to get more direct evidence about GABA’s inhibitory action. Though I was convinced that GABA was the most likely inhibitory transmitter in the cortex, we needed to show that the synaptic potentials (IPSPs) and GABA had similar effects on the cell membrane, independently of the membrane potential. We therefore had to record intracellularly long enough to compare IPSPs and the effects of several GABA applications. Two microelectrodes were needed, one with a tip fine enough to penetrate cells and another for GABA release. I had tried a concentric arrangement, with the finer-tipped electrode inserted inside a wider, GABA- containing barrel; but iontophoretic currents generated huge recording artifacts. A possible solution (suggested by Bob Werman, who had visited us in Babraham and now worked in Indianapolis) was to use two pipettes, cemented together but with separate tips. He was kind enough to give me a Narishige micromanipulator for the preparation of such double electrodes— which indeed proved very effective.

In spite of many technical problems—our intracellular recordings in the cortex in situ were most often transient—several aspects of inhibition worked in our favor. Prominent IPSPs could be evoked in all neurons by surface stimulation; they were associated with large increases in membrane conductance; and hyperpolarizations became more prominent as the membrane potential deteriorated. The results were clear. GABA raised the membrane conductance, thus occluding IPSPs, in a dose-dependent manner. Current injections reversed GABA’s effect and IPSPs at the same membrane potential, and both were also reversed by injecting Cl ions into a cell (such reversed, depolarizing IPSPs could even generate action potentials!). But intracellular injections of GABA did not affect the membrane conductance. These findings, which strongly reinforced the idea that GABA is the main inhibitory transmitter in cortex, were first reported in Nature in September 1966. In contrast to these marked effects on neurons, when tested on inexcitable cells (presumed glia) GABA caused only a mild depolarization and no increase in conductance. We suggested that this depolarization might reflect electrogenic uptake, in keeping with previous evidence that brain slices take up amino acids.

Before Susan Schwartz returned to New York, we had a good look at neurons in the cuneate—working together with my first graduate student Anibal Galindo (a Columbian anesthetist) and George Yim, visiting from Purdue University. Like spinal neurons, cuneate cells were equally sensitive to glycine and GABA and were readily excited by glutamate. We also tested ATP, which had been proposed as the transmitter released by primary afferents: ATP did excite some cuneate cells, but far less consistently than glutamate. From this we concluded that the sensory pathway was probably also glutamatergic. A surprising feature of cuneate neurons was the pattern of firing in response to glutamate, which closely matched the characteristic discharge of different types of sensory axons. Fast adapting axons evidently formed synapses on fast adapting cells (and so on). Such matching of pre- and postsynaptic properties was unexpected—though it made s sense functionally.

A few more pages were added to the GABA story. With new collaborators, including John Kelly (Wellcome Fellow from Edinburgh, where he obtained a Ph.D. in pharmacology under Bernard Ginsburg’s supervision), Jean-Pierre Dreifuss (visiting from Geneva), and Mary Morris (another anesthetist, starting her Ph.D.), we obtained more data on IPSP-associated and GABA-induced conductance changes and compared the rates of reversal of IPSPs seen when different anions were injected into neurons. For inorganic univalent anions, the apparent rates of permeation through the IPSP channels were linearly related to their limiting conductance in water, but polyvalent anions, such as sulphate and citrate, were virtually impermeant.

From these data, we concluded that the width of the inhibitory channel was approximately twice that of Cl–. The more surprising finding that some large organic anions also reversed IPSPs seemed to indicate an interaction with the hydrophobic component of the channels but may have been caused by some indirect effect. In these experiments, we measured only the early component of IPSPs, which reversed most rapidly. If we had examined the later, less reversal-prone component, we might have discovered another inhibitory action of GABA, that mediated by K ions and GABAB-receptors—but that came to light only a decade later, in Norman Bowery’s seminal paper of 1980.

Home Life in the 1960s

During the 1960s, Montreal was moving toward a peak of excitement and optimism generated by EXPO 67. This great event proved enormously successful. From all over Canada and the adjoining United States, visitors poured in to enjoy the happy “ambiance.” National pavilions catered to every taste, ranging from the very traditional Soviet—displaying impressive machinery—to the U.S.’s geodesic dome, containing both the recent lunar module and a tongue-in-cheek collection of Hollywood relics. Long lines formed outside the Czechoslovak Laterna Magika, a clever melding of stage and film and the futuristic cinema at the Canadian Labyrinth. Great opera companies and a fine collection of paintings were imported, and much else. It was a golden year, when Canada also celebrated the centenary of its constitution: “one country, one people” seemed a reality. It did not endure. The success of the “quiet revolution” led to a resurgence of Quebec nationalism, further stimulated by de Gaulle’s celebrated call “Vive le Québec libre!” The new slogan was “Maîtres chez nous!” By the late 1960s, the student agitation—that had started in Paris and California—reached Montreal. Here, it took a special form: part Marcusian/Marxist, part Québécois/ nationalist. At McGill, students occupied the Principal’s office and held long palavers. Young radicals, unexpectedly led by taxi drivers, wanted to reform society; but also loudly voiced long-suppressed resentment against the privileged status of Anglo-Canadians and the English language. Thus, McGill was attacked both internally (by its own leftist students) and externally, as both a bastion and a symbol of “Anglo” supremacy. In time, the student disturbances subsided, as they did everywhere else. In Montreal, many of the newly conscious “Québécois”—no longer subservient “French Canadians”— became increasingly militant. At first, there were single terrorist acts (bombs in mail boxes). Then, after the formation of the National Liberation Front, some prominent individuals were kidnapped (one even executed). The situation in Montreal became critical; the provincial government seeming to lose control, the federal government stepped in, sending in armored cars to police the streets. The city was soon back to normal; but the presence of troops in Montreal exacerbated nationalist feeling. The sense of being a nation apart grew ever stronger. The provincial political scene became sharply polarized between ostensibly federalist Liberals and the avowedly separatist Parti Quebecois.

The Opposite Effects of Acetylcholine and Cytoplasmic Ca²⁺ on Excitability Are Mediated by Opposite Changes in K⁺ Conductance

Perched in our McIntyre tower, little disturbed by the momentous events of the period, our research went on unabated. A major shift of focus took us back to cholinergic mechanisms in the cortex. In experiments (with Ann Silver and Rod Reiffenstein) on cortical slabs, chronically isolated from the rest of the brain by undercutting in situ, we found no evidence of denervation supersensitvity to glutamate and GABA, but the cells failed to respond to ACh. The unusual features of ACh’s action in the cortex—its slow time course and the absence of a clear conductance increase—suggested some novel mechanism of excitation. Could ACh produce a slow depolarization by activating electrogenic Na/K pumping? There was a precedent: the Hokins had shown that ACh stimulates Na secretion by the salt gland in birds. Clearly, we needed to test metabolic blockers that should interfere with the postulated pump-mediated action.

Mechanism of ACh Action in the Cortex

In a joint study—with Hiroshi Kawamura, René Pumain (‘coopérant’ from Paris) and Jean-Marie Godfraind (from Louvain, then still a bilingual university), we looked at the effects of some metabolic inhibitors. By reducing the supply of ATP—needed for the operation of the Na/K pump—such inhibitors should interfere with the muscarinic action. Indeed, dinitrophenol (DNP), an uncoupler of mitochondrial function, very effectively suppressed the action of ACh. Though at first tempted to conclude that ACh acted by accelerating electrogenic Na/K pumping, closer examination of intracellular recordings revealed that DNP consistently hyperpolarized cells and reduced their membrane resistance. Because DNP’s effect had a very negative reversal potential and was quite insensitive to intracellular injections of Cl–, a more likely explanation was that DNP increased K⁺ conductance.

In parallel experiments with René Pumain and Leo Renaud (M.D., but now a Ph.D. student; in spite of his name, Anglophone Canadian), we found that ACh’s characteristic slow depolarizing action was associated with an increase in membrane resistance. In corresponding voltage-current plots, the depolarization disappeared at a very negative potential. These observations could be readily explained by suppression of an ongoing hyperpolarizing conductance (either GK or GCl). But Cl– injections, which greatly altered the Cl-mediated IPSPs, had no effect on ACh’s action. So we concluded that ACh excited by suppressing GK. This was a new idea, for which we knew of no parallel in the literature. But the data were too consistent to be ignored.

So here was a novel mechanism of transmitter action, not as a direct excitant but rather potentiating other excitatory inputs. It was the first example of what later came to be known as modulator actions. Such modulations of synaptic actions by ACh (and various moamines and peptides) were subsequently identified at many other sites and in many species. As it turned out, ACh blocked the voltage-sensitive m-type K current—later identified by Brown and Adams—and the A current, as well as less voltage-sensitive K channels, including some that maintain the resting potential or mediate the later phase of postspike hyperpolarizations. In this manner, ACh increased the general level of activity of cortical neurons; and perhaps most important, facilitated and prolonged their responses to afferent intputs. All these features supported the concept of a cholinergic regulation of cognitive function. which might account for the loss of cognitive function that follows degeneration of the ascending cholinergic pathways in Alzheimer-type dementia.

Neuronal Ca Ions and Excitability

How would GK be raised by DNP? One possibility, that DNP might be taken up by the cell membrane and act as a selective K channel, seemed unlikely. On the other hand, it was known that DNP, by short-circuiting the inner mitochondrial membrane, tends to release Ca ions normally accumulated by mitochondria. If a rise in cytoplasmic Ca²⁺ somehow activated K⁺ channels in the plasma membrane, we would have an explanation for the hyperpolarizing action of DNP. This was an exciting new possibility. If true, cytoplasmic free Ca²⁺ could be an important modulator of excitability, whether caused by influx of external Ca²⁺ or by release from internal stores.

At that time, internal signaling by Ca²⁺ was virtually unknown. The only relevant information that I could find was a brief 1968 report (by R. Whittam) that metabolic inhibition makes red blood cells more permneable to K⁺, probably by raising internal Ca²⁺. In fact, this had been observed a decade earlier by G. Gardos: his discovery was later recognized by hematologists by referring to the “Gardos channel”. Totally new findings are seldom made by a single individual or group. So it was in this case. Unknown to us, while we were proposing that DNP hyperpolarizes mammalian neurons by raising internal [Ca²⁺], Bob Meech, then a visitor in Strumwasser’s lab at Caltech, was busy injecting CaCl₂ directly into large molluscan neurons. His experiments showed quite unequivocally that internal Ca²⁺ activated K⁺ channels. Although I had attended the1970 FASEB meeting in Atlantic City, where both Meech and I presented our respective stories—at different sessions—we knew nothing about each other’s findings. Not until I visited Cambridge later that year (in September 1970) and gave a lecture attended by Bob Meech (who had returned to the Cambridge Zoology department), did I learn about his results.

Our hypothesis needed testing more directly by injecting Ca ions into CNS neurons. But this was not feasible in the cortex with the only micro electrodes then available, high-resistance “sharp” electrodes. The solution was to do the experiments on the much larger spinal motoneurons. Working “blind,” we could not insert separate microelectrodes into a given cell, but some motoneurons can withstand the insertion of 3- (or even 4-) barreled electrodes having tips up to 2–3 μm in diameter. By passing currents from a CaCl₂ to a KCl-containing channel, Ca²⁺ could be released into cytoplasm while keeping current flow through the cell membrane to a minimum. But even this minimum was sufficient to mask most membrane potential changes. The clearest effects observed in these arduous experiments— performed with Anne Feltz and a graduate student (Adam Lisiewicz)—was a reversible drop in excitability and membrane resistance, probably caused by a rise in GK—as indicated by the negative reversal level of the potential changes.

Apart from the relatively selective block of cholinergic excitation, we had little evidence that the postulated Ca²⁺-dependent GK was of much significance for motoneuron function. For the next few years, working with several collaborators—including Bob Werman (on hemisabbatical leave from the Hebrew Universtiy), Ernie Puil (then at the Universitě de Montréal), John MacDonald, Andrea Nistri, and Yvon Lamour (all post doctoral fellows)—our experiments focused on this problem. An obvious test was to try to prevent any [Ca²⁺]-dependent changes by buffering internal [Ca²⁺]. Injections of EGTA indeed sharply reduced AHPs, indicating that Ca²⁺ influx during the action potential was responsible for the AHP—which is an important determinant of the maximum firing frequency of many neurons. There was also some reduction of resting membrane resistance, suggesting that cytoplasmic Ca²⁺ helps to stabilize the resting potential. EGTA also suppressed the action of DNP, in keeping with a DNP-induced rise in cytoplasmic [Ca²⁺]. We further showed that only only Sr²⁺ had a Ca²⁺-like effect, whereas Mg²⁺, Co²⁺ and Mn²⁺ suppressed AHPs and increased the membrane resistance—which we interpreted as probably owing to competition with Ca²⁺ for the relevant K⁺ channels. On the other hand, when applied outside motoneurons, Co²⁺ and Mn²⁺, well-known blockers of Ca currents, greatly depressed AHPs, confirming the external origin of the Ca²⁺ responsible for the AHP.

For me, this was an exciting time. One does not often come up with a really new idea, especially one that stood up to critical examination, Though at first greeted with much skepticism—AHPs were thought to be mediated by a voltage-dependent K current (Hodgkin and Huxley’s ‘delayed rectifier’)— the new findings were soon confirmed by numerous groups. The discovery that Ca²⁺-dependent channels regulate excitability opened up a vast area of research, as such channels are found in many central and peripheral cells, throughout the animal kingdom. A particularly interesting feature is that they can be activated by either Ca²⁺ influx or Ca²⁺ release from internal stores—including endoplasmic reticulum, as described a decade later by Berridge and Irvine.

The release of Ca²⁺ from mitochondria, linked to changes in cellular respiration, might even play a role in the control of consciousness—insofar as this depended on a heightened degree of neuronal firing in the cortex, maintained by ongoing liberation of ACh. The opposite actions of ACh and cytoplasmic Ca²⁺ on K⁺ channels seemed very suggestive A prominent theory held that narcosis is caused by depression of cellular respiration (Verworn, Quastel). It was tempting to propose that mitochondrial depression by anesthetics could lower the activity of central neurons by raising cytoplasmic [Ca²⁺], thus suppressing consciousness. I did not resist the temptation. To me, it was an attractive idea; but few experts have agreed. One objection was that mitochondrial Ca²⁺ uptake occurs only when [Ca²⁺] reaches very high, unphysiological levels. The main consensus, in this disputatious field, is that general anesthetics act by enhancing GABAA receptormediated inhibition. Curiously, albeit well aware of Pavlov’s belief that sleep is produced by a spread of “inhibition” over the cortex, I had not considered increased inhibition as a likely mechanism of anesthesia. Bearing in mind more recent evidence that mitochondria do play a major role in Ca²⁺ homeostasis, even under normal conditions, I still like to believe that activation of Ca²⁺ sensitive GK may contribute to general anesthesia.

Modulation of Synaptic Transmission in Some Afferent Pathways

After spending much time writing a comprehensive review of chemical mechanisms of synaptic transmission (Physiol Rev, 1974), my research interests returned to more peripheral synaptic mechanisms. Still outstanding was the question of the nature of the transmitter at primary afferent synapses. Our earlier observations in the cuneate nucleus suggested glutamate—obviously suitable because of its very strong and brief action. We had also tested another candidate, Substance P (SP), but the SP-containing tissue extract that we applied had no consistent effects. Only a few years later, a peptide extracted from salivary glands and purified by Susan Leeman proved to be SP. So we were now able to repeat iontophoretic tests in the cuneate and spinal cord with the pure compound. This time, there was a clear effect: a slow and prolonged excitation, comparable to ACh’s action, and quite different from the sharp synaptic responses evoked by sensory stimulation. This looked more like a modulator action that could potentiate fast synaptic transmissions, perhaps those involved especially in nociception (as indicated by further observations by my colleague Jim Henry). According to some intracellular recordings, like ACh, SP induced a slow depolarization and rise in membrane resistance, consistent with a block of K⁺ channels. In related experiments, we found no evidence that baclofen was a selective antagonist of SP. In addition, we confirmed previous reports that baclofen strongly depresses monosynaptic transmission in the spinal cord; and also found that it lowered the excitability of motoneurons and raised their membrane conductance. But we failed to realize that baclofen was a selective agonist for the GABAB receptors identified by Norman Bowery 2 years later.

Prolonged after-potentials, a prominent feature of primary afferent synapses, reflect another form of modulation: presynaptic inhibition (originally named by Eccles), which operates by reducing the amount of transmitter released by afferent fibers. One possible physiological function would be to suppress painful inputs, as postulated by Melzack and Wall’s Gate Theory (1965). But how did it operate? One mechanism, GABA-mediated terminal depolarization, had been proposed by Eccles. An alternative (or additional) mechanism was depolarization by K⁺, released from unmyelinated afferent terminals. This intriguing problem led us (Mary Morris and I) to measure extracellular K⁺ accumulations in the spinal cord and the cuneate, using the recently developed K⁺-sensitive microelectrodes. At both sites, clear increases in extracellular [K⁺] followed afferent stimulation. We explored systematically such changes in [K⁺], at different depths in the tissue and as evoked by a variety of types and frequencies of stimulation. The observations could be fitted by a model combining fixed release of K⁺ per impulse with its removal, partly by diffusion to inactive neighboring tissue and partly by uptake by the Na/K pump—the significant role of uptake was revealed more directly by blocking Na/K pump activity with strophantidin. For this modeling, I could indulge in playing with diffusion equations, something that had remained as a hobby from my calculations of diffusion in sciatic nerves, as graduate student. Albeit a satisfying occupation, the modeling took up much time and effort that perhaps could have been better spent in following up experimentally some suggestive leads. At any rate, these data showed a good agreement, over most of their time course, between changes in K⁺ potential and the smaller, prolonged changes in local DC potential. This would be expected if the latter were caused by K⁺-induced depolarization of neurons and/or glia. The fit was good, except for an early mismatch, indicative of another depolarizing mechanism, most likely that of GABA-mediated presynaptic inhibition.

Recordings in Hippocampus In Situ

We turned the page to a new chapter near the end of the 1970s when we started recordings in rats. Hitherto, our studies had always been on cats, but their rapidly increasing costs were becoming prohibitive. Going against the fast growing rush toward slices, with my new colleagues, Y. Ben-Ari (from Paris) and Wolfgang Reinhardt form Germany, we decided to continue experiments on the brain in situ. Ben spent a good while working out how to reach the hippocampus with stimulating and recording electrodes held at sharp angles from the vertical—they had to be angled because the rat’s brain is so small. I believe we were the first to obtain useful intracellular records from the rat’s brain in situ. Focusing on IPSPs and GABA, we found large IPSP conductance increases and even better agreement between the effects of GABA and IPSPs than in our experiments on neocortical neurons. An unexpected feature, however, was that IPSPs rapidly diminished, or even disappeared during repetitive stimulation at frequencies above 5 Hz. This was not simply caused by the change in transmembrane Cl– gradient resulting from Cl– influx because the IPSP conductance change also diminished or vanished. Could GABA (or some other agent) released by stimulation act presynaptically to block further GABA release? Another possibility was suggested by some evidence that GABA applications became less effective—a postsynaptic change, such as receptor desensitization or more rapid removal by uptake. That IPSPs could be so labile was not just an epiphenomenon: it might help to explain why the hippocampus is notoriously susceptible to paroxysmal activity (“seizures”). This form of disinhibition (‘DSI’) long remained mysterious but in the end shown by Roger Nicoll to be mediated by cannabinoid release from the post-synaptic cell.

Acetylcholine also seemed to mediate disinhibition. Acting via both muscarinic and nicotinic receptors, ACh facilitated population spikes, evidently by depressing IPSPs. Could this play a role in the cholinergic component of the theta rhythm, driven by septal input (as reported by Vanderwolf)? When we stimulated repetitively the medial septum, hippocampal population spikes were facilitated—by a mechanism at least partly mediated by ACh, since it was diminished by applying hemicholinium, a blocker of choline uptake and thus of ACh release. Though suggestive, the results were rather variable, possibly owing to activation of the septohippocampal GABAergic fibers later found by Tamas Freund.

In all these experiments, we were joined by Nicole Ropert (recently graduated from Laval University, where she had worked under the supervision of Mircea Steriade). Every scientist is special in his or her own way. Mircea Steriade was more special than most. A native of Romania, his scientific orientation was set for life in Brussels, by visiting Frederic Bremer, whose lifelong interest in sleep physiology and thalamocortical function he inherited. In 1968, he was invited to Canada by Jean-Pierre Cordeau (who planted the seeds for the now flourishing neurosciences at the Université de Montréal). As on all later occasions, I was much impressed by Steriade’s enthusiasm and the polemical vigor with which he spoke about his work. He took up a position at Laval University, in Quebec City, where he remained for the next 40 years, recording from the brain in situ to analyze cortical and thalamic activity and interactions—for decades, it had been one of the main topics of brain research, but it was going out of fashion by the late 1960s.

Albeit increasingly isolated, Steriade refused to give up. Deeply convinced that such complex events as sleep and waking could not be usefully studied in isolated tissues, he never wavered from his focus on brain mechanisms in situ. Only recently did Steriade’s prolific research get its due recognition when consciousness (hitherto taboo) began to be viewed as serious topics of scientific investigation. Steriade’s numerous contributions, and his expertise and deep knowledge, set him at the center activity in this rapidly evolving area of neuroscience—a very happy, satisfying outcome for an exceptionally focused career.

The hippocampus was full of surprises. Not the least were the large changes in extracellular K⁺ and Ca²⁺ that accompany neuronal firing. My colleague Mary Morris having much experience with K⁺- and Ca²⁺-selective microelectrodes, together with our visitor from Edmonton ( Rod Reiffenstein) we began a systematic study of changes in extracellular K⁺ and Ca²⁺ concentrations in hippocampus ([K⁺]o and [Ca²⁺]o, respectively) It was soon obvious that hippocampus differed greatly from the cuneate, where [K⁺]o rose linearly with the frequency of stimulation. In the hippocampus, the changes were far greater and more complex, the rise in [K⁺]o being linear only up to a frequency of 3–4 Hz. At this point cells started firing in bursts, the synaptic potential rapidly diminished, and [K⁺]o jumped to a much higher but stable level near10 mM. The sudden rise in [K⁺]o was always accompanied by a sharp but only transient fall in [Ca²⁺]o. If stimulation was maintained at 5–8 Hz, periodic increases in [K⁺]o and falls in [Ca²⁺]o occurred at intervals of about 30 s. The large changes in [Ca²⁺]o were sharply limited to the pyramidal stratum of CA1, in contrast to the widely distributed increases in [K⁺]o. The large reductions in [Ca²⁺]o, clearly the result of somatic Ca currents activated during busts of firing, were especially interesting. They would limit extracellular Ca²⁺ available for further influx into pyramidal cells and the inhibitory nerve endings, predominant at this level, thus reinforcing the disinhibition seen during repetitive stimulation. All these features of hippocampus indicated an exceptional ability to translate relatively low frequency inputs (in the theta range) into bursts of firing and Ca²⁺ influx that can trigger long-term changes in synaptic efficacy. A less desirable aspect is the limited range of safe operation of this hyperreactive organ, notoriously prone to seizures.

Nonresearch Activities

Thanks to my schooling in Geneva, speaking French came as easily as English. But as my French education stopped with primary school, my vocabulary was rather limited. In contrast, English was the language of all my formal education after the age of 14. Thus, in English, I have a wider vocabulary though somehat less efficient mechanics of speaking—my voice tends to give out toward the end of a lecture or after long conversations.

In French, the articulation comes more easily, but I cannot produce the elaborate sentences of the educated Frenchman. This was somewhat less of a problem in Quebec, where people do not speak like typical Frenchmen. Indeed, the problem—especially during the first years—was more in understanding the local dialect; but, in time, I learned to enjoy its lively, colourful and unpretentious qualities. Large or small, conventional or avant-garde, theaters abound in Montreal. So did new writers, including at least one, Michel Trenblay, as good as any contemporary in the world, as well as several gifted film directors. The Quiet Revolution released much pent-up psychic energy in a vibrant cultural renaissance. There was much to enjoy.

As a Croat, I was naturally sympathetic to the Francophones’ determination to rise out of what they saw as a colonial status. Higher education and research began to flourish, especially in the sciences. Francophones were becoming major achievers even in business—something they’d been viewed as congenitally incapable of doing. I was not convinced, however, that separation from Canada was desirable. Unlike Croatia, Quebec was not subject to a ruthless, all-powerful central government. A great deal of power in Canada has devolved to the provinces—for Quebec, even that of collecting its own taxes. Indeed, had Yugoslavia been as half as decentralized as Canada, it might well still be in existence. At the federal level, the influence of Quebec is quite out of proportion to its population: since 1968, most Canadian prime ministers have come from Quebec. By definition, Canadians are North Americans who did not wish to be U.S. citizens. To survive as an independent nation they need to stay together. In this respect, Canadians are very much like the Swiss—who also wanted to remain separate from powerful neighbors: in spite of the differences in language, religion, and world outlook, the variegated cantons realized that they had to be united. Throughout their history, French Canadians saw the Protestant, English-speaking New Englanders as the greatest threat to their national survival. When, after their revolution, American forces (as well as Franklin) marched to Montreal and urged the French Canadians to join the new Union, they were driven away by the local inhabitants. Curiously, a surprising number of Québécois nationalists now proclaim a greater affinity for Americans than for other Canadians—seemingly oblivious of the fate of large francophone communities in Louisiana and New England.

The fast rise of nationalist feeling, and especially the advent of a separatist Parti Québécois government in 1976, was very disturbing for the “Anglos” of Quebec. Though having spent their lives here, few could converse in French. New rules making French the only official language, restricting the use of English in advertising, and especially forcing children to go to French schools, convinced many thousands of Anglos that there was no future for them in Quebec. Migration to Ontario (or further west, increasingly) soon became a flood. Major firms moved their headquarters to Toronto. Even at McGill, an English (or perhaps more precisely Scottish) bastion when I came in 1964, many of the staff were now leaving. Although language was not a problem for me, I was concerned about my family’s prospects in an independent Quebec—likely to be hyper-nationalist, at least initially (like the new republics born of ex-Yugoslavia). I therefore considered more seriously than usual offers of possible positions elsewhere. One particularly, from the University of Geneva, was very attractive as it might enable us to live near my aging, increasingly ailing mother. Outstandingly active all her life—much devoted to mountaineering and skiing—she was now seriously handicapped by vicious attacks of asthma (from which she was to die in February1980). Our close proximity would be a great comfort to her. But it didn’t work out. While the terms of the Geneva position were under somewhat protracted discussion, Sam Freedman, the new McGill Dean of Medicine asked me to be a candidate for the Chair of Physiology. A distinguished clinician and researcher in oncology, Sam Freedman broke new ground as the first Jewish Dean of a faculty that severely limited the entry of Jewish students before World War II. It was a clear sign of how much McGill was changing after the departure of much of the Anglo establishment.

Why did I accept this heavy responsibility? Mainly because I saw it as a new kind of challenge, at a time when the morale at the University was undergoing a major crisis. The Physiology Department was a large concern. Though Physiology’s budget came from the Dean of Medicine, its main teaching was for the faculty of science, largely because physiology was viewed as a good avenue into medical school. Indeed, so many were enrolled in our first-year course that, at one point, lectures had to be given in a downtown theater. And of course there were medical students, honors students, and over 70 graduate students. Caring for all these was a correspondingly large staff with good strength across the board, from neurophysiology to immunology. Though my own teaching was not very onerous, administration took up a good deal of time. But I protected myself by staying as much as possible on the 12th floor—in Anesthesia Research, where I could get on with my research—rather than in the chairman’s office on the 10th floor. For the first 2–3 years, the Dean, Sam Freedman, was very supportive, accepting my argument that the basic sciences, unlike clinical departments, had no additional sources of funds from wealthy donors or charities. We were able to maintain our small library, seminar series and workshop facilities, and even recruit new staff. Of all my initiatives during those years, probably the most satisfying (and successful) was getting department members to sponsor a Vietnamese “boat people” family. Taking on the responsibility of providing for three adults and four small children meant having to find accommodation, employment for the father, schooling for the children, medical help when needed—all requiring a major collective effort. I like to think that a sense of common purpose helped to reinforce departmental morale at a time of serious political and economic uncertainty.

As university funding was cut deeply, a new dean, Dick Cruess, was appointed with a mandate to reduce spending. We had to further tighten our collective belt—over 7 years, the departmental budget was reduced by one third (allowing for inflation). This made life distinctly less pleasant and members of the department more restive. Nevertheless, in view of the department’s strong performance in teaching and research, the Dean asked me to stay on for a second 5-year term. Convinced that Physiology was thriving, his main concern now was to build up Pharmacology—admittedly by far the smallest basic science department in the Faculty of Medicine.

By the ninth year of my tenure, I felt the need to take a break from the increasingly time-consuming administration. During this first sabbatical leave since my arrival at McGill, I renewed my collaboration with Y. Ben-Ari (ex-postdoc and now good friend), who had taken over an INSERM unit at Port-Royal, in Paris. Having studied hypoxic block of neuronal function in mature hippocampus (as described later), I wanted to repeat the experiments on slices from immature (newborn) rats: — by that time,we were all working on hippocampal slices. For some months, I joined Ben’s group at Port-Royal, where we had access to pups of any age. The team included Enrico Cherubini (descendant of Laerzio Cherubini, the Roman lawyer for whom Caravaggio painted the Louvre’s notorious Death of the Virgin). The experiments went very well. In keeping with the known resistance of human infants to anoxia, compared to mature hippocampus, early postnatal hippocampus was much less sensitive to anoxia. At the end of my sabbatical leave, I decided to go back to full-time research and stepped down from the Chair of Physiology.

What did I achieve as Physiology Chairman? One thing mainly (I like to believe). The department held together and on a more or less even keel through a period of great political uncertainty and financial duress. Despite unfavorable conditions, we attracted some dynamic young scientists— Al Shrier, Ellis Cooper, John Hanrahan, who would fully live up to their promise. And we kept our best senior staff, including Geoffrey Melvill-Jones, a world leader in research on vestibular motor control who had been offered a Wayneflete Chair at Oxford. What I did not do was move the department toward molecular biology—as did my successor, David Goltzman. My own inclination was against an unduly reductionist approach, perhaps owing to an upbringing in medicine and weak grounding in hard science. Inevitably, the wondrous new possibilities offered by molecular and genetic techniques would prove irresistible, especially for younger scientists. But to make sense of the exponentially increasing outpouring and complexity of new information will surely require the more integrative approach favored by physiologists. For that reason, as a discipline, physiology has survived and will continue to thrive, especially in in areas such as neuroscience, where vast amounts of diverse data lend themselves to—indeed are crying out for—a broader synthesis.

Later Years

Though from the very beginning I wanted to bring closer together brain physiology and psychology, for the first decade my research had focused on peripheral structures, and then moved up from nerve and muscle to the spinal cord. Finally, I reached the cortex. I was now closer to the site of the mind-brain boundary—where consciousness is somehow generated. When we found that ACh makes cortical neurons more responsive to incoming signals, we proposed that this might be the cellular basis for consciousness. Though not a breakthrough, it was a useful advance. Another aspect of consciousness, perhaps even more fascinating, is that it is so easily but reversibly suppressed pharmacologically, notably by general anesthetics. Even if the “mind” can exist independently of the brain—a question for which one can foresee no definitive answer—its expression in consciousness is “mediated” by brain circuits that are highly susceptible to chemical manipulation. Some of our findings suggested interesting possibilities. If agents such as dinitrophenol can block the action of ACh in the cortex, apparently by raising cytoplasmic [Ca²⁺] and activating K⁺ channels, might not anesthetics operate in a comparable manner?

More recently, I tried to answer a related question: how does brain anoxia (or ischemia) so rapidly abolish consciousness? Humans subjected to temporary brain ischemia become unconscious within some 20 seconds. How is this reflected at the level of brain cells and synapses? An obvious target for searching study was the hippocampus, known to be one of the first portions of the brain to be affected by anoxia. Recording in vitro, from hippocampus in brain slices, under optimal conditions for stable intracellular recordings—with the possibility of analyzing membrane currents under voltage-clamp—surely we should soon find out precisely how anoxia produces such a rapid loss of function. It didn’t work out quite that way.

My latest postdoctoral fellow Jean Leblond—a psychology Ph.D. from Université Laval (in Quebec City)—also happened to be my first francophone Quebecois collaborator. A bright, mildly pudgy young man, with a pawky sense of humor, he never felt quite at home in very cosmopolitan Montreal—on Monday mornings, he would come by bus from Quebec city (a 3–4 hour ride) and return home every Friday afternoon. But he cut good slices. Our main problem was making “sharp” microelectrodes, fine enough to penetrate the cells but not having such high resistance as to preclude voltage-clamping. Danish investigators had found that anoxia induced an early hyperpolarization,which they attributed to a rise in K⁺ conductance, as well as block of synaptic transmission. We confirmed these observations, which supported the idea that block of respiration induces Ca²⁺ release from mitochondria and activation of Ca²⁺-sensitive K⁺ channels. But K⁺ channels might be activated, equally plausibly, by another intracellular signal, a drop in cytoplasmic ATP level. This mechanism of GK activation had been discovered in the heart by Noma, 5–6 years earlier. Such KATP channels might well be present in hippocampal neurons. Over the next few years, we (and others) tested various pharmacological blockers of KATP channels, with conflicting results. After many experiments—in which I was joined by several excellent collaborators, including Gül Eredmli (from Ankara), Andrei Beloussov (from Moscow), Yao-Zhong Xu (from Hefei) and, Jean-Marie Godfraind (still a regular visitor from Brussels)—we concluded that the K⁺ channels activated by hypoxia, being G protein dependent and blocked by both ACh and isoprenaline, were predominantly of the Ca²⁺-activated slow AHP type; and most likely not adenosine-activated K⁺ channels though adenosine was largely responsible for the hypoxic block of synaptic transmission. As is so often the case, the simple picture I originally had in mind turned out to be far murkier than I expected; though overall in keeping with the idea that the cellular response to loss of energy supply is to minimize energy expenditure (as emphasized by Peter Hochachka). In the brain, this is achieved by a rapid block of neuronal firing and synaptic activity on which conscious perception depends.

China and Chinese Colleagues

By the mid 1980’s, graduate students and postdocs began to come from China. The first, Liang Zhang (from Wuhan), was a prodigiously hardworking student. Of an unusually cheerful disposition, Liang was highly articulate in English, but almost impossible to understand. This was to be a recurrent problem with Chinese students who, in China, are practically never exposed to English spoken by non-Chinese. How different from most European countries. In Croatia, very impressed by the excellent English spoken by all my young relatives, I commented on the efficiency of their English teachers at school. In fact, from an early age they had learned English watching and hearing American and British programs on television. Here was a lesson for China, where such programs are invariably dubbed in Chinese.

YaoZhong Xu, and I met by chance in Dubrovnik. On leave in Italy (from the USTC, in Hefei), he had come from Trieste to attend the Summer school in Biophysics (superbly organized by Greta Pifat, of the Rudjer Bošković Institute). Quite unlike my other Chinese visitors, Xu was a bon-vivant. He had traveled to all parts of Italy and admired the sites and cities, noting the beauty of the women and the excellence of the cuisines—most of all he appreciated the unhurried lunches. Perhaps he was making up for his exile to Inner Mongolia during the Cultural Revolution though even in Mongolia, ever adapting to circumstance, he found a wife, and enjoyed riding on ponies. Xu spent a year with me in Montreal and later arranged my three visits to China (in 1991, 2001, and 2003). In 1991, the first 2 days Jeanne and I were hosted by T. P. Feng at the Shanghai Institute of Physiology.

China’s leading neurobiologist, in prewar years Feng had worked in Chicago with R. W. Gerard and in London with A. V. Hill. He returned to China and set up a very productive laboratory in Shanghai. He survived the great upheavals of the war years, the Maoist takeover, and the Cultural Revolution but was unable to do much science until he was reestablished as Director of Research at the Academy in Shanghai. Being familiar with his many publications—first, on the nerve sheath, and later on end-plate potentials (in Canberra, Eccles had all Feng’s reprints from the Chinese Journal of Physiology)—I was delighted to make his acquaintance when he visited North America in the early 1980s. In Shanghai, I met two other Chinese scientists who in their youth had also worked overseas, H. C. Chang at Mill Hill with John Gaddum (my mentor at Babraham), and H. T. Chang, who was a dynamic CNS researcher at Yale and the Rockefeller Institute until the mid-1950s, when he returned to China. At the time of my first visit (1991), the streets of Shanghai were clogged with cyclists, undisturbed by cars. Owing to power shortage, there was no electricity after 10 a.m. By 2001, Shanghai was almost unrecognizable. Cars had replaced the bicycles. Whole quarters were being razed to make room for large office and apartment buildings. And the unremarkable view across the Huang-Po River had turned into a forest of skyscrapers (as architecture, mostly uninspiring, but nonetheless eye-catching). China’s stupendous growth is hardly news to anyone nowadays, but seeing it firsthand made a deep impression.

In 2003, I spent a month in Hefei, lecturing as visiting professor. Apart from the ever denser and more chaotic traffic, much was changing, even in a relatively small provincial town (by Chinese standards, but nonetheless with 1 million inhabitants). For example, a major intersection was blocked for several days by a “sit-down” strike of civil servants, calmly watched by policemen redirecting the traffic. A few years earlier, even such a peaceful demonstration would not have been tolerated. One weekend, I was driven to a much smaller town, in southernmost Anhui province to visit the new middle school opened by an enterprising Mrs. Wong. I was taken from class to class to address the bemused children who had never heard an English-speaking foreigner. So in communist China, just as in capitalist countries, parents were happy to pay high fees to have their children go to a private school. In spite of the apparently unyielding politics of its government, Chinese society (not just the economy) was rapidly evolving. Some other vivid memories from China come to mind: in Inner Mongolia, a Tibetan style Buddhist monastery, Genghis Khan’s putative tomb, a lavish feast (including camel hooves) in a yurt, and sliding down huge sand dunes. In Xian, an extraordinary mosque complex, architecturally in pure Chinese style; and much else.

My next visitor from China, Yanguo Hong was also old enough to have lived through the Cultural Revolution. He was exiled to a remote mountainous area where, as physician, he had an exhausting time traveling up and down steep hillside tracks. Then came PingJun Zhu. Originally from Hangzhou, he was studying cardiac electrophysiology at the Université de Montréal, but decided he wanted to work with me on hippocampus. At first, I was very reluctant, not wishing to “steal” him from his PhD supervisor, but he was very insistent. Tall and cadaverous—despite vast quantities of dumplings prepared by himself and consumed at lunchtime—he was a really serious worker. His research on the protective actions of glucose and adenosine against irreversible brain damage was very productive. As a postdoctoral researcher, he (and his very lively wife and little daughter) moved to the United States. Curiously, we quite recently again became collaborators (at long distance, as mentioned in the next section). My last Chinese student, Yong-Tao Zhao, was untypically keen on athletics, including tennis. Albeit successful in some very difficult experiments, his heart was not in research. He left after only one year.

The Turkish Connection

Of all my “connections” the richest has been that with France. I was fortunate to have as visitors such gifted scientists as Anne and Paul Feltz, René Pumain, Yehezkel Ben-Ari, Yvon Lamour, Nicole Ropert, and Jean-Louis Bossu (in chronological order). Another connection, with Turkey, was more fortuitous. How did it come about? In a very roundabout manner, via an IBRO Workshop held in 1974 at the Pahlavi Medical School in Shiraza delightful town graced by the finest bazaar and most colorful domes imaginable, Participants were invited from all countries in the region (under the Shah’s enlightened rule, even Israel!). Two came from Turkey, including the pharmacologist Ogűz Kayaalp from Ankara. Though I did not see Kayaalp again till some decades later, in 1981 he wrote to me from Hacettepe University (Ankara), strongly recommending for a postdoc position his ex-student Turgay Dalkara, a research-oriented neurologist. An ardent nationalist—like all his compatriots—Turgay was a most pleasant collaborator. Our studies (with Conrad Yim, a Canadian Chinese) on hippocampus in situ revealed striking ephaptic interactions between the closely apposed pyramidal cells. Such mutual reinforcement of synchronized excitation would facilitate network oscillations and seizures—both characteristic features of hippocampus.

Another ‘Turkish’ student, Nadia Agopyan, though born in Istanbul, was really Armenian. An exuberant personality, she later had an exciting postdoctoral career. First, one year in Japan, with N. Akaike (in Sendai); her uninhibited laughter, as well as disparaging comments about malechauvinist treatment of women employees made a great impression. Her second postdoc year—now accompanied by her husband Peter Miu (also my graduate student)—in Sackmann’s laboratory in Heidelberg, became equally memorable when she installed their very young baby in a corner of the lab.

After this they returned to North America. The next arrival from Turkey, Gűl Erdemli, was recommended by Turgay Dalkara. She took the torch from Jean Leblond, continuing the investigations on membrane currents induced or altered by hypoxia in hippocampal slices. My appreciation of Turkey became even stronger when Turgay organized a symposium on brain ischemia in Urgűb (Cappadocia). After the meeting, driving from Urgűb via Konya to the Mediterranean, and then, mainly along the coast to Izmir, I discovered a country immensely rich in different landscapes and ancient monuments, remnants of Greek and Roman Ionia, and the long-enduring Byzantine and Ottoman empires.

My Turkish connection ended with my last graduate student, Selva Tekkök, another medical graduate of Hacettepe University. Her experiments on the effects of glucose deprivation on synaptic transmission, also in hippocampal slices, took an unexpected turn when she discovered a curious, unsuspected manifestation of synaptic plasticity. Substituting glucose with 2-deoxyglucose (2-DG, a nonmetabolized derivative) for 10-20 min resulted in block of synaptic transmission—as expected—but when glucose was reapplied, the return of synaptic transmission was invariably followed by a pronounced and long-sustained rebound of EPSP amplitude. This intriguing, long-term potentiation (LTP)-like phenomenon was of interest, as the only form of LTP induced by blocking metabolism at a precisely known step in the glycolytic pathway. Though readily taken up by cells and phosphorylated, unlike glucose 2-DG is not further metabolized and just accumulates in the cells (hence its well-known use as an index of glucose uptake). For Selva, this topic had the advantage of being quite new and therefore wide open for all kinds of investigations, with no competition to worry about. Albeit having no obvious physiological relevance, 2-DG has been proposed for the treatment of a variety of disorders , including obesity, viral infections, malignant tumors and parkinsonism. Its potential effects on learning and memory may have a wider significance.

The Postretirement Years

At my retirement in 2000, I stepped down after heading Anesthesia Research for 35-years. Though sometimes referred to as “anesthetic research” or, more seriously, criticized for insufficient relevance to clinical anesthesia, it had been a thriving, highly productive operation. “Curiosity-driven” research, in neurosciences as in other fields, often throws new light on old issues and practices. In this manner, basic research supplies new tools for improvements in clinical practice. This truism cannot be overemphasized, especially now that “translational” research has become the latest fad, forcefully promoted by university administrations and granting agencies.

Two stressful events marked the first decade of my retirement. After 40 years in a relatively large house on Belmont Avenue, we moved to a much smaller apartment, more appropriate for two “retirees.” Having to deal with huge amounts of material (especially books), accumulated over four decades, was physically draining and psychologically traumatic. Parting with books is always hard; with so many, it was devastating. But we managed to keep a good number and survived.

Naturally, I had to vacate Anesthesia Research to make room for Fernando Cervero, my able successor. An expert on nociception, he established a busy center for basic research on pain. I was given an office nearby, on the 12th floor. But there was not enough space for long shelves full of scientific journal, as well as rows of filing cabinets, brimful with experimental protocols and data, reprints, and correspondence Having to throw out so many precious, handsomely bound journals was distressing, but only a temporary hindrance: journals becoming increasingly available on the Internet, regular visits to the library were no longer necessary. Neither was a secretary, as, at first tentatively and laboriously, I learnt how to use a word processor. At any rate, as emeritus, I had an office. Conveniently next door, in Pharmacology, my Croatian colleague Ante Padjen had his office and laboratory. Also born in Zagreb, Ante was much involved in Croatian expatriate affairs. We were both members of an association of alumni of Zagreb University (in my case, as honorary member); and also an International Croatian Initiative (whose aim, during the Tudjman years, was to promote democracy in Croatia). We both also had a life-long interest in music (in his case expressed more tangibly by creating a medical faculty orchestra, I Medici di McGill). Ante allowed me to move some of my old equipment into a corner of his shielded room. This was the site of my last “hands-on” experiments and also of my first close encounter with transgenic mice. Jasna Križ, my only Croatian collaborator, was an ex-Ph.D. student of Ante’s and was now working with Jean-Pierre Julien. They had produced mice overexpressing peripherin—an intermediate filament, apparently involved in some neurodegenerative conditions. In these mutants, could high levels of peripherin in the hippocampus be reflected in altered synaptic transmission? We recorded synaptic responses in hippocampal slices, from many mutants and control littermates, but found only some changes in the magnitude of LTP. Curiously, they were opposite in direction in CA1 and CA3.

My continued involvement in research, albeit still quite deep and time consuming, is no longer at first hand, but rather as advisor in planning experiments, interpreting data, and writing up papers or grant applications. My main collaborators, both leaders of very active groups, have kept me quite busy. The first was Jiang-Hong Ye (at the New Jersey Medical School)—a native of Guandong, whom I had met in Akaike’s lab in Japan. His research has focused on synaptic transmission in the dopaminergic, reward pathway—generally believed to mediate drug addictions—in particular modulation of transmission by strychnine-sensitive actions of glycine and taurine and some unsuspected presynaptic effects of ethanol.

My second ongoing collaborator, Mauro Costa-Mattiol, an exceptionally gifted and dynamic young scientist, was born in Uruguay. Having obtained his PhD at the University of Nantes, he spent several years at McGill as postdoctoral fellow in the laboratory of Nahum Sonenberg (at McGill), a world expert on the hugely complex mechanisms of RNA translation. Further exploring the functional role of the translation initiation factor eIF2α, they studied transgenic mice deficient in GCN2—a kinase which phosphorylates eIF2α. To their surprise, these mice were able to learn and memorize more efficiently than control littermates. In hippocampal slices from the mutants, the threshold for sustained LTP was also lowered. These findings seemed paradoxical, because activation of eIF2α suppresses general translation, which would prevent the synthesis of new protein(s) known to be essential for sustained LTP and for behavioral memory. The explanation is that phosphorylated eIF2α activates ATF4, a repressor of CREB, a transcription factor involved in learning. Hence, in mutants lacking GCN2, reduced phosphorylation of eIF2α removes the inhibition of CREB by ATF4, thus facilitating learning. The pivotal role of eIF2α phosphorylation was confirmed in the second phase of the project in which increasing or reducing eIF2α phosphorylation elicited the expected bidirectional changes in learning. My own contribution to this vast project lay in almost daily discussions with Mauro over the interpretation and writing up of a great variety f data. Although Mauro is now in Houston, at the Baylor College of Medicine our ongoing discussions have continued by email or telephone. A series of exciting new findings by Mauro and my ex-student Ping Jin Zhu have revealed a quite unexpected function of PKR—another eIF2α-related kinase—as regulator of GABAergic inhibition, probably acting through interferon-γ. Perhaps most surprising is that mutants lacking PKR are prone to mild electrographic seizures; but they perform better than littermates in tests of learning and long-term memory. A fascinating example of the anything but simple interactions between molecular, cellular and cognitive function.These forays into large-team research—so different from my own life-long practice—have been hugely instructive. I learned that I was still capable of learning, which was personally satisfying but of no great consequence. More important was seeing, so to speak at first hand, both the extraordinary power of molecular genetics and the awe-inspiring, seemingly unfathomable complexity of living matter. It is encouraging to know that so much can be done at last to narrow the gap between cognition and brain physiology and biochemistry. However, to achieve this, large teams and abundant funds have become essential—a situation not unlike that of physics, to which biology has long been aspiring. As members of such teams, individual researchers tend to become narrowly specialized and have fewer opportunities for personal initiative. Can they have the all-consuming attachment to their work, characteristic of many researchers of my generation? If research becomes a 9-to-5 occupation, albeit beneficial for family life, it will be very different. The future, like the past, is a foreign country.

Selected Bibliography

Peripheral Nerves

Krnjević, K. (1952) The perfusion of the frog sciatic nerve with electrolyte solutions. J. Physiol. 18, 3–4P.

Krnjević, K. (1954) Some observations on perfused frog sciatic nerves. J. Physiol. 123, 338–56.

Krnjević, K. (1954) The connective tissue of the frog sciatic nerve. Q. J. Exp. Physiol. 39, 55–72.

Dainty, J., & Krnjević, K. (1955) The rate of exchange of 24Na in cat nerves. J. Physiol. 128, 489–503.

Krnjević, K., Aungle P.G., & Kilpatrick, R. (1955) A study of some aspects of nervous and muscular activity during experimental human salt deficiency. Q. J. Exp. Physiol. 40, 203–216.

Spinal Cord

Curtis, D.R., Krnjević, K., & Miledi, R. (1958) Crossed inhibition of sacral motoneurones. J. Neurophysiol. 21, 318–326.

Eccles, J.C., & Krnjević, K. (1959) Potential changes recorded inside primary afferent fibres within the spinal cord. J. Physiol. 149, 250–273.

Eccles, J.C., & Krnjević, K. (1959) Presynaptic changes associated with post-tetanic potentiation in the spinal cord. J. Physiol. 149, 274–287.

Phrenic-Diaphragm

Krnjević, K., & Miledi, R. (1958) Motor units in the rat diaphragm. J. Physiol. 140, 427–439.

Krnjević, K., & Miledi, R. (1958) Some effects produced by adrenaline upon neuromuscular propagation in rats. J. Physiol. 141, 291–304.

Krnjević, K., & Miledi, R. (1958) Failure of neuromuscular propagation in rats. J. Physiol. 140, 440–461.

Krnjević, K., & Miledi, R. (1958) Acetylcholine in mammalian neuromuscular transmission. Nature Lond. 182, 804–806.

Krnjević, K., & Miledi, R. (1959) Presynaptic failure of neuromuscular propagation in rats. J. Physiol. 149, 1–22.

Krnjević, K., & Mitchell, J.F. (1960) The release of acetylcholine in the isolated rat diaphragm. J. Physiol. 155, 246–262.

Krnjević, K., & Mitchell, J.F. (1960) Diffusion of acetylcholine in agar gels and in the isolated rat diaphragm. J. Physiol. 153, 562–572.

Hebb, C.O., Krnjević, K., & Silver, A. (1964) Acetylcholine and choline acetyltransferase in the diaphragm of the rat. J. Physiol. 171, 504–513.

Krnjević, K., & Straughan, D.W. (1964) The release of acetylcholine from the denervated rat diaphragm. J. Physiol. 170, 371–378.

Neurotransmitters in the Central Nervous System

Krnjević, K., & Phillis, J.W. (1963) Actions of certain amines on cerebral cortical neurones. Br. J. Pharmacol. 20, 471–490.

Krnjević, K. (1964) Micro-iontophoretic studies on cortical neurons. Int. Rev. Neurobiol. 7, 41–98.

Krnjević, K. (1965) Transmitters in the cerebral cortex. Lectures & Symposia. XXlll Int. Physiol. Congr. (Tokyo) pp. 435–443.

Krnjević, K. (1965) Action of drugs on single neurones in the cerebral cortex. 1965. Brit. Med. Bull. 21, 10–14.

Krnjević, K. (1970) Central excitatory transmitters in vertebrates. In Excitatory Synaptic Mechanisms. Eds. P. Andersen & J.K.S. Jansen. Oslo: Universitetsforlaget, pp. 95–104.

Krnjević, K. (1971) Microiontophoresis. In Methods of Neurochemistry. Ed. R. Fried. New York: Marcel Dekker, pp. 129–172.

Acetylcholine and Consciousness

Krnjević, K., & Phillis, J.W. (1961) Sensitivity of cortical neurons to acetylcholine. Experientia 17, 469.

Hebb, C.O., Krnjević, K., & Silver, A. (1963) Effect of undercutting on the acetylcholinesterase and choline acetyltransferase activity in the cat’s cerebral cortex. Nature Lond. 198, 692.

Krnjević, K., Mitchell, J.F., & Szerb, J.C. (1963) Determination of iontophoretic release of acetylcholine from micropipettes. J. Physiol. 165, 421–436.

Krnjević, K., & Phillis, J.W. (1963) Acetylcholine-sensitive cells in the cerebral cortex. J. Physiol. 166, 296–327.

Krnjević, K., & Phillis, J.W. (1963) Pharmacological properties of acetylcholine sensitive cells in the cerebral cortex. J. Physiol. 166, 328–350.

Krnjević, K., & Silver, A. (1965) A histochemical study of cholinergic fibres in the cerebral cortex. J. Anat. 99, 711

Krnjević, K., & Silver, A. (1966) Acetylcholinesterase in the developing forebrain. J. Anat. 100, 63–89.

Krnjević, K., Pumain, P., & Renaud, L. (1971) The mechanism of excitation by acetylcholine in the cerebral cortex. J. Physiol. 215, 247–268.

Krnjević, K., & Reinhardt, W. (1979) Choline excites cortical neurons. Science 206, 1321–1323.

Krnjević, K. (1981) Acetylcholine as modulator of amino-acid mediated synaptic transmission. In The Role of Peptides and Amino Acids as Neurotransmitters. Progress in Clinical and Biological Research, Vol. 68. Eds. J.B. Lombardini & A.D. Kenny. New York: Alan R. Liss, Inc., pp. 127–141.

Krnjević, K. (1965) Cholinergic innervation of the cerebral cortex. In Studies in Physiology (presented to John C. Eccles). Eds. D.R. Curtis, & A.K. McIntyre. Berlin: Springer Verlag, pp. 144–151.

Krnjević, K. (1969) Central cholinergic pathways. Fedn. Proc. 28, 113–120.

Krnjević, K. (1988) Central cholinergic transmission: the physiological evidence. In The Cholinergic Synapse. Ed. V.P. Whittaker. Berlin: Springer-Verlag, pp. 633–662.

Krnjević, K. (1993) Central cholinergic mechanisms and function. Progress Brain Res. 98, 285–292.

Krnjević, K. (2004) Synaptic mechanisms modulated by acetylcholine in cerebral cortex. Progr. Brain Res. 145, 81–93.

Amino Acids

Krnjević, K., & Phillis, J.W. (1963) Iontophoretic studies of neurones in the mammalian cerebral cortex. J. Physiol. 165, 274–304

Krnjević, K., Randić, M., & Siesjö, B. (1965) Cortical CO₂ tension and neuronal excitability. J. Physiol. 176, 105–122.

Krnjević, K., & Whittaker, V.P. (1965) Excitation and depression of cortical neurones by brain fractions released from micropipettes. J. Physiol. 179, 298–322.

Galindo, A., Krnjević, K., & Schwartz, S. (1967) Micro-iontophoretic studies on neurones in the cuneate nucleus. J. Physiol. 192, 359–377.

Galindo, A., Krnjević, K., & Schwartz, S. (1968) Patterns of firing in cuneate neurones and some effects of Flaxedil. Exp. Brain Res. 5, 87–101.

Krnjević, K. (1970) Glutamate and γ-aminobutyric acid in brain. Nature Lond. 288, 119–124.

Krnjević, K., Reiffenstein, R.J., & Silver, A. (1970) Chemical sensitivity of neurones in long-isolated cortical slabs of cat cerebral cortex. Electroenceph. clin. Neurophysiol. 29, 269–282.

Krnjević, K. (1992) Amino-acid transmitters. Citation Classic Commentary. Current Contents, 35, 11.

Krnjević K. (2010) When and why amino acids? J. Physiol. 588, 33–44.

GABA and Inhibition

Krnjević, K., Randić, M., & Straughan, D.W. (1966) An inhibitory process in the cerebral cortex. J. Physiol. 184, 16–48.

Krnjević, K., Randić, M., & Straughan, D.W. (1966) Nature of a cortical inhibitory process. J. Physiol. 184, 49–77.

Krnjević, K., & Schwartz, S. (1966) Is γ-aminobutyric acid an inhibitory transmitter? Nature Lond. 211, 1372–1374.

Krnjević, K., & Schwartz, S. (1967) The action of γ-aminobutyric acid on cortical neurones. (with S. Schwartz). Exp. Brain Res. 3, 320–336.

Kelly, J.S., Krnjević, K., Morris, M.E., & Yim, G.K.W. (1969) Anionic permeability of cortical neurones. Exp. Brain Res. 7, 11–31.

Dreifuss, J.J., Kelly, J.S., & Krnjević, K. (1969) Cortical inhibition and γ-aminobutyric acid. Exp. Brain Res. 9, 137–154.

Kelly, J.S., & Krnjević, K. (1969) The action of glycine on cortical neurones. Exp. Brain Res. 9, 155–163.

Krnjević, K., Reiffenstein, R.J., & Silver, A. (1970) Inhibition and paroxysmal activity in long-isolated cortical slabs. Electroenceph. clin. Neurophysiol. 29, 283–294.

Krnjević, K., & Puil, E. (1976) Electrophysiological studies on actions of taurine. In Taurine. Ed. R. Huxtable & A. Barbeau, New York: Raven Press, pp. 179–189.

Krnjević, K. (1976) Inhibitory action of GABA and GABA mimetics on vertebrate neurones. In GABA in Nervous System Function. Eds. E. Roberts, T.N. Chase, & D.B. Tower. New York: Raven Press, pp. 269–28l.

Fox, S., Krnjević, K., Morris, M.E., Puil, E., & Werman, R. (1978) Action of baclofen on mammalian synaptic transmission. Neuroscience 3, 495–515.

Ben-Ari, Y., Krnjević, K. & Reinhardt, W. (1979) Hippocampal seizures and failure of inhibition. Can. J. Physiol. Pharmacol. 57, 1462–1466.

Constanti, A., Krnjević, K., & Nistri, A. (1980) Intraneuronal effects of inhibitory amino acids. Can. J. Physiol. Pharmacol. 58, 193–204.

Ben-Ari, Y., Krnjević, K., Reiffenstein, R.J., & Reinhardt, W. (1981) Inhibitory conductances changes and action of γ-aminobutyrate in rat hippocampus. Neuroscience 6, 2445–2463.

Krnjević, K. (1982) Loss of synaptic inhibition as a cause of hippocampal seizures. In Physiology & Pharmacology of Epileptogenic Phenomena. Eds. M.R. Klee, H.D. Lux, & E-J. Speckman. New York: Raven Press, pp. 123–130.

Krnjević, K. (1984) Some functional consequences of GABA uptake by brain cells. Neurosci. Letts. 47, 283–287.

Krnjević, K. (1990) Role of neurotransmitters in the genesis of epileptiform discharges. In Generalized Epilepsy. Neurobiological Approaches. Eds. M. Avoli, P. Gloor, G. Kostopoulos, & R. Naquet. Boston, Birkhäuser, pp. 86–101.

Krnjević, K. (2004) How does a little acronym become a big transmitter? Biochem. Pharmacol. 68, 1549–1555.

Lorenzo L-E., & Krnjević K, (2010) GABA and movement disorders. In: K. Kompoliti & L. Verhagen (eds). Encyclopedia of Movemnent Disorders. Oxford: Academic Press, vol. 1, pp. 517–525.

More General Reviews and Articles

Krnjević, K. (1974) Chemical nature of synaptic transmission in vertebrates. Physiol. Rev. 54, 418–540.

Krnjević, K. (1981) Transmitters in motor systems. In Handbook of Physiology, Section 1, Vol. II, L. Ed. V.B. Brooks. American Physiological Society Press: Bethesda, MD,, Chapter 4, pp. 107–154.

Krnjević, K. (1982) Too much of a good thing? Guest Editorial. IBRO News 10, 1–2.

Krnjević, K. (1984) Physiological actions of multiple transmitters. In Coexistence of Neuroactive Substances in Neurons. Eds. V. Chan-Palay & S.L. Palay. New York: John Wiley & Sons, Inc., pp. 363–377.

Krnjević, K. (1984) The Michel Sarrazin Lecture. Travels in Physiology. Canada Physiology 15, 58–64.

Krnjević, K. (1986) The future of neuroscience. Clin. Investig. Medicine 9, 296–300.

Acetylcholine in Hippocampus

Krnjević, K., Reiffenstein, R.J., & Ropert, N. (1981) Disinhibitory action of acetylcholine in the rat’s hippocampus: extracellular observations. Neuroscience 6, 2465–2474.

Ben-Ari, Y., Krnjević, K., Reinhardt, W., & Ropert, I. (1981) Intracellular observations on the disinhibitory action of acetylcholine in the hippocampus. Neuroscience 6, 2475–2484.

Krnjević, K., & Ropert, N. (1982) Electrophysiological and pharmacological characteristics of facilitation of hippocampal population spikes by stimulation of the medial septum. Neuroscience 7, 2165–2183.

Glavinović, M., Ropert, N., Krnjević, K., & Collier, B. (1983) Hemicholinium impairs septo-hippocampal facilitatory action. Neuroscience 9, 319–330.

Rovira, C., Ben-Ari, Y., Cherubini, E., Krnjević, K. & Ropert, N. (1983) Pharmacology of the dendritic action of acetylcholine and further observations on the somatic disinhibition in the rat hippocampus in situ. Neuroscience 8, 97–106.

Krnjević, K., Ropert, N., & Casullo, J. (1988) Septo-hippocampal disinhibition. Brain Res. 438, 182–192.

Substance P

Krnjević, K., & Morris, M.E. (1974) An excitatory action of Substance P on cuneate neurones. Can. J. Physiol. Pharmacol. 52, 736–744.

Henry, J.L., Krnjević, K., & Morris, M.E. (1975) Substances P and spinal neurones. Can. J. Physiol. Pharmacol. 53, 423–432.

Krnjević, K. (1977) Effects of Substance P on central neurones in cats. In Substance P. Eds. U.S. von Euler & B. Pernow. New York, Raven Press, pp. 217–230.

Krnjević, K., & Lekić, D. (1977) Substance P selectively blocks excitation of Renshaw cells by acetylcholine. Can. J. Physiol. Pharmacol. 55, 958–961.

Ca²⁺ on Neuronal Excitability

EXTRACELLULAR CA²⁺

Kelly, J.S., Krnjević, K., & Somjen, G. (1968) Divalent cations and electrical properties of cortical cells. J. Neurobiol. 1, 197–208.

Krnjević, K., Lamour, Y., MacDonald, J.F., & Nistri, A. (1978) Motoneuronal after potentials and extracellular divalent cations. Can. J. Physiol. Pharmacol. 56, 516–520.

Krnjević, K., Lamour, Y., MacDonald, J.F., & Nistri, A. (1979) Depression of monosynaptic excitatory postsynaptic potentials by Mn²⁺ and Co²⁺ in cat spinal cord. Neuroscience 4, 1331–1339.

Krnjević, K., Lamour, Y., MacDonald, J.F., & Nistri, A. (1979) Effects of some divalent cations on motoneurones in cats. Can. J. Physiol Pharmacol. 57, 944–956.

CYTOPLASMIC CA²⁺

Godfraind, J.M., Krnjević, K., & Pumain, R. (1970) Unexpected features of the action of dinitrophenol on cortical neurones. Nature Lond. 228, 562–564.

Godfraind, J.M., Kawamura, H., Krnjević, K., & Pumain, P. (1971) Actions of dinitrophenol and some other metabolic inhibitors on cortical neurones. J. Physiol. 215, 199–222.

Feltz, A., Krnjević, K., & Lisiewicz, A. (1972) Intracellular free Ca²⁺ and membrane properties of motoneurones. Nature New Biol. 237, 179–181.

Krnjević, K., & Lisiewicz, A. (1972) Injection of Ca²⁺ into spinal motoneurones. J. Physiol. 225, 363–390.

Krnjević, K., Puil, E., & Werman, R. (1975) Evidence for Ca²⁺ -activated K⁺ conductance in cat spinal motoneurons from intracellular EGTA injections. Can. J. Physiol. Pharmacol. 53, 1214–1218.

Krnjević, K., Puil, E., & Werman, R. (1976) Intracellular Mg²⁺ increases neuronal excitability. Can. J. Physiol. Pharmacol. 54, 73–77.

Krnjević, K., & Van Meter, W.G. (1976) Cyclic nucleotides in spinal cells. Can. J. Physiol. Pharmacol. 54, 416–421.

Krnjević, K. (1977) Control of neuronal excitability by intracellular divalent cations: a possible target for neurotransmitter actions. In Neurotransmitter Function: Basic and Clinical Aspects. Ed. W.S. Fields. Symposia Specialists, Miami, Fla, pp. 11–26.

Krnjević, K., Puil, E., & Werman, R. (1978) Significance of 2,4-dinitrophenol action on spinal motoneurons. J. Physiol. 275, 225–239.

Krnjević, K., Lamour, Y., MacDonald, J.F., Nistri, A., Puil, E., & Werman, R. (1979) Intracellular divalent cations and neuronal excitability. Can. J. Physiol. Pharmacol 57, 957–972.

Zhang, L., & Krnjević, K. (1986) Effects of 4-aminopyridine on the action potential and after-hyperpolarization of cat spinal motoneurons. Can. J. Physiol. Pharmacol. 64, 1402–1406.

Zhang, L., & Krnjević, K. (1987) Apamin depresses selectively the after hyperpolarization of cat spinal motoneurons. Neurosci. Letts. 74, 58–62.

Zhang, L., & Krnjević, K. (1988) Intracellular injection of Ca²⁺ chelator does not affect spike repolarization of cat spinal motoneurons. Brain Res. 462, 174–180.

Mechanisms of Anesthesia

Krnjević, K. (1974) Central actions of general anaesthetics. In Molecular Mechanisms in General Anaesthesia. Ed. M.J. Halsey, R.A. Miller, & J.A. Sutton. New York: Churchill Livingston Press, pp. 65–89.

Krnjević, K. (1975) Is general anaesthesia induced by neuronal asphyxia? In Molecular Mechanisms of Anaesthesia, Progress in Anaesthesiology, Vol. L. Ed. B.R. Fink, New York: Raven Press, pp. 93–98.

Krnjević, K., & Morris, M.E. (1976) Input-output relation of transmission through cuneate nucleus. J. Physiol. 257, 791–815.

Krnjević, K. (1986) Cellular and synaptic effects of general anesthetics. In Molecular and Cellular Mechanisms of Anesthetics. Eds S.H. Roth & K.W. Miller. New York: Plenum Press, pp. 3–16.

Krnjević, K., & Puil, E. (1988) Halothane suppresses slow inward currents in hippocampal slices. Can. J. Physiol. Pharmacol. 66, 1570–1575.

Krnjević, K. (1992) Cellular and synaptic actions of general anaesthetics. In Neural Mechanisms of General Anaesthesia. Ed. W. Winlow. Gen. Pharmacol. 23, 965–975.

Krnjević, K., & Puil, E. (1997) Cellular mechanisms of general anesthesia. In Principles of Medical Biology; Molecular and Cellular Pharmacology, Vol. 8A. Eds. E.E. Bittar & N. Bittar. New York: JAI Press, pp. 811–882.

Li, K.Y., Guan, Y.Z., Krnjević, K., & Ye, J.H. (2009) Propofol facilitates glutamatergic transmission to neurons of the ventrolateral preoptic nucleus. Anesthesiology 111, 1271–1278.

Extracellular [K] and [Ca] in Central Nervous System In Situ

PRIMARY AFFERENT SYNAPSES

Krnjević, K., & Morris, M.E. (1972) Extracellular K⁺ activity and slow potential changes in spinal cord and medulla. Can. J. Physiol Pharmac. 50, 1214–1217.

Krnjević, K., & Morris, M.E. (1974) Extracellular accumulation of K⁺ evoked by the activity of primary afferent fibres in the cuneate nucleus and dorsal horn of cats. Can. J. Physiol. Pharmacol. 52, 852–87l.

Krnjević, K., & Morris, M.E. (1975) Correlation between extracellular focal potentials and K⁺ potentials evoked by primary affrent activity. Can. J. Physiol. Pharmacol. 53, 912–922.

Krnjević, K., & Morris, M.E. (1975) Factors determining the decay of K⁺ potentials and focal potentials in the central nervous system. Can. J. Physiol. Pharmacol. 53, 923–934.

IN HIPPOCAMPUS

Krnjević, K., Morris, M.E., & Reiffenstein, R.J. (1980) Changes in extracellular Ca²⁺ and K⁺ activity accompanying hippocampal discharges. Can. J. Physiol. Pharmacol. 58, 579–583.

Morris, M.E., & Krnjević, K. (1981) Slow diffusion of Ca²⁺ ions in the rat’s hippocampus. Can. J. Physiol. Pharmacol. 59, 1022–1025.

Krnjević, K., Morris, M.E., & Reiffenstein, R.J. (1982) Stimulation-evoked changes in extracellular K⁺ and Ca²⁺ in pyramidal layers of the rat’s hippocampus. Can. J. Physiol. Pharmacol. 60, 1643–1657.

Krnjević, K., Morris, M.E., Reiffenstein, R.J., & Ropert, N. (1982) Depth distribution and mechanism of changes in extracellular K⁺ and Ca²⁺ concentrations in the hippocampus. Can J. Physiol. Pharmacol. 60, 1658–1671.

Morris, M.E., Krnjević, K., & MacDonald, J.F. (1985) Changes in intracellular free Ca ion concentration evoked by electrical activity in cat spinal neurons in situ. Neuroscience 14, 563–580.

Morris, M.E., Leblond, J., Agopyan, N., & Krnjević, K. (1991) Temperature dependence of extracellular ionic changes in hippocampal slices. J. Neurophysiol. 65, 157–167.

Electrical Interactions

MacVicar, B.A., Ropert, N., & Krnjević, K. (1982) Dye-coupling between pyramidal cells of rat hippocampus in vivo. Brain Res. 238, 239–244.

Taylor, C.P., Krnjević, K., & Ropert, N. (1984) Facilitation of hippocampal CA3 pyramidal cell firing by electrical fields generated antidromically. Neuroscience 11, 101–109.

Yim, C.Y., Krnjević, K., & Dalkara, T. (1986) Ephaptically generated potentials in CA1 neurons of rat’s hippocampus in situ J. Neurophysiol. 56, 99–122.

Dalkara, T., Krnjević, K., Ropert, N. & Yim, C. (1986) Chemical modulation of ephaptic activation of CA3 hippocampal pyramids. Neuroscience 17, 361–370.

Studies on Hippocampus In Vitro

EFFECTS OF HYPOXIA

Krnjević, K., & Leblond, J. (1987) Anoxia reversibly suppresses neuronal Ca-currents in rat hippocampal slices. Can. J. Physiol. Pharmacol. 65, 2157–2161.

Leblond, J., & Krnjević, K. (1989) Hypoxic changes in hippocampal neurons. J. Neurophysiol. 62, 1–14.

Krnjević, K. & Leblond, J. (1989) Changes in membrane currents of hippocampal neurons evoked by brief anoxia. J. Neurophysiol. 62, 15–30.

Cherubini, E., Ben-Ari, Y., & Krnjević, K. (1989) Anoxia produces smaller changes in synaptic transmission, membrane potential, and input resistance in immature rat hippocampus. J. Neurophysiol. 62, 882–895.

Krnjević, K., Cherubini, E., & Ben-Ari, Y. (1989) Anoxia on slow inward currents of immature hippocampal neurons. J. Neurophysiol. 62, 896–906.

Krnjević, K., & Xu, Y.Z. (1989) Dantrolene suppresses the hyperpolarization or outward current observed during anoxia in hippocampal neurons. Can. J. Physiol. Pharmacol. 67, 1602–1604.

Krnjević, K., & Walz, W. (1990) Acidosis and blockade of orthodromic responses caused by anoxia in rat hippocampal slices at different temperatures. J. Physiol. 422, 127–144.

Krnjević, K., & Xu, Y.Z. (1990) Mechanisms underlying anoxic hyperpolarization of hippocampal neurons. Can. J. Physiol. Pharmacol. 68, 1609–1613.

Krnjević, K. (1993) Membrane current activation and inactivation during hypoxia in hippocampal neurons. In Surviving Hypoxia: Mechanisms of Control and Adaptation. Eds. P.W. Hochachka, P.L. Lutz, T. Sick, M. Rosenthal, & G. van den Thillart. Boca Raton FL Florida: CRC Press, pp. 365–388.

Crépel, V., Krnjević, K., & Ben-Ari, Y. (1993) Sulphonylureas reduce the slowly inactivating D-type outward current in rat hippocampal neurones. J. Physiol. 466, 39–54.

Zhang, L., & Krnjević, K. (1993) Whole cell recording of anoxia effects on hippocampal neurons in slices. J. Neurophysiol. 69, 118–127.

Erdemli, G., & Krnjević, K. (1994) Tolbutamide suppresses slow and medium after hyperpolarization in hippocampal slices. NeuroReport 5, 2145–2148.

Belousov, A.B., Godfraind, J-M., & Krnjević, K. (1995) Internal Ca²⁺ stores involved in anoxic responses of rat hippocampal neurones. J. Physiol. 486, 547–556.

Erdemli, G., Xu, Y.Z., & Krnjević, K. (1998) Potassium conductance causing hyperpolarization of CA1 hippocampal neurons during hypoxia. J. Neurophysiol. 80, 2378–2390.

ADENOSINE AND HYPOXIA

Zhu, P.J., & Krnjević, K. (1993) Adenosine release is a major cause of failure of synaptic transmission during hypoglycaemia in rat hippocampal slices. Neurosci. Letts. 155, 128–131.

Zhu, P.J., & Krnjević, K., (1994) Anoxia selectively depresses excitatory synaptic transmission in hippocampal slices. Neurosci. Letts. 166, 27–30.

Zhu, P.J., & Krnjević, K. (1997) Adenosine release mediates cyanide-induced suppression of CA1 neuronal activity. J. Neurosci. 17, 2355–2364.

Zhu, P.J., & Krnjević, K. (1999) Persistent block of CA1 synaptic function by prolonged hypoxia. Neuroscience 90, 759–770.

Krnjević K. Electrophysiology of brain ischemia. (2008) Neuropharmacology 55, 319–333.

HYPOGLYCEMIA AND 2-DEOXYGLUCOSE

Crépel, V., Krnjević, K., & Ben-Ari, Y. (1992) Developmental and regional differences in the vulnerability of rat hippocampal slices to lack of glucose. Neuroscience 47, 579–587.

Tekkök, S., & Krnjević, K. (1995) Long-term potentiation in hippocampal slices induced by temporary suppression of glycolysis. J. Neurophysiol. 74, 2763–2766.

Tekkök, S., & Krnjević, K. (1996) Calcium dependence of LTP induced by 2-deoxyglucose in CA1 neurons. J. Neurophysiol. 76, 2343–2352.

Zhao, Y.T, Tekkök, S., & Krnjević, K. (1996) 2-Deoxy-D-glucose-induced changes in membrane potential, input resistance and EPSPs of CA1 hippocampal neurons. Can. J. Physiol. Pharmacol. 75, 368–374.

Tekkök, S., Medina, I., & Krnjević, K. (1999) Intraneuronal [Ca²⁺ ] changes induced by 2-deoxy-D-glucose in rat hippocampal slices. J. Neurophysiol. 81, 174–183.

Zhao, Y.T., & Krnjević, K. (2000) 2-Deoxy-D-glucose-induced long-term potentiation in CA1 is not prevented by intraneuronal chelator. J. Neurophysiol. 83, 177–180.

Krnjević, K., & Zhao, Y.T. (2000) 2-Deoxyglucose-induced long-term potentiation of monosynaptic IPSP’s in CA1 hippocampal neurons. J. Neurophysiol. 83, 879–887.

Xu, Y.Z., & Krnjević, K. (2001) Unlike 2-deoxy-D-glucose, 3-O-methyl-D-glucose does not induce long-term potentiation in hippocampal slices. Brain Res. 895, 250–252.

Tekkök, S.B., Godfraind J.M., & Krnjević, K. (2002) Moderate hypoglycemia aggravates effects of hypoxia in hippocampal slices from diabetic rats. Neuroscience 113, 11–21.

Post-retirement Research

ON DOPAMINERGIC CELLS IN MIDBRAIN

Ye, J.H., Ren, J., Tao, L., Krnjević, K., Liu, P.L., & McArdle, J.J. (2001) Ethanol potentiation of glycine-induced responses in dissociated neurons of rat ventral tegmental area J. Pharmacol. Exp. Therap. 296, 77–83.

Zhu, L., Krnjević, K., Jiang, Z., McArdle, J.J., & Ye, J.H. (2002) Ethanol suppresses fast potentiation of glycine currents by glutamate. J. Pharmacol. Exp. Ther. 302, 1193–1200.

Jiang, Z.L., Krnjević, K., Wang, F.S., & Ye, J.H. (2004) Taurine activates strychnine-sensitive glycine receptors in neurons freshly isolated from nucleus accumbens of young rats. J. Neurophysiol. 91, 248–257.

Ye, J.H., Wang, F., Krnjević, K., Wang, W., Xiong, Z., & Zhang, J.L. (2004) Presynaptic glycine receptors on GABAergic terminals facilitate discharge of dopaminergic neurons in ventral tegmental area. J. Neurosci. 24, 8961–8974.

Xiao, C., Zhang, J., Krnjević, K., & Ye, J.H. (2007) Effects of ethanol on midbrain neurons: role of opioid receptors. Alcoholism: Clin. Exper. Res. 31, 1–8.

Xiao, C., Shao, X.M., Olive, M.F., Griffin, W.C., Li, K.Y., Krnjević, K., Zhou, C., & Ye, J.H. (2009) Ethanol facilitates glutamatergic transmission to dopamine neurons in the ventral tegmental area. Neuropsychopharmacology 34, 307–318.

Some Others

Križ, J.M., Beaulieu, J.M., Julien, J.P., & Krnjević, K. (2005) Upregulation of peripherin is associated with alterations in synaptic plasticity in CA1 and CA3 regions of hippocampus. Neurobiol. Dis. 18, 409–420.

Costa-Mattioli, M., Gobert, D., Stern, E., Gamache, K., Colina, R., Cuello, C., Sossin, W., Kaufman, R., Pelletier, J., Rosenblum, K., Krnjević, K., Lacaille, J.C., Nader, K., & Sonenberg, N. (2007) eIF2α phosphorylation bidirectionally regulates the switch from short to long-term synaptic plasticity and memory. Cell 129, 195–206.

Zhu P.J., Huang W., Kalikulov D., Yoo J.W., Placzek A.N., Zhou H., Bell J.C., Krnjević K., Friedlander M.J., Noebels J.L. & Costa-Mattioli M. (2011) Suppression of the protein kinase PKR promotes network hypersynchrony and enhanced cognition by interferon-gamma-mediated disinhibition. (in revision).

*David Lowenthal, Cambridge University Press, 1985

Nicole M. Le Douarin

BORN:

Lorient, France

August 20, 1930

EDUCATION:

Université, La Sorbonne, Paris

Licence et agrégation de Sciences-Naturelles (1954)

Doctorat d’Etat es Sciences Naturelles, Paris (1964)

APPOINTMENTS:

Professeur agrégé de Sciences Naturelles (1954)

CNRS Researcher (1960)

Assistant Professor University of Clermont-Ferrand (1965) and Nantes (1971)

Director of the Institute of Cellular and Molecular Embryology of the CNRS and Collège de France (1975)

Professor at the Collège de France, Paris (1988)

Permanent Secretary of the Académie des Sciences, Paris (2001)

HONORS AND AWARDS (SELECTED):

Prix Cognac-Jay de l’Académie des Sciences (1965)

Prix Van Beneden de l’Académie Royale de Belgique (1973)

Member of the Académie des Sciences, Paris (1982)

Member of the Academy of Arts and Sciences (1984)

President of the International Society of Developmental Biologists (ISDB) (1985)

Kyoto Prize in Advanced Technology de la Fondation Inamori, Japon (1986)

Gold Medal of the CNRS (1986)

Foreign Associate of the National Academy of Sciences, USA (1989)

Foreign Fellow at the Royal Society of the United Kingdom (1989)

Award of the Fondation Louis Jeantet de Médecine, Genève (1990)

Louisa Gross Horwitz Prize, Columbia University (1993)

Ross Harrisson Prize of the International Society of Developmental Biology (1997)

Member of the Pontifical Academy of Sciences, le Vatican (1999)

Grand Officier dans l’ordre de la Légion d’Honneur (2002)

The Pearl Meister Greengard Prize, Rockfeller University (2004)

The Edwin Conklin Award of the American Society of Developmental Biology (2005)

Grand’ Croix dans l’ordre National du Mérite (2005)

Ralph W. Gerard Prize, Society for Neuroscience, USA (2007)

Prix d’Honneur de l’INSERM (2009)

Grand’ Croix dans l’ordre de la Légion d’honneur (2010)

Nicole M. Le Douarin began her research career while a high school teacher. Her Ph.D. work under the supervision of Etienne Wolff was on the development of the digestive tract and liver in the chick embryo. She later devised a cell-marking technique based on the construction of chimeras by combining cells of quail and chick embryos in ovo. Using this technique, she demonstrated that the neural crest is a major player in vertebrate embryogenesis, namely by its role in the development of the head and brain. She demonstrated with her colleagues the existence of a stem cell in the neural crest, the first example of a neural stem cell. She and her group applied the quail-chick chimera system to other problems such as hematopoiesis and demonstrated a novel mechanism of tolerance to self.

Nicole M. Le Douarin

Early Years

I was born in Brittany, a beautiful French province, in the city of Lorient. I spent my childhood in a small village, 30 km away from Lorient, where my mother was a teacher in the public school. My father was in business.

In France, child education was made both free and compulsory by Jules Ferry in the late 19th century. State schools were constructed even in small remote villages so that all children, whatever the financial means of their parents, could have a basic education up to the age of 15. Brittany was, at that time, under the powerful influence of the Catholic Church and, apart from the school provided by the state, there were also Catholic schools to which, especially in country places, the parents were strongly influenced to send their children. In fact, for many decades, a kind of “school war” (guerre scolaire) prevailed in several regions in our country and particularly in Brittany. As a result, the number of pupils in the public school was often small and, in small villages, like Locoal-Mendon where we were, there was a single teacher available in charge of pupils from the age of 6 to 15 (the so-called classe unique).

My mother allowed me to sit at the far end of the classroom from the age of 3 or 4, at least for part of day, provided that I behaved. As a result, I learned to read by myself without any effort at a very early age, just by listening and following the lessons meant for others. This was the way my primary school proceeded, smoothly and happily with not much difference between school and home.

At the age of 11 came the time for me to go to the secondary school called lycée (now designated as college for the first 4 years and lycée only for the next three). From the village where we lived, the closest city with a lycée was Lorient. But we were at war. The German troops occupied the country and Lorient had been chosen by them to establish a base for submarines, which was the target of frequent attacks by the Allied air force. The inhabitants of Lorient were evacuated and no lycée was available there anymore. I had to go to Nantes, 150 km away from home by train, which took 5 hours when everything went well. My father had a car, but during these difficult times, there was no gas except for people with a special permit, such as physicians who needed a car to visit their patients.

The separation from my family was extremely difficult for me and also, I think, for my parents, as I was their only and cherished child. We accepted this situation and my schooling went on smoothly, except that in 1944 Nantes was also the target of heavy bombing by the Royal Air Force. Fortunately the worst of it took place during the summer vacations. The consequence was that the lycée was closed and both teachers and pupils were invited to stay home. Thus, for one academic year we communicated by mail. At the “Libération” I was 15 years old. The country was free again. My mother got a teaching position in Lorient and the lycée opened again there. I left the Nantes boarding school and spent the 2 years that remained before the baccalauréat in the lycée in Lorient. The city had been totally destroyed; one house out of ten had been spared by the massive destruction inflicted to it because of its strategic position. My family had been given an “American house” provided by the Marshall Plan. We stayed there several years before the house, which my parents possessed in the city, was reconstructed. This period, when France revived from its long submission to an omnipresent enemy was a very exciting one. It was such a relief not to have the “occupation troops” around anymore and a joy to welcome the American troops, our liberators. These memories have remained vividly in my mind.

After obtaining my baccalauréat, the terminal high school examination, I wanted to go on studying and attend a University, a choice that my parents adhered to enthusiastically. The decision was that I should go to La Sorbonne in Paris, although, being in Brittany, the law (not too strict, fortunately) wanted me to register at the University of Rennes, the closest one to my residence. I succeeded in being accepted as a student in Paris.

My orientation in the secondary school was essentially about literature and humanities; I studied Greek, Latin, French literature, and philosophy. However, in the last year I had a very good teacher in biology and this probably explains my decision at the University, where after one year as a student in literature I resolutely turned my interests to natural sciences. My first project was to be a high school teacher. At the age of 24 I passed the competitive exam, called “agrégation de Sciences Naturelles,” which, if you succeed, provides you with a permanent position as a “Professeur de Lycée.”

At 23, I was already married and mother of my first daughter, Claire. I taught natural sciences (biology, physiology, zoology, botany, etc.) as well as earth science to high school children for 8 years, first in the city of Caen in Normandy and then in a special school where different teaching experimentations were conducted. This was in Montgeron, a city close to Paris, where the conditions were particularly nice: the lycée was in in the middle of a large park and the number of children by class was less than in a regular school. I was told that I was offered this position because I had been identified as someone who liked teaching. These 5 years in Montgeron left me with nice memories. However, I was not completely satisfied with my professional life. Although I liked to teach, I missed the University where one follows the science in progress. I felt that transmission of the knowledge to younger generations, although a very valuable task, was a bit frustrating.

Thus, I decided, at the age of 28 to go back to the University and to try and see whether I could find a means to do research.

I was the mother of two little daughters and had a full-time job at the lycée. I needed to go on with a job to survive since, although my husband was also a teacher, our two salaries were necessary. Therefore, satisfaction of this ambition was not a simple endeavor. My parents helped me very generously by paying a nanny who took care of our children. Moreover, my teaching duties left me some time every week so I could spare the equivalent of about 2 days to try and see whether research was something I could do and would like to do.

The next step was to find a laboratory in Paris that would accept me as a freelance researcher à l’essai, so to speak. This was a serious problem. Research was not very active after the war. Only a few laboratories were on the forefront of international research. Fortunately, the CNRS (Centre National de la Recherche Scientifique) had been created and efficiently contributed to the revival of French science. However, after some unsuccessful attempts to find a laboratory to work in, I realized that I did not have the right profile: I was too old (28 years old), and I had a family and a job. As I was told by someone: that was good enough and OK for me. Why should I want to do more or something else?

I was nearly completely discouraged when I had the chance to be introduced to Professor Etienne Wolff, who was running one of the most dynamic laboratories of experimental biology at the Collège de France in Paris. The Institut d’Embryologie et de Tératologie Expérimentales was located in a superb environment in Nogent-sur-Marne at the border of the Bois de Vincennes on the east side of Paris.

This laboratory has had a great importance in my professional life since it is where I was initiated to research in my young years and a place where I became Director later on for 25 years. For this reason I would like to tell some of its history.

The Institute of Embryology in Nogent-sur-Marne: Origin and Intellectual Heritage

Before being appointed to the Collège de France, Etienne Wolff held a professorship at the University of Strasbourg, where, back from a 5-year stay in a German prisoner camp, he had developed an already large laboratory supported by the CNRS.¹ The Nogent venture was part of a significant effort in the 1950s to re-create a national corpus of research, on the ruins left by the war.

The Nogent estate became a laboratory dedicated to the study of embryology in 1955 when Etienne Wolff was elected as a Professor at the Collège de France, where the chair of “Embryologie Expérimentale” was created for him. The estate had been donated to the Collège de France in the 1940s by the late Pr. d’Arsonval. This wealthy family house sat in a park planted with magnificent trees and ornamental bushes, bordering the residential suburban city of Nogent-sur-Marne in the “Bois de Vincennes.”

Given the choice between the CNRS campus in Gif-sur-Yvette and the Nogent site, Etienne Wolff chose Nogent and had it completely renovated, one floor becoming his own apartment, the rest being transformed into what was at that time a modern laboratory. A large part of the building had previously been the private laboratory of Pr. d’Arsonval.

Etienne Wolff was already famous for his finding that the recently discovered estrogens were able to influence the sexual development of the chicken embryo. He showed that these hormones transformed genetically male birds into intersexuals, which developed an ovarian cortex and retained Müllerian ducts. This first demonstration of a hormonal effect in the developing embryo opened a large research avenue brilliantly developed in France, apart from Etienne Wolff’s own laboratory, by Alfred Jost in mammals and Louis Gallien in amphibians. Wolff’s experiments were carried out just before the Second World War (Wolff, 1936a, 1936b) and were reported in his secondary thesis.² This piece of work was experimental rather than the typical analytical assay—an exceptional fact and a testimony to the intellectual dynamism and enthusiasm for biology displayed by this young man whose initial university education was in philosophy.

Etienne Wolff’s main thesis, published in 1936 in the Archives d’Anatomie, d’Histologie et d’Embryologie is a monumental study in the field of teratology. How do “monsters,” which appear from time to time in human or animal evolution, emerge? Some mechanism must go astray during development. The rational basis of this work was to try and reproduce the morphological abnormalities in the hope of finding cues as to how and why they appear, and, more interestingly, in the hope of acquiring information about normal embryological development. This was long before the time when any gene responsible for developmental malformations was identified. Wolff’s thesis, a masterpiece, still yields accurate information for avian embryologists.

In the laboratory that Etienne Wolff created in the College de France in the late 1950s, the number of investigators was already significant. Each was in charge of his own project, teamwork being rare at this time, so that the problems tackled were very diverse, ranging from regeneration in planarians and neural induction in amphibians to teratological effects of various drugs such as thalidomide.

Apart from the persistent interest of Etienne in the effects of ionizing radiations, the major trends concerned, first, sexual differentiation, which was directly related to Wolff’s previous findings (namely the effects of steroid hormones on the developing genital tract), and, secondly, tissue interactions occurring during organ development.

From the 1950s onward, one of the trends in physiology and developmental biology has been to dissect processes, previously described in the animal, in simplified systems, that is, in tissues isolated and grown in vitro in organotypic cultures. There, organ rudiments maintain their tridimensional structure in which the interacting tissue players can be separated by filters with adequate pores, allowing or not allowing cell traffic and passage of molecules of various sizes.

With one of his most skilful collaborators, Katy Haffen, Etienne Wolff developed a culture technique with which he himself and his coworkers (among whom were his spouse and colleague Emilienne Wolff) analyzed the responses to steroids of various organs rudiments. This culture technique was based on the incorporation of nutriments in a semisolid agarose gel, the tissues being placed at the interphase between air and medium. It was commonly used by researchers interested in tissue interactions during organogenesis.

My Early Research Experience

I came to Nogent in the late 1950s when the laboratory was at its peak. Broadly, my project concerned the digestive tract. Not much interest was directed to endoderm and its derivatives at that time and the message I received, along with some practical advice, was that I would find something worth investigating in this area.

In the first 2 years of my laboratory experience, I was far from being a full-time researcher. I remained a high school teacher and joined the Nogent-Institute only when my teaching duties gave me free time.

I rapidly realized that research would be my choice for life. Etienne Wolff was very encouraging and wise. He had created, in Nogent, a very well-organized laboratory with a pleasant atmosphere for work. At the end of these years during which I could test my motivation and he could evaluate my capacities for this activity, I was able to switch from teaching to research administration and from 1962 I was paid to do research and thus could devote myself full time to my project.

My first goal was to study the developmental events leading to the formation of the digestive tract and associated glands. As Etienne said, it was a neglected field. I learned from him how to handle early chick embryos, to make current type microsurgery such as grafting tissues into the coelomic cavity or on the chorio-allantoic membrane of host embryos. Organotypic cultures were among the techniques that Etienne Wolff had developed in the laboratory. Histology and histochemistry were the other methods regularly used by embryologists at that time.

In 1964, I defended my doctorate thesis entitled Etude expérimentale de l’organogenèse du tube digestif et du foie chez l’embryon de Poulet, which was published in the Bulletin Biologique de la France et de la Belgique (1964c). In this work, I first studied the morphogenetic movements of the endomesoderm, which lead to the ventral closure of the gut. I was fascinated by the spectacular transformations affecting the avian embryo during the first days of its development in the egg. How could a sheet of cells lying flat on the yolk become, within the next 2 to 3 days, a highly structured organism endowed with a head, a trunk, and a beating heart, surrounded by a frame of blood vessels? This appeared as a marvel and I thought that trying to decipher the cell behavior and the mechanistic forces underlying these processes would be an appealing (although very ambitious) challenge.

Arriving in Etienne Wolff’s laboratory, I naturally had the curiosity to read his thesis. Although dating from 22 years back (Wolff, 1936a), I found the opus inspiring. In this published memoire entitled Les bases de la tératogenèse expérimentale des Vertébrés Amniotes d’après les résultats de méthodes directes, he wanted to demonstrate that the abnormalities and monstrosities exhibited by some unfortunate children at birth were nothing mysterious (some people believed at that time that they were a manifestation of the ire of God) and could be scientifically explained. Developmental genetics had not yet been invented, and the best way to prove the validity of this view was to experimentally reproduce these naturally occurring abnormalities by interfering directly with the development of the embryo.

The availability of the avian embryo in the egg during the entire period of development was particularly suitable for this endeavor. Etienne Wolff was able to destroy selected embryonic areas in the early embryo by subjecting them to heavy and strictly targeted X-irradiation. The chick embryo as a whole was protected by a lead screen placed on top of it in ovo, except for the targeted area which was the only living tissue exposed to the X-rays. The cells of the irradiated zone died after a while and were progressively replaced by the adjacent living cells. Thus, the continuity of embryonic tissues was never interrupted. This allowed Etienne not only to produce some spectacular monsters such as Cyclops but also to discover the presumptive territories fated to yield various tissues and organs.

The precision of his experiments and the logic underlying both their planning and their interpretation were perfect. Coming back to my project, I thought that a prerequisite for the analysis of the development of endoderm-derived organs was to construct a fate map of the endomesoderm at the early embryonic stages and to try and discover its transformation into the digestive tract and its glandular appendages. In order to do so, I followed the path opened by Etienne many years before.

Two ways were available to reach this goal, either labeling the tissues and following de visu the movements of the labeled cells, or destroying definite territories by X-rays and looking at what was missing afterward. I was conscious, however, that the X-ray technique was not fully reliable since the neighboring embryonic cells might partly replace those that had been killed. The “regulation capacity” through which an embryo tends to produce a normal individual after being subjected to various kinds of injuries is actually very efficient at these early stages of vertebrate development.

In the late 1950s, one of the best ways to label embryonic territories was to apply carbon particles to them which, although they adhere to the cell membrane, are not harmful. The relative displacements of the labeled cells can, by this means, be roughly (if not very precisely) visualized and recorded. The use of these methods, namely X-ray destruction and carbon labeling of embryonic areas, led to the construction of embryonic fate maps at different developmental stages. The results showed that the construction of the digestive tract involved major and complex morphogenetic movements that I strived to describe.

My second objective was to determine when the commitment of the endodermal cells at the origin of the glands associated with the digestive tract takes place early in development. I found that endodermal cells fated to differentiate into hepatocytes, pancreas, thyroid, and parathyroid are present in the anterior intestinal portal (AIP) at the 15 to 25 somite stages (15–25 ss). It is only later, when ventral closure of the foregut has occurred, that these cells start to form the corresponding glandular structures. This, however, cannot happen without the cooperation of the splanchnopleural mesenchyme.

I studied the relationships that take place between endoderm and mesoderm during the development of the liver. I showed that the few endodermal cells in the AIP committed to become hepatocytes originated from the coalescence of paired endodermal areas (the prehepatic endoderm) lying on each side of the primitive streak and head process at the presomitic stages. These prehepatic areas of endoderm were juxtaposed to the future cardiac mesoderm.

Two successive steps of induction of the prehepatic endoderm are required for the differentiation of hepatocytes to occur. The first one takes place early (before 5 ss) and arises from the precardiac mesoderm. It turned out to be required for the efficacy of the second interaction, which occurs between the specified hepatic endoderm and the mesenchymal component of the liver. These two steps lead to the growth of the endodermal cells and their differentiation into hepatocytes (Le Douarin, 1963a, 1963b; Le Douarin, 1964a–1964c; Croisille et Le Douarin, 1964; Le Douarin, 1965).

In the early 1960s, the molecular tools required to identify the signaling molecules involved in these processes were not available. Since then, several groups have pursued investigations on the tissue interactions responsible for the development of glandular tissues of endodermal origin. The two-step induction of the prehepatic endoderm was found to occur also in mouse development. Fgf1 and Fgf2 were shown to trigger the specification effect of the cardiac mesoderm on the prehepatic endoderm. Fgf8 seemed to be responsible for the second induction, which leads to growth and differentiation of the hepatocytes (Jung et al., 1999).

In the chick, I investigated the nature and origin of the mesenchymal component of the liver. It turned out that the liver mesenchyme develops at the same time as it is invaded by cords of epithelial cells from which the hepatocytes differentiate. This is why it had never been described or isolated. I designed a microsurgical technique, through which the mesenchymal component of the liver developed in the absence of its endodermal component, which was prevented from invading it. In such a situation, the liver mesenchyme developed as bilateral empty bags connected with the septum transversum. It turned out that, in the embryo, the liver mesenchyme was entirely composed of cells belonging to the vascular endothelial lineage.

The technique I devised to isolate the mesenchymal network into which the epithelial cords of endodermal origin progress consisted in interposing an obstacle (a fragment of the shell membrane of the egg) in the somatopleura within the presumptive territory fated to yield the liver mesenchymal component. The areas located posteriorly to the barrier gave rise to the mesenchyme that could be cultured in vitro. The liver mesenchyme was then placed in organotypic cultures, with the aim of exploring more precisely its role in the differentiation of the hepatic-endoderm (Le Douarin, 1964b, 1964c).

The endoderm of the AIP of the chick embryo of 2 to 3 days of embryonic age (E2–3) could easily be isolated by using trypsin or pancreatin. This avoided contamination by mesenchymal cells. If cultured alone as an explant at the interface air/medium, it survived for about 24 hours, but its component cells did not proliferate. The contrast was striking when this small piece of endoderm was placed in contact with the liver mesenchyme taken from an E5–6 embryo, which I operated so that this mesenchyme developed void of hepatocytes. In such an association, the endodermal cells divided actively, colonized the mesenchyme, and acquired evident hepatocytic features: glycogen storage and enlargement of the nucleolus were the most conspicuous. None of the other endodermal anlagen in the E2–3 embryo, with the exception of the epithelium of the AIP, taken from the donor and subjected to the influence of the hepatic mesenchyme, underwent any of these changes. This was indicative of the commitment of the AIP endoderm to hepatic differentiation.

I found that the effect of hepatic mesenchyme was mediated by a diffusible substance since it could take place when a filter preventing cell-to-cell contacts was interposed between the two reactive tissues. The substance(s) probably belongs to the Fgfs family, as is the case in the mouse.

From Liver Studies to the Quail/Chick Marker System

Being “Docteur ès sciences” in 1964, the “normal” course of my career should have been to continue as a CNRS researcher. The other possibility was to apply for a position of “Assistant Professor” in a University. This, however, did not seem realistic to me since, at that time, these positions were essentially reserved for men. The position of University Professor was much more prestigious in the early 1960s than that of CNRS researcher.

Etienne Wolff, however, encouraged me to apply for a position at the University of Clermont-Ferrand , where I stayed for 1 year before going to Nantes. Two positions became available there in 1966, which my husband and I occupied. We therefore moved the family to this town, where I had spent my high school years in the Lycée Gabriel Guist’hau and where I established my first independent research group.

The respective status of University Professor and CNRS researcher has radically changed since this time. In the 1950s and early 1960s, the laboratory directors were all professors while the CNRS employees, at least in biology, worked under their authority. Moreover, in contrast to the “Education Nationale,” the CNRS did not appoint their researchers and technicians to permanent jobs. It was only after 1981, when the left wing won the elections and François Mitterrand became President, that the CNRS researchers acquired the status of civil servants with the same salaries as the University personnel.

With the after-war baby boom, a rush of students submerged the universities. The teaching load of the assistants and professors increased considerably. Moreover, the social changes that followed the 1968 movement, which minimized the prestige of the University Chairman, contributed to switching the research funding provided by the Ministry of Education and Research from the universities to CNRS and INSERM (Institut National de la Santé et de la Recherche Médicale) laboratories. A more accurate way of evaluating the scientific achievements of the laboratories prevailed and, beginning in the 1970s, research subsidies were preferentially distributed to laboratories in which CNRS researchers, free from teaching duties, could devote all their time to their research projects. As a consequence, research and universities tended to be separated with, at term, negative consequences for both. Fortunately, a certain number of productive university laboratories became associated with the CNRS and INSERM so that research activity remained, at least in these, closely associated with teaching and students.

In 1965, I was thus appointed as a Maître de Conférences (now designated as second-class Professor) in Clermont-Ferrand in the Department of Developmental Biology whose chairman was Hubert Lutz. Hubert Lutz had been Etienne’s first student when he started his career at the University of Strasbourg. I was provided with a substantial amount of teaching, which extended over the whole academic year. I was in charge of teaching Biology for the first and second-year students and also in charge of a course in Developmental Biology, two others in General Physiology, and one in Agricultural Zoology! My family was still staying in Paris and I had to travel to Clermont-Ferrand every week by train. In addition to teaching, Hubert Lutz gave me the responsibility of supervising two young students who prepared a master research project. It was when I was working with them that I had, for the first time, the opportunity to use quail eggs for my experiments.

Several laboratories working with avian embryos in France were provided with eggs of quail (Coturnix coturnix japonica) by a geneticist working in the CNRS campus of Gif-sur-Yvette in close vicinity of Paris. Dr. Ernst Bösiger was doing experiments on this species to document the concept of “hybrid vigor,” developed after the Second World War, with a view of demonstrating that establishing “pure races” by means of inbreeding was not particularly favorable to the species, in contrast to the selective advantages provided by hybridization.

Each sexually mature female quail lays one egg per day, meaning that the large colony that he needed for his investigations produced far more eggs than he could use. He had the generous idea of giving these fresh quail eggs to labs which could use them for their research. In Etienne Wolff’s Institute in Nogent, as well as in Clermont-Ferrand, some researchers started to do some experiments with quail instead of chick embryos. This is what I did with my two first students. We published a paper in 1966 (Le Douarin and Chaumont, 1966) in which we described that the mesenchyme of the liver is not unique in being able to promote the growth and differentiation of hepatocytes from the AIP endoderm. The entire splanchnopleural mesoderm can play the same role. If the endoderm of the AIP is grafted into the splanchnopleura of an E3 embryo, a liver lobe develops either in the ventral body wall or in the intestinal mesenchyme. Interestingly, other glandular structures, parathyroid and thymus, are also present at the graft site, meaning that the splanchnopleura is permissive for the expression of all the potentialities contained in the AIP endoderm. The signaling pathways responsible for this effect are still not known. Another result of these experiments was that the dorsal mesenchyme (somitic and unsegmented paraxial mesoderm) associated with the AIP endoderm inhibited its growth and differentiation, while allowing the survival of only a selected set of the grafted cells. Most of these experiments were carried out on quail embryos. I noticed, after a simple hematoxylin-eosin staining, that quail nuclei had a large, densely stained nucleolus, but this did not particularly capture my attention at this time.

The following year I was appointed at the University of Nantes, where I was to stay for 8 years. There I established my first independent research group. I was in charge of most of the Developmental Biology course and part of the Physiology one, the latter mainly under the responsibility of my husband, Georges le Douarin. These courses attracted several young students and some, interested in studying development, asked me to be their thesis supervisor. Christiane Le Lièvre, Marie-Aimée Teillet, and Josiane Fontaine, who were among them, have been working with me from the beginning, when I decided to apply the quail-chick marker system to the ontogeny of the neural crest and its derivatives, and for many years onward.

Devising a Cell-Marking Technique in the Avian Embryo In Ovo

Serendipity allied to curiosity sometimes results in a story with a happy ending. Before telling this story I will describe the framework of the institution in which I established my first independent research.

Nantes had possessed a University in historical times. Such an institution was created by a papal bull in 1490 but was abolished by the French revolution. The new University dated from the early 1960s. When we arrived, no active research laboratory had been established yet in the Life Sciences. Both teaching and research had to be created there by the newly arriving professors.

Georges Le Douarin was also a former disciple of Etienne Wolff and was interested in the development of the heart. During his postdoctoral stay with the well-known physiologist Edouard Coraboeuf, he became interested in the physiological aspects of cardiomyocytes differentiation. We joined our efforts to create a laboratory in which the two groups, his and mine, worked side by side on different subjects. I developed an embryology project which was the continuation of my thesis work on liver development. I was intrigued by the strong effect of the hepatic mesenchyme on the differentiation and growth of the AIP endoderm, and I decided to concentrate on the mechanisms underlying these tissue interactions. As a side project and since quail eggs were available, I decided to see whether the induction of growth and differentiation of the hepatic endoderm by the homologous mesenchyme could take place if these tissues belonged to two different species. This seems evident today since we know now that the molecular pathways involved in developmental processes have been remarkably conserved throughout evolution, but it was not so sure at that time. I then associated in organotypic culture the hepatic mesenchyme of a quail embryo with the AIP endoderm of a chick (and vice versa) in the same way I previously did with the two components belonging to the chick. I saw similarly that a lobe of hepatic tissue, in which mesenchymal cells and hepatocytes were closely associated, developed in the culture dish.

A “detail” struck my eyes, however, when I observed the microscopic sections of these chimeric liver lobules resulting from the association of chick AIP endoderm with quail liver mesenchyme. One of the conspicuous changes taking place in the endodermal cells when they become hepatocytes was the enlargement of their nucleolus. This is related to the increase in protein synthesis, a characteristic of hepatocytes. In the chimeric liver resulting from the association of quail mesenchyme with chick endoderm, the chick hepatocytes looked the same as in normal chick liver, but the mesenchymal cells also exhibited a large nucleolus, a character not expected in this cell type.

This probably reminded me of the observation that I made in Clermont-Ferrand of the large size of this organelle in quail cells. At that time, it remained in my mind in a subliminal state, but in the context of the hepatic tissue it occurred to me that it was something strange since no particular quantitative increase in protein synthesis was known to justify it in hepatic mesenchymal cells.

I decided to make some enquiry on this observation, just to satisfy my curiosity. First, I had a look again at diverse quail tissues, and I noticed that the large nucleolus of the hepatic mesenchymal cells was, in fact, a general feature of all quail cells. I applied Feulgen-Rossenbeck’s staining procedure for DNA to various cell types, including the chimeric liver lobes that had developed in culture. I also tested the RNA component of the nucleoli through the Unna-Pappenheim staining method. To my surprise, I saw that the quail nucleolus was mostly composed, not of RNA as is classically the case, but of DNA (Le Douarin, 1969, 1973a, 1973b).

Notably, in the mesenchymal cells of the liver lobes, the amount of RNA of the nucleolus was as small as in the same cells of the chick. The enlargement of this organelle was due to the presence of heterochromatin, a feature common to all quail cell types in embryos and adults as well. Some variations in the quantitative and spatial relationships of DNA and RNA in the nucleolus existed, however, in the different cell types as reported in an article I published in 1973 (Le Douarin, 1973b).

In the late 1960s, an in-depth structural and dynamic study of the nucleolus was being performed in the laboratory of Wilhelm Bernhard in a CNRS laboratory at Villejuif, a Paris suburb. I decided to visit Dr. Bernhard and to show him the unusual nucleoli of quail cells. He was interested and invited me to report this observation at a meeting that he was organizing and which was going to take place a month later in Hungary, close to Lake Balaton. He found 15 minutes for me in the already finalized program.

This introduced me into the biology of this important cellular organelle whose role in the molecular biology of protein synthesis was being actively studied at that time. I was very interested and thought for a while to embark into this field with the aim of finding why the nucleoli of quail cells accumulated so much heterochromatin while in the chick, mouse, and humans, for example, heterochromatin was more or less evenly dispersed in the nucleoplasm with merely some aggregates called chromocenters always distinct from the nucleolus. Having been interested in zoology and biodiversity during my training years at the University, I wondered whether this particularity of the quail was a rare occurrence or if it was common in the avian world.

I bought as many birds as available in specialized shops and decided to look at the distribution of their DNA in the nucleus. The problem was that I had to kill these beautiful little birds and found myself unable to do it. A colleague in the lab graciously replaced me in this nasty work.

I found that domestic birds had the same type of nucleolus as the chicken (with a very restricted amount of DNA component). Among wild birds, many had quail-like nucleoli. This particularity turned out to be a generic character. Within a given genus, like Sturnus for example, all the species I could look at had the same DNA-rich nucleolus (Le Douarin, 1971). These zoological investigations were only a short parenthesis. I rapidly resumed my research on the mechanisms of development and fully devoted my interests to this fascinating field.

I was still working on the cell-to-cell interactions that lead endodermal cells to differentiate into hepatocytes. At that time nothing was known about the signaling molecules (like the Bmps, Wnts, Fgfs, noggin, chrodin, etc.), which are responsible for determining dorsoventral polarity in the vertebrate embryo. What was suspected, however, was that this polarity corresponded to inverse gradients of still hypothetical dorsalizing and ventralizing substances along the dorsoventral axis of the embryo (see, for example, Toivonen and Saxen, 1955).

I had observed that any ventral type of mesenchyme (belonging to the lateral plate, either somatopleural or splanchnopleural) in the 2- to 4-day- old embryo (E2–4) was permissive for the development of the endodermal glandular tissues. In contrast, the paraxial, dorsal mesoderm was clearly inhibitory. I was thus curious to see what would be the effect of the still undifferentiated intermediate mesoderm in similar circumstances. At that time, several laboratories were investigating the development of the metanephros in the mouse and in the chick. I therefore knew how to isolate the chick metanephric mesenchyme before it had been induced by the ureteric rudiment to differentiate into kidney tubules. I therefore cultured this mesenchyme organotypically in association with the AIP endoderm in the same way I had done before with the liver mesenchyme.

The result was striking. The metanephric mesenchyme promoted the growth of the endodermal epithelium, which produced epithelial cords of hepatocyte-like cells but with a surprising characteristic: they were totally devoid of glycogen (Le Douarin and Houssaint, 1968; Le Douarin, 1968).

The capacity of these cells to produce glycogen, however, was not definitively lost. The lobe of pseudo-liver (made up of kidney mesenchyme associated with the AIP endodermal cords of cells) was co-cultured with pure liver mesenchyme. Hepatocytes arising from the proliferation of the endodermal cells present in the metanephric environment invaded rapidly the hepatic mesenchyme. In this context these liver cells accumulated glycogen, although they were derived from the endodermal cells which had first developed in the metanephric mesenchyme.

The question was then the following: why was the glycogen absent in the hepatocytes that colonized the metanephros? I finally could prove that, in the chick, catecholamine (CA)-producing cells were present in the metanephric rudiment at the time I was removing it from the embryo (E4–5) (Houssaint and Le Douarin, 1968; Le Douarin, 1968). Epinephrine and norepinephrine are hyperglycaemic hormones. I thus inferred that they were depleting the glycogen from the hepatocytes present in the explant. I wanted next to prove that these CA-producing cells revealed by a simple histochemical technique were bona fide adenomedullary-like cells, hence derived from the neural crest.

After reading the available literature on the neural crest, I realized that I had at hand a way to see whether the cells that I suspected were producing adrenaline had a neural crest origin, as they should if my hypothesis was correct. The tool I had in hand for approaching this problem was the capacity to trace embryonic cells by constructing quail-chick chimeras. I then started to construct such chimeras by replacing the neural tube of the chick by that of a stage-matched quail at the level from which I supposed the medullary cells of the suprarenal glands originate.³ I extended these grafts caudally since it had been reported in the literature that some “extra suprarenal glands” represented by adrenergic cell aggregates existed along the dorsal aorta in birds. In mammals such accessory adrenergic tissues are also present and even form islets of adrenergic cells on the surface of the urinary bladder.

These experiments were lateral to the main stream of the research going on in the lab, and I did them on my own just for fun. When I first saw a chimeric embryo whose sections had been treated with the Feulgen-Rossenbeck’s staining procedure (allowing distinction between quail and chick cells by their nucleolus), the result was striking. Quail cells were present not only in the grafted spinal cord but also were dispersed in many other places of the embryo (at E5–6): along the nerves, as Schwann cells, in the peripheral ganglia, in the suprarenal gland and within the metanephritic mesenchyme. It was a shock, a real joy which has no equivalent, which I wanted to share immediately with the other members of the lab. They were invited to watch by themselves, at the microscope, what could be considered as the visualization of the migration of cells within the embryonic body, a phenomenon that had so far merely been inferred from fragmentary experimental proofs. It was clear that this technique, compared to the previous ones used to label the cells and follow their fate (either H3-TdR, vital stains, or carbon particles), was superior due to its being stable and unalterable and also not transmissible to neighboring cells. Its degree of precision thus depended upon the skill of the microsurgeon who was substituting the quail (or chick) tissue to that removed in the host of the other species. The potential use of this cell-marking technique for solving a number of problems in embryology immediately appeared to be considerable.

During my Ph.D. work, I had been working abundantly on the embryo in vivo, and I was well trained for doing microsurgery on many systems. Along the rest of my career in research I taught this technique, with many variants, to a number of younger research students and also to colleagues who came to Nogent for a sabbatical stay with us. Among many others, Marie-Aimée Teillet acquired remarkable skills in in vivo manipulations. We have worked together on a number of developing systems during 30 years. Christiane Le Lièvre was one of my first students in Nantes. For her thesis work, she completely revisited the role of the neural crest in vertebrate head development (Le Lièvre, 1978). This subject was later on pursued by Gérard Couly and myself with more refined methods and is presently taken over by Sophie Creuzet.

Others, such as Josiane Fontaine-Pérus, who developed her own lab at the University of Nantes, derived from the original quail-chick chimeras a new technique in which she constructed mouse-into-chick chimeric embryos and was thus able to study certain developmental problems in an original way. For her thesis work, Christiane Le Lièvre explored the fate of the cephalic neural crest and was the first to demonstrate that the facial skeleton is entirely derived from the neural crest. This was made possible because she performed large grafts of segments of the quail encephalic vesicles into chick embryos leading to cartilages and bones entirely made up of quail cells.

My long-term association with Gérard Couly deserves to be mentioned. When he came to the lab to undertake experimental work on the embryology of the face, he was a young surgeon at the Hospital Necker-Enfants-Malades in Paris. He was trained in odontofacial surgery and was essentially using his skills to repair congenital or traumatic malformations or damage in the faces of babies and children. He was intrigued by the origin of the distortions from normal morphogenesis that he had to deal with in the unfortunate children born with facial defects, a situation which occurs with a rather high frequency. He had heavy duties at the hospital and, although I fully acknowledged his curiosity and ambition to undertake experimental work on avian embryos, I was not so confident that he would be in a situation to meet the constraints involved in such an endeavor.

The reason he happened to know about my work is because I was asked to give a series of lectures on the neural crest to medical students. Although not a student anymore, he attended these lectures and developed a desire to be part of this venture.

Christiane Le Lièvre was in charge of teaching him how to handle the avian embryos. He thus started to switch from surgery on babies to microsurgery on small chick and quail embryos whose size at the stages he was concerned with was much smaller. He impressed us by the regularity with which he attended his microsurgery sessions in the lab. He regularly came one full day per week during which he was stuck to the dissecting microscope. When we were convinced that he was really taking it seriously, I managed to have him assisted by a technician to collect the embryos and perform histology on them when he was back at the hospital.

He became passionate for this work, and we engaged in a close collaboration that led to his becoming an embryologist particularly gifted in microsurgery while still being a doctor and eventually a Professor of Medicine at the University of Paris V in the Necker-Enfants-Malades hospital. Gérard Couly’s grafting procedures were very refined. They concerned very small fragments of the anterior neural primordium and even of its lateral border, the neural fold at the head level, which were exchanged between quail and chick embryos, with the objective of discovering their actual fate during embryogenesis and their contribution to the adult brain and head.

Anne Grapin, now in EPFL (Ecole Polytechnique Fédérale de Lausanne), followed him in this venture for her thesis work. This approach gave rise to several articles in which many basic features of vertebrate head development were established (Couly and Le Douarin, 1985, 1987, 1988, 1990a, 1990b; Couly et al., 1992, 1993, 1994, 1995, 1996, 1998, 2002; Etchevers et al., 2002; Creuzet et al., 2005). This work is now pursued by Sophie Creuzet and myself with a new goal: discovering the molecular control of facial and brain development (see below) (Creuzet et al., 2006; Creuzet, 2009).

The Neural Crest and Its Derivatives in Higher Vertebrates

As related before, my first work on the neural crest was to seek an explanation for an intriguing observation concerning liver development. This first experimental acquaintance with the nervous system seemed to me very attractive, since I realized that I could achieve something worthwhile by using the quail-chick marker system to document the role of the neural crest in vertebrate development.

This transitory structure had been discovered by the German histologist, Wilhelm His, in 1868, and had been mostly studied in lower forms of vertebrates during the first half of the 20th century. This early work had been summarized in 1950 in a well-acknowledged monograph by Sven Hörstadius entitled The Neural Crest (Hörstadius, 1950).

When I became interested in this structure, in 1968, only a little information was available about the contribution of the neural crest to embryogenesis in higher vertebrates (birds and mammals). Moreover, knowledge about the neural crest in lower vertebrates was only partial. It seemed therefore that the identification of the derivatives of the neural crest in amniotes was a chapter of embryology that had to be further documented and the quail-chick marker system was perfectly suited to do so.

By constructing quail-chick chimeras, in which part of the neural primordium of the host embryo was substituted by its counterpart taken from a stage-matched donor of the other species, the migration and fate of the neural crest cells was followed during the entire embryonic life and could even be pursued after birth thanks to the stability provided by this cell labeling technique. Such chimeras were able to hatch and displayed normal growth and behavior before being subjected to graft rejection (see later discussion).

The experiments that I performed with young doctoral students, Marie-Aimée Teillet, Christiane Le Lièvre, and Josiane Fontaine, were aimed at exploring systematically the fate of the neural crest cells exiting from the various transverse levels of the neural axis. We could thus establish the following: (1) the cell types arising from the neural crest, (2) their level of origin, and (3) the pathways they followed to reach their destinations. This allowed a fate map of the neural crest to be constructed.

The derivation of the peripheral nervous system (PNS) from the neural crest was already known. However, it was striking to see that regions of the spinal cord and medulla oblongata were particularly devoted to yield the sympathetic, parasympathetic, or enteric ganglia. Certain areas of the neural crest were particularly interesting to me in this respect. One of them was the so-called vagal level of the neural crest (extending over somites 1 to 7 and corresponding roughly to the level of emergence of the vagus nerve, which innervates the gut), from which the neural crest cells migrated to the gut and invaded it down to the cloaca. This showed that the pre- and postganglionic parasympathic neurons of the enteric nervous system (ENS) have the same level of origin along the neural axis. We found an additional contribution to the ENS from the lumbosacral neural crest located posteriorly to somite 28. These two levels of the central nervous system (CNS) thus contain the preganglionic neurons innervating the enteric ganglia, which are derived from the neural crest and which, in the gut environment, differentiate into cholinergic and peptidergic neurons, catecholamine (CA)-producing cells being excluded in the ENS.⁴

A third region of interest is located in the spinal cord between somite 18 to 24. It provides the suprarenal gland with adrenal cells and yields the adrenergic neurons of the sympathetic ganglia corresponding to this axial level (but does not contribute to the ENS). It was for this reason designated as the “adrenomedullary” level of the neural crest. As mentioned earlier, accessory aggregates of catecholaminergic glandular cells located along the dorsal aorta are also produced by the neural crest of the more caudal levels.

These results were published in the Journal of Embryology and Experimental Morphology in 1973 (Le Douarin and Teillet, 1973). I happened to know the referee of this paper, since I met him in Woods Hole where I was invited during the summer as a Lillie Fellow. Pr. Yntema, who had worked on the origin of the gut innervation in the chick several years before (Yntema and Hammond, 1954, 1955), engaged in a discussion with me on the subject and said that he enjoyed reading the article when he was invited to act as a referee for the JEEM. The method he had used several years before to investigate how the ENS developed consisted of removing sections of the neural crest in the chick embryo. The results he obtained pointed to an origin of most of the neurons at the vagal level of the neural axis, but they were not as precise and clear-cut as those that were produced from the use of a cell marker. At that time (before Internet) Eugene Garfield, the founder in Philadelphia of the “Institute of Scientific Information,” published every week Current Contents, where the table of the contents of all the scientific journals were recorded on a weekly basis. Every issue presented and commented on one or two articles that had a special interest and that were recorded as “Citation Classics.” To our great satisfaction, our paper was one of those.

Developmental Plasticity of PNS Neural Precursors

The fate map of the neural crest clearly showed that the neural crest cells exiting from the neural tubte between the vagal and the lumbosacral levels did not contribute to gut innervation. This striking difference in neural crest cells fate between the “vagal-lumbosacral” or “enteric” on the one hand and the “adrenomedullary” levels, on the other hand, raised the question as to whether the neuronal precursors fated to differentiate into adrenergic or cholinergic neurons were precommitted prior to their migration. In such a case, this prespecification would be responsible for their migratory behavior. The alternative was that, according to the level of the neural tube from which they emerge, they could be led through defined migration pathways to a particular destination. Their differentiation into one or the other neuronal types would in this case depend upon signals that they would receive either during their migration or later at their site of arrest or both.

Experiments carried out to test these alternatives demonstrated the initial pluripotency of the autonomic neuroblasts. Thus, transplantation from quail to chick (or vice versa) of the fragment of the neural tube located at the level of somites 18–24 (adrenomedullary level of the neural crest) up to the 1–7 level (enteric level of the neural crest), showed the capacity of the neural crest cells of this truncal level to colonize the gut and to differentiate into cholinergic (and not to adrenergic) neurons. In the same way, transplantation of the neural tube from the “enteric” or “vagal” level (somite 1 to 7) to the “adrenomedullary” level of the neural axis contributed adrenergic neurons and adrenomedullary cells (of vagal origin) to the para-aortic plexus and to the suprarenal gland, respectively (Le Douarin et Teillet, 1974; Le Douarin et al., 1975).

In the early 1970s, I was invited to lecture in several Canadian universities, and I related these observations before they were published. When I was visiting Pr. Jack Diamond, at McMaster University, Pr. Edwin Furshpan from Harvard was in the audience and saw, in my results, a support for experiments going on at that time at Harvard Medical School in the famous neuroscience laboratory where Edwin Furshpan, David Potter, and Paul Patterson were showing in isolated newborn rat sympathetic neurons that their adrenergic phenotype could be switched to cholinergic through coculture with glial cells. The plasticity of the neuronal progenitors that we demonstrated in vivo reinforced their conviction that the phenomenon they were seeing was not an in vitro artifact but resulted from a real influence of the environment on the terminal neuronal differentiation concerning the neurotransmitter choice (Patterson and Chun, 1977; Patterson et al., 1975; Furshpan et al., 1976; Rao and Landis, 1990). This series of work was the first demonstration of the developmental plasticity of neuronal progenitors. It was at the origin of a number of projects in various laboratories. Such a plasticity was found in other neuronal systems, including the CNS.

Paul Patterson continued to work on this capacity of sympathetic neuroblasts to switch their phenotype from adrenergic to cholinergic and identified a substance able to mediate this effect (Yamamori et al., 1989) that was already known for its action on hematopoietic cells, LIF (for leukemia inhibitory factor).

The Problem of the Origin of the Endocrine Cells Associated with the Digestive Tract: The APUD Cells

In the 1970s a great deal of attention was devoted to aminergic and peptidergicsecreting cells that turned out to be common in the nervous system as well as in the gut epithelium and its derivatives. One way to demonstrate such cells was to show that they were able to take up various precursors of monoamines and to decarboxylate them. Hence, this rather heterogeneous group of cells is designated by the acronym APUD (for amine precursor uptake and decarboxylation), the name given to them by a British histochemist, Anthony Pearse (1969). Being decarboxylated, these amines were fluorescent if subjected to the appropriate wavelength of ultraviolet light. Pearse put forward the hypothesis that all the endocrine cells of that type (including the adenomedullary catecholaminergic cells [AM cells], the dopaminergic cells of the carotid body, several cells of the intestinal epithelium [e.g., the enterochromaffin cells], the pancreatic islet cells, the calcitonin-producing cells of the ultimobranchial body) were all neural crest derivatives. This was established for the AM cells, but the fact that all these cells had some histochemical common characters could not be considered as a proof of their common origin. With Josiane Fontaine and Christiane Le Lièvre, we traced the origin of the cells of the carotid body and of the calcitonin-producing cells of the ultimobranchial body back to the rhombencephalic neural crest (Le Douarin and Le Lièvre, 1970, 1971; Le Douarin et al., 1972, 1974, 1978; Pearse et al., 1973; Polak et al., 1974; Fontaine and Le Douarin, 1975). In contrast, the endocrine cells of the pancreas and of the gut epithelium were found to be endodermal in origin (Le Douarin, 1988; see also Le Douarin, 1982).

The Neural Crest and the Vertebrate Head

One of the striking features of the neural crest is that it is truly pluripotent and yields not only neural cell types, melanocytes, and endocrine cells but also mesenchymal cells that are highly represented in the vertebrate head. The first demonstration of the contribution of the crest to the mesenchyme goes back to the 19th century when Kastchenko (1888) and Goronowitsch (1892, 1893) observed cells of mesenchymal types arising from the neural crest in Selacians and Teleosts. At the same time, Julia Platt, watching the development of Necturus under the microscope, noticed that cells originating from the dorsal midline of the neural anlage travelled ventrally to participate in the formation of the lower jaw (Platt, 1893). This assumption of a possible ectodermal origin of mesenchymal cells giving rise to bones contested the generally recognized validity of von Baer’s germ layer theory, according to which each of the three germ layers was devoted to yielding definite types of derivatives. In this context, the skeleton was considered to be exclusively of mesodermal origin. It thus appeared (at that time) “impossible” that the jaw could have an ectodermal origin via the neural crest. Following this observation, numerous investigations were carried out during the first half of the 20th century, essentially on lower vertebrates, which confirmed and completed Julia Platt’s results (for reviews, see Hörstadius, 1950; Le Douarin, 1982; Hall, 1999).

Very little work had been devoted to the neural crest in the higher forms of vertebrates when I started to be interested in this structure. This is related to the fact that in amniotes the number of embryonic cells becomes rapidly very high and the migrating cells thus become undistinguishable from those of the tissues through which they move. A way to label them in a reliable and stable manner was actually required for this purpose.

Until such a method became available, researchers performed ablation experiments in which excision of fragments of the neural primordium in chick embryos were followed by the absence of certain structures (Hammond and Yntema, 1953; see Le Douarin, 1982, for a review). However, this technique is not totally reliable, since at the stage of development elected for these experiments, the capacity of the embryo to regulate the deficiencies due to the ablations is high.

In 1966, Malcolm Johnston undertook a series of investigations on craniofacial development in the chick by tracing neural crest cells through the radio-autographic labeling of dividing cells with tritiated thymidine (3H-TdR) (Johnston, 1966). This technique was also used by Drew Noden in 1975 for the same purpose. Realizing that neither the specificity (due to contamination of neighboring cells by the marker released by the dying labeled cells) nor the stability (because the label becomes diluted as the cells divide) of the marker were insured by this technique, Johnston, Noden, and their colleagues turned to the quail-chick marker system to investigate the migration and fate of the cephalic neural crest cells. These authors clearly confirmed the participation of the cephalic neural crest to the mesenchyme of the head and the jaws (see Le Douarin, 1982, for a review).

Christiane Le Lièvre and I undertook experiments aimed at deciphering the role of the cephalic neural crest cells on morphogenesis of the head from the early 1970s onward. Our aim was to see to what extent the neural crest contributes to the head skeleton and what was the respective part of the ectoderm (via the neural crest) and the mesoderm in both cephalic skeleton and connective tissues. For this purpose (in contrast to the experiments done before, where small fragments of the neural tube labeled with 3H-TdR were grafted into unlabeled chick embryos), entire encephalic vesicles were exchanged between stage-matched quails and chicks. This allowed us to see whether the bones were entirely or only partly derived from the neural crest (Le Lièvre and Le Douarin, 1974, 1975; Le Lièvre 1974, 1978).

A massive migration of the neural crest cells from their dorsal origin to the surface of the developing brain and the facial and hypobranchial buds was observed. Apart from the striated muscles of the branchial arches and the vascular endothelium of all the blood vessels, which were derived from the host mesoderm, the connective and skeletal tissues of the face and of the frontal and parietal part of the skull were of neural crest origin. Striated myocytes, forming the iridal muscles, have recently been shown to also be neural crest derived (Creuzet et al., 2005) as well as the ciliary bodies and the corneal endothelium. The meninges of the telencephalon were entirely of neural crest origin (except for the blood vessel endothelium). These structures are mesoderm-derived in all the other parts of the CNS (Le Lièvre, 1974; Le Lièvre and Le Douarin, 1975).

The Neural Crest and Vertebrate Evolution

These embryological results together with other considerations led Gans and Northcutt (1983) to put forward their concept of the vertebrate “New head,” according to which emergence of the neural crest is essential for the evolutionary transition from the protochordates to the vertebrates. The extant form of cephalochordates, the amphioxus, generally considered to be similar to the putative vertebrate ancestor, is devoid of a neural crest. This is also the case for the urochordates (although neural crest-like cells have been reported in ascidians (Jeffery et al., 2004). Amphioxus has a poorly developed encephalic vesicle and is devoid of the sense organs that characterize the vertebrate head. According to Gans and Northcutt, the development of a head in the chordate phylum is linked to the appearance of the neural crest and coincides with a change in lifestyle. Amphioxus is filterfeeder, while vertebrates became predators. This was made possible thanks to the acquisition of sense organs (vision, smell, audition), which developed from the anterior part of the neural primordium from placodes that, like the neural crest, are vertebrate innovations. The vertebrate brain became more and more complex and efficient through the development of associative neural structures, especially in the forebrain, midbrain, and cerebellum.

The work that we did in the late 1980s and early 1990s with Gérard Couly and Olivier Pourquié, and which consisted in constructing the fate map of the anterior neural plate, brought about interesting data along this line. By constructing the fate map of the anterior part of the neural plate and thus following the development of the early neural primordium with Gérard Couly, we have shown that, as in its original configuration in jawless vertebrates (hagfish and lampreys), the anterior-most part of the early neural primordium corresponds to the diencephalon (thalamus, hypothalamus, and pituitary gland) with only a modest development of the telencephalon dorsally. The diencephalon corresponds to the anterior end of the notocord, a vertebrate-organizing center that plays an important morphogenetic role at different steps of body plan patterning.

Olivier Pourquié in his postdoctoral work demonstrated that the differentiation of the paraxial mesoderm (cephalic and somitic) into cartilage and bone depends upon a signal arising from the notochord (Pourquié et al., 1993), later identified as the secreted molecule sonic hedgehog (Shh). The notocord present up to the mesencephalon-diencephalon junction thus accounts for the formation of the vertebral column and the occipital region of the skull. The evolution of the vertebrate phylum is characterized by the development of the cerebral hemispheres, which peaks in nonhuman primates and humans. We focused our attention on the early developmental steps of the cerebral hemispheres and showed that they arise from the lateral areas of the anterior neural plate. After fusion of the neural folds and formation of the encephalic vesicles, these lateral areas are the site of intensive growth, so that they develop rostrally beyond the tip of the notocord and the adenohypophysis to form the telecephalon. The latter becomes “buried” inside the stomodeal cavity while maintaining its close relationships with the floor of the diencephalon (which yields the hypothalamus). Due to the absence of notocord and mesoderm at the telencephalic level, no skeleton of mesodermal origin develops to cover the “new brain” that appeared and enlarged during the course of evolution. This new brain was covered by cells of neural crest origin, which formed the forebrain meninges and the skull (optic and nasal skeleton, frontal and parietal bones). Thus, coevolution of the anterior brain and of the neural crest was critical for the development of higher cognitive functions in the most recent forms of vertebrates. Notably, this considerable development of the forebrain has been accompanied by the emergence of sense organs, the eyes that originate from the diencephalon and the smell organs whose precursors cells we have localized in the anterior neural fold. The fate map of the neural plate that we published in 1985 and 1987 (Couly and Le Douarin, 1985, 1987) has served as a reference for many investigations of the forebrain in mammals, birds, as well as Xenopus by other groups. Acquisition of higher brain functions in vertebrates was matched by a change in lifestyle as compared to the filter-feeder ancestors, the cephalochordates. Vertebrates became able to seek their food and later even became predators. Their facial skeleton, which is entirely derived from the neural crest (see Le Douarin, 1982), involves the first organ of predation, the jaw, which is already well developed in some teleost fishes. Evolution of the vertebrate head is therefore characterized by an increased participation of ectoderm via the neural primordium. The latter not only generates the brain but also the neural crest, which is critical to construct the face and yields a large part of the heart and of the head vasculature (endothelium excluded). In conclusion, the embryological analysis of neural crest ontogeny has shed new light on the evolution of the vertebrate phylum. This was recently confirmed by a series of studies that we performed on the role played by the neural crest on the development of the vertebrate brain.

The Neural Crest: A Signaling Center Regulating the Development of the Preotic Brain

The experimental demonstration that the neural crest has a major influence on brain development had not been reported before a series of studies carried out in my laboratory in recent years. I wish to describe how and why the experiments which led to this important notion were undertaken.

The origin of this work stems from the observation of several authors (see Le Douarin and Kalcheim, 1999, for a review) that Hox genes, which play a critical role in patterning the body in all bilateria, have, in vertebrates, their anterior limit of expression between the two rostral-most rhombomeres (r1 and r2). This means that most cephalic structures develop in a Hox-free domain. As far as the neural crest is concerned, the cells that migrate to the facial primordium and construct the facial skeleton are Hox-negative, whereas those forming most of the hyoid cartilage and the so-called cardiac neural crest, which contributes to the conotruncus of the heart (Kirby et al., 1985), express Hox genes of the first four paralogous groups. Each rhombomere (or pair of rhombomeres) is characterized by a combinatorial Hox gene expression (also designated as Hox-code). Mutational analyses carried out in the mouse have shown that Hox genes are critical for patterning these neural crest derivatives as well as for the development of the vertebral column from the paraxial mesoderm and for the development of the brain stem from the rhombencephalon (see Le Douarin and Kalcheim, 1999, and references therein).

The Hox-negative, anterior domain of the cephalic neural crest (CNC), which is responsible for the construction of the face and part of the skull (Couly et al., 1996), designated as FSNC (for facial skeletogenic neural crest) is clearly patterned by another genetic system which was shown to involve among others the vertebrate homologs of the Drosophila Orthodenticle and Emptyspiracle genes: Otx1, Otx2 and Emx1, Emx2, respectively.

The question that we raised was the following: is it possible to get a normal development of head and face skeleton if a fragment of the Hox-positive domain of the premigratory cephalic neural crest (e.g. r4–r8) is substituted for the anterior Hox-negative one? In previous work we had shown that the rostral-most neural fold down to the level where the epiphysis is formed (i.e., at the mid-diencephalic level) does not undergo the epithelio-mesenchymal transition (EMT) and therefore does not produce neural crest cells (Couly and Le Douarin, 1985, 1987). The problem was raised as to whether, after excision of the FSNC down to r3 excluded, the remaining rostral and/or caudal portion of the neural fold (NF) that were left in situ would regenerate neural crest cells able to construct the head skeleton. The result was that, in the absence of the FSNC (the NF corresponding to the posterior half of the diencephalon, the mesencephalon and r1 + r2) excised at 5–6 ss, that is, prior to the onset of neural crest cells emigration, the facial processes remained empty of neural crest cells and did not grow. Hence, a complete absence of facial structures ensued. Moreover, the brain was the site of major defects resulting in anencephaly. The telencephalon was severely reduced as well as the thalamus and optic tectum, which did not develop since the preotic brain remained open.

If a fragment of the Hox-positive NF was grafted rostrally to replace the rostral domain, morphogenesis of the head was equally disrupted. In contrast, within the Hox-negative domain, including the diencephalic, mesencephalic, and anterior rhombencephalic levels (r1–r2), the neural crest possesses a high regeneration capacity. For example, a quarter of the endogenous Hox-negative neural crest (i.e., belonging to the FSNC), whatever its level of origin (e.g., diencephalic, mesencephalic, or rhombencephalic), is able to reconstitute the entire facial and lower jaw skeleton and to restore brain morphogenesis as well (Creuzet et al., 2002). This means that the information encoding any particular element of the facial skeleton does not belong to the neural crest proper but is imposed on it by extrinsic cues. The foregut endoderm was shown to play a role in this morphogenetic process (Couly et al., 2002), and we could demonstrate that one of the signals involved is Sonic hedgehog (Shh) (Brito et al., 2006).

Moreover, gain of function experiments, in which Hox genes were selectively electroporated into the Hox-negative domain of the neural crest, have shown that expression of these genes inhibits the differentiation of the facial cartilages and bones (Creuzet et al., 2002). The molecular mechanism of this inhibition is presently under investigation in our laboratory.

The role of the cephalic neural crest (FSNC) in brain development was further investigated at the molecular level. One of the immediate effects of FSNC excision was to dramatically reduce the production of Fgf8 in the anterior neural ridge (ANR) and to a lesser extent in the isthmus, two regions of the brain anlage that have been recognized as “brain organizers” through the production of this signaling molecule. In the absence of the cephalic neural crest, the branchial arch ectoderm is also deprived of Fgf8 mRNA. The effect of Fgf8 on both facial and brain development is therefore critical, and the dramatic phenotype resulting from FSNC removal can be rescued by exogenous Fgf8 provided to the operated embryos through Sephadex beads placed in close contact to the ANR (Creuzet et al., 2006).

In still ongoing experiments, it has been shown that Fgf8 production by the ANR is regulated by the cephalic neural crest, which produces anti-Bmp4 secreted molecules like Noggin and Gremlin from the time they start to migrate and onward. Because Bmp4 is a strong antagonist of Fgf8 production (Ohkubo et al., 2002), the excision of the cephalic neural crest results in the failure of the development of the telencephalon, the thalamus, and the optic tectum, that is, the brain regions derived from the lateral territories of the rostral neural plate. Fgf8 is critical for this process, and the neural crest cells play a regulatory role in the production of this signaling molecule during the early stages of neurogenesis (Le Douarin and Creuzet, 2009).

Therefore, the role of the CNC in head development is not restricted to providing the cells that build the skeleton and connective tissues of the face. The neural crest also acts as an organizing center able to regulate the activity of both the ANR and the isthmus.

Cell Culture of Neural Crest Cells: Toward the First Demonstration of a “Neural Stem Cell”

The experiments aimed at disclosing the fates of the neural crest cells emerging from the various levels of the neural axis illuminated two characteristics of these cells: their capacity to give rise to a large number of different cell types and the fact that they migrate all over the developing embryo to settle in many places where they differentiate into a large variety of derivatives. In fact, there are virtually no organs or tissues in the vertebrate organism devoid of neural crest cells since, as Schwann cells, they line the nerves that travel with the smallest blood vessel ramifications.

This pluripotency and vast distribution all over the body are characteristics also shared with the blood cells. This led me to undertake an investigation on the actual developmental capacities of the neural crest cells by using clonal culture assays as had been so successfully done to study the hematopoietic cell lineage.

When I arrived in Nogent in 1975, I found appropriate conditions to develop in vitro cultures of the neural crest cells. Catherine Ziller, like me a former student of Etienne Wolff, took over the project together with Anne Baroffio, a postdoctoral fellow, and Elisabeth Dupin, a graduate student at that time. They developed a method that allowed clonal cultures of neural crest cells and provided them with a medium that, in principle, allowed the full expression of their differentiating capabilities. This led us to show that, as early as the migratory stage, neural crest cells from the cephalic level of the neural axis (CNCC) form an heterogeneous population of cells with different commitments. Fully committed precursors, giving clones with only one cell type, were found, as well as pluripotent progenitors, in respective proportions of about 20% and 80%.

Our problem raised by the CNC is that it yields not only derivatives of the “neural” type (such as neurons, glial cells, melanocytes, and peptidergic cells) but also cells of the mesenchymal type (cartilage, bone, and connective tissues), which in other parts of the body are of mesodermal origin. The question was therefore whether these two types of cells could be found in the progeny of single CNCC. Analysis of the phenotypes represented in the colonies showed that the capacities to produce cells of the neural and mesenchymal lineages coexist in the CNCC. The number of the neural crest cells recorded as being able to yield elements belonging to these two cell lineages in their progeny was low in our first experiments (Baroffio et al., 1988, 1990, 1991a, b; Dupin et al., 1990) but increased recently for two reasons: first, because we could show that the signaling molecule Shh, applied at a defined time course during the differentiation process, enhances significantly the number of cells differentiating into chondrocytes in the presence of other cells of the neural type. Secondly, we showed that numerous cultures contained cells expressing Runx2, a gene considered as a marker for bone differentiation (Calloni et al., 2007, 2009).

Moreover, as also shown by the Graham group (McGonnell and Graham, 2002), the trunk neural crest which in vivo does not yield cells of the mesenchymal lineage turned out to be able to do so in appropriate culture conditions.

Building on these results, we could propose a cell lineage model that accounts for the diversification of neural crest derivatives from a multipotent stem cell (Le Douarin et al., 2004). This first identification of a “neural stem cell” (although at that time, the self-renewal capacity of this cell had not been demonstrated) in the nervous system was confirmed by other groups in the United States and was followed by the demonstration of neural stem cells in the CNS.

This work is now pursued in our group by Elisabeth Dupin and several coworkers. We showed that several pluripotent progenitors such as those able to give rise to glial (G), pigment (M), and smooth muscle (F) cells (GMF precursors), or only glial cells and melanocytes (GM precursors), are endowed with self-renewal capacities and thus can be considered bona fide as “stem cells” (Trentin et al., 2004; Le Douarin et al., 2004). It was obvious that a parallel could be established between the segregation of cell lineages in the neural crest and in the hematopoietic system.

This led to the search for growth and survival factors able to promote the proliferation and differentiation of a selected set of precursor cells in each type of neural crest derivatives. The identification of molecular markers specific for the different cell types arising from neural crest progenitors has been a prerequisite for the analysis of the phenotypes present in the cultures. In the 1980s onward, my laboratory engaged in the production of monoclonal antibodies directed against molecular markers for the avian neural crest cells and their derivatives and also for other cell types. Some of these monoclonal antibodies have been studied in depth. This is the case for example, for the SMP monoclonal antibody, which allowed the cloning of the gene and the purification of the Schwann cell myelin protein, which exhibits a strict specificity for oligodendrocytes in the CNS and the Schwann cells in the PNS (Dulac et al., 1988, 1992; Dulac and Le Douarin, 1991). SMP was discovered and studied by Catherine Dulac, now professor at Harvard University, and by the late Patricia Cameron-Curry who died of acute lymphocytic leukemia 1 month after being diagnosed at the age of 35. Patricia came to our laboratory as an Italian postdoctoral fellow and decided to stay in France. She had just been appointed to an INSERM position when she suddenly fell sick. This was for us a terrible shock and a great loss.

Other monoclonal antibodies were useful in our studies on chimeras because they recognized species and cell type–specific antigenic determinants and thus allowed us to recognize quail from chick cells as well as their differentiated phenotypes in chimeric birds.

Cytokines Selectively Active on Subpopulations of Neural Crest Cells

Our next goal was to identify the factors provided to the neural crest cells by the environment they meet at the term of (or during) their migration and which make them survive, grow, and differentiate. Among the secreted factors we studied, endothelin 3 (ET3) was the most interesting. Laure Lecoin, Ronit Lahav, Valérie Nataf, and Elisabeth Dupin worked very successfully on this project (Lahav et al., 1996, 1998; Nataf et al., 1996, 1998a, b; Lecoin et al., 1998), which is presently pursued actively by Elisabeth Dupin and myself.

We could show that ET3 exerts a proliferative effect on the neural crest precursors, which are endowed with a specific seven-transmembrane-domain receptor for this peptide. These precursors are essentially of two kinds, those which invade the gut and later on differentiate into the ENS, and the future melanocytes which migrate to the skin. ET3 is produced by the superficial ectoderm and by the mesenchymal wall of the gut. We found that these two kinds of neural crest progenitor cells express two different (although closely related) ET3-receptor genes in avian species, while in the mouse and humans only one ET3-receptor exists on both cell types called ETRB. Laure Lecoin cloned the melanocytic ET3-receptor in chick and quail that she designated ETRB2 (Lecoin et al., 1998), which is encoded by a different gene from the avian ETRB (designated as ETRBI) expressed in the PNS (Nataf et al., 1996).

In the avian embryo, the precursors of melanocytes exit from the neural tube later than those which have taken the dorsoventral migration pathway. They were found to express ETRB2 and not ETRB1. If the early migrating crest cells are cultured in vitro, they express in their majority the ETRB1 gene. In the presence of ET3, a switch of ETRB1 to ETRB2 expression takes place as soon as 24 hours of exposure to the cytokine. One day later it appears that the cells have proliferated much more actively in presence of ET3 than in control cultures and they massively differentiate into melanocytes in the following days. The presence of neural crest cells expressing transiently both receptors suggests that ET3 is able to activate the ETRB2 genes both in culture and in the skin but not in the gut environment where ETRB1 remains the only ET3 receptor gene activated (Lahav et al., 1998).

In following work, we were able to demonstrate that the ET3 receptors (ETRB1 or ETRB2) were either continuously expressed or at least inducible in fully differentiated melanocytes and glial cells (like Schwann cells). If subjected to ET3 in vitro, these cells were induced to proliferate and to dedifferentiate into precursors of the GM or GMF types which could self-renew and later on yield melanocytes (M), glial cells (G), and/or myofibroblasts (F) (Dupin et al., 2000, 2003; Real et al., 2005, 2006).

These experiments were a striking demonstration of the capacity of differentiated cells to dedifferentiate and reacquire embryonic capacities. The GM and GMC precursors are able to self-renew. Therefore, under the proliferative stimulation exerted by ET3, melanocytes and glial cells are able to yield cells that have acquired a stem cell status.

Following Cell Migrations and Morphogenetic Movements during Neurogenesis of the Brain

In the late 1980s, the dominant thinking was that cell migrations in the encephalic vesicles were essentially radial. Tangential migrations had not been described, whereas radial migration of the neuroblasts had been clearly demonstrated by labeling the still dividing neuroblasts in the mammalian fetuses with tritiated thymidine. In 1989, two groups, using the Q/C chimera system (Balaban, Teillet, and Le Douarin) or LacZ carrying retroviruses as cell markers (Connie Cepko’s group at Havard), published side by side two articles in Science (Balaban et al., 1988; Walsh and Cepko, 1988). Both showed that extensive tangential migrations actually occur during neurogenesis in the mammalian and avian forebrain, including the cerebral hemispheres, a notion now widely accepted.

In my laboratory, these explorations were further pursued on the cerebellum by Marc Hallonet, a graduate student. The results described in Marc’s Ph.D. thesis changed significantly the current view about the development of this part of the brain. First, it was established that, in contrast to prior belief, the cerebellar cortex did not originate entirely from the metencephalic vesicle. An important contribution from the mesencephalon was demonstrated, such that the cerebellar primordium encompasses the territory expressing the homeobox gene En2, and indeed, as later shown, agenesis follows the targeted mutation of this gene in the mouse. The construction of chimeric brain showed that the cerebellum arises from a territory equally distributed on each side of the constriction known as the midbrain-hindbrain junction. In addition, the assumption according to which cells of the molecular layer originate from the external granular layer was found to be incorrect. We could show that these cells undergo an inward-outward migration from the ventricular epithelium, in the same way Purkinje cells do (Hallonet et al., 1990).

The Role of Cell–Cell Interactions in Gene Regulation within the Differentiating Neural Epithelium

A Japanese group headed by Harukazu Nakamura, a former postdoctoral fellow in my laboratory, and the French team of Dr. Alvarado-Mallard in Paris, using the Q/C transplantation technique, discovered that the midbrainhindbrain junction is an important organizing center in brain development.

The two groups showed that transplantation of neuroepithelial grafts from this region to the diencephalon or rhombencephalon resulted in the induction of the En2 gene in the host’s neighboring neural epithelium and in the differentiation of tectal or cerebellar structures depending on the site of implantation. This led to the discovery by Dr. Salvador Martinez and colleagues (Crossley et al., 1996) that the critical factor in this induction is FGF8, naturally produced in the midbrain-hindbrain junction and fated to become the isthmus.

The fact that transcription factors expressed in the brain during development can be environmentally regulated prompted me to investigate the regulation of Hox gene expression in the rhombencephalon, a piece of work undertaken by Anne Grapin in association with Gérard Couly. When we started to investigate the problem of gene regulation in the hindbrain, the general assumption was that the expression of Hox genes in various levels of the brain was cell-autonomous and nothing was known about the upstream regulation of these genes. By performing a series of heterotopic rhombomere transplantations at the early neurulation stages between quail and chick embryos, we have shown that in fact Hox gene expression at the various rhombencephalic levels obeys extrinsic cues and is regulated by signals transmitted through the neural epithelium itself and the paraxial mesoderm. Retinoic acid acts on this process by “posteriorizing” the anterior levels of the brain through Hox gene induction (Grapin-Botton et al., 1995).

Our experiments have also revealed that the potentiality to express Hox genes extends up to the prosencephalon. Indeed, when transplanted posteriorly, prosencephalic neuroepithelium was induced to express Hox genes corresponding to the position of the transplant along the neural axis. Thus, in normal development either the inductive signal is not present in the prosencephalic and mesencephalic vesicles, or it is inhibited by antagonistic cues. Several experimental results point to the distribution of this signal as a postero-anteriorly decreasing gradient, a notion compatible with the hypothesis that retinoic acid could be involved in mediating Hox gene induction.

Transposition of rhombomeres along the neural axis does not modify Hox gene expression in transplants grafted more rostrally than their normal position. In contrast, caudal transposition results in “posteriorisation” of the neuroepithelium as far as expression of Hox genes is concerned, thus illustrating in vertebrates the “posterior dominance” demonstrated in insects. When rhombomeres 5/6 were transposed to the level or rhombomeres 7/8, this change in the Hox-code was followed by a homeotic transformation of the transplant phenotype. The transplant differentiated neural structures corresponding to its new AP position.

These experiments thus indicated that regulation of the Hox-code at each AP level of the neural axis depends upon positional cues and showed the crucial role of Hox genes in neural specification at the rhombencephalic level.

Neurulation in Amniotes Revisited

From the work of Hans Spemann, neurulation was considered to result from an induction of the ectoderm by the “organizer” and its derivative, the notocord. The resulting neural plate was thought to be originally formed by a homogeneous sheet of epithelial cells in which the notocord introduces heterogeneity by inducing the neuroepithelial cells to become the floor plate, a medial structure that plays an important role in patterning the neural tube. The accepted view was that the floor plate is induced by the notocord via the secreted protein sonic hedgehog (shh). This induction would lead the floor plate cells to produce a transcription factor of the forkhead family HNF3bβ which in turn would control the production of Shh protein by floor plate cells. By using the quail-chick marker system in the embryo in ovo, it was possible to trace the fate of the avian organizer (Hensen’s node cells) throughout the entire neurulation process. It turned out that the cells of the organizer express HNF3bβ from the onset of gastrulation onward. Moreover, they yield not only the notocord, as previously thought, but also the floor plate which accordingly is derived, not from the ectodermal but from the mesodermal layer and a stripe of cells in the dorsal endoderm. During gastrulation and neurulation, Hensen’s node moves along the anteroposterior axis according to the process called “regression” and leaves in its wake these three mediodorsal structures (Catala et al., 1995, 1996; Le Douarin et al. 1998). This and other experiments thus challenged the role of the notocord in floor plate induction during normal development. In fact, the floor plate develops in a cell-autonomous manner, and the notocord is not required for inducing the floor plate. Those observations are supported by several genetic data, particularly by the existence of mutants in Zebrafish (like floating head) in which a floor plate develops into a normally patterned neural tube in the total absence of a notocord.

Our results therefore led to a reconsideration of the classical notions about the process of gastrulation and neurulation in the vertebrate phylum (Charrier et al., 1999; Le Douarin et Halpern, 2000 and references therein). They have also disclosed a novel role for the protein Shh during neurulation. We have shown that, if the development of the notocord and floor plate is prevented by extirpation of Hensen’s node, the neural tube and the paraxial mesoderm are the site of massive cell death. The Shh morphogen thus acts as a survival factor, and one of the primary roles of these midline structures in the vertebrate embryo is to prevent the neural and mesodermal cells from triggering their cell death program (Charrier et al., 2001). This is further attested by the fact that after the removal of Hensen’s node in the six somite-stage (6 ss) embryo, the development of its posterior part can be rescued if it is provided with an exogenous source of Shh.

In collaboration with Dr. Patrick Mehlen and coworkers at the University of Lyon (France), we could demonstrate, in this system, that the Shh receptor Patched (Ptc) belongs to the family of “dependence receptors” characterized by the fact that in absence of their ligand, they induce cell death by activating cellular caspases through the liberation of a “death domain” from the intracellular part of their molecule (Thibert et al., 2003).

Therefore, one of the major roles of the notocord-floor-plate complex at these early stages of neurulation is to insure the survival and induce the growth of the cells of the neural tube and of the paraxial mesoderm. This analysis of neurulation through the use of quail/chick chimeras has profoundly revised current notions about neurulation in amniote vertebrates (Teillet et al., 1998a, 1998b; Thibert et al., 2003; Charrier et al., 2005).

Chimeras in the Study of Brain Functions

For about 10 years (from 1985 on), I extended our studies on embryos up to the posthatching stages. After seeing that the neural chimeras were able to both hatch and survive, we could tackle problems dealing with some functional aspects of brain development.

I had the privilege of being elected as a member of the Neuroscience Research Program (NRP) in 1983. This Program was founded in 1962 by Francis O. Schmitt (1903–1995), then Professor at MIT, and chaired by him until 1974. The NRP is an informal college of scholars and research scientists whose purpose was and still is to promote study of the brain. When Francis O. Schmitt retired, the NRP was transferred from Boston to the Rockefeller University in New York and its new chairman became Gerald Edelman. Members of the program met twice a year for a few days at the Rockefeller University in New York, where they presented their new results or listened to invited scientists. When I presented our experiments showing that Q/C neural chimeras were able to hatch and remained in a healthy condition for a long period after birth, Peter Marler, a specialist in bird ecology, then a NRP member, was in the audience. He reported these experiments to the fellows of his laboratory, one of whom, Evan Balaban, already a Ph.D. and thinking of a postdoc, was interested by the model. He thought that it could be applied to study the problem of “nature versus nurture” in behavior. What type of behavior would a chimera exhibit when regions of the brain had been replaced by those from another bird?

When he came to Nogent, Evan Balaban chose to study the species-specific crow (or call) induced in young birds by testosterone implants. He found that crows were different in young quails and chickens. Moreover, movements of the head accompanying crowing were also different between the two species. Evan decided to look for the brain site(s) driving vocalization and behaviors linked to crowing. Marie-Aimée Teillet took part in the project and taught Evan how to exchange specific neuroepithelial areas between E2 quail and chick embryos. At that time encephalic vesicles are not yet vascularized and fusion of graft and donor neuroepithelium takes place rapidly. Numerous Q/C brain chimeras hatched, and it appeared that the crowing-specific area was in the mesencephalon. A chicken grafted with a quail mesencephalon emitted the quail typical crowing. However, simultaneous head movements were of the chicken type. When he returned to the United States and established his own laboratory, Evan was able to assign the origin of the typical head movements, accompanying the crow in the quail, to the brain stem (Balaban et al., 1988; Balaban, 2005).

This work, very demanding as far as the quality and precision of the microsurgery was concerned, showed that complex behaviors like crowing are genetically determined in definite areas of the neural epithelium of the encephalic vesicles a long time before neuronal differentiation takes place. Thus, at the early stages of neurogenesis, the neural plate is far from being a homogeneous structure with interchangeable regions. On the contrary, the neural epithelium is already the site of an underlying structuralization that involves genetic and species-specific inbuilt characteristics. During neurogenesis, the various regions so defined acquire their functionality together with their differentiation in the context of the connections that they establish with neighboring structures.

These experiments showed that the quail regions which define the crow as well as the head movements develop in a species-specific manner, whether they are on their own or in a foreign environment. Moreover, these regions develop autonomously, even though the connections they establish with other foreign brain structures are critical for the full expression of their functional characteristics.

The same observation was made in another series of experiments that involved a pathological trait determined by a Mendelian mutation leading to epilepsy.

The Epileptic Chickens

Seeing the possibility of exchanging parts of the brain between two embryos, Pr. Robert Naquet, a highly recognized specialist in epilepsy, wanted to use the avian chimera model to try and define the origin of an autosomic Mendelian recessive form of epilepsy in a strain of chicken discovered in Canada by Roy Crawford in 1972. Genetic forms of epilepsy are known in humans and are characterized by seizures triggered, among other things, by visual or auditory stimuli (e.g., intermittent light). They are considered to be a subcortical type of epilepsy. However, what generates seizures and what brain area(s) is (are) involved in this process was not well known, though it had been proposed that the focus is located in the brain stem.

As mentioned earlier, the embryonic grafts of neural epithelium are rejected in interspecific chimeras 1–3 months after the young bird has become immunologically competent, an event which takes place about 2 weeks after birth. During our work on the host’s immunological response to neural grafts, we made an observation that opened a novel research avenue. Neural grafts between MHC-different chickens were permanently tolerated. This led our group to develop a series of experiments in collaboration with Pr. Robert Naquet and Dr. Cesira Batini, a neurophysiologist from the CNRS in Paris. The disorder that affected the homozygous epileptic chickens (epi/epi) consisted of seizures of the “grand mal” type following either light or sound stimulation. By transplanting entirely or partly either the prosencephalic, mesencephalic, or rhombencephalic brain vesicles, the neural pathways involved in the onset of the photic or audiogenic forms of epilepsy could be determined (Teillet et al., 2005). It was shown that the nucleus mesencephalicus (pars dorsalis) triggers the seizures after processing either stimulus (sound or light). The “epi” chicken mutant can thus be considered as a unique animal model for the so far poorly understood subcortical types of human epilepsy. The work on chicken epilepsy has given rise to several articles (Guy et al., 1992; Fadlallah et al., 1995; Teillet et al., 1995; Batini et al., 1996).

From Neurobiology to Immunology: Revisiting the Problem of Self/Non-Self-Discrimination in Postnatal Chimeras

The experiments that we performed in the 1970s to explore the fate of the neural crest cells exclusively concerned events taking place during embryogenesis. When I gave talks, however, I was often asked about the immunological status of the grafted quail cells and their numerous progeny in posthatching chimeras.

When a Japanese postdoctoral fellow, Dr. Masae Kinutani, came to the laboratory in 1982, she was enthusiastic about a project that would explore the hatching ability of Q/C spinal cord chimeras and the fate of the graft after birth, when the host’s immune system has become fully competent. Marie-Aimée Teillet obtained the first hatching of a chimera. She gave me a large photograph of this bird that I keep as a precious remembrance. Masae Kinutani, under the efficient teaching of Marie-Aimée, became one of the most skillful “transplanters” in the laboratory and pursued the project.

The rate of hatching was about 1 out of 10 operated embryos but, once born, the chimeras generally were healthy. Their health did not last for long, however, as birds with a graft at the brachial level developed a paralysis of the wings and in most cases eventually died. A few animals, however, recovered complete motility and survived. The grafted segment of spinal cord appeared infiltrated with macrophages and lymphocytes, and the inflammatory process further invaded the host nervous tissues. These lesions were similar to those observed in animals with induced experimental allergic encephalomyelitis (EAE) and to those occurring in humans afflicted with multiple sclerosis (MS). In addition, the chimeric birds developed neuritis in the peripheral nerves derived from the grafted spinal cord.

This pathology of the chimeras was clearly the manifestation of graft rejection but, curiously, the first signs appeared long after immunological maturity of the host. We interpreted this delay by the fact that CNS tissues have a privileged immunological status on one hand and express no (or only a little) class I and class II MHC antigens on the other. It is likely that the first immune attack on graft-derived tissues takes place in the peripheral nerves, devoid of the protective blood–brain barrier present in the CNS. The T-cells recognize neural and glial antigens and thus become activated and able to attack the CNS in the same way as in EAE, where T-cells become activated by systemic injection of neural antigens, for instance myelin basic protein (MBP). The chimeric birds thus appeared to be an experimental model for MS (Kinutani et al., 1986).

As far as developmental immunology is concerned, these results were at odds with the common assumption, according to which antigens present during development of the immune system are later recognized as self (for a discussion, see Coutinho, 2005). To understand whether the delay observed before rejection of the graft was due to the privileged status of the nervous tissue or whether it was related to the presence of the graft in the embryo, we undertook, with Claude Martin, Maurice Belo, Catherine Corbel, and a young Japanese researcher, Hiroko Ohki, a series of studies in which quail nonneural tissues, the limb bud and the bursa of Fabricius, were grafted into chick embryos. In both cases, the graft pursued its development in the chick, reaching its species-specific size according to its own timing.

Many chimeras of this type were obtained. All of them rejected the foreign wing acutely, starting at various times during the first two posthatching weeks (i.e., when the host’s immune function reaches maturity). The wing was totally destroyed after 2 months. Thus, the delay typical for neural tube grafts was not observed for nonneural tissues. This was confirmed by Maurice Belo for bursal grafts (Belo et al., 1985; Corbel et al., 1987).

At that point, it appeared relevant to investigate the immunological status of wing bud grafted between chickens of different MHC. These strains were available from the INRA laboratory of genetics belonging to the Institut National de Recherche Agronomique (INRA). The grafted wing was not rejected, contrary to the outcome in Q/C wing-chimeras. However, tolerance was not complete since rejection crises occurred, separated by episodes during which inflammation regressed (Corbel et al., 1990).

Inspired by a paper in Nature (Fehilly et al., 1984), I was anxious to see whether manipulating the immune system of the chimera could induce permanent tolerance of the quail wing by the chicken host. On the front page of the journal was a strange animal, a sheep-goat chimera in which the tissues from the two species formed a patchwork while entertaining peaceful relationships. What were the differences between the Q/C wing-chimeras and the sheep-goat chimeras? As mammalian chimeras result from the aggregation of two (or more) morulae, there is a chance that virtually all tissues of the animal contain cells from the two species. There is no telling the host from the recipient in this case while, in Q/C wing, bursa, or neural grafts, recipient tissues were clearly dominant over donor tissues.

I reflected that chimerism in the blood or in the thymus could be decisive for the reciprocal tolerance in sheep-goat chimeras, as thymus is the site of T-cell differentiation and as mouse blood chimeras produced at birth are tolerant to skin grafts of the MHC-type of the injected foreign blood cells in allogeneic combinations (Billingham et al., 1953). I knew, however, from a conversation with Milan Hasek that, in birds, this kind of tolerance is not induced by heterospecific blood chimerism. Consequently, we devised an experimental design in which the donor quail embryo provided not only a wing bud but also the four thymic epithelial anlagen of the third and fourth pharyngeal pouches substituted for their counterpart in E4 chick embryos, host and donor being stage matched.

The thymus operation was delicate. Claude Martin’s skills in microsurgery were decisive, and she taught Hiroko Ohki and Maurice Belo. As described in our paper in Science (Ohki et al., 1987), one out of 10 animals hatched. Out of the 16 birds that hatched, 14 showed tolerance of the quail wing. In 3 of them slight signs of rejection appeared after about 40 days, much later than in Q/C limb-only chimeras. Two did not show tolerance. The complete thymic lobes of all these double limb-thymus chimeras were studied for chimerism analysis: quail cells appeared to form the thymic epithelial stroma in all the chimeras that were tolerant and not in the others that were not tolerant. However, substitution of thymic epithelial rudiments was usually incomplete. The proximity of the branchial arch arteries made the operation difficult because hemorrhages were fatal. This technical problem made the experiment even more interesting than expected. Tolerance turned out to be induced permanently if only one-third of the thymic lobes was chimeric (Belo et al., 1989). This meant that chick T-cells differentiating in contact with the quail thymic epithelium not only failed to aggress the quail graft but were able to “protect” the graft from the chick T-cells that had differentiated in the purely chick thymic lobes. When no tolerance was induced, none or very few thymic tissues were found to be chimeric.

This significant finding meant that tolerance to self did not result exclusively from the elimination of autoreactive T-cells in the thymus. The process was shown to be incomplete: T-cells with high affinity for self-components are currently found in the periphery and become harmful in autoimmune diseases. The Q/C double chimeras showed that a mechanism at work prevented these T-cells from being activated in an antigen-specific manner.

Tolerance mediated by these cells is “active,” differently from the widely accepted dogma of the default mechanism, that is, autoreactive cell elimination in the thymus. This work was recorded in a series of papers (see for review Le Douarin et al., 1989, and Salaün et al., 2005).

At this point we had animated discussions with immunologists, particularly with Pr. Max Cooper from the University of Birmingham in Alabama, who spent a sabbatical year with us, and Pr. Antonio Coutinho, who was leading an immunobiology research unit at the Pasteur Institute. Although a number of important concepts in fundamental immunology were inspired by experimental results obtained in the chick, in modern times the classical model in this science is the mouse. Therefore, we have had to convince immunologists that we had made an observation of general interest. Openminded and creative, Antonio Coutinho was immediately interested by the quail/chick chimera model and by the insights it was yielding about the mechanisms of self/non-self-recognition. We decided that we should try and reproduce these experiments in the mouse model. Josselyne Salaün in our laboratory successfully carried out this project together with Antonio Bandeira from the Pasteur group. Josselyne Salaün had been combining in vivo and in vitro studies on the mouse embryo in order to sort out the successive ontogenic steps of T-cell differentiation (Salaün et al., 1986) and was well prepared to tackle this problem.

Since microsurgery on the early mammalian embryos is not feasible, athymic nude mice were elected as recipients for isogeneic or allogeneic thymic epithelium grafting. Nude mice are devoid of T-cells and therefore immuno-incompetent. In both combinations, T-cell function was rescued by HC from the host, which colonized the grafted thymic epithelium, differentiating into T-lymphocytes that migrated to the periphery. We demonstrated that, in allogeneic combinations, the nude mice engrafted with the thymic epithelium were tolerant to both skin grafts of their own haplotype and of the thymus haplotype while rejecting third-party grafts. Yves Modigliani, a graduate student in Antonio Coutinho’s laboratory, showed that this tolerance was mediated by CD4 T-cells. Antonio Coutinho designated it as “dominant” tolerance. These T-cells, whose existence was subsequently confirmed by many other groups (see Le Douarin et al., 1996, for a review, and Coutinho, 2005) and are called “regulatory T-cells” (Treg), had to be characterized. The first important step toward their molecular characterization was due to Sakaguchi and colleagues (1982), who found that such cells express as a surface marker CD25 in addition to CD4. A new research avenue in immunology was thus initiated, which is now expanding vigorously. At the Congress of the International Union of Immunological Societies held in Montreal on July 16 to 22, 2004, where I was invited to give a lecture on the contribution of my laboratory to immunology, several symposia were devoted to regulatory T-cells and the importance they may have in transplantation medicine.

Concluding Remarks

I wish to say that I consider it an honor to be invited to write about my own scientific experience in this prestigious series of autobiographies. I received this invitation in 2004 and accepted it with great pleasure. However, when I started to write about the past, I realized that I was so busy and had so many ongoing projects, that I did not feel able to pursue this task at that time. I put my writing aside and nearly forgot it. Fortunately, Pr. Larry Squire did not forget and encouraged me to go on. I wish to thank him for his persistence.

Now, time has passed and I can ponder my contribution to science with some composure. As a developmental biologist, I had the chance to make an observation that led me to devise a technique which turned out to be useful for deciphering some of the developmental features of many systems in the vertebrate embryo. Among those, the nervous and hematopoietic ones have been my favorites. About the former, I could show that the neural crest, a transitory and very unobtrusive structure of the early embryo (and a more or less abandoned topic at that time), is in fact a major player in vertebrate embryogenesis and even in the evolution of this phylum. It plays a critical role in building the head and, as shown recently, the brain. Several aspects of neural development were highlighted in this work: the plasticity of the neuroblasts and the influence of environmental factors on the final phenotypes they exhibit at the end of the differentiation process; the existence of a stem cell in the neural crest (at a time when stem cells were not the popular subject they are today), indeed the first example of “neural stem cells” ever mentioned; the evidence of the real cell movements involved in neurulation in amniotes. These cell movements have disclosed mechanisms that had not, so far, been correctly interpreted.

The fact that I led parallel research projects on the nervous and the hemopoietic systems led me with my colleagues to bring about the concept of dominant tolerance, now well illustrated by the large current of work on regulatory T-cells.

In conclusion, these series of experiments are characterized by the combination of a large diversity of themes, together with an underlying unity. This unity lies not only in the technology, a combination of classical embryological methods and molecular biology, but also in the rationale underlying the problems tackled and the experimental approaches elected to unravel them. This work was accomplished thanks to the collaborations of many gifted scientists, Ph.D. students, postdoctoral fellows, and colleagues, to whom I wish to express my heartfelt gratitude.

Selected Bibliography

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Balaban E, Teillet MA, Le Douarin N. Application of the quail-chick chimera system to the study of brain development and behavior. Science 1988;241:1339–1342.

Baroffio A, Dupin E, Le Douarin, NM. Clone-forming ability and differentiation potential of migratory neural crest cells. Proc Natl Acad Sci USA 1988,85: 5325–5329.

Baroffio A, Dupin E, Le Douarin NM. Cell lineage studies in avian neural crest ontogeny. In Lauder J ed. Proceedings of the Second Conference of the Institute of Dev. Neuroscience and Aging Society for Developmental Neuroscience on Molecular Aspects of Development. New York: Plenum Press, 1990; 53–62.

Baroffio A, Dupin E, Le Douarin NM. Common precursors for neural and mesectodermal derivatives in the cephalic neural crest. Development 1991a;112: 301–305.

Baroffio A, Dupin E, Le Douarin, NM. Clone-forming ability and differentiation potential of migratory neural crest cells. Proc Natl Acad Sci USA 1991b;85: 5325–5329.

Batini C, Teillet MA, Naquet R, Le Douarin NM. Brain chimeras in birds: application to the study of a genetic form of reflex epilepsy. Trends Neurosci 1996;19: 246–252.

Belo M, Martin C, Corbel C, Le Douarin NM. A novel method to bursectomize avian embryos and obtain quail/chick bursal chimeras. I. Immunocytochemical analysis of such chimeras by using species-specific monoclonal antibodies. J Immunol 1985;135:3785–3794.

Belo M, Corbel C, Martin C, Le Douarin N. M. Thymic epithelium tolerizes chickens to embryonic graft of quail bursa of Fabricius. Int Immunol 1989;1:105–112.

Billingham RE, Brent L, Medawar PB. Actively acquired tolerance of foreign cells. Nature 1953;172:603–606.

Brito JM, Teillet MA, Le Douarin NM. An early role for sonic hedgehog from foregut endoderm in jaw development: insuring neural crest cell survival. Proc Natl Acad Sci USA 2006;103:11607–11612.

Calloni GW, Glavieux-Pardanaud C, Le Douarin NM, Dupin E. Sonic Hedgehog promotes the development of multipotent neural crest progenitors endowed xith both mesenchymal and neural potentiels. Proc Natl Acad Sci USA 2007;104:19879–19884.

Calloni GW, Le Douarin NM, Dupin E. High frequency of cephalic neural crest cells shows coexistence of neurogenic, melanogenic, and osteogenic differentiation capacities. Proc Natl Acad Sci USA 2009;106:8947–8952.

Catala M, Teillet, MA, Le Douarin NM. Organization and development of the tail bud analyzed with the quail chick chimaera system. Mech Dev 1995;51: 51–65.

Catala M, Teillet MA, De Robertis EM, Le Douarin NM. A spinal cord fate map in the avian embryo: while regressing, Hensen’s node lays down the notochord and floor plate thus joining the spinal cord lateral walls. Development 1996;122: 2599–2610.

Charrier, JB, Teillet MA, Lapointe F, Le Douarin NM. Defining subregions of Hensen’s node essential for caudalward movement, midline development and cell survival. Development 1999;126:4771–4783.

Charrier JB, Lapointe F, Le Douarin NM, Teillet MA. Anti-apoptotic role of Sonic Hedgehog protein at the early stages of nervous system organogenesis. Development 2001;198:4011–4020.

Corbel C, Belo M, Martin C, Le Douarin NM. A novel method to bursectomize avian embryos and obtain quail/chick bursal chimeras. II. Immune response of bursectomized chicks and chimeras and post-natal rejection of the grafted quail bursas. J Immunol 1987;138:2813–2821.

Corbel C, Martin C, Ohki H, Coltey M, Hlozanek I, Le Douarin NM. Evidence for peripheral mechanisms inducing tissue tolerance during ontogeny. Int Immunol 1990;2:33–40.

Couly GF, Le Douarin NM. Mapping of the early neural primordium in quail-chick chimeras. I. Developmental relationships between placodes, facial ectoderm, and prosencephalon. Devel Biol 1985;110:422–439.

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Couly G, Le Douarin NM. The fate map of the cephalic neural primordium at the presomitic to the 3-somite stage in the avian embryo. Development 1988;103: 101–103.

Couly G, Le Douarin NM. Head morphogenesis in embryonic avian chimeras: evidence for a segmental pattern in the ectoderm corresponding to the neuromeres. Development 1990a;108:543–558.

Couly G, Le Douarin NM. Mapping of the cephalic ectoderm at the neurula stage in avian chimeras. In Le Douarin N, Dieterlen-Lièvre F, Smith J, eds The avian model in developmental biology: from organism to genes. Paris: Editions du CNRS, 1990b; 11–24.

Couly G, Coltey P, Le Douarin NM. The developmental fate of cephalic mesoderm in quail-chick chimeras. Development 1992;14:1–15.

Couly G, Coltey P, Le Douarin, NM. The triple origin of skull in higher vertebrates. Development 1993;117:409–429.

Couly G, Coltey, P, Chéron G, Abadie V, Martelli H, Le Douarin NM. Rhombomères, code Hox, crête neurale et malformations de la face. Méd Sci 1994;10:151–162.

Couly G, Coltey P, Eichmann A, Le Douarin NM. The angiogenic potentials of the cephalic mesoderm and the origin of brain and head blood vessels. Mech Dev 1995;53:97–112.

Couly G, Grapin-Botton A, Coltey P, Le Douarin NM. The regeneration of the cephalic neural crest, a problem revisited: the regenerating cells originate from the contralateral or from the anterior and posterior neural fold. Development 1996;122:3393–3407.

Couly G, Grapin-Botton A, Coltey P, Ruhin B, Le Douarin NM. Determination of the identity of the derivatives of the cephalic neural crest: incompatibility between Hox gene expression and lower jaw development. Development 1998;125:3445–3459.

Couly G, Creuzet S, Bennaceur S, Vincent C, Le Douarin NM. Interaction between Hox-negative cephalic neural crest cells and the foregut endoderm in patterning the facial skeleton in the vertebrate head. Development 2002;129:1061–1073.

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Creuzet S, Couly G, Vincent C, Le Douarin NM. Negative effect of Hox gene expression on the development of the neural crest-derived facial skeleton. Development 2002;129:4301–4013.

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Dulac C, Tropak MB, Cameron-Curry P, Rossier J, Marshak DR, Roder J, Le Douarin NM. Molecular characterization of the Schwann cell myelin protein, SMP: structural similarities within the immunoglobulin superfamily. Neuron 1992;8:323–334.

Dupin E, Baroffio A, Dulac C, Cameron-Curry P, Le Douarin N.M. Schwann cell differentiation in clonal culture of the neural crest as evidenced by the anti-Schwann cell myelin protein monoclonal antibody. Proc Natl Acad Sci USA 1990; 87:1119–1123.

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Dupin E, Real, C, Glavieux-Pardanaud C, Vaigot P, Le Douarin NM. Reversal of developmental restrictions in neural crest lienages: transition from Schwann cells to glial-melanocytic precursors in vitro. Proc Natl Acad Sci USA 2003; 100:5229–5233.

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Le Douarin N. Rôle du mésenchyme dans l’histogenèse hépatique chez l’embryon de Poulet. CR Acad Sci Paris 1963a;257:255–257.

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Le Douarin N. A biological cell labeling technique and its use in experimental embryology. Dev Biol 1973a;30:217–222.

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Le Douarin NM.The embryological origin of the endocrine cells associated with the digestive tract: experimental analysis based on the use of a stable cell marking technique. In Bloom SR ed. Gut Hormones. Edinburgh: Churchill Livingstone, 1978; 49–56.

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Le Douarin NM. On the origin of pancreatic endocrine cells. Minireview Cell 1988;53:169–171.

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Le Douarin N, Le Lièvre C. Démonstration de l’origine neurale des cellules à calcitonine du corps ultimobranchial chez l’embryon de Poulet. CR Acad Sci Paris 1970;270:2857–2860.

Le Douarin N, Le Lièvre C. Sur l’origine des cellules à calcitonine du corps ultimobranchial de l’embryon d’Oiseau. CR Ass Anat 1971;152:558–568.

Le Douarin N, Teillet, MA. The migration of neural crest cells to the wall of the digestive tract in avian embryo. J Embryol Exp Morphol 1973;30:31–48.

Le Douarin NM, Teillet MA. Experimental analysis of the migration and differentiation of neuroblasts of the autonomic nervous system and of neurectodermal mesenchymal derivatives, using a biological cell marking technique. Dev Biol 1974;41:162–184

Le Douarin NM, Kalcheim C. The neural crest. 2nd ed. Cambridge: Cambridge University Press, 1999.

Le Douarin NM, Halpern M. Origin and specification of the neural tube floor plate: insights from the chick and zebrafish. Curr Op Neurobiol 2000;10:23–30.

Le Douarin NM, Creuzet SE. Craniofacial patterning. In The skeletal system. Cold Spring Harbor Laboratory Press, 2009;53:117–147.

Le Douarin N, Le Lièvre C, Fontaine J. Recherches expérimentales sur l’origine embryologique du corps carotidien chez les Oiseaux. CR Acad Sci Paris 1972;275:583–586.

Le Douarin N, Fontaine J, Le Lièvre C. New studies on the neural crest origin of the avian ultimobranchial glandular cells. Interspecific combinations and cytochemical characterization of C cells based on the uptake of biogenic amine precursors. Histochemistry 1974;38:297–305.

Le Douarin NM, Renaud D, Teillet MA, Le Douarin GH. Cholinergic differentiation of presumptive adrenergic neuroblasts in interspecific chimeras after heterotopic transplantations. Proc Natl Acad Sci USA 1975;72:728–732.

Le Douarin NM, Teillet MA, Ziller C, Smith J. Adrenergic differentiation of cells of the cholinergic ciliary and Remak ganglia in avian embryo after in vivo transplantation. Proc Natl Acad Sci USA 1978,75:2030–2034.

Le Douarin NM, Corbel C, Martin C, Coltey M, Salaün J. Induction of tolerance by embryonic thymic epithelial grafts in birds and mammals. Cold Spring Harbor Symp Quant Biol 1989;54:777–787.

Le Douarin NM, Teillet MA, Catala M. Neurulation in amniote vertebrates: a novel view deduced from the use of quail-chick chimeras. Int J Dev Biol 1998;42: 909–916.

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Le Lièvre C, Le Douarin N. Origine ectodermique du derme de la face et du cou, montrée par des combinaisons interspécifiques chez l’embryon d’Oiseau. CR Acad Sci Paris 1974;278:517–520.

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¹Centre National de la Recherche Scientifique.

²At that time and up to the 1970s the grade of Docteur ès Sciences d’Etat was delivered upon defense of a main and a secondary thesis.

³I had an idea about that from the fate maps I had constructed for my thesis work where I destroyed transverse sections of the embryo through X-ray irradiations.

⁴This is true for birds at all developmental stages. In the mouse, the neural crest cells invading the gut give rise to a transient wave of adrenergic cell differentiation in the fetus. No adrenergic neurons, however, persist after birth.

Terje Lømo

BORN:

Ålesund, Norway

January 3, 1935

EDUCATION:

University of Bergen, Norway, M.D (1961)

University of Oslo, Norway, Ph.D. (Dr. Med.) (1969)

APPOINTMENTS:

Lecturer, Professor, Department of Neurophysiology, Institute of Basic Medical Science, University of Oslo (1968–2003)

HONORS AND AWARDS:

The Nansen Prize, The Norwegian Academy of Sciences (1980)

Member of The Norwegian Academy of Sciences (1986)

The Ipsen Prize (1992)

Anders Jahre Prize (2003)

Member of The Royal Norwegian Society of Sciences and Letters (2006)

Commander of The Order of St. Olav (2009)

Terje Lømo discovered long-term potentiation (LTP) and with Tim Bliss did the first systematic study of LTP. Lømo discovered that evoked muscle impulse activity per se controlled the properties of muscle fibers outside the neuromuscular junction and provided evidence against the idea of such control by “trophic factors.” He described the normal firing patterns of motor neurons by 24 h recordings of single motor unit activity from unrestrained rats and demonstrated the importance of such patterns in controlling the phenotype of muscle fibers with respect to both membrane and contractile properties. He introduced the concept of adaptive ranges, within which muscle fibers adjust their contractile properties to the impulse patterns and hence to the work imposed on them.

Terje Lømo

To be invited to write about yourself in a book like this must mean that you have had some success in life. In my case, this success, such as it is, has always amazed me. With no particular intention or ambition to do research, how did it come about that I have spent most of my life doing it? I read of others in these collections of autobiographies, about hardships, courage, narrow escapes under persecution in some cases, dedication to learning, and hard work followed by success. And I think of countless others, surely equally able and strong, who perish in periods of wars and civil breakdowns when their luck runs out and who leave no trace outside their nearest circle. There is nothing similar in my story. Growing up in occupied Norway during World War II, I was too young to be put to any test of hardship. I enjoyed an almost free ride at school and university, meeting a post-war world where jobs were abundant and Western societies were becoming ever more affluent.

It was thought in the family that I would study medicine and so I did. There was nothing else I particularly wanted to do. Medicine meant being able to postpone any real decision about my future since it opened doors to many types of workplaces, not only the clinic. I cannot remember that research entered my mind and, if it did, surely I must have concluded that I had neither the interest nor the ability. In fact, I barely got into medical school. In 1935, when I was born at the time of the Great Depression, there were exceptionally few births in Norway and the number of applicants to medical school 18 or so years later was correspondingly low. Consequently, I could enter with lower grades than ever before or since. In those days, it was mainly the sons and daughters of the bourgeoisie who entered University (my father was a dentist). In all, there were about 40 of us who finished gymnas (high school) in 1954. At that time, there was only one high school serving Ålesund, the town where I grew up, and the population on surrounding islands and along the fiords totaling perhaps 30,000–40,000 inhabitants. Today, the schools are many, the number of pupils many-fold higher with not all that many more inhabitants. Norwegian, mathematics, and physics were the main subjects for those wanting to study medicine, dentistry, or engineering. The grades in these subjects were weighted heavily and had to be good to obtain one of the 100 places at the medical school in Oslo, then the only one in the country. Many went abroad for their studies, mainly to Universities in Europe. For the United States, an affidavit, documenting local financial support in case of need, was required, making it difficult for many to go there. Entrance to law and liberal arts studies was not restricted. Biology and chemistry were minor subjects at high school. I cannot remember being much engaged by these subjects and certainly put little effort into them.

I remember being more interested in political subjects than anything that had to do with medicine or biology. At medical school I happened to come across the monthly periodical Encounter at the public library and found it of immediate interest. I soon became a loyal subscriber and remained so until it folded when the Soviet Union collapsed in 1990. To me, it represented an appealing corrective to much left-wing writing and politics of the day. I found Hans Eysenck’s Sense and Nonsense in Psychology, Use and Abuse of Psychology, and You and Your Neurosis very interesting. Neurosis, inferiority complexes, anxiety, feelings of insecurity, and the like preoccupied me. I felt I had more than my fair share of such attributes and was prone to contemplate my own navel to nobody’s pleasure. Throughout my life I have experienced at times long periods of very low spirits. I considered leaving science but held back knowing that would hardly solve the problem. In such periods I would withdraw. Exposure at meetings was often an ordeal. There were challenges and possibilities that I could not take on. Making a career did not seem important. I preferred the more lonely existence of being in the lab with my experiments. This explains, I think, my lack of ambition, the modesty that has been attributed to me in a Norwegian biographical lexicon. Perhaps this also explains why I have never looked for heroes or role models, but rather have maintained a skeptical awareness of human imperfections.

More rarely, I felt on top of the world. But most of the time, I guess, it was a matter of going about an ordinary daily life with trying not to make a fool of myself as my main driving force. Unexpectedly, however, the intermittent feelings of doom that often gripped me appear to have lifted in recent years, particularly after retirement, and to have been replaced by unaccustomed feelings of contentment.

Childhood

I grew up in Ålesund, a small town on three islands on the west coast of Norway, between fiords and steep mountains on the inside and a string of larger islands on the outside, protecting Ålesund from the Atlantic Ocean and its winter storms. The people living there are industrious and entrepreneurial, a gift from ancestors surviving under harsh conditions as small farmers and fishermen along the fiords and on the islands. Home industries took off early—boat building, the making of furniture and textiles. Today, Ålesund is home to a fleet of modern fishing boats and trawlers plowing the waters all over the world. Smaller and larger industries are scattered along the coastline, supplying offshore installations, building ships and advanced machineries, farming salmon, producing furniture for the often distant international markets, and yet highly competitive. For some time after the war the region also had a large textile industry until most of it went under as this industry went to places with cheaper labor, first in Southern Europe, then Asia.

During World War I, when Norway was neutral, my father moved to Ålesund from eastern Norway. His oldest brother had inherited the family farm, and the other children had to seek their fortunes elsewhere. Some in similar situations went to the United States A few went to St. Petersburg before the Russian Revolution made that option unattractive. For my father it happened to be Ålesund. My father always liked Ålesund. He found it less class ridden than where he came from, the wealth spread across many families, opportunities aplenty for the hard working, so he admired the people there. Growing up in Ålesund, the town seemed to me to be split into two types of people: on the one hand the religious, the puritans, and the teetotalers for whom dancing, drinking, and playing cards was considered sinful and, on the other, those who liked to do just those things. My family and my friends belonged to the second category. While many of my friends, and my oldest brother as well, knew from early on that they would return to Ålesund after studies and live there, I never felt quite at ease there. I felt constrained by the jargon, the customs, and the social pressures that came from belonging to a particular group. I wanted to start from scratch, on my own, freer, and without social bonds. So I left, never to return, except for brief visits, and without regrets then or later. Such sentiments, I think, have followed me since. Prone to feelings of awe toward people in command, I would tend to shy away from situations that I felt might require commitments and expression of loyalties that would undermine my sense of freedom.

Medical School

At medical school one of my teachers in anatomy was Alf Brodal, the author of Neurological Anatomy, a widely known book for many years and described by Todd Sacktor as his “bible” during preparations to become a neurologist. In one of his early lectures, Brodal invited some students to form a study group that would come to his office once a week for discussions about his research project at the time, the reticular formation of the brain stem. I joined that group and found it very much to my taste. We did not do any research ourselves but were introduced to relevant literature and offered his experimental material to look at. Brodal’s approach was to cut axons by making small lesions in the spinal cord (and elsewhere in the central nervous system) and then determine their cells of origin by identifying swollen cell bodies undergoing retrograde chromatolysis (tigrolysis) in sections of the brain stem. Using young kittens (his modified Van Guddens technique), such cells would stand out clearly from intact neurons in the region. To be able to trace pathways in the brain in this rather precise way appealed to me as did reading about and discussing their possible functional implications. At the end of this exercise, I presented the group’s experiences to the rest of the class to Brodal’s satisfaction, according to his concluding remarks. And that apparently was the end of it. As it turned out, however, it probably had a decisive influence on my later choice of what to do in life. It was also, I think, a fine and relatively rare example for its time of a professor making a strong effort to introduce and recruit young students to research.

Early Days in Pisa

In 1958, in the midst of clinical studies, I felt I needed a break. I contacted Brodal and told him that I would like to go abroad perhaps to do research. Did he have any suggestions? He suggested Pisa, wrote to Professor Guiseppe Moruzzi, the head of the “Istituto di Fisiologia” at the University of Pisa, who immediately agreed. So with a fellowship from the Italian State, I left Oslo by train one Wednesday evening in August 1958 and arrived in Pisa on Friday afternoon nearly 2 days later. My father enthusiastically supported this study abroad as he had earlier, in 1951–1952, supported my spending a year in a high school in Fort Wayne, Indiana, with a scholarship from the American Field Service, and even before that when I bicycled with a friend over much of England at the age of 14.

Arriving in Pisa I was met at the station by Arnaldo Arduini. He took me to a nice hotel along the river Arno, where the institute had booked a room for me, and asked me to come to the institute on Monday morning, which suited me fine. The room turned out to be on the top floor, where I quickly stepped into the bathtub to take a shower, looking more like a chimney sweeper after 2 days on the train and hours of leaning out of the train to take in the Italian scenery. Then with black foams of soap all over my body, the water disappeared and did not come back that day. Although trivial, it left an impression on me. I can still see the layout of the room, the bathtub, and myself scraping off the foam before I went out to have my first Italian meal in a nearby trattoria with wine and fresh fruit for dessert, feeling free and great, but also wondering what the next year would bring.

On Monday, I was shown a little corner room on the second floor, which was to be my home for the next year. To reach it I had to pass through a student laboratory, where I later assisted Amilcare Mollica in demonstrating the vagus effect on the heart of anesthetized rabbits for the medical students. Moruzzi was in Moscow, I seem to remember, at an international conference on brain research, particularly sleep, that attracted many high-profile scientists in the field from Europe and the United States. When he returned, he arranged for me to work with Mollica, who had a large laboratory with high windows facing Via S. Zeno and a large Faraday cage in the middle. In a similar, neighboring room worked, among others, Ronald Melzack, who with Patrick Wall, would later publish the classic Gate Control Theory of pain. At the time, the Institute in Pisa was an international centre for brain research, attracting researchers from across the world, and over it all presided Moruzzi, Il Professore, in somewhat splendid isolation it seemed to me. The language in the institute was English, and partly for that reason I was very slow in learning Italian, even though friends among the local students helped me along. But I have always regretted that I never learned to speak Italian well.

Pisa and Oslo collaborated at the time. Gian Franco Rossi and Ottavio Pompeiano, who would later replace Moruzzi as head of the Institute, both spent a year or more in Brodal’s lab in Oslo, which explains, I think, why I was so readily and so well accepted in Pisa. But I remember Mollica’s surprise when he realized that I was only a medical student with no experience doing research.

Research in Pisa

Moruzzi wanted Mollica to study sleep. I remember Moruzzi telling us about a presentation at the meeting in Moscow, claiming that it was possible to induce sleep in humans by letting them rest in a bed that was rocked back and forth at a certain frequency. So he suggested we do something similar with rabbits. We had a cage made that swung to and fro while suspended from the ceiling of the Faraday room and placed a rabbit inside with screws in the skull for electroencephalogram (EEG) recordings. The problem was that we could never make these rabbits sleep. The EEG was more or less continuously desynchronized and if hopeful signs of synchronization should appear, sudden loud noises from Via S. Zeno would put an end to that, as when the local rag-and-bone man made his rounds shouting out his goods.

We gave up the project, which Mollica from the beginning did not believe in anyway, and went on to a more conventional approach to sleep research based on the encephale isolé preparation. Mollica did not believe in this approach either and was happy to leave the surgery to me, first on rabbits and, when that turned out difficult, on cats, the more common preparation. I don’t remember the purpose of the effort and before long this project also was abandoned. Occasionally, Moruzzi would come into our lab to ask how we were doing. As progress was zero, also eventually he gave up making suggestions and left Mollica to his own devices. We then began recording from single units in the cortex of awake rabbits, using electrolytically sharpened, insulated tungsten electrodes, the technique for which David Hubel had published a little earlier in Science. I don’t remember Moruzzi taking any interest in this project but, when we told him about it, he suggested that I go to Rome at the Institute’s expense to see G. M. Ricci, who had recently returned from Herbert Jasper’s lab in Montreal and was setting up his own lab to do similar single-unit recordings. I was well received by Ricci, saw Rome for the first time, and enjoyed a marvelous couple of days there.

But well before this, when Mollica and I were at our most frustated, Ron Melzack, perhaps concerned that I was having a difficult time, suggested that I could join his group. In this group there were also C. J. Smith, F. Magni, and sometimes Moruzzi would come down from his office on the third floor to participate in the experiments. However, Mollica and I got along very well together and I was happy to work with him. It is true, that at times of frustation, we would distract ourselves by shooting down flies from the high ceiling by squirting ether on them from syringes. With every hit, the fly would drop to the floor and then quickly recover from the anesthesia, which allowed the game to continue. It is also true that Mollica was extremely upset after every visit by Moruzzi, not because Moruzzi, as far as I could see or now remember, was unkind or unreasonable, but rather because hierarchic traditions and Mollica’s character were such that, when facing Moruzzi and even strongly disagreeing with Moruzzi’s proposals, he was unable to express his own. Perhaps Mollica took as orders what Moruzzi meant as suggestions and generally answered Moruzzi with “Si Professore” in his presence, while resorting to fits of temper as soon as Moruzzi left the room.

By New Year 1959 Mollica and I were on our own. We designed a microdrive and asked a machine shop in Piacenza to make it. The shop, which specialized in high-precision tools, belonged to the father of an engineering student in Pisa who had become a close friend of mine. We attached the drive to the skulls of rabbits under anesthesia and later recorded from single units in the visual cortex with the rabbit loosely attached with a strap to a wooden cage open at both ends, head and chest sticking out at one end, tail at the other. I made the electrodes according to Hubel’s description, realizing soon that this was not always straightforward. Despite efforts to standardize the procedure, particularly the coating of the electrodes with insulating material, the electrodes varied enormously in quality and most of them had to be discarded. Nevertheless, over the ensuing month we were able to record many units with high signal-to-noise ratios over periods of up to several hours. We exposed rabbits to light, sound, odors, pinpricks, and squeezes of the tail, described the firing patterns of responding neurons and the modulatory effects of different sensory inpurts, as wells as effects of barbiturates and local applications of strychnine to the cortical surface.

I was probably the last person to collaborate with Mollica, and our paper together was probably his last. Later, I heard that Mollica had had a serious mental breakdown and that he never returned to science. I found this very sad. Our relation and collaboration had been very good. Mollica was interested in many things, which we frequently discussed. He had top grades from medical school. I found him very clever, even brilliant, in many ways. But, as far as I could tell, he had little or no social life outside work. He lived alone with his mother. After work he would take his bicycle and apparently go straight home. Outside work, we never met and I never saw him with others. When difficulties arose and he stopped working, I believe that Moruzzi tried to help him. It is one of my many regrets in life that after I returned to Norway and the correspondence relating to the paper came to an end, I failed to keep in touch with him.

In June or July, I returned to Norway. Mollica had started writing the paper, which appeared in 1962 in Archives Italiennes De Biologie. There, we acknowledge that the research was carried out with funds from the U.S. Air Force and the Rockefeller Foundation. This was a time when the United States was still very active in rebuilding and supporting Europe after the war with direct donations in the best traditions of American philanthropy.

I now see what I had forgotten, that the paper was translated into English by T. D. M. Roberts and J. D. Christie. Roberts visited Pisa when I was there. We went out together with my Italian friend who spoke no English. Roberts was walking with notebook and pencil in hand asking for the Italian names of just about everything that caught his eye. I was impressed and I remember well wanting to take up that behavior myself, but it never came to that then or later. I may well have seen the paper before it was submitted for publication, but I cannot remember that I took any direct part in writing it. Perhaps it wasn’t even considered that I might be of use, being a student with no previous research experience and without English as my native language. As it was, it suited me fine. I was busy taking up my medical studies again and would have found it very difficult to enter into the mindset and vocabulary needed to describe and discuss such complex issues.

I don’t know that our paper has ever been referred to. It is not listed under PubMed. Although these were early days for recording from single cortical neurons in awake animals, the paper was anecdotal rather than systematic, descriptive rather than mechanistic, and rather deficient in revealing new and interesting phenomena or principles. But then it becomes another example of the ease with which one can spend much time and effort on research and obtain results that then disappear without leaving a trace except in CVs for job applications. And yet, the year in Pisa was not only personally unusually enjoyable, satisfying, and educational but also decisive for my later choice in life (more later).

Memories from Pisa

I had a good year in Pisa. I was on my own and was never homesick. I liked living in the institute and having my own private room there. Seeing it again last summer for the first time in more than 50 years filled with outdated instruments and computer ware, I was amazed at how small it was, room for a bed, a wash basin, and a writing desk in front of the window and little more. But I don’t remember having any problems with that. Coming from the north to the sunny Mediterranean of my imagination I had not expected some of the winter days to be so cold but with an electric stove installed, my room was fine. In the mornings I went straight to lab without breakfast of any kind, which was contrary to everything that had been drilled into me for as long as I could remember, namely the absolute necessity of a regular, substantial, and healthy breakfast. But again, no adverse effects came to pass, only a healthy appetite building up before lunch. My stipend and supplements from my father allowed me to buy a wonderful new Vespa, travel, eat and drink well, and see Toscana, the nearby mountains, and the sea. I enjoyed the library in the Institute but found Eccles’ The Physiology of the Nerve Cell rather difficult. Every midday I would walk across Piazza dei Cavalieri and Piazza dei Miracoli to a little bar just outside the old city wall where, in a little room behind the darkness of the bar, the wife of the bar owner served a delicious, simple, low-cost lunch for a few regular customers, including myself and one or two friends among the students. This became such a routine that at one point I told my surprised friend that I needed a break and wanted to walk around on my own. Before long, however, I fell back into the routine. After Norway, where I was used to partying, drinking, dancing, and the rest from the time of my confirmation, Pisa at the time appeared very provincial. Everybody, it seemed would dress up and walk up and down the streets before disappearing behind gates and shutters for dinner, leaving a good number of male students to wander aimlessly around. From what I understood, the church controlled the choice of films shown by most of the cinemas, so that was not much fun either.

In my experience there was little social interaction between the people working in the institute, no common room where one could go for a cup of coffee or tea, or to talk about science, ongoing work, or whatever, no seminars that I can remember. Had I known better, I think I would have missed it. But I may also have missed much of what was going on in the institute since outside working hours I was away most of the time. By some happy coincidence I had met an Italian engineering student as I stepped out of the train that brought me to Pisa. He became an almost daily companion during my year in Pisa and a life-long friend. He introduced me to many of his friends and made my days in Pisa anything but lonely.

Of many memorable experiences in Pisa, one in particular made an impression on me. One day I heard loud noises from the lab next door, went in, and saw a cat on the loose knocking down bottles and making a great confusion. I tried to grab it, but it turned around in its loose skin, biting and scratching my hand. This caused some concern and I was sent to the hospital with a prescription for immunization against rabies. There the doctors filled a large syringe with an opaque, withish fluid that they injected under the skin of my belly. I did not like the sight of the fluid and when they told me to come back for an astonishing number of additional injections, I started thinking about risks, about the likelihoods of rabies in the cat, and immune reactions in my brain in particular. No more injections for me, I quickly concluded, and went back to observe the cat, which in the meantime had been caught and brought back to the stabulario in the garden. When it saw me, it snarled at me in great anger but when it continued to do so on subsequent inspections without any signs of disease, I dropped the matter without at any time having felt really worried. This may have been the first time that I became concious of an enduring scepticism of doctors for their readiness to overtreat and, in the process, underappreciate risks, side effects, and complexities. Sometimes it is better not to treat and give the body time to heal itself.

Return to Oslo and Medical Studies

I returned to Norway in July 1959. Soon afterward, I was invited to present the work from Pisa at a meeting of the Neurological Society in Oslo. There I met Per Andersen for the first time and on his suggestion presented the work again at the Scandinavian Physiological Congress in Oslo in 1960. The session was chaired by Ragnar Granit, who made some comments I did not understand. I don’t remember my answer, but I remember talking to others afterward who also had not understood what Granit had been talking about. By then I had moved to Bergen to finish the final 2 clinical years of medical school.

Life as a Doctor in Northern Norway

After graduation, I was doctor in a hospital for 1 year and assistant community doctor for another half year. Such practice was required in Norway, and it still is to obtain a medical licence. I went to the hospital in Tromsø and then to the community of Skjærvøy, a small island north of Tromsø with about 1400 inhabitants. There was only one car on the island, no bridge to the mainland, but northbound and southbound coastal steamers that stopped over once a day. I often visited patients at home, by foot on the island or by boat to nearby islands or the mainland, trips that could take many hours. The boat Medicus owned by the community, was slow, had a crew of two who made delightful company, and whose job it was to take the doctor around and transport patients. Contact could be made by radio, but it was seldom used. Thus, weather permitting, the boat calls often became restful outings, sometimes in the company of my wife, Anne, in spectacular landscapes as the season changed from no sun in the winter for 2–3 months to sun all day and night in the summer.

For many, life was hard in a harsh climate, the men away as fishermen or sailors, the women at home often in isolated places looking after children, a cow or two, or some sheep. Pain from muscles and joints, usually in the back or neck was a common complaint, and I soon adopted my own procedure for dealing with it. There were four main components. Application of an ointment over sore muscles, resulting in a local flush and feeling of warmth; injections of dilute solutions of a local anaesthetic into sore spots; aspirin; and a belladonna derivative, a relaxant before the time of valium and similar drugs. I would use them in this order depending on the condition and its resistance to treatment, only for restricted periods of time with counterindications in mind, aiming to break a vicious circle, always with instructions to the patients to make sure they had a good bed or mattress and, if possible, to take time off during the day in which to concentrate on relaxing, massage the ointment into sore regions, or better have a partner to do that, then inform me of any progress after a week and, if disappointing, to come back for further treatment. I believed in the approach, was enthusiastic, and as a result the patient probably benefited from a strong measure of placebo effect together with any specific effects there might have been from breaking a vicious circle and adopting a lifestyle that stressed the muscles less. Anyway, I had the impression that sometimes the treatment was helpful. As an indication of that, at the end of my time at Skjærvøy, a woman travelled the considerable distance from Tromsø to see me because she had heard that I was good at treating backaches.

I remember one patient in particular, a young woman complaining of chronic headache. The muscles at the back of her head were sore on palpation for which I found no reason and therefore started treating as described. She came back after a few days not seeing well. The belladonna, a muscarinic antagonist, had blocked accomodation in her eyes, revealing a hyperopia that eyeglasses immediately corrected. She did not come back, in all likelihood because her problem had been solved. This event had some lessons for me. Had I continued being a doctor, I would never again have treated headaches without checking eyesight. It demonstrated how chronic tension in some muscles, in this case in the eye, could somehow cause chronic tension and pain in other muscles, in this case the neck. Assuming that the eyeglasses resolved the headache, it also demonstrated how effective breaking a vicious circle can be.

I liked being a doctor. Initially, it was hard due to inexperience, unnessarily long hours because I was slow, responsibilities beyond my competence, and, I think, an inborn feeling of insecurity. But before the end of my time at Skjærvøy, and faster than I had feared, I had acquired a certain assurance based on a conviction, drilled into us at medical school, that it was essential to be systematic in taking the history of the patient and in the subsequent physical examination, so as not to overlook anything. On many occasions, surprise findings made it clear to me that being systematic was important even when it might seem to be a waste of time. Moreover, it was essential when things did not turn out well or as expected. One had done one’s best and mistakes, when they occurred, at least were not due to negligence. With hindsight, I think this was the only way I could deal with the anxieties and feelings of guilt that could otherwise so easily come with being a doctor. I see my background in medicine and medical practice, however short, as important for my subsequent career in science. The search for a diagnosis in medicine and a resolution to a problem in science have similarties, among them the lack of a priori answers. Perhaps it has helped me to better see the organism as a whole with many interacting parts at the level not only of cells and molecules but of organs and to see functional significance in new observations made in the laboratory.

Apprenticeship with Per Andersen

After Skjærvøy, I returned to Bergen to complete my military service in the Norwegian Navy. I had already done 5 months of service during summer holidays as a student. There remained 13 months as a Navy doctor, partly on land at the NATO naval headquarter outside Bergen and partly on board one of the Norwegian frigates. A few years earlier, I had served as an attendant to the officers on board another frigate on a training expedition for Norwegian naval cadets that took us to O’Porto in Portugal and Jan Mayen in the Arctic Ocean with many calls at ports in between. Some impressions remain: the extreme tiredness from late nights in ports, crowdedness and irregular hours of duty on board, rough weather, and sea sickness at sea. Around Jan Mayen there were several large Soviet factory and storage ships serving numerous trawlers inside and outside Norwegian territorial waters, at that time positioned 3 or 4 nautical miles from the shore. As our frigate moved very slowly along this border, the fishing boats pulled up their gear and moved out of Norwegian waters only to move in again as soon as we had passed. But Norway had shown its flag and Norwegian jurisdiction over Jan Mayen and its surrounding waters had been respected, and that was, surely, the purpose of the visit. But this was in a time of peace. I can only imagine the conditions on board such ships in times of war.

Before discharging from the Navy in July 1964, I asked for a leave of absence for a few days, went to Oslo, and looked for a job that combined research and clinical medicine. Neurology had no appeal, too little to offer in terms of treatment. Neurophysiology, as I knew it, was too far removed from the clinic. I had visited one hospital and was on my way to another when I accidentally met Per Andersen in the street. He had done highly successful postdoctoral work with John Eccles in Canberra, Australia, was back to set up his own lab, and was looking for people to join him. He remembered me from 4 years earlier and promptly said we needed to talk, the result of which was that I joined Per in August 1964 with a fellowship from the Norwegian Research Council that Per and Alf Brodal helped me to obtain. I had a letter of recommendation from Moruzzi saying that he was “quite pleased” with my stay in Pisa, but I did not I use it, thinking that it meant fairly or not so pleased, according to English usage. Now I learn that “quite” according to American usage might be an intensifier, an interesting ambiguity in the meaning of words. I still think Morzzi used it in the English sense, and rightly so, since what I did in Pisa was quite ordinary.

I assisted Per with his experiments until Christmas 1965, usually twice a week and, as was common among serious neurophysiologists at the time, often long into the night. We focused on CA1 in the hippocampus of rabbits and cats, the identity and location of excitatory synapses on dendrites in collaboration with Theodor Blackstad and dendritic conduction. Soon I was setting up the preparation and moving the electrodes while Per controlled the instruments. Upon penetrating a cell, the loud noise from the loudspeaker made Per jump to life and in the fleeting moments before we lost the cell, he would play the instruments like a virtuoso and obtain incredible amounts of information. With Sven Andersson, visting from Gothenburg, Sweden, I also participated in the experiments on thalamo-cortical interactions that led to the book by Per and Sven: The Physiological Basis of the Alpha Rhythm. Early on I learned the Golgi technique from Blackstad and, in one of the sections, I could see one neuron, and only one, a CA1 pyramidal cell, standing out pitch-black apparently in its entirety. This cell and influential ideas by Wilfred Rall on the electrophysiology of dendrites inspired Per to suggest the following project: model the stained neuron in copper, run hot water over the cell body, and measure temperature gradients along the cell’s branches as simulation of passive current flow. Bill Letbetter, a postdoctoral students in Per’s lab, made the model in our workshop with help from specialized tool shops in downtown Oslo. The cell body and dendrites were in solid copper, extending more than 1 m with relative dimensions similar to the stained cell and with strips of copper clamped to the dendrites to simulate spines in a completely unrealistic manner. Letbetter, another student in Per’s lab, and I did the experiments, placed the model horizontally on a bench, attached homemade thermocouples at different positions along the cell, opened a valve from a large container with 60 liters of boiling water on a high shelf above to let the water flow rapidly over the cell body and into a reservoir on the floor through custom-made tubes and a tightly sealed plastic housing around the cell body. With a new multichannel HP A-D converter we obtained beautiful curves of temperature changes along the dendrites. As expected, the temperature rose progressively more slowly with distance from the cell body. But that was the end of it, presumably because we did not quite know what to do with the data we had collected. Unfortunately, all records from this rather heroic or reckless experiment from an earlier era, considering all the boiling water above our heads, have disappeared.

On other occasions, I went into the garden around the University buildings in Oslo’s center to collect hedgehogs, which were then placed in the refrigiator for hibernation. The idea was to remove the hippocampus in toto under cold conditions, hoping that it would survive and allow in vitro experiments, but it did not work. The few hedgehogs we found did not properly hibernate and it was not easy, I remember, to remove the spines and anesthetize them.

At the end of 1965 it was time to start my own Ph.D. project. In agreement with Per I began studying frequency potentiation in the dentate area. Per had earlier reported this phenomenon, which refers to the dramatic increase in firing of pyramidal or dentate granule cells caused by repetitive stimulation of their afferent fibers, usually at frequencies around 10–20 Hz. It was expected that work for the Ph.D. should be independent. Therefore, I used the lab on days when Per had other things to do, and did all the experiments, subsequent analysis, and writing myself. Under Per’s guidance I had participated in all aspects of this type of research, from the idea to the finished paper, except the writing. This was essential background. But now I wanted to be on my own, choose my own directions, and prove, above all to myself, that I could be independent. I am grateful to Per, and the tradition of that time, for the opportunity to do so.

The Discovery of Long-Term Potentiation

Initially, the focus was on what happened during repetitive stimulation. I cannot remember that Per and I ever discussed that looking for the after-effects of such stimulation should be a specific part of my project. That just happened as I did the experiments. I then saw the dramatic build-up in granule cell population responses with repeated trains of stimuli, a build-up which then could last for hours. It must have been a natural thing to look for. I was then reading papers by Eccles and coworkers on the cerebellum and was impressed by how they used the paired-pulse paradigm to demonstrate excitability changes and the spread of such changes at different times after the first pulse. All I needed to do was to replace the single pulse with a train of pulses. Furthermore, others had already looked for such aftereffects and not found them, and I wanted to have my own look. I reported the new phenomenon at a meeting of the Scandinavian Physiological Society in Åbo (now Turku), Finland in August 1966, and in an abstract from that meeting in Acta Physiologica Scandinavica.

I remember showing the result to Per and how impressed we both were by the magnitude and the duration of the effect. But I am sure we had no idea then that this would be the beginning of the LTP story as it is known today. Rather, I think it is fair to say, we saw it as one of many other exciting phenomena brought to light by the brain studies of the day. Nevertheles, in seminars that I gave at the time, my records show that I used expressions such as “The effect is long-lasting, shows no tendency to fade after periods of rest up to 22 min in this experiment. In other experiments increased efficiency is seen for hours,” “If it is correct that the hippocampus is involved in memory function, this is a region where one should expect long lasting changes to occur,” and “The phenomenon may represent a kind of bahnung [opening] of individual synapses and may have relevance to theories of learning.”

Trying to Understand the Dentate Gyrus

I had many records and plots related to frequency potentiation and its after-effects lying around at the time but, except for the abstract in Acta Physiologica Scandinavica, I never published any of them, nor did I on my own follow up or publish anything on what was later to be known as LTP. I remember sitting there by myself in the lab, often late at night, being overwhelmed by the complexity of the field potential changes unfolding before my eyes on the ocilloscope screen. I obviously needed to know much more about the basic properties of the structure I was studying. I therefore changed direction. Along the lines pioneered by Eccles and coworkers in the cerebellum, I began using field potential analysis to explore the distributions of responses to orthodromic perforant path stimulation and antidromic mossy fiber stimulation and obtained evidence for a lamellar organization of both the input to and the output from dentate granule cells. Using the paired pulse paradigm I demonstrated marked potentiation of intra- and extracellularly recorded excitatory postsynaptic potential (EPSPs) at the perforant path-granule cell synapse. The potentiation occurred independently of any detectable granule cell firing, which required substantial EPSP summation. When the intensity of the conditioning stimulus was increased to discharge granule cells, profound postfiring inhibition occurred, lasting up to 100 ms and spreading several mm along the longitudinal, septal-temporal axis of the dentate gyrus to granule cells that had not been activated by the conditioning stimulus. When granule cells were discharged antidromically by stimulating mossy fibers in CA3, granule cells were profoundly inhibited along a similar time course and with a similar longitudinal spread, which I took as evidence that the inhibition was mainly recurrent. This work then made up my thesis, which did not include frequency potentiation or LTP. I defended my thesis in Ocober 1969. The first opponent was Anders Lundberg, professor of Neurophysiology in Gothenburgh, Sweden. He made some critical remarks with which I agreed and, as I remember it, I then went on to mention other aspects of the work with which I was unhappy. To the amusement of the audience, we then entered into a discussion where he would defend and I would criticize the thesis.

The work consisted of four single-author papers, which I submitted to Experimental Brain Research at the end of 1969. The papers were returned with both favorable comments and critical remarks calling for changes. I made the necessary changes for two of the papers, which were published in 1971. The other two remained in my files for nearly 40 years until I merged them into one paper using the same original figures but an updated text and had it published in Hippocampus in 2009. But before then I received a letter dated March 31, 1970, from Eccles, the editor of Experimental Brain Research and one of the reviewers of the four papers saying: “I have been wondering for some time about your hippocampal papers. I am sorry that you have not made some of the suggested alterations and sent them in to me because they would certainly have been accepted for publication. Perhaps though it is better that you think some more about them. Please do appreciate that the referee and I both think very highly of the papers so you should not be depressed about them.”

Enter Tim Bliss

While I was busy in Oslo, Tim Bliss was doing a Ph.D. on synaptic plasticity in the neocortex at McGill University, Montreal, with Ben Delisle Burns as his supervisor. When Burns became Head of the Division at the National Institute for Medical Research, Mill Hill, United Kingdom, in 1966, Tim followed him a year later and has been there ever since. From the beginning of his research career, his interest had been in possible neural mechanisms underlying learning and memory. But work on the neocortex appeared difficult and unrewarding. In Tim’s own words: “However, the main conclusion I reached after devoting nearly 3 years to this approach [undercut slabs of neocortical tissue developed by Burns] was that it was misguided. The preparation was too complex. It was essential to simplify.” Tim then happened to read a paper by Per on the hippocampus describing its relatively simple structure, with the cell bodies condensed in a single layer and afferent fibers from different sources terminating on different discrete regions along the dendrites. This structure appeared much more suitable, particularly for field potential studies, and when Per made a visit to London in 1968, Tim contacted him and asked him about the possibility of spending a year in his lab to learn the hippocampus and field potential analysis. On hearing of Tim’s interest in memory mechanisms, Per, according to Tim, then said: “You must come and talk to Terje Lømo who has found something that will interest you.”

Tim visited Oslo briefly and, as he remembers it, we agreed to carry on with the LTP experiments but, since I had to finish my Ph.D., I would not be able to spare more than 1 day a week. Then, in August 1968, Tim came to Oslo for a year. With Per and Knut Skrede he did experiments that led to papers on the “Lamellar Organization of Hippocampal Excitatory Pathways” and “Unit Analysis of Hippocampal Population Spikes,” both published in 1971 in Experimental Brain Research. They confirmed the lamellar organization that I had shown in my thesis work for the perforant path input and the mossy fiber output of the dentate gyrus (published in 1971 and 2009, respectively), expanded it, and went on to demonstrate a similar organization for the CA3 input by Schaffer collaterals to CA1. Thus, they showed that it should be possible to preserve the entire trisynaptic circuit from the entorhinal cortex (perforant path fibers) to CA3 (mossy fibers), and thence to CA1 (Schaffer collaterals) in a narrow, nearly transverse segment of the hippocampus, an essential requirement for the success of the transverse hippocampal slice maintained in vitro that was to come later.

Bliss and Lømo (1968–1969): The Start of Long-Term Potentiation Research

When Tim came to Oslo in 1968, a new lab had been set up across the corridor from Per’s lab. About once a week, Tim joined me there to follow up my preliminary results on LTP 2 years earlier. Usually, the experiments went on until late at night or into the morning, either because we were busy with other projects and therefore started late or because some of the experiments lasted that long. We both remember our tremendous excitement when, in the very first experiment, the granule cell population spike increased dramatically and progressively after each stimulus train in the experimental pathway, while the control pathway on the other side was unaffected. And, into the next morning, our excitement was no less when we found similar long-lasting effects after briefly tetanizing what had been the control pathway. Our minds were prepared and, when further experiments showed that the results were reproducible, we were well aware of their significance.

With the setup just described, we used the same stimulation electrode to tetanize (condition) the pathway and to monitor the aftereffects with single test stimuli. We therefore worried, and Tim may have been the first to express this concern, that changes at the site of stimulation might lead to activation of more perforant fibers after the tetanization. If so, the posttetanic increase in the population spike might be an artifact. In my own studies, I had observed that the perforant path fibers run as through a bottleneck in the angular bundle before they fan out to excite the dentate gyrus along narrow, nearly transverse strips of tissue along its entire dorsal extent. We therefore changed our approach and for all the reminaing experiments placed the conditioning, tetanizing electrode up front to stimulate only a narrow strip of granule cells in what we called the experimental pathway and the test electrode some distance away in the bottleneck of the angular bundle to stimulate together perforant path fibers both in the experimental pathway and in a more lateral control pathway not receiving tetanization. Obtaining comparable LTP with this approach, we became convinced that the phenomenon was genuine. There was now no longer any reason to think that the test stimulus had activated more axons in the experimental pathway than in the control pathway.

We also routinely measured not only the size of the population spike but also its latency, and most important, the population EPSP in the molecular layer. We knew that this was monosynaptic and by measuring its rate of rise and amplitude no more than 1 ms after its onset we could be reasonably sure that it reflected the synaptic current evoked by the perforant path volley uncontaminated by other activity. In this way we convinced ourselves that the observed potentiation was real and occurred at the synapses that perforant path fibers make with the dendrites of the granule cells. Nevertheless, there was much variability in the result, as described in Bliss and Lømo (1973), from one stimulus to the next and from one animal to the next in the size and duration of the potentiation. Interestingly, the varibility from one stimulus to the next was much reduced after induction of LTP. In some animals, the spike latency was shorter than accounted for by EPSP potentiation, and in some cases spike potentiation could occur without EPSP potentiation (this uncoupling of spike and EPSP potentiaton was later termed EPSP-to-spike potentiation or E-S potentiation). Why we had such variability, we did not know (but see the next section).

The Paper (Bliss and Lømo, 1973)

We did our last experiments in the summer of 1969 and submitted the paper based on them early in 1973. There were several reasons for this delay. I was finishing my thesis and preparing to defend it in October 1969. Tim was busy finishing other work in Per’s lab. Soon after my thesis we both left Oslo for London. Tim returned to Mill Hill. I went with a fellowship from the Wellcome Trust to work for 1½ years on the nerve-muscle preparation at the Department of Biophysics, University College London after a letter from Per to Ricardo Miledi had elicited an invitation to work with him. There were still experimental records in Oslo waiting to be analyzed. Things moved less fast in those days, there was no immediate interest in our results (see later), and neither Tim nor I could have felt any urgency for a rapid communication. Moreover, both Tim and I tended never to be fully satisfied with our drafts and would go on and on, intermittently, trying to make improvements. Until one day, according to Tim, Tony Gardner-Medwin took matters in his own hands. Tim and Tony had earlier completed a study in Tony’s lab in the Department of Physiology, University College London, similar to ours but on unanesthetized rabbits. In exasperation at our procrastinations, Tony finally and in a short time came up with a nearly submission-ready paper describing their work. This must have pushed Tim and me to a final spurt of energy, and both papers were submitted together to the Journal of Physiology. Two or three weeks later, and I cite Tim: “Bliss was startled to be informed by the Journal of Physiology referee, Bernard Ginsborg, who had taken the unusual step of telephoning him from Edinburgh to discuss ‘this interesting work,’ that while the second manuscript was fine as it stood, the first, Bliss and Lømo, showed signs of having been hurriedly written.”

Bliss and Lømo (1973) was reprinted in the Journal of NIH Research in 1995 as a landmark paper. There, Roger Nicoll writes: “So, the question is, Why did this paper start this dramatic field? First of all, it describes all of the basic phenomena of the process of long-term potentiation. These include pathway specificity, saturation, and an increase in the coupling of the synaptic potential to the discharge of the granule cells. Second, there’s not a single controversial result in that paper—a very remarkable thing in this field.” Pathway specificity was not directly demonstrated in our work in the sense that synapses belonging to inactive inputs to the same target cells were shown to be unaffected. That demonstration would come later in slices. But we had indirect evidence, which Tim, Tony, and I published in a book article in 1973. We plotted stimulus response curves before and after tetanization and showed that there was an increased slope after the induction of LTP, but only for stimuli with an intensity equal to or less than the intensity used for the tetanization. After that, the curves were parallel. This, we argued, implied input specificity because at higher intensities nontetanized axons were being recruited, and these, as indicated by the parallel curves, had not been potentiated.

The Reception

In 1969, at a NATO-sponsored summer school in Varenna, Italy, we presented our work as students to many of the top names in neuroscience at that time without causing any obvious excitement. As late as 1981, LTP was not mentioned in the textbook Principles of Neuroscience by Kandel and Schwartz or in Alf Brodal’s Neurological Anatomy despite Brodal’s extensive treatment of the hippocampus in his book. Interest in LTP began in earnest in the first half of the 1980s when G. L. Collinridge, P. Ascher,

G. Lynch, and others discovered that LTP in CA1 requires both activation of postsynaptic NMDA receptors by glutamate and sufficient postsynaptic depolarization to remove the Mg²⁺ block of NMDA receptors, and that postsynaptic injection of calcium chelators blocks the induction of LTP (see Bliss and Collinridge, Nature, 1993, review).

A few scientists did show an early interest in our work. John Eccles, visiting Per’s lab at the end of 1968, was very excited. He had looked unsuccessfully for such plasticity in the spinal cord and in his book The Physiology of Synapses (1964), he writes: “Perhaps the most unsatisfactory feature of the attempt to explain the phenomenon of learning and conditioning by the demonstrated changes in synaptic efficacy is that long periods of excess use or disuse are required in order to produce detectable synaptic changes.” Our results were just what he had been looking for but in the wrong system. He incorporated the results into his own thinking about the brain and presented some of our results and figures as unpublished results in books that he wrote at the time, one of them with Karl Popper, The Self and Its Brain (Springer International, 1977). Other persons showing an early interest were Gary Lynch, Graham Goddard, and Bruce McNaugthon. I first met Bruce, then a Ph.D. student with Graham Goddard, at a summer school in 1973 in Erice, Sicily, where Bernard Katz had set up the scientific program. I remember Bruce at lunch, after a lecture I had given, asking many questions and wanting to discuss the implications of our findings.

Thoughts on the Function of the Hippocampus as Perceived in the 1960s

At times during my Ph.D. work people would ask, Why do you work on the hippocampus? What does it do? and I was embarrassingly short of answers. I knew that its main output, the fimbria, projected to the hypothalamus, so I said it probably participated in the control of the endocrine and autonomic systems. The older idea that it served olfaction, reflected in the term rhinencephalon, was out, as convincingly argued by Brodal in his book Neurological Anatomy. Citations from the latest edition of that book in 1981, pages 683–685, illustrate the dearth of knowledge: “The anatomical complexity of the hippocampal formation makes it clear that it will be difficult—and perhaps impossible—ever to define satisfactorily the ‘function’ of the hippocampus or any other part of the hippocampal formation. One type of theory suggests that a major function of the hippocampus is to modulate motor control systems directly. The second type of theory suggests that the major function of the hippocampus concerns some non-motor behavioral or psychological process (Black, 1975). Some authors have concluded that a main function of the hippocampus is to exert a nonspecific inhibition of emotional reactivity in general.”

In fact, I did not really care much about “the function” of the hippocampus. The structure had its own intrinsic beauty, first displayed by the drawings of Ramon Y Cajal and Lorente de No, later by the anatomical studies of Blackstad and his students; and a simplified cortex well suited for electrophysiological approaches, as exploited early on by Per, and appreciated by Tim from afar, a structure ready to reveal its secrets. On joining a lab, one does what that lab is good at, and so, in Per’s lab, I soon became fascinated by the internal workings of the hippocampus, in particular the dentate gyrus, as reflected in the title of my thesis: “Synaptic mechanisms and organization of the dentate area of the hippocampal formation.” Answers to what the hippocampus does, I felt, would come in due time and were of little concern to me then.

Why did Bliss and Lømo not refer to Hebb? many have asked, and McNaughton was “amazed that neither Hebb nor Marr was referred to in our paper” when he first saw it on his return from Erice in 1973 (see earlier). In the book chapter that Tim, Tony, and I published in 1973, and where we review and discuss our findings from both anesthetized and unanesthetized rabbits, we do refer to both Hebb and Marr together with several others as follows: “Synapses with this sort of properties, in one guise or another, feature in many theoretical discussions of learning.”

I knew about H. M., the patient with intractable epilepsy treated in 1954 by bilateral resection of the temporal lobes, including the hippocampal formation, who lost the ability to remember events that had occurred minutes earlier. This knowledge and related knowledge from other reports of memory dysfunctions after damage to the hippocampus probably expain that I did refer to theories of learning in describing my findings (see earlier). But again, things appeared less clear then than now. Citing Brodal again:

The belief that the hippocampus is involved in memory functions is based chiefly on experience with patients . . . Autopsy was carried out on only a few of the patients, and convincing evidence has never been produced that damage to the hippocampus is responsible for the loss of recent memory that occurs following bilateral removal of the medial part of the temporal lobe (see Horel, 1978, for references). Are the memory disturbances due to affections [sic] of non-hippocampal parts of the temporal lobe? Horel (1978), who discusses these relations in an extensive study, produces good arguments for an affirmative answer to this question. No final conclusion is as yet possible about the structures in the temporal lobe whose damage results in loss of recent memory. However, at present evidence for a close relation of the hippocampus to memory function is rather weak. There appears to be a growing skepticism about theories that consider certain brain regions specifically related to memory. Perhaps the most important common factor is a general disturbance of brain function. There are interesting features in common between the search for “the site of memory” and the search for “the site of consciousness,” discussed in Chapter 6.

Brodal then cites Weiskrantz (1978): “The striking aspect of the hippocampus is the anatomical elegance of its structure, revealed in detail in the past few years. In contrast there is really appalling ignorance about what this elegance means” (pages 686–689). In our 1973 paper Tim and I refer to the hippocampal formation as “a region of the brain which has been much discussed in connection with learning and memory,” and give some references, although we do not specifically refer to Hebb or the patient H. M.

Hebb’s neurophysiological hypothesis (1949) famously starts with the words, “When an axon of cell A is near enough to excite a cell B. . . .” It has always surprised me that this formulation is treated with such reverence among neuroscientists. I did not know about the hypothesis in 1966 and I don’t see now that it would have made any difference to what I did then or Tim and I would do later, based as it was on speculation without evidence. Many scientists at the time and before, Konorski, Eccles, Burns, Bliss, and others, believed that memory and learning had to involve long-lasting changes in synaptic efficacy and some looked for such changes in structures outside the hippocampus without finding them. Some studied the effects of high-frequency stimulation in the hippocampus without looking for aftereffects (Cragg and Hamlyn, J. Physiol., 1955). Others did look for aftereffects but found that they lasted only up to some minutes, too short to be of relevance to learning and memory (Green and Adey, EEG Clin. Neurophysiol., 1956; P. Gloor et al., EEG. Clin. Neurophysiol., 1964; Andersen, Acta Physiol. Scand., 1960; Andersen et al., Acta Physiol. Scand., 1966).

What Hebb did, in my view, was to formalize some current ideas with an apparent rigor that presumably helped his theory to become widely accepted. It did not have any obvious relevance to the homosynaptic potentiation that Tim and I described. It emphasized a requirement for coincident pre- and postsynaptic firing, although later work showed that such firing is not necessary. For example, in our own experiments, brief conditioning 100 Hz trains induced LTP despite failure of granule cell firing after the first stimulus due to the high frequency-induced depolarization and spike inactivation. It did not describe the more interesting model where two cells converge on a third so as to explain associative conditioning between weak and strong inputs, later to be amazingly well explained by the discovery of NMDA receptors requiring strong depolarization (the strong input) to allow glutamate from the weak input to open NMDA receptors and to allow influx of calcium for strengthening of the weak input. Hebb himself expressed surprise at so much excitement about this particular part of his theory. The idea was, he said according to McNaughton, “an old one, dating back at least to Lorente de No, and the principle was obvious to anyone who had considered the principles of associative learning. Something like cooperativity had to be present in the nervous system.” Would the enormous progress of recent years in uncovering mechanisms of learning and memory not have occurred if Hebb had not formulated his hypothesis? I doubt it.

Failing to Reproduce Bliss and Lømo (1973)

When Bliss and Lømo (1973) appeared, I had already left the field. This had not at all been my intention. Arriving In London in 1969, I joined Tim at Mill Hill about once a week to continue our work. To our dismay, LTP was now far less impressive and often absent. We could not bring the experiment under sufficient control for further systematic analysis and had to abandon the project. We considered importing rabbits from Norway. Perhaps they were smarter. But this idea, only partly a joke, had to be discarded when similar difficulties arose in Oslo when I returned there in 1971. Back in Oslo, I was joined by Tony Gardner Medwin to continue work on LTP. Tony had recently published a theoretical paper in Nature entitled “Modifiable Synapses Necessary for Learning” and, with Tim Bliss, had just finished experiments in his own lab that demonstrated LTP in the unanesthetized rabbit lasting up to 3 days after a single conditioning train of stimuli and, in one animal, lasting several weeks after a series of such trains. Again, what little LTP Tony and I saw was modest and highly variable. We tried all we could think of to improve the situation, but to no avail. I never worried that what Tim and I had found was not true. One cannot begin to doubt something one has seen over and over again. But how to explain it?

Until recently, I had no idea how to explain it. But now, papers have appeared showing that stress markedly suppresses LTP, as observed in vivo and in slices from stressed animals, effects mimicked by administration of corticosteroids. The rabbits that Tim and I studied were bought from a local farmer for the equivalent of about £3 and brought to the institute by the farmer. Perhaps his rabbits were less stressed than the rabbits I studied with Tim in London or with Tony later in Oslo. Differences in animal strain, age, handling, and previous history are all factors that affect an animal’s response to stress and might be responsible for the variability in LTP that Tim and I also observed (see earlier). Perhaps such factors also explain why Per and others studying frequency potentiation in the hippocampus before the LTP era failed to see long-lasting aftereffects. I cannot know, of course, but it seems plausible. It strengthens the impression that LTP, like learning and memory, is a rich and subtle phenomenon sensitive to a variety of modulators.

Failing to study LTP in vivo, Tony and I then tried to do so in slices of the hippocampus. Across the corridor in Per’s lab, Knut Skrede, who had worked with Tim and Per on the lamellar and population spike experiments, and was taking a year off from his medical studies, had set up such a technique. Skrede had learned the technique from Chris Richards during a visit to Tim at Mill Hill. Richards, in turn, had come from the lab of McIlwain who, with Chosaburo Yamamoto, had pioneered the technique. Skrede’s setup consisted of a metal cooking pot containing the perfusion fluid, an aquarium heater bought from a local hardware shop, a silk mesh floating on the surface to support the slices, and a humid gas mixture of O₂+CO₂ blowing over the slices. He was later joined by Rolf Westgaard and together they did the experiments that showed for the first time that the entire trisynaptic circuit, perforant path to dentate gyrus to CA3 to CA1, survived in the transverse slice and could be activated in sequence by stimulating the perforant path. For most of this time Per was away on sabbatical in Charles Philllip’s lab in Oxford and was not, as I understand it, directly engaged in the project. Yamamoto (1970) introduced the transverse slice, but not in the context of the trisynaptic circuit. How the idea to study the trisynaptic circuit in slices arose is not clear but from the lamellar organization of this circuit already demonstrated, it was a natural thing to do.

Tony and I set out to improve on Skrede’s setup, or so we thought, by submerging the slices in a small perfusion chamber that we placed on the stage of a high-power compound light microscope for transmitted light. Layers, cell bodies, and dendrites now stood out in much greater detail than with a low-power dissection microscope and incident light, beautiful to see and useful for more precise placements of electrodes. But again, we failed. The excitability of the submerged slices remained poor. Perhaps we did not master the technique of cutting the slices by hand, as we had to in those days, or the slices did not like being submerged, not getting enough or too much oxygen, which we tried to vary as best we could. I did not want copy the setup across the corridor because I liked ours and because I sometimes heard sudden sharp noises from their loudspeaker. It turned out that drops of water condensed on the outside of the recording electrode and every time it dropped or flowed down onto the slice, bursts of spike discharges, amplified by the loudspeaker, resounded in the air. Impressed by this observation, Tony and I started to dilute our perfusion fluid with distilled water, and for every dilution the excitability in the slice improved. But when we reached near half-normal tonicity, we felt we were studying pathology rather than physiology and gave up. Skrede and Westgaard (1971) even refer to this finding as follows: “Preliminary experiments indicate that the excitability of the preparation in vitro is highly dependent on the ionic composition of the bathing medium (Gardner-Medwin and Lømo, personal communication).” After all this travail, Jan Jansen came back from a sabbatical at Harvard and suggested collaboration on a problem related to my work in London on the nerve–muscle preparation. That work left a mine of interesting problems that appeared much easier to address than LTP. So I switched to explore that mine for the next nearly 40 years, while Tony, who wanted to stick with brain, went on to study on his own, and for the rest of his time in Oslo, impulse conduction in parallel fibers in the cerebellum, work that was published in the Journal of Physiology.

While Tony and I struggled in Oslo, Tim did likewise in London. He tells me that he and Chris Richard were unable to demonstrate LTP in the dentate gyrus in vitro, because, as became clear later, they did not add bicuculline, which was needed to block the tonic inhibition that prevented LTP from developing (though not, luckily for the transverse slice, in areas CA3 and CA1). Tim then turned to other problems until Graham Goddard came to visit Tim in 1974. He was then on sabbatical with John O’Keefe but came to Tim at Mill Hill for a few days to look for LTP in rats. In the one rat they tried, they did not see any LTP but when Goddard returned to Halifax he did, and in collaboration with Rob Douglas, the study of LTP in vivo, now in rats, was born again.

Concluding Remarks on the Discovery of Long-Term Potentiation

Concluding these recollections about LTP, I note that the events just described took place 40 years ago. Few notes remain, no diaries, a few letters, no records from the experiments that Tim and I, or Tony and I, did. To my regret they must have disappeared, unintentionally, in 1990, when our institute moved from the old University buildings downtown to new buildings in the suburbs of Oslo. Papers and records related to the work for my thesis I did keep because it was always my intention some day to come back to them and publish the papers so far unpublished, as I finally did in 2009. As I write, questions arise: What did I or people central to the story do then? What did they say? Whose idea was it? And repeatedly I am unable to answer because I have forgotten. Again, as I was writing, my wife came with some letters I wrote to her from London in 1971 when I stayed on alone for a few months to finish the work there. Reading them now brings back memories that would have been gone forever without these letters. What better illustration of the value of letters and diaries and of the regrets one feels at not having been more disciplined and forward looking when interesting things happen in one’s life? And how difficult it is, without such records, to be sure that one’s recollections are reasonably close to what actually happened.

With such thoughts in my mind I will try to answer a question Tim has asked: Would Oslo have followed up my observations in 1966 if he (Tim) had not come to the lab in 1968? Probably not. I might well have wanted to return to my early observations of long-term changes but would hardly have had the time considering the direction my Ph.D. work was taking (see earlier). I would have finished my thesis and gone to London for further training. There, as it turned out, the answers I obtained to different problems on a different preparation were received with much greater interest than any results relating to LTP (see later discussion). On my return to Oslo, would I then have chosen the hippocampus over muscle, with the success in London behind me and without the work that Tim and I did together? Hardly.

Without Tim’s year in Oslo, Knut Skrede would almost certainly not have gone to Mill Hill in the summer of 1970, where he learned the slice technique and was inspired to set it up in Oslo. The purpose of his visit was to write a paper with Per and Tim as coauthors, and it was Tim’s suggestion that, when there, he might be interested in learning the slice technique. At that time Tim and Richards used “longitudinal” slices. As Tim writes: “the hippocampus was laid out flat and a slice was cut that contained the whole septal-temporal extent of the lower blade of the dentate gyrus.” How it came about that Skrede chose the transverse slice, containing the pyramidal cell fields in addition to granule cells, is not clear but as already noted it was a very natural thing to do at that stage. Without this background, Schwartzkroin and Wester would probably not have demonstrated LTP for the first time in slices in 1975 in Per’s lab.

As far as I can remember and understand from talking recently with those involved, Per did not directly engage himself in these early projects on LTP or on the slice. That would come later. We were doing our projects. Per was busy with his. He provided essential support but did not interfere with the way we did the experiments and we were very grateful for this. I felt that he considered our results on a par with other results obtained in the lab at the time. So I think the answer to Tim’s question must be that neither Per nor I would have followed up my findings from 1966 had Tim not come to the lab in 1968, at least not for some years.

One of the more rewarding experiences of my involvement with LTP has been the lifelong friendship that Tim and I developed from our first days together, the fun of working together, the satisfaction of discovering how easily we agreed on how to do things and view the developments in the field, and, above all, especially now that LTP has become so important to neuroscience, that our memories and interpretations of what happened then match so well. Wonderful also that now 40 years after our last experiments together we are collaborating again, setting up experiments to try to solve some unsolved problems from back then. What will come of it remains to be seen. Time is running short.

London (1969–1971): The Trophic Hypothesis

I arrived in London in October 1969 with Anne, three children between 1½ and 7 years of age, and an au pair, a young girl from our neighborhood in Norway. We stayed in a hotel in Gower Street with money running out and the au pair desperate with homesickness. After 3 or 4 days, the girl already on her way home, Tim came to our rescue. Together we looked at apartments for rent and after about a week we were nicely settled in a small but charming “cottage” in Hampstead Garden Suburbs.

Ricardo Miledi suggested that Jean Rosenthal and I should team up in a small lab down the corridor on the fifth floor of the Department of Biophysics. Jean had just arrived from Yale after a Ph.D. with Bob Martin. Other labs down the corridor housed Nick Spitzer, Wolfgang Grampp, John Heuser, Dale Purves, Bill Betz, Bert Sakmann, Lincoln Potter, Mike Dennis, among others. Miledi suggested that Jean and I should try to block impulse conduction in the sciatic nerve of rats without damaging the nerve and causing denervation. In normal muscle fibers the sensitivity to transmitter acetylcholine is restricted to the neuromuscular junction. But after denervation the sensitivity increases dramatically along the entire length of all the muscle fibers (acetylcholine supersensitivity), as was well known at the time. By blocking nerve impulse conduction and paralyzing the muscle without causing denervation, we might find out whether the supersensitivity was caused by lack of impulse activity in the muscle or a putative motor neuron-derived trophic factor believed at the time to be released from the nerve terminals at neuromuscular junctions. Miledi had already done experiments, mainly in the frog, which he interpreted to mean that the supersensitivity occurred because denervation (axotomy) interrupted the flow of the trophic factor and not because it interrupted nerve-evoked muscle impulse activity.

In their classic work on the effects of cross-reinnervating fast and slow muscles, Buller, Eccles, and Eccles (J. Physiol., 1960) discussed whether alterations in impulse activity or trophic factors were responsible for the observed changes in muscle contractile speed. They favored the “trophic hypothesis” and presented a figure showing schematically how the putative trophic factor travelled down the axon of a motor neuron, crossed the synapse, and continued travelling intracellularly to either end of the muscle fiber. Regarding the acetycholine supersensitivity caused by denervation, Eccles wrote as follows in his book The Physiology of Synapses (1964, p. 246): “In summary of the preceding section it can be stated that the evidence for a trophic influence from nerve on to muscle membrane is conclusive, but it is still uncertain whether it is entirely effected by unique trophic influences or whether in part by the spontaneous emission of quanta of acetylcholine. The trophic influence apparently travels along the motor axon with a velocity ranging from 1–2 mm/hour.” This being the accepted idea of the day, one might expect that muscle fibers paralyzed by blocking nerve impulse conduction would retain normal sensitivity to acetylcholine, as predicted by the trophic hypothesis. Some distinction, however, is in order. Since the heyday of the trophic hypothesis, neural agrin has been established as a substance that induces and maintains the neuromuscular junction after axonal transport and release from motor nerve terminals. However, agrin is not considered trophic, as the hypothesis was understood then because its actions are restricted to the neuromuscular junction. Target-derived substances acting retrogradely on motor neurons also fall outside the trophic hypothesis.

At the Institute of Neurology, Queen Square in London, research on demyelination was ongoing, and Jean and I heard that diphtheria toxin was used to induce it. As a first approach, we therefore injected diphtheria toxin under the perineurium of the sciatic nerve in rats. A week or so later, the leg on the injected side was paralyzed and the muscle fibers were supersensitive to acetylcholine, like the supersensitivity observed after denervation. And yet spontaneous acetylcholine release (MEPPs) and muscle responses to stimulation of the sciatic nerve below the injected site were essentially normal. Apparently, apart from the conduction block, the axons were intact. Then one day, Steve Roper in Jack Diamond’s lab in the next building came over and told us about a paper by Robert and Oester (J. Pharmacol. Exp. Ther., 1970). This paper reported that in rabbits no acetylcholine supersensitivity was observed in muscles distal to a silicone cuff mixed with lidocaine, a local anesthetic, around the sciatic nerve despite complete impulse conduction block and muscle paralysis. This seemed a more direct and controlled way of blocking impulse conduction than using diphtheria toxin and we immediately adopted it. And again, with this technique too, full acetylcholine supersensitivity appeared in muscle fibers that appeared normally innervated. Later, Jean tried to replicate the findings of Robert and Oester in the rabbit without getting a clear answer. The experiment was more difficult on the larger nerve and muscles of the rabbit. In Lømo and Rosenthal, 1972, we therefore wrote: “So far, we have no explanation for this contradictory finding [Robert’s and Oester’s], but only note the species differences.”

The Importance of Denervating Muscles and Stimulating Them Electrically

Denervation-like acetylcholine supersensitivity in muscles innervated by “silent” but otherwise apparently intact nerve fibers suggested that spontaneously released acetylcholine or some unknown factor might not be responsible for the acetylcholine supersensitivity as postulated by the trophic hypothesis. But we could not be certain because blocking impulse conduction might also affect axonal transport. The next step was obvious. We would have to remove all neural influences by cutting the nerve and substitute nerve impulse-evoked muscle activity by direct stimulation of the muscle through implanted electrodes. If such muscles became insensitive to acetylcholine outside the denervated endplates like normally innervated fibers, evoked muscle impulse activity would have to be the essential factor. This was the critical experiment, and I cannot remember that we discussed it with Ricardo at that time. When things started to go well, we were left to ourselves and liked it that way.

We were into January, 1971, before we had our first successful experiments with direct stimulation of denervated muscles. There had been several difficulties. Ordinary electric wires under the skin invariably broke, usually within 1 day of implantation due to the rat’s movements. I remember going to a shop in nearby Tottenham Court Road selling hearing aids to get flexible multistranded wires, which solved the problem. Polarization of electrodes was another problem, which was solved when we began using stimulus pulses that were only 0.1 ms in duration, unusual at that time for stimulating denervated muscle, and switching polarity between each train of stimuli. More of a nuisance than a problem was the observation that the rats under stimulation in the lab tended to move around more in one direction than the other. We therefore spent much time “unwinding” the wires that connected the rat to the stimulator on the shelf above it, done also outside “normal” working hours since intermittent stimulation went on day and night for up to 2 weeks. Today, the use of commercially available rotating contacts easily solves this problem. For stimulation of the soleus muscle we ended up using platinum wires inside a silicone cuff that we molded to fit around the Achilles tendon, while the most distal portion of the muscle was activated with the short platinum wires connected to the hearing aid wires that ran under the skin to a plug attached to the skull with screws and dental cement. I remember contacting Patrick Wall in the next building to hear about how they attached wires to record from rats that moved about. I also visited John O’Keefe who was developing his technique for recording from single cells in the hippocampus of freely exploring rats, cells that he later called place cells.

Then, finally, one day in February we had a group of four or five rats, each in its own wide plastic bucket with its sciatic nerves cut in both legs and the soleus muscle in one leg apparently well stimulated for at least 5 days. I remember well the first experiment. I removed both soleus muscles, placed them side by side in a perfusion chamber, inserted a recording electrode into a surface fiber of the denervated unstimulated muscle and, on the outside of that fiber, positioned a micropipette containing 3M acetylcholine chloride. Moving the electrode to different positions along the length of the fiber and at each position passing a short electric pulse through the electrode to eject acetylcholine, I evoked large depolarizing endplate-like potentials along the entire length of that fiber and others tested in the same way, as expected from the supersensitivity known to occur after denervation. In the other denervated muscle, however, which had been chronically stimulated, I got no response. Could there be something wrong with the electrode? A broken pipette tip, leakage of acetylcholine, and desensitization of acetylcholine receptors in the muscle fiber membrane were common problems. How reassuring then that subsequent tests on the unstimulated muscle, using the same pipette, evoked the same large responses as before. I then returned to the stimulated muscle fibers, moved the acetylcholine-containing pipette along the fibers, and saw no response except at one restricted site on each fiber that corresponded to the denervated endplate. The distribution of acetylcholine sensitivity at such sites was in exact agreement with that observed at normally innervated endplates but MEPPs were absent because these endplates were denervated. The result was enormously exciting. The difference between stimulated and unstimulated fibers stood out like the difference between night and day. In one stroke, existing understanding seemed turned upside down. Absence of a nerve-derived “trophic factor” could not be responsible for the acetylcholine supersensitivity of denervated muscle. The controlling factor had to be evoked muscle impulse activity.

Immediately, however, the question arose: Is the result reproducible? The following day, Jean examined the next rat in the series. I remember walking up and down in the corridor outside the lab nervously awaiting the result. To my immense relief, Jean got the same result. Thereafter, it was relatively smooth sailing. Chronic stimulation starting at the time of denervation not only prevented acetylcholine supersensitivity from appearing but made the supersensitivity disappear when the stimulation started after it had fully developed. The denervated extensor digitorum longus responded similarly to direct stimulation. While many denervated stimulated fibers were indistinguishable from normally innervated fibers (except for the absence of MEPPs), others displayed varying degrees of supersensitivity in some stimulated muscles. In some of these muscles it was obvious that the implanted electrodes had not stimulated effectively all the fibers. But, as would become clear later (see later discussion), by causing peripheral nerve branches to degenerate, the axotomy also elicited an inflammatory response in the muscle that in itself could induce some degree of acetylcholine supersensitivity, thus counteracting the effect of stimulation. Finally, we showed that stimulating the sciatic nerve through electrodes implanted on the nerve below a paralyzing block also prevented supersensitivity from appearing. But this result could not answer what to us was the fundamental question: Was there or was there not a factor carried by axonal transport as postulated by the trophic hypothesis? Only by removing the nerve altogether and replacing nerve-evoked impulse activity with stimulation-evoked impulse activity could we get an answer and the answer seemed unequivocal. It had to be muscle impulse activity.

Life in the Department of Biophysics

Jean and I started out doing experiments together but found it difficult. Together in the small lab with both of us having our hands on the experiment, we got into arguments about who was to do what next. Since one person could easily do the experiments, we therefore early on decided to split the project between us. Jean would address some aspects of the project. I would address others. She would have the lab to herself on some days, and I would have it on other days. Jean took care of all the electron microscopy showing that neuromuscular junctions belonging to axons in cuffed sciatic nerves appeared structurally normal. She worked on replicating the results of Robbin and Oester and began studying effects of our interventions on muscle contractile properties. I developed the approach for stimulating denervated muscles and did most of the tests for acetylcholine supersensitivity until I returned to Oslo at Easter in 1971. We both worked at writing up the bulk of the paper and, when I left, Jean finished it after consultations with Miledi. There were also further stimulation experiments to be done. I was very happy with our arrangement. It allowed us to stay on friendly terms, enjoy each other’s company outside the lab, and to collaborate effectively to finish the work.

I very much enjoyed my time at the Department of Biophysics. Considering the stimulating research environment and the good outcome of our work, it was also unusually rewarding. I remember the “time off” periods in the department’s seminar and lunchroom around 11 o’clock when people from the labs along the corridor would come in for coffee or tea and chats. Miledi was often there, a source of stimulating and interesting conversations. Katz came in rarely, and I remember being disappointed when he let us understand that he was not interested in “talking shop” there. He would rarely, if at all, discuss his own or other people’s work at coffee time. At that time Katz and Miledi were studying acetylcholine-induced membrane “noise,” but I did not know about this important work before it was published in Nature. Katz received the Nobel Prize in 1969 and some time after the announcement I remember him coming into our lab asking us how we were doing and what we thought about some more general aspects of science. Otherwise, I saw little of Katz during my time there. I am sure he would have been very helpful had we needed help, but for me our problems appeared too trivial and were mainly of a practical nature that we had to sort out ourselves.

We hesitated to tell Miledi about our results. They stood in such contrast to his own results and interpretations that I felt awkward at breaking the news. However, when a moment came at coffee time, his response was short, and as far as I can remember, something like: Oh, I had expected it to be different. Later, when an abstract was being prepared for a talk that Jean would give in Paris and later still, when the full paper was being completed, relations with Miledi became somewhat difficult. We could not agree on how references to earlier literature should be phrased or on the wording of some other aspects of the paper. In the end, Miledi did not want to have anything more to do with the paper because, as I remember Jean telling me, “We did not listen to him anyway.”

The day before I left London Jean and I had an appointment with Katz to discuss our work. However, when Katz learned that we had not yet written up the Discussion, he seemed irritated, commented that the Discussion is an important part of any paper, and left me at least with the impression that we were wasting his time. Hence the meeting became quite short as I said we would be back when the paper was closer to completion. On the last day of my 1½ years at the institute as I stood wating for the lift with a bag containing some of my belongings from the lab, Katz emerged from the lift together with John Eccles and Stephen Kuffler. Seeing my bag and addressing Eccles and Kuffler, he then said something to the effect that “there go our fine scissors”. Perhaps some people did take with them expensive instruments when they left the department but I hardly liked the suggestion that I would be one of them. Perhaps I was being considered “difficult” by Katz and Miledi since we did not agree with Miledi about how to write certain parts of the paper (see earlier discussion), and perhaps this accounts for what I felt was a rather odd farewell.

The Reception of Our Results on the Trophic Hypothesis

Our results were immediately well received by neurophysiologists not studying the trophic hypothesis, and less well by others who did (see later discussion). The issues involved were well known and the significance of the results promptly appreciated, in contrast to the reception of the results on LTP (see earlier discussion). I remember being invited to give a lecture on neural control of muscle properties at a high-profile meeting in Oxford in 1972 or early 1973. I suggested to the organizers that perhaps I could talk about some interesting unpublished results from the hippocampus instead, but it was the muscle they wanted to hear about. I find it interesting that while Lømo & Rosenthal (1972) was received with immediate interest but now seems largely forgotten, Bliss & Lømo (1973) took many years to be widely recognized in a way that now seems to endure.

In the following I describe some examples of the criticisms that were leveled against our experiments in London and later in Oslo because I think they contain a lesson. Today, it seems clear that the trophic factor postulated by so many does not exist (see later discussion). It may therefore be instructive to go over the evidence that led to the trophic hypothesis and see how they now can be given alternative more plausible explanations.

R. J. Blunt and G. Vrbova (Pflügers Arch., 1975) reported that the local anesthetic used in our cuffs was too toxic, that such cuffs produced extensive denervation, and that the effects were irreversible. However, we had noted the problem of partial nerve degeneration in our paper. In our experiments, the effect was reversible in cases where there was little or no degeneration. The presence of some degeneration was not important for the conclusions we made, and subsequent work by others and us fully confirmed them. As it turned out, the addition of a local anesthetic to the cuff was unimportant. The long-term block was caused by nerve compression and occurred (with a delay) also with plain cuffs, as used later. The critical part was the diameter of the cuff’s central canal that accommodated the nerve; slightly too wide and no block occurred, slightly too narrow and much nerve degeneration ensued.

S. S. Deshpande, E. D. Albuquerque, and L. Guth (Exp. Neurol., 1976), concluding that “both the prejunctional nerve membrane and the postjunctional muscle membrane are regulated by a neurohumoral factor,” made the following comment: “Furthermore the experiments using prolonged electrical stimulation [Lømo and Westgaard, 1975; Westgaard, 1975] can be criticized because they were performed on chronically denervated muscles. The denervated muscle fiber is a cell that has been released from many of its physiological regulatory controls; given our present state of knowledge one cannot use such pathological tissue to make inferences about the role of muscle activity on physiologically normal muscle fibers; this experimental approach appears to us to be inappropriate for the study of trophic nerve function.” This seemed an odd criticism. To me it was perfectly in order, following common research practice, first, to remove some unidentified factor and, then, add a specific, identified factor to see to what extent it could replace the unidentified one and restore normal function. In our case, direct muscle stimulation did restore normal nonjunctional properties, not only with regard to acetylcholine sensitivity but also, as later work showed, with regard to a host of other nonjunctional properties.

V. Witzeman, H. -R. Brenner, and B. Sakmann (J. Cell Biol., 1991), comparing the effects of denervation, direct muscle stimulation, and nerve blockage by botulinum toxin, α-bungarotoxin, or tetrodotoxin on acetylcholine receptor subunit expression in muscle, concluded that “levels of the γ-subunit in the entire fiber are reduced by a negative neural factor and possibly also by nerve-induced electrical muscle activity.” This conclusion surprised me because Brenner had earlier shown that stimulation of denervated muscles blocked the expression of γ-subunits, a necessary component of the extrajunctional acetylcholine receptors induced by denervation and underlying the acetylcholine supersensitivity that Jean and I had studied. This result and many others (see later discussion) have been cited as evidence for the trophic hypothesis in textbooks and elsewhere. For example, in his Chapter 10 in the handbook Myology (1994) Alan Grinnell writes: “Because the direct-stimulation experiments are so convincing, it is tempting to conclude that muscle activity is the only factor responsible for many of the muscle properties changed by denervation or that it is essential to their regulation. However, there is compelling evidence that activity-based effects are superimposed on at least two other mechanism of trophic regulation.” He then discusses this evidence under the headings: “Stump length effects,” “Nerve breakdown products,” “Nerve conduction block,” “Block of axonal transport,” and “Pharmacological block of synaptic transmission.”

Attempts to Prove the Fallacy of the Trophic Hypothesis

The evidence that Grinnell found compelling, I did not. The demonstration over and over again that direct stimulation of muscle could restore normal muscle properties outside the neuromuscular junction made me ask: What can then be the role of a hypothetical trophic factor? How then to explain the “compelling” evidence listed by Grinnell? After London, and my failure to pursue LTP, trying to answer such questions was what much of my work was about in the years that followed. And here are my answers.

But first some background is necessary. Jones and Vrbova (J. Physiol., 1974) showed that a foreign body, such as a small piece of thread, placed on the surface of a muscle induced a local supersensitivity to acetylcholine underneath the inflammation at the site of the thread. Later Clarke, Slater, and I confirmed this and spent much time trying to find out what was going on without succeeding. In Pisa, Italy, Alberto Cangiano and his colleagues showed that in partially denervated muscles, fibers with intact innervation developed a moderate degree of supersensitivity to acetylcholine (and other denervation-like properties) in proportion to the degree of denervation. Moreover, when they reversibly blocked impulse conduction in the intact axons, the innervated fibers became as supersensitive as the denervated fibers. By comparing the development of denervation-like changes in denervated and in innervated but chronically blocked muscles, they also showed that the earlier and greater effects of denervation, already well known, were transient and that after 2 weeks there was no longer any difference between denervated muscles on the one hand and innervated but blocked muscles on the other. Finally, in denervated muscles, re-innervation by chronically blocked axons did not suppress their supersensitivity to acetylcholine or other signs of denervation. Such results have two important implications. First, denervation (axotomy) results in transient changes in the muscle, probably of an inflammatory nature related to the breakdown of intramuscular nerve branches that by themselves induce acetylcholine supersensitivity and other denervation-like changes. Second, no evidence emerged that blocked but otherwise intact nerves deliver any trophic signal capable of counteracting the signs of denervation. Others disputed some of these findings or obtained contradictory results. However, in my view, Cangiano’s experiments, some of which were published in Nature and Science, were by far the most careful and convincing.

Our own results were consistent with these findings. In addition, they revealed the importance of impulse activity and impulse patterns in controlling muscle fiber properties, perhaps the first demonstration of the importance of impulse patterns in controlling postsynaptic phenotypic expressions. Here is a brief summary of our findings.

“Fast” pattern stimulation (100 Hz for 1 s every 100 s) starting at the time of denervation prevented the development of acetylcholine supersensitivity altogether. In contrast, “slow” pattern stimulation (10 Hz for 10 s every 100 s) restored normal sensitivity only after an initial marked but transient increase in acetylcholine supersensitivity, maximal on day 3 and over by day 10.

Doubly innervated soleus muscle fibers were obtained by letting the denervated soleus become re-innervated first ectopically by a “fast” nerve (the superficial fibular nerve) and then at the original endplates by the original “slow” soleus nerve. In such muscles cutting the slow soleus nerve caused no supersensitivity to appear around the denervated soleus endplates, whereas cutting the fast nerve resulted in marked local transient acetylcholine supersensitivity around the denervated fibular endplates. In the first case, only the fibular nerve delivering fast activity remained intact. In the second case, only the soleus nerve delivering slow activity remained intact.

Points (1) and (2) show that fast impulse activity (high frequency) prevented the development of transient acetylcholine supersensitivity around denervated endplates, whereas slow activity (low frequency) did not. Moreover, the result was the same whether the activity had been imposed naturally by a nerve or artificially by electrical stimulation. Evidently, fast activity was more efficient than slow activity in counteracting the expression of acetylcholine supersensitivity induced by degeneration of peripheral nerve branches in the muscle, an effect of what Cangiano and I have called “products of nerve degeneration.”

The rate at which fully developed acetylcholine supersensitivity declines after onset of direct stimulation depends strongly on the stimulus patterns used, the decline being faster with higher frequencies than lower frequencies, and with larger amounts than smaller amounts.

The rate of decline also becomes slower with longer intervals between stimulus trains, being weak but still noticeable with as much as 5.5 h separating each short single stimulus train.

Delivering a certain number of short stimulus trains over a 6 h period every 24 h is much less effective than when the same number of trains is spread out evenly over the same 24 h.

Fast pattern stimulation is only effective if it starts earlier than 1 day after denervation. If it starts after 1.5 days, marked and transient acetylcholine supersensitivity follows.

Points (3)–(6) lead to the following conclusions. Acetylcholine supersensitivity and other denervation-like changes develop when a period of inactivity exceeds a certain critical duration. Even very small amounts of activity are effective provided this period is not exceeded. When exceeded, processes causing acetylcholine supersensitivity (and other denervation-like changes) are set in motion and will run their course lasting some days even as activity is reinstated. Fibrillatory activity has little effect on acetylcholine supersensitivity because the periods of inactivity are too long.

With this background it is now possible to provide more plausible explanations of the results listed by Grinnell and others as evidence for a neurotrophic factor. The acetylcholine supersensitivity observed after cutting one of two nerves to doubly innervated muscle fibers in the frog is more likely the result of “products of nerve degeneration” than interruption of any hypothetical trophic factor by the axotomy. The delay in onset of denervation changes caused by cutting the nerve far from the muscle rather than close is more likely due to the later onset of nerve terminal degeneration in muscles with the “long nerve stump” rather than a longer release time for the postulated trophic factor. Given that very small amounts of muscle impulse activity is needed to suppress acetylcholine supersensitivity in denervated muscles (and probably even less in innervated muscles), it must be very difficult to rule out the presence of such activity in experiments based on spinal cord isolation, immobilization, or cuffs around nerves. Cangiano has convincingly demonstrated how difficult it is to completely block all axons over long times by cuffs around the nerve and how much care is needed in interpreting the results.

The use of toxins presents its own problems. For example, when colchicine is applied to the sciatic nerve, acetylcholine supersensitivity (and other denervation-like effects) appears in distal leg muscles with preserved neuromuscular transmission. Since colchicine blocks axonal transport, Albuquerque, Thesleff, and their colleagues concluded that failure of the trophic factor to reach the muscles was responsible. However, knowing the effects of direct muscle stimulation, I thought there might be another explanation. I therefore applied colchicine to the sciatic nerve in one leg, as the others had done, and like them observed the supersensitivity downstream. But I also looked at other muscles in the body and found, as Cangiano did independently, that these muscles were similarly supersensitive. Could there be a systemic effect of colchicine on muscle independent of any effects on the nerve (Lømo, Nature, 1974)? I then cut the sciatic nerve in one leg, allowed supersensitivity and other changes to fully develop, injected colchicine in the thigh (away from the nerve that had been cut anyway), and started stimulation. The result was exciting. In the presence of colchicine in the thigh, stimulated denervated muscles developed the same supersensitivity as innervated muscles, whereas in the absence of colchicine, stimulated muscles became as insensitive as normal muscles. Evidently, the effect of colchicine on the muscle had nothing to do with its effect on the nerve. Again, contradictory reports and criticisms followed but soon interest in colchicine as a way to identify activity-independent trophic effects petered out. In the case of Witzeman et al. (see earlier) they based their conclusion on comparing the effects of denervation with the differential effects of several toxins on acetylcholine receptor subunit expression. The expression of γ-subunits after botulinum toxin was unexpectedly high. Could injection of the toxin, a foreign protein, into the muscle and accompanying inflammation have boosted the effect? The expression of γ-subunits after 9–10 days of a tetrodotoxin block of the nerve was unexpectedly low. Could the block have been incomplete for some of the axons for some of the time? One does not know, but the possibility is there. So how much trust should one place on such results knowing that evoked muscle impulse activity can account for all the effects of the nerve on these properties?

Concluding this part of my story, the controversy that marked the field for many years now seems over. The essential role of nerve-evoked muscle impulse activity is generally accepted. No convincing evidence for the postulated trophic factor appears to exist. That Chapter 10 in the 1994 edition of Myology entitled “Trophic Interaction between Nerve and Muscle” has been removed from the latest edition strengthens this impression. Despite many attempts to isolate a candidate trophic factor from motor nerves, no one has yet succeeded. In fact, what has been isolated usually has the opposite effect from that expected, for example, increasing the expression of acetylcholine receptors. Of course, it is difficult to prove that something does not exist. Convincing evidence may still arise in species not yet examined. Nevertheless, with hindsight I find it surprising that so many have invested so much energy in defending a concept for which there was so little direct evidence, so many plausible alternative explanations, and such strong evidence for the essential role of evoked impulse activity.

Control of Muscle Contractile Properties

The cross-reinnervation experiments by Buller et al. (1960) referred to earlier showed that muscles are remarkably plastic with respect to their speed of contraction. It was a surprising discovery, noted inadvertently when muscles were seen to contract either slower or faster than normal after an operation performed to study plasticity of synapses in the spinal cord. To explain it, Buller et al. opted for the trophic hypothesis in keeping with the thinking of the day, although the possibility that impulse activity might play a role was discussed at length. In 1972–1973, knowing the importance of impulse activity for the control of membrane properties, we began to study whether it is similarly important for contractile properties. And sure enough, during chronic “fast” (high-frequency) direct stimulation, the denervated rat slow soleus muscle became much faster than normal. The average twitch time to peak dropped from ∼40 ms to ∼16 ms, or close to that of the normal extensor digitorum longus. Moreover, fiber typing based on myosin ATP-ase activity revealed that considerable slow to fast transformation had occurred also with respect to the type of contractile protein expressed (Lømo, Westgaard, and Dahl, 1974). Similar effects of chronic stimulation had already been demonstrated by G. Vrbova, S. Salmons, F. A. Sreter, and D. Pette, but only for indirect stimulation through the nerve. An influence by a putative trophic factor affected by the stimulation was therefore still a possibility. To circumvent this possibility, we started to stimulate denervated muscles directly and look for effects on their contractile properties.

A detailed study (Westgaard and Lømo, 1988), using different frequencies and number of stimuli for about 2 months, showed that both frequency and number were important factors controlling contractile properties in the rat soleus. Increasingly higher frequencies for a given number of stimuli caused increasingly faster twitch speed, and greater numbers for a given frequency caused slower twitch speed. In addition, greater number of stimuli caused higher fatigue resistance. Thus, the denervated soleus maintained slow fatigue-resistant properties or turned into a fast fatigue-resistant, or fast fatigue-sensitive muscle depending on the stimulus pattern used. As a consequence of briefer twitch durations, the tension-frequency curve moved toward higher frequencies, that is, toward the imposed frequency, suggesting that muscles adapt their speed to the firing frequency of motor neurons for optimal force output control. In fast extensor digitorum longus, studied in less detail, high-frequency stimulation maintained normal fast speed, whereas high amounts at low frequencies caused a change in twitch speed from normal ∼11 ms to ∼24 ms but not to ∼40 ms, which is normal for the soleus. Interestingly, however, ∼24 ms is the normal speed for slow type 1 motor units in extensor digitorum longus. Therefore, the transformation from fast to slow twitch speed appeared complete with respect to normal slow type 1 fibers in extensor digitorum longus but incomplete with respect to normal slow type 1 fibers in soleus.

Such findings led us to introduce the concept of an “adaptive range” subject to the following rules:

Muscle fibers adapt their contractile properties within certain limits.

These limits are different for different types of muscle fibers owing to intrinsic differences between the fibers.

Adaptation within these limits is controlled in a graded way by patterns of impulse activity.

Later work confirmed this concept. In collaboration with Stefano Schiaffino and his colleagues in Padova, Italy, we showed that slow pattern stimulation for 2 months maintained the type 1 phenotype in soleus but failed to induce it in extensor digitorum longus. Conversely, fast pattern stimulation maintained type 2B phenotype in extensor digitorum longus but failed to induce it in soleus (although fast types 2A and 2X were induced). In addition, intrinsic shortening velocity in soleus became only about half as fast as that in normal extensor digitorum longus, confirming the absence of the fastest type 2B fibers. Since twitch time to peak undergoes essentially complete slow to fast transformation in soleus, these results also demonstrate that individual properties within a muscle display different degrees of plasticity, or adaptive ranges. In a more recent work, we showed that intrinsic differences exist not only for different mature muscle fiber types but also for satellite cells from different muscles. Thus, muscle fibers regenerating from satellite cells in denervated soleus and extensor digitorum longus muscles acquired distinctly different phenotypes during identical fast or slow pattern chronic direct stimulation (Kalhovde et al., 2005).

We continued collaborating with Schiaffino’s group in Padova until quite recently. The focus in Padova was on intracellular signaling pathways that transform muscle impulse activity patterns into gene expression patterns for the control of type and size of muscle fibers. We contributed by providing muscles subjected to different stimulation regimes.

The Importance of Patterns of Impulse Activity

Of course, we were aware that the stimulus patterns we used to begin with were quite artificial. To learn more about the natural firing patterns of motor neurons, Rune Hennig in our lab therefore embarked on a very challenging project, to record single motor unit activity continuously over 24 h from slow soleus and fast extensor digitorum longus in rats moving or resting unrestrained in their cages. The differences in firing patterns for different types of motor units were remarkable (Hennig and Lømo, Nature, 1985). In soleus, slow units with type 1 muscle fibers fired from 300,000– 500,000 impulses per day often as trains lasting minutes at nearly constant frequency of ∼20Hz. In extensor digitorum longus, two types of firing patterns stood out. In the first type, brief, high frequency bursts of impulses dominated. Total number of impulses per 24h was only 2600–11,200, number of impulses per burst usually only 1–6, median frequency within bursts 70–90 Hz, with the first interval particularly short, up to 250 Hz (initial doublet). Almost certainly, these units were fast fatigue-sensitive units consisting of type 2B (and probably some 2X) fibers. The second type was similar to the first type except for considerably longer trains of impulses at somewhat lower frequencies making up a much larger total number of impulses per 24 h. These units were probably fast fatigue-resistant units consisting of type 2A (and probably some 2X) fibers. With this knowledge we could let our chronic stimulation protocols mimic more precisely the natural firing patterns of motor neurons.

Torsten Eken in our lab took over studying single motor unit activity when Rune Hennig left and later became professor of neurosurgery at the University of Tromsø. Early on in this work, Eken established a close collaboration with Ole Kiehn in Copenhagen. One major focus of their work was on plateau potential generation in motor neurons, and convincing evidence was obtained that such plateau potentials generated the long duration “tonic” impulse trains in the soleus just referred to. I was intrigued by seeing such trains go on and on while the rat was resting or asleep and making no movements. Obviously, they had nothing to do with motor control. Could they be engaged in temperature control? We have explored this possibility and found that the number and duration of tonic episodes increase progressively with decreasing ambient temperature from 26°C to 17°C (T. Eken, E. Bekkestad Rein, and T. Lømo, in preparation). Accordingly, we propose that this type of tonic activity in deep-lying, well-circulated muscles such as the soleus is generated by plateau potentials in motor neurons. The tonic activity serves to fine tune body temperature around its set point by producing heat that is transferred to the blood and distributed to the rest of the body. The control goes on at normal ambient temperatures well above those that cause shivering and is a novel mechanism for body temperature control not mentioned in textbooks.

The “size principle” for recruitment of motor neurons is well known. It describes the finding that motor units are recruited in a certain order during voluntary contractions of increasing intensity, small units being recruited before large motor units. Eken’s findings show that during the involuntary tonic contractions just described, the activity may switch from one unit to another in no apparent order. According to textbooks, two mechanisms participate in increasing the force output of muscle: motor unit recruitment and increased motor unit firing rates with force output increasing according to the tension-frequency relation. Our work (Hennig and Lømo, 1985, 1987) shows that there is a third mechanism based on the finding that the fastest units in extensor digitorum longus rarely fire more 1–6 pulses in brief bursts of activity. For such units in rats moving unrestrained in cages, the interval between successive impulses is constant and independent of the number of impulses in the burst. Most often there is only 1 impulse, less often 2, and so on. Consequently, there is a marked increase in force output for each additional impulse in the burst without any rate modulation. But, like many other findings, this one has disappeared from view and is never referred to, as far as I can tell.

Ectopic Neuromuscular Junction Formation: An Instructive Model

Formation of ectopic neuromuscular junctions has been a major experimental model of our lab. Fex and Thesleff (Life Sciences, 1967) introduced the model. They cut the deep fibular nerve and moved the proximal cut end onto an endplate-free region of the gastrocnemius. Two weeks later, they denervated the gastrocnemius by cutting the tibial nerve. After a further 2 weeks they stimulated the foreign transplanted nerve and observed strong contractions resulting from transmission at new ectopic neuromuscular junctions. The important stratagem here was to allow time, 2 weeks in this case, for the transplanted nerve to grow to the “starting line” for synapse formation, then to denervate the muscle by cutting the original nerve to induce receptivity to ectopic innervation with the result that new neuromuscular junctions began to form underneath the terminals of the regenerating transplanted nerve. Without denervation, no ectopic junctions appeared. With simultaneous transplantation and denervation, only a few ectopic junctions appeared in some animals.

We adopted this approach with the difference that we transplanted the foreign superficial fibular nerve onto the soleus muscle. Often, the number of ectopic junctions was impressive, covering all fibers in large parts of the muscle. At other times, ectopic innervation might fail altogether in batches of rats in certain periods and for unknown reasons. Our earlier failure to consistently induce LTP comes to mind (see earlier). Nevertheless, the model has proved very useful for studying basic features of neuromuscular junction formation. On superficial muscle fibers, ectopic synapse formation starts nearly synchronously 1–2 days after the denervation, proceeds over the next 1–2 weeks to fully formed and functional neuromuscular junctions, recapitulating all the essential steps in neuromuscular junction formation in the right sequence, including aggregation and stabilization of acetylcholine receptors underneath nerve terminals, appearance of acetylcholine esterase after a couple of days’ delay, folding of the postsynaptic membrane, and synapse elimination.

In 1975 Clarke Slater and his wife Helen and two young children came to Oslo for a year. Together, Clarke and I set out to study inflammation-induced supersensitivity to acetylcholine in muscle fibers with much effort but little success. We therefore switched to studying ectopic synapse formation, which turned into a productive (three papers in Journal of Physiology) and exciting enterprise full of lively discussions, much enthusiasm, and good companionship. A few years later, Johannes Skorpen took a year off from his medical studies to make a substantial contribution to our studies of ectopic synapse formation.

Here are some main results of our combined efforts using this model.

Blocking impulse conduction in the original nerve (rather than cutting it) allows ectopic synapse formation to occur, whereas direct muscle stimulation after cutting the original nerve prevents it. Therefore, receptivity to ectopic innervation is controlled by evoked muscle impulse activity.

Extensive reorganization of ectopic inputs on individual muscle fibers occurs as the junctions mature. Some sites develop into mature adult-type neuromuscular junctions (the winners), while multiple others disappear (the losers). The winners become spaced out, separated by ∼1.5 mm on average. Thus, a refractory zone appears around ectopic winners, like that observed on either side of the original endplate band where ectopic junctions never form closer than ∼0.75 mm, although foreign axons may “jump” this zone and innervate original endplates.

No such reorganization occurs if impulse conduction in the transplanted nerve is blocked or the transplanted nerve is cut early, but it does occur if the transplanted nerve is cut early and the muscle, in addition, is stimulated directly. Therefore, evoked muscle impulse activity causes the appearance of winners and refractory zones, and the elimination of losers.

If the foreign nerve is cut at the time of onset of synapse formation, subsequent discrete sites of acetylcholine esterase activity, representing mature endplates, will not appear. But if the muscle is stimulated directly after the cut, such sites appear just as they do with an intact nerve. Evidently, the cut nerve leaves a trace, or an imprint, in the muscle fiber, which will then persist and provide instructions for subsequent impulse activity-dependent processes setting up the postsynaptic apparatus, including the appearance of acetylcholine esterase.

In the presence of such a nerve-derived transient trace, stimulation-evoked muscle impulse activity causes the now denervated winners to attain a limited size, comparable to the size of normally innervated junctions. This limitation and the accompanying refractoriness suggest that impulse activity-dependent processes within the muscle fibers determine both the size and spacing of future neuromuscular junctions. Furthermore, such restriction in available “synaptic space” seems likely to affect competitive interactions between axons during periods of synapse elimination.

Individual soleus muscle fibers support from 1 (most common) to 5 ectopic neuromuscular junctions depending on the length of the region covered by transplanted axons. The “synaptic domain” of one winner, that is, the length of fiber required to “support” each one, would be about 1.5 mm (the winner + a refractory zone about 0.75 mm long on either side). These results may explain why normal muscle fibers (unless they are very long) end up with only one neuromuscular junction roughly in the middle of the fiber. In the embryo, axons form neuromuscular junctions when the muscle fibers are very short. Nerve evoked impulse activity occurs early, setting up refractory zones on either side of the initial site. Conducted impulse activity then makes the rest of the fiber refractory to innervation as the fibers grow in length by additions to either end, and the initial site ends up roughly in the middle.

Agrin at the Neuromuscular Junction

In 1993, with the experience of ectopic synapse formation behind me, I went to Jack McMahan at the Department of Neurobiology, Stanford University, for a sabbatical. In a series of important experiments Jack and his coworkers had discovered agrin and shown its essential role in the formation of neuromuscular junctions. Could agrin be responsible for the persistent “trace” that axons leave on the surface of muscle fibers when removed at an early stage of synapse formation (see earlier discussion)? To answer this question, Mendell Rimer, Ilana Cohen, and I started to inject neural agrin cDNA into denervated rat soleus muscles. The effect was impressive.

In some muscle fibers short segments began to express neural agrin, while clusters of mature acetylcholine receptors containing ε-subunits appeared on fibers immediatley surrounding these segments. Moreover, at the sites of such clusters, other components and structural features characteristic of the postsynaptic apparatus of normal neuromuscular junctions also appeared. Evidently, the injected cDNA had entered some muscle fibers where it caused local expression and release of neural agrin, which in turn induced the appearance of a mature postsynaptic-like apparatus on neighboring fibers. Similar results were obtained independently and at about the same time by Hans Brenner and his colleagues.

Back in Oslo, Iacob Mathiesen, a Ph.D. student in my lab joined the project and injected, as before, the cDNA into denervated soleus muscles. In addition, he stimulated the injected muscles directly. The results were strikingly similar to those observed during ectopic innervation. In the absence of stimulation, multiple clusters of acetylcholine receptors appeared along the length of fibers surrounding the agrin-expressing segments. In the presence of stimulation, all but one of these clusters disappeared (the losers), while the one that survived (the winner) acquired a size comparable to that of the original endplates in the same muscle. In addition, the winner displayed all the normal components of the postsynaptic apparatus that we looked for. Thus, the formation of ectopic neuromuscular junctions can be accounted for by the combined effects of neural agrin and evoked muscle impulse activity, normally secreted or evoked by motor nerve terminals. There is one exception. Since no nerves are present at agrin-induced acetylcholine receptor clusters, the distinct structural features that normally reflect overlying nerve terminal branches and swellings are missing.

I think these results answer the question raised earlier: Yes, agrin probably is responsible for the postsynaptic trace that nerve terminals leave after early removal, a trace that then provides instructions for further postsynaptic development. Other evidence, based on estimates of the number and stability of postjunctional acetylcholine receptors obtained in collaboration with Jacopo Andreose and Guido Fumagalli, suggests that the trace persists at least 2 months in the presence of stimulation-evoked muscle activity but disappears within 2 weeks in the absence of such stimulation.

Recently, there has been much interest in the possibility that during development muscle fibers are preprogrammed to display acetylcholine receptor clusters that determine where the first neuromuscular junctions will form. Certainly, for ectopic neuromuscular junction formation no such programming is needed. The new junctions form at random sites without the presence of any clusters before the nerve terminals “touch down” on the surface of muscle fibers. For this reason, I have earlier suggested that the appearance of acetylcholine receptor clusters in the middle of some muscles around the time of nerve arrival may be an epiphenomenon that is unnecessary for normal neuromuscular junction formation (Lømo, 2003).

Ectopic synapse formation is rarely used as an experimental model today. It does not normally occur and may therefore be seen as artificial. Nevertheless, ectopic synapse formation recapitulates all essential aspects of normal neuromuscular synapse formation and allows studies that are difficult or impossible to do in the embryo. I think the processes of ectopic synapses, as outlined earlier, throw light on important general principles of synapse formation.

Life at Stanford (1993–1994)

Anne and I enjoyed our stay at Stanford very much—the good life, the Sundays with coffee, newspapers, and books at Printers Ink in Palo Alto, the climate, the walks in nearby hills and from our apartment across the road to the department, and the extraordinary generous hospitality of Jack and Sandra McMahan in whose home I lived for more than 2 months in Anne’s absence. There I was introduced to molecular biology, working at the bench with Mendell Rimer next to me explaining and showing me how to do things. Thus, after nearly a year, I felt that I was on speaking terms with molecular biologists, if only barely. Before Stanford we had been without a car for 16 years. We thought we could do likewise at Stanford but quickly experienced its absolute inconvenience. So from a neighbor we bought a sleek bottle green 1979 two-door Cadillac Eldorado with brown leather seats and a rather cozy backseat, which very soon required very expensive repairs. After that, it served us wonderfully. In fact, we liked it so much that I contacted authorities in Norway to learn that it would cost us ∼$24,000 in customs duty alone to bring it to Norway. In the end, the day before leaving the United States, we drove down El Camino Road to a park-and-sell place where we paid the guy $100 to sell it for us at some unspecified later date. And after about half a year we received $1800 for the car.

Setting up a Biotech Company

Injection of cDNA into muscles for transformation of muscle fibers was very inefficient. To improve the efficiency, Iacob Mathiesen began to stimulate the muscle with brief, high-frequency, and high-voltage electrical pulses immediately after the injection. This procedure, called electroporation, increased the efficiency substantially. He then did a systematic study of stimulus parameters to optimize the procedure and initiated a collaborative project with a Merck subsidiary in Rome, Italy. This resulted in the demonstration of dramatic and long-lasting expression of erythropoetin in muscle after intramuscular injection of its cDNA, an effect that could be attributed mainly to the electroporation. The two of us then applied for and obtained a U.S. patent for the method of electroporation that Iacob had used. With money from venture investors and licenses sold, Iacob set up a company, Inovio, with me as a partner, which was later sold to a company in the United States taking the name of Inovio Biomedical Corporation. The entire enterprise was the result of Iacob’s ideas and efforts. For me, watching from the sideline how it developed, it was a totally unexpected and exhilarating experience. I even gained some money so that Anne and I now buy more books, subscribe to more newspapers and periodicals than we will ever have time to read, and travel more often and more comfortably than we would otherwise have done. I have invested in powerful machinery in my carpentry shop in our basement and I have already had plastic surgery on one badly injured finger to show for it. Our needs have always been quite modest, and I am sure we would have been just as fine without the extra money and some shares in the new company by now much reduced in value.

Back to Oslo

Returning from Stanford in the summer of 1994 with ideas for new projects that combined my experience with chronic experiments on live animals with my newly acquired experience of techniques in molecular biology, I joined others in applying for larger and more ambitious grants from the European Union and the Norwegian Research Council. Some of the projects built on already established collaborations with labs in Europe, others on new ones, most of them fruitful. Instead of having a Ph.D. student or two in the lab, I now had several such students and two or three postdocs. In general, I found these projects productive and enjoyable but also stressful with meetings, deadlines, and reports coming up all the time. Among many results from these efforts, here is one set of results that I find particularly interesting and that owes much to Gabriela Bezakova, a postdoc in the lab who did most of the work.

Examining muscle fibers with agrin-induced acetylcholine receptor clusters outside the endplate, Gabriela noticed that the clusters consisted of smaller aggregates that lined up along transverse stripes in electrically active fibers and along longitudinal stripes in denervated or electrically inactive fibers. Further work revealed that the transverse stripes overlapped with costameres, a chain of proteins made up of α-dystroglycan on the outside, β-dystroglycan in the sarcolemma, and underneath the sarcolemma, dystrophin, F-actin, and α-actinin connecting to the Z-disks of each sarcomere. After denervation, all these proteins changed organization and appeared instead along longitudinal stripes. During direct muscle stimulation, they then returned to their normal transverse orientation. Similar changes were seen at endplates where acetylcholine receptor clusters underwent comparable reorientations, as expected if they were firmly attached to underlying cytoskeletal proteins. Importantly, in denervated muscles, muscle agrin induced a similar restoration of the normal transverse orientation when applied to the muscle surface in very low concentrations. Unlike neural agrin, muscle agrin does not cluster acetylcholine receptor on the surface of muscle fibers because it lacks eight amino acids required for such clustering, and its function was a mystery. Muscle agrin was known to be secreted by muscle fibers and to bind to α-dystroglycan on the outside. Moreover, the chains of costameric proteins, positioned at Z-lines along the entire length of muscle fibers, transmit forces generated by each sarcomere to the extracellular matrix. With this background we proposed a function for muscle agrin. Outside the endplate, muscle activity (and/or accompanying mechanical stresses) controls the expression (and/or processing) of muscle agrin. After secretion, muscle agrin binds to α-dystroglycan and acts back in an autocrine way to adjust the cytoskeleton in accordance with the mechanical demands posed by the activity. At the endplate, muscle agrin similarly assists in stabilizing the postsynaptic apparatus. These and other results from that work were published in Journal of Cell Biology (2001) and Proceedings of the National Academy of Sciences (2001). I felt that our results demonstrating such dramatic effects of muscle impulse activity and muscle agrin on the organization of the cytoskeleton of muscle fibers were novel and important. I have therefore been surprised to see that at least so far they have not made much of an impact. Perhaps their time will come.

Resurrecting the Lamellar Hypothesis

Finding the unpublished manuscripts that I had submitted to Experimental Brain Research 40 years ago, I immersed myself in the literature of the intervening years, wrote a new manuscript based on the old experiments and figures, and saw it published in Hippocampus in 2009. Two conclusions stood out.

The perforant path input to and the mossy fiber output from the dentate gyrus were both organized according to the lamellar hypothesis.

Marked inhibition spread for several millimeters along the septo-temporal axis of the dentate gyrus following the discharge of granule cells along a narrow transverse strip of the dentate gyrus. Orthodromic activation by perforant path fibers or antidromic activation by mossy fibers produced comparable inhibition, indicating that the inhibition was primarily recurrent.

The lamellar hypothesis fell into disfavor after an influential review of anatomical data by Amaral and Witter (Neuroscience, 1989), and it is not discussed in the recent The Hippocampus Book (2006). In their review, Amaral and Witter write: “The overwhelming consensus in all these studies is that aside from the mossy fibers, none of the intrinsic connections of the hippocampal formation is organized in a lamellar fashion. Quite the opposite organization seems to be true.” They pointed to findings showing that extracellular injections of tracers into small regions of the entorhinal cortex labeled perforant path fibers along “substantial portion of the long axis of the dentate gyrus.” Conversely, small injections into the dentate gyrus labeled “cells in a long, rostrocaudally oriented zone of the EC.” Therefore, they write: “it is clear that the fibers that cross the hippocampal fissure to enter the dentate area are collaterals of axons that contribute a far more widespread pattern of termination within the dentate gyrus.” And they conclude, surely correctly, that a point source in the entorhinal cortex cannot activate a lamella of hippocampal tissue, as argued by Andersen, Bliss, and Skrede (1971). But the idea of widespread collaterals of a single axon required an explanation of my conclusion (Lømo, 1971), which they cite: “Provided the stimulating electrode was located close to the hippocampal fissure where the perforant path enters the dentate area, it was consistently found that the incoming perforant fibers divide the dentate area into a series of parallel segments.” The explanation they suggest is that “these collaterals terminate with lower density at progressively greater distances from the stimulation point, the synaptic effect on distant granule cells may be insufficient to generated sufficiently synchronous activation to produce detectable populations spikes.”

There are two arguments against this view.

The perforant path-evoked field EPSP drops rapidly just outside the strip of activated granule cells, as my contour plots showed. And even if some collaterals spread further and affect distant points only weakly, the much greater efficiency centrally may well turn the dentate gyrus into a series of functional lamellae. I see such lamellae not as well-demarcated anatomical lamellae but as narrow strips of discharging cells, one strip flowing into others, shifting positions as events unfold, and interacting by longitudinal connections and accompanying excitability changes. Such functional lamellae would be much narrower than any anatomical lamella encompassing the entire terminal field of a perforant path axon.

The entorhinal cortex may be organized in a modular manner, and there is supporting anatomical data, much like the situation in primary sensory cortical areas where information from large visual, somatosensory, or auditory fields is split for similar processing in a mosaic of columns. This suggests a model where one cell with a particular set of properties in one module projects to one transverse lamella, and other cells with the same set of properties in other modules project to that same lamella. Similarly, any other lamella receives inputs from cells in many modules having another set of similar properties. Such a model is consistent with the anatomical data reviewed by Amaral and Witter (1989) and with other more recent anatomical and physiological data.

I presented this model at the Spring Hippocampal Research Conference in Verona, Italy, in 2009. In the discussion after the session, one of the participants made the following comment: “There is no evidence supporting the lamellar hypothesis, and trying to resurrect it is like trying to beat a dead horse back to life.” This to me appears close minded. The lamellar hypothesis as presented earlier may be wrong, of course, but is not impossible, and to me seems the more plausible. Anyway, we have now started experiments to test it. Tim Bliss will come to Oslo to participate in some of the experiments, an unexpected and wonderful opportunity to take up again a collaboration that was so enjoyable and rewarding 40 years ago. It seems important to try to find out which of the two models referred to earlier is the more correct since it must strongly influence how one will understand and model dentate gyrus function in the future. Today, so-called pattern separation appears to be an important function of the dentate gyrus, a process of splitting the information from the entorhinal cortex to the dentate gyrus before it is sent forward for pattern completion in CA3. While my understanding of pattern separation may well be incomplete, it seems to me that the concept is better served by perforant path fibers targeting a series of lamellae in the dentate gyrus than by extensive longitudinally running axon collaterals spreading the same information along the entire dorsal dentate gyrus.

Concluding Remarks

In summing up I am struck by how lucky I have been, having lived and nearly completed a life in a peaceful corner of the world in good health, in a happy marriage of almost 50 years, with three sons with successful careers who have given their parents nothing but pleasure, and with grandchildren, all of whom appear set for normal and fulfilling lives. One goes through different epochs in life, each epoch requiring different approaches and efforts for a good outcome. Marriage, family, and work are especially important. To my continual amazement, somehow and largely unplanned, I have managed to land on my feet. Perhaps surprisingly, life in retirement has turned out particularly rewarding with access to a part of what was my own lab, now under the control of the younger professor and good collaborator Arild Njå, ready for interesting experiments with my own hands, as in the old days when I did my own experiments in the lab.

The move away from the lab that came with advancement in age and position I found problematic. It was in the lab that I made my discoveries, doing experiments sometimes over and over again to convince myself that they were reproducible, to allow time for separating the significant from the noise, and for seeing new and interesting patterns emerge. One of the reviewers of my paper in Hippocampus commented: “I think it might be worth adding something here [to my claim that the figures shown were representative], for there may have been a change in etiquette over the years. Does ‘representative’ mean just that, or are these the experiments that ‘worked’? This was my answer:

An interesting question. The more correct answer is probably “representative of the experiments that worked.” But this phrasing may leave an impression of undue selection of results, which I hope was not the case. Over those 3–4 years many experiments were ignored for different reasons. Some early ones were ignored because I could not make sense of them. It took time to reasonably master the technical procedures, to obtain reproducible results under particular experimental conditions, and to get a grasp of what was happening on the oscilloscope screen in front of me. Others were ignored for merely technical reasons. Still others were ignored because they were part of an exercise in trial and error, looking for phenomena that did not materialize, make sense, or were not reproducible (or they did catch my eye and made grounds for a different paper, for example Bliss & Lømo, 1973). The present paper is not the outcome of experiments to test well-conceived, preformed ideas but rather a synthesis of an understanding based on many different experiments, slowly arrived at by asking many different questions over a relatively long period of time, with certain parts selected to make a coherent whole for this particular paper. With this approach it is critical, I think, to do the experiments often enough to become convinced that they are reproducible and thus ‘true’ under the conditions described. I believe and hope that that was so in this case.

My work has pleased me the most when the results spoke for themselves and the use of statistics was unnecessary. I have never felt comfortable with statistics and the conventions behind them. At a 5% significance level the result might be spurious anyway and often of marginal importance.

So in doing research, what has been rewarding for me? I think the process of finding out more than the result itself. Is LTP an essential process for learning and memory? Probably. But if it is, other processes, most of them perhaps still unknown, are likely also to be essential. Once we know, the fun is over. The excitement is in the uncertainty and in trying to find the right answers. Finding out about learning and memory involves problems of mechanism and are therefore probably soluble. Harder questions relate to consciousness. Will we ever know? To me it is no less and no more than shifting patterns of activity in the networks of my brain. When that activity stops, it is all over. Why such activity gives me self-awareness and subjective feelings I don’t know. And I will never know. The problem seems insoluble and therefore I am not particularly interested. For others the question obviously is not as simple as that. There will always be people who believe in religious or other forces affecting us from outside in mysterious ways. That may or may not be real. If it is unreal, as I believe it is, then the fact that the unreal is so real to many people is a paradoxical aspect of reality. Similarly, the fact that there is so much irrationality in the world, people believing in the unreal, is also part of our reality. Consequently, the prospects for a rational world appear bleak, even as we find out ever more about the workings of the brain and reach for an understanding of the nature of consciousness.

Acknowledgements

I thank Tim Bliss, Clarke Slater, Alberto Cangiano, and Jean Rosenthal for reading the whole or parts of a draft for this chapter and for their valuable comments.

Selected Bibliography

Lømo T, Mollica A. Activity of single units in primary optic cortex of the unanaesthetized rabbit during visual, auditory, olfactory and painful stimulation. Arch Ital Biol 1962;100:86–120.

Andersen P, Andersson SA, Lømo T. Patterns of spontaneous rythmic activity within various thalamic nuclei. Nature 1966;211:888–889.

Andersen P, Blackstad TW, Lømo T. Location and identification of excitatory synapses on hippocampal pyramidal cells. Exp Brain Res 1966;1:236–248.

Lømo T. Frequency potentiation of excitatory synaptic activity in the dentate area of the hippocampal formation. Acta Physiol Scand 1966;68(Suppl 277):128.

Andersen P, Andersson SA, Lømo T. Some factors involved in the thalamic control of spontaneous barbiturate spindles. J Physiol 1967;192:257–281.

Andersen P, Andersson SA, Lømo T. Nature of thalamo-cortical relations during spontaneous barbiturate spindle activity. J Physiol 1967;192:283–307.

Lømo T. Patterns of activation in a monosynaptic cortical pathway: the perforant path input to the dentate area of the hippocampal formation. Exp Brain Res 1971;2:18–45.

Lømo T. Potentiation of monosynaptic EPSPs in the perforant path dentate granule cell synapse. Exp Brain Res 1971;12:46–63.

Lømo T, Rosenthal J. Control of ACh sensitivity by muscle activity in the rat. J Physiol 1972;221:493–513.

Bliss T, Gardner MA, Lømo T. Synaptic plasticity in the hippocampal formation. London: MacMillan, 1973; 93–203.

Bliss T, Lømo T. Long-lasting potentiation of synaptic transmission in the dentate area of the anaesthetized rabbit following stimulation of the perforant path. J Physiol 1973;232:331–356.

Frank E, Jansen J, Lømo T, Westgaard RH. Maintained function of foreign synapses on hyperinnervated skeletal muscle fibres of the rat. Nature 1974;247: 375–376.

Lømo T. Neurotrophic control of colchicine effects on muscle? Nature 1974;249: 473–474.

Lømo T, Westgaard RH, Dahl HA. Contractile properties of muscle: control by pattern of muscle activity in the rat. Proc Roy Soc Lond, Ser B 1974;187:99–103.

Frank E, Jansen JK, Lømo T, Westgaard RH. The interaction between foreign and original motor nerves innervating the soleus muscle of rats. J Physiol 1975; 247:725–743.

Lømo T, Westgaard RH. Further studies on the control of ACh sensitivity by muscle activity in the rat. J Physiol 1975;252:603–626.

Lømo T, Westgaard RH. Control of ACh sensitivity in rat muscle fibers. Cold Spring Harbor Symposia on Quantitative Biolology 1976;XL:263–274.

Lømo T, Slater CR. Control of acetylcholine sensitivity and synapse formation by muscle activity. J Physiol 1978;275:391–402.

Cangiano A, Lømo T, Lutzemberger L, Sveen O. Effects of chronic nerve conduction block on formation of neuromuscular junctions and junctional AChE in rat. Acta Physiol Scand 1980;109:253–296.

Lømo T. What controls the development of neuromuscular junctions? Trends Neurosci 1980;3:126–129.

Lømo T, Slater CR. Control of junctional acetylcholinesterase by neural and muscular influences in the rat. J Physiol 1980;303:191–202.

Lømo T, Slater CR. Acetylcholine sensitivity of developing ectopic nerve-muscle junctions in adult rat soleus muscles. J Physiol 1980;303:173–189.

Hennig R, Lømo T. Firing patterns of motor units in normal rats. Nature 1985;14: 164–166.

Lømo T, Massoulié J, Vigny M. Stimulation of denervated rat soleus muscle with fast and slow activity patterns induces expression of acetylcholinesterase molecular forms. J Neurosci 1985;5:1180–1187.

Lømo T, Wærhaug O. Motor endplates in fast and slow muscles of the rat: what determines their differences? J Physiol (Paris) 1985;80:290–297.

Brenner HR, Lømo T, Williamson R. Control of end-plate channel properties by neurotrophic effects and by muscle activity in rat. J Physiol 1987;388:367–381.

Hennig R, Lømo T. Effects of chronic stimulation on the size and speed of long-term denervated and innervated rat fast and slow muscles. Acta Physiol Scand 1987;30:115–131.

Hennig R, Lømo T. Gradation of force output in normal fast and slow muscles of the rat. Acta Physiol Scand 1987;130:133–142.

Lømo T. Formation of ectopic neuromuscular junctions: role of activity and other factors. In: The Neural and Molecular Bases of Learning (Changeux J-P, Konishi M, eds). New York: John Wiley & Sons Ltd. 1987; 359–374.

Gorza L, Gundersen K, Lømo T, Schiaffino S, Westgaard RH. Slow-to-fast transformation of denervated soleus muscles by chronic high-frequency stimulation in the rat. J Physiol 1988;402:627–649.

Lømo T, Gundersen K. Trophic control of skeletal muscle membrane properties. In: Nerve-Muscle Cell Trophic Communication (Fernandez HL, ed). Boca Raton: CRC Press, Inc. 1988; 61–79.

Lømo T, Pockett S, Sommerschild H. Control of number and distribution of synapses during ectopic synapse formation in adult rat soleus muscles. Neurosci 1988;24:673–686.

Schiaffino S, Ausoni S, Gorza L, Saggin L, Gundersen K, Lømo T. Myosin heavy chain isoforms and velocity of shortening of type 2 skeletal muscle fibres. Acta Physiol Scand 1988;134:575–576.

Westgaard RH, Lømo T. Control of contractile properties within adaptive ranges by patterns of impulse activity in the rat. J Neurosci 1988;8:4415–4426.

Schiaffino S, Gorza L, Sartore S, Saggin L, Ausoni S, Vianello M, Gundersen K, Lømo T. Three myosin heavy chain isoforms in type 2 skeletal muscle fibres. J Muscle Res Cell Mot 1989;10:197–205.

Ausoni S, Gorza L, Schiaffino S, Gundersen K, Lømo T. Expression of myosin heavy chain isoforms in stimulated fast and slow rat muscles. J Neurosci 1990; 10:153–160.

Fumagalli G, Balbi S, Cangiano A, Lømo T. Regulation of turnover and number of acetylcholine receptors at neuromuscular junctions. Neuron 1990;4:563–569.

Andreose J, Xu R, Lømo T, Salpeter MM, Fumagalli G. Degradation of two AChR populations at rat neuromuscular junctions: regulation by electrical stimulation. J Neurosci 1993;13:3433–3438.

Wærhaug O, Lømo T. Factors causing different properties at neuromuscular junctions in fast and slow rat skeletal muscles. Anat Embryol 1994;190:113–125.

Andreose JS, Fumagalli G, Lømo T. Number of junctional acetylcholine receptors: control by neural and muscular influences in the rat. J Physiol 1995;483: 397–406.

Cohen I, Rimer M, Lømo T, McMahan UJ. Agrin-induced postsynaptic-like apparatus in skeletal muscle fibers in vivo. Mol Cell Neurosci 1997;9:237–253.

Mathiesen I, Rimer M, Ashtari O, Cohen I, McMahan UJ, Lømo T. Regulation of the size and distribution of agrin-induced postsynaptic-like apparatus in adult skeletal muscle by electrical muscle activity. Mol Cell Neurosci 1999;13: 207–217.

Rimer M, Mathiesen I, Lømo T, McMahan UJ. γ-AChR/ε-AChR Switch at agrin-induced postsynaptic-like apparatus in skeletal muscle. Mol Cell Neurosci 1997;9:254–263.

Rimer M, Cohen I, Lømo T, Burden SJ, McMahan UJ. Neuregulins and erbB receptors at neuromuscular junctions and at agrininduced postsynaptic-like apparatus in skeletal muscle. Mol Cell Neurosci 1998;12:1–15.

Sala C, Andreose JS, Fumagalli G, Lømo T. Calcitonin gene-related peptide: possible role in formation and maintenance of neuromuscular junctions. J Neurosci 1995;15:520–528.

Windisch A, Gundersen K, Szabolcs MJ, Gruber H, Lømo T. Fast to slow transformation of denervated and electrically stimulated rat muscle. J Physiol 1998;510:623–632.

Skorpen J, Lafond-Benestad S, Lømo T. Regulation of the size and distribution of ectopic neuromuscular junctions in adult skeletal muscle by nerve-derived trophic factor and electrical muscle activity. Mol Cell Neurosci 1999;13: 192–206.

Vult von Steyern F, Martinov V, Rabben I, Njå A, deLapeyrière O, Lømo T. The homeodomain transcription factors Islet 1 and HB9 are expressed in adult alpha and gamma motoneurons identified by selective retrograde tracing. Eur J Neurosci 1999;11:2093–2102.

Murgia M, Serrano AL, Calabria E, Pallafacchina G, Lømo T, Schiaffino S. Ras is involved in nerve-activity-dependent regulation of muscle genes. Nat Cell Biol 2000;2:142–147.

Awad SS, Lightowlers RN, Young C, Chrzanowska-Lightowlers ZMA, Lømo T, Slater CR. Sodium channel mRNAs at the neuromuscular junction: distinct patterns of accumulation and effects of muscle activity. J Neurosci 2001;21: 8456–8463.

Bezakova G, Helm JP, Francolini M, Lømo T. Effects of purified recombinant neural and muscle agrin on skeletal muscle fibers in vivo. J Cell Biol 2001;153: 1441–1452.

Bezakova G, Lømo T. Muscle activity and muscle agrin regulate the organization of cytoskeletal proteins and attached AChRs aggregates in skeletal muscle fibers. J Cell Biol 2001;153:1453–1463.

Bezakova G, Rabben I, Sefland I, Fumagalli G, Lømo. The neural agrin controls acetylcholine receptor stability in skeletal muscle fibers. Proc Nat Acad Sci USA 2001;98:9924–9929.

Martinov VN, Sefland I, Walaas SI, Lømo T, Nja A, Hoover F. Targeting functional subtypes of spinal motoneurons and skeletal muscle fibers in vivo by intramuscular injection of adenoviral and adeno-associated viral vectors. Anat Embryol 2002;205:215–221.

Ralston E, Ploug T, Kalhovde J, Lømo T. Golgi complex, endoplasmic reticulum exit sites, and microtubules in skeletal muscle fibers are organized by patterned activity. J Neurosci 2001;21:875–883.

Serrano AL, Murgia M, Pallafacchina G, Calabria E, Coniglio P, Lømo T, Schiaffino S. Calcineurin controls nerve activity-dependent specification of slow skeletal muscle fibers but not muscle growth. Proc Nat Acad Sci USA 2001;98: 13108–13113.

Lømo T. Nerve-muscle interactions. In: Handbook of Clinical Neurophysiology: Clinical Neurophysiology of Disorders of Muscle and Neuromuscular Junction, Including Fatigue (Stålberg E, ed). Elsevier Science B. V. 2003; 47–66.

Lømo T. What controls the position, number, size, and distribution of neuromuscular junctions on rat muscle fibers? J Neurocytol 2003;32:835–848.

Lømo T. The discovery of long-term potentiation. Philos Trans R Soc Lond B Biol Sci 2003;358:617–620.

Reid B, Martinov VN, Njå A, Lømo T & Bewick GS. Activity-dependent plasticity of transmitter release from nerve terminals in rat fast and slow muscles. J Neurosci 2003;23:9340–9348.

McCullagh KJ, Calabria E, Pallafacchina G, Ciciliot S, Serrano AL, Argentini C, Kalhovde JM, Lømo T, Schiaffino S. NFAT is a nerve activity sensor in skeletal muscle and controls activity-dependent myosin switching. Proc Natl Acad Sci USA 2004;101:10590–10595.

Grønevik E, Mathiesen I, Lømo T. Early events of electroporation-mediated intramuscular DNA vaccination potentiate Th1-directed immune responses. J Gene Med 2005;7:1246–1254.

Kalhovde JM, Jerkovic R, Sefland I, Cordonnier C, Calabria E, Schiaffino S, Lømo T. “Fast” and “slow” muscle fibres in hindlimb muscles of adult rats regenerate from intrinsically different satellite cells. J Physiol 2005;562:847–857.

Vult von Steyern F, Lømo T. Postnatal appearance of 5-HT2A receptors on fast flexor and slow extensor rat motor neurons. Neuroscience 2005;136:87–93.

Eken T, Elder GC, Lømo T. Development of tonic firing behavior in rat soleus muscle. J Neurophysiol 2008;99:1899–1905.

Lømo T. Excitability changes within transverse lamellae of dentate granule cells and their longitudinal spread following orthodromic or antidromic activation. Hippocampus 2008;19:633–648.

Lømo, T. Modulation of the Muscle Fiber and the Neuromuscular Junction by Activity. In: New Encyclopedia of Neuroscience (Squire LR, ed). New York: Elsevier 2009; xx–xx.

Michael M. Merzenich

BORN:

Lebanon, Oregon

May 15, 1942

EDUCATION:

Public Schools, Lebanon, Oregon (1924–1935)

University of Portland (Oregon), B.S. (1965)

Johns Hopkins University, Ph.D. (1968)

University of Wisconsin Postdoctoral Fellow (1968–1971)

APPOINTMENTS:

Assistant and Associate Professor, University of California at San Francisco (1971–1980)

Francis A. Sooy Professor, University of California at San Francisco (1981–2008)

President and CEO, Scientific Learning Corporation (1995–1996)

Chief Scientific Officer, Scientific Learning Corporation (1996–2003)

Chief Scientific Officer, Posit Science Corporation (2004–present)

President and CEO, Brain Plasticity Institute (2008–present)

HONORS AND AWARDS (SELECTED):

Cortical Discoverer Prize, Cajal Club (1994)

IPSEN Prize (Paris, 1997)

Zotterman Prize (Stockholm, 1998)

Craik Prize (Cambridge, 1998)

National Academy of Sciences, U.S.A. (1999)

Lashley Award, American Philosophical Society (1999)

Thomas Edison Prize (Menlo Park, NJ, 2000)

American Psychological Society Distinguished Scientific Contribution Award (2001)

Zülch Prize, Max-Planck Society (2002)

Genius Award, Cure Autism Now (2002)

Purkinje Medal, Czech Academy (2003)

Neurotechnologist of the Year (2006)

Institute of Medicine (2008)

Michael M. Merzenich has conducted studies defining the functional organization of the auditory and somatosensory nervous systems. Initial models of a commercially successful cochlear implant (now distributed by Boston Scientific) were developed in his laboratory. Seminal research on cortical plasticity conducted in his laboratory contributed to our current understanding of the phenomenology of brain plasticity across the human lifetime. Merzenich extended this research into the commercial world by co-founding three brain plasticity-based therapeutic software companies (Scientific Learning, Posit Science, and Brain Plasticity Institute). Those companies have developed and validated neuroscience-based, computer-delivered rehabilitation training programs that have now been applied (by 2010) to more than 4 million impaired children and adults. Their research and treatment targets include developmental impairments that limit the cognitive, reading, and mathematical abilities of school-aged children; perceptual and cognitive impairments in normal aging; preventing and treating schizophrenia, bipolar disorder, depression, and other psychiatric diseases; rehabilitation strategies applied to treat traumatic brain injury and stroke; and the treatment of cognitive impairments arising from brain infections, toxin exposures, hypoxic episodes, and other environmental causes.

Michael M. Merzenich

I grew up in a German American family in a small farming and lumbering community in western Oregon. My father was a foreman in the primary industry in our town, a large plywood mill. My mother was dedicated to taking care of six rambunctious children and the gardens and livestock that supported a small-town/country life. My fundamental education as a young boy was enriched by a love of reading and by a wonderful family that, while largely self-educated, had mastered the practical arts of mechanics, engineering, and building, and took great pride in their practical good works. My mother and father were also masters of the art of Western hospitality, and our home was the gathering point for innumerable large and small celebrations with neighbors and kin. Everyone who came down our country lane was welcome to stay for supper!

My childhood at the edge of town provided the fields, forests, creeks, and mountains that became a play yard and a natural habitat for a natural game-playing and nature-loving child. Although we were expected to work to contribute to the family welfare at home, and worked from a young age as laborers on the fruit and vegetable farms in our community, my siblings and I were also granted a great deal of personal freedom throughout our childhood. That childhood combined strong lessons about personal responsibility and self-development, enriched by a goodly number of self-reliant and effective adult models.

Most important among these youthful influences were my maternal and paternal grandfathers Alois Hassler and William (Wilhelm) Merzenich. Both men operated with high professional standards; both were exemplary “self-made men.” Both were at once stern and demanding, always gave a boy a chance to prove himself, and always showed just a small glimmer of approval (never backed up by more than three or four words) when it mattered most. Because my Grandfather Merzenich lived near our own home, I saw him often, and he had a strong influence in shaping my own youthful interests. Emigrating from Germany to the United States at the age of 9, his formal education ended upon his arrival because he worked from that time forward to contribute to his own struggling family’s support. At the same time, he was one of the most broadly educated individuals that I have met in life—and certainly one of the most intelligent and interesting chaps a young lad could follow around. All that he knew he had learned through disciplined self-study and as an apprentice and on the job. Grandpa supported his family for most of his life as an architect and building contractor. During World War II, he was first a government building inspector, then an “engineer of the ways” at a shipyard. William Merzenich was justifiably proud of the buildings that he designed and constructed in our part of the United States (including about 20 Oregon churches). He was also very proud of his several

U.S. patents, the most important of which described the pneumatization of heavy shipyard equipment (drills, riveters), greatly increasing production speeds and cutting labor costs in wartime factories.¹ In the same way, my mother’s father and his wonderful bachelor son (my uncle Edward) understood that science provided the basis for better agricultural practices. No citizens were a better audience for the latest agricultural college knowhow applied to the farm than Alois and Edward Hassler.

I was drawn to an interest in the great questions of philosophy and psychology, and to a practical engineering and scientific approach to understanding and discovering the truths in life from these childhood experiences. I also learned from my kin that every individual had an obligation of service, and that the most important works were those that benefited others. Training as an engineering-oriented scientist coupled with an interest in religion and philosophy (a young lad’s way of framing an interest in the study of “the meaning of life”) were natural outcomes of this upbringing. With a scholarship in hand provided by our local community that supported my college expenses, I matriculated at and graduated with highest honors with a degree in General Science from the University of Portland in Oregon. I chose this major because it gave me the greatest flexibility in choosing courses in mathematics, and in physical and biological science.

As a University student, I developed a close friendship with (soon-to-be Dr.) Robert Prusch, who had practical electronics knowledge acquired as a technician in the U.S. Navy. Bob Prusch and I shared a wonderful instructor in Physiology, Dr. Blondell Carlton, who liked our idea of initiating a recording experiment in worm and insect nervous systems. An alumnus of our University was a co-founding engineer of Tektronics, Inc., one of the world’s leading medical instrumentation companies. He had donated a truckload of state-of-the-art electrophysiological recording equipment to our University laboratories. Bob Prusch and I opened the appropriate boxes, read the equipment user manuals, and set about recording action potentials from creatures that we caught in the lawn and nearby swamp! Puzzled about how to interpret our unit response recordings, I made an uninvited call to the Physiology Department at the Oregon Health Sciences Center asking for help. That call soon led me to the office of Dr. John Brookhart, a kindly, thoughtful, dignified man who almost immediately took me under his wing. I was stimulated by conversations with Professor Brookhart and his neurophysiology faculty colleagues Archie Tunturi and Alden Spencer. I explained to Brookhart that I had determined to dedicate my life’s work to the neurological study of the origins of behavior and the conscious self, using a neurophysiological approach to address “the great issues of philosophy.” In my juvenile mind, I thought of this career choice as the study of “experimental philosophy.” Little did I know at the time that this distinguished gentlemanly professor whom I had adopted as an adviser was the President of the American Physiological Society and the Editor-in-Chief of the Journal of Neurophysiology, then the preeminent neuroscience journal! Brookhart told me that neurophysiology had not yet gotten off to much of a start in studying my issues. I asked him where I should go to study them. He said, “Mike, you should go to Harvard to study with David Hubel or Elwood Henneman, or to Johns Hopkins, to study with Vernon Mountcastle or Philip Bard. Or you can come here.” I have no doubt that he spoke up for admission for this ill-formed country boy at these Eastern institutions, because I was accepted by both immediately upon application.

Neurophysiology (“Applied Philosophy” Level 0.1) Training

I was educated as a “real physiologist” at Johns Hopkins, which has advantaged my approach to neuroscience ever since. The same integrity and commitment to hard work, and the same respect for learning that marked my family’s approach to life, were richly exemplified by my professor, Vernon Mountcastle. Professor Mountcastle read more and wrestled with the complex logic of his data and subdiscipline with greater discipline and intensity than anyone you know. He worked continually to shape strong conclusions from scientific fact—while never extending his verbal or written commentary beyond those facts in hand. I learned the importance of creating and continuously revisiting a grand logical construct related to neurophysiological science from this wonderful, intense, completely dedicated individual.

At the same time, from my own background arguing with a man of equal intelligence (my Grandfather Merzenich), I knew that you could extend your view and dare to use your brain, à la Descartes as your primary scientific instrument, to extend your logical constructs beyond your data—but only if you always kept the boundary between “what you really know” and “what logic tells you that you know” in clear sight. At issue is the degree of aggressiveness with which a scientist might attempt to succeed in achieving the greatest aim in science: advancing the boundary of the known. One might say that my approach to science has always been just a little contaminated by a logical extension of “the facts” through the more introspective approach of a philosopher or psychologist.

I completed two studies as a graduate student, one published, the other not. For my thesis, I demonstrated correlates between parametrically documented tactile percepts and the firing characteristics of receptors innervating the glabrous skin of the hand dorsum and the hairy skin of the arm. These rather mundane studies showed that specific receptor classes must account for specific cutaneous perceptual phenomena (vibratory detection; stimulus magnitude). I also found, interestingly, that several classes of cutaneous receptors did not contribute to tactile perception, and I discovered to my great delight that the great 19th-century professor Friedrich Merkel had long before claimed that cutaneous touch domes were insensate spots on the skin, a fact that he had confirmed on the belly skin of fair-haired German boys! While these studies were methodologically routine, they did introduce me to an experimental strategy that I would repeatedly apply over the next decade: studies of human perception or cognition, directly paralleled by studies of primate or rodent behavior and neurology, achieved using the same psychophysical measures and/or training paradigms.

In a second, more inventive study, I demonstrated that responses in cortical field S1 evoked by vibratory stimuli in an adult monkey increased in amplitude to asymptote in the local neuronal population at a low stimulus level, while the growth of perceptual magnitude continued to grow across a far-broader intensive range. I concluded that the perceptual growth of perceived magnitude could only be accounted for by unit or local field potential activity in S1 by the spread of activity from the initially engaged “column” out across the horizontal cortical network. Mountcastle did not like this outcome, perhaps because (I think) he interpreted it as challenging the cortical column theory. He discouraged completion and publication, even while he was clearly very interested in this result. Several years later, Professor Kenneth Johnson (my favorite Johns Hopkins doctoral student compatriot) repeated this study with greater elegance and control, and came to the same general conclusion.

I was frustrated by my Johns Hopkins experience by the gulf between these kinds of elementary “information coding” experiments and any neurological understanding of “higher brain function.” I did not agree with the operational Mountcastelian view (which Mountcastle himself cautiously abandoned a few years later) that any real understanding of complex (real) neurology was dependent upon a complete understanding of its more fundamental subforebrain coding precedents. Upon a review of the literature, I determined, perhaps foolishly, that the auditory system had important advantages for pursuing my more behaviorally expansive interests. The young reader might be interested to know that in making this decision in 1967, I read every published report from the beginning of time related to the anatomy and physiology of the auditory system—just as I had read (insofar as I could determine) every paper ever published about cutaneous receptors and tactile sensation in conducting my doctoral thesis work. In both cases, a large proportion of these studies were written in German or French. These few decades later, no students at the same stage of their career development could begin to read all of the published literature related to their thesis project or to the subdiscipline of neuroscience that they might choose to pursue as a postdoctoral fellow.

In choosing to shift my attention to auditory neuroscience, most attractively, there were well-developed perceptual and cognitive subdisciplines (psychoacoustics, phonetics, linguistics) that provided a rich tableau for correlative studies. There were also great advantages for generating, calibrating, and controlling stimuli applied in the auditory versus the somatosensory or visual domains. The system seemed to be beautifully set up to study brain–behavioral relationships in behaving monkeys.

When I told Mountcastle that I was determined to shift my scientific focus to the hearing brain, he informed me immediately that, in that event, my postdoctoral studies would be conducted at the University of Wisconsin in the laboratory of Professor Jerzy Rose. The decision was made about 10 minutes before Professor Rose was told about it! The reader should understand that this kind of imperious treatment, professor to student, was accepted by me with respect: I knew that my mentor had my best interests at heart—and I knew that he had the greatest respect for Rose. Without hesitation, Mountcastle called Rose on the phone and said something like “Jerzy, I have a boy that I’m sending to you.” The deal was closed within a few minutes. For my female readers, this is what they used to call “the old boy’s network.” It was not about being fair.

In the late 1960s and early 1970s, the Wisconsin auditory research group was equal to any in the world. Jerzy Rose was a distinguished Germantrained Polish Jewish anatomist/electrophysiologist with a great scientific bloodline (Maximilian Rose was his uncle; Rose was trained by, and a great friend of, Cecile and Oskar Vogt), rescued from the Nazis shortly before the door closed. Rose was another man with extraordinary high standards of proof. Like Mountcastle (who had been strongly influenced by him through an earlier collaboration), he was exceptionally conservative in raising any arguments or extending any discussion in a manuscript or formal lecture past the cold hard facts of the study at hand.² But unlike Vernon, and just like my own kin, Rose was interested in everything, and he was willing to wrestle with the logic of any issue that you raised, usually initially taking a position that was contrary to yours! I suspect that this willingness to argue any issue was acquired at the Yeshiva. In any event, objectivity in perspective was the great lesson learned. Everything you “know,” every rock in your foundation of knowledge, should be turned over, because it might have a substantially different appearance when viewed from the other side!

At Wisconsin, I actually worked most closely with a wonderful scientist who has been a lifelong friend, John Brugge. Together, we derived the first detailed “maps” of auditory cortical fields in the macaque monkey, then conducted the first waking monkey recording experiments in these cortical areas. While these two studies were instructive and useful for experiments that were to follow, two off-the-beaten-track studies were actually more intellectually stimulating. First, Wisconsin had a wonderful mammalian brain collection, with well-preserved specimens gathered from about 130 mammals. I spent several months examining and documenting the auditory brainstems of all of these species, finding many marvels of comparative anatomy in the process. None was as astounding as the incredible specialization of the cochlear nucleus in a burrowing mammal, the “mountain beaver,” Aplodontia. I talked a trapper that I knew in Oregon into catching a few of these primitive burrowing rodents, where this species is native. We quickly discovered that they had unbelievably sensitive subsonic hearing. I constructed a special apparatus by which we could induce minuscule changes of pressure, and with my colleagues Lindsay Aitkin and Leonard Kitzes discovered that this creature’s inner ear could detect a 1 cc compression in a closed air volume of 30 cubic meters. This animal’s ear was a highly sensitive, living barometer! This is a very useful ability when you live in a complex burrow that you can plug with your fat little body! How could this animal hear, if his body plugged his burrow (and his side-mounted ears)? His ear canal was an Eustachian tube 7 or 8 mm in diameter, exiting from the back of the palate; that is, this beautiful little animal heard through his mouth! These specializations plausibly explained how this animal could have the lowest birthrate of any rodent, occupy a large-diameter burrow that is easily entered by innumerable predators (my trapper friend caught weasels, a spotted skunk, two martens, and a fisher in their burrows), yet almost never end up as dinner! I later determined that fat cells blocked the scala tympani in the central turn of this mammal’s pine-tree-like cochlea. This animal had evolved a kind of mechanical AC-to-DC converter in its inner ear! What a thrill it is, in science, to discover something about the nature of things that no one else before you had begun to imagine.

The second series of special studies arose through a wonderful, extended interaction with the great surface evoked potential cortical mapping authority in that epoch, Clinton Woolsey. Professor Woolsey and I had spent many wonderful hours together, talking about variations in the organization of cortical systems in different mammalian brains. Woolsey had encouraged a young neurosurgeon, Ronald Paul, to join his lab as a postdoctoral fellow. Because Clinton was no longer conducting experiments himself, he asked me whether I would agree to supervise Dr. Paul’s research project. Paul had already determined that he wanted to reconstruct the cortical “maps” of the hand surfaces in the macaque monkey after the surgical repair on the median nerve innervating the glabrous skin on the radial side of the volar hand. I agreed that this was a worthwhile study, and I enjoyed teaching the basic method of dense-array cortical recording (unit response “mapping”) to Dr. Paul.

There were two important outcomes in these studies. First, we quickly discovered that there were at least three complete hand representations in the cortical area that up to that time had been viewed (by Penfield, Woolsey, Mountcastle, and others) as a single field, “SI.”³ Second, more provocatively, we were astounded by the nature of the changes in receptive fields and in topographic organization recorded after peripheral nerve repair. It had been well established, in elegant prior studies, that after repair peripheral nerve fibers randomly reconnected to follow Swann cell tubes in the distal nerve stump. Yet, despite this dramatically shuffling of distal-to-central addresses, every cortical site in cytoarchitectonic area 3b (one of the 3 S1 subfields) had recovered a small, single, sharply defined receptive field; while every site (column) in cortical area 1 (a second S1 body surface representation) had two to five small, almost always widely separated cutaneous subfields. I struggled mightily to try to understand how this had occurred, given the then-predominant view that the adult brain was aplastic. I wrote a long section in the Discussion section of the manuscript in which I argued that this must mean that all of the divergent and convergent projection anatomy on the path from the skin to the cortex was a kind of illusion; that the only way that these small cortical fields could be reestablished was if at each level in the central somatosensory system, all of the neurons excited by divergent projections from a single cutaneous source were precisely recollected to project forward to the next system stage, and that this must occur across three anatomically divergent stages (i.e., within the dorsal column nuclei, ventrobasal thalamus, and in area 3b itself).

Woolsey did not like this Discussion section; he was not so enamored with my using my Cartesian instrument (my imagination, which I regarded as my powers of “reasoning”) as I was! He saved me the need for later embarrassing correction, because what we had observed was not a demonstration of precise divergent-convergent anatomy in a brain that was based on nearmiraculous point-to-point connectional detail. To the contrary, we had generated dramatic proof that the adult brain was massively plastic, with that plasticity achieved on the basis of Hebbian-network rules of competitive connectional remodeling. Alas, at this point, I was too narrow in my perspective to tumble to this very obvious alternative. My wife and I had talked about returning to the Western United States to be nearer our families as I sought a permanent faculty position. Our primary choices were to return to Johns Hopkins, to the University of Maryland (where Ron Paul had just been appointed Chairman of a new Neurosurgery Department), or to accept a position in Otolaryngology and Physiology (and in a new Neuroscience Program) at the University of California at San Francisco. For us, the continent naturally tilted westward.

Establishing a University of California at San Francisco Laboratory

My arrival in UCSF was blessed by my landing in a collaborative, interactive research environment that at that time had few equals in the scientific world. As the new “Director” of the John C. & Edward Coleman Laboratory (endowed by a California mining, banking, and insurance family in the 1920s), I quickly constructed one of the first computer-controlled electrophysiology laboratories at UCSF and initiated studies designed to define the functional organization of the principal midbrain auditory nucleus, the central nucleus of the inferior colliculus. My reasoning: It would be helpful to understand the basic ways in which information was integrated and “represented” at this level and at the level of the thalamus, before I charged into studying “big issues” in the cortex. With several outstanding young colleagues, we defined the three-dimensional functional organization of this key nucleus in relatively elementary response-related terms and, through a combination of physiological mapping and anatomical tracing studies, discovered that its isofrequency lamina topographically represented different sound parameter continua. This, astonishingly, was despite the fact that anatomical projections within the frequency dimension of representation were highly divergent; that is, every point on functional lamina from multiple input sources projected anatomically to every point across broad sectors of these central nucleus lamina.

It did not take us very long to determine that the auditory system again fed information forward to the medial geniculate body via a massively divergent projection—but again, as in the central nucleus of the inferior colliculus, functional maps in the medial geniculate body (MGB) were again highly refined and topographically ordered. And just to make a point, the system “destroyed” that emergent topographic “representation” a third time, via a highly divergent anatomical projection fed forward from the thalamus to the primary cortex.

From these laborious experiments came an important new insight into how this great neurological system is organized (b) for what purposes. The auditory system extracts common information from the auditory nerve, processing it in five or six elemental forms. It combines this information from two ears, thereby generating three or four more forms of elementary combinative extraction. It then converges (combines) all of this different monaurally and binaurally extracted information onto broad sectors of the isofrequency lamina of the central nucleus. It always keeps information sorted by frequency—but in other representational dimensions, every point source of information is dispersed very broadly across the next system level. From this massively convergent information, the next system level creates new, higher-ordered (topographic) representations of complex feature combinations across its frequency-band lamina, first in the inferior colliculus, then after a second recombination in the thalamus, then after a third recombination in the cortex. In the central nucleus, these selective and orderly representations across the nucleus’s isofrequency planes are already pretty sophisticated and must be pretty important for the brain’s sound feature representations. But alas, the auditory system repeatedly “destroys” them by feeding all information forward via those all-to-all isofrequency-plane projections.

One of the great joys of science is to have the data in hand, for the first time in human history, that can provide new insights into something that matters. I began to understand, by the mid-1970s, that the organization of the auditory system represented a fundamental challenge to the predominant model of brain organization that had been posited on the basis of more extensive visual system studies. With the exception of the physiological psychologists (who the scientists I had trained with did not pay much attention to) the overwhelmingly predominant view was that sensations, perceptions, and object recognition were a product of multiple-level anatomical construction. My colleagues and I were seeing something that challenged this simplistic model. Our system extracted information in a dozen ways; combined it all, then extracted again; then combined and extracted again; then again— just to get the cortical field A1! Even this country boy could understand the potential combinative selectivity and power of such an information processing strategy! And even this raw young scientist could see that there was a problem with understanding how the brain actually got the most out of this system. How does the brain fully exploit this power, if the connections in the adult brain are aplastic? Again, as with our findings following nerve transection and repair, for a second time in my scientific life I had powerful evidence about how the brain must be operating, without enough of a vision to fully understand its extended implications.

By 1973, I had worked my way up to the cortex in the adult awake animal (in these initial studies, the cat). I began by deriving the first detailed microelectrode maps of A1 and surrounding fields in this species—a duplication of earlier studies conducted in the macaque monkey—then turned to study cortical column organization in the waking animal. I quickly discovered something confounding. When you went beyond frequency organization, A1 in different individual cats could be very different in organization. Unlike V1, where the basic organization for any one cat and monkey pretty much applied for all other cats or monkeys, A1 in every adult cat was “special.” In some cats, we could define sharply bounded “cortical columns” with columnspecific response characteristics, representing this or that complex sound feature combination. In other cats, we saw no such thing. In the second or third case I studied, we documented an elegant representation of stimulus durations and intervals, expressed across a series of cortical columns. It was never seen again, in any other cat in that series.

“Surely,” I said to myself, “these differences must reflect the behavioral abilities that distinguish one cat from another. Surely they must arise from each individual animal’s behavioral experiences.” I was dangerously close, at this point in my research history, to understanding that the predominant scientific view that held that the adult brain was aplastic was bankrupt.

These studies also led me to ponder, once again, about the true nature of “cortical columns.” “How,” I asked myself, “can they be so prominent and well-defined in one animal, and so obscure and ill defined in another?” That reminded me, in turn, about the surprising outcome recorded in somatosensory cortex following peripheral nerve transection and regeneration. If you remember, in each vertical penetration into area 1, every neuron in a nerverepaired monkey appeared to have the same odd set of two to five widely separated receptive fields. “Why wouldn’t this provide us with a strategy for defining the true neuronal constituencies of, and the neurological processes that explained response sharing within, and the functional boundaries delimiting cortical columns?” I asked myself. “After all, every neuronal member of a column in this preparation would presumably share the same odd receptive field set, and its boundaries should be easy to define.” The best place to achieve the very precise and highly spatially refined recording needed to address these questions of neuronal coupling and cortical column boundaries and neuronal “memberships” would be in an unsulcated primate brain. Fortunately, I had a great friend at Vanderbilt University, Dr. Jon Kaas, who had been conducting studies in the visual system of the lissencephalic New World owl monkey. Because the central sulcus terminated medial to the hand area in these beautiful animals, the dimensions and neuronal connections and memberships of hypothetical cortical columns defined following nerve repair could be very precisely determined.

The young reader might see this shift in the focus of my attention from auditory neuroscience back to somatosensory neuroscience as a kind of self-imposed distraction. My advice to you is to make sure that your questions supersede your methodological approaches or models. Go where the question leads you. Go where the answer lies. After all, it’s all about making progress.

The owl monkey is an especially beautiful preparation for studying the orderly representations of the body surfaces in the brain, because most of their representations are exposed on the flat cortical surface. Our maps of the body surface in the S1 areas 3b and 1 were to become a landmark in somatosensory cortical studies. They quickly revealed a third general finding that challenged how we think about cortical representation: Just as in the auditory case, all maps of the surfaces of the hands were not the same. Indeed, especially in cortical area 1, body surface representations could be very different in different adult monkeys. Monkey A could have a huge thumb representation, while monkey B had almost no thumb representation; monkey C could have a large and refined representation of the dorsal hand, while monkey D had a small and primitive representation of the dorsal hand. “Surely,” the question again automatically rose to mind, “this must have something to do with what the monkey is and is not good at. Surely it relates to an individual monkey’s adult hand use.”

I had so much fun doing these experiments with Jon Kaas and a terrific group of young research fellows in his laboratory (John Wall, Randy Nelson, Daniel Felleman, Mriganka Sur, Roz Weller), driving them like slaves over a period of several months of almost continuous experimentation. While we were at it, we also mapped the somatosensory thalamus in three dimensions, as well as the somatosensory cortex in the squirrel monkey, in part to keep our little team busy while we waited for full recovery after repairing transected median nerves in a small group of owl monkeys. Those experiments were to lead to a radical change in my scientific career: the direct and unequivocal demonstration that large-scale plasticity was in play in the adult somatosensory cortex.

Before describing how that happened, I would like to complete one small detail of my narrative, because the finding is important but has never been published. Remember those two to five receptive fields that were recorded in a vertical penetration into S1? It turned out that each of these receptive fields engaged neurons across the dimensions of a distinctly delimitable column, but that every individual overlapping receptive field had its own column boundaries. Columns within and overlapping with other columns. And why were those two to five fields widely separated, one from another? Almost certainly because Hebbian-network processes established each receptive field, on the basis of differences in the temporal structure of its spatially separated inputs, as a competitor with the other emergent fields sharing the same cortical neurons. Columns are temporal neuronal alliances—a marvelous product of coincident input-based (Hebbian) plasticity! And their boundaries? A simple predictable product of competitive Hebbian-network plasticity.

The Cochlear Implant

Before I talk further about the origin of the work that I might be most identified with in the current era, brain plasticity science, it is appropriate to digress to discuss a second scientific program that was conducted in parallel in my laboratory across the decade of the 1970s and well into the 1980s.

The primary promoter of my recruitment in the Department of Otolaryngology at UCSF had been a highly distinguished otolaryngologist, Francis Sooy. This wonderful gentleman had the notion that the primitive scientific attempts that had been made to restore hearing by electrically stimulating the inner ear might have an important clinical future in his surgical field. He had already recruited an eccentric surgeon, Dr. Robin Michelson, to his Department faculty. Michelson had constructed and applied one of the first reliable “cochlear implant” models. As I heard Sooy talk about this subject during the process of my recruitment, I was intrigued by the possibility that something useful might be achieved. However, upon arrival at UCSF, I made the almost immediate decision that Robin Michelson was not scientifically prepared to achieve it, and although he pestered me incessantly asking for my help I shunned him, even while that is generally contrary to my nature. Robin (who later became a dear friend) had no real understanding of electrophysiology, and like most ear, nose, and throat doctors, had little understanding of the inner ear or auditory brain. I cringed when he told me “how his cochlear implant worked,” and how and why it benefited his patients.

After about a year of his pleading with me, I finally gave in, in part because I wanted to resolve issues of argument to get this pleasantly persistent cuss out of my office and off of my back. I said “Robin, give me 2 weeks to make preparations, and have your best patient come to my laboratory. I’ll set up psychophysical studies to determine what she can and cannot really hear. Then we’ll talk about it.” I prepared simple stimuli to play for her, so that we could systematically determine how she described and could discriminate between tones, tone stacks, noises, FM sweeps, et alia; and a young resident working in our labs, Dr. C. Robert Pettit, had a friend in the Music Department at San Francisco State University who helped generate aural speech and musical stimuli (different instrument voices, melodies, et alia). I thought that we were in for a long day of debunking.

I was wrong. By the end of a day of testing, this wonderful patient, Mrs. Ellen Bories, opened my eyes to what could be possible: the recovery of speech understanding through patterned electrical stimulation of the inner ear in a profoundly deaf individual. Implanted with a single pair of lowimpedance wires introduced into the scala tympani (what I sarcastically called a “railroad track electrode”) and excited with capacitively coupled (charged-balanced) pulsatile and analog stimuli, Ellen identified (for example) the sounds of a flute or bassoon, could easily identify the voices of different speakers, and could distinguish modulated frequency differences with reasonable fidelity up to 600 or 700 Hz. “What if she was being stimulated with 5 or 6 or 11 electrode pairs,” I asked myself, almost immediately. After all, communication engineers had already shown that one could produce perfectly intelligible speech via “vocoders” (human voice coders) that reduced band-passed speech to the outputs of 11 fixed-frequency oscillators; and they had shown that if the lowest sound processing channel representing first-formant frequencies (sounds up to 500–600 Hz) could rove to faithfully represent the strongest components in the first-formant (lowest) frequency range, fully intelligible speech could be achieved with a 5- or 6-channel device. Mrs. Bories’ outcomes indicated that this second glorious possibility just might be within reach!

Young scientists beware. This is what can happen to a person. There is nothing more wonderful or sleep depriving than the infection of a personal awakening that supports grand forward scientific possibilities!

With support from Neurology Institute grants and contracts (the latter from a crucial Neuroprosthesis Contract Program led by a great NIH administrator, Dr. Terry Hambrecht), we assembled a world-class team of otologists (Robin Michelson, Robert Schindler), neuroscientists (Mark White, Patricia Leake), mechanical, electrical engineers, technicians (Chuck Byers, Steve Rebscher, Gerald Loeb, David Patterson, Peter Zimmerman), and behavioral (speech) scientists (Elmer Owens, Dorcas Kessler, Mike Vivion).⁴ Over the first research decade (the 1970s), we focused on four fundamental problems that we thought must be addressed if we were to reduce the cochlear implant to a surgical/clinical reality.

Device safety. How can electrodes be mechanically designed to be inserted >25 mm into the spiral-form scala tympani without damaging this most fragile of biological structures? What materials could be applied to minimize tissue reactions and at the same time assure long-term device survival? How could we avoid untoward hazards that might apply for the heavy, continuous stimulation of surviving spiral ganglion cells?

Controlling the patterned electrical stimulation of the auditory nerve array. How could the requisite, discrete channel-by-channel excitation of the auditory nerve array be achieved? How could we most faithfully simulate normal auditory inputs via patterned electrical stimulation?

Device electronics. How should the implant electronics be designed to most effectively translate sound inputs into appropriately spectrally (spatially) and intensively patterned eighth nerve array stimulation? How, specifically, should speech be “encoded” by the cochlear implant?

Constructing a reliable and repairable prosthetic. How could implant materials, designs, and fabrication methods assure that an implant introduced into the inner ear in a young individual survivor for 90–100 years, that is, for a lifetime? If an implantable device did fail, how could it be replaced without removing an effectively hearing-restoring intracochlear electrode? And how could a device be designed to “grow” with the changing dimensions of the head and skull?

A Hard-Won Lesson about Patents

By 1979, we believed that we had reasonable answers to all of these questions.⁵ We had produced an 8-channel (16-lead) electrode array with mechanical characteristics that enabled its introduction long distances into the scala tympani without inducing cochlear damage. We had shown that chronic implantation and electrical stimulation in at least the cat model did not induce any additional damage to the surviving auditory nerve fibers in normally or in chronically deafened animals. We had shown that discrete channel-by-channel stimulation of the spiral-form intracochlear nerve array was achieved with this model. We had constructed miniaturized current-controlled stimulators that could engage intracochlear electrodes for a hypothetical lifetime without significant loss of metal or performance characteristics. We had constructed speech-to-patterned-electrical-stimulation voice coders that implemented the sound-processing strategies used to represent intelligible speech via transmitting minimal information in the telecommunications industry. We had implemented gain control strategies required to equate sound intensities with stimulus-evoked loudnesses. We had demonstrated, by the use of behavioral indices recorded using model devices controlled via a percutaneous connector, that we had successfully realized our basic engineering design specifications in deaf humans. It was time, we thought, for prime time.

I contacted the technology transfer office of the University of California system and explained to them that we had our hands on a practical invention of potentially great human and commercial value. This led to a series of meetings with medical device companies in the UC patent office. The first question asked by the first company: “Dr. Merzenich, where [the hell] are your patents?” It turned out that no company wanted to invest the several to many tens of millions of dollars required to bring the cochlear implant to market without having any patent protection.

As a typical academic idealist, I had the notion that we worked for the public, and that patent applications were, by their nature, selfish. I realized, in a flash, that this perspective was ignorant. Back in the laboratory on the following day, I asked our research team what we might still be able to patent. The two patents filed shortly thereafter (we could have filed 20 or 30 earlier, but did not) were ultimately a key to finding companies that would invest in what became the UCSF-Symbion cochlear implant (now manufactured and marketed by Advanced Bionics, Inc., a division of Boston Scientific).

A second lesson about patents was to be learned 7 or 8 years later, when a competitive company filed a lawsuit claiming that Advanced Bionics infringed on their patents. It turned out that we were first to invent on most of the issues in question but, without having filed patents, were subject to capricious challenge. At about the same time, another scientist filed and was awarded a patent that was claimed to represent an advance in cochlear implant encoding. Alas, the principle described in that patent had been explained to the “inventor” and others during a grant review site visit to my laboratory.

The young scientist should understand that patents can provide protection against the aggrandizement of valuable ideas, and against an antagonist frustrating your own research efforts; and patents can provide necessary protection for an investor who is willing and able on scientific and commercial grounds to help bring a big idea out into the real world. These facts partially explain why I have subsequently filed more than 70 patents, more than 50 of which have been awarded by the U.S. Patent and Trademark Office.

In the mid-1980s, I decided to withdraw from further research related to cochlear implant development. Most aspects of this invention now had a good scientific footing. It was clear that the application of these devices was going to be a practical success, and that additional efforts on my part would be largely lily-gilding. At the same time, this research field had already provided me with five wonderful gifts as a scientist.

First, it helped change many tens of thousands of peoples’ lives for the better. That achievement was a wonderful “bonus” for a laboratory scientist. Restoring useful hearing in an individual who has acquired profound deafness is, after all, the stuff of miracles.

Second, it elaborated my own self-development in the realm of technology transfer and practical engineering.

Third, it taught me about the problems of commercialization, and it gave me the great privilege and enjoyment of leading the first of a series of large multidisciplinary teams in which everyone worked together to achieve a great, common purpose.

Fourth, it taught my colleagues and me many new lessons about the value of applying alternate strategies, on the path to truly understanding the principles of one’s scientific subdiscipline (in this case, issues of auditory coding and auditory system function).

Finally, it provided us with powerful new insights into how the auditory brain must really be operating, and it greatly reinforced the growing understanding, coming from other research in my laboratory (and from other scientists), that the adult brain is a powerfully self-adjusting (plastic) organ.⁶ After all, the cochlear implant represents one of the great brain plasticity experiments conducted up to that time. Drive inputs into the brain that code complex signals (aural speech) in what must be a degraded and unequivocally different way (rather like playing a Chopin sonata with your fists), and not surprisingly, a patient initially understands almost nothing. Not too many weeks or months later, about 90% of patients understand almost everything, that is, can follow aural speech via hearing alone with few phonemic errors at relatively high word rates. When that recovery is achieved, most patients declared that their received speech now sounded “completely normal.” And despite the unequivocally large differences in its encoding, the patient had a full, complete, seamless connection to all earlier acquired information gathered in earlier life from his or her aural speech listening. This is not a miracle of neuroscience-guided engineering. It is a manifestation of a remarkably powerful adult capacity for top-down- (experience-) guided brain plasticity. As we declared “victory” over acquired deafness and abandoned this field in the mid-1980s, even I now understood the greater implications of the recovery of hearing in these patients: The adult brain is fundamentally plastic.

Plasticity

I have earlier noted that beginning in the 1970s, I traveled to Nashville first to map in detail the S1 somatosensory cortical areas in the lissencephalic owl monkey, then, with this crucial foundation data in hand, to transect and surgically repair the median nerve, as the first step in an experiment designed to measure the true dimensions and nature of (somatosensory) cortical “columns.” When we mapped the cortex after median nerve regeneration several months later, we had a great surprise: the majority of the territory that formerly represented the skin field of the median nerve was now occupied by other inputs, arising from either the ulnar side of the palm and fingers, from the back of the hand, or from the face—unequivocal evidence of large-scale representational plasticity. Moreover, we soon realized at this point that the recovery of the representation of the median nerve skin with its emergent, discrete, topographically represented patches of a restored skin field representation was a fabulous expression of coincident input-based (Hebbian-network) plasticity!

With this (for us very exciting) finding, we immediately initiated a second experiment, in which we cut the same large cutaneous nerve—but in this case did not allow its regeneration. Several weeks later, this very large cortical territory was completely occupied by expanded inputs from other hand and face surfaces. In a special variation of this experiment, we tracked the progressive reorganization of the cortex at different times in individual monkeys. That study not only documented the sequence of progressive remodeling of this large cortical zone, but showed that even areas remote from the nerve transection (for example, the cortical representation of the face bordering the hand area, or the far-ulnar side of the hand) were unequivocally different in detail, each time it was mapped in the same monkey.⁷

In addition to documenting a capacity for large-scale plasticity in adult brains, these studies supported a very important general conclusion about cortical representational processes. Because any given skin surface could be represented at different locations at different times in the life of an adult monkey, the common view that there was a fixed relationship between cortical location and perceived skin location (the “grandmother neuron” model) could not be correct. Cortical representations had to tolerate the fact of plasticity. They must be relational.

These simple and inescapable conclusions provided a basis for my happy abandonment of the fixed-location, aplastic-adult view of the brain that I had been carrying around as heavy, tired baggage, for more than a decade!

When I returned to San Francisco, we initiated several experiments that quickly confirmed that cortical representations of the skin surface were (as Donald Hebb had argued) coincident-input based: considered in detail, cortical “maps” were actually dynamic, temporally based (not stable, anatomical) constructs. Studies in behaviorally trained monkeys showed that the neuronal memberships of (the dimensions of) cortical columns were highly plastic, on these same “competitive Hebbian-network” bases. The “rules” governing this plasticity were revealed by studies in which we varied temporal inputs or varied the dimensions and separations of the skin-surface competitors that were engaged by training. Large-scale plasticity completely consistent with a competitive Hebbian-network model was recorded in all of these studies.

These findings strongly supported the view that brain remodeling provided the basis of skill acquisition at any age⁸—that skill acquisition was equatable with connectional “specialization” achieved via relatively simple plasticity principles. As our adult monkeys acquired or refined a skill or ability, their brain was “specialized” in ways that repeatedly accounted for that acquisition or refinement.

This perspective was contrary to the predominant view of neuroscientists in that era and, as I began to argue this position, my colleagues and I were subjected to very strong criticism by powerfully entrenched investigators— most operating from a visual neuroscience perspective. They held that the brain was plastic (connections could be remodeled) within a limited, early “critical period,” evolving to a mature aplastic phase at the end of this epoch. How, then, could one account for the seamless elaboration of skills and knowledge that extended to the end of life? The most common analogy was to the computer, which had fixed functional elements and connections and a resident operating system and programs, now burned in from a strong inherited base.

Because this incorrect conclusion indicated that developmental potential ended with critical period closure, it had powerful, negative impacts on educational science and in medicine, because it led to the operational position that an individual was stuck with his or her postcritical-period brain through the remainder of his or her life—that deficits recorded when a child entered school, for example, would have to be accepted as a fixed (largely inherited) reality—and that the physical brain from a young age onward had only one trajectory: downhill. Nothing could be further from the truth.

While the mainstream of neuroscience held to this view as religion (Hubel and Weisel were awarded a Nobel Prize in 1979, in large part for positing it), there was a small group of neuroscientists, the “physiological psychologists,” who had already documented many aspects of cortical plasticity. Almost no one in my mainstream camp—including myself—had paid enough attention to them. One limitation of their studies was the almost exclusive use of the Pavlovian (classical) conditioning model. Still, scientists like Charles Woody, Jerome Engel, Richard Thompson, E. Roy John, John Disterhoft, and Norman Weinberger (among others) had conducted compelling studies documenting large-scale changes in cortical responses that met all of the contingent requirements of Pavlov’s model. For example, Woody and Engel recorded large changes in the neurological representations of both the unconditioned stimulus and the conditioned response in rabbits trained to avoid air-puff stimuli; Disterhoft first showed that changes selectively amplified the representations of conditioned stimuli; Weinberger’s group repeated and greatly elaborated these studies, recording single-unit-level changes for conditioned stimuli that endured as long as conditioning was sustained, but that reverted to a pretraining status when conditioning was “extinguished”; while Richard Thompson and colleagues showed that all of the changes contributing to classical conditioning could be recorded in the same machinery (in deep cerebellar nuclei). In parallel with these studies, scientists like Mark Rosenzweig, Marian Diamond, and Roy Johns had shown that plastic remodeling is almost certainly a universal property of the mammalian forebrain. Train an animal any which way and watch it change before your eyes, by elaborating neuronal connections, or by instantiating the operational rules of classical (Pavlovian) conditioning! In the light of these important earlier studies, I have sometimes been very embarrassed to be called “the father of cortical plasticity”!

At the same time, my research group did rapidly extend these earlier studies in a number of important ways. We documented the fact of plasticity in the domain of operant conditioning, which is a primary route to human skills acquisition. We illustrated its nature and power in models of nerve and brain injury that bore strong implications for rehabilitation. We provided proofs that Hebbian-network plasticity principles accounted for primary plasticity phenomenology, which immediately brought plasticity research into a higher logical frame. We described “adult” plastic changes in terms of classical neurophysiological constructs: cortical receptive fields, cortical columns, cooperativity, competitive network plasticity, synaptic plasticity, inhibitory and excitatory processes, et alia. We added substantially to our understanding of how plasticity was controlled and regulated in adult brains. We provided compelling evidence that selective attention/ working memory/prediction controlled adult cortical plasticity. We effectively demonstrated that plasticity could not be isolated to any one system level but, to the contrary, inevitably applied for brain systems and networks. By these studies, we helped define plasticity phenomenology in the operational terms of our then-current understanding of the fundamental machinery of the brain. Perhaps most important, we began to consider how these processes might be employed therapeutically to empower underfunctioning brains, or to drive neurologically or psychiatrically dysfunctional brains, through training, in strongly “corrective” (renormalizing) directions.

Lifelong Brain Plasticity

Before I discuss our efforts to translate this science into therapeutic strategies that could be applied in neurological and psychiatric medicine, it is useful to describe studies conducted primarily over the past two decades that I believe shall result in another fundamental correction about how we think about the brain and its plasticity. In understanding that brain plasticity operated by Hebbian-network “rules,” we understood how to drive positive (refining) or negative (degrading) changes in cortical representation, that is, immediately appreciated that plasticity processes are, by their nature, reversible. In the late 1980s and early 1990s, we conducted several studies that demonstrated that these principles unequivocally applied for the adult primate brain. For example, studies conducted with a superb doctoral student, Gregg Recanzone, showed that training a monkey with locationally invariant point-like stimulation on the hand (the monkey was engaged in a vibratory frequency discrimination training task) resulted in a dramatic increase in cutaneous receptive field size and in a >100x expansion of the neuronal population (cortical column neuronal membership or volume) representing the engaged skin spot. By contrast, when we randomly moved the stimulation site to different loci over a small finger zone on each successive training session, exactly the opposite occurred. Receptive field sizes shrank to a fraction of their pretraining areas, and cortical columns and their neuronal memberships were reduced to about one-third of their pretraining dimensions! In the former case, that single constantly engaged skin location was a competitive “winner.” In the latter case, each small stimulus location was a vigorous neuronal and territorial competitor!⁹ In the same general way, the Hebbian model—affirmed by direct animal model studies—quickly demonstrated that the same two-way (refining or degrading) plasticity applied for the representations of all other stimulus-parameter continua.

In later studies, we documented the changes in the cortex from the time of the onset of the critical period onward, marking the progression to “adult” cortex, then tracking changes forward into old age. Such studies led to a reinterpretation of the significance of the critical period. In the auditory cortex, it is a period of unregulated Hebbian-network plasticity through which cortical processing can be specialized in an extraordinary stimulus-exposure-specific manner. In the auditory system, its closure is defined locally, in the cortex itself, on the basis of the local schedule of activation by correlated inputs; there are many critical periods in play. Just as important, our studies led us to question the classical dogma that the brain is on a one-way trajectory of “development.” We now know, in fact, (a) that we can rapidly “mature” a cortex by providing it with a hyperrich environment (accelerating representational refinement); (b) we can rapidly “age” the “mature” cortex by maintaining the animal in continuous, moderate-level noise (accelerating representational degradation); (c) we can almost completely rejuvenate the cortex of the old animal (establishing most of the physical and functional performance indices of a vigorous young adult) by appropriately and intensively training the animal (driving positively representational refinements); and (d) we can drive the cortex back to the state of infancy, as defined by its physical and functional status, in an animal of any adult age (driving negative representational degradation), again by adding to the noisiness of cortical process by delivering moderate-level extrinsic noise or by amplifying intrinsic process noise.

These studies documenting the fundamental bidirectionality of cortical plasticity provide a strong basis for understanding likely “failure modes” of this self-organizing machine—failure modes that we identify as plausibly underlying the “great illnesses” recognized in psychiatric and neurological medicine. They also support our growing conclusion that variations in the noisiness of cortical processes are a major contributor to variations in human performance ability. Cortical process “noise” could arise from intrinsic sources contributed to by hundreds of possible genetic faults. It would also be expected to result from variations in the richness and reliability of early childhood (or adult) experiences, and from variations in environmental exposures to a rich variety of factors (heavy metals; toxins; prescribed medicines; acoustic and visual noise exposures; hypoxic episodes; brain infections; bumps on the head; et alia). In our models, we affirmed these general conclusions by manipulating the qualities of early childhood and adult experiences, and by exposing animals to environmental toxins or physical embarrassments (PCBs, hypoxia, SSRIs, et al.). In every model, the cortex was driven to a more refined or a more degraded functional and physical state (development or adult functional status was accelerated and upgraded—or delayed and downgraded), just as predicted by these plasticity-is-inherently-reversible models!

These studies provide the basis of a second great correction in how we should think about the mammalian brain: The brain slowly organizes its selective processes plastically to a level of refinement that normally peaks in young adult life. Anything that contributes to greater process noise across this epoch will delay and frustrate the achievements of the brain’s self-organizing processes. A rich early engagement with the world can accelerate and beautifully elaborate those achievements. Beyond its functional peak, as noise grows within the machinery of the average older adult (largely, we are convinced, due to limitations in a typical individual’s brain use), the two-way plasticity processes slowly adjust “backward” (degrade functional brain operations). Functions that were the last to be mastered in the old brain are the first to be degraded, as the selective processes of the brain progressively roll backward. Ultimately, the functional and physical status of the older brain progressively reverses to be more and more undifferentiated; that is, its physical, chemical, and functional characteristics are more and more like those recorded in the child and (ultimately) infant brain.

Fortunately, at any point in life, positive changes in the operational capabilities of the brain can be rapidly achieved through relatively simple forms of positive (refining) training!

Brain Plasticity-Based Therapeutics

By the late 1980s, we had begun asking ourselves: How does natural “negative” plasticity contribute to the functional decline recorded in almost every chronic psychiatric and neurological illness? Given its fundamentally reversible nature, could we more effectively employ plasticity to contribute to functional recovery in chronically impaired or “ill” individuals, or following brain injuries? How can positive brain change rates be optimized? What catastrophic failure modes apply for a self-organizing brain? Could we prevent them by strengthening brain function via plasticity, prior to disease onset? Would it be possible to drive what we know to be reversible plasticity processes “backward” to recover more normal function—or dare we imagine, to overcome or cure, long-enduring impairments or chronic “disease”?

All of these questions tumbled around in our arguments and minds across the early 1990s. They had already led us to the first crystallized understanding that the adult brain’s inherent plasticity could provide the basis for a revolution in how we think about the neurological origins of ourselves and our operational abilities. And they inspired us to work hard to understand how we might be able to control the genie, to achieve potentially powerful therapeutic strategies.

As we were actively seeking a model for initiating an evaluation of these great prospects, one landed squarely in our laps. It came in the form of an invitation to a meeting organized by a Rutgers University professor, Dr. Paula Tallal. The meeting topic was “processing speed,” a subject that had completely consumed Paula since her discovery, about two decades earlier, that kids who operated sluggishly in processing successive acoustic inputs were delayed in language development and struggled to initiate effective reading. I had told Dr. Tallal in conversation that this is a problem that I thought we could “fix” by intensive plasticity-based training. After we described how we believed this could be achieved at her symposium, Paula invited us to include a collaborative project supporting our construction of a suite of training tools in a consortium grant that was submitted to the Dana Foundation. In this grant, we committed to construct brain plasticity-based training programs designed to progressively drive positive plasticity in ways that would enable more accurate and higher-speed processing in her speed challenged language and reading-impaired kids. Paula’s part of the grant supported outcomes trials evaluating the effectiveness of our novel training approach.

With very important advice from Paula and from Steven Miller, a postdoctoral fellow leading the outcomes research in her laboratory, Bill Jenkins (a brilliant neuroscientist/psychologist/technologist) and I (with help from two engineers, Xiaoqin Wang and Srikantan Nagarajan) designed the first version of what would become the “Fast ForWord” language training program. Jenkins recruited UC engineering undergraduates and a brilliant high school student to construct these programs. The first models were completed in about 6 months.

Because Jenkins and I were anxious to understand what was happening in the outcomes trial, we designed the software to record performance data in detail, and with the help of another key technical collaborator (Bret Peterson) wrote custom software to assure the automatic transmission of that data back to us every day on the Internet. This was the first application of the automatic Internet/database tracking of trainee outcomes, a fact later acknowledged by awarded patents. As the days passed across this 1-month-long study, our excitement grew because we could see at a distance that all seven language and reading-impaired kids were making great progress, ultimately achieving performance levels that applied for normal kids.

As Paula and Steve’s team began their blind posttraining outcomes assessments, Bill and I were on the plane to Newark. We were greeted with very large smiles. The blind assessors had found that all seven children had made strong gains in their aural language abilities. Their improvement generalized richly to performance indices recorded by every measure, in a standard language assessment battery. Both their aural speech production and reception had markedly improved. Their speech reception accuracy in noise had been normalized. Different assessments of language and speech-in-noise improvements moved by about 1 to 2 standard deviations!

For several children, the training had been unequivocally transformative. I still remember one quiet, darling, almost-6-year-old boy who had a language age of about 2.5 at the beginning of the trial. One month later, this now-confident little chatter-box operated in language as a normal almost-6-year-old, and he now wore a smile on his face that could melt a rock!

This visit to Paula’s laboratory at the end of this trial was one of the happiest days of my scientific life because I knew, in these kids’ outcomes and in their faces, that our science could be extended to help hundreds of millions of children and adults in the world—to change the lives of many millions of individuals for the better.

At dinner that evening, I suggested to the group that we had to figure out how to deliver this training out to all of those kids who could be helped by it. “We’ll have to write patents. We may have to help establish a company, or find a company that would do a good job delivering this kind of program to kids in need.” Jenkins and Miller immediately signed on. Paula was more conservative by nature. She quite correctly insisted that nothing practical could really be accomplished until we had completed a controlled trial.

We all agreed that such a trial could be conducted with still-better software over the following summer. In the meantime, I would work “in my free time” to organize an effective technology translation strategy.

Birthing Scientific Learning Corporation

Upon returning to San Francisco, we began writing what would become a series of important patents summarizing our therapeutic tools. I then met with our wonderfully supportive Chancellor, Dr. Joseph Martin, and explained to him that I needed the University’s help in determining how to help deliver these useful training strategies out into the world. Joe ultimately organized a team of advisors—a group of San Francisco’s wealthiest citizens chaired by the investment guru Charles Schwab—to listen to my story. Mr. Schwab asked me to prepare a “business plan” to distribute to this group before our meeting.

In fact, I wrote a brief scientific treatise because I knew nothing about business or business plans. Mr. Schwab began the meeting by dropping my document down in front of me while he said, rather sharply, “This is no business plan…. Dr. Merzenich, what are you selling? Who are you selling it to? Who would control its purchase? How would you convince therapists or teachers or parents that this would be good for their children? How much would it cost?” On and on, went the obvious, business-101-level questions. My advisors were not impressed by my feeble preparations!

At the same time, this group did conclude in their report to Dr. Martin that “these scientists just might have something that could have a major impact on these child populations and could become a substantial business”; that “you’ll have to let Merzenich be involved in creating a company, because it probably can’t succeed without him [our team]”; and that “he’ll probably have to play a leadership role in the business in its start-up phase.” When Joe Martin got this report, he agreed to make an exception to the usual UCSF policy by allowing me to work to establish and lead this business on an 18-month-long leave of absence. I shall be forever appreciative of his help and generosity, because the meeting with these business advisors crystallized my appreciation of the seriousness of the business creation process and allowed me to focus on creating Scientific Learning Corporation without having to give up my cherished UCSF laboratory and professorship.

Of course, business creation depended crucially on the outcome of the controlled trial being conducted in Paula’s laboratory. When it confirmed our initial findings, we quickly wrote two companion papers for Science. Their publication resulted in more than 40,000 phone calls to the Rutgers and UCSF switchboards by parents and other individuals asking for information about how a child they loved might be helped with this software. Business creation also required leadership from the business side, and wonderful assistance almost magically appeared in the forms of David Charron and Carl Holstrom as we struggled to create a new company and organize its initial financing. Bill Jenkins and Steven Miller agreed to leave their University positions to head key business divisions (product development; outcomes research). Paula was able to initiate a sabbatical, so that her wisdom and energy could be brought to bear in our early program designs and research planning. While it had absolutely nothing to sell to anyone in hand, Scientific Learning Corporation was off to a very strong beginning!

With support from “friends and family,” then from an investment company (Warburg-Pincus), we rapidly created the initial forms of child-training software and enlisted the unpaid assistance of more than 30 high-quality speech therapists to help evaluate it. They relatively quickly returned data to us from many hundreds of impaired kids. Again, universally strong gains in longitudinal assessment indices were recorded in these children from every clinic. We now knew that we had a clinically validated product that should ultimately transform the lives of millions of developmentally limited kids.¹⁰

Crossing the Great Divide: A Neuroscientist in a (Brave) New World

As a scientist-CEO, I immediately began investing in science that could extend the application of brain plasticity-based training to impaired adult populations. Research initiatives targeting the treatment of motor disorders, schizophrenia, depression, traumatic brain injury, and other important human problems were begun. Patents were written. Prospects for great future business appeared to be wonderful.

In the meantime, I made preparations for returning to the University that began with the recruitment of a professional executive to lead Scientific Learning. That new executive almost immediately decided that the company had to “focus to win”; non-child research initiatives were abandoned. This decision was terribly frustrating, because I knew that our science could be applied to help many other human populations. The preliminary work that had been accomplished and the patents that had been awarded that seemed to open up this far-wider window soon lay dormant.

After nearly a decade of trying to influence Scientific Learning to pursue wider interests, I finally negotiated an agreement with them by which we could apply “their” patents (some of the most important of which came from my laboratory’s research) to help adult populations with normal aging-acquired or clinically acquired impairments. With that agreement completed in 2004, Posit Science Corporation was founded and immediately directed its sights on adult “brain health” (the losses accompanying normal aging) and toward developing effective treatments for a variety of psychiatric and neurological conditions that could be addressed via brain plasticity-based therapeutics. To further expand our scientific reach, The Brain Plasticity Institute was founded in 2008. Designed as an “incubator company,” its goal is to conduct research and to create practical brain plasticity-based strategies that can potentially address many other human impairments and maladies that would otherwise receive little scientific attention.

This period of working to help deliver science-based therapeutic tools out into the world has been richly rewarding. Our first kid trainees are now of a college age; one wonderful young child in that first study is now pursuing her Ph.D. in psychology! Many thousands of patients and aged-infirm individuals and parents and therapists and teachers have written to us, or told us contributing scientists in person, how the programs that our teams have created have greatly helped them, and often literally transformed or recovered their (or their children’s) lives. What a bonus such feedback is for an inveterate lab rat like me!

As these programs have come out into the world, their effectiveness has been repeatedly confirmed in controlled studies conducted in many hundreds of clinics and schools and university laboratories. Several hundred such studies employing the training programs that we have created are now in progress in clinics and laboratories across the world. Whenever a scientist has appropriately conducted a longitudinal brain recording or imaging study, he or she has found that the training that we developed—designed for whatever purpose—has driven the patterns of responses in the brain in the predictable “corrective” direction. Many such studies have now been published in the peer-reviewed literature. These behavioral and neurological outcomes provide powerful evidence that we understand (to an initial level of perfection) how to control neuroplasticity processes for therapeutic good.

Over the next decades, you shall witness the rapid maturation of this therapeutic field, as hundreds of tools developed to “reverse” plastic changes that limit the performance abilities of patients with many classes of neurological and psychiatric impairment and disease are brought into the world. I believe that in time, this “organic” medical approach—employing the powerful plasticity processes of the brain to “heal” itself—will largely supplant less sophisticated, currently predominant neuropharmacological treatment strategies.

Back to Square 1: Understanding Myself

The great philosophers of the Age of Enlightenment understood that the brain is a trickster; that our realities are an almost unfathomable abstraction; that I am my own brain’s creation. In their wake, scholars have repeatedly argued, from many directions, that the person that you or I are behaves according to the standards of our species, but with very powerful biasing in behavior stemming from our individual histories.

As a young scientist, my main goal was to understand the neurological origins of my own personhood, and of the consciousness that haunts it. As I’ve grown older, I am no longer as interested in the basis of consciousness itself. Continuous awareness is a glorious aspect of ourselves. We understand neurophysiological correlates of that awareness; it clearly arises through those processes as an important aspect of our personal evolution. Plasticity processes are designed, I believe, to sustain it no matter what. Our hypothesis has been that the brain specifically regulates its plasticity to sustain ongoing awareness, which is sine qua non with survival itself.

As my perspective grew as a scientist, it became increasingly obvious to me that there was a more important question than the origin of the flame of “consciousness”: Why do I (why do we humans) behave the way that we do? Where does the operational person that we are come from? This question has been answered with increasing clarity, and to my satisfaction at a level of process and mechanism, across my scientific lifetime. We now understand that our specific functional skills and abilities arise as a product of our experiential (brain plasticity) histories. As William James argued more than a hundred years ago, our abilities and achievements reflect the simple sum of our experience-acquired and brain plasticity-achieved skills and abilities, which we have employed to record the massive body of information that shapes and ultimately controls our mental and physical actions.

In the same way, scientists have provided us with an understanding of the neurological origins of agency and the “self.” Miyashita and Sakai first showed that associative learning is a fundamental achievement of brain plasticity. A variety of studies show that agency is a product of those associative memory processes. Put another way, for every feeling, thought, or action, there is an association with their source, literally billions of times a year. That source is creating powerful self-reference! The demonstration that the person you or I have become is a product of your/my brain plasticity within our lifetimes is, for me, a satisfactory answer to the great questions that originally motivated my entry into neuroscience.

But on the way to answering that question, what a rich panoply of other questions have arisen, only some of them answered. This scientist deeply appreciates the privilege of being supported by his fellow citizens to work in this garden of earthly (scientific) delights.

An Afterword: Advice to a Young Scientist

The culture of science and modern culture and its technologies are advancing at breakneck speed, and any advice to a young scientist must be limited to general issues that related to the overall quality of your life and work. We could list them under the heading: “Top ten things that worked, for me.”

First, identify a big issue (or two). Live it. Breathe it. Take a scholarly approach to wrapping your brain around it. Try to understand how prescientists and scientists have thought about your issue, from about 1000 BCE onward. Accept your responsibility to become a world authority on your subject. If not you, who?

Second, organize a personal self-development plan, to prepare yourself for scientifically approaching your “great issue.” Think forward 10 years and ask yourself “what skills and abilities must I acquire, to make the most progress toward understanding my own, personal big question(s)?” Foremost among those abilities: Your skills at organizing, inspiring, and leading a team of fully empowered collaborators.

Third, create a logical construction that informs you in detail about what you know and don’t know that is relevant to answering your great question. Feed and nurture this logical construct, almost every day. Before you know it, as in The Little Shop of Horrors, it will take on a life of its own— and if you’re lucky, threaten to consume you!

Fourth, seek multidisciplinary enrichment. All of the best work that I have achieved has been with the collaboration with research fellows or clinicians or technologists who have special abilities that elaborate my own knowledge and technical proficiencies. The modern scientist who limits his or her knowledge and methodological repertoire to the boundary of his or her own experience, intelligence, and technical repertoire, or who selfishly controls what his or her collaborators do or think is a damn fool.

Fifth, look for the opportunity to carry your science out into the world. To help other scientists. To help the citizens who have been paying the bill for you having all that fun. To help yourself grow with the knowledge that what you do matters, not just for the growth of knowledge. It’s not what you do. It’s what your science does.

Sixth, leave the lily-gilding to the saints and angels. While it’s often easier to get grant support to conduct studies with already-established answers, your time is far better spent conducting studies that really matter.

Seventh, don’t limit your sources of information to the scientific literature—and especially to the incredibly arcane literature that relates to your sub-subdiscipline of neuroscience. Far too many scientists limit their knowledge and invention to those things that fall within the “religion” of their little scientific pocket. The more ways that you can nuance your flexible intelligence from domains outside your scientific sphere, the more likely you are to be truly intuitive and inventive.

Eighth, it’s not about competition. It’s about progress. “Cast your bread upon the waters,” said an old mentor (Meyer Schindler). “Some of it will come back sponge cake!” Scientists who worry too much about telling other scientists what they think matters just aren’t making progress fast enough.

Ninth, don’t neglect the training of those who help you. Ultimately, their collective achievements will vastly exceed yours. The better prepared they are to achieve, the more impact your own efforts will have out in the world.

Finally, don’t forget to carry your “heart” along for the ride. Think beyond yourself, as you think about who benefits from what you do. Care about it. And think beyond yourself, when you think of others you have invited to join you, in the lab and in your home, on this wonderful journey.

Selected Bibliography

Early Studies

Brugge JF, Merzenich MM (1973) Responses of neurons in auditory cortex of macaque monkey to monaural and binaural stimulation. J Neurophysiol 36:1138–58.

Harrington TH, Merzenich MM (1970) Neural coding in the sense of touch. Exp Brain Res 10:252–64.

Merzenich MM, Brugge JF (1973) Representation of the cochlear partition on the superior temporal plane of the macaque monkey. Brain Res 50:275–96.

Merzenich MM, Harrington TH (1969) The sense of flutter-vibration evoked by stimulation of the hairy skin of primates. Exp Brain Res 9:236–60.

Merzenich MM, Kitzes L, Aitkin L (1973) Anatomical and physiological evidence for auditory specialization in the mountain beaver (Aplodontia rufa). Brain Res 58:331–44.

Paul RL, Goodman H, Merzenich MM (1972) Alterations to mechanoreceptor input to Brodmann’s Areas 1 and 3 of the postcentral hand area of Macaca mulatta after nerve section and regeneration. Brain Res 39:1–19.

Paul RL, Merzenich MM, Goodman H (1972) Representation of slowly and rapidly adapting cutaneous mechanoreceptors of the hand in Brodmann’s Areas 3 and 1 of Macaca mulatta. Brain Res 36:229–49.

Functional Organization of the Auditory and Somatosensory System

Kaas JH, Nelson RJ, Sur M, Lin C-S, Merzenich MM (1979) Multiple representations of the body within the primary somatosensory cortex of primates. Science 204:521–23.

Merzenich MM (1986) Sources of Intraspecies and Interspecies Cortical Map Variability in Mammals: Conclusions and Hypothesis. In: Comparative Neurobiology: Modes of Communication in the Nervous System M. Cohen and F. Strumwasser, eds, Wiley, New York, pp. 105–116.

Merzenich MM, Allard T, Jenkins WM (1991) Neural Ontogeny of Higher Brain Function; Implications of Some Recent Neurophysiological Findings. In: Information Processing in the Somatosensory System O. Franzén and P. Westman, eds, MacMillan Press, London, pp. 293–211.

Merzenich MM, Jenkins WM, Middlebrooks JC (1984) Observations and Hypothesis on Special Organizational Features of the Central Auditory Nervous System. In: Dynamic Aspects of Neocortical Function. Wiley, New York, pp. 397–424.

Merzenich MM, Kaas JH, Sur M, Lin C-S (1978) Double representation of body surface within cytoarchitectonic areas 3b and 1 in “SI” in the owl monkey (Aotus trivirgatus) J Comp Neurol 181:41–74.

Merzenich MM, Kaas JH (1980) Principles of Organization of Sensory-Perceptual Systems in Mammals. In: Progress in Psychobiology and Physiological Psychology J. Sprague and A. Epstein, eds. Academic Press, New York, pp. 1–42.

Merzenich MM, Knight PL, Roth GL (1975) Representation of cochlear within primary auditory cortex in the cat. J Neurophysiol 38:231–49.

Merzenich MM, Reid M (1974) Representation of the cochlear within the inferior colliculus of the cat. Brain Res 77:397–417.

Middlebrooks JC, Dykes RW, Merzenich MM (1980) Binaural response-specific bands in primary auditory cortex (A1) of the cat: Topographical organization orthogonal to isofrequency contours. Brain Res 181:31–48.

Roth GL, Aitkin LM, Andersen RA, Merzenich MM (1978) Some features of the spatial organization of the central nucleus of the inferior colliculus of the cat. J Comp Neurol 182:661–80.

Cochlear Implant Development

Loeb G, Byers CL, Rebscher S, Casey D, Fong M, Schindler RA, Gray R,Merzenich MM (1983) Design and fabrication of an experimental cochlear prosthesis. Med Biol Eng Comput 21:241–54.

Merzenich MM (1975) Studies on Electrical Stimulation of the Auditory Nerve in Animals and Man; Cochlear Implants. In: The Nervous System, Vol. 3. D. Tower, ed., Raven Press, New York, pp. 537–548.

Merzenich MM (1979) Cochlear Implants: State of Development and Application. In: Interrelations of the Communicative Senses. L. Harmon, ed., pp. 325–337;

Merzenich MM, Byers CL, White M, Vivion MC (1980) Cochlear implant prosthesis: Strategies and progress. Ann Biomed Eng 8:361–68.

Merzenich MM, Michelson RP, Pettit CR, Schindler RA, Reid M (1973) Neural encoding of sound sensation evoked by electrical stimulation of the acoustic nerve. Ann Otol 83:486–504;

Merzenich MM, Rebscher SJ, Loeb GE, Byers CL, Schindler RA (1984) The UCSF Cochlear Implant Project: State of Development. In: Cochlear Implants in Clinical Use. Karger, Basle, pp. 119–144.

Merzenich MM, White M (1977) Cochlear Implant: The Interface Problem in Functional Electrical Stimulation. In: Biomedical Engineering and Instrumentation.F. Hambrecht and J. Reswick, eds., Marcel Dekker, Inc., pp. 321–340.

Merzenich MM, White MW (1980) Coding considerations in design of cochlear prosthesis. Ann Otol 74:84–7.

Schindler RA, Merzenich MM (1974) Chronic intracochlear electrode implantation: Cochlear pathology and acoustic nerve survival. Ann Otol 83:202–16.

White MW, Merzenich MM, Gardi JN (1984) Multichannel cochlear implants. Channel interactions and processor design. Arch Otolaryngol 110:493–501.

Defining the “Rules” of Adult Cortical Plasticity

Allard TA, Clark SA, Jenkins WM, Merzenich MM (1991) Reorganization of somatosensory area 3b representation in adult owl monkeys following digital syndactyly. J Neurophysiol 66:1048–58.

Buomomano DV, Merzenich MM (1998) Cortical plasticity: From synapses to maps. Ann Rev Neurosci 21:149–86.

Clark SA, Allard T, Jenkins WM, Merzenich MM (1988) Receptive fields in the body surface map in adult cortex defined by temporally correlated inputs. Nature 332:444–5.

Jenkins WM, Merzenich MM, Ochs M, Allard TT, Guic E (1990) Functional reorganization of primary somatosensory cortex in adult owl monkeys after behaviorally controlled tactile stimulation. J Neurophysiol 63:82–104.

Merzenich MM (1987) Dynamic Neocortical Processes and the Origins of Higher Brain Functions. In: The Neural and Molecular Bases of Learning. J-P. Changeux and M. Konishi, eds, Wiley, Chichester, pp 337–58.

Merzenich MM (2001) Cortical Plasticity Contributing to Child Development. In: Mechanisms in Cognitive Development. J. McClelland and R. Siegler, eds., L. Erlbaum Assoc., Mahwah NJ, pp. 67–96.

Merzenich MM, DeCharms RC (1996) Neural Representations, Experience and Change. In: The Mind-Brain Continuum. R. Llinas and P. Churchland, eds., MIT Press, Boston, pp. 61–81.

Merzenich MM, Jenkins WM (1993) Cortical Representation of Learned Behaviors. In: Memory Concepts. P. Andersen, et al., eds., Elsevier, Amsterdam, pp. 437–53.

Merzenich MM, Kaas JH, Wall J, Nelson RJ, Sur M, Felleman D (1983) Topographic reorganization of somatosensory cortical area 3b and 1 in adult monkeys following restricted deafferentation. Neurosci 8:33–55.

Merzenich MM, Kaas JH, Wall JT, Sur M, Nelson RJ, and Fellman DJ (1983) Progression of change following median nerve section in the cortical representation of the hand in areas 3b and 1 in adult owl and squirrel monkeys. Neuroscience 10:639–65.

Merzenich MM, Nelson RJ, Stryker MP, Cynader MS, Schoppmann A, Zook JM (1984) Somatosensory cortical map changes following digit amputation in adult monkeys. J Comp Neurol 224:591–605.

Merzenich MM, Sameshima K (1993) Cortical plasticity and memory. Curr Opin Neurobiol 3:187–96.

Nudo RJ, Milliken GW, Jenkins WM, Merzenich MM (1995) Use-dependent alterations of movement representations in primary motor cortex of adult squirrel monkeys. J Neurosci 16:785–807.

Recanzone GH, Merzenich MM, Jenkins WM, Grajski KA, Dinse HA (1992) Topographic reorganization of the hand representational zone in cortical area 3b paralleling improvements in frequency discrimination performance. J Neurophysiol 67:1031–56.

Recanzone GH, Merzenich MM, Schreiner CS (1992) Changes in the distributed temporal response properties of SI cortical neurons reflect improvements in performance on a temporally-based tactile discrimination task. J Neurophysiol 67:1071–91.

Recanzone GH, Schreiner CE, Merzenich MM (1993) Plasticity in the frequency representation of primary auditory cortes following discrimination training in adult owl monkeys. J Neurosci 13:87–103.

Wall JT, Kaas JH, Sur M, Nelson RJ, Felleman DJ, Merzenich MM (1986) Functional organization in somatosensory cortical areas 3b and 1 of adult monkeys after median nerve repair: Possible relationships to sensory recovery in humans. J Neurosci 6:218–33.

Wang X, Merzenich MM, Sameshima K, Jenkins WM (1995) Remodelling of hand representation in adult cortex determined by timing of tactile stimulation. Nature 378:71–5.

Xerri C, Coq JO, Merzenich MM, Jenkins WM (1996) Experience-induced plasticity of cutaneous maps in the primary somatosensory cortex of adult monkeys and rats. J Physiol 90:277–87.

Further Insights into Brain Plasticity-Refined Neurological “Representations”; Controlling the “Genie”; Plasticity across the Life Span; Reversible Plasticity; Correcting Impaired Animal Brains

Bao S, Chan VT, Merzenich MM (2001) Cortical remodeling induced by dopaminemediated ventral; tegmental activity. Nature 412:79–83;

Bao S, Chan VT, Zhang LI, Merzenich MM (2003) Suppression of cortical representation through backward conditioning. Proc Natl Acad Sci USA 100: 1405–1408.

Bao S, Chang EF, Davis JD, Gobeske KT, Merzenich MM (2003) Progressive degradation and subsequent refinement of acoustic representations in the adult auditory cortex. J Neurosci 23:10765–75.

Bao S, Chang EF, Woods, J, Merzenich MM (2004) Temporal plasticity in the primary auditory cortex induced by operant perceptual learning. Nat Neurosci 9:974–81.

Chang EF, Merzenich MM (2003) Environmental noise retards auditory cortical development. Science 300:498–502.

DeCharms RC, Merzenich MM (1996) Primary cortical representation of sounds by the coordination of action potential timing. Nature 381:610–13.

De Villers-Sidani E, Chang EF, Bao S, Merzenich MM (2007) Critical period window for spectral tuning defined in the primary auditory cortex (A1) in the rat. J Neurosci 27:180–9.

De Villers-Sidani E, Simpson KL, Lu YF, Lin RC, Merzenich MM (2008) Manipulating critical period closure across different sectors of the primary auditory cortex. Nat Neurosci 11:957–65.

Froemke RC, Merzenich MM, Schreiner (2007) A synaptic memory trace for cortical receptive field plasticity. Nature 450:425–9.

Kenet T, Froemke RC, Schreiner CE, Pessah IN, Merzenich MM (2007) Perinatal exposure to a noncoplanar polychlorinated biphenyl alters tonotopy, receptive fields, and plasticity in rat primary auditory cortex. Proc Natl Acad Sci USA 104:7646–51.

Kilgard MP, Merzenich MM (1998) Cortical map reorganization enabled by nucleus basalis activity. Science 279:1714–18.

Kilgard MP, Merzenich MM (1998) Plasticity of temporal information processing in the primary auditory cortex. Nature Neurosci 1:727–31.

Kilgard MP, Merzenich MM. (2002) Order-sensitive plasticity in adult primary auditory cortex. Proc Natl Acad Sci USA 99:3205–9.

Polley DB, Heiser MA, Blake DT, Schreiner CE, Merzenich MM (2004) Associative learning shapes the neural code for stimulus magnitude in primary auditory cortex. Proc Natl Acad Sci USA 101:16351–6.

Polley DB, Steinberg EE, Merzenich MM (2006) Perceptual learning directs auditory cortical map reorganization through top-down influences. J Neurosci 26:4970–82.

Strata F, Coq JO, Byl N, Merzenich MM (2004) Effects of sensorimotor restriction and axoxia on gait and motor cortex organization: implications for a rodent model of cerebral palsy. Neurosci 19:141–56.

Strata F, del Polyi AR, Bonham BH, Chang EF, Liu RC, Nakahara H, Merzenich MM (2005) Perinatal anoxia degrades auditory system function in rats. Proc Natl Acad Sci USA 102:19156–61.

Wang X, Merzenich MM, Beitel R, Schreiner CE (1995) Representation of a speciesspecific vocalization in the primary auditory cortex of the common marmoset: Temporal and spectral characteristics. J Neurophysiol 74:1685–1706.

Xerri C, Merzenich MM, Peterson BE, Jenkins WM (1998) Plasticity of primary somatosensory cortex representation paralleling sensorimotor skill recovery from stroke in adult owl and squirrel monkeys. J Neurophysiol 79:2119–48.

Zhang LI, Bao S, Merzenich MM. (2001) Persistent and specific influences of early acoustic environments on primary auditory cortex. Nature Neurosci. 4:1123–30.

Zhang LI, Bao S, Merzenich MM (2002) Disruption of primary auditory cortex by synchronous auditory inputs during a critical period. Proc Natl Acad Sci USA 99:2309–14.

Zhou X, Merzenich MM (2007) Intensive trainng in adults refines A1 representations degraded in an early postnatal critical period. Proc Natl Acad Sci USA 104:15935–40.

Zhou X, Merzenich MM (2008) Enduring effects of early structured noise exposure on temporal modulation in the primary auditory cortex. Proc Natl Acad Sci USA 105:4423–8.

Brain Plasticity-Based Therapeutics

Byl NN, Merzenich MM, Jenkins WM (1996) A primate genesis model of focal dystonia and repetitive strain injury. Neurology 47:508–20.

Fisher M, Holland C, Merzenich MM, & Vinogradov S (2009) Using neuroplasticity based auditory training to improve verbal memory in schizophrenia. Am J Psychiat 166:805–11.

Mahncke HW, Bronstone A, Merzenich MM (2006) Brain plasticity and functional losses in the aged: scientific bases for a novel intervention. Prog Brain Res 157:81–109.

Merzenich MM, Jenkins WM (1995) Cortical Plasticity, Learning and Learning Dysfunction. In: Maturational Windows and Adult Cortical Plasticity. B. Julesz and I. Kovacs, eds., Addison-Wesley, New York, pp. 247–272.

Merzenich MM, Jenkins WM, Johnston P, Schreiner C, Miller SL, Tallal P (1996) Temporal processing deficits of language-learning impaired children ameliorated by training. Science 271:71–81.

Merzenich MM, Miller S, Jenkins W, Saunders G, Protopapas A, Peterson B, Tallal P (1998) Amelioration of the acoustic reception and speech reception deficits underlying language-based learning impairments. In: Basic Neural Mechanisms in Cognition and Language. C. v Euler ed., Elsevier, Amsterdam, pp. 143–72.

Merzenich MM, Schreiner CS, Jenkins WM, Wang X (1993) Neural mechanisms underlying temporal integration, segmentation, and input sequence representation: Some implications for the origin of learning disabilities. Ann NY Acad Sci 682:1–22.

Merzenich, MM, Tallal P, Peterson B, Miller SL, Jenkins WM (1998) Some neurological principles relevant to the origins of—and the cortical plasticity based remediation of—language learning impairments. In: Neuroplasticity: Building a Bridge from the Laboratory to the Clinic. J. Grafman and Y. Cristen, eds., Springer-Verlag, New York, pp. 169–87.

Nagarajan S, Mahncke H, Salz T, Tallal P, Roberts T, Merzenich MM (1999) Cortical auditory signal processing in poor readers. Proc Natl Acad Sci USA 96: 6483–6488.

Tallal P, Miller SL, Bedi G, Byma G, Wang X, Nagarajan SS, Schreiner C, Jenkins WM, Merzenich MM (1996) Acoustically modified speech improves language comprehension in language-learning impaired children. Science 271:81–4.

Temple E, Deutsch GK, Poldrack RA, Miller SL, Tallal P, Merzenich MM, Gabrieli JD (2003) Neural deficits in children with dyslexia ameliorated by behavioral remediation: Evidence from functional MRI. Proc Natl Acad Sci USA 100:2860–5.

Wright B, Lombardino LJ, King WM, Puranik CS, Leonard CM, Merzenich MM (1997) Deficits in auditory temporal and spectral resolution in language-impaired children. Nature 387:176–7.

¹He was rewarded for this invention with a $300 bonus and a “holiday” ride in the Captain’s quarters 100 miles down the Columbia River in a newly launched light aircraft carrier.

²After he had delivered a formal lecture, a member of a scientific audience once asked Rose the kind of question he hated (and refused) to answer: “What, Dr. Rose, is your model [that you would apply to explain your data]?” Rose believed that an extended description of data in the form of an abstraction represented by a model was improper. “My model is Jesus Christ,” he responded, with a delightful impish grin. He had nothing more to say.

³One of Woolsey’s protégés, Dr. Wally Welker, had earlier shown that there was a complete representation of the body surface in cortical area 3b, one of the three cytoarchitectonic subfields of S1, in the prosimian galago.

⁴Several dozen other scientists and engineers also made important contributions to this project.

⁵We did not realize that one “answer” represented a basis for implant failure. We had developed implantable connectors (rubberized, and sealed under very high pressures) modeled after under-sea connectors used in transocean marine and other saltwater cables, to provide a strategy for replacing failed electronics. Unfortunately, these implanted connectors failed in human application because of salt deposits that formed around the very closely spaced leads; this “sophisticated” solution to “assuring” life-long, undisturbed electrode array implantation had to be abandoned.

⁶When I decided to join forces with Robin Michelson and work on practical issues related to developing a practical speech-encoding cochlear implant, I called Vernon Mountcastle and informed him of my decision. He told me, emphatically, not to do it. “You have the capability of being a world-class scientist. This would be a distraction, and will be destructive to your career.”

Fortunately, he was wrong. When you do look at issues that are fundamental to your science in a completely fresh way (the cochlear implant provided a wonderful opportunity to test longstanding principles of auditory coding and brain organization, and rapidly turned many of them on their head), you have an enormous opportunity to move that edge of the known forward.

⁷We later realized that we had conducted another version of a historic study conducted in the 1920s by Karl Lashley. He had repeatedly mapped the motor cortex in an adult monkey using surface-stimulation procedures, discovering that the map was unequivocally different (the evoked movement was around another joint) if several weeks intervened between successive maps. This study provided the basis for his positing the principle of “cortical equipotentiality.”

Randolph Nudo later directly repeated Lashley’s experiments in my laboratory using modern intracortical microstimulation methods, and again documented large-scale variations in motor maps recorded in successive “maps” obtained over a several-month-long period.

⁸To double-check this conclusion, I located several aged monkeys early in this experimental series and found that their plasticity was little different from that recorded in vigorous young adults.

⁹The large training-driven improvements in the monkey’s vibratory frequency discrimination abilities were accounted for by a sharpening of temporal coordination of evoked spiking activity in the engaged cortical networks—in the first case, expressed across a single, very large cortical column, and in the second case, by an equivalent increase in coordination for neurons within several hundred cortical columns representing the same skin zone in highly resolved detail.

¹⁰At the time of this writing (2010), more than 4 million mostly struggling children in nearly 50 countries have benefited from the use of the brain-plasticity-based Fast ForWord training programs.

John Wilson Moore

BORN:

Winston-Salem, North Carolina

November 1, 1920

EDUCATION:

Davidson College, B.S. Physics (1941)

University of Virginia, Ph.D. Physics (1945)

APPOINTMENTS:

Radio Corporation of America Laboratories (1945–1946)

Assistant Professor of Physics, Medical College of Virginia (1946–1950)

Biophysicist, Naval Medical Research Institute (1950–1954)

Associate Chief, Laboratory of Biophysics, NINDB, NIH (1954–1961)

Professor of Physiology & Pharmacology, Duke University (1961–1988)

Professor of Neurobiology, Duke University (1988–1990)

Professor Emeritus of Neurobiology, Duke University (1990–present)

HONORS AND AWARDS (SELECTED):

Dupont Fellowship, University of Virginia (1941–1945)

Fellow: National Neurological Research Foundation for Scientists (1961)

Biophysical Society, Council and Executive Board (1966–1969; 1977–1979)

Biomedical Engineering Society, Board of Directors (1971–1975)

Trustee and Executive Committee, Marine Biological Laboratory (1971–1979; 1981–1985)

K. S. Cole Award, Biophysical Society (1981)

Fight for Sight Citation for Achievement in Basic Research (1982)

John Wilson Moore initially became known for elucidating the action of tetrodotoxin and other neurotoxins using his innovative sucrose gap method for voltage clamping squid axon. He also was a pioneer in the nascent area of computational neuroscience, using computer simulations in parallel with experiments to predict experimental results and thus validate the concepts used in modeling. Intrigued by the possibility of applying his knowledge of physics to learn how neurons employ electricity to generate and transmit signals, he led the field in exploring how ion channels and neuronal morphology affect excitation and signal propagation. He developed electronic instrumentation of high precision for electrophysiology, the result of experience gained through an unconventional career path: early training in physics, assignments involving feedback in the Manhattan Project, and learning principles of operational amplifiers at the RCA Laboratories. His summers at the Marine Biological Laboratory in Woods Hole, MA, now exceeding 50, made much of his work possible and established the MBL as his intellectual home. In retirement, he developed the educational software Neurons in Action, coauthored with his wife Ann Stuart, that is now widely used as a learning tool in neurophysiology.

John Wilson Moore

“I want to know about your life before me,” said Annie, my beloved wife and colleague of the past 35 years. We are obviously different in age, and she did not know about my life before the 1970s. And so I began telling her what I remember, usually on Saturday evenings. Sitting beside me with her MacBook, she typed as I talked. Her questions have drawn buried memories to the surface, causing neurons to fire that had for some time been quiescent. It has been great fun for us both. Thus, when Larry Squire so graciously invited me to write my autobiography, I had a considerable start. Here I attempt to encapsulate my career by recalling some of the events and people that influenced it and the collaborations that I have greatly enjoyed, both before and after Annie joined me.

1920–1937: Growing up

I was the oldest son of a feisty, overworked mother and a demanding, workaholic, educator father. We kids liked to say, “Dad might be the salt of the earth, but Mom was surely the pepper!” I adored my mother and came to deeply respect my father, a man of the highest integrity. Mother, a tiny, redhaired ball of fire, and interested in everyone but herself, was focused for most of her life on tending Dad, us four kids, and visiting missionaries and teachers. She longed for vacations at the coast but Dad would never consider such a frivolous waste of time! As high school principal, then superintendent, in Winston-Salem, North Carolina, he was too occupied with daily school crises during the academic year itself, while during the summers he felt that every day was precious for finding and hiring the best teachers and preparing for the fall. Only after Dad’s death, relieved of her duties, did Mom’s spirit soar, and well I remember her flirting with a med student even on her death bed. Mom finally saw the ocean when she was able to visit me in Woods Hole after Dad died.

After serving in the Cavalry during World War I, Dad became the math teacher at the Winston-Salem High School. He believed in the importance of sports as a complement to classroom learning, initiating both football and basketball in the high school and coaching both teams to play their best, but always fairly. Dad loved teaching, but he was advanced to principal because of his integrity and dedication to education. Then, fortunately for me personally, Dad was promoted from principal to superintendent just before I entered the high school. Several of his former students became members of the school board and supported him strongly as he strove to improve the quality of all schools, black as well as white. His devotion to the school system was recognized by having a new school built and named after him. Dad, as Superintendent of Schools, partnered with his friend Terry Sanford, at that time the NC governor, in locating the now famous North Carolina School of the Arts in Winston-Salem.

Both Mom and Dad, improbably, were children of missionaries assigned to the same Presbyterian mission station in Kobe, Japan, although they did not grow up in Kobe together. Both were brought to the United States by their parents at the age of 7, my dad to be raised by his grandfather in North Carolina after his mother had died in Japan, and my mother to live with a foster family in South Carolina. Perhaps their shared unhappiness at having been abandoned by their parents helped draw them together as adults. Dad’s grandfather, John Wilson Moore (for whom I was named), was truly a remarkable person, a self-educated farmer who brought up all of his children to become professionals: two physicians and two preachers. One of the preachers and Dad received honorary degrees from Davidson College at the same time.

In Winston-Salem we lived in a little house with a huge backyard graced by many tall, beautiful oaks. Upstairs there was a miniature apartment typically occupied either by missionary relatives on sabbatical or by teachers who were renting it for room and board. When we four kids were small, we were pushed into the unheated sleeping porch upstairs because the missionaries and the teachers got the bedrooms. I recall our little house often beset by missionary relatives, mostly Dad’s, who were used to having servants in Japan, so when they visited us they just sat around being waited on by Mom. She was rightfully quite resentful of these annoying relatives who would stay for a week to a month.

I had been born with a short left leg and a club foot with only four toes. Despite this, Dad thought I should work hard and continuously on family duties. From an early age until I went to college, it was my job to shovel the coal into the furnace in the spooky basement and care for chickens. Behind the house was plenty of room for the eight chicken houses, where roughly 100 of Dad’s premium breed, White Wyandotte chickens, lived. When I was about 5 years old, I began my assigned chicken chores: watering, feeding, and cleaning the droppings. The droppings provided fertilizer for the garden, which I was also assigned to tend. Once a year Dad showed and sold his prize-winning chickens at fairs. Prior to the showing, there was the ritual of chicken washing. Everyone from the family participated (often without Dad). Imagine dunking dozens of squawking, flapping chickens in a tub of water, soaping them to get the oil off, putting them in a bluing solution to make them more intensely white, rinsing and drying them, and placing them in shipping crates where they could not get dirty! Annie asks if I didn’t resent the hard work. Of course I did! My social life was almost nonexistent. But my father was a man of such integrity and good will that I came to realize he was trying to do what he thought was best for me. I am proud of the man he was and what he accomplished.

1937–1941: Davidson College

Since Dad was a teacher, and we were a family of four children, he did not have the money to send me to an elite college. Besides, there was no question as to choice; it had to be little Davidson College where Grandpa, Dad, and others in the family had been educated. As a teacher, Dad got a discount on my tuition; in addition, because of my club foot, enterprising Dad obtained a North Carolina state grant intended to help disabled kids to go to college. With these sources of help, Dad was able to pay for my room and tuition for all 4 years. I earned my board separately, however, by waiting tables in a boarding house.

These boarding houses were in a sense like fraternities. Although there actually were small frat houses on campus, neither I nor my friends were interested in this sort of life centered on parties and drinking. My hardworking friends all did quite well in their lives. Although two of my best friends died in World War II, our class turned out two college presidents, a seminary president, and the dean of Yale Divinity School. One friend, John McLucas, deserves particular mention. With training in physics and business, John eventually became the undersecretary of the Air Force who pushed for the drone surveillance aircraft; he was on the boards of a number of high-tech corporations and had a satellite named after him! When he and I met at a recent Davidson reunion and swapped stories about what we had been doing, his remark was, “Well I thought you were going to make more of yourself John—why don’t you do something important?”

Starting in my sophomore year, I also earned money as a T.A. and by running the gym, but only after I had proved myself. As an entering freshmen I was small and wimpy despite my years of shoveling coal! I admired the muscle-bound senior running the gym and devoted myself to gymnastics, receiving the award for the most physical development at the end of my freshman year. As a sophomore I replaced my muscle-bound senior friend, managing the gym and being in charge of physical education for freshman for the other 3 years of college—and getting paid for it. I most enjoyed the horizontal and parallel bars. I loved the sensation of using the momentum of the body at precisely the right moment to be able to execute a handstand, or a backward or forward roll: it was exhilarating and gratifying. I even organized a half-time gymnastics demo at a basketball game. I also wrestled, enjoying the gracefulness of the sport. Even with a club foot I was able to enjoy athletics and develop the muscles that have kept me strong and active all my life; for example, I became a windsurfer at age 60, windsurfed the 10 miles from Woods Hole to Martha’s Vineyard and back, and only stopped this exhilarating sport at age 80!

Inspired by excellent Davidson professors, I became deeply interested in physics. Perhaps in the back of my mind I was considering becoming a professor, since it was clear that my math and physics teachers at Davidson enjoyed what they were doing. Professors Mebane and McGavock in particular had been my favorites. Both of them welcomed students to their homes and enjoyed the company of their students. In my freshman year, Mebane, the math teacher, standing in as a physics teacher for the regular professor on sabbatical, had to learn physics along with the students and in doing this provided one of the best learning experiences I had at Davidson. He was usually only one week or even one lecture ahead of the class, exciting for both professor and students. First, the professor could see the kind of problems the students would encounter since he was learning the material de novo as we were. Second, students and professor attempted to outwit each other, a game that Mebane relished. When I told Davidson President Bobby Vagt about this experience at my class’s 60th reunion, Vagt was fascinated and suggested that he should shake up the teaching assignments of his faculty more often.

Bill McGavock taught differential equations. Because there were only three students (myself, Pat Hobson, and John McLucas) in this class, we met in his office. Most memorable for me from this class was that there was no sure path that you could follow and know that you would get a solution. McGavock told his students to assume a solution and see if you could find a fit. But this was very unsatisfactory to me: what if we didn’t know what to assume? When analog computers became available later, they seemed to me a terrific advance for understanding math. After I had used an analog computer to solve differential equations, I could actually see the individual variables of acceleration, velocity, and position change with time and yet their sum was always the same. Would that I had had a graphics calculator as present-day students do.

In my senior year I did a small project for Professor Henry Fulcher on the viscosity of oils—his one research idea for which he had equipment. How different it is today to return to Davidson and see the well-equipped labs with professors who publish, along with their students, in premier journals.

It was 1941 when I graduated. Europe was torn by war. Many of my classmates had competed ROTC in college and would soon be off to war, but my foot deformity excluded me from ROTC and military service. Having fallen in love with the elegance of physics, I decided to go on to graduate school in this discipline. Little did I realize that as a physics graduate student I would be very much involved in the war effort.

1941–1945: Graduate School in Physics during World War II

In September 1941, I entered graduate school in physics at the University of Virginia. There I joined John Reisner, a Phi Beta Kappa scholar who had been 2 years ahead of me at Davidson. His stellar performance at UVA must have been the reason that I was admitted there, sight unseen, even with a fellowship! John invited me to be his roommate and became my closest friend, constant companion, and mentor throughout my years at UVA. From UVA he went to RCA, joined the program to refine the electron optics for their electron microscope, and had an illustrious career there. Perhaps, then, it is not a coincidence that I also moved to RCA after completing my degree, and I remain happily indebted to him to this day.

New graduate students took a required course in machine shop as well as courses in physics; it was necessary to know from practical experience in the shop just what could and could not be made there. I had just gotten started when Pearl Harbor was bombed on Sunday, December 7. On Monday morning there was a barbed wire fence around the physics building and military guards at the door! At that point we new students learned that a small group in the Physics Department had been working on isotope separation for the war effort.

To get into the building, each student now had to be screened. There were secretaries at the entrance interviewing and filling out a detailed history for each student. My family has heard me often recount this amusing moment in my life:

Secretary: “Name of father and place of birth?”

John: “John Watson Moore; Kobe, Japan.”

The startled secretary looks at me, shakes her head sadly, and says she doesn’t think I will get in. I explain that my father is the son of a Presbyterian missionary to Japan. She relents a bit—well maybe. Next question:

Secretary: “Name of mother and place of birth?”

John: “Marjorie McAlpine; Kobe, Japan.”

Secretary: “That does it.”

She grabs the piece of paper and rips it out of the typewriter saying, “You’ll never make it!” But after an explanation to higher authorities I was not only given clearance to enter the building but, in time, clearance to work on highly secret projects. Only gradually were we informed that our Physics Lab at the University of Virginia was one of several groups in the top secret Manhattan Project that were attempting to make a nuclear bomb before the Germans. The head of our group was Jesse Beams, who was trying to separate U-235, the radioactive isotope of uranium, from U-238 using centrifugation as the separation technique. Separating out the U-235 was absolutely critical for the building of the atomic bomb. We later learned that there were other locations where isotope separation by diffusion was being tested: the Naval Research Lab (Washington, D.C.) and a new Oak Ridge National Lab (Oak Ridge, TN). After December 7, classes became secondary and work toward the war effort became the primary focus of the students.

The Giant Centrifuge

By the beginning of 1942, the whole department was fully engaged with designing and building a huge centrifuge with its required ancillary equipment. Uranium was to be centrifuged in the gaseous state, uranium hexafluoride. It was to be passed through a vertical inflow tube into a huge, revolving, vertical aluminum tube (this centrifuge was about 10 inches in diameter and 10 feet or more in length). In this way the gas would be exposed to a strong acceleration so the heavier U-238 particles would spin to the outside of the tube and the lighter U-235 particles would stay near the center. Concentric exit plumbing was required at the bottom of the cylinder to collect the separated U-235 and U-238.

Together the graduate students and professors faced a number of problems in this crucial effort. Since we were dealing with a small difference in weight (3 parts in 238), separation presented a real challenge. Clearly we had to spin the tube as fast as possible without breaking it in order to get separation of the isotopes. The extraordinary machinery needed to effect the separation was large and complex. Fortunately the physics building had a special, safe place for it, a tower for a Foucault Pendulum (a pendulum suspended from a high place that demonstrates the rotation of the earth by exhibiting a change in its plane of oscillation with respect to the floor). The tower was three stories high and, best of all, was built with thick stone walls in the solid manner of the 19th century. All of the students were pressed into the job of stripping the pendulum out of the tower and, with steel angle iron, acetylene torches, and arc welding, building a frame to hold the huge centrifuge tube, made in the physics shop. In the course of this labor I had to learn both kinds of welding. I attribute much of my fondness for “hanging out” with skilled laborers today to such projects in my early life that required me to learn, understand, and respect the truly professional skills involved in construction.

What supplied the power to turn this huge centrifuge tube? Our team decided that a steam turbine would be best because an electric motor would fall apart before it could spin the tube at high enough speeds. The plan was to build a turbine driven by high pressure steam supplied by the campus steam generator, a building 200–300 yards away from the physics building. As the construction of the centrifuge was proceeding in the tower, the university laid large, high-pressure steam pipes to the tower despite the long distance. The graduate students did the plumbing inside because the workmen doing the external piping did not have security clearance and were not allowed in the building. There must have been a booster in the building itself because it was necessary to have immediate, high steam pressure upon opening the valve, both to get the centrifuge going and then to keep it accelerating through certain resonant frequencies. If the centrifuge’s spinning had remained even for a moment at these resonant frequencies, the assembly would have wobbled and probably been destroyed.

It was necessary, then, to know where the resonant frequencies occurred so that extra steam pressure could be supplied as the spinning tube approached them during its acceleration in order to overcome the potentially dangerous resonance. No electronic devices were yet available to measure frequency. However, it turned out that the physics department had an excellent frequency meter, piano-playing Professor Snoddy, who was blessed with perfect pitch! He was consequently given the duty of manning the steam valve, a wheel (imagine a small ship’s wheel) that one turned in order to deliver more or less steam to the turbine. He would open the valve to let in steam to start the tube spinning, then, listening to the frequency of the sound made by the accelerating tube, begin to close the valve at a point just below the resonant frequency. By partially closing the valve he could let steam pressure build up. Then, by suddenly opening it again (imagine the wheel being furiously turned in one direction, then the other), he could supply a burst of steam to push the centrifuge through the resonant frequency. Since there were several harmonic frequencies as the tube spun faster and faster, this task had to be repeated during any one separation run; it required considerable skill and focused attention and was critical for the smooth operation of the device.

In 1942, as we were constructing the centrifuge and its plumbing, a young guy, Edward P. Ney, arrived with a mysterious new instrument called a mass spectrometer. This marvelous machine was to measure the ratio of the isotopes for each run of our centrifuge in order to evaluate the quality of the run; it turned out to be a special mass spectrometer just designed and built specifically for this purpose by Alfred O. Nier at the University of Minnesota. Nier was playing an important role in the Manhattan Project: as a pioneer in mass spectrometry, he had provided crucial samples of U-235 to the Uranium Committee, a tiny one that was used to show that this isotope, not U-238, was responsible for nuclear fission and then a larger sample requiring our newcomer Ney (along with another undergraduate student) to keep a mass spectrometer going 24 hours a day for 3 months! Nier’s instruments became key in measuring the enrichment of uranium produced by the different separation methods under development at Oak Ridge, Columbia University, the Naval Research Laboratory, and our department at the University of Virginia.

I enjoyed interacting with Ed Ney, who had been assigned to bring us our designated mass spectrometer and make it work. Ed’s remarkable intellect, and his level of understanding through his work with Nier, led me to think at first that he was already a Ph.D. although he only had a B.S. As well as being the mass spectrometer specialist for the Manhattan Project, he joined our graduate program and upon his graduation was immediately offered an Assistant Professor position in our physics department. However, he returned to Minnesota and had a fabulous career in astrophysics recounted in his online obituary; for example, he flew the first space science experiment on NASA’s manned flight Gemini 5.

Although our centrifuge was promising as a pilot model, the development of a production facility for it in New Jersey did not go well; the Manhattan Project’s General Groves visited and closed our program in 1944. The diffusion method of separation at Oak Ridge was used to make the bomb. Nevertheless, centrifugation seems now to have become the standard tool for uranium isotope separation: think Iran.

The Naval Project: An Automated Target Tracker

In the Pacific, the Navy was having great difficulty in shooting down kamikaze aircraft with manually aimed gun directors linked to the anti-aircraft guns. The operator, on the deck of a rolling and pitching ship, had to attempt to keep the aircraft in his binoculars’ field of view while trying to estimate where he thought the plane would be when the fired shell arrived there. The Navy shipped one of these massive and unwieldy gun directors to us so that we could experience their problems; the director was weighed down with the inertia of its synchronizing motors necessary to direct the gun and also was itself armored. Success in hitting the aircraft probably depended more on luck than skill, and certainly not on technology. Furthermore, the operator was in an extremely vulnerable position on deck. Thus, the mission for the UVA physics department was to build an automatic gun director using a new invention, a radar dish.

The department received one of the first of these highly secret radar dishes and the electronics to go with it. To develop and test the desired system, we physics students first needed to build a gimbaled 16 ft by 16 ft steel platform in the “backyard” of the physics building. We then had to employ oil-pressure-driven hydraulic motors, such as those used today in cranes, for moving the platform to mimic the rolling and pitching of the ship’s deck. Similar hydraulic controls were used to move the super-secret radar dish now mounted on this virtual deck. (I commend whoever chose such an acronym, an easily remembered palindrome, for RAdio Detection And Ranging).

This new project required that we students learn about servo (feedback) systems as well as how to build the electronic circuits that would determine any deviation of the axis of the radar dish from pointing directly at the plane. Any error in pointing had to be sent to the hydraulic control system to move the dish so that the error was minimized. Indeed, we accomplished our goal, first with the gun on a steady deck with a fixed target, and then with a Piper Cub piloted by one of our students. Now we had to build a circuit that would calculate the “lead angle”—the position where the moving plane would be after the time taken to fire the shell plus the time of the shell’s flight to meet the plane. After working out the problems in tracking a small plane in flight, we found that when the “deck” was in full motion, the tracking was almost as good.

We were rather surprised and gratified that we were able build an automatic gun director even with the target being such a small plane having so little radar reflection signal. We proclaimed that our invention worked and so the system was passed on to the government for development. This was my first work with servo systems.

Finally My Dissertation: My First “Clamp”

I had started graduate school with a project to develop magnetic suspension for a centrifuge and finally, with the war over, I was able to finish it. My project was to suspend a small steel ball magnetically in a vacuum to minimize friction and then spin it to very high speeds. How fast could you spin the steel ball bearing until it broke apart? (I was behind a barricade for these experiments!) I used a light beam with a photocell to measure the vertical position of the ball in a glass tube and a feedback system to maintain the ball at a chosen level by adjusting the magnetic field—a “position clamp.” To measure the speed of rotation, a second photocell detected with each rotation a flick of dark from a small ink stripe on the side of the ball. I was able to spin balls at up to 108 G before they exploded—100 million times greater than earth’s gravitational force. Working like this with the concept of negative feedback, as in the gun director project, prepared me for my important year to come with Art Vance; indeed, the concept of stable control through negative feedback became central in my future life in research.

During graduate school I had met and married Natalie (Lee) Bayless, who later got her doctorate in biology, focusing on electron microscopy. With my thesis finished, we left for Princeton, New Jersey, where I had taken a job at RCA.

1945–1946: The Year at RCA That Changed My Thinking

Art Vance, Extraordinary Mentor and Master Engineer

At the RCA, where I did the equivalent of a postdoc, I was assigned to the group headed by Art Vance, the inventor of the operational amplifier and analog computer. I was put on relatively minor jobs of calculations for sending up a missile with a payload, but mainly I was learning as Art Vance took me under his wing. Vance was the second of two big, gentle guys who had gone out of their way to help me. The first was a shop foreman in a woodworking mill where I was an apprentice during one of my high school summers. This kindly man with huge Popeye arms would not only show me what to do but would adjust the jobs to my strength so that I always felt competent and useful. He protected me from socializing with the older guys who were coarse and “spat chewin’ tabacca.”

Vance was brilliant and inventive, yet his common sense was dominating. Among his most important inventions was an extremely constant, roughly 100KV voltage supply which was absolutely required for the stable functioning of RCA’s new product, the electron microscope (EM). At this point RCA was the only company making EMs, in part because Vance was the only person in the world competent to make the requisitely stable power supply. RCA was quite proud of this product; it set RCA apart from other electronics companies. Vance also was a pioneer in loudspeakers and sound canceling. He described his imaginary “father’s Sunday morning quiet box” that he planned would come down around his chair, complete with light and newspaper inside, and have microphones to pick up the kids’ sounds and cancel them with external loudspeakers (think current noise-canceling headphones). It was these sorts of conversations with Vance and the engineers around him, in the big room with about 10 desks, that made RCA such a special place.

The Operational Amplifier

Of all of Vance’s inventions, the most far-reaching and important was negative feedback and the operational amplifier. With “op-amps” it was possible to carry out precise mathematical operations: addition, subtraction, integration, and differentiation.

To demonstrate the power of an appropriately connected array of op-amps, Vance’s lab constructed a 10 x 10 array to solve 10 simultaneous equations. RCA’s marketing arm, naturally wondering who would possibly find such a device useful, offered a prize to any RCA department for the most useful problem the array could solve. Who won?—the accounting department with the question “How much money should we assign to each of 10 different categories of income and expenditure to minimize the tax we pay?” To my knowledge the device was never marketed. Interestingly, the present-day artificial neural networks closely resemble this matrix equation solver—they are built on the same principles.

Vance combined the op-amp with another of his inventions, a high-speed electronic multiplier that used loudspeaker coils to oscillate light metal foils, allowing it to be orders of magnitude faster than the inertia-loaded electromechanical multiplier. In the early 1940s there was hope that these devices could be used in the war effort. Buzz bombs directed toward London presented a special problem. They were so fast that the ram jet motor “buzzed” like a bee. It was impossible to track these bombs with conventional tracking devices designed to follow far slower aircraft. Vance used his new tools to make a tracker that was orders of magnitude faster than anything else available at the time. Although tests in London showed that it could actually track the bombs, the device was not actually used in the war because the equipment needed to intercept the bombs had not yet been developed.

Vance helped me rearrange my mindset so that I would think in terms of currents, which then allowed me to understand how op-amps could be used in biophysics and was crucial to my future work. I had learned about capacitors in physics in terms of the static ratio of voltage to charge (difficult to measure) but had not thought about capacitors from a dynamic point of view, where the capacitor determines the rate of change of the voltage. So now I thought of the current flowing into and out of a capacitor and completely ignored static charge considerations. It is interesting that this small difference in point of view was essential to my understanding of operational amplifiers: with op-amps the currents must sum to zero, so one always looks at the currents rather than the charge.

Later, at Duke, I developed a course with extensive notes on the use of op-amps to make precise analog instruments for a wide variety of needs. When digital logic devices came along, I extended the notes to show how op-amps could be connected to become digital logic elements, revealing the theoretical possibility of designing digital computers from analog devices! My students were enthralled and enthusiastically designed their own circuits. I printed two volumes of paperbound notes and wish I had published what I still consider exciting insights.

Applying the Op-Amp to Physiology

A few years later (1952), after I had entered the field of biophysics, this new understanding of capacitance was crucial in my immediately grasping the Hodgkin-Huxley (HH) equations, written in terms of currents. Since I had been schooled by Vance, it seemed natural to me to look at the equations this way and it was immediately obvious to me that the HH equations would be easily solvable on an analog computer.

Later, when I was using op-amps to make voltage clamp circuits for the squid giant axon, I realized that I could use them to improve on the conventional method of measuring membrane currents (previously used by Hodgkin and Huxley). I introduced the current-to-voltage converter, made of a single op-amp with a resistor in the feedback loop. This is by far the simplest, most precise, and most elegant way to measure current. Many innovations were happening in neurophysiology around that time, for example the capacity compensation electrometer, and I was thrilled to contribute the current-to-voltage converter, along with the op-amp voltage clamp circuit.

1946–1950: The Medical College of Virginia

At RCA I was beginning to look for opportunities where I might use physics in a more unique way than by pursuing the engineering or mathematics on which RCA was focused. My wife Lee called my attention to an article about the Medical College of Virginia (MCV) and its forward-looking president, who wanted to begin to incorporate the physical sciences into the teaching and research in his medical school. I actually had been thinking of biology as a possibly interesting area in which to apply my knowledge of physics, so I wrote to the president suggesting myself! Certainly job hunting in science is different now! I visited and was offered a slot primarily teaching physics to pharmacy students.

Because space was at a premium at MCV, only a tiny room and a half was cleaned out for me, and these rooms were in the basement of the library. Here I prepared my lectures and built circuits for my research. I also developed close associations with several deeply interesting, forward-looking, and inspiring colleagues and began applying my physics training to biological problems. One colleague was Bob Ramsey, a smart, fun-loving, superb muscle physiologist whose graduate student and eventual wife, Sibyl Street, had dissected out single muscle fibers on which the two of them did length tension measurements. It was said that Sibyl was the only person in the world who could do this dissection, so Bob had to marry her in order to keep his research going. Like me, Ramsey had a short leg and a limp, so of course I felt this as a bond between us.

Bob had summered at the MBL. He regaled me with stories of the biophysicist Kacy Cole, of sailing, of the fabulous delights of this amazing scientific Mecca. Since he knew that both Kacy and I were interested in electrical measurements of biological tissue, Bob thought that we should get together.

At the MCV I also interacted with George Zur Williams, a pathologist and oncologist. George was on the cutting edge of every one of his interests. As an oncologist, he was a pioneer in the use of radioactive isotopes to attempt to kill cancer cells. I actually helped out at several operations where I monitored the radiation that George was giving a patient. I also measured the flux of radioisotopes across muscle membrane with a jolly, highly respected German muscle physiologist named Ernst Fischer. Ernst had a small grant—almost unheard of at that time—and he was also able to give me some space in his lab. And I published with a dermatological surgeon, Hermann Nachman, who did skin grafts and wanted me to evaluate the quality of the skin by electrical measurements. My electrical impedance measurements of the properties of skin were presented at the meeting of the American Physical Society (APS), where a fateful encounter with Kacy Cole decided my next move and, indeed, the rest of my career. Bob Ramsey had set me up for this crucial meeting.

The Momentous Encounter with Kacy Cole

My APS talk on skin was scheduled as the last talk on the last day of the meeting, probably because the paper was in the “miscellaneous oddballs” session. There were five persons remaining in the room: the previous speaker, the chairman, the projectionist, one tall, lanky unidentified person roughly aged 50 or so with a cigarette hanging from his mouth, and myself. At the end of my talk the chairman uncomfortably asked whether there were any questions and the unidentified person actually asked a good question, revealing considerable knowledge of the topic. I responded: “Under these unusual circumstances would you identify yourself?” And this person responded in his slow drawl, almost as if it were a question: “Ken-neth Cole?”

I certainly knew about Kenneth “Kacy” Cole. From Ramsey I had heard about his adventures sailing Knockabouts in Woods Hole and, most marvelous, that he had crewed on a ship in the Great Lakes and had a sailor’s tattoo, of all things. I had read Kacy’s papers carefully because they presented a unique way of plotting the impedance measurements he had made of the eggs of various sea creatures—in fact I had plotted my data the same way. The notion of being a biophysicist by the sea was a romantic one for this young land-raised Winston-Salem native.

I responded, “Since I have read some of your papers, I can answer accordingly,” and then proceeded with my answer. Evidently the answer was satisfactory because Kacy waited for me to get my slides from the projectionist and we walked out together.

He said, “You know, I am in administrative work now (he was Scientific Director of the Naval Medical Research Institute, the NMRI) and I don’t get to do any lab work anymore.”

I said, “Yes, I had heard that from Bob Ramsey.”

To my surprise he said, “I would like to start my lab up again—would you run it for me?” He was that way—first impressions were terribly important with Kacy.

I replied, “Well, if I were to accept your offer, could we go back to Woods Hole in the summers as you used to do?”

“Hmmmmm...(30-second pause)...OK,” said he.

“I accept,” said I.

From reading his papers I knew this was the sort of thing I was truly interested in, and he needed help. There were not many people available for him to choose from with my training and interests and at the right age! So the symbiotic deal was obvious to both of us and thus it happened very quickly. I had to pass a government service exam (GSA) to get my ranking as a civilian scientist but that was not too difficult. Clearly the Cole-Moore conversation occurred before the days of affirmative action.

1950–1954: The Naval Medical Research Institute

I moved to Washington, D.C., during the next summer (1950). Woods Hole was out of the question this first summer since the lab had to be set up from scratch. All that Kacy had brought with him to the NMRI from his previous institution, the University of Chicago, was his original Wheatstone bridge, made by Hewlett and Packard in their garage, (!) and an oscilloscope. So I designed chambers and bought a microscope; there was a small relay rack holding an oscillator, whose amplitude and frequency you could change, as well as the infamous Wheatstone bridge, a wide range of capacitors and resistors in both fixed and variable values, and the experimental preparation, frog muscle. These were all the tools necessary for impedance measurements.

Measuring the Impedance of Frog Muscle

A new Navy Lieutenant J.G., H. W. (Tony) Shirer, was assigned to work with me. Tony was smart, cheerful, and knowledgeable about electronics and simulations and we both enjoyed our time together at the NMRI. As one of our first endeavors together, Tony and I were able to continuously superfuse a sartorius muscle for more than a month! The muscle was mounted between two plates over which cellophane (from Kacy’s cigarette box wrappers) had been stretched to protect the metal electrodes from degradation due to contact with biological molecules. Water and electrolytes could pass through the cellophane but not the molecules from the tissue. With this chamber we made electrical measurements of impedance, at first over short intervals and then daily for a month. At the end of the month we weren’t sure if the fiber was actually still alive or if we were just measuring the system. So we took out the fiber, stimulated it, and it contracted! By including antibiotics we had made an excellent culture system, but the muscle fiber was really not a good project. The changes in impedance we observed in different solutions were very small and the interpretations were difficult, so we never wrote a paper.

During this time I sat on a biomedical engineering committee of the IEEE (Institute of Electrical and Electronics Engineers) with an inventive engineer named Wilson Greatbatch. In his shed, Wilson had developed the electronics and encapsulation of the first implantable pacemaker. (He licensed it to Medtronics and continued to improve its design and built-in battery; he went on to develop batteries with lifetimes approaching a decade for implanted devices.) He told us that the electrodes in contact with tissue deteriorated with age, a serious problem. Based on my experience with the frog muscle, I suggested cellophane or a similar material. I always wondered whether he took the suggestion and whether our efforts had in some small way aided pacemaker design. When I recently received my own pacemaker, I wrote a letter of thanks to Wilson—who wrote back and sent me a copy of his book describing the extensive materials and tests to achieve long-term durability for implanted electrodes (Greatbatch, 2000).

Detection of Frostbite

At the NMRI was a young officer named Harold (Harry) Meryman, an M.D., who had joined the Navy to avoid going to the Korean War. He was a smart guy, a colorful character, quite sloppy, and therefore rather uncomfortable in the Navy uniform. His uniform tended to get filthy, particularly the white cap. There were inspections, times when all officers and corpsman had to be present and in good form for visiting, high-ranking officers. Meryman would forget about inspections until the last minute—so he would put chalk on his cap with a blackboard eraser. Meryman chose to live in an old abandoned canal-lock operator’s cabin along the Potomac. This way he could live in natural surroundings, with wild animals around him, but close to the lab.

Harry was interested in the use of quick freezing in liquid nitrogen to preserve cells, and their subsequent recovery. I remember him showing me how he had preserved autumn leaves in full color by replacing the water in the leaves with glycerol. In particular he worked on the preservation of blood for transfusion by freezing. Inspired by Harry, I became intrigued with the possibility of freezing a bit of muscle in liquid nitrogen and restoring it to life. I made a tiny frame of Lucite, in the shape of a pipe wrench, so that the frog’s sartorius muscle could be stretched over the top and frozen in glycerol. It worked; the muscle was alive when we warmed it up! One problem: upon warming, it contracted and broke the frame holding it.

An urgent message from the field came to Naval Medical about horrible frostbite in the Korean War: Is there any way you can determine whether soldiers and sailors have frostbite and its depth? By now radar was well developed and Harry and I wondered whether you could see a difference in the reflection of microwaves from normal versus frostbitten tissue. Since we were at a real naval station, we were able to scavenge a microwave generator, a detector, and the necessary waveguides. What would we use as frozen tissue? A piece of prime beef from the officer’s mess was perfect. So we froze the surface in liquid nitrogen, hypothesizing that reflection of the microwaves would not occur until they got to live muscle where there were electrolytes (a conducting surface), and we would then observe a longer delay in the reflection. It worked! We reported the result (Meryman and Moore, 1953) and Harry was immediately shipped to Korea, although the fighting was over before he had a chance to use the method in the field.

Harry continued his experiments with freezing and reviving blood cells in the American Red Cross Lab he established at NMRI. He published a landmark paper for cryopreservation of red blood cells, a method still used around the world to save countless lives. This founder of the field of cryobiology moved on to study transplantation rejection and performed the first experimental human tissue transplant on himself (typical Harry!). He was a truly marvelous guy and friend who died earlier this year before I had time to call and talk with him about my comments here.

Other Experiments and Colleagues at the NMRI

A biochemist named Nachmanson now entered the scene. Despite the beauty and universal acceptance of the HH equations, he was convinced, indeed obsessed, with the idea that acetylcholine was the basis of the propagation of the action potential. Nachmanson went to great lengths to argue with the many experiments that showed otherwise. One experiment was to apply acetylcholinesterase inhibitors to the sciatic nerve to see whether they blocked the action potential. Of course, they didn’t. But Nachmanson then claimed that the inhibitors did not block the action potential because they did not get through the sheath. To many scientists, the Nachmanson idea seemed absolutely ridiculous, but he argued it quite publically and had to be reckoned with continually. I set out to try to squash the idea once and for all.

Here was my plan. Manuel Morales at the NMRI had brought an excellent chemist named Seymour Friess to the Cole lab. I persuaded him to join forces to stop Nachmanson. I had read that you could desheath the sciatic nerve of frogs by pulling off the sheath like a stocking. So Friess, my technician Whitcomb, and I dissected out the sciatic nerve of bullfrogs, measured the velocity of propagation of the action potential, stripped the sheath off, put acetylcholinesterase inhibitors on the nerve, repeated the measurement, then pulled the sheath back up and repeated the measurement once again. There was, of course, no change in the propagation with the inhibitor (Whitcomb et al., 1958). On the way to one of the first International Biophysical Meetings, held in Stockholm, I visited Bernard Katz and told him about my results with the desheathed sciatic nerve. We talked about his scathing review of Nachmanson’s book which had recently come out. How could Nachmanson be so completely backward, arguing that acetylcholine was the basis of nerve propagation but did not work at the synapse (where, of course, it is the neurotransmitter)? Katz was very cordial, a person who did not seem to take himself terribly seriously, and we became good friends.

Next door to our basement lab was the lab of Morales and his student Joe Blum, an extremely energetic, delightful guy who had just come from the University of Chicago. Joe and I would renew our friendship when he later joined Dan Tosteson’s department at Duke. From Joe I learned some interesting information about Kacy. In Chicago Joe had known George Marmont, who had made sophisticated electronic equipment for experiments in collaboration with Kacy when he was still in Chicago. It was Marmont who had first had the idea of putting the axial wire down the axon, causing quite a stir when he referred to it as a “rape” of the axon. He also had the idea for the guard chambers. In particular, Marmont had made a current clamp for their MBL studies of the squid axon. When Kacy saw the current clamp equipment in use, he realized that voltage control offered a better method than Marmont’s current clamp to understand the basis of excitation. But Marmont did not appreciate the extraordinary possibilities of the voltage clamp.

Joe told me that Marmont and Cole could not get along personally. Perhaps personal animosity kept Marmont from realizing the power of the voltage clamp, but he was so stuck on using current clamp to study the action potential that at the MBL the two collaborators had to split up the day. Marmont worked by day with the current clamp, recording many action potential shapes, but he was unable to understand the underlying processes. Kacy worked at night with the equipment switched to voltage clamp mode, recording only a precious few currents, but he was unable to interpret their roles in excitation. Hodgkin, then, visiting the MBL, recognized that Kacy’s voltage clamp was the key to solving this fundamental problem. Kacy and Marmont published separately and later Marmont quit academia.

Other colleagues with whom I interacted at the NMRI were Terrill Hill, a very smart, mathematically oriented physical chemist; Dave Goldman, who as a graduate student under Kacy developed the membrane equations that bear his name; and Fred Julian, who worked in Goldman’s lab and developed the sucrose gap technique with me.

Woods Hole and Hurricane Carol

Kacy kept his promise to go to the MBL, but each summer for the first few years was too short to make progress beyond finding the limitations of our squid chamber. It was in one of these first summers, in 1952, that Hurricane Carol sneaked up on us.

We were in the lab and I noticed that the water squirt bottle started to squirt on its own. I relieved the pressure and it started squirting again. A few minutes later I looked out the window and saw the ferry rushing into port and slamming against the dock—and there was the bottle squirting again! Clearly the barometric pressure was plummeting. It was at the time quite puzzling; the weather information in the early 1950s was poor. We had heard radio reports of a hurricane off Cape Hatteras, but it was said to be moving slowly. Everyone had come to the lab thinking that if it were to target the Cape it would take several days to travel that distance. The rising wind that morning had been out of the northeast, so people dismissed the blustery weather as a standard nor’easter.

But it was indeed Hurricane Carol, bringing disaster that lives vividly in the memories of everyone who was in Woods Hole at the time. She hit at full force at high tide. We were in the lab on the third floor of Lillie building where everyone had been doing experiments, oblivious to the danger.

Water started pouring over the seawall and into the basement of Lillie. This hurricane caused extensive damage and ended the scientific effort that summer.

Next summer, 1953, one of the first things Kacy and I did together was to use the new microelectrode technique to measure the voltage in the giant axon in situ in a squid that had been opened up and laid out flat. We wanted to know if the action potential in vivo was the same as that in the isolated axon. I got help at the MBL from Steve Kuffler and Carlos Eyzaguirre in penetrating the axon with microelectrodes that had to traverse the surrounding tough sheath. I had noticed in previous summers that dissected axons tended to run down with time; as they deteriorated, they depolarized and the undershoots of their action potentials became larger. We found that there was no undershoot in vivo, evidence that the undershoot in the isolated axon indeed represented a degradation to a lower resting potential from dissection time or damage.

The main consequence of these first few MBL summers was to remind Kacy that being at the MBL was what he loved—sitting at the setup in a Lillie lab, humming, dissecting, and doing experiments. Kacy’s pleasure in dissecting and experimenting led within a few years to his quitting his administrative post at the NMRI and moving across Wisconsin Avenue to the new Building 10 of the National Institutes of Health. He took the position of Lab Chief with a decrease in responsibilities and salary; here he could return to experimenting. I went with him, pleased that I was the force that got him back into active science. At the NIH, Kacy was Chief of the Laboratory of Biophysics under Seymour Kety, the Director of the National Institute of Neurological Diseases and Blindness (NINDB). Kety, eyeing Cole’s enthusiasm for his reduced responsibilities and his pleasure at working in a smaller setting, became intrigued with the notion and stepped down from the Director’s position to head a laboratory himself!

1954–1961: The National Institutes of Health

Moving from the NMRl to the NIH

We didn’t have much equipment to move from the NMRI to the NIH: just the old AC Wheatstone bridge, a microscope, an oscilloscope—practically nothing. Fancy electrophysiological setups with racks and isolation tables were not standard equipment in 1954. I have a vivid recollection of standing at the entrance of Building 10, an enormous new edifice, with a marbled foyer to inspire awe, and realizing that now everything was available to us: space and excellent facilities. So now I had to perform—no excuses! We had not only more space but very good mechanical and electronic shops and we could start to make a real electrophysiological laboratory. In this huge building at the time were Mike Fuortes, Kay Frank, and Charlie Edwards.

Eric Kandel was upstairs doing a postdoc with Wade Marshall (whose wife Louise helped found the Society for Neuroscience and actively recorded the history of the field).

This big building had come about because of the generosity of Congress. According to the NIH Web site, the NIH budget had expanded from $4 million to $100 million from 1947 to 1957, and the building was part of this expansion. In 1955 Jim Shannon became the Director of the NIH (1955– 1968) and under his leadership it expanded even more, resulting in the “Golden Years” of the NIH. The story is frequently told that when Shannon would present the NIH budget to Congress, Lister Hill from Alabama and another forward-looking senator would say, “Jim—are you sure that’s enough?” Even if Shannon said his budget was enough, Congress would give him 25%–50% more, repeating this interesting phenomenon over several years. Why was this time so good to research? It was an expansive time— computers were just appearing and Sputnik had spurred extraordinary interest in science when it was launched in 1958.

The NIH shops were run by an efficient guy named Mike Davis, who assigned a young ex-Marine named Ed Harris to work with me. Ed devoted much of his time to making electrical and mechanical devices that I designed for Kacy’s and my research at the MBL. Because Ed’s work was excellent, when I moved to Duke in 1961 I proposed for him to be the department’s instrumentation person. In time at Duke I was able to employ him full time to work on voltage clamp projects until he died from cancer at a tragically young age.

Voltage Clamping Squid Axons at the MBL

With the move to the NIH we finally settled into a routine where we worked at the MBL in the summer months, typically from mid-May to mid-September, and at the NIH in the “off season” winter months. Kacy could go to the MBL for a longer time now that he no longer had administrative responsibilities. Experiments were done primarily in the summer. Back at the NIH in the winter, I read the scientific literature, analyzed the results of the previous summer’s experiments, planned the experiments for the upcoming summer, wrote manuscripts, updated equipment, and in general prepared for the intense experimental work at the MBL.

The first productive voltage clamping was at the MBL in 1955 or 1956. We employed Cole’s previous chamber where the axon was arranged lengthwise in a 1-mm slot that traversed three major saline pools (two guard pools and the central measuring pool), the axon draped over the ends. At one end Kacy would make a tiny snip, insert the axial wire, and thread it down the interior.

Enormous effort went into making the electrode. Even though extremely fine, it had to be stiff and straight, and carefully electroplated for low surface resistivity. There were several different plating methods; we had to search for the best method to make the resistivity as low as possible. After a long, careful dissection . . . well, let’s discuss “long.” Kacy’s idea of how to dissect an axon was to work slowly and carefully because when working with Hodgkin, he and Alan had once found that a very long dissection gave the finest result. On the other hand, Jose del Castillo, with whom I worked a few years later, dissected quickly with far greater manual dexterity and his axons typically gave excellent results.

Insertion of the internal wire was hazardous because when Kacy nipped the axon to put in the wire, any bathing seawater (containing calcium) contacting the internal axoplasm would quickly degrade the axon, turning the gelatinous axoplasm into soup. Also, simply making sure that the wire was properly aligned with the chamber took time and there was much cursing as the wire was inserted. But I think Kacy simply relished putting in this wire, humming and cursing, enjoying every minute of the hour or two he took to insert it. The yield of good axons, however, was quite low—perhaps one per day or two.

Kacy was a fine mathematician but not particularly knowledgeable in electronics, which was my strength. Now that I was at the NIH, I could design electronics and have instruments built to my specifications by Ed Harris. Because of my training with Art Vance at the RCA, I knew how to produce a high precision voltage clamp circuit with operational amplifiers. By the time I moved to Duke in 1961, op-amps became commercially available so I could use them rather than having Ed build my own op-amps.

I actually was able to improve on the quality of Hodgkin and Huxley’s voltage measurements. First, I impaled the axon with a microelectrode, measuring the difference in membrane voltage between this microelectrode just under the membrane and a larger reference electrode outside. Hodgkin and Huxley’s voltage sensor, the axial wire, was both physically and electrically remote from the inside of the axon’s membrane. Membrane current flow through the intervening axoplasm produced a voltage drop across its resistance and thus introduced an error in their membrane voltage measurements. Second, I used an amplifier developed at MIT and shown to me by Jerry Lettvin, a brilliant and iconoclastic physician, engineer, neuroscientist, and poet, who visited Kacy from time to time. During these visits Jerry and I became very fond of one another. The MIT amplifier incorporated ultra-high input resistance as well as a circuit that compensated for the capacitance across the glass wall of the microelectrode. So with this more precise measurement of voltage I could now control the voltage across the membrane rather precisely.

I was also able to improve the measurement of the membrane current. Hodgkin and Huxley had measured the current by the voltage drop across the resistance of the bathing solution, but I realized I could measure current directly with a current-to-voltage converter. Art Vance never knew that, through his influence on me, he made a major contribution to the design of this wonderful new technique in neurobiology, membrane current measurement using the voltage clamp.

Back at the NIH in the winter of 1956, I was joined by Jose del Castillo, a Spaniard, who was one of my favorite collaborators of all time. He was swarthy, athletic, handsome, and delightful to work with. Jose was also extremely dexterous, with a sharp intellect to match his facile hands. We were somehow perfectly compatible. Jose had trained with Katz in England and then had worked for a few months with Jerry Lettvin at MIT. Jose and Jerry had tried to study the frog node following a method similar to that of Frankenhauser and Dodge. I thought that Jose and Jerry’s system had problems since their records looked curious, so I proposed that Jose and I join together and use electronic feedback in order to measure the nodal currents more accurately.

We set up a “Vaseline gap” clamp to record currents from a single node of a single axon dissected from frog sciatic nerve using Vaseline as a seal on either side of the node. A major problem was that the resistance of the seal could never be high enough for us to measure the voltage across it accurately because there was always fluid between the Vaseline and the myelin sheath. So I designed an electronic feedback circuit to increase the effective resistance enormously by electronically forcing the voltage drop across one of the gaps to be minimized to a few microvolts. Jose and I published this circuit under the title “An Electronic Electrode” (Moore and del Castillo, 1959).

Then, at the MBL the next summer, Jose and I did a simple experiment that led to more ramifications than we expected. We inserted an axial wire into a squid axon and measured the velocity of propagation of the action potential from one end of the wire to the other. As expected, the time for the action potential to travel from one end of the wire to the other was essentially zero because the wire had short-circuited the axon’s internal resistance and the region in which the wire was located was now isopotential. But, unexpectedly, the waveform of the spike became more and more unusual as it approached the region with the wire, reflecting its difficulty of propagating into this region. I later followed up these experiments with Monte Westerfield at Duke to establish the importance of geometry in the generation and propagation of action potentials.

At the MBL, Jose and I would experiment in the morning, plan our next experiments at Nobska Beach after a swim, draw the plans in the sand, and then return to the lab mid-afternoon to carry out the experiments we had just discussed. This relaxed routine was marvelously productive and in part it worked because Jose was so very quick with his dissections. We also started a tradition: when we had a good axon, we would throw it to the ceiling like a piece of cooked pasta, and there it would stick, the threads we had used to tie off each end hanging down like tiny stalactites. For years these axon threads hung from the ceilings of the labs we rented each summer!

Committing to the MBL

In the 1950s, the MBL decided to offer parcels of its substantial land holdings in Woods Hole to scientists in the hopes of seeding a community that would return to the Laboratory summer after summer. In 1955 I jumped at the chance to buy a lot on F.R.Lillie Road (for $800!) when it became available. Dozens of other investigators bought parcels on Lillie and Wilson Roads—a mass migration of scientists to a summer settlement. I hired a carpenter to put up a shell of a house, as some of us did, and then my task was to complete the interior. Nobody had much money, so many of us had to build the interiors of our own houses. By this time Lee and I had adopted three children (Reid, Marjorie, and Steve) and you can’t imagine what it was like to try to do experiments, build a house interior, and deal with a family. But now all of us scientists were in the same wonderful situation, with our own house in Woods Hole and the expectation of many future summers in this inspiring environment. We had an immense gratitude for the chance to work at the MBL and tried to give back to the Lab over the ensuing years by working on committees and as Trustees, and eventually donating money.

Wintering Back at the NIH

Back at the NIH, Dick Fitzhugh and I were joined in the Cole lab by a mathematician named Knox Chandler. Knox was engaging, generous, and fun— just a delight to be around. He was lucky to be able to go to Cambridge off and on to work with Hodgkin. In particular he, Hodgkin, and Richard Adrian published a very important paper (Adrian et al., 1970) in which they used three electrodes to create a space in a muscle fiber where there was uniform voltage and then measured the current in that part. It was an ingenious application of the voltage clamp to a preparation that had appeared impossible to clamp because of its contractility.

The paper of Knox’s that had most impact on me was one with Hodgkin to solve the problem of the erroneous amplitude of the action potential, where it surpassed the equilibrium potential for sodium ion (ENa). This error by Kacy (Curtis and Cole, 1942) set back progress on understanding the action potential for several years; later, in a series of papers, Ichichi Tasaki again reported huge amplitudes that called into question the voltage clamp work of Hodgkin and Huxley.

The conventional way of measuring the action potential at the time was with the axon’s glass cannula, drawn out into a long, small-diameter capillary. The cannula was about the diameter of the axon, but at the point of insertion it narrowed into the capillary, which was threaded along the axon’s axis. The capillary was filled with conducting solution; a wire back in the cannula measured the internal voltage picked up by the capillary. Hodgkin had realized that there would be a time delay in measuring the action potential via this long capillary because its high internal resistance would slow the voltage signal. So he, with Huxley (1945), and then with Katz (1949), inserted a wire to short-circuit this resistance. Hodgkin must also have been aware that there would be a capacitive current flowing through the glass wall of the cannula into the electrometer when the action potential reached the end of the axon tied to the cannula. Thus, as the action potential traveled up the capillary into the cannula, the capillary’s high resistance and cannula’s capacitive current combined to produce an erroneously large action potential.

Spurred by Tasaki’s continued publication of oversized action potentials, Chandler and Hodgkin (1965) published unequivocal evidence of capacitive current artifacts; they showed records similar to Tasaki’s that overshot ENa using his method, then action potential records that never exceeded ENa when the wire was present in the capillary. In our correspondence, Huxley has asked whether I have insight into how Kacy could have made his error of the strangely high action potential. Although Kacy proposed that his was an error from overcompensation for capacity, it seems to me that his error was the same as Tasaki’s: the lack of the short-circuiting wire in the capillary.

Colleagues at the NIH

There were many splendid colleagues at the NIH. I particularly enjoyed interactions with Kay Frank and Mike Fuortes—I liked to look at their data, talk circuits, and exchange manuscripts with them. They had started to voltage clamp spinal motoneurons of the cat, working together off and on, so their experiments were closely related to mine. Their experiments derived from those pioneered by Jack Eccles (later Sir Jack). Jack’s recordings made him think that the impulse initiated in the initial segment, the portion of axon between the hillock and the myelin, because of a lower threshold there (Coombs et al., 1957). Kay and Mike came to the same conclusion and actually drew a published diagram assigning a lower threshold to that region. In their simulations, Fred Dodge and James Cooley altered the parameters of the HH equations so that the threshold for the action potential was lowered in the motoneuron’s initial segment in their simulations.

Later, I became quite intrigued with this problem and took it up with Monte Westerfield; he and I showed in both experiments and simulations that morphology alone could cause the impulse to be initiated at the region where the large-diameter soma became a small-diameter axon (analogous to the initial segment). But when Monte and I tried to publish the hypothesis that geometry alone could explain impulse initiation at this juncture, my good friend Fred was the referee and rejected our paper! We argued our case; he argued in response that if readers were presented with two groups (him and us) doing simulations of the same process, yet disagreeing, then they would be prejudiced against simulations! Monte was quite careful with the wording, I asked to have a new reviewer, and the paper was accepted.

At about this time Ladislav Tauc visited Mike and Kay from France. He was putting electrodes into the huge cell bodies of Aplysia neurons and finding that the action potentials recorded there were quite small. His explanation for these diminutive action potentials was that there must not be many channels in the soma, making it difficult, if not impossible, for the spike to invade from the axon. But the records looked just like my records, taken with Jose, in which we had put a wire down the axon to mimic a soma. We found that as the impulse struggled to invade this “soma” section of axon, its amplitude was smaller and had a curious shape. So I felt that the change in geometry might explain Tauc’s observations rather than a decreased number of channels. Tauc’s observations added to those of Eccles, and of Frank and Fuortes on the motoneuron, in ratcheting up my interest in how a neuron’s impulse might propagate or fail to propagate into its component parts. What happened to its waveform at branch points? At transitions between myelinated and nonmyelinated sections? Monte Westerfield and I would revisit this question later.

Jack Coombs, a splendid electronics engineer, visited us from Jack Eccles lab in Australia for a few months. Coombs’ skills made us realize the utility of having an electronics engineer, so when he went back to Australia we hired John Gebhart to work on these very high impedance preamplifiers (also called potentiometric circuits) to measure potential. The sharp microelectrodes we were using to read the voltage just under the membrane required a special circuit because the preamplifier tubes had a capacitance to ground. We were using a capacitance compensation circuit previously shown to me by Jerry Lettvin; it was described in the Report of War Research from his Research Lab of Electronics at MIT (in the Plywood Palace, Building 20, sadly now demolished). John Gebhart and I worked out an analog simulator of this negative capacitance circuit—the first simulation of a circuit and perhaps the first time I worked back and forth between a simulated circuit and the real thing. John and I published a paper on the simulation of the circuit (and of course we made the circuit itself) to demonstrate the principles for capacity compensation. We also simulated (and made) a “chopper circuit” that drastically reduced the DC drift; the chopper converted DC drift into a square wave whose amplitude could be minimized by negative feedback.

Jerry Lettvin and the Frog’s Eye Paper

The Institute of Radio Engineers (IRE), that later became the IEEE, wanted to have an issue of its journal devoted to biomedical engineering. At the suggestion of Britton Chance, I was asked to be a guest editor. I invited Jerry to write an article on his high impedance preamplifier for measuring voltages with microelectrodes. In the spring of 1959, as I left the Federation Meetings to board a plane, I met Jerry getting off the plane to come to the same meeting. He yelled “John—I’ve got a very special and important paper and I want to publish it as soon as possible. Can you please include it in your special issue?” I agreed to consider it as soon as he completed his assigned article. He accepted the challenge and brought the manuscript to Woods Hole that summer to show me. I read it and realized it was indeed ground breaking, but the title was quite boring, unworthy of such a remarkable paper, and would not attract readers. I thought that perhaps the title had been written by one of his coauthors, Walter Pitts or Warren McCulloch.

John: I ACCEPT the paper but REJECT the TITLE, which is certainly not yours.

Jerry: That’s true.

John: Then give me a better title in your own words.

Within milliseconds, Jerry came up with his now famous title: “What the Frog’s Eye tells the Frog’s Brain.” I wrote this title on the manuscript and, as guest editor, accepted it: no further review, no delay, only one revision—the title. This is a more complete telling of the story of how this memorable title came about than appears in Jerry’s Autobiography (Volume 2 of this series, p. 235). There he wrote a paragraph entitled “The Frog’s Eye” in which he refers to the title with the parenthetical statement (for which I am much indebted to John Moore).

Although this classic paper was published in 1959 in an obscure journal for neuroscientists, it is now widely known and referenced.

I Leave Kacy’s Lab

Kacy was running out of scientific ideas and being more and more difficult to work with. I was becoming increasingly restless in the lab and indeed was spending much of my time now back at the NMRI, working with Fred Julian in Dave Goldman’s lab to develop the sucrose gap. Kacy didn’t bother to interview or even inquire about people—he just used his first impressions. He was fixated on mathematicians, offering a job to Robert Taylor (who had been a postdoc with Huxley) sight unseen. On the other hand, he did not take Abe Shanes, a pharmacologist and enthusiastic guy working at the NIH who would have contributed a badly needed, broader perspective to the lab.

The situation between Kacy and me deteriorated. The final straw was when Kacy made Robert Taylor the author on work not done by him but by del Castillo and me. Robert had suggested to Jose and myself, as we were headed to the MBL, that it might be interesting to try procaine on the squid axon. We did this experiment, made figures (I still have the originals), wrote up the results, gave the manuscript to Kacy to read, and the next thing we knew was that Kacy had made Robert the sole author on the paper! I was furious. Jose and I had done the work—what right did Taylor have to author this paper when he hadn’t done the work? When he hadn’t written the paper? I could no longer work under these circumstances and had to leave.

1961–1968: TTX and the Sucrose Gap at Duke

As I started looking for other jobs in the Bethesda area so as not to move the family, an opportunity became available to do postwar research at the Johns Hopkins Applied Physics Lab in Silver Spring, MD. The job did not really interest me, but I had said a tentative yes anyway—I was absolutely intent upon leaving Kacy. But a few days later I received a call from Dan Tosteson, who had been in another lab at the NIH. He and I attended biophysics seminars together and, by the questions he asked, I knew he was a most remarkable person. In his call he said he was accepting the chairmanship of the Departments of Physiology and Pharmacology at Duke and wanted Paul Horowicz and me to join him there and in fact his taking the chair was contingent on the two of us joining him. The Duke opportunity—doing the biophysics I enjoyed, being in a university setting, being close to my parents, and with Dan as Chair—was irresistible.

From the beginning of his Chairmanship of the two departments at Duke, Dan’s focus on research, his own and that of the faculty, was either matched or exceeded by his intention to improve medical education. Dan played a key role in changing the medical curriculum, both at Duke and also as dean of Harvard Medical School where he completely reoriented its curriculum to a model now being followed by other medical schools as well.

Beginning at Duke

The dean of Duke’s medical school, Barnes Woodhall, was the host of a “recruiting dinner” for me, held at the Hope Valley Country Club where he was a member—the most elegant setting in town at the time. At this dinner were: Dan, the future dean of Harvard Medical School; Phil Handler, Chair of Biochemistry and future president of the National Academy of Sciences; and Jim Wyngaarden, future director of the National Institutes of Health!

Phil later (1963) asked me whether I would take his son Mark to Woods Hole to work with me at the MBL for the summer. Of course I took Mark— with unexpected and far-reaching consequences having to do with his parents, Phil and Lucy. They came to visit Mark in Woods Hole, were smitten with the place, and began to take their vacations there, renting houses. Shortly thereafter Phil was named president of the National Academy. When the Academy was looking for a place to hold conferences and an estate became available on Quissett Harbor (next to Woods Hole), a gorgeous setting on a promontory overlooking the harbor and Buzzards Bay, Phil grabbed it for the Academy.

And that was not the end of my influence through providing opportunities for scientists’ sons. DeWitt (Hans) Stetten, Jr., who would eventually become Deputy Director for Science at the NIH, heard from Phil that I had taken Mark and thought the opportunity would be great for his son George. So of course I took George, who went on to become a professor of Bioengineering and Robotics in Pittsburgh. Hans had been bringing his family to Woods Hole every summer since the late 1950s. The magic of Woods Hole is irresistible, it seems.

Working in Duke’s Bell Building

I started at Duke in the fall of 1961 and Ed Harris came with me. Ed, a former Marine was proud of being tough but was extremely gentle and kind, not the Marine stereotype. Like other Marines, he had tattoos on his arms; later, when he drove a 24-foot U-Haul to Woods Hole filled with racks of expensive electronics and huge wooden boxes packed with scientific equipment, he deeply enjoyed the responsibility, driving the 15 or so hours straight through in his Texas boots, and arriving triumphant at the MBL loading dock at precisely the predicted moment. One year he even thwarted a possible hijacking! In time, Ed and I constructed tool cabinets and equipment boxes that rolled on heavy duty castors for rapid loading and unloading of the truck in my lab’s annual migration to the MBL. We would even transport to the MBL some shop equipment such as a drill press and a Minimax (a combination of a lathe and a milling machine) because we frequently modified equipment as we did experiments. Ed took special pride in building my voltage clamps. I would try out his clamp at Woods Hole, redesign it after a summer’s work, and then he would modify the design in the winter.

These first years at Duke were in the Bell building, an old dilapidated structure I detested because the cancer researcher who obtained the money for it was a racist who insisted on “his” building having black and white restrooms. In the spring of 1961, in preparation for my fall arrival at Duke, I had discussed the renovation of my space with the building planners and expected that it would be completed when Ed and I arrived in the fall. But instead we found that absolutely nothing had been done. Inquiring why, I found that “they were just waiting to be sure that it was exactly what I wanted.” Furious, Ed and I did it ourselves. In those days we had a great deal of freedom with the building code. Certainly that sort of unprofessional construction in a lab would not be allowed now.

The Sucrose Gap Chamber

Following our own lab renovations at Duke, Ed reproduced the precision electronic circuits and equipment that had been carefully worked out at NIH. He also built two sucrose gap chambers, one for lobster axons and one for squid giant axons, both chambers improving on that first one designed and used at NMRI for lobster axons. The squid axon chamber allowed exploitation of the squid axon’s increase in diameter and length over that of the lobster in three major ways:

While the exposed length of the “artificial node” (between the streams of flowing sucrose) was about the same as for lobster axon, it was a much smaller fraction of the overall length of the squid axon. Thus, the voltage uniformity in the squid axon “node” was far superior to that for the lobster.

The surface-to-volume ratio for a length of squid axon was far smaller than that for the lobster. This allowed us the luxury of much longer experiments before axoplasmic ions leached into the flowing sucrose, degrading the quality of the voltage control of the “nodal” membrane.

We were able to add a sliding holder for the axon, allowing the axon to be translated longitudinally through the flowing streams.

These factors together provided great flexibility and dramatically increased our experimental success rate as well as the ratio of experimental to dissection time.

For example, one could avoid spots along the axon that had been damaged during dissection and choose very active areas for the node. Furthermore, a fresh area of axon node could be chosen for the next experiment. This made possible repetitions of a single protocol on a single axon—analogous to an assembly line. In contrast, the axial wire voltage clamp had required that the dissection of the whole length of the axon be damage-free, greatly reducing the probability of a successful experimental day.

Discovering the Action of TTX

I had heard Toshio Narahashi talk a few times at meetings and was intrigued that in Japan he had used the infamous puffer fish poison tetrodotoxin (TTX) on muscles and found that they were no longer excitable. TTX is the poison well known in Japan to be concentrated in the ovaries of this tasty fish. Chefs must be trained in the careful removal of the ovaries and preparation of the fish; should they make a mistake and cause a death, they in turn are expected to commit hare kare. Minute quantities of TTX can kill a person: the first sensation is a numbing of the lips, followed in a short time, depending on how much one had consumed, by paralysis of the nerves and muscles of breathing. So TTX was thought to act on nerves in some fashion.

Toshio thought that TTX might act by blocking the sodium conductance in nerve and muscle. Since I was studying sodium currents in axons, he and I had a mutual interest in applying TTX to axons in voltage clamp to test this hypothesis. He joined me at Duke and we, along with a medical student, Bill Scott, worked on axons from lobsters purchased at a local fish market. In spite of the disadvantage of ion depletion from the lobster axons in the sucrose flow, necessitating brief experiments, we showed a definitive block of the sodium current and nearly full recovery on wash out. Fortunately, TTX’s action is clean, precise, and unequivocal, so we did not need to do a large number of controls for a definitive answer and my first TTX paper (Narahashi et al., 1964).

Toshio then came with me to the MBL the next summer and we continued the TTX work but on the squid axon, generating the first in what would be a series of five papers. In the squid axon, TTX reproduced the data we found on the lobster axon; again the results were clean and unequivocal. Ironically, the downside of this almost perfect poison was that there was no controversy in the literature about its action and very quickly it was subsumed into the neurophysiologist’s tool kit much like an amplifier or oscilloscope. Soon it was not necessary to reference our papers and Toshio and I were forgotten, it seemed! Well, perhaps not entirely: Some 20 years later there was a meeting devoted to TTX and saxitoxin (STX) where Toshio and I were guests of honor. We were appreciative, having felt somewhat slighted at the beginning of the “TTX era.”

Actually, there was one small, incipient controversy, but one with a delightful outcome. At a meeting, Mordy Blaustein (who had replaced Fred Julian in David Goldman’s lab at the NMRI) reported that TTX blocked only at voltages below ENa but not above it (in contrast to our published work). Because Mordy was working with lobster axons, using the original chamber that Fred Julian and I had designed for these nerves, he may not have understood that ions could be leached from this small-diameter axon and confound his observations. It was very important to resolve this difference. So I invited Mordy to come to Woods Hole and do experiments with Toshio and myself on the squid axon. I made it clear that I wanted us to be able to agree on the data but that he would be free to publish separately if he did not agree with our interpretation. Working together, we three confirmed that Toshio and I had been correct: TTX blocked the currents whether the Na current was flowing out or in through the channels. I strongly recommend this sort of approach as a good way to avoid unnecessary controversy for we quickly solved the problem, had fun, were coauthors on two papers, and have stayed best of friends ever since.

Toshio had to leave me after our first year together because his visa had run out. Two years later he returned as an assistant professor and eventually occupied space adjoining mine when we moved to the Nanaline Duke building in 1968. At this point he began to run his own lab and we did fewer projects together. Later Toshio became chair of the Pharmacology Department when it finally split off from Physiology. I have continued to be amazed by, and envious of, Toshio’s efficiency in everything he does. Toshio frequently would have collaborators come for only a single day with assurance of success in an experiment. I could never be so confident.

During Toshio’s absence, another Japanese scientist, Mitsuru Takata, joined me and a Chinese neuroscientist, C. Y. (Eric) Kao, visited from Stanford. Eric brought yet another toxin, tarichatoxin, extracted from the eggs of a California salamander by two Stanford biochemists, Harry Mosher and Frederick Fuhrman. Kao and Fuhrman had shown that it blocked the action potential in frog nerve and wanted to know whether its action was similar to that of TTX. Mitsuru Takata and I tried the toxin on voltage clamped lobster axons and found that it blocked sodium currents in precisely the same way as TTX. But was tarichatoxin TTX itself, or was it another compound that affected the sodium current in the same way as TTX? I took a sample of TTX to Stanford where Mosher found that its infrared spectra matched that of tarichatoxin. But did this mean that the two toxins had exactly the same structure––that the eggs of an American salamander and the ovaries of a Japanese puffer fish were making exactly the same poisonous compound? In due course it was decided that the two toxins were indeed exactly the same, and it was gratifying that our voltage clamp results for the two toxins were identical.

At a small meeting in Miami, Toshio Narahashi and I talked about the effect of TTX on the squid axon. Bernard Katz (later Sir Bernard), listening in full attention mode, immediately wanted to know where to get this magic bullet. As soon as he received some TTX he exploited its blockage of sodium channels to study presynaptic calcium currents in isolation (Katz and Miledi, 1967, 1969). Also at this meeting of about 25 people was Trevor Shaw, who had been planning to come to Duke to work with Schmidt-Neilson but decided, as we rode together to the airport, to work with Toshio and myself to use TTX to count the number of sodium channels in an axon. The experiment used the walking legs of lobsters because they were innervated by bundles of very small nerves, giving us a lot of surface area. We estimated this area from cross sections of the nerve bundle seen in electron micrographs, made by Brenda Eisenberg, although this estimate was tempered as usual due to fixation. Although we guessed that there were about a dozen per square micron, we put a question mark in the title (Moore et al., 1967). At my retirement party, Jim Hudspeth teased me publicly by suggesting that we should have been more confident, or at least more adventuresome, in the title—perhaps “There are damn few sodium channels . . . .”

During this exciting TTX time I gave a major talk at a Federation Meeting. In the published paper from this talk I cite a reference from Playboy Magazine! Why? Well, the author, Ian Fleming, published two of the James Bond 007 adventures there. At the end of From Russia with Love, the female spy jabs her high-heeled spike into the leg of 007, the hero, and 007 flops to the floor. It turns out that she had TTX in the spike of the heel. But at the beginning of the sequel, Dr. No, we are told that 007’s colleagues, recognizing that he must have been poisoned by TTX, gave him artificial respiration and saved his life. To my dismay, Ian Fleming’s knowledge of TTX had not come from reading my papers. Instead he had spent time in Japan, where he had heard the TTX lore and had presumably been warned about eating fugu.

Teaching a New Field: Excitable Membranes

In my first years at Duke I began teaching graduate students with a fine new colleague about 10 years my junior, Paul Horowicz. Paul, a modest and dignified scientist, was scholarly and thoughtful, well read, and rather formal, especially in his dress; he was an extremely nice person with a great sense of humor and was a joy to have as a close colleague. Paul was recruited by Dan Tosteson, who had known him at Washington University in St Louis where Paul had been a brilliant student. Paul had then been a postdoc with Hodgkin, distinguishing himself by doing the single muscle fiber dissections of the tour-de-force Hodgkin and Horowicz papers. (Remember that this very difficult dissection had been done by only one other person, Sybil Street, Bob Ramsey’s graduate student.) Paul and I often met with Dan at his house, especially in the early days of expanding the department, where Dan would seek our advice before he took action. (Dan was a great chairman, especially in seeking advice of the faculty on tricky issues; when he decided to make a political decision unpopular with the faculty, he would always take the heat.)

Paul and I designed and taught a new course called “Excitable Membranes” concentrating on the axon, my specialty, and muscle, which was his. Inventing this particular course was especially exciting because both of us were immersed in the field and also because Paul was probably the best muscle physiologist in the country at that time. We taught the course as a seminar and at least one student blew it away, as I now describe.

It happened in the section of the course where we discussed the Hodgkin-Huxley equations. One student in the class, Frank Starmer, although only an undergraduate, was in the bioengineering department and had access to the Duke IBM Computer. At that time universities rarely could afford more than one single mainframe computer. This sacred machine was overseen by a faculty committee from the math and physics departments, a Holy of Holies committee. Faculty who wanted computation done were required to write a program of instructions on a typewriter and then hand the program to clerics who would punch cards to put into the computer. So the scientists, “the commoners,” would come to the outer vestibule of the temple and bring their offering of punch cards to a junior priest, who in turn would take the punch cards to the high priest, who in turn would run the machine; the answer would then come back from the Holies in the opposite direction. A corollary of this arrangement was that the computer committee had a lot of power and did not want anyone else buying a computer at Duke. So all purchase orders for computers were routed through the committee for approval. This committee had a choke collar on anyone trying to do computation on campus.

One Monday morning Frank showed up with a pile of computer printout paper. Along the length of the paper, the abscissa, the time axis was displayed and across the paper, the ordinate, was voltage—like paper in a chart recorder. He had actually programmed the digital computer to calculate not only one but two action potentials in succession! I was awed! After his Ph.D. from UNC, Frank returned to Duke and joined Eugene Stead’s Department of Medicine as an Associate in Biomathematics; in 1971 he was a founding member of Duke’s Computer Science Department. After retiring from Duke, he continued working elsewhere in information technology and learning tools and is now helping to shape the curriculum at the new Duke-National University of Singapore.

Before Frank left Duke he brought to my lab a smart and amiable fellow named Gus Grant, an M.D. cardiologist working on ion channels. Two decades later I felt quite comfortable calling Gus right before leaving for Woods Hole and asking whether he could see me on the spot for symptoms that made me suspect I needed a pacemaker. He not only saw me—he put me straight into the hospital. I now have a fine pacemaker: its existence in my body is the result of a diagnosis by Gus, who was introduced to me by the best student in my first excitable membranes course, and of a design originally by Wilson Greatbatch, with whom I had served on the Biomedical Engineering Group of the IEEE!

My First Computer

In the 1960s there were two types of computer, analog and digital. The Duke IBM Computer was digital and had the advantage of accuracy, but the processes of loading, running, and plotting were slow. Analog computers were much faster but less accurate and uncommon in universities. But because I had been influenced by Art Vance toward analog computers, and having used one to solve the HH equations at the NIH with Dick Fitzhugh, I requested an analog computer built by Electronic Associates, a TR48, in my first grant application to the NIH.

I actually got a call from Ralph Stacy who was on the NIH Study Section considering my application. He was the primary reviewer of my application. Of course nowadays such an unethical call would be prohibited.

“John, this is Ralph. On that analog computer you are asking for—are you absolutely sure you have asked for enough components to solve the HH equations? This is your last chance to change before we approve.” Those days will never return!

The computer was approved and the money was committed for my work. Incredulously, the Duke computer committee blocked the purchase of this computer! How ridiculous it was that I had to waste my time writing a strong letter to higher authorities at Duke to be able to purchase the machine I needed for my research. Some things indeed have changed for the better.

The TR48 was about 6 feet long, 4 feet high, and had a front panel with plug boards wired to the amplifiers and components behind. I programmed it by simply leading wires from one banana plug jack to another. Individual units carried out particular operations. While the accuracy of the analog computer was limited to 1 part in a thousand, it was quite fast and speed was what was important to me. I wanted to solve the HH equations for the membrane (stationary) action potential on a fast analog computer so that I could see how varying parameters would affect it. Furthermore, this computer allowed me to simulate my experimental results and also was useful in revealing the fatal flaw in an approach called the “ramp clamp,” which some neuroscientists (including Kacy Cole) were enthusiastically embracing as a technique to speed up voltage clamp data acquisition (Fishman, 1970).

After a while, however, I needed the accuracy of the digital computer. I found that the Digital Equipment Corporation (DEC) made a machine called a PDP8, a Precision Data Processor—and guess what? That machine was not flagged in the Duke purchasing department because the word “computer” was not in the title! I asked the DEC representative if the name purposefully hid the identity of the machine from university purchasing departments and he said “you betcha.” Similarly, a machine made by Honeywell was called a Digital Data Processor to avoid the word computer. Obviously the computer purchasing problem extended beyond Duke.

An Explosion of Collaborations

I continued to attract a host of visiting colleagues, perhaps because we had developed a fast, reliable voltage clamp and recording system along with an axon chamber where multiple experiments could be performed on a single axon. Werner Ulbricht was a visiting German scientist who joined Toshio and me to internally perfuse squid axon using the roller for axoplasm extrusion that was loaned to us by Alan Hodgkin. Jerry Lettvin and his postdoc Bill Picard brought cesium to the MBL from MIT and we all, including Takata, Ted Bernstein, and John Pooler, my first graduate student, put cesium on the squid axon. Jerry had proposed that cesium would not go through the membrane and indeed our experiments showed no cesium current. Jerry came to Duke later with another idea: reasoning that because calcium ions in sea water partially blocked sodium and potassium currents, the trivalent lanthanum would be far more effective at doing this job.

Again Jerry’s intuition was validated, using lobster axons. Toward the end of our time in the Bell building a young guy from the NIH named Bert Shapiro brought us yet another toxin—condylactis toxin from the sea anemone—to test on the axons. (I found out later that Bert had been Annie’s T.A. at Swarthmore when she was a freshman in 1961.) People simply showed up with substances—it was a productive and lovely time. I also took on my first postdoc, Nels Anderson, who applied the voltage clamp to smooth muscle and, after his postdoc years, continued this work independently in the department.

It was a swinging biophysical gang at Duke. In particular I enjoyed knowing Richard Adrian who worked with Paul Horowicz for a year or two. He was a superb scientist, a warm and gentle person, and went on to become a Lord like his Nobel Laureate father, Edgar. I thought if all the Lords of England were like Richard, the country would be extremely well governed. Dan and Paul were rather well known in Europe, so there was a huge European influx of visiting scientists; between us all we had a steady stream of people coming through. Dan would question the visitors relentlessly at their seminars and then have dinner at his home for the visitors afterward—with perhaps a dozen of us—and continue to question them intensely. He had bought an old mansion in the main part of Durham, previously the home of a tobacco executive, so the house was near Duke and was large enough to accommodate many people. He created an unusually intellectual atmosphere that knew no time or location limits.

Visiting Takata in Japan

Here I digress to discuss some highlights of a trip to an International Physiology Meeting in Japan in 1965. Mitsuru Takata, who had just gone back to Japan and was living in Osaka, was also at the meeting and had invited me to be his guest after the meeting. Mitsuru and his wife had hired a taxi to take us to visit a famous palace in Kyoto. We knew that Japanese were not allowed into this palace—only foreign visitors of importance were allowed to enter. Consequently Mitsuru expected to return to the taxi. But when we arrived at the gate, the gatekeeper said, “Tour already left—take him to join group.” Mitsuru was flabbergasted and overjoyed to be able to see the palace and of course rushed in with me to catch up with the tour.

The second day the Takatas became comfortable with me and hesitatingly asked whether I would stay with them in their little home in Osaka. Osaka was not far from Kobe, where my parents had been born. I was delighted and overwhelmed with their hospitality. What a tiny place they occupied, sleeping on futons that were pulled out from hiding every night. That night we both bemoaned the war. Neither of us had been directly involved, me because of my club foot and he because of a deformed left hand. The next morning his wife played on a shakuhachi, finishing a lovely, quiet, gentle, friendly interlude in their home overnight. The contrast between the home and the very noisy Japanese bustle outside was a shock.

I met Toshio for the trip back to the United States. We had to refuel at Honolulu, arriving very early on a Sunday morning. Here was a Japanese and an American, sitting side by side, discussing the Sunday morning of December 7, 1941.

Moving to the Nanaline Duke Building

The Physiology Department was in dispersed locations for the first 7 years of Dan’s chairmanship, so it was a pleasure for the department finally to be all together when, in 1968, we moved to the Nanaline Duke building, the result of Dan’s and Phil Handler’s efforts. At this time an absolutely charming Australian named Peter Gage came to work with Paul but suggested also working with me on the squid giant synapse at the MBL. Perhaps he was lured by the idea of Woods Hole as much as by the experiments! Peter and I attempted to find the reversal potential of the postsynaptic response at the squid synapse, even though it was quite difficult to voltage clamp, as a clue to the identity of the neurotransmitter. We found that the reversal potential extrapolated to the sodium equilibrium potential—that is, the transmitter caused a change only in the sodium conductance rather than a change in both the sodium and potassium conductances known to be caused by acetylcholine at the frog neuromuscular junction. This made acetylcholine unlikely to be the transmitter. Returning with me from the MBL after the summer of 1968, Peter completed the year with Paul, then could not resist returning to the MBL in the 1970s for more experimental fun with me.

Within 2 years of moving to the Nanaline Duke building my dear colleague Paul Horowicz was called to be chair at Rochester, to my sorrow, and worse, he took with him Clay and Clara Armstrong. Several other members of the department left to become chairs elsewhere. Within the next 5 years the “Camelot years” of the department would be over as the department split into separate Physiology and Pharmacology Departments, Toshio became chair of Pharmacology, and then Dan left to become dean at Harvard Medical School.

1968–1975: Modeling Action Potential Propagation

In the early 1960s, our sucrose gap voltage clamp experiments on axons were manually controlled: we would set the parameters (amplitude, duration) of a voltage step, push a button to trigger it, observe the resulting current on the oscilloscope screen, and photograph the traces with a Grass Instrument camera (a movie camera allowing each frame to capture one set of traces).

The tedium of recording data and then developing the film, plus the delay in the analysis of the filmed traces, drove me to devise faster methods for storing and retrieving such data. Analog tape recorders were available but were completely impractical for capturing a current trace lasting only a few milliseconds followed by the interminable seconds between pulses. It dawned on me that a small digital storage buffer could hold a single trace, quickly stored, which could then be read out to an FM analog tape recorder during the interval between pulses. However, we needed an Analog-to-Digital (A/D) converter that would follow the extremely fast sodium current transients, a device much faster than any commercially available A/D converter at that time. Fortunately I was able to improve on contemporary logic design and employ the electronic skills of Ed Harris to build an augmented count-up count-down converter. With a four-bit shift register to keep track of recent up/down changes, it was able to take accurate data points at 4 microsecond intervals; with each tick of the clock, the shift register was queried in order to determine the size of the next up or down step (Moore and Harris, 1972).

We purchased a “small” storage buffer with a magnetic core memory of 4096 words of 10 bits each; small is in quotes because while the actual number of bits was small, the box holding it had to be rack-mounted and was at least a foot high! (In contrast, today’s flash cards can store gigabytes of 32-bit words.) The readout of the current record was at a very slow rate so that an FM analog tape recorder could save the traces for later plotting out with a pen on an X-Y plotter. This system—several relay racks filled with electronic boxes custom-made by Ed Harris—worked reliably for many years.

Lab Computers Become Commercially Available

Hoping to further speed up the storage and retrieval of traces and also record the time, temperature, and holding and pulse potentials of the experiment, I purchased a LINC8 computer. The LINC8 was built by DEC, merging its own PDP8 with the LINC (Laboratory INstrument Computer) developed at the Lincoln Laboratory at MIT. It had a built-in A/D input and D/A output; it used DEC’s logic boards of transistors, resistors, and capacitors to do digital logic. This computer, a double-bay relay rack on wheels, could be programmed to take data and store it on digital magnetic tapes available from DEC. However, because the LINC8’s A/D converter was slow and had poor resolution, we needed to continue to use our own, much faster A/D converter and buffer memory.

I had been incredibly fortunate at this time to attract as a graduate student Ronald Joyner, a whiz at math and programming. Ron quickly accepted the challenge to design programs to interface the LINC8 computer with our equipment, programming it to control the voltage, read the current, and store this information on digital tape for later analysis. He wrote programs using FOCAL, a proprietary language for DEC machines, adding his own new functions. The LINC8’s clock triggered the voltage clamp (whose parameters were programmed), it stored the voltage and current data in our external buffer memory, and then it read these values onto the DEC tape between pulses (Joyner and Moore, 1973). Now we could quickly record a whole family of currents in response to, say, 12 voltage steps, put on a toxin, see the effect on the family, wash it off, and wow—we were suddenly in a full production mode! This computer became our workhorse for voltage clamp experiments on the squid giant axons.

In addition to his Ph.D., Ron received his M.D. at Duke and then he stayed on with me as a postdoc. He is now a professor in the Department of Pediatrics at the Emory School of Medicine. Ron has continued to make unique contributions in both his cardiac studies and computer modeling, amply demonstrated by his novel “coupling clamp” technique where he couples a real cell to a real-time simulation of a model cell.

A Sabbatical at the Rand Corporation

I now became interested in the possibility of simulating a simple neuronal network, so in 1969 I took a sabbatical with a splendid mathematician, Don Perkel, at the Rand Corporation in Santa Monica, California, where such simulations were being attempted. Don had written software programs to simulate nerve cells on a time-sharing machine, built at Rand, that was called the Johnniac for Johnny Von Neumann, the legendary computer scientist. He had also written software for an IBM 360–50 to model a network of nerve cells. I wanted to use this program to learn how much detail was required to describe the simplest of networks (two interacting identical cells) in order to achieve a realistic output reproducing experimental observations. Several years previously, Leon Harmon of Bell Labs had attempted to simulate the performance of two such interacting neurons in a locust, but his very basic model failed to match biology. Ted Lewis at Berkeley added axonal and synaptic delay to Harmon’s, but the simulations were still not realistic. Although I had access to Perkel’s network program on an IBM 360–50 computer at Cal Tech, it had not been debugged, and I failed to answer my question. Nevertheless, I developed a much deeper appreciation of the challenges of network simulation through this attempt and through long discussions with both Don Perkel and Ron MacGregor at Rand.

We Finally Simulate Propagation

Returning to Duke, I set about evaluating integration methods with Fidel Ramon, a playful Mexican M.D. postdoc (now a member of the Faculty of Medicine of the National Autonomous University of Mexico), in order to find the optimal method for achieving speed and accuracy in simulating the action potential and, ultimately, propagation. We tested four different integration methods, modifying one to achieve the accuracy and speed that would make optimum use of the slow digital computers of that era. But Fred Dodge, the newly appointed Editor-in-Chief of the Biophysical Journal, rejected our paper (again!). We were perplexed by this rejection because his participation and help was acknowledged in the paper! It turned out that he thought that a simulation-only paper was inappropriate for a biophysics journal. So we published the paper in the Journal of Theoretical Biology (Moore and Ramon, 1974); later a chagrined Fred apologized, saying that he had to refer many requests for information about the accuracy of integration methods to our paper in a competing journal!

Meanwhile, Ron Joyner was working out a method to simulate propagation by solving the cable equation for the axon. He also developed a powerful computer simulation for our electronic voltage clamp. Using these two simulation tools, Ron, Fidel, and I then looked at the quality of the data that could be obtained with the sucrose gap. We wrote a series of papers in which we detailed the simulation methods, simulated a single axon and then a bundle of fibers in a sucrose gap, described how the equipment and axon interacted, and all along compared our simulations with experimental results. I was particularly fond of the papers from this work, which took an approach that had not been done before and thus broke new ground in the field. In 1975 this series of four papers was readily accepted by Fred Dodge, who had changed his mind about simulation papers, and they took up much of one issue in the Biophysical Journal (vol. 15, no. 1).

By the way, in the summer of 1974 I attended a party in Woods Hole and spent some time talking with a young neurophysiologist named Ann Stuart, an Assistant Professor in Steve Kuffler’s Neurobiology Department at Harvard Medical School, who was studying the synapses of the huge photoreceptors of giant barnacles. We had earlier been introduced to one another (in 1968) in John Nicholl’s lab where Ann was a graduate student; now we probably engaged in a typical conversation of the “What sort of research do you do?” type that happens in Woods Hole. Possibly we even discussed the fact that both of us enjoyed sailing. At the time I was married, so there was no reason for either of us to have attached any special significance to this meeting. I did note that as a woman scientist, particularly an electrophysiologist, Ann was a rare species at the MBL. When we met again the following summer, my personal situation was completely different and sailing became a more important topic of conversation and activities.

1975–1979: Duke, MIT, and Harvard

In parallel with the effort to make progress in simulations with Ron and Fidel, I continued to work during this time on toxins. In the spring of 1973 I had received a letter from a Princeton undergraduate, Monte Westerfield, asking for a position as a technician. When I discovered he had been voltage clamping a molluscan neuron as an undergraduate, I convinced him to be my graduate student instead. Monte was a creative, imaginative, hardworking, fearless, and productive student. He is now in the Biology Department at the University of Oregon, where he has led the department to eminence in the field of zebrafish neurodevelopment. There Monte established and directs the Zebrafish International Resource Center.

Monte and I worked on various toxins as well as on simulations of morphology (described later). One particularly important toxin was that of the Florida red tide organism, Gymnodinium breve. George Padilla, a colleague in my department, purified the toxin and then Monte, Y. S. Kim (a postdoc of Narahashi’s) and I tested it on squid axons in Woods Hole. In contrast to the New England red tide toxin, saxitoxin, which blocks sodium channels like TTX, the Florida toxin drove the nerve into spontaneous activity by shifting the kinetics of the sodium channel so that it tended to be in the open state. Thus, both red tide toxins acted on sodium channels but differently, albeit both with lethal outcomes for the victim. We also teamed up with Peter Gage who, looking for an excuse to get back to Woods Hole, showed up with the extremely deadly maculotoxin from the little blue-ringed octopus that lives on the Australian coast. We found that maculotoxin had two actions: it blocked the sodium channel (and later analysis proved that one component was TTX), but it also shifted the kinetics. In another summer, Peter brought funnel web spider venom, which turned out also to shift the sodium channel kinetics so that the channel was always open.

We Simulate Propagation Through Morphological Changes

Meanwhile, Ron’s simulation of axonal propagation was truly a major step forward, leading to a long-desired direction for the lab—to be able to explore how channel currents interact with changes in morphology. My dream was to simulate the voltage waveform throughout the whole neuron: in the dendrites, through the cell body, into the axon, and into the axon’s branches.

Over the next few summers at the MBL, Monte joined Ron, Fidel, and me in simulating morphological changes in a neuron in parallel with experiments on the squid axon. These experiments, derived from those with Jose del Castillo, involved threading a wire down a squid axon to short-circuit a region of the axon, effectively making this region one of larger diameter with the resulting larger capacitance. Using a microelectrode, we probed the voltage transients as the impulse propagated from the normal region of the axon into the “large diameter” region and vice versa, observing the temporal and spatial pattern of the voltage. When an impulse in the normal axon attempted to invade the large diameter “soma,” we found an extremely steep temperature dependence that determined whether it succeeded or failed. Our simulations and experimental results agreed almost precisely, giving us confidence in our understanding. Ron, Monte, and I also found a steep temperature sensitivity for antidromic propagation from a branch into the giant axon. Exploring further, we measured and simulated the changes in membrane current in the vicinity of a step change in morphology.

These experiments with antidromic invasion led us naturally to reopen the question of the initiation of the action potential: When a neuron suddenly shrinks from a soma of large diameter into an axon of much smaller diameter, where does the action potential begin? We could stimulate the “soma” through the internal wire and then, with a microelectrode, record the voltage at different positions along the rest of the axon. From these experiments it was clear that the spike always initiated in the portion of the axon adjacent to the larger-diameter portion that mimicked the “soma.” Simulations agreed with the experiments. Further, Monte showed that the membrane could be charged faster in the region of axon adjacent to the “soma” than in either the soma or further out the axon. We concluded that the threshold was lower in the axon segment neighboring a soma by virtue of its faster rate of charging (shorter time constant). We suggested that this consequence of geometry was sufficient for impulse initiation at this site.

Working at the MBL

During these summers we occupied the corner lab on the third floor of Lillie Building that looked over Eel Pond and the old “Supply Department” that housed the tanks of squid, toadfish, dogfish sharks, skates, horseshoe crabs, and other experimental animals. John Valois and his staff in the Supply Department communicated with their boats via a radio transmitter on the Lillie building roof directly above us. The signals from this transmitter occasionally caused surges on our current traces that led us to a quick scramble to turn off the voltage clamp so that the axon would not be “fried.” Luckily these signals were not too frequent. Ah, the peculiarities of working at the MBL in those days! Salt water sometimes leaked from the sea water tables in the labs above, dripping through the floor onto the equipment in the labs below. Huge temperature swings in the animal holding tanks occurred when one investigator increased the flow of sea water to his or her tank, thereby reducing the flow to (and raising the temperature of) another investigator’s tank. Midnight stir-fries of squid mantles, cooked in woks in lab hallways, brought out investigators from their darkened rooms and long experiments. Odoriferous buckets of invertebrate carcasses waited for morning pickup in the hallways. But all of this was simply quaint to those of us who led the charmed life of working at the MBL. In our lab, the spent axons hung down from the ceiling in increasing numbers, a testimony to the incessant and productive work of the summer.

A Major Change in My Personal Life

During the summer of 1975, I met Ann Stuart again. At this point I was essentially a free man and actually dating a little, since Lee had left me and we were in divorce proceedings. Annie, with her student Duane Edgington, was sharing a set of small lab rooms in the Whitman building (now Rowe) with Joel Brown, his postdoc and her dog, and Larry Pinto. It was rather a tight arrangement, especially as colleagues like Phil Dunham and myself were in the habit of increasing the density when stopping by to discuss MBL politics with Joel. It turns out that Annie and I were noticing each other on these visits and inquiring discretely of our colleagues about each other’s “significant other” status. When Annie showed up in my Lillie building lab to inquire about how to voltage clamp her photoreceptor’s presynaptic terminal (later discovered to have been an excuse to get my attention), I was rather pleased. So when I saw her looking for dropped keys one evening on the lawn I became Sir Galahad: I galloped off to a nearby police officer, found that he had indeed picked up the keys as I had hoped, and presented them to Annie with a knightly flourish. We began a little game of trying to bump into each other on the MBL campus that no doubt will be recognized by the many persons who are happy victims of romances started there. When does he/she retrieve mail? Which seminars does he/she attend and how can I position myself to sit near where he/she sits? And so on. By the end of the summer all of this Woods Hole-style courting had paid off and we could often be found sailing together in my Javelin, or swimming together at Stony Beach in the Noctiluca after dark. That summer was somewhat less scientifically productive for both of us!

Sabbatical at MIT

That fall Annie returned to Boston and her lab in the Harvard Neurobiology Department, I returned to Duke, and both of us were miserable. So I asked my long-time friend Jerry Lettvin if I could have some space and an office in his lab at MIT where I could do simulations and write papers (and be close to Annie) on a half-year sabbatical. There, in Jerry’s space, I encountered a sharp young neurologist, one of the first M.D./Ph.D.s, named Steve Waxman. In looking at the nerves from autopsies of patients who had been stricken with multiple sclerosis and then been in remission, Steve had found results of great interest to me: that the internode proximal to the demyelinated region was much shorter than usual. He and I, and his mathematician postdoc (Mike Brill), began to talk about simulating propagation in myelinated fibers, so I asked Ron Joyner to write a program for us to do this. Ultimately Steve and I, with Brill and Ron as coauthors, wrote two papers on propagation in myelinated fibers and its dependence on internodal length. Although Steve and I were together for a relatively short time, we developed a lifelong friendship, and I am delighted when he and his wife Merle occasionally show up at our door on Lillie Road. Steve went on to an illustrious research career as chair of Neurology at Yale and Director of the Research Center at the Veterans Affairs (VA) Hospital. Recently, after receiving the highest scientific honor of the VA, the Middleton Award, Steve gave up the chair at Yale to fully focus on his research at the VA.

Michael Hines Joins the Lab

Around this time, back at Duke in the winter, Joe Blum and I realized that we both needed a professional mathematician programmer. Joe, my former colleague at the NMRI, was now a professor in our physiology department working on the hydrodynamics of ciliary motion and fluid flux, and he wanted to model these processes. We hired a young Ph.D. from the University of Chicago named Michael Hines. Mike pretty much answered Joe’s questions in 2 years, then turned his attention to my problem of simulating a propagating action potential.

The complexity of solving the action potential in space as well as in time––that is, as it traveled along a simple axon of uniform diameter–– required hours, even on the fastest digital machine available. I decided to put into action what I had learned from Art Vance and couple the memory of a digital machine with the speed of an analog machine. So in 1975 the LINC8 in the lab was superseded by an analog-digital hybrid system. It ran along one wall for well over 30 feet: a DEC PDP15 (occupying four relay racks); an analog machine (EAI 690) made by Electronic Associates, a manufacturer of sophisticated analog computers mostly used in the aeronautical industry; a fast, accurate Hybrid Interface (A/D and D/A converters) (EAI 693); and an X-Y plotter.

With it, Mike was able to simulate the action potential traveling down an axon so rapidly that the action potential was just a wave streaking across the oscilloscope screen! Fred Dodge now popped back into the picture again, this time as a site visitor evaluating our grant for renewal. Fred saw the impulse propagating and asked whether we could slow it down so that he could follow it! But when given the problem of solving propagation in a neuron with complex morphology, the hybrid’s speed was limited by the necessity of multiple iterations of the modified Euler method. Soon, however, extraordinary increases in the speed of digital machines, where iterations could be eliminated by implicit numerical integration, caused Mike to move his simulations to a new, small, fast PDP11 DEC computer.

I soon took Mike with me to the MBL. I thought it was important for him to participate in squid experiments for several reasons. First, I wanted him to get a feel for biological variability, not common amongst mathematicians. I thought Mike really needed this sense if he was going to attempt to simulate nerve cells. Second, I wanted to intrigue him with our experiments by having him participate in them. My plan worked well: it helped to give Mike a unique view of how his professional mathematical skills could be applied to neurobiology.

Sabbatical with Ed Kravitz at Harvard

In the spring of 1978, after too many semesters apart, Annie and I at last married and she joined Ed Perl’s Department of Physiology at the University of North Carolina in Chapel Hill. During her transition year, Torsten Wiesel, then the chair of Neurobiology at Harvard, found space for me for an office, and I arranged to work with Ed Kravitz and Silvio Glusman to attempt to understand the basis of facilitation in the presynaptic terminal of the lobster motoneuron. Our plan was to voltage clamp a presynaptic terminal and directly measure the calcium currents to ascertain whether more calcium current entered during the second impulse. While this project ultimately did not succeed, Ed, Silvio and I had a wonderful time together and I started to ponder what happens to calcium in the presynaptic terminal. Our many fruitful discussions stimulated my desire to model the facilitation problem.

At that time it was becoming clear that calcium buffering, as well as calcium extrusion by an ATP-driven pump, must be taken into account in understanding what happened to this important ion after it entered the terminal and caused transmitter release. So I interested my student Norman Stockbridge, a good programmer, in the dissertation project of modeling the complex spatial and temporal distribution of the calcium concentration in a presynaptic terminal. The model was a simplified system including calcium channels, calcium pumps, and intracellular buffering. Mike Hines also became intrigued by calcium, and the two of us eventually wrote a paper together on simulations of calcium entry, binding to a buffer, and being pumped out (Moore and Hines, 1986). We showed that calcium entering the cell accumulates in the buffer not far from the membrane so that a subsequent entry of calcium causes the submembrane calcium concentration to be transiently higher with each additional pulse. The transient concentration change is huge next to the membrane but insignificant at the center of even a 1μm cylinder due to buffering; the transients are damped out with radial distance from the membrane. Indeed, there is residual calcium, but it is away from the region just under the membrane, where the pump pulls the concentration from its high value to a very low value to terminate release.

1979–1985: Photoreceptor Synapse, Lizard Neuromuscular Junction, and NEURON

The Barnacle Photoreceptor Synapse

In the fall of 1979, Annie and I at last found ourselves living in the same state, and even in the same house! We were extremely lucky to purchase a dream house on a lake in Chapel Hill, with great blue heron and a variety of other waterfowl (and, eventually, beavers) right there in our back yard. We continued to migrate to the MBL in the summers and indeed decided in the summer of 1981 to work together there along with Annie’s student Jon Hayashi, measuring the input/out relation at the synaptic terminals of barnacle photoreceptors (Hayashi et al., 1985). This collaboration formed part of Hayashi’s dissertation in which he reported a process of adaptation at this synapse that enabled it to function over a huge dynamic range.

In February 1983 we had a son, Jonathan. Both Annie and I had been invited to give presentations in the coming summer at the International Society of Physiologists meeting in Sydney, Australia, and at a satellite meeting on the Great Barrier Reef. At the tender age of 6 months, Jonathan accompanied us to San Francisco, Hawaii (where we stopped for a week to time-shift and indulge in a mutual passion, windsurfing, assisted by Annie’s mother, Pedie, our babysitter), Sydney, Hayman Island on the Barrier Reef, Fiji, Los Angeles, and back home. It worked so smoothly that we had no hesitation in accepting invitations to speak the next summer in Jerusalem, and Pedie was of course happy to accompany us again as babysitter. But this second trip was not as charmed: while taking time after the meeting to see the Mount of Olives, Annie and Jonathan fell off of a camel when the saddle strap broke. Jonathan was not hurt as he fell on top of Annie; she, on the other hand, ended up having an adventure, first in an Arab hospital and then in Hadassah Hospital, with a broken collar bone and a concussion.

The Lizard Neuromuscular Junction

Annie and I stayed in Woods Hole in the winter of 1985–1986 on sabbaticals and Alberto Mallart joined me there to try to measure currents at the neuromuscular junction (NMJ). At the meeting in Jerusalem, Alberto and I had discovered a mutual interest: he wanted to do simulations and I was intrigued with his preparation, the lizard NMJ, and with his “loose patch” method of measuring currents and release simultaneously. During this collaboration, my postdoc Clark Lindgren came to Woods Hole to learn the lizard preparation. Back home at Duke, Clark and I were able to model and also to measure the pre- and postsynaptic currents at different release sites within the boutons of the NMJ in the same record (Lindgren and Moore, 1989). I later added this work as a tutorial to the Neurons in Action educational software that I published with Annie in order to show students how simulations could assist the interpretation of experimental results. Since finishing his postdoc, Clark has held a faculty position at Grinnell College.

Developing NEURON

At this time, back at Duke, Mike Hines was pushing the limits of simulation software. He had originally been writing programs for the digital computer in FOCAL (for me to use); this had quickly escalated to the CABLE program (in HOC, Higher Order Calculator) that solved the propagation of the action potential along the axon. Now he was expanding and enhancing CABLE, developing it into the NEURON simulation environment (Carnevale and Hines, 2006), a more sophisticated tool that could handle complex morphologies, including tapering diameters and channel densities. Mike had come up with an ingenious way to speed NEURON’s calculations for complex morphologies (Hines, 1984) that now made it possible to simulate a full stylized motoneuron with dendrites, soma, hillock, and myelinated axon. This was a significant advance because NEURON could now handle individual dendrites, not just the collapsed dendritic tree of the Rall model used by Dodge and Cooley. We assigned channel densities to each component of the cell as well as we could from values in the literature, but we had the option of varying the densities to see how the change affected the performance of the neuron. The synaptic inputs on the dendrites could be assigned locations, conductances, and times of onset. When values were assigned on the basis of published current records from voltage clamp steps in motoneuron somata, we could now see that the spike was actually initiated in the axon, not the hillock.

Soon after it was built, I demonstrated this model for Bert Sakmann at the MBL and showed him that simulations indicated that the impulse was actually generated out in the myelinated axon and back-propagated through the soma into the dendritic tree. I was delighted when he and others later observed both generation in the axon and back-propagation in central nervous system (CNS) neurons, verifying the prediction from the simulations. Later Annie and I incorporated this model into our Neurons in Action software.

1990–2007: Conceiving, and Finally Publishing, Neurons in Action

In November of 1990 I was forced by federal law to retire. A delightful fest of the occasion brought a number of good friends and former colleagues to Duke for the day. I was especially surprised and pleased that my NIH grant manager and friend, Gene Streicher, came from Washington for the occasion. Dan Tosteson was the Master of Ceremonies, flying down from Boston, where he was then dean of Harvard Medical School. The talks by Knox Chandler, Toshio Narahashi, Monte Westerfield, and Jim Hudspeth represented different facets of my professional life: Knox from my days in the Cole lab; Toshio, my early collaborator on the TTX experiments; Monte, my former student; and Jim, reflecting the new colleagues I had gained through my marriage to Annie.

Dale Purves (also a long-time friend of Annie’s), who had become chair of the new Department of Neurobiology at Duke (in the new Bryan building opened in 1990), let me retain a lab, an office, and an office for Mike Hines, whose work on NEURON was now supported by the NIH. Mike and I still worked together modeling complete neurons with soma, hillock, and dendrites, but we were focusing on intracellular calcium and neurotransmitter release as well.

Because the movie that Monte, Norm, and I had made in the 1970s was so helpful in visualizing an impulse propagating along an axon, both into and out of a soma, I had earlier urged Mike to program NEURON to display voltages moving in space. Mike did a fabulous job building this movie function into NEURON, and as a result I could now make glorious moving displays on my desktop computer as the simulation progressed. But how could I show these simulations to an audience? These were the days before laptops connected to projectors. In particular, in 1992 I had been invited to give a talk in Genoa, Italy, and wanted some way to show these movies. I made a videotape of the movie displayed on the computer screen and also converted it into European format, enabling me to show my movies in Italy in one format and at seminars in the United States in the other format. Movies became a central feature of the learning tool Neurons in Action, my next big endeavor.

The idea for Neurons in Action (NIA) occurred to me in 1992 when the first Web browser, Mosaic, appeared on the scene. When Mike showed me that NEURON could be launched by clicking a link on a Web page, I had an epiphany regarding teaching. At that time I had been teaching neurophysiology to graduate and medical students using NEURON to show the properties of action potentials. My “lectures” were a series of questions: “What would happen to the amplitude of the action potential if I decreased the external sodium concentration by 50%,” and so on. I changed a NEURON parameter, had the students predict the outcome and vote on the answer, and then ran the simulation to see who was correct. I saw that the students were engaged with the simulations and that misconceptions were cleared up on the spot. My epiphany was to realize that I could write these lectures as tutorials in HTML that a browser could then display and link to NEURON simulations. It would be a new learning tool, with which students could learn as they asked and answered their own questions as well as mine, specifying NEURON’s parameters. It would free the action potential and other neuronal signals from the textbook, where they were stuck in figures.

It took several years to persuade Annie to help me make my dream a reality. She became convinced while assisting me in a lab for Duke medical students and seeing for herself how this new way of learning engaged the students. The early tutorials were very much in my rather playful, but perhaps disorganized, style, with fonts that were different colors or larger or smaller, depending on what I thought needed emphasis. Annie argued that publication would require the style to be more consistent and professional, with more explanation and easier navigation, and she appointed herself the one to impose order on the chaos! As we developed a consistent set of tutorials and added hyperlinked information, she tested our efforts on her own students in both graduate and undergraduate classes and in both lecture and lab settings. By 1998 we were able to submit a prototype to Andy Sinauer that convinced him to publish this unusual book/CD, and at a price affordable by students. We signed a contract with a deadline.

The next 2 years, then, saw a constant, herculean effort to complete this project. The text had to be not only correct but also targeted to explaining the results of the simulations, sometimes counterintuitive. The simulations had to work properly no matter what parameter the user chose. The interface had to be friendly even to an inexperienced undergraduate. During this time our teenage son Jonathan had inserted himself into the project, ultimately becoming so crucial to the effort that we dedicated NIA to him. “Dad,” he said at the start, “your Web pages are terrible––let me do them.” His programming skills made the program work on both the Mac and PC platforms and with both browsers of the time, Netscape and Internet Explorer. Furthermore, he created its graphics and an explanatory movie (available at the Sinauer Associates and NIA Web sites), he designed and still maintains the Web site (http://neuronsinaction.com/), and he became Annie’s HTML tutor. It was a time of very intense, devoted work in the whole family.

Sinauer was just figuring out how to edit a multidimensional project like this one, where many of the pages were not sequential, as in a book, but hyperlinked from a number of different loci. Furthermore, marketing a CD project was novel for Sinauer, so Annie spent literally the entire 1999 meeting of the Society for Neuroscience in the Sinauer booth, explaining our new learning tool to interested faculty and students who stopped by. We finally published NIA in 2000.

In 2004 we obtained a Course, Curriculum, and Laboratory Improvement grant from the NSF that enabled us to completely redesign NIA and its file structure, bringing it in line with changing technology and adding many more tutorials, and Version 2 (NIA2) was published in 2007. This generous grant supported technical help for solving some rather tricky problems as well as a professional evaluation team (whose findings are detailed on the NIA Web site). Jonathan’s increasingly sophisticated programming skills, and his gentle insistence on taking control of Annie and me at certain stages, were crucial in this effort. We are thrilled that our learning tool is being used to teach neurophysiology in undergraduate as well as graduate courses and, indeed, all over the world. I can’t describe my joy in discovering, for example, that the Dali Lama’s monks and nuns, exiled in India, recently used NIA2 in order to understand neuronal signaling, or that it is being used in various courses in African countries.

The Present

I am simply unable to stop working because I enjoy it so much! For example, writing this autobiography made me reflect on the exciting beginnings of computational neuroscience in this country, and how the field has continued to accelerate in parallel with the spectacular advances in computer power, so I was pleased when recently invited to publish an online article on this subject (Moore, 2010). Responding to requests, Annie and I have been designing new tutorials for NIA2 and discussing how to append them to the current version. Additionally, we are working on simulations for a Calcium in Action set of tutorials that explore how channels, pumps, buffers, and diffusion determine the concentration of calcium just under the membrane. Every day I am grateful for Wilson Greatbatch’s pacemaker that keeps me alive and for the luck of having a spouse who shares, and helps me develop, my professional interests and enthusiasms.

How magical can a career be? It has been as if its path was guided by a benevolent hand through college, graduate school, RCA, the NMRI, and the NIH to Duke. In Woods Hole, the underside of the drawbridge used to display infamous graffiti: “Charmed men walk the streets of Woods Hole.” I have always felt that I was one of them. I have had the opportunity to explore electrical and ion channel properties of neurons by doing experiments in parallel with computer simulations. The NMRI, the NIH, Duke, and the MBL gave me the chance to collaborate with many outstanding colleagues from around the globe and to learn from superb students and postdocs, collaborations resulting in lasting friendships. Such memories and friendships remain a source of delight and inspiration.

Acknowledgments

I have attempted, by describing their work and our interactions throughout this biography, to thank my colleagues, students, and postdoctoral fellows for bringing such joy to my work while we experimented and discovered together. I regret that space limitations do not allow me to include everyone by name and note their many contributions to the fullness of my life. I cannot overstate my gratitude for NIH’s support of our efforts for three decades, guided by Gene Streicher. Finally, I am indebted to my soul mate, Annie, who initially suggested that I record the memorable portions of my life and then patiently helped me prepare this autobiography, taking time from her own interests of mentoring students and playing chamber music. We have had as close to a perfect marriage as is possible.

Selected Bibliography

Adrian RH, Chandler WK, Hodgkin AL. Voltage clamp experiments in striated muscle fibers. J Physiol 1970;208:607–644.

Beams JW, Young JLIII, Moore JW. The production of high centrifugal fields. J Applied Physics 1946;17:886–89

Brill MH, Waxman SG, Moore JW, Joyner RW. Conduction velocity and spike configuration in myelinated fibers: Computed dependence on internode distance. J Neurol Neurosurg Psychiatr 1977;40:769–774.

Buchwald HD, Durham L, Fischer HG, Harada R, Mosher HS, Kao CY, Furhman FA. Identity of tarichatoxin and tetrodotoxin. Science 1964;143:474–475.

Carnevale NT, Hines ML. The NEURON Book. Cambridge, UK: Cambridge University Press, 2006. [Database]

Chandler WK, Hodgkin AL. The effect of internal sodium on the action potential in the presence of different internal anions. J Physiol 1965;181:594–611.

Cole KS. Membranes, Ions, and Impulses. Berkeley & Los Angeles, CA: University of California Press, 1968

Cole KS, Moore JW. Liquid junction and membrane potentials of the squid giant axon. J Gen Physiol 1960;43:971–980.

Cole KS, Moore JW. Ionic current measurements in the squid giant axon membrane. J Gen Physiol 1960;44:123–167.

Cole KS, Moore JW. Potassium ion current in the squid giant axon: Dynamic characteristic. Biophys J 1960;1:1–14.

Cooley JW, Dodge FA Jr. Digital computer solutions for excitation and propagation of the nerve impulse. Biophys J 1966;6:583–599.

Coombs JS, Curtis DR, Eccles JC. The generation of impulses in motoneurones. J Physiol 1957;139:232–249.

Curtis HJ, Cole KS. Membrane resting and action potentials from the squid giant axon. J Cell Comp Physiol 1942;19:135

del Castillo J, Moore JW. On increasing the velocity of a nerve impulse. J Physiol 1959;148:665–670.

Dodge FA Jr, Cooley JW. Action potential of the motoneuron. IBM J Res Dev 1973;17:219–229.

Fishman HM. Direct and rapid description of the individual ionic currents of squid axon membrane by ramp potential control. Biophys J 1970;10:799–817.

Gage PW, Moore JW. Synaptic current at the squid giant synapse. Science 1969;166:510–512.

Gage PW, Moore JW, Westerfield M. An octopus toxin, maculotoxin, selectively blocks sodium current in squid giant axons. J Physiol 1976;259:427–443.

Greatbatch W. The Making of the Pacemaker. Amherst, NY: Prometheus Books, 2000.

Hayashi JH, Moore JW, Stuart AE. Adaptation in the input/output relation of the synapse made by the barnacle’s photoreceptor. J Physiol 1985;368:179–195.

Hines ML Efficient computation of branched nerve equations. Int J Biomed Comput 1984;15:69–76.

Hodgkin AL, Huxley AF. Resting and action potentials in single nerve fibres. J Physiol 1945;104:176–195.

Hodgkin AL, Katz B. The effect of sodium ions on the electrical activity of giant axon of the squid. J Physiol 1949;108:37–77.

Joyner RW, Moore JW. Computer controlled voltage clamp experiments. Ann Biomed Eng 1973;1:368–380.

Joyner RW, Moore JW, Ramon F. Axon voltage-clamp simulations. III. Postsynaptic region. Biophys J 1975;15:37–54.

Joyner RW, Ramon F, Moore JW. Simulation of action potential propagation in an inhomogeneous sheet of coupled excitable cells. Circ Res 1975;36:654–661.

Joyner RW, Westerfield M, Moore JW. Effects of cellular geometry on current flow during a propagated action potential. Biophys J 1980;31:183–194.

Joyner RW, Westerfield M, Moore JW, Stockbridge N. A numerical method to model excitable cells. Biophys J 1978;22:155–170.

Julian FJ, Moore JW, Goldman DE. Membrane potentials of the lobster giant axon obtained by use of the sucrose-gap technique. J Gen Physiol 1962a;45: 1195–1216.

Julian FJ, Moore JW, Goldman DE. Current-voltage relations in the lobster giant axon membrane under voltage clamp conditions. J Gen Physiol 1962b;45: 1217–1238.

Kao CY, Fuhrman FA. Pharmacological studies on tarichatoxin, a potent neurotoxin. J Pharmacol Exp Ther 1963;140:31–40.

Katz B, Miledi R. A study of synaptic transmission in the absence of nerve impulses. J Physiol 1967;192:407–436.

Katz B, Miledi R. Tetrodotoxin-resistant electric activity in presynaptic terminals. J Physiol 1969;203:459–487.

Lindgren CA, Moore JW. Identification of ionic currents at presynaptic nerve endings of the lizard. J Physiol 1989;414:210–222.

Meryman HT, Moore JW. The detection and measurement of freezing in tissue. J Applied Physiol 1953;6:12–21.

Moore JW. A personal view of the early development of computational neuroscience in the USA. Front Comput Neurosci 2010;4:20. doi: 10.3389/fncom.2010.00020. http://www.frontiersin.org/computational_neuroscience/10.3389/fncom.2010.00020/abstract

Moore JW. Electronic control of some active bioelectric membranes. Proc IRE 1959;47:1869–1880.

Moore JW. Operational amplifiers. In: Nastuk WL, ed. Physical techniques in biological research. Academic Press, NY: 1963;6:77–97.

Moore JW Voltage clamp studies on internally perfused axons. J Gen Physiol 1965; 48:11–17.

Moore JW, Blaustein M, Anderson NC, Narahashi T. Basis of tetrodotoxin’s selectivity in blockage of squid axons. J Gen Physiol 1967;40:1401–1411.

Moore JW, Cole KS. Membrane potentials of the squid giant axon in vivo. Fed Proc 1955;14:267–276.

Moore JW, Cole KS. Resting and action potentials of the squid giant axon in vivo. J Gen Physiol 1960;43:961–970.

Moore JW, Cole KS. Voltage clamp techniques. In: Nastuk WL, ed. Physical techniques in biological research. New York, Academic Press: 1963;6:263–321.

Moore JW, Cox EB. A kinetic model for the sodium conductance system in squid axon. Biophys J 1976;16:171–192.

Moore JW, del Castillo J. An electronic electrode. Inst Radio Engrs Natl Conv Rec 1959;7,Part 9:47–50.

Moore JW, Gebhart JH. Stabilized wide-band potentiometric preamplifiers. Proc IRE 1962;50:1928–1941.

Moore JW, Harris EM. Voltage clamp data processing. In Agin D, ed. Perspectives in membrane biophysics. New York: Gordon and Breach Science Publishers, Ltd. 1972;169–185.

Moore JW, Hines ML. Some consequences of intracellular calcium binding on the phasic synaptic transmitter release. In Rahamimoff R, Katz B eds., Calcium, neuronal function and transmitter release. Boston: Martin Nijoff 1986:115–140.

Moore JW, Joyner RW, Brill MH, Waxman SG. Simulations of conduction in uniform myelinated fibers: Relative sensitivity to changes in nodal and internodal parameters. Biophys J 1978;21:147–160.

Moore JW, Narahashi T. Tetrodotoxin’s highly selective blockage of an ionic channel. Fed Proc 1967;26:1655–1663.

Moore JW, Narahashi T, Shaw TI. An upper limit to the number of sodium channels in nerve membrane? J Physiol 1967;188:99–107.

Moore JW, Narahashi T, Ulbricht W. Sodium conductance shift in an axon internally perfused with a sucrose and low-potassium solution. J Physiol 1964;172:163–173.

Moore JW, Ramon F. On numerical integration of the Hodgkin and Huxley equations for a membrane action potential. J Theor Biol 1974;45: 249–273.

Moore JW, Ramon F, Joyner RW. Axon voltage-clamp simulations. I. Methods and tests. Biophys J 1975a;15:11–24.

Moore JW, Ramon F, Joyner RW. Axon voltage-clamp simulations. II. Double sucrose-gap. Biophys J 1975b;15:25–36.

Moore JW, Stockbridge N, Westerfield M. On the site of impulse initiation in a neurone. J Physiol 1983;336:301–311.

Moore JW, Stuart AE. Neurons in Action: Computer Simulations with NeuroLab. Sunderland, MA: Sinauer Associates, 2000.

Moore JW, Stuart AE. Neurons in Action Version 2: Tutorials and Simulations Using Neuron. Sunderland, MA: Sinauer Associates, 2007.

Moore JW, Ulbricht W., Takata M. Effect of ethanol on the sodium and potassium conductances of the squid axon membrane. J Gen Physiol 1964;48:279–295.

Moore JW, Westerfield M. Action potential propagation and threshold parameters in inhomogeneous regions of squid axons. J Physiol 1983;336:285–300.

Narahashi T, Anderson NC, Moore JW. Tetrodotoxin does not block excitation from inside the nerve membrane. Science 1966;153:765–767.

Narahashi T, Anderson NC, Moore JW. Comparison of tetrodotoxin and procaine in internally perfused squid giant axons. J Gen Physiol 1967;50:1413–1428.

Narahashi T, Moore JW, Scott WR. Tetrodotoxin blockage of sodium conductance increase in lobster giant axons. J Gen Physiol 1964:47;965–974.

Narahashi T, Moore JW, Shapiro BI. Condylactis toxin: Interaction with nerve membrane ionic conductances. Science 1969;163:680–681.

Narahashi T, Moore JW, Poston RN. Tetrodotoxin derivatives: Chemical structure and blockage of nerve membrane conductance. Science 1967;156:976–979.

Pickard WF, Lettvin JY, Moore JW, Takata M, Pooler J, Bernstein T. Cesium ions do not pass the membrane of the giant axon. Proc Natl Acad Sci USA 1964; 52:1177–1183.

Ramon F, Anderson N, Joyner RW, Moore JW. Axon Voltage-clamp simulations. IV. A multicellular preparation. Biophys J 1975;15:55–69.

Ramon F, Joyner RW, Moore JW. Propagation of action potentials in inhomogeneous axon regions. Fed Proc 1975;34:1357–1363.

Ramon F, Moore JW. Ephaptic transmission in squid giant axons. Am J Physiol 1978;234:C162–C169.

Ramon F, Moore JW. Propagation of action potentials in squid giant axons. The effect of membrane inhomogeneities. J Gen Physiol 1979;73:595–603.

Stockbridge N, Moore JW. Dynamics of intracellular calcium and its possible relationship to phasic transmitter release facilitation at the frog neuromuscular junction. J Neurosci 1984;4:803–811.

Stuart AE, Hayashi JH, Moore JW, Davis RE. Currents in the synaptic terminals of barnacle photoreceptors. In Rahamimoff R, Katz B, eds., Calcium, neuronal function and transmitter release. Boston: Martin Nijoff 1986:443–455.

Takata M, Moore JW, Kao CY, Fuhrman FA. Blockage of sodium conductance increase in lobster giant axon by tarichatoxin (tetrodotoxin). J Gen Physiol 1966;49:977–988.

Takata M, Pickard WF, Lettvin JY, Moore JW. Ionic conductance changes in lobster axon membrane when lanthanum is substituted for calcium. J Gen Physiol 1966;50:461–471.

Tasaki I, Luxoro M. Intracellular perfusion of Chilean giant squid axons. Science 1964;145:1313–1315.

Westerfield M, Moore JW, Kim YS, Padilla. How Gymnodinium breve red tide toxin produces repetitive firing in squid axons. Am J Physiol 1977;232:C23–C29.

Westerfield M, Joyner RW, Moore JW. Temperature sensitive conduction failure at axon branch points. J Neurophysiol 1978;41:1–8.

Whitcomb ER, Friess SL, Moore JW. Action of certain anticholinesterases on the spike potential of the desheathed sciatic nerve of the bullfrog. J Cell Comp Physiol 1958;52:275–300.

Robert Y. Moore

BORN:

Harvey, Illinois

December 5, 1931

EDUCATION:

Lawrence University, B.A. (1953)

University of Chicago, M.D. (1957), Ph.D. (1963)

Resident in Neurology (1963)

APPOINTMENTS:

Instructor in Anatomy to Professor Anatomy and Neurology, University of Chicago (1959–1974)

Professor, Department of Neurosciences, University of California San Diego (1974–1979)

Professor and Chair, Department of Neurology, SUNY, Stony Brook (1979–1990)

Professor, Departments of Neurology and Psychiatry, University of Pittsburgh (1990–1996); Chair of Neurology (1996–2000)

Love Family Professor of Neurology and Neuroscience, University of Pittsburgh (1998–2010)

HONORS AND AWARDS (SELECTED):

Markle Scholar in Medical Science (1964–1969)

M.D. (Honoris causa), University of Lund, Sweden (1974)

President, The Cajal Club (Society of Neuroanatomists) (1990–1992)

C.U. Ariens-Kappers Medal, Netherlands Institute for Brain

Research, Royal Netherlands Academy of Science (1991)

President, Society for Research on Biological Rhythms (1992–1994)

Farrell Prize in Sleep Medicine, Harvard Medical School (2010)

Member, President’s Committee on the National Medal of Science (2006–2011)

Robert Moore became intrigued with the concept of localization of function in the brain, and its implications for medicine, as an undergraduate. After early work on the neurobiology of memory, he studied the organization of mammalian auditory and visual systems. This led to studies of the neural control of circadian timing, resulting in discovery of a direct retinohypothalamic tract specialized to mediate entrainment. Subsequent studies showed that selective ablation of the suprachiasmatic nuclei resulted in a loss of circadian function, evidence that the nucleus is a circadian pacemaker, and this has formed a basis for a continuing investigation of a brain circadian timing system. Description and analysis of the circadian timing system has continued in his laboratory along with extensive anatomical studies of the organization of brain systems producing monoamines. Over the last 10 years, he has extended this work to imaging studies of the dopamine systems in Parkinson’s disease. Throughout his career, he has practiced and taught neurology, and care of patients has been an important component of his activities.

Robert Y. Moore

Parents and Early Years

My father, Raymon Irwin Moore, was born on a farm in Powder Springs, Georgia, on June 20, 1904. Powder Springs is north of Atlanta, close to the now prosperous town of Marrietta. His father was Autry Cole (called “AC”) Moore, born on the same farm in about 1865. My family had owned the farm since at least the Civil War, and it contained, not far from the farmhouse, the remains of trenches and fortifications built by Hood’s army, the Confederates, for the Battle of Atlanta in 1864 during Sherman’s march to the sea. I remember playing in them as a child. The family story, for which I have no proof, is that the Moores came to Georgia in the first group of prisoners with Oglethorpe (the prisoners were from debtor’s prison and were transported to colonies as indentured servants) in the 1730s and had begun farming when released from their obligations. This was in an area of poor soil fertility, and their lives were ones of subsistence farming. My father was the fourth of five boys and, with no prospects of inheriting the farm, he was sent to a residential training school for the poor to obtain an education. After finishing high school, he moved to Chicago in the early 1920s to find employment. After some temporary jobs, he was taken on as a clerk by the Continental Illinois Bank and Trust Company. It was there he met my mother, Marie Louse Fisher, born on September 11, 1904, in Maquoketa, Iowa, a small farm town in eastern Iowa. My grandfather, Harry C. Fisher, was the son of German immigrants and owned the town lumberyard. He was the fire chief as well and had a siren on his car, very compelling for a young child. He also taught me to play golf, a lifelong but rarely fulfilled obsession.

I was born at the Ingalls Memorial Hospital in Harvey, Illinois, a southern suburb of Chicago. My parents lived in an apartment in Blue Island, Illinois, next door to my mother’s maternal aunt and uncle, for 4 years after I was born, and my earliest memory is of a visit from the iceman. We had a real icebox kept cold by a block of ice delivered by a man with a black rubberized shawl over his back upon which a block of ice was held with great pincers. I have no other memories from that age, and we moved to Atlanta when I was 5 because my father was employed as a salesman by the Burroughs Adding Machine Company (a company that made a variety of business machines but was absorbed into Unisys subsequently). He was eager to return to the area of his home and we moved to an apartment in Atlanta just off Peach Tree Street. I remember the apartment and fragments of the neighborhood. It must have been integrated to some extent because I remember playing often with a little “colored” girl. I attended kindergarten but failed and had to repeat it. I probably would be designated as having attention-deficit behavior now but such niceties were unavailable at the time and I suspect I was called “slow.” I had one frightening experience that I still remember vividly. On my way home from school I was stopped by a group of older boys, tied up, and taken to an abandoned building where one of the group dropped hot candle wax on my thigh. I screamed so loudly that the boys fortunately let me go. I reported this to my father, but the boys were apparently not local and could not be identified. From Atlanta, we moved to Detroit, quite a nice city in those days. We lived in an apartment near 9 Mile Road, north of the city center. It was a pleasant area away from heavy traffic and I learned to ride a bicycle. School was a several-block walk and I remember a problem with a teacher who objected to my left-handed writing. Neither she nor my parents were able to convince me to change. I did second and third grade there and my reading became sufficiently proficient that I could read fiction of some complexity. My father purchased a Modern Library edition of Mark Twain’s Tom Sawyer and Huckleberry Finn for me and I was enthralled, particularly with Tom Sawyer (Huckleberry Finn was a bit too deep for an 8-year-old). I read them over and over. At one point, my records indicated that I had read Tom Sawyer 56 times. The experience turned me into a reader.

My only sibling, Jim, was born in 1938 in Detroit but, as he was 7 years younger, we did not do much together until he was much older. One experience that started during our period in Detroit was a series of operations, performed at St Louis Children’s Hospital, to repair a congenital anomaly of the penis called hypospadias. These were excruciatingly painful and I dreaded the operations. My father was transferred again by his employer in 1939 and we moved to St. Louis, settling into an apartment on the then outskirts of the city. A few memories remain about the times; I was learning that we lived in a world and that things happening at a distance had direct effects on us. I remember the 1940 presidential campaign, Roosevelt and Willkie, well. All parents seemed to have strong feelings about FDR, pro or con and the election, in the midst of the very menacing start of World War II in Europe, was a subject of conversation among children as well. The events of the Pearl Harbor attack on December 7, 1941, seemed menacing, even for a newly 10-year-old. It seemed ominous. Rationing began, of gasoline in particular, and, at times, there was relatively little meat available. My family was not prosperous during this era, and we ate some things that were not food to my mind at the time. I became fascinated by sport; hours and hours passed with baseball, football, and a game called “corkball,” played with a small ball, slightly larger than a golf ball made of cork wrapped in leather, and a long thin bat. Its advantage was that four boys and girls could have a good game in a small area without risk of broken windows.

Our family finances were strained, and it was clear to me that I needed a source of income. An opportunity to sell magazines door to door came my way and I took it. Very rapidly I learned that interruption of the dinner hour by a magazine-carrying urchin was not greeted enthusiastically. The best time was afternoon, after school, and before the man of the house returned from work. The magazines sold for 10 or 15 cents and I received 30%. In time, this went so well that I became the distributor, employing other boys. My major entertainment in the summer months, besides playing with pals, was a thing called the “Knothole Gang.” St Louis at that time had two baseball teams, the Cardinals and the Browns, and all games were played at Sportsman’s Park. If one took a birth certificate to the ticket office, a membership card for the Knothole Gang was issued which permitted, for day games, admission to the game for the cost of tax on a ticket, 5 cents. After a modest walk from our apartment to a main road, a streetcar to the ballpark was 5 cents, popcorn at the game 10 cents so that, for 25 cents, a small boy could go to the baseball game with transportation, entertainment, and nourishment all included. I am now at about 1939 and 1940. In 1942, my father applied for a job with a company headquartered in Cleveland, the Snapout Forms Co., a maker of business forms, to head a new sales office in Chicago. It was a good time for jobs for men above age for military service, and my father had just missed both great wars as I did World War II and Vietnam. He and my mother were pleased to be able to return to Chicago. We settled in a suburb immediately northwest of the city, Park Ridge, for the first time in our own house. It was adjacent to a zone called the “Forest Preserve,” a large area of preserved parkland surrounding the city of Chicago, a kind of public accomplishment that our current politicians would be incapable of making. My parents continued to live there until the late 1970s when both required nursing homes.

Education and Life in the Suburbs

The local schools in Park Ridge were quite good, but I was not a successful student, failing all courses in eighth grade. An IQ test was administered and the principal informed my parents that I was too bright to be failing in school and he was sending me to high school. For the first 2 years I managed a C+ average but, for no reason I can remember now, everything suddenly seemed easily accomplished and it was high grades from then on. My major preoccupations were sports and reading. In junior high school, we played basketball essentially year round, mixed with some baseball and football. In high school I tried out for the football team, but it was soon apparent to me, and the coach, that I was not big enough, strong enough, fast enough, or coordinated enough to succeed at that sport. There were no such requirements for cross-country running and that became my fall sport, followed by indoor track in the winter and golf in the spring. In my last 2 years in high school there were few days when I went directly from school to home. In the summers from 12 to 16, I worked as a golf caddy. A friend who lived nearby would meet me at 5 a.m., and we walked the 1.5 miles to the golf course to be the first there as the work assigned by the caddy master was on a first-come, first-served basis. Being a caddy allowed us to use this very nice private course on Monday mornings, a help for my golf game. The job also provided a fine insight into the vagaries of human behavior. After I was 16, I worked in factories and hospitals in the summers. These were always interesting for many reasons and taught me a lot. I gave up factories after two summers with little interest in the monotony of factory work and a profound dislike, really abhorrence, of labor unions.

In my last 2 years of high school, I became increasingly interested in literature, but it was more than evident to me that I had no talent for creative writing. In searching for a surrogate activity, I came across literary criticism and this led me to attend Kenyon College, a small men’s school at that time in Gambier, Ohio, well known for a program in that discipline. The education was excellent, but I was not happy with the location of the school in a town of 500 and an all-male student body. My best friend from high school was attending Lawrence College in Appleton, Wisconsin, and was happy there, so I transferred. I could not have made a better choice. Lawrence was, and continues to be, an excellent university with high standards and a faculty of very dedicated scholars and teachers. My education at Lawrence was a transforming experience. Classes were small and I became deeply interested in the brain through courses in biology and psychology. One professor in particular, John Bucklew, took an interest in me and taught me in individual tutorials over my last 2 years. These were largely devoted to reading and discussing a broad literature on brain function. I became fascinated by the concept of localization of function and that has been maintained. In my senior year I struggled with the choice between a Ph.D. or medical school. My mother and father were, of course, eager to have a doctor in the family, but I felt certain that I wanted to do research. I applied to a few Ph.D. programs and several medical schools and was accepted by all. At an interview at the University of Illinois School of Medicine, the interviewer suggested that I should consider the University of Chicago because I would be able to do both degrees there. I took the recommendation and have always been grateful for it. My last semester in college revealed a problem that has recurred intermittently ever since. In the late winter of 1953, I developed episodes of severe, unremitting fear. I was agitated, unable to sleep, and had great difficulty concentrating. Fortunately, I had no regular classes and my only unfulfilled requirement was a dissertation. Writing the dissertation was difficult, but I could do it and finished all that was needed to graduate. Shortly after the symptoms began, I visited home and my father took me to a psychiatrist who spent a few minutes talking to me and recommended sedatives. The problem was what is now designated panic disorder; it was called acute anxiety attacks at the time. The symptoms gradually resolved, and I entered medical school without difficulty. Since that initial attack, I have had occasional recurrences, but none so severe. Instead, I have had intermittent episodes of depression. These all cleared with time, but I have certainly had repeated visits from what Dr. Samuel Johnson referred to as his “black dog.” Since the development of the selective serotonin reuptake inhibitors (SSRIs), this has rarely been a problem.

My medical education at the University of Chicago was a very different experience from that of friends at other schools. Medical students were viewed as graduate students at Chicago and took preclinical courses designed as graduate courses. There was no clinical content for the most part and we saw no patients until the third quarter of the second year. In addition, there were elective courses in which any subject was allowed; a roommate took a course in art history. I took the opportunity to begin research and worked in the laboratory of Austin Riesen, a neuropsychologist who had discovered the effects of early visual deprivation on the development of the visual system in monkeys. As I found was typical of the University of Chicago, Riesen was perfectly happy to let me design my own experiment and conduct it with his funds and facilities. These were early days in the discovery of adrenal corticosteroids and Hans Selye’s development of the concept of a stress syndrome with adrenal responses. My hypothesis was that adrenal responses would be necessary for aversive learning. I was taught how to do rat adrenalectomies by Dwight Ingle, a pioneer adrenal physiologist, and was able to do the experiment in the course of the quarter. Although the results were negative, I felt I had begun a career. My father was willing to support me for the summer and I went to work on another project with Howard Hunt, another neuropsychologist who had had some graduate training with B. F. Skinner and was introduced to the use of operant behavior paradigms. In all, I worked with Howard for about 6 years, summers, weekends, vacations and electives, and a year following graduation from medical school to complete a Ph.D.

The liberal program of the University of Chicago was again a blessing because my entire senior year in medical school was elective. My grades had been good except for gross anatomy, which I barely passed, and my junior year clinical grades had been outstanding. I was elected to Alpha Omega Alpha, as I had been to Phi Beta Kappa, and the medical school seemed perfectly happy to allow me to do as I pleased. I elected to do no clinical work and concentrated on research completing the work for my thesis during that year and a subsequent postdoctoral year. Thus, contrary to present programs, I was able to do an M.D.-Ph.D. in 5 years. My thesis was driven conceptually by the finding of Scoville and Milner that bilateral hippocampal lesions in man produced a severe and permanent deficit in short-term memory. The hypothesis was that hippocampal lesions in animals would have the same effect and provide an animal model for memory research. Once again, I made a mistake in experimental design and chose to use a negative reinforcement paradigm and hippocampal ablation in cats. By this time I had become a very skilled animal neurosurgeon and the experiment was quire lovely but, again, negative (Moore, R.Y. Effects of some rhinencephalic lesions on retention of conditioned avoidance behavior in cats. J. Comp. Physiol. Psychol., 57:65–71, 1964). Thus, this early venture into science was not rewarding with respect to positive outcomes but was rewarding in every other aspect. As time went on during my training, I became increasingly interested in neuroanatomy and began to collaborate with students working in the laboratory of W. D. Neff, a neuropsychologist studying the auditory system. Neff and an associate, Irving Diamond, did some anatomical studies and had an active lab in which I was taught anatomical techniques. I was a graduate assistant in a human neuroanatomy course my senior year in medical school and was allowed to give a number of the lectures in the course the following year. Neuroanatomy at that time was a course with 40 lectures and 90 hours of laboratory, all taught by one faculty member, a teaching load that would be derided now. It was evident to me from the beginning that teaching was the most efficient way to become broadly knowledgeable in a subject in a short time.

On entry to medical school, I had believed that the proper specialty for my interests would be psychiatry, but lectures on human behavior given by the Department of Psychiatry prompted further consideration. The department had become very Freudian, and I vividly remember one lecture in which it was proposed that one example of the success of psychoanalytic theory was the realization that asthma represented the calling out of a child for its mother. Even in my naiveté I knew that something was wrong with that idea. In that era, the first 2 years of medical school were basic science with little clinical correlation. One clinical experience available to all students was a weekly presentation of a patient by Dr. Douglas Buchanan. Buchanan was a Glaswegian educated at Cambridge who took neurological training at the famous National Hospital for the Epileptic and Insane, as it was then called, Queen Square, London. When he finished in 1931, there were few positions in England, and he was hired at the University of Chicago as a neurologist for children. Prior to 1927, the University of Chicago offered only 2 years of training for medical students who then went to Rush Medical College for the last 2 years. The University had planned for several years to open a 4-year medical school based on the recommendations of the famous “Flexner Report” that was quite critical of American medical education and made recommendations for an ideal medical school and curriculum. These included having a full-time faculty, both basic science and clinical. To meet this objective, the University built its own hospital adjacent to the main campus and hired the faculty. Buchanan was one of these pioneers. The University of Chicago Hospitals and Clinics opened in 1927 and each of the general clinical services, medicine, surgery and pediatrics, was allotted a position for a neurologist. Child neurology was an unknown field at the time; pediatricians or general physicians cared for most children with neurological disorders. Through his vast experience at Chicago, and his skills as an educator, Buchanan became one of the three founders of child neurology, now a vigorous subspecialty. At the time I went to the University, he had trained more than a third of the child neurologists in the country. He was the most captivating teacher I have ever known. In addition to ward and clinic teaching, he made a Saturday morning presentation each week during the academic year in a lecture hall with 120 seats. The class was entirely elective, but the hall was filled every Saturday morning. After presenting a case and performing an examination, Buchanan would discuss it. These were far-ranging discussions, often with a good deal of history. What was evident to all was how much he cared about the patient and how deeply he was devoted to scholarship and education. In my clinical training, I was also captivated by the teaching of Richard B. Richter, whom I will discuss later. The two of them made a convincing argument for becoming a neurologist.

Following my postdoctoral year, I did a rotating internship at the University of Michigan with a focus on neurology. This was rigorous. Upon arrival, we were informed that vacations were too hard to schedule, but we would receive one month’s salary ($117) in lieu of vacation. We were on call every other night and spent a lot of time in the hospital on those nights. I lived in the hospital, in the intern’s quarters, sharing a room. We were charged $30/month rent and were required to pay for our own food. It was good to be young with no responsibilities. At the University of Chicago, I had learned about the work of C. Judson Herrick, an eminent neuroanatomist who made the standard classification of cranial nerves and wrote many papers and books. At Michigan I learned that he lived with his daughter, a dermatologist in Grand Rapids, and, even at an advanced age, was still writing. I had the opportunity to spend 2 months at St Mary’s Hospital in Grand Rapids as an intern in pediatrics. I contacted his daughter to inquire whether I could meet the great man, and she invited me for dessert one evening and, subsequently, to his 90th birthday party later in the month. I was awed by his insight into structure–function relationships in brain and nearly overwhelmed by the birthday party held on a sunny autumn day and attended by great neuroscientists from around the world.

Despite the heavy schedule, I was bored by internship duties and went to the Department of Psychology to meet Robert Isaacson, a young faculty member, who wanted to do some work on brain and behavior but had not done animal surgery. We had a good experience together and the collaboration led to a publication (Isaacson, R.L., Douglas, R.J., and Moore, R.Y. The effect of radical hippocampal ablation on acquisition of avoidance response. J. Comp. Physiol. Psychol., 54:625–628, 1961).

During my internship, I was contacted by Chicago and offered a position on completion of my training in Michigan as instructor in the Department of Anatomy with my own laboratory, and funding to start, with half of my time to be spent as resident in Neurology. Thus began a career in research, teaching, and clinical medicine I have enjoyed ever since. As a special pleasure, I found that the lab I was assigned had been Herrick’s. For the first 6 months I took my place as neurology resident. My laboratory was having some minor renovation, and I was ordering equipment and other essentials to start research. At that time, the summer and fall of 1959, I was the only resident in the program, a heavy load, and I was on night call every other night and every weekend. Somehow it did not seem so bad at the time. It helped not to be married. Another resident started in January 1960, and the strain was greatly relieved.

Neurology at that time was a Division in the Department of Medicine with three faculty members. Richard B. Richter was the chief. I have seen neurologists at work now for 50 years, all over this country and in Europe, but he was the best clinician I have ever seen. His style was deductive, not intuitive. Histories were precise and organized. His neurological examination was appropriate to the situation but always detailed, frequently lasting more than an hour. When one worked with him, he expected the same detailed approach, and I quickly caught on. He was a terror for medical students because he expected their work to be similarly performed, requiring from each student a detailed and organized history and examination and a deductive process formulating a differential diagnosis. He was not sympathetic to those who did not perform. When I responded to a question from him once about a rather weak medical resident applying to the neurology program with a statement that he was a very kind and diligent fellow, he responded, “Fortunately, that’s not good enough.” His research was in neuropathology and all of the hospital neuropathology was done in neurology.

One of my proudest moments as a trainee was when he asked me to join him in writing a paper (Richter and Moore, 1968). The other two faculty members were Sidney Schulman and Charles Barlow, both superb clinicians. Schulman was in the mold of Richter, precise, patient, deductive. Barlow, like Buchanan, was an intuitive neurologist who often took little time but nearly always reached the right conclusions. After my second year, Barlow left to become the Bronson Crothers Professor of Neurology at Boston Children’s. This was shortly before Buchanan was scheduled to retire and, as I had spent more time than anyone in the program with Buchanan, I was asked to succeed Barlow on completion of my training and to take over the Child Neurology Division on Buchanan’s retirement. It came with a great fringe benefit; the medical center had just built a new children’s hospital with incredible laboratory space and I moved into 3000 square feet of brand new space. At that time, there was a dispute among neurologists and pediatricians about the proper training of a child neurologist. Was the basic emphasis to be neurology or pediatrics? This was not decided until the late 1960s when a committee was appointed by the American Academy of Neurology to discuss and design a curriculum for training child neurologists. I was one of the committee and a final task for us was to have the cooperation and consent of the American Academy of Pediatrics for neurology to establish a special training program to be accredited by the Accreditation Council for Graduate Medical Education (ACGME). The head of the pediatric division of the ACGME at that time was F. Howell Wright, one of my regular squash partners and my children’s pediatrician. I was delegated by our committee to discuss the situation with him, and that together with subsequent input from others, resulted in the decision that the regulation of training in child neurology would rest with neurology. I began my full-time appointment in January1964, as Assistant Professor of Neurology, Pediatrics and Anatomy. Douglas Buchanan and Richard Richter both retired in 1966, initiating a new era without the founding chiefs with clinical duties of inpatient attending 4 months a year and outpatient clinic 3 half days a week.

A Career in Research

By the spring of 1960 my laboratory was equipped and ready to function, and I hired my first technician. Never having had that experience, and recognizing the importance of making a good choice, I sought advice from my neighbor on the first floor of the Anatomy Building, Isadore Gersh, one of the pioneers in posterior pituitary anatomy and function. Gersh was brief, stating, “You should hire a middle-aged woman who is an immigrant and a Roman Catholic.” This characterized his technicians aptly and they were noticeably industrious, but I was puzzled. I told him I understood the middle age and immigrant status but, as Gersh was clearly Jewish, the reason for the Roman Catholic requirement eluded me. His reply was, “Bob, they work not only for you but for God.” My first technician was a woman from Latvia who had lost her husband in World War II and spent 5 years in a refugee camp in Germany before coming to America. She was a gem as were all but one of the additional technicians hired using the same criteria. With a laboratory, equipment, and staff, it was time to begin research. My objective was to follow the example then being established by Walle Nauta with his work placing connectionist neuroanatomy into a strong functional context. Nauta had recently developed the most powerful anatomical tract tracing method available (Nauta, W.J.H., and Gygax, P.A. Silver impregnation of degenerating axons in the central nervous system: A modified technique. Biotech. Histochem. 1954; 29:91–93), and I began to attempt to use it. Despite long, and intensive efforts, I was unable to stain degenerating axons and by the fall of 1960 I was quite discouraged. The 7th International Congress of Anatomy was held in New York that fall and funds permitted attendance. I took the train from Chicago to New York with the new experience of spending the trip in a roomette, a small space containing a seat, a toilet, and a bed that folded down from the ceiling at night. Shoes were placed at bedtime in a small cubicle and miraculously appeared in the morning shined. The train was called the 20th Century Limited, and in the morning it rolled along the Hudson River, a beautiful sight. I had never been to New York and that added to the pleasure of a wonderful experience with two high points. The first was meeting Walle Nauta. He gave a talk in one session and I waited after it to inquire whether I might ask him some questions about his method. This was at noon and, forsaking lunch, he sat down and asked me about my experiences with it. Learning of my frustration, he asked me to take some notes and for the next 2 hours he took me though the method in detail with numerous “if this goes wrong, you do that” and so on. When I returned to Chicago, all went as he had expected and I never had a problem with the method again. The second highlight of the trip was the meeting banquet. Somehow, the anatomists had managed to obtain exclusive use of the Metropolitan Museum of Art for the evening. As I was entering the museum, Nauta and another neuroanatomist of Dutch origin, Hans Kuypers, were also at the door. Nauta asked whether I would like to join them going through the museum and I agreed. Thus began my first lesson in Dutch art. Nauta was from a cultured family, and one aunt was a well-known art critic. For Nauta, the Rijksmuseum, the Stadeljk, and the Mauritshuis and others were familiar places. We spent nearly the whole evening with the Dutch collection. I have never known a scientist more gracious and unassuming than Nauta. We remained friends until his death.

With success using Nauta’s method, I was ready to apply for funding and submitted two grants in 1961, “A Comparative Study of Tectothalamic Connections” and “Anatomical Studies of Brain Monoamine Neuron Systems.” Both were funded in 1962 and were continuously funded, with evolving research topics, for many years. The study of tectothalamic connections was largely devoted to analysis of auditory pathways. The first paper from this presented a new analysis of projections from the inferior colliculus to the thalamus, particularly the medial geniculate body in the cat (Moore and Goldberg, 1963). Jay Goldberg, my oldest friend, was a student of Dewey Neff and we had collaborated as students. Following his Ph.D., he did a postdoctoral fellowship with Clinton Woolsey and Jerzy Rose at the laboratory of Neurophysiology, University of Wisconsin. Rose and Woolsey had done extensive studies of thalamocortical connections and Jay had discussed this at length with them. We concluded from our study that the medial geniculate body had two divisions that received auditory projections, a pars principalis (MGp) and pars magnocellularis (MGm), and another that was really part of the pulvinar-posterior complex receiving no auditory input. The same organization was demonstrated in the monkey (Moore and Goldberg, 1966). We were concerned, however, about the shadow of Cajal. In the Histologie, Cajal described the fibers of the lateral lemniscus, the ascending pontine auditory pathway, bypassing the inferior colliculus and ascending directly to the medial geniculate. If true, this would render whatever projections came from the inferior colliculus as secondary. We set out to test Cajal’s conclusion. This required producing a very small lesion transecting the lateral lemniscus but leaving the immediately adjacent fibers of the spinothalamic tract intact. It soon became evident that this was not possible using stereotaxic surgery. As I have described earlier, I had had extensive experience performing manual microsurgery and I began making lateral lemniscus lesions under direct vision by removing dorsal cerebellum to expose the lateral brainstem and inserting a microknife into the lemniscus. With some practice we obtained several brains with restricted lesions, and a number of controls. The result was a very clear demonstration that all lateral lemniscus axons terminate in the inferior colliculus, and none ascend to the geniculate. Again, the same organization was shown in the monkey (Goldberg and Moore, 1967). Thus, the inferior colliculus is an obligatory pathway in the ascending brainstem auditory system. From our material it was quite clear that Cajal had mistaken the spinothalamic tract for the lateral lemniscus, one of his few errors. There were other studies on the auditory system but, as I shall relate later, we shifted to an area where functional correlations were more readily explored, the visual system. My laboratory was moved in 1964 to the Wyler Children’s Hospital, where additional space allowed more personnel and trainees.

Monoamines in the Brain

Part of my graduate work had been a study funded at first by the Wallace Company, developer of meprobamate (Miltown), a widely used tranquilizer. The mechanism of action was not known and Hunt thought it might act through sleep mechanisms. A new faculty member in the Department of Pharmacology, Alfred Heller, and another Hunt graduate student, John Harvey, and I began a study in which stereotaxic lesions were placed in various brain regions and, after recovery, a determination of sleeping time was made. Sleeping time was a standard method to quantify the effects of sedatives in which the experimental compound was injected intravenously, rats were placed on their backs, and the time until they first rolled over was measured. Our control was a short-acting barbiturate. We found a highly significant doubling of sleep time with both compounds with lesions ablating the septal area and the pontine tegmentum but not lateral hypothalamus (Harvey, J.A., Heller, A., Moore, R.Y., Hunt, H.F., and Roth, L.J. Effect of central nervous system lesions on barbiturate sleeping time in the rat.

J. Pharmacol. Exptl. Therap., 144:24–36, 1964). John Harvey and I had spent an enormous amount of time on this and, to this day, I do not understand the results. Meprobamate soon was found not to be very effective and was supplanted as a tranquilizer of choice by chlordiazepoxide (Librium). We published the barbiturate results and went on to other projects. The major one was an attempt to demonstrate that brain monoamines were associated with specific pathways. The catecholamines were discovered in the early 20th century, but their presence in brain was not established until the work of Marthe Vogt (1954; Vogt, M. The concentration of sympathin in different parts of the central nervous system under normal conditions and after the administration of drugs. J Physiol (Lond).1954; 123:451–481), and dopamine was not recognized as a separate transmitter until 1957. Serotonin was isolated and characterized in 1948 and shown in brain shortly thereafter. Early work on brain monoamines was hampered by the lack of efficient, reliable, and sensitive methods for assay.

In the mid-1950s, a spectrophotofluorometer was marketed and assay of all monoamines became routine (Udenfriend, S. Development of the spectrophotofluorometer and its commercialization. Protein Sci. 1995;4:542–551). Al Heller quickly understood the potential this had for study of brain monoamines and obtained one of the early instruments. During my postdoctoral fellowship, I had become proficient with stereotaxic surgery and we designed a study to test the hypothesis that monoamines in brain were associated with specific pathways. The fluorometric analyses at that time were only sensitive enough for either pooled regional concentration determinations or whole-brain levels. I had developed an interest in hypothalamus, particularly in the lateral hypothalamic syndrome. We had developed feeding techniques to obtain a high level of survival of these profoundly aphagic animals so that we could perform bilateral lesions in rats. As in the sleeping study, we placed other lesions in the septal area and lateral pontine isthmus region with cortical lesions as controls.

The first monoamine we were able to assay reliably was serotonin, and our first experiment had what, in our eyes, was a beautiful result. Lateral hypothalamic lesions produced decreases in whole-brain serotonin of about 50%, but the other lesions were not as effective (Harvey et al., 1963). In succeeding experiments, we showed that both serotonin and norepinephrine were affected and that all forebrain structures rostral to the lesion showed similar changes (Moore et al., 1965; Heller et al., 1966). I performed an experiment in which each of our lesion types were made in rats and the brains were prepared using the Nauta method. This showed degenerating axons in the vicinity of the lesions but none in the rest of the forebrain. My interpretation of this evidence was that the distant effects of our lesions were a consequence of transsynaptic changes, and I convinced my colleagues that this was correct. It was not. Subsequent work showed that the monoamine axons were very small and unmyelinated, below the resolution of the Nauta method. This was demonstrated almost immediately by the work of Swedish groups that developed the fluorescent histochemical, or Falck-Hillarp, method (Falck, B., Hillarp, N.-Å., Thieme, G., and Torp, A. Fluorescence of catechol amines and related compounds condensed with formaldehyde. J Histochem Cytochem. 1962;10:348–354). With this, small axons below the limits of light microscope resolution are visualized readily with fluorescence microscopy because of diffusion of the signal. The origin of the fluorescence histochemical method and its history has been discussed in a recent paper by Tomas Hökfelt (Hökfelt, T. Looking at neurotransmitters in the microscope. Prog Neurobiol. 2010;90:101–118). Bengt Falck visited the University of Chicago for a lecture in early 1963. As soon as he presented the method, its power to study brain monoamine systems was evident and, after the lecture, I inquired whether I might visit him to learn it. He was most interested and I spent 6 weeks in Lund in the fall of 1963. Falck and his family greeted me warmly and I spent the last 3 weeks as a guest in their house. We became fast friends and have remained so since. Over the next 10 years, I visited Lund frequently carrying out a collaborative research program that was quite productive. In 1971, I did a sabbatical in Lund. This began in May and continued through the fall. On prior trips I had begun working with Anders Björklund, who was then a student in the laboratory. Bengt was not devoted to neuroscience studies but encouraged Anders and others to develop that field.

Adventures in the Rhythm Trade

In the 1960s, I did a study of retinal projection in collaboration with Marcel Frankel, a resident in ophthalmology, who had learned the technique of making small lesions in the retina with a laser (Moore, R. Y., Karapas, F., and Frenkel, M. Lateral geniculate projection from discrete retinal lesions in the cat. Am. J. Ophthalmol.1966;62:918–925). Our study was done in cats with the Nauta method for staining degenerating axons, and it required me to learn the visual system in a detail I had not done previously. I found this fascinating and began to study the rest of the visual system in detail. As this proceeded, I began a collaboration with Julius Axelrod and Richard Wurtman to determine the central pathways of pineal control. This was not long after Axelrod had demonstrated the metabolic pathway for melatonin production, and Wurtman had come as a postdoctoral fellow to his laboratory with an interest in pineal function. My collaborator at Chicago, Al Heller, spoke with Axelrod at a FASEB meeting, and plans for a study between Chicago and the NIH were put in place. Axelrod’s suggestion was that we could identify central pathways involved in pineal regulation.

Service for the Neuroscience and Academic Communities

My first service beyond local activities in Chicago was as a member of the Maternal and Child Health Program Project Review Committee of the NICHD beginning in 1972. This was a broad committee and I was one of two neurologists serving. It introduced me to the review process and initiated my education in “committeeship.” The next year I was appointed to the Pediatric Subcommittee of the FDA Neuropharmacology Agents Advisory Committee. Our major charge was to review the use of antipsychotic drugs in children and provide a report. In 1976 I was appointed to the Psychobiology Study Section of the Division of Research Grants. This committee reviewed a very broad range of grants from standard brain–behavior studies to field studies of animal behavior. I remember one in which the major expense was the purchase of a Land Rover for a field study of primate behavior in Africa. Overlapping this, I served on a VA Career Development Committee that covered neurology, gastroenterology, and nephrology. I remember, with some feeling of chagrin, how confidently we reviewed applications that covered subjects that a substantial part of the committee had no real basis for critical judgment. It was a process of trusting your colleagues. The meetings were held at the VA Central Office on McPherson Square, and this location gave me my first experience with the elegance and institutional beauty of our capital. I have always enjoyed Washington,

D.C. When I first went to Bethesda for meetings, it had the feeling of a small town. There were two hotels, the In Town and the Bethesdan. Restaurants were few and limited in scope. The changes since those times are amazing.

In 1980, I was appointed to a National Academy of Sciences Panel that was to study the Health Related Issues of Marijuana Use. The committee was chaired by Arnold Relman, Editor of the New England Journal of Medicine, and had a very diverse membership. I was the member assigned to cover neurological issues. The committee worked for 2 years to prepare a report of which we were all proud. Part of the work was public hearings, which were interesting. The report made news for a short period and was, I think, quite influential in the long run. Following this, I served for 4 years on the NIMH Board of Scientific Counselors. This was followed by 4 years on the Board of Scientific Counselors of NINDS, 2 years as Chair with a subsequent 4 years, 1992–1996, as Chair of the NIMH Board of Scientific Counselors. Service on these boards was both a rewarding and frustrating experience. When I first started the work, the NIH was in its heyday. Funds were abundant as was transient staff such as fellows. NIH scientists are reviewed every 4 years. In my first tour of duty on the NIMH board, the reviews were perfunctory, no changes were made in response to recommendations, and it was a pro forma process. Then money became tighter and new intramural research directors were under more pressure to justify the allocation of funds. The essential problem was, and is, how to deal with a tenured scientist who gradually loses productivity and whose work has diminishing impact. In the academic world this is accomplished by increasing teaching or administration. No such opportunities exist at NIH. In addition, NIH scientists had been able in some circumstances to add other permanently appointed scientists. This resulted in some very large groups, particularly in clinical research. When these lost vitality, the problems were compounded. The NIH continues to struggle with this problem. I have served on a number of ad hoc panels and committees, advisory boards, and review boards. Among these was a 4-year appointment on the NASA National Space Biomedical Research Institute National Advisory Council. I have also served on 14 editorial boards, including a 25-year term of service on the Brain Research board. Although this has some rewards, done properly it requires a substantial commitment of time and intellectual energy.

Two experiences in industry have been informative. The first was as an advisor for the Institute de Recherches Internationales Servier. Servier is a French pharmaceutical company. The work was interesting, but the major benefit was many trips to Paris. On some occasions, they would call a meeting at short notice requiring me to travel on the Concorde. The second experience has been with the American company, Cephalon, Inc. I have consulted for the company from its founding in 1987 to the present. It went from the two founders in an office to an international company with annual sales exceeding $2 billion. The difference between academic science and drug development is considerable, and the latter is critical for translation of academic science. Both are valuable, and understanding industry is increasingly important for the academic scientist.

I will recount two other advisory experiences. The first is a 12-year service, 1996–2008, on the Board of Directors of the National Sleep Foundation, a small foundation dedicated to increasing public knowledge of the importance of sleep and sleep disorders. The requirements for a foundation differ from any of the other advisory roles I have played. First, the knowledge needs to be packaged and distributed effectively. For this a cooperative interaction between scientists and clinicians and media experts is needed. Second, to exist and function, the foundation needs to raise funds. The Board oversees these, and I have been impressed by the commitment of uncompensated board members to the foundation. The second is service on the President’s Committee on the National Medal of Science. I was appointed to the Presidential Commission by President George Bush in 2006 for a 3-year term, which was extended with a second term of 3 years in 2009. The National Medal of Science is given to eight scientists from all areas of science each year. Individuals are nominated and the nominations are reviewed by the committee that is comprised of 12 individuals. I am one of three biological scientists, and the only medical scientist on the committee. The challenge for us is selecting from the number of outstanding scientists nominated. The service on this committee is very gratifying, and we have the pleasure of attending the medal presentation by the President at the White House each year.

Serving on the Faculty of Several Institutions

I started on the faculty of the University of Chicago in 1959 and had every intention of finishing my career there. For me, my major appointment was in the Division of Neurology, even though I held appointments in Pediatrics and Anatomy. The Division prospered from 1966 through 1973 with increasing faculty and activity. The group worked together well and was very compatible. But, as happens with a young faculty, people were lured away by other institutions and one young woman tragically committed suicide after her fiancé died of an acute leukemia. As a Division, we were required to obtain approval for new appointments from the Chair of the Department of Medicine. There was, at that time, a new Chair who felt Neurology was not a major priority for that Department and refused to approve new appointments. As a consequence, the clinical load became overwhelming for those remaining and all, save the division head, left in 1973–1974. I received an offer from the University of California, San Diego, to join the Department of Neurosciences and agreed. We arrived in San Diego in July 1974. Our house was in La Jolla at the bottom of Mount Soledad and a half mile from the beach. The unvarying good weather was a real change from Chicago, and it took a couple of years to discern that the lack of seasons was a bit disconcerting. UCSD had a VA Hospital and what was called the “University Hospital.” Its previous incarnation had been as the San Diego County Hospital and this was how the public saw it. Consequently, the clinical load was rather light and much lighter than I experienced in Chicago. The advantage was increased lab time, and my years in San Diego were very productive. Another advantage was that recruiting students and postdocs to San Diego was much easier than to the south side of Chicago. I took up running for exercise and reached a level of running two marathons. About 2 years after we arrived, one of my sons was having some problems in school and I began investigating. He was using marijuana and not attending to school. In the course of reviewing his problem I found that the school curricula, both primary and secondary, did not have the rigor we had experienced at the University of Chicago Laboratory School. In addition, school funding in California was low then, as it is now. Finally, the level of cultural activity in San Diego was low; it was very much an “outdoor” society. With all of these issues, we decided to leave California in 1979. Two years before, I had been offered the Chair of Neurology at the University of Michigan but turned it down after long consideration. In 1979, I was interviewed, and subsequently offered the chair at the University of Wisconsin and the State University of New York at Stony Brook. Stony Brook presented an interesting challenge. The medical school was only 10 years old and had just completed building a new University Hospital. The Department of Neurology had not been formed and only two neurologists had been hired. There was new laboratory space and, thus, a founding chair would have responsibility for developing a clinical service, hiring a faculty, and developing research programs. It was too intriguing to pass up. We opened the hospital in 1980 with 10 psychiatric beds and gradually increased the census to about 300 beds. In all, I spent 12 years at Stony Brook. By the end of that time, the department had 15 faculty members, a busy practice, multiple research grants covering both clinical and basic topics, a residency training program that was recruiting excellent American graduates, and it ran a substantial surplus. The other interesting component of this start-up operation was to establish a practice plan for the clinical departments. I learned an immense amount about the business of medicine and became Vice President of the plan. Over the next 10 years it became a business with revenue much in excess of $100 million per year. But, by 1989, I felt the important challenges had been met, I was too deeply into administrative activities to actively run a laboratory, and it clearly was time to move on. I felt that it would be difficult to recruit a new chair with the old one looking over his or her shoulder, so I sought opportunities elsewhere.

I had served on an external advisory committee at the University of Pittsburgh for several years, and the Dean of the Medical School asked me what he could do to get me to come to Pittsburgh at each advisory committee visit. Early in 1990 he put the same question to me and I replied, “Give me something interesting to do.” I was made Professor of Neurology and Psychiatry and Director of the Center for Neuroscience. The Center was without walls and its major functions were to establish and administer a graduate program that would serve all neuroscience faculty independent of departmental affiliation and to promote interaction among neuroscientists. This was not burdensome and went quite well. It left ample time for research. In 1992, I was asked to be Director of the Alzheimer Disease Research Center funded by NIA. This was to be temporary and only until a competing renewal of the grant was prepared. After this was completed I was asked by the President of the University to head a group of University of Pittsburgh faculty to work with a Carnegie Mellon University group to prepare a grant proposal for the RK Mellon Foundation to establish a Center for the Neural Basis of Cognition that would be a joint function of the two universities. We successfully raised $12 million that allowed renovating space for the Center, the recruitment of new faculty, and establishing a cognitive neuroscience graduate program. All of these activities went well and the Center has been an enormous success. I resigned as Co-Director of the Center in 1996 when I agreed to become Chair of the Department of Neurology. The Department was in a crisis of leadership, and I was expected to get it on an even keel. Directing a clinical department is rarely an easy task, and it was not so on this occasion. At age 65 I was not interested in a long-term involvement and was able to withdraw in 2000.

In today’s clinical departments, particularly in the cognitive specialties, the three most urgent problems are money, money, and money. The chairs have become CFOs and the major attribute required for a clinical chair is financial probity. I took a sabbatical in 2000 in the MRC Cyclotron Unit, Hammersmith Hospital, London. In 1996 I had limited my clinical practice to movement disorders. The head of the MRC Unit, David Brooks, has done much of the important positron emission tomography (PET) work on Parkinson’s disease. It was a very productive 6 months and London is a magnificent city. We lived in a mews apartment next to Hyde Park in Knightsbridge, two blocks from Harrods. When I returned, I became interested in developing research in movement disorders at Pittsburgh. A patient had endowed a chair for me, the Love Family Professorship, and with his encouragement, and help from the family of another patient, Michael Zigmond and I were encouraged to approach a foundation, the Scaife Family Foundation, with a proposal to develop a multidisciplinary program in neurodegenerative disease. After a long courtship, the Foundation agreed to provide $10 million if it was matched. The University of Pittsburgh Medical Center graciously provided matching funds and the Pittsburgh Institute for Neurodegenerative Disease now exists in new laboratory space headed by a distinguished Parkinson’s disease investigator, J. Timothy Greenamyre. And I have been gratefully free of any administrative duties for more than 5 years. In 2009, I retired from clinical practice, feeling that 50 years of neurology would suffice. I shall retire at the end of September 2010, and we plan to move to the San Francisco area to be near children and grandchildren.

Family

I have commented on my family origins but not on our life together nor on my own experiences as a husband and father. My mother was not a nurturing person and, as I later deduced, was given to intermittent depressive episodes of varying severity. As she grew older, and my recollections are most accurate for the period of her 40s and beyond, she became increasingly unable to interact with people, largely being by herself. In her early 50s, my Grandfather Fisher died suddenly of a myocardial infarct. This affected her greatly and she developed a delusion that people on the street were talking about her and saying, “There’s the woman that killed her father.” Other delusions and deep depression followed, and she was hospitalized and received electroshock therapy. She never recovered to any approximation of normal function and by her early 60s she required custodial care in a nursing home. Despite this, she was basically a kindly person but never played an important role in my life beyond the age of about 10.

My father was almost a complete opposite. He was open, friendly, and naturally gregarious. We spent a good deal of time together. He was especially important during the period of onset of my panic disorder. During my last undergraduate year, I developed episodes of anxiety that evolved into a full panic disorder, a disorder not recognized at that time. Fortunately, I was largely engaged in independent study at school and could function some. My father provided understanding and support in a way hard to express. This continued throughout his active life. He was a major encouragement for me to pursue my objectives. After my mother was placed in a nursing home, he moved back to Georgia and purchased a small plot of land on the family farm from his sister and grew vegetables and fruit. That was the happiest I had ever seen him. His routine was to arise early and tend to the farm until about noon. After lunch he would begin “visiting,” going around the area talking to friends and strangers. In the late 1970s, it became apparent that he was cognitively impaired and my brother and I placed him in the nursing home where my mother resided.

Over the years his siblings all died, save a younger brother who lived in Atlanta. I kept in touch with him until he and his wife died about 10 years ago. They were childless and I lost contact with other Georgia relatives. It was heartbreaking to watch his descent into profound dementia. He died in 1992 not knowing who he was or where he was. My mother remained intellectually intact, albeit with her depression, until she had a basilar artery thrombosis in 1986. My brother had chronic ulcerative colitis from the age of 7 with multiple hospitalizations. Nevertheless, he functioned well as a purchasing agent, married and had two children. In mood and interests he was very much like my father. He had a colectomy in 1983 and did exceptionally well, having the most active and healthy period of his adult life. In 1986, he developed angina and was scheduled for a stress test. He died of cardiac arrest during it at age 48. His son continues to live in the Chicago area and we communicate occasionally. His daughter attended college but did not graduate. She took a clerical job but was prone to depression. She simply disappeared one day without any communication and has never been heard from again. His wife left the area and we have not been in contact.

I was married to Colston Nauman, a graduate student with Neff, in 1959. She is from an old family in Harrisburg, Pennsylvania. We have three children, Betsy born in 1961, Matthew in 1963, and Joshua in 1965. Colston had an acute psychosis in 1967 and moved to live by herself, leaving me with the challenge of three children. She became well enough in a few months to take them for a few hours to a day at a time and that continued until they went to high school. Each time I have moved, she has followed so that her relations with the children are quite good. She is independently wealthy, which facilitates things. I was able to hire a woman for child care who lived with us, and the children did better than I would have predicted. In 1969 I married a former graduate student, Jean Kavanagh, and we had one son, Thomas Moore, born in 1972. About 6 weeks after birth he was found to have the inherited metabolic defect, phenylketonuria. The dietary treatment for this was developed in the early 1960s and prognosis with dietary control was not known. Fortunately, Tom has done well and now works as a TV director in Los Angeles, but his early care and anxiety about his future put great strain on our marriage. The other children are also doing well. Betsy and Joshua both live in Silicon Valley and have good jobs in the information science business. Matthew lives in New York, works in interior design, largely for business, and has his own firm. He also teaches at the Fashion Institute of Technology. Only Tom is married. Jean left me in 1986, and I was married to an industrial toxicologist, Cynthia Driscoll in 1991. That did not work out either, and I am now married to Jane DeYoung. Jane was my departmental administrator in New York and we have been friends for 30 years. We were married in 1997 and have been splendidly happy since. We now live quietly in a Pittsburgh suburb, Fox Chapel, with our two Norwich terriers, Satchel and Sabrina.

Summation

I have long held that research university faculty are among the most privileged and pampered people in the world. They have few duties and almost unlimited time to study the scientific universe of their choosing. Tenure is obtained at a young age and their lives are secure. Compared to my father, who worked as a salesman in an environment of unease and uncertainty, I feel extremely fortunate. I have always looked forward to returning each day to my office and laboratory to indulge my curiosity. Teaching is one of the most pleasurable activities I know, both in the classroom and the laboratory. It is an exploration of knowledge with a group of intelligent, curious, and energetic people who ask only that you come prepared and present clearly. They enjoy it even more if you make it interesting. I have been able to travel the world through science. The most uncomfortable thing that happens in my academic life is a long, boring faculty meeting. Through my life I have had brief periods, such as on sabbatical, when I did not practice or teach neurology. It has always made me feel somewhat lost. There is, in my mind, no greater trust than that placed in a physician by a patient. One is asked to listen and understand. The process in neurology consists of taking and interpreting a history, the patient’s story of illness. A physical examination is performed to verify hypotheses reached from the history. This information is then used to make a localizing diagnosis: what part of the nervous system is malfunctioning? With this it is hopefully possible to reach a judgment about the etiology and pathophysiology of the problem. Further information from the laboratory or imaging may be required. The final step is therapy and assessment of its efficacy. The process requires communication between patient and physician and, particularly, understanding and empathy from the physician.

Selected Bibliography

Abrahamson, E.A., and Moore, R.Y. Lesions of suprachiasmatic nucleus efferents selectively affect rest-activity rhythm. Mol. Cell. Endocrinol., 252:46–56, 2006.

Abrahamson, E.A., and Moore, R.Y. The posterior hypothalamic area: Chemoarchitecture and afferent connections. Brain Res., 889:1–22, 2001.

Abrahamson, E.A., Leak, R.K., and Moore, R.Y. Suprachiasmatic nucleus projections to posterior hypothalamic arousal areas. NeuroReport, 12: 435–440, 2001.

Abrahamson, E.E., and Moore, R.Y. Suprachiasmatic nucleus inthe mouse: Retinal innervation, intrinsic organization and efferent projections. Brain Res. 916: 172–191, 2001.

Aguilar-Roblero, R., Morin, L.P., and Moore, R.Y. Morphological correlates of circadian rhythm restoration induced by transplantation of the suprachiasmatic nucleus in hamsters. Exper. Neurol., 130:250–260, 1994.

Aguilar-Roblero, R., Shibata, S., Speh, J.C., Drucker-Colin, R., and Moore, R.Y. Morphological and functional development of the suprachiasmatic nucleus in transplanted fetal hypothalamus. Brain Res., 580:288–296, 1992.

Axelrod, J., Snyder, S.H., Heller, A., and Moore, R.Y. Light-induced changes in pineal hydroxyindole-0-methyltransferase: Abolition by hypothalamic lesions. Science, 154:898–899, 1966.

Bjorklund, A., Moore, R.Y., Nobin, A., and Stenevi, U. The organization of tuberohypophyseal and reticulo-infundibular catecholamine neuron systems in the rat brain. Brain Res., 51:171–191, 1973.

Bohnen, N.I., Constantine, G.M., Mathis, C.A., and Studenski, S.A., and Moore, R.Y. Selective hyposmia and nigrostriatal dopaminergic denervation inParkinson’s disease. J Neurol., 254:84–90 2007.

Bohnen, N.I., Gedela, S., Herath, P., Constantine, G.M., and Moore, R.Y. Selective hyposmia in Parkinson disease: Association with hippocampal dopamine activity. Neurosci. Lett., 447:12–16, 2008.

Bohnen, N.I., Gedela, S., Kuwabara, H., Constantine, G.M., Mathis, C.A., Studenski, S.A., and Moore, R.Y. Selective hyposmia and nigrostriatal dopaminergicdenervation in Parkinson’s disease. J. Neurol., 254:84–90, 2007.

Bohnen, N.I., Kaufer, D.I., Hendrickson, R., Constantine, G.M., Mathis, C.A., and Moore, R.Y. Cortical cholinergic denervation is associated with depressive symptoms in Parkinson’s disease and parkinsonian dementia. J Neurol. Neurosurg. Psychiat., 78:641–643, 2007.

Bohnen, N.I., Kuwabara, H., Constantine, G.M., Mathis, C.A., and Moore, R.Y. Grooved Pegboard test as a biomarker of nigrostriatal denervation in Parkinson’s Disease. Neurosci. Lett., 424:185–189, 2007.

Bohnen, N.I., Studenski, S.A., Constantine, G.M., and Moore, R.Y. Diagnostic performance of clinical motor and non-motor tests of Parkinson disease: a matched case-control study. Eur. J. Neurol., 15:685–691, 2008.

Buysse, D.J., Nofzinger, E.A., Germain, A., Meltzer, C.C., Wood, A., Ombao, H., Kupfer, D.J., and Moore, R.Y. Regional brain glucose metabolism during morning and evening wakefulness in humans. Sleep, 27:1245–1254, 2004.

Card, J.P., and Moore, R.Y. Neuropeptide Y localization in the rat suprachiasmatic nucleus and periventricular hypothalamus. Neurosci. Lett., 88:241–246, 1988.

Card, J.P., and Moore, R.Y. Organization of lateral geniculate-hypothalamic connections in the rat. J. Comp. Neurol., 284:135–147, 1989.

Card, J.P., and Moore, R.Y. The suprachiasmatic nucleus of the golden hamster: Immunohistochemical analysis of cell and fiber distribution. Neurosci., 13: 415–431, 1984.

Card, J.P., and Moore, R.Y. Ventral lateral geniculate nucleus efferents to the rat suprachiasmatic nucleus exhibit avian pancreatic polypeptide-like immunoreactivity. J. Comp. Neurol., 206:390–396, 1982.

Card, J.P., Brecha, N., and Moore, R.Y. Immunohistochemical localization of avian pancreatic polypeptide-like immunoreactivity in the rat hypothalamus. J. Comp. Neurol., 217:123–136, 1983.

Card, J.P., Brecha, N., Karten, H.J., and Moore, R.Y. Immunocytochemical localization of vasoactive intestinal polypeptide-containing cells and processes in the suprachiasmatic nucleus of the rat: Light and electron microscopic analysis. J. Neurosci., 11:1289–1303, 1981.

Card, J.P., Enquist, L.W., and Moore, R.Y. Neuroinvasiveness of pseudorabies virus injected intracerebrally is dependent on viral concentration and terminal field density. J. Comp. Neurol., 407:438–452, 1999.

Card, J.P., Riley, J.N., and Moore, R.Y. The motor trigeminal nucleus of the rat: Analysis of neuronal structure and the synaptic organization of noradrenergic afferents. J. Comp. Neurol., 250:462–468, 1986.

Cassels, D.E., and Moore, R.Y. Sympathetic innervation of the ductus arteriosus in relation to patency. Chest, 63:727–731, 1973.

Cassone, V.M, Roberts, M.H., and Moore, R.Y. Melatonin inhibits metabolic activity in the rat suprachiasmatic nuclei. Neurosci. Lett., 81:29–34, 1987.

Cassone, V.M., and Moore, R.Y. Retinohypothalamic projection and suprachiasmatic nucleus of the house sparrow, Passer domesticus. J. Comp. Neurol., 266: 171–182, 1987.

Cassone, V.M., Speh, J.C., Card., J.P., and Moore, R.Y. Comparative anatomy of the mammalian hypothalamic suprachiasmatic nucleus. J. Biol. Rhythms, 3:71–91, 1988.

Eichler, V.B., and Moore, R.Y. The primary and accessory optic systems in the golden hamster Mesocricetus auratus. Acta Anat., 89:359–371, 1974.

Fallon, J.H., and Moore, R.Y. Catecholamine innervation of the basal forebrain. III. Olfactory bulb, anterior olfactory nuclei, olfactory tubercle and piriform cortex. J. Comp. Neurol., 180:533–544, 1978.

Fallon, J.H., and Moore, R.Y. Catecholamine innervation of the basal forebrain. IV. Topography of the dopamine projection to the basal forebrain and neostriatum. J. Comp. Neurol., 180:545–579, 1978.

Fallon, J.H., and Moore, R.Y. Superior colliculus efferents to the hypothalamus. Neurosci. Lett., 14:265–270, 1979.

Fallon, J.H., Koziell, D.A., and Moore, R.Y. Catecholamine innervation of the basal forebrain. II. Amygdala, suprarhinal cortex and entorhinal cortex. J. Comp. Neurol., 180:509–531, 1978.

Fallon, J.H., Riley, J.N., and Moore, R.Y. Substantia nigra dopamine neurons: Separate populations project to neostriatum and allocortex. Neurosci. Lett., 7:157–162, 1978.

Fallon, J.H., Riley, J.N., Sipe, J.C., and Moore, R.Y. The islands of Calleja: Organization and connections. J. Comp. Neurol., 181:375–396, 1978.

Fuchs, J.L., and Moore, R.Y. Development of circadian rhythmicity and light responsiveness in the rat suprachiasmatic nucleus: A study using the 2-deoxy[1–14C] glucose method. Proc. Nat. Acad. Sci. USA, 77:1204–1208, 1980.

Gall, C.M., and Moore, R.Y. Distribution of enkephalin, substance P, tyrosine hydroxylase, and 5-hydroxytryptamine immunoreactivity in the septal region of the rat. J. Comp. Neurol., 225:212–227, 1984.

Gao, B., and Moore, R.Y. Glutamic acid decarboxylase message isoforms in human suprachiasmatic nucleus. J. Biol. Rhythms, 11:172–179, 1996.

Gao, B., and Moore, R.Y. The sexually dimorphic nucleus of the hypothalamus contains GABA neurons in rat and man. Brain Res., 742:163–171, 1996.

Gao, B., Fritschy, J-M., and Moore, R.Y. GABA-A-receptor subunit composition in the circadian timing system. Brain Res., 700:142–156, 1995.

Gustafson, E.L., and Moore, R.Y. Noradrenaline neuron plasticity in developing rat brain: Effects of neonatal 6-hydroxydopamine demonstrated by dopamine–B–hydroxylase immunocytochemistry. Dev. Brain Res., 37:143–155, 1987.

Harvey, J.A., Heller, A., and Moore, R.Y. The effect of unilateral and bilateral medial forebrain bundle lesions on brain serotonin. J. Pharmacol. Exp. Therap., 140:103–110, 1963.

Harvey, J.A., Heller, A., Moore, R.Y., Hunt, H.F., and Roth, L.J. Effect of central nervous system lesions on barbiturate sleeping time in the rat. J. Pharmacol. Exp. Therap., 144:24–36, 1964.

Heller, A., and Moore, R.Y. Effect of central nervous system lesions on brain monoamines in the rat. J. Pharmacol. Exptl. Therapeutics, 150:1–9, 1965.

Heller, A., Harvey, J.A., and Moore, R.Y. A demonstration of a fall in brain serotonin following central nervous system lesions in the rat. Biochem. Pharmacol., 11:859–866, 1962.

Heller, A., Seiden, L.S., and Moore, R.Y. Regional effects of lateral hypothalamic lesions on brain norepinephrine in the cat. Intl. J. Neuropharmacol., 5:91–102, 1966.

Heller, A., Seiden, L.S., Porcher, W., and Moore, R.Y. 5-Hydroxytryptophan decarboxylase in rat brain: Effect of hypothalamic lesions. Science, 147:887 888, 1965.

Heller, A., Seiden, L.S., Porcher, W., and Moore, R.Y. Regional effects of lateral hypothalamic lesions on 5-hydroxytryptophan decarboxylase in the cat brain. J. Neurochem., 13:967–974, 1966.

Hemmendinger, L.M., and Moore, R.Y. Synaptic reorganization in the motor trigeminal nucleus of the rat following neonatal 6-hydroxydopamine treatment. J. Comp. Neurol., 250:462–468, 1986.

Johnson, R.F., Moore, R.Y., and Morin, L.P. Loss of entrainment and anatomical plasticity after lesions of the hamster retinohypothalamic tract. Brain Res., 460:297–313, 1988.

Johnson, R.F., Morin, L.P., and Moore, R.Y. Retinohypothalamic projections in the hamster and rat demonstrated using cholera toxin. Brain Res., 462:301–312, 1988.

Jones, B.E., and Moore, R.Y. Ascending projections of the locus coeruleus in the rat. II. Autoradiographic study. Brain Res., 127:23–53, 1977.

Jones, B.E., and Moore, R.Y. Catecholamine-containing neurons of the nucleus locus coeruleus in the cat. J. Comp. Neurol., 157:43–51, 1974.

Jones, B.E., Halaris, A.E., McIlhany, M., and Moore, R.Y. Ascending projections of the locus coeruleus in the rat. I. Axonal transport in central noradrenaline neurons. Brain Res., 127:1–21, 1977.

Kafka, M.S., Marangos, P.J., and Moore, R.Y. Suprachiasmatic nucleus ablation abolishes circadian rhythms in rat brain neurotransmitter receptors. Brain Res., 327:344–347, 1985.

Klein, D.C., and Moore, R.Y. Pineal N-acetyltransferase and hydroxyindole-0-methyltransferase: Control by the retinohypothalamic tract and the suprachiasmatic nucleus. Brian Res., 174:245–262, 1979.

Klein, D.C., Moore, R.Y., and Reppert, S.M. (Eds.) The Suprachiasmatic Nucleus– The Mind’s Clock, Oxford Press, New York, 1991.

Klein, D.C., Weller, J.L., and Moore, R.Y. Melatonin metabolism: Neural regulation of pineal serotonin: Acetyl coenzyme A N-acetyltransferase activity. Proc. Nat. Acad. Sci. USA, 68:3107–3110, 1971.

Kromer, L.F., and Moore, R.Y. A study of the organization of the locus coeruleus projections to the lateral geniculate nuclei in the albino rat. Neurosci., 5: 255–271, 1980.

Kromer, L.F., and Moore, R.Y. Norepinephrine innervation of the cochlear nuclei by locus coeruleus neurons in the rat. Anat. Embryol., 158:227–244, 1980.

Leak, R.H., and Moore, R.Y. Identification of retinal ganglion cells projecting to the lateral hypothalamic area of the rat. Brain Res., 770:105–114, 1997.

Leak, R.K., and Moore, R.Y. Suprachiasmatic nucleus projections in the rat: Retrograde analysis. J. Comp. Neurol., 433: 312–334, 2001.

Leak, R.K., Card, J.P., and Moore, R.Y. suprachiasmatic pacemaker organization analyzed by viral transynaptic transport. Brain Res., 819:23–27, 1999.

Levitt, P., and Moore, R.Y. Noradrenaline neuron innervation of the neocortex in the rat. Brain Res., 139:219–231, 1978.

Levitt, P., Moore, R.Y., and Garber, B.B. Selective cell association of catecholamine neurons in brain aggregates in vitro. Brain Res., 111:311–320, 1976.

Levitt, P.R., and Moore, R.Y. Development of the noradrenergic innervation of neocortex. Brain Res., 162:243–259, 1979.

Levitt, P.R., and Moore, R.Y. Developmental organization of raphe serotonin neuron groups in the rat. Anat. Embryol., 154:241–251, 1978.

Levitt, P.R., and Moore, R.Y. Organization of brainstem noradrenaline hyperinnervation following neonatal 6-hydroxydopamine treatment in rat. Anat. Embryol., 158:133–150, 1980.

Levitt, P.R., and Moore, R.Y. Origin and organization of brainstem catecholamine innervation in the rat. J. Comp. Neurol., 186:505–528, 1979.

Lindvall, O., Bjorklund, A., Moore, R.Y., and Stenevi, U. Mesencephalic dopamine neurons projecting to neocortex. Brain Res., 81:325–331, 1974.

Loy, R., and Moore, R.Y. Anomalous innervation of the hippocampal formation by peripheral sympathetic axons following mechanical injury. Exptl. Neurol., 57:645–650, 1977.

Loy, R., and Moore, R.Y. Ontogeny of the noradrenergic innervation of the rat hippocampal formation. Anat. Embryol., 157:243–253, 1979.

Loy, R., Koziell, D.A., Lindsey, J.D., and Moore, R.Y. Noradrenergic innervation of the adult rat hippocampal formation. J. Comp. Neurol., 189:699–710, 1980.

Loy, R., Milner, T., and Moore, R.Y. Sprouting of sympathetic axons in the hippocampal formation: Conditions necessary to elicit ingrowth. Exptl. Neurol., 67:399–411, 1980.

Moga, M.M., and Moore, R.Y. Organization of neural inputs to the suprachiasmatic nucleus in the rat. J. Comp. Neurol., 389: 508–534, 1997.

Moga, M.M., and Moore, R.Y. Paraventricular thalamus lesions after circadian period and activity distribution in the blinded rat. J. Bio. Rhythm Res., 31:212–219, 2000.

Moga, M.M., and Moore, R.Y. Putative excitatory amino acid projections to the suprachiasmatic nucleus in the rat. Brain Res., 743:171–177, 1996.

Moga, M.M., Weis, R.P. and Moore, R.Y. Efferent projections of the paraventricular thalamic nucleus in the rat. J. Comp. Neurol., 359:221–238, 1995

Moore, R.Y. Catecholamine innervation of the basal forebrain. I. The septal area. J. Comp. Neurol., 177:665–683, 1978.

Moore, R.Y. Effects of some rhinencephalic lesions on retention of conditioned avoidance behavior in cats. J. Comp. Physiol Psychol., 57:65–71, 1964.

Moore, R.Y. Entrainment pathways and the functional organization of the circadian system. Prog. Brain Res., 111:103–119, 1996.

Moore, R.Y. Indolamine metabolism in the intact and denervated pineal, pineal stalk and habenula. Neuroendocrinol., 19:323–330, 1975.

Moore, R.Y. Neural control of the pineal gland. Behav. Brain Res., 73:125–130, 1996

Moore, R.Y. Organization of midbrain dopamine systems and the pathophysiology of Parkinson disease. Parkinsonism Relat. Disord., 9: S65–S71, 2003.

Moore, R.Y. Organization of the primate circadian system. J. Biol. Rhythms, 8:S3–S9, 1993. [Database]

Moore, R.Y. Organum vasculosum lamina terminalis: Innervation by serotonin neurons of the midbrain raphe. Neurosci. Lett., 5:297–302, 1977.

Moore, R.Y. Pineal transplants to the anterior chamber of the eye: Evidence for functional reinnervation. Exptl. Neurol., 49:617–621, 1975.

Moore, R.Y. Retinohypothalamic projection in mammals: A comparative study. Brain Res., 49:403–409, 1973.

Moore, R.Y. Suprachiasmatic nucleus in sleep-wake regulation. Sleep Med., 8: Suppl 3:27–33, 2007.

Moore, R.Y. Suprachiasmatic nucleus, secondary synchronizing stimuli and the central neural control of circadian rhythms. Brain Res., 183:13–28, 1980.

Moore, R.Y. The geniculohypothalamic tract in monkey and man. Brain Res., 486:190–194, 1989.

Moore, R.Y. The organization of the human circadian timing system. Prog. Brain Res., 93:101–117, 1992.

Moore, R.Y., Abrahamson, E.A., and van den Pol, A.N. The hypocretin neuron system: An arousal system in the human brain. Ital. Arch. Biol., 139:195–206, 2001.

Moore, R.Y., and Bernstein, M.E. Synaptogenesis in the rat suprachiasmatic nucleus demonstrated by electron microscopy and synapsin I immunoreactivity. J. Neurosci., 9:2151–2162, 1989.

Moore, R.Y., and Bloom, F.E. Central catecholamine neuron systems: Anatomy and physiology of the dopamine systems. Ann. Rev. Neurosci., 1:129–169, 1978.

Moore, R.Y., and Bloom, F.E. Central catecholamine neuron systems: Anatomy and physiology of the norepinephrine and epinephrine systems. Ann. Rev. Neurosci., 2:113–168, 1979.

Moore, R.Y., and Card, J.P. The intergeniculate leaflet: An anatomically and functionally distinct subdivision of the lateral geniculate complex. J. Comp. Neurol., 344:403–430, 1994.

Moore, R.Y., and Danchenko, R.L. Paraventricular–subparaventricular hypothalamic lesions affect circadian function. Chronobiol. Intl., 19:345–360, 2002.

Moore, R.Y., and Eichler, V.B. Loss of a circadian adrenal corticosterone rhythm following suprachiasmatic lesions in the rat. Brain Res., 42:201–206, 1972.

Moore, R.Y., and Goldberg, J.M. Ascending projections of the inferior colliculus in the cat. J. Comp. Neurol., 121:109–136, 1963.

Moore, R.Y., and Goldberg, J.M. Projections of the inferior colliculus in the monkey. Exptl. Neurol., 4:429–438, 1966.

Moore, R.Y., and Gustafson, E.L. The distribution of dopamine-B-hydroxylase, neuropeptide Y and galanin in locus coeruleus neurons. J. Chem. Neuroanat., 2:95–106, 1989.

Moore, R.Y., and Halaris, A.E. Hippocampal innervation by serotonin neurons of the midbrain raphe in the rat. J. Comp. Neurol., 164:171–184, 1975.

Moore, R.Y., and Klein, D.C. Visual pathways and the central neural control of a circadian rhythm in pineal serotonin N-acetyltransferase activity. Brain Res., 71:17–33, 1974.

Moore, R.Y., and Leak, R.K. The suprachiasmatic nucleus. In Takahashi, J.S., Turek, F.W., Takahashi, J.S., and Moore, R.Y. (Eds.) Circadian Clocks, PlenumPress, New York, pp. 141–179, 2001.

Moore, R.Y., and Lenn, N.J. A retinohypothalamic projection in the rat. J. Comp. Neurol., 146:1–14, 1972.

Moore, R.Y., and Rapport, R.L. Pineal and gonadal function in the rat following cervical sympathectomy. Neuroendocrinol., 7:361–374, 1971.

Moore, R.Y., and Sibony, P. Enkephalin-like immunoreactivity in neurons in the human pineal gland. Brain Res., 457:395–398, 1988.

Moore, R.Y., and Silver, R. Suprachiasmatic nucleus organization. Chronobiol. Intl., 15:475–487, 1998.

Moore, R.Y., and Smith, R.A. Postnatal development of a norepinephrine response to light in the rat pineal and salivary glands. Neuropharmacol., 10:315–323, 1971.

Moore, R.Y., and Speh, J.C. A putative retinohypothalamic projection containing substance P in the human. Brain Res., 659:249–253, 1994.

Moore, R.Y., and Speh, J.C. GABA is the principal neurotransmitter in the mammalian circadian system. Neurosci. Lett. 150:112–116, 1993.

Moore, R.Y., Bhatnagar, R.K., and Heller, A. Anatomical and chemical studies of a nigro-neostriatal projection in the cat. Brain Res., 30:119–135, 1971.

Moore, R.Y., Bhatnagar, R.K., and Heller, A. Norepinephrine and DOPA decarboxylase in rat brain following hypothalamic lesions. Intl. J. Neuropharmacol., 5: 287–291, 1966.

Moore, R.Y., Bjorklund, A., and Stenevi, U. Plastic changes in the adrenergic innervation of the rat septal area in response to denervation. Brain Res., 33:13–35, 1971.

Moore, R.Y., Gustafson, E.L., and Card, J. P. Identical immunoreactivity of afferents to the rat suprachiasmatic nucleus with antisera against avian pancreatic polypeptide, molluscan cardioexcitatory peptide and neuropeptide Y. Cell Tiss. Res., 236:41–46, 1984.

Moore, R.Y., Halaris, A.E., and Jones, B.E. Serotonin neurons of the midbrain raphe: Ascending projections. J. Comp. Neurol., 180:417–438, 1978.

Moore, R.Y., Heller, A., Bhatnagar, R. K., Wurtman, R.J., and Axelrod, J. Central control of the pineal gland: Visual pathways. Arch. Neurol., 18:208–218, 1968.

Moore, R.Y., Heller, A., Wurtman, R.J., and Axelrod, J. Visual pathway mediating pineal response to environmental light. Science, 155:220–223, 1967.

Moore, R.Y., Karapas, F., and Frenkel, M. Lateral geniculate projection from discrete retinal lesions in the cat. Am. J. Ophthalmol., 62:918–925, 1966.

Moore, R.Y., Speh, J.C. and Card, J.P. The retinohypothalamic tract originates from a distinct subset of retinal ganglion cells. J. Comp. Neurol., 352:351–366, 1995

Moore, R.Y., Speh, J.C. Serotonin innervation of the primate suprachiasmaticnucleus. Brain Res. 1010:169–173, 2004.

Moore, R.Y., Speh, J.C., and Leak, R.K. Suprachiasmatic nucleus organization. Cell Tiss. Res., 309:89–98, 2002.

Moore, R.Y., Weis, R., and Moga, M.M. Efferent projections of the intergeniculate leaflet and the ventral lateral geniculate nucleus in the rat. J. Comp. Neurol., 420:398–418, 2000.

Moore, R.Y., Whone, A.L., and Brooks, D.J. Extrastriatal monoamine neuron functionin Parkinson’s disease: An 18F-dopa PET study. Neurobiol. Dis., 29: 381–390, 2008.

Moore, R.Y., Whone, A.L., McGowan, S., and Brooks, D.J. Monoamine neuroninnervation of the normal human brain: An 18F-DOPA PET study. Brain Res., 982:137–45, 2003.

Moore, R.Y., Wong, S.L.R., and Heller, A. Regional effects of hypothalamic lesions on brain serotonin. Arch. Neurol., 13:346–354, 1965.

Moore, R.Y., Ziegler, B., and Bayer, S.A. Monoamine neuron innervation of the hippocampal formation: Alteration by neonatal irradiation. Exptl. Neurol., 60: 318–326, 1978.

Morin, L.P., Blanchard, J., and Moore, R.Y. Intergeniculate leaflet and suprachiasmatic nucleus organization and connections in the hamster. Visual Neurosci., 8:219–230, 1992.

Morin, L.P., Goodless-Sanchez, N., Smale, L., and Moore, R.Y. Projections of the suprachiasmatic nuclei and subparaventricular zone and retrochiasmatic area in the golden hamster. Neurosci., 61:391–410, 1994.

Mosko, S., and Moore, R.Y. Neonatal suprachiasmatic nucleus ablation: Absence of functional and morphological plasticity. Proc. Nat. Acad. Sci. USA, 75: 6243–6246, 1978.

Mosko, S.S., and Moore, R.Y. Neonatal ablation of the suprachiasmatic nucleus: Effects on the development of the pituitary-gonadal axis in the female rat. Neuroendocrinol., 29:350–361, 1979.

Mosko, S.S., and Moore, R.Y. Neonatal suprachiasmatic nucleus lesions: Effects on the development of circadian rhythms in the rat. Brain Res., 164:17–38, 1979.

Mosko, S.S., and Moore, R.Y. Retinohypothalamic tract development: Alteration by suprachiasmatic lesions in the neonatal rat. Brain Res., 164:1–15, 1979.

Mosko, S.S., Erickson, G.F., and Moore, R.Y. Dampened circadian rhythms in reproductively senescent female rats. Behav. Neural Biol., 28:1–14, 1980.

Nofzinger E.A., Nichols T.E, Seltzer C.C., Price, J., Steppe D.A., Miewald J.M., Kupfer D.J., and Moore, R.Y. Changes in forebrain function from waking to REM sleep in depression: preliminary analysis of (18F)DG PET studies. Psychiatry Res., 31:59–78, 1999.

Nofzinger, E.A., Buysse, D.J., Miewald, J.M., Meltzer, C.C., Price, J.C., Sembrat, R.C., Ombao, H., Reynolds, C.F., Monk, T.H., Hall, M., Kupfer, D.J., and Moore, R.Y.Human regional cerebral glucose metabolism during NREM sleep in relation to waking. Brain, 125:1105–1115, 2002.

Nofzinger, E.A., Mintun, M.A., Price, J., Meltzer, C.C., Townsend, D., Buysse, D.J., Reynolds III, C.F., Dachille, MJ., Matzzie, J., Kupfer, D.J., and Moore, R.Y. A method for the assessment of the functional neuroanatomy of human sleep using FDG PET. Brain Res. Protocols, 2:191–198, 1998.

Nofzinger, E.A., Mintun, M.A., Wiseman, M.B., Kupfer, D.J., and Moore, R.Y. Forebrain activation in REM sleep: An FDG PET study. Brain Res., 770: 192–201, 1997.

Reuss, S., and Moore, R.Y. Neuropeptide Y-containing neurons in the rat superior cervical ganglion: Projections to the pineal gland. J. Pineal Res., 6:307–316, 1989.

Richter, R.B., and Moore, R.Y. Non-invasive central nervous system disease associated with lymphoid tumors. Johns Hopkins School of Medicine Journal, 122:271–283, 1968.

Riley, J.N., Card, J.P., and Moore, R.Y. A retinal projection to the lateral hypothalamus in the rat. Cell Tiss. Res., 214:257–269, 1981.

Roberts, M.H., and Moore, R.Y. Localization of neuropeptides in efferent terminals of the eye in the marine snail, Bulla gouldiana. Cell Tiss. Res., 248:67–73, 1987.

Roberts, M.H., Bernstein, M.E., and Moore, R.Y. Differentiation of the suprachiasmatic nucleus in fetal rat anterior hypothalamic transplants in oculo. Dev. Brain Res., 32:59–66, 1987.

Shibata, S., and Moore, R.Y. Development of a fetal circadian rhythm after disruption of the maternal circadian system. Dev. Brain Res., 41:313–317, 1988.

Shibata, S., and Moore, R.Y. Development of neuronal activity in the rat suprachiasmatic nucleus. Dev. Brain Res., 34:311–315, 1987.

Shibata, S., and Moore, R.Y. Electrical and metabolic activity of suprachiasmatic nucleus neurons in hamster hypothalamic slices. Brain Res., 438:374–378, 1988.

Shibata, S., and Moore, R.Y. Neuropeptide Y and optic chiasm stimulation affect suprachiasmatic nucleus circadian function in vitro. Brain Res., 615:95–100, 1993.

Shibata, S., and Moore, R.Y. Neuropeptide Y and Vasopressin effects on suprachiasmatic nucleus neurons in vitro. J. Biol. Rhythms, 3:265–276, 1988.

Shibata, S., Cassone, V.M., and Moore, R.Y. Effects of Melatonin on neuronal activity in the rat suprachiasmatic nucleus. Neurosci. Lett., 97:140–145, 1989.

Shibata, S., Newman, G.C., and Moore, R.Y. Effects of calcium ions on glucose utilization in the rat suprachiasmatic nucleus in vitro. Brain Res. 426:332–338, 1987.

Shirakawa, T., and Moore, R.Y. Glutamate shifts the phase of the circadian neuronal timing rhythm in the rat suprachiasmatic nucleus in vitro. Neurosci. Lett., 178:47–50, 1994.

Smale, L., Cassone, V.M., Moore, R.Y., and Morin, L.P. Paraventricular nucleus projections mediating pineal Melatonin and gonadal responses to photoperiod in the hamster. Brain Res. Bull., 22:263–269, 1989.

Speh, J.C., and Moore, R.Y. Retinohypothalamic tract development in the hamster and rat. Dev. Brain Res., 76:171–181, 1993.

Squire, L.R., and Moore, R.Y. Dorsal thalamic lesion in a noted case of human memory dysfunction. Ann. Neurol., 6:503–506, 1979.

Steeves, T.D.L., King, D.P., Zhao, Y., Sangoram, A.M., Du, F., Bowcock, A.M., Moore, R.Y., and Takahashi, J.S. Molecular cloning and characterization of the human CLOCK gene: Expression in the suprachiasmatic nuclei. Genomics, 57:189–200, 1999.

Stenevi, U., Bjorklund, A., and Moore, R.Y. Growth of intact adrenergic axons in the denervated lateral geniculate body. Exptl. Neurol., 35:290–299, 1972.

Stenevi, U., Bjorklund, A., and Moore, R.Y. Morphological plasticity of central adrenergic neurons. Brain Beh. Evol., 8:110–134, 1973.

Tarlov, E.C., and Moore, R.Y. The tecto-thalamic connections in the brain of the rabbit. J. Comp. Neurol., 126:403–421, 1966.

Thannickal T.C., Moore, R.Y., Nienhuis, R., Ramanathan, L., Gulyani, S., Aldrich, M., Cornford, M., and Siegel, J.M. Reduced number of hypocretin neurons in human narcolepsy. Neuron, 27:469–474, 2000.

Thannickal, T.C., Siegel, J.M., Nienhuis, R., and Moore, R.Y. Pattern of hypocretin (orexin) soma and axon loss, and gliosis, in human narcolepsy. Brain Pathol. 13:340–51, 2003.

Thomas, G.J., Moore, R.Y., Harvey, J.A., and Hunt, H.F. Relations between the behavioral syndrome produced by lesions in the septal region of the forebrain and maze learning in the rat. J. Comp. Physiol. Psychol., 52:527–532, 1959.

Watkins, W.B., Yen, S.S.C., and Moore, R.Y. Presence of b-endorphin-like immunoreactivity in the anterior pituitary gland of rat and man and evidence for the differential localization with ACTH. Cell Tiss. Res., 215:577–589, 1981.

Whone A.L., Moore R.Y., Piccini P.P., and Brooks D.J. Plasticity of the nigropallidal pathway in Parkinson’s disease. Ann. Neurol. 53:206–13, 2003.

Wilkes, M.M., Kobayashi, R.M., Yen, S.S.C., and Moore, R.Y. Monoamine neuron regulation of LRF neurons innervating the Organum vasculosum laminae terminalis and median eminence. Neurosci. Lett., 13:41–46, 1979.

Michael I. Posner

BORN:

Cincinnati, Ohio

September 12, 1936

EDUCATION:

University of Washington, B.S. (1957)

University of Washington, M.S. (1959)

University of Michigan, Ph.D. (1962)

APPOINTMENTS:

Assistant Professor of Psychology, University of Wisconsin (1962–1965)

Associate Professor of Psychology, University of Oregon (1965–1968)

Professor of Psychology, University of Oregon (1968–EMERITUS 2000–present)

Professor of Neuropsychology and Psychology, Department of Neurology Neurosurgery, Washington University, St. Louis (1985–1989)

Director, Institute of Cognitive and Decision Sciences, University of Oregon (1989–1995)

Head, Department of Psychology, University of Oregon (1995–1998)

Professor of Psychology in Psychiatry, Weill Medical College of Cornell University, New York Founding Director, Sackler Institute (1998–2002)

Adjunct Professor, Weill Medical College (2002)

HONORS AND AWARDS (SELECTED):

Paul M. Fitts Award, Human Factors Society (for training in Human Factors, 1967); Ersted Award for distinguished teaching, University of Oregon (1975); John Simon Guggenheim Fellow (1979–1980)

A.P.A. Distinguished Scientific Contribution Award (1980)

National Academy of Sciences, U.S.A. (1981)

American Academy of Arts and Sciences (1986)

Howard Crosby Warren Medal, Society of Experimental Psychologists (1988)

Howard Vollum Award for exceptional achievement of a member of the scientific and technical community of the Pacific Northwest (1989)

Scientist of the Year Award, Oregon Academy of Sciences (1995)

Charles A. Dana Award for pioneering research in medicine (neuroscience) (1997)

Honorary Doctoral Degrees: Universities of Padova (1998), Granada (1999), Nottingham (2002),

Paris (2002), Brussels (2007), Ben Gurion (2007), Michigan (2009), and Buenos Aires (2010)

Karl Lashley Award, American Philosophical Society (joint with M. E. Raichle) (1998)

Pasarow Foundation Award in Medical Research (Neuropsychiatry) with M. E. Raichle (2000)

First Grawemeyer Award for Psychology with M. E. Raichle and S. E. Petersen (2001)

Fyssen Foundation International Prize for Studies of Human Consciousness (2004)

Patricia Goldman Rakic Award NARSAD (with M. E. Raichle) (2004)

First Mattie Dogan Prize in Psychology (2008)

National Medal of Science (2008)

Michael I. Posner’s early work involved the measurement of mental operations by use of reaction time and other chronometric measures. In 1979 he began studies of patients to link mental operations to brain areas in the study of attention. To test hypotheses arising from this work, he developed with Marcus Raichle studies imaging the human brain during cognitive tasks. He has worked on the anatomy, circuitry, development, and genetics of three attentional networks underlying maintaining alertness, orienting to sensory events, and voluntary control of thoughts and ideas. His methods for measuring these networks have been applied to a wide range of neurological, psychiatric, and developmental disorders and to normal development and school performance. At the time of this volume his research involves a longitudinal study of children prior to school designed to understand the interaction of specific experience and genes in shaping attention and self-regulation and studies of methods for training attention networks and changing the brain state in ways that might also alter attention.

Michael I. Posner

A Life in Psychology

I was fortunate to be around during extraordinary times for the study of psychology. Neuroimaging made the human brain, which is obviously central to understanding the mind and behavior, available for scientific analysis. This biography tries to trace some of the background for my involvement in these events. I believe that a better understanding of the human mind requires both measurement of mental events and mapping of those events to brain networks. It has been my goal over many years to contribute to that effort.

Personal Story

I was born late in the Great Depression on September 12, 1936, in Cincinnati, Ohio, but at two months of age I travelled with my family to San Bernardino, California. My father had a successful law practice in Cincinnati, but for health reasons he undertook the move to California. Because California had no reciprocity in law degrees and because of the difficult economic times during the depression years he never again practiced law. During the war years he first worked in defense-related industry, including Cal Ship and later social work with Jewish servicemen and their families. My mother was most often home with us in these years, but she also was a very fine shoe salesperson, a calling she pursued mostly on weekends.

The most influential people in my early development were my father, whose extraordinary dedication to helping others was always a powerful example in my life, and my brother Jerry, whose guidance has continued over my whole career. He was a brilliant student who decided to become a physician at age 2, received his M.D. in his early 20s and became a very renowned neurologist and founder of the Department of Neuro-Oncology at Memorial Sloan Kettering Cancer Center in New York. After my graduation in physics he suggested graduate work in biological science, which eventually led to my choice of psychology

In 1979 I went to New York and learned from Jerry Posner about how to study neurological patients. In my 3 years in the Neurology and Neurosurgery Departments in St. Louis at the start of cognitive imaging, being Jerry’s brother helped to overcome my connection to psychology and cognition, both regarded with suspicion in that department. My role as a mystic in St. Louis is described somewhat in the section on the neural basis of mental operations. Jerry’s reputation also aided me during my 3 years in Psychiatry at Weill Medical College, which is described in the section on attention.

Measuring Mental Operations

In 1963 I was a young Assistant Professor at the University of Wisconsin in Madison. I had been appointed in 1962 and set up a small laboratory in the old Journalism building, which was just behind 600 N. Park where Psychology was located. I thought it important to do something in this laboratory. It was the department of Harry Harlow, David A. Grant, and Wilf Brogden. They were important in psychology and thought that anyone in their department should be as well. It was not the easiest department to join!

Inspired by Broadbent’s 1958 book, I planned to study attention. I had set out to study the time to switch attention from one modality to another. This was the era before computers, so in the experiment I used a gift from my mother-in-law of a Wallensak tape deck together with a new display device consisting of small photos of the digits 1–9 and another with upper- and lowercase letters. When a light was switched on, the digit or letter was projected so that it could be seen on the front screen. This in-line display was switched from a beep on one channel of the recorder. In this way I could expose the subject to an auditory stimulus (e.g., letter or digit) and a visual digit or letter. The subject’s task was to say whether the two successive items were the same or different. My goal was first to determine how much longer it took to deal with matching cross-modal events than events in the same modality. Then to determine the switching time I planned to delay the second item until the difference went away and the length of the delay needed would be a measure of the switching time needed.

If you were to have read my papers that appeared a few years later based on these findings, you would never have guessed the purpose of my study. In the course of the studies I found out something quite different and, from my perspective, more important. It does take longer to match an auditory digit following a visual one than to match two identical auditory or two identical visual digits, just as I had predicted. However, when the task was changed from matching the identical digits to one of determining whether digits were odd or even, the time for switching went away. It no longer took time to switch between modalities. Instead I found that whenever the two items were not physically identical there was an increased time. If, for example, I had the subjects indicate whether two letters had the same name and the pair were upper- and lowercase (e.g., Aa versus AA or aa), I found the same 80 millisecond increase that occurred for matching a visual and auditory A. Why was Aa longer than AA? From my perspective steeped in the learning theory of the 1960s, this was a genuine puzzle. We have spent a lifetime learning that Aa were the same letter, and even longer learning that a visual and auditory 3 were both the same digit. If our mental processes were based on learned associations as it said in all my learning textbooks, why were physically identical items at such an advantage?

Perhaps matching a capital and small letter was longer than pairs with the same name because the identical letter pairs were identical in two ways. They both had the same name and they were the same shape. If this were true, I reasoned that pairs like AB, which were different in both form and name, would take the same time irrespective of whether the instruction were to match based on physical identity or on name. However, I found in another experiment that it took 80 milliseconds longer to match AB when the matching instruction was based on physical identity (i.e., are the two letters exactly identical?) than when it was based on name (i.e., do the two letters have the same name?). Since AB were always just as similar, I thought this meant that some internal process involved in determining whether a nonidentical pair has the same name had to be performed before one could decide AB did not require a yes to the name match instruction. I was measuring a covert mental process that delayed making the no response to letter pairs like AB. I loved this idea.

Of course I knew that 100 years ago the great Dutch physiologist Donders had first measured the time for the covert mental processes of recognition and choice by using the subtractive method. I also knew that the subtractive method has been criticized by a number of psychologists as requiring that all processes remained the same except the one being measured, but since the instruction changed from one experiment to another there was no way to be sure this was true. In fact, the leading historian of psychology, Boring, had dismissed Donders’ method as useless, in his history of psychology that all students of my generation had been required to read. However, in my study the 80 millisecond difference between AA and Aa could be obtained in exactly the same experiment with the same instruction. Thus, I reasoned it was not as subject to the criticism made of Donders. At the time I could not have guessed that 30 years later I would still be debating this issue with a generation of neuroscientists who had never been exposed either to Donders or Boring, but were using subtraction in neuroimaging experiments.

My paper describing these findings appeared in the Psychological Review in 1967. By then I had left Madison, Wisconsin, to take up a position at the University of Oregon in Eugene, which was to be my lifetime home. In my work I felt that the covert mental process that I had trapped might be a good empirical method for measuring the kinds of internal computations that were discussed in a new book by Miller, Galanter, and Pribam that took the ideas of Herbert Simon and applied them to the questions of experimental psychology. At Oregon there were already a number of psychologists closely related to the topics on which I was working. Fred Attneave had written a great book on how information theory might relate to psychology, and Ray Hyman was one of the discoverers of the law that related the time taken to perform a task to the amount of information contained in the task. The trips to Oregon were full of discussion about how to shape the new information processing psychology that was emerging from many laboratories.

Setting up a new laboratory is always difficult. In Eugene it was more of a problem because the Psychology department had almost no space. It had a small animal laboratory in which Jim McGaugh had done many learning studies. Jim left the year I came and in fact I was his replacement and was to teach courses in learning which he had formerly taught. Dan Kimble, who was already part of the faculty, was conducting research on the hippocampus. Fred Attneave had a small room in Condon Hall where psychology offices were located, and Ray Hyman had space in Susan Campbell a few buildings away, but there was no substantial laboratory for human studies. Indeed in human work most of the effort was on the development of theory, and experiments played a smaller role. We were given a house on the far end of campus, which had been a fourplex. I had start-up funds of $3500 to equip a laboratory. In these days where some new faculty receive up to half a million dollars, that might seem a bit small, even corrected for inflation. I traveled with Dick Littman (then department head) to Salem, where the state warehouse had furniture, much of it made in the prison, which was sold cheaply to qualified state agencies. I remember that in addition to new visual displays I also bought a Stowe memory drum, a tachistoscope, and slide projector. Within a few years this laboratory was to house four faculty, a dozen students, and more than $100,000 worth of computer equipment, but that was all in the future.

The paper on letter matching, written with graduate student Ron Mitchell, was published in 1967. I felt that we had made a very considerable contribution in showing how to improve the old subtractive method. However, a much greater contribution to this problem was to come from another source the very next year. In appreciation of the 100th anniversary of Donders’ paper, the new group called Attention and Performance, which had been started by Andries Sanders in the summer of 1966, held a meeting in Eindhoven, the Netherlands. On the last day of that meeting Saul Sternberg presented his paper on the additive factors method for studying how to infer serial stages from reaction times. Everyone at the meeting knew immediately that this was truly a great contribution. It showed how Donders’ insights could be extended to any serial task by examining additivity and interactions between independent variables thought to influence the same or different internal stages. My own reaction was somewhat mixed. I knew this was a great contribution to the field of psychology. I also knew it would eclipse whatever my own studies based on the more limited matching method had produced. While there was clearly a bit of jealousy for what Sternberg had achieved, a feeling I was to have many times over the years, I was also happy that at last we had a strong, if limited, method to explore the internal workings of the mind.

What exactly were the mental operations involved in matching an upper- and lowercase A? I first imagined that the person determined whether the two letters were identical in physical form and, if the answer was no, then tested whether they had the same name. This would be a strictly serial model. I rejected this idea because matching at the physical level would take time and, if all the physical matching stimuli were left out so that subjects would have to name all name pairs, no reduction in RT resulted. It seemed like the two processes took place in parallel. If so, the ending times for each process had to be variable because we could extend the time for physical matches by making the color different between two matching letters and not influence the name-level matches. Having other letter names in memory increased the time for the name match but not the physical match. We seemed to have two relatively independent and parallel processes.

In 1967 when these experiments were being carried out, Richard Atkinson and Richard Shiffrin published a joint paper on memory for letters and other materials. In this very famous model there was an encoding process that converted the visual letters to a verbal code that was stored. There was no idea that the physical form of the letter could also be stored. It was a strictly serial model of the type that was then common in psychology and in physiology. Additive factors in psychology built upon the serial processing ideas that were the basis of digital computers at that time, and this appeared to fit with the kind of hierarchy of simple, complex, and hypercomplex cells that had been found in the visual system by Hubel and Wiesel. Parallel models were thought of as too complex and as violations of the scientific strictures for simplicity. The massively parallel systems at the basis of connectionism were 15 years in the future.

Steve Keele and I thought we could study the possibility of parallel coding in memory if we simply put in one letter and then delayed the time before the second letter was presented. We found that at least for several seconds after the first letter disappeared, the trace of the physical form of the first letter must have been present because physical matches were still faster than name matches. Moreover, we could extend the life of the physical form by making name matches more difficult, so that even when we measured no advantage in the standard experiment that did not mean that the physical form was no longer stored. We published the first of these results in a paper in Science, which I believe was the first evidence against the serial coding model in memory.

Steve and I realized that we could test the imagery ability of subjects by making the first letter auditory and seeing how they might respond to upper- and lowercase matches. When instructed to code an auditory stimulus as an uppercase A, a delay of .5 sec was sufficient for the match to be identical to the time for matching against a physically presented uppercase A. Moreover, when this occurred the time for a lowercase A was the same length as for letters not presented on that trial. Based on our letter match results, Barbara Tversky taught subjects names to correspond with simple line drawings of face-like stimuli with varying numbers of features in common. Later, Miriam Klein (now Rogers) varied the physical similarity or the similarity of the names. The findings suggested that when given the name of a face name, subjects could retrieve the physical face in about .5 of a second. At that time most subjects claimed to have a visual image. However, earlier when most people denied having an image, the match still depended upon the number of visual features in common. I distinguished between a visual code in memory, which clearly influenced the time to match stimuli, and a visual image that was available to consciousness.

At the time we published a monograph illustrating the dual nature of codes and the ability to maintain a visual code in memory and to create an image in .5 second (Posner, Boies, Eichelman, & Taylor, 1968) it was still thought that visual images were somewhat mystical. How could something as subjective as a visual image be measured and thus meet the criterion of behaviorism for objective evidence? I believed then that our evidence putting auditory letters into concrete visual form provided such evidence. However, a year or two after our paper, Roger Shepard published a series of papers showing that one could create a visual representation of a letter and rotate it at will to any angle. Even more beautiful was the finding that, once having created an image at a particular angle, one could match a rotated letter faster than even an upright one. A lifetime of learning to deal with upright letters was less important for matching than a created representation at the instructed angle. This was beautiful evidence for imagery and it was to be shortly supplemented and massively documented by the studies of Steve Kosslyn showing in detail the properties of visual images. Moreover, these important findings set the stage for the results Kosslyn was to obtain with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) showing how even primary visual cortex could be influenced by images.

I must admit a kind of quiet pride at all of these results on imagery. I think it is one of the great cumulative success stories of psychology in the current era. At times I felt a bit upset when a student would ask me whether I knew about the discoveries on images of Shepard or Kosslyn, but I realize that one needs to remember the very best evidence that was obtained on a topic, which is not necessarily the same as the first evidence. Even when I lecture on imagery I refer mainly to mental rotation or to Kosslyn’s many demonstrations. I still feel that the distinction between code and image is important for psychology, even more these days when neuroimaging studies show late activation within sensory areas in tasks where no conscious image occurs.

Exemplars and Prototypes

At the time of my dissertation studies, information theory was at the height of its popularity in psychology. It had been very successful in summarizing how the amount of information transmitted by a stimulus could provide a prediction of the time required to respond. This finding suggested that human mental activity could be measured in terms of channel capacity or the bits per second that could be transmitted by the system. It thus extended the subtractive method by allowing one to deal with the probability of a stimulus and error along with the number of stimuli by a single measure that could be correlated with reaction time. At last Psychology had a law: reaction time was proportional to information transmitted (Hick-Hyman law).

My dissertation adviser, Paul Fitts, used information theory to extend the law to movement. When the extent and accuracy of a movement was related to the amount of information that the movement conveyed, one could predict the time to move to the target quite accurately (Fitts law). The two laws together, and knowledge of a person’s speed, could allow one to predict when a person would leave and reach a wide variety of targets. These findings were the centerpiece of the book, Human Performance, I was to finish for Fitts after his very untimely death.

It was difficult to describe the pleasure of being able to have two laws based upon the same underlying theory. More than just the new laws, information theory provided a critique for pure behaviorism. It was not just reinforced practice that influenced speed of processing. Instead what might have occurred but did not, that is, the alphabet of possible stimuli, was also important for prediction. This suggested that some intrinsic structure limits the human capacity to process information. It was our goal to understand these limits, and this was the basis for my strong concentration on attention.

As soon as one left the experimental tasks that Fitts had used, there were clearly problems. Consider adding two numbers together. Here was a mental operation that did not preserve the information in the stimulus, but of course it required time to calculate the response. Mental arithmetic was clearly more difficult than merely reporting each number. Overall it seemed to me more difficult to combine and reduce information than to transmit it. I designed a series of simple tasks that showed, under the conditions I had created, a certain amount of truth to the hypothesis that information reduction was a measure of thought, but the generality was too limited to be really useful and part way through my dissertation I realized that the goal of finding a new law was not to be realized.

Nonetheless, I persisted and was very delighted that my committee members, whom I greatly admired, were willing to let me pursue things. They must have known it would not succeed, but they never really conveyed their doubts. After working with numerous students myself, I know that sometimes it does pay to withhold criticisms and see what develops.

In an effort to extend my measurement of information reduction to the study of perception, I created stimuli of nine dots and applied various rules that distorted the dots and produced new patterns that were either close to the original or very dissimilar. The distortions could be summarized by the amount of information change needed to produce them. Using the then popular methods of standard psychophysics, I could show that my information measure of distortions fit well with subjective ratings by people. Not surprisingly, when two patterns were heavily distorted it was very hard to classify them as members of the same category than if they were similar. That this finding could be summarized in terms of information reduction allowed my experiments to be seen as related by a single hypothesis.

The most enduring finding from the dot pattern work was based on studies that I conducted with Steve Keele after coming to Oregon. In my thesis I had taught people to call two very different patterns by the same name. We could easily extend this to study a type of concept or pattern learning. At the time of this research, studies of concept formation were dominated within psychology by an extremely rational approach based on ideas developed earlier by Aristotle and Mill. For example, Jerome Bruner had shown that Harvard undergraduates could reason about series of nonsense patterns consisting of conjunctions or disjunctions of distinct attributes. With appropriate feedback concerning whether or not the pattern reflected the concept, they were able to abstract an understanding of the rule that had been chosen. Clearly this work showed some of the reasoning capabilities of selected undergraduates, but concepts could be learned nearly automatically by young children, animals, and undergraduates, probably less reflective and more poorly trained than the Harvard students that Bruner had studied.

With only a vague understanding of the questions we were asking, Keele and I designed studies in which subjects learned to give a single name to four patterns highly distorted from a single prototype pattern in the manner used in my dissertation. When people memorized four such patterns, they showed the behavior of having a concept in that they gave a common response to what appeared to be very different looking events. However, we were pleased that they could do more than this. When we showed them the prototype which they had never before seen, they named it without difficulty and in recognition memory experiments they often said that they had actually seen it before.

I was very excited by these results. It seemed at the time that I had a new experimental demonstration not only of learning of schemas but of an automatic way of abstracting the essence from clues that would be as remote as would actually be found in the real world. This after all is what philosophers Berkeley and Mill had argued were abstract ideas derived from sensory input but capturing only what was most essential. Critics could and did argue that this was merely a kind of complex generalization process in which the prototype was not stored but simply recognized from storage of all of the exemplars. Indeed this criticism was made to my submission of a somewhat overheated paper, which we titled “On the Genesis of Abstract Ideas.”

To my delight, and despite many criticisms, the paper was accepted by the editor to the Journal of Experimental Psychology, David Grant, who was thought to be as tough a critic as they come. He even accepted the title, which most of the referees wanted me to cut, with the comment this shows “we can trip the light fantastic.”

This is not the end of the story. Thanks to the brilliance of Eleanor Rosch, my efforts ended up as a small part of what was certainly one of the intellectual triumphs of psychology during the late 20th century. Rosch first attempted to understand how color names were derived. The importance of this question derived from the general issue of whether names were really quite arbitrary or whether they depended critically upon the perceptual process. Benjamin Lee Whorf had argued that our perception or worldview was critically dependent upon the language we spoke; and how we perceived color had been made by Brown and others a central topic in testing whether perception depended on naming or not. Rosch was a student of Brown, and she conducted anthropological work with the Dani people, who apparently had only two color names (light and dark). She showed that they were better at learning to name colors that were excellent examples of our English color names (e.g., a clear, highly saturated red) than those close to the boundary. These results supported the idea that color names were not arbitrary but arose out of perceptual experience. Later, two Berkeley anthropologists built on this finding to show simple rules out of which perception led to naming that seemed to be general across cultures. In the era of cognitive neuroscience the dominance of biology for many of our cultural derivations (e.g.,language) is not a surprise, but it was the first of the many important observations that Rosch made. Rosch argued for prototypical colors as the basis of classification and cited my studies, although, in fact, her work in no way really depended upon them. Nonetheless, I was delighted to have a role.

Rosch was to make even more important findings for the field of psychology. After all, not all trees and still less all games look alike, yet we have no trouble in forming these concepts. Rosch distinguished between basic concepts in which the exemplars looked similar (e.g., trees) and superordinate concepts (e.g., games) in which they did not. She found that with basic concepts there was an automatic extraction of the concept, and in studies that were built upon matching experiments she proved that the time to classify clear instances of a concept was really based on their distance from the prototype. After priming with the name animal, it was easier to match two good instances of animals (e.g., cow) than two instances equally familiar but which were not as close to the prototype (fish). Moreover, Rosch was able to write clearly that these studies were really violations of the overly rational idea of concept that had come into psychology via Bruner. Indeed, later writings on the issue often argued that Rosch had overturned ideas of concepts that had begun with Aristotle and had shown instead how concepts were fuzzy or graded ideas based on simple derivations from our perceptual experience.

I thought at the time, and I still do, that Rosch’s work represents an enduring and fundamental contribution to psychology for which she is due every credit that the field has. I came to see them as related to an observation made by Herbert Simon based on his concept of bounded rationality. We can, of course, learn to reason, but the thought processes reveal the concrete nature of how we do reason, whether in images or in concepts. Cognitive neuroscience has tended to confirm these ideas by showing how intimately frontal systems, highly abstracted from sensory input, are related to posterior systems such as the fusiform face area which are close to the perceptual input. Indeed, when dog and bird experts who were able to differentiate many different species were tested, they tended to activate the fusiform face areas just as nonexperts would do for human faces.

The work of Rosch has formed an important link between general social science and models of brain function. In my view one of the most important developments in the study of the higher mental processes has been based upon the importance of concrete analogical thinking in human reasoning. In a brilliant series of empirical and philosophical works, the linguist George Lakoff and the philosopher Mark Johnson have built upon the thinking of Rosch to argue that metaphors play a central role in how we think about movement, love, and politics. They argue that much of our knowledge is based upon what they call embodied reasoning. Again a clear reference to the kind of bounded rationality and concrete thought that was implied by Simon. However, in their hands we can see how so much of our thinking about the real world is governed by common and idiosyncratic metaphors. How the knowledge of the Munich agreement, ceding parts of Czechoslovakia to Germany, influenced the response to Vietnam and how our thinking about how the body moves influences how we regard covert shifts of attention.

While Rosch clearly made a major contribution toward how to conceive of human thought processes, my original dot patterns were employed in studies of human memory. During the 1970s and 1980s there were continual attacks on the idea of prototypes being abstracted from diverse inputs. Many researchers developed models in which, by storing each individual exemplar, it was possible to simulate the data obtained in my original memory experiments by methods that relied on simple stimulus generalization just as the referees of the original paper had suggested. I began to get the feeling that I was like the punch drunk fighter who had to be beaten up by each new model before it could be proposed for an important championship fight. The most creative and sustained of these models (Minerva) was developed by my friend and colleague Doug Hintzman. Minerva proposed a creative way to store exemplars and use them in creating an echo that provided a basis for recognition of new instances. Thus, our data could be simulated even though there was never any storage of prototypes. Minerva was a great step forward in memory models and was really not very inconsistent with our way of thinking about prototypes. Because Minerva stored the results of the echo, and even though any given calculation was based on exemplars, once the calculation was made the prototype became a new exemplar and was now stored. The Minerva form of memory storage was sufficient to allow prototypes to stand for concepts and to play the role in metaphorical thinking that has been discovered.

Probably our work on prototypes would have died off with no resolution of the disputes except that Knowlton and Squire showed that patients whose memory had been impaired by brain lesions were at a great disadvantage in remembering exemplars but dealt very well with the prototype. These studies suggested that extraction of the prototype might not involve the medial temporal brain area found important for explicit storage. One way of examining this issue is to compare conditions when people are asked to explicitly recall an item with situations in which they can make use of the material but do not explicitly have to remember it. This task lent itself to fMRI studies, and they showed that implicit use of the primed word seemed to involve a portion of the right posterior cortex. In order to determine whether this activation represented an early priming by the stored information, I conducted a high-density electroencephalography (EEG) study with Rajendra Badigaiyan. We found that right posterior electrodes consistent with the fMRI activation differed between primed and unprimed words in the implicit condition during the first 150 milliseconds after input. These data suggested that right posterior activation of information was contacted automatically and rapidly after the input cue. On the other hand, activations in the explicit condition were mostly in hippocampal and frontal areas.

Another feature of the brain circuits related to expertise (including faces, word forms, and artificial and natural categories) is that in addition to the posterior area of activation they also involve frontal areas. In the case of visual words, for example, frontal areas including the left ventral frontal area and the anterior cingulate are active within 150 milliseconds after input, almost as fast as some of the posterior areas. In general, the frontal and posterior areas work together over a long time interval to integrate diverse information related to the problem solution. In the case of generating the use of a noun, which takes about 1100 milliseconds, the frontal areas are in communication with posterior areas related to semantics at 450 milliseconds. In general, brain studies have argued that there is close communication between frontal, posterior, and subcortical areas in generating the solution to problems. These findings provide a more objective basis for the role that concrete codes stored in visual and auditory areas may play in cognition.

Neural Basis of Mental Operations

Starting in 1978, I began to use a cue in an otherwise empty visual field as a way of moving attention to a target. We monitored eye movements and since only one response was required there was no way to prepare the response differently depending upon the cue. The results seemed to me to be very spectacular. We found that a covert shift of attention induced by a cue, presented as little as 100 milliseconds before a target, could enhance the speed of responding to target onset. We had trapped a covert attention shift and observed its movement. In fact, in one study response times to probes at intermediate locations were enhanced at intermediate times as though attention actually moved through the space. Whether attention moves through the intermediate space is still a disputed matter, suggesting the limitation of a purely behavioral study. At the time, it was also hard to conceive how a movement of attention could possibly be executed by neurons. Subsequently, Georgopoulos and colleagues showed that the population vector of a set of neurons in the motor system of a monkey could carry out what would appear, behaviorally, as a mental rotation. After that finding, a covert shift of attention did not seem too far-fetched.

About this time I became aware of a number of papers by Vernon Mountcastle and by Bob Wurtz using cellular recording to study the properties of cells in the posterior parietal lobe of the monkey. These papers suggested the possibility of attention cells in the parietal cortex that might be critically involved in orienting attention toward visual events. A Tuesday night meeting of our research group was assigned to read these papers. I asked whether our reaction time measures were the results of such attention cells. I thought, if the covert shifts of attention in humans could be connected with the monkey work, it might contribute to linking cognitive psychology to brain mechanisms. I don’t think there was much enthusiasm for this idea at the time. After all, cognition was about software and what did it have to do with the parts of the brain in which cells were found in the monkey?

In 1979 I met Oscar Marin, an outstanding behavioral neurologist. He was about to move to Portland, Oregon, to set up a clinical and research effort at Good Samaritan Hospital, and he invited me to set up a neuropsychology laboratory in conjunction with the hospital. It was a perfect time for me because I had spent 6 months of 1979 in New York working with Michael Gazzaniga, whose career in psychology is probably familiar to most readers, and my brother Jerry, who helped me test patients with parietal lesions. I pursued these questions in the new laboratory in Portland. In the end I commuted to Portland once a week for 7 years. It was such a pleasure to work with Dr. Marin that the long drive was worthwhile.

The results seemed to me to be a revelation. Patients with different lesion locations in the parietal lobe, the pulvinar, and the colliculus all tended to show neglect of the side of space opposite the lesion, but in a detailed cognitive analysis it was clear that they differed in showing deficits in specific mental operations of disengaging, moving, and engaging attention. As I saw it at the time, we had found a new form of brain localization. Different brain areas executed individual mental operations or computations such as disengaging from the current focus of attention (parietal lobe), moving or changing the index of attention (colliculus), and engaging the subsequent target (pulvinar). No wonder Lashley thought the whole brain was involved in mental tasks. It was not the whole brain, but a widely dispersed network of quite localized neural areas. Even looking back from the perspective of 20 years, I can again feel the excitement I had surrounding this idea at the time.

I read an article in Scientific American indicating changes in cerebral blood flow in the brain when reading silently. In cognitive psychology, reading had been studied quite a lot and we knew something about the orthographic, phonological, and semantic operations that must have taken place while reading, but they would be combined in the overall blood flow. Even more compelling for the possible anatomy of mental operations was a paper appearing in 1985 by Per Roland indicating that different parts of the brain were active during way finding, mental arithmetic, and verbal tasks. However, even in this paper there was no effort to uncover the specific operations that might be performed by the brain areas involved.

About this time Washington University School of Medicine started a national search for a psychologist who might work in conjunction with the developing PET center led by Marc Raichle. It might be surprising to people how reluctant psychologists were to take a chance on brain imaging. For me this was the opportunity to test the idea that arose from the neurological studies that individual mental operations would be localized in separate brain tissue. James S. McDonnell had wanted to develop an Institute that would study extrasensory perception, but the powers that be at Washington University were not going to do that. Instead, they agreed to a Center for Higher Brain Function. A psychologist who studied brain function was about as mystical as they wanted to go, and Marc Raichle and his colleagues at Washington University recognized the importance of being able to use PET to illuminate questions of higher mental function.

I had gone to St. Louis in the hopes of pursuing work on attention. When I talked to neurologists about covert shifts of attention (without eye movements) and then proposed to break the invisible shift into component operations like disengaging and moving, I saw eyes glaze and interest wane. Language studies have the advantage that the operations were more concrete and that neurosurgeons valued knowledge about the localization of language areas to aid them in avoiding such areas during surgery. Our language studies, summarized in my book with Marc Raichle, had an important influence on the field, fostering many studies of language and other cognitive processes. The development of fMRI allowed studies that were less invasive and more precise, and they have generally confirmed and greatly extended our language studies and shown that in many other areas of cognition a network of widely scattered brain areas become active, which when orchestrated together allow us to carry out a variety of tasks.

The St. Louis studies did quite a lot for the development of neuroimaging and, in the main, supported the idea that widely scattered brain areas were involved when any task was studied. Some people have thought that these areas were specific for domains of function like language or face stimuli, and so on. I have maintained the importance of mental operations, without denying that domain specificity may also play a role in understanding localization. In the area of face processing, for example, there has been a lot of dispute over whether there is a specific face area because experts in other domains activate the same area when thinking about their domain of expertise. However, if one thinks about localization of mental operations, it seems clear that faces and other objects, where we come to recognize the individual people or objections via their distinctive features, share operations in common. A similar argument can be applied to the visual word form area.

Attention is one of the areas that has been widely studied by fMRI. Maurizio Corbetta came to St. Louis after I had left and he, together with Gordon Shulman, have provided strong evidence for localization of quite separate mental operations within two areas of the parietal lobe that form a portion of a larger network whose functions are to align attention with the target. Although my initial speculation of which operations occurred in which areas was not entirely correct, the beautiful localized brain areas support the overall localization hypothesis.

Development of Attention

When I returned to Eugene from St. Louis in 1989, it was with the goal of forwarding research in two directions. It was my conviction that the findings we made in St. Louis on processing visual and auditory words would lead to evidence for many networks of brain areas involved in mental activity. While I did not dream that the work would grow to the magnitude that actually took place, following the use of fMRI, the general shape of what has happened seemed clear right from the start. I also realized that the skills needed to improve localization and understand the anatomy of cognition were far removed from what I could do best. Instead I concentrated on measuring the operation of these networks in real time.

Even before leaving St. Louis, I teamed with Avi Snyder and Marc Raichle to carry out studies of the time course of processing visual words and nonsense material using the 16-channel EEG system available there. However, in Eugene, Don Tucker was developing a new way of taking EEG from the skull, which would allow many electrodes to be put into place at once. Together we set up a laboratory in Straub Hall and began to compare his 32-channel EGI system with a 32-channel electro-cap using the Grass amplifiers from older studies. The results convinced me that there was no great loss from the relatively high impedances used in the EGI system. We were able to see scalp signatures of brain areas corresponding to the major generators found in the previous PET and later fMRI language studies. In my work with Yalchin Abdullaev and Bruce McCandliss, among others, it was exciting to see activity in the visual word form area, anterior cingulate and frontal and temporo-parietal cortex in real time, as the network computed different aspects of the language tasks we used. More recently, real-time fMRI allows some of this work to be done using that method, but because of the speed of mental processes and the importance of brain rhythms in connecting neural areas, EEG remains an important contributing method.

The study of attention has been a central topic from the start of human experimental psychology. However, many who write about attention seem to view it as a slightly mystical issue not amenable to scientific definition. They prefer to think of it as an emerging property, usually of sensory or motor systems and not an organ system with its own anatomy, evolutionary history, and function. In 1972, I began work on attention by dividing the overall system into components. It was not until 1990 when, due largely to the development of neuroimaging in humans and cellular recording in nonhuman primates, it became possible to outline the neural networks that underlie these functions.

In our work, we laid out networks of brain areas related to obtaining the alert state, orienting to sensory stimuli, and executive control involve in resolving conflict between other brain networks. I have written extensively about the anatomy, circuitry, neuromodulators, and genes related to common properties and individual differences in network efficiency. As a result I have come to regard attention as an organ system consisting of separate networks carrying out its various functions. Attention networks are of special importance because attention is involved in many functions, including our ability to control our behavior in the face of conflicting external and internal demands. During the late 1990s, as the result of a donation by the Mortimer Sackler family, I had the unique opportunity to set up an Institute for Developmental Psychobiology in New York City. My application was aided by the fact that my brother headed the Neuro-oncology Department right across the street. Moreover, there was a clear need for students trained to understand the developing human brain, and the presence of scanning and other facilities in New York was attractive. During my stay in New York, it was possible to recruit B. J. Casey and Bruce McCandliss to the Sackler Institute faculty, and they have given it a leadership role in pediatric neuroimaging and in the new area of brain and education.

According to theories developed by Mary Rothbart, a control system develops in late infancy or early childhood that involves attention and can also be measured through parental reports as a higher-order variable she called effortful control. Since the executive attention system involves the anterior cingulate, which is well activated by conflict, we developed a series of conflict tasks that could be executed by children. Scanning with fMRI in New York, Jin Fan was able to show that these various conflict tasks activated a common network, including the anterior cingulate gyrus.

I never expected to study individual differences. Cognitive psychology was about mental processes common among humans, and I thought one of the most important results of the early neuroimaging studies was evidence that the data of subjects could be averaged to provide a common anatomy even for higher mental tasks where one might have suspected a lot of individuality. Of course the early PET data had a large area of blur in activity due to averaging, so, despite evidence for commonality, there was also opportunity for individuality. The development of fMRI has allowed enough data to be collected on an individual that activity can be plotted in relation to the anatomy of the individual brain, thus opening the way for more detailed analysis of individuality in brain activation.

Two things tipped me in the direction of wanting to study individual differences. First was the influence of Mary Rothbart’s elegant theory of the role of effortful control in child socialization. Our data showed that all during childhood there were correlations between the executive attention network measured in cognitive tasks and parent-reported effortful control. This seemed remarkable evidence that individual differences in laboratory experiments were important enough to relate to the diverse behaviors of everyday life that would be obvious to parents.

The second reason was due to meeting John Fossella and Tobias Sommer at the Sackler Institute in New York. They both had been trained in molecular biology, John to the Ph.D. level, and were eager to explain to me some of the new opportunities opened up by the human genome program. With the support of Mary and her team in Eugene, we set out to measure adult individual differences both by questionnaire and experimental test and to determine how they might be influenced by genetics. John Fossella took cheek swabs from 200 New York adults and using the magic of polymerase chain reaction (PCR) was able to genotype them for dopamine genes. We found that individual differences in the attentional network that related to effortful control were influenced by dopamine genes, and an fMRI study, conducted by Jin Fan, B.D. showed that the genetic differences influenced the degree of brain activation in the anterior cingulate.

Sometimes the effort to relate genes to brain networks and complex behavior is taken as evidence that everything is hard wired and that experiences are unimportant. This of course is not at all true. In a study of 2-year-old children we found, for example, that children with the 7-repeat allele of the DRD4 gene were greatly influenced in critical aspects of behavior by the quality of parenting. However, for children without the 7-repeat allele, parenting made little difference in these same aspects of their behavior. The results with the DRD4 gene were particularly important, because they led us to the hypothesis that genetic variation might be selected in human evolution because they made the child more influenced by culture factors like parenting.

Mary Rothbart attended a meeting at NIH and reported that Duane Rumbaugh and David Washburn had trained monkeys in a version of the Stroop effect. Since conflict tasks such as the Stroop served as a marker of executive attention, we decided to adopt their methods to train preschool children. With Charo Rueda, we developed a training program based on the animal research and randomly assigned 4- and 6-year-old preschool children for 5 days of training in this program or to a control group using interactive videos. We found clear improvement in the executive network at both ages. Subsequently, Rueda showed that this small amount of training still had an effect after 2 months. At the time we did these experiments it seemed unlikely that such a small amount of attention training could improve brain networks, but subsequently there has been quite a lot of research showing improvement in attention with different methods. In 2007 Mary Rothbart and I published our volume Educating the Human Brain. It reviews our efforts to train attention in preschool children, and we still hope it may help lead to improved experience for children in preschool that might influence their later education.

Most of the work on training has involved practice with a specific brain network. In our case we tried to systematically exercise the brain’s executive attention network. However, more recently I have joined with Dr. Yiyuan Tang in proposing a second method which might be useful. In this method we attempt to train the brain state. Brain states are being studied a lot these days, thanks to Marc Raichle showing the importance of the default state. In our studies, we used a version of meditation adapted from traditional Chinese medicine (integrated body-mind training [IBMT]). With

U.S. and Chinese undergraduates randomized to IBMT or to a relaxation training control condition, improvements were found in executive attention and in cortisol secretion to a cognitive challenge. These changes appeared to involve a combination of central and autonomic (parasympathetic) system enhancements. In the case of IBMT there are no specific exercises involving practice of attention. Instead one attempts to induce a highly relaxed but mentally focused state.

Currently we continue training studies and are examining how attention networks are shaped by genes and experience in children from 7 months to 4 years of age. Examining individual differences may seem a somewhat surprising method to identify genes involved in the development of common brain networks. However, I believe that those genes related to individual differences in the efficiency of a particular network will prove to be the same as those involved in building the general network. Future research will determine how sound this logic is.

It is now over 50 years since I first began to study psychology. At the time I began my work in my fondest dreams I could not have imagined that we would be discussing the mechanisms of voluntary control, and using neuroimaging to determine which brain areas are involved and genetic variation to examine how those brain areas were developed. When I married in 1958 and my wife asked why I wanted to go to graduate school, I told her, “To figure out how the brain works.” Although we have a long way to go, it seems to me that in these 50 years I had a wonderful opportunity to help make a start.

Selected Bibliography

Abdullaev, Y.G., & Posner, M.I. (1998). Event-related brain potential imaging of semantic encoding during processing single words. NeuroImage, 7: 1–13.

Badgaiyan, R., & Posner, M.I. (1998). Mapping the cingulate cortex in response selection and monitoring. NeuroImage, 7: 255–260.

Fan, J., Fossella, JA, Summer T., Wu, Y., & Posner, M.I. (2003) Mapping the genetic variation of executive attention onto brain activity. Proceedings of the National Academy of Science USA 100: 7406–7411.

Fan, J., McCandliss, B.D., Sommer, T., Raz, M., & Posner, M.I. (2002). Testing the efficiency and independence of attentional networks. Journal of Cognitive Neuroscience, 3(14): 340–347.

Posner, M.I. (1978). Chronometric Explorations of Mind. Hillsdale, NJ: Lawrence Erlbaum Associates.

Posner, M.I. (1980). Orienting of attention. The 7th Sir F.C. Bartlett Lecture. Quarterly Journal of Experimental Psychology. 32: 3–25.

Posner, M.I., & Boies, S.J. (1972). Components of attention. Psychological Review, 78: 391–408.

Posner, M.I., & Keele, S.W (1968). On the genesis of abstract ideas. Journal of Experimental Psychology, 77: 353–363.

Posner, M.I., & Mitchell, R.F. (1967). Chronometric analysis of classification. Psychological Review, 74: 392–409.

Posner, M.I., & Petersen, S.E. (1990) The attention system of the human brain. Annual Review of Neuroscience, 13: 25–42.

Posner, M.I., & Raichle, M.E. (1994). Images of Mind. New York: Scientific American Books.

Posner, M.I., & Rothbart, M.K. (1998). Attention, self regulation and consciousness. Philosophical Transactions of the Royal Society of London B, 353: 1915–1927.

Posner, M.I., & Rothbart, M.K. (2000). Developing mechanisms of self-regulation. Development and Psychopathology, 12: 427–441.

Posner, M.I., & Rothbart, M.K. (2007). Educating the human brain. Washington DC:APA Books.

Posner, M.I., Boies, S.W., Eichelman, W., & Taylor, R. (1969). Retention of visual and name codes of single letters. Journal of Experimental Psychology Monography, 79: 1–16.

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Peter H. Schiller

BORN:

Berlin, Germany

May 5, 1931

EDUCATION:

Duke University, B.A., Psychology (1955)

Clark University, M.A., Psychology (1959); Ph.D., Psychology (1962)

Postdoctoral training, Psychology Department, MIT (1962–1963)

MILITARY SERVICE:

U.S. Army, 1955–1957

ACADEMIC POSITIONS:

Research Assistant, Austen Riggs Center, Stockbridge, MA (1953–1960)

Research Assistant, Clark University, Worcester, MA (1961–1962)

Lecturer, Massachusetts Institute of Technology, Cambridge, MA (1962–1964)

Assistant Professor, Massachusetts Institute of Technology, Cambridge, MA (1964–1968)

Associate Professor, Massachusetts Institute of Technology, Cambridge, MA (1968–1971)

Professor, Massachusetts Institute of Technology, Cambridge, MA (1971–present)

AWARDS AND HONORS:

Dorothy Poitras Chair for Medical Physiology, MIT (1986)

National Academy of Sciences, U.S.A. (2007)

American Academy of Arts and Sciences (2007)

Honorary member of the Magyar Tudományos Akadémia, Hungarian Academy of Sciences (2008)

Peter H. Schiller, in collaboration with numerous investigators, has carried out research using psychophysical methods, single-cell recordings, microstimulation, and pharmacological manipulations. The research has examined (1) the neural underpinnings of visual illusions and visual masking, (2) retrograde amnesia, (3) the neural control of eye movements, (4) the functions of the midget and parasol systems that originate in the retina, (5) the functions of the ON and OFF channels of the retina, and (6) the functions of extrastriate areas in visual processing. Studies at the present time are engaged in assessing the feasibility of creating a prosthetic device for the blind based on electrical stimulation of area V1 and in specifying the neural mechanisms that underlie depth processing.

Peter H. Schiller

Beginnings

In the early 1930s my father and my mother moved to Berlin, Germany, from Budapest, Hungary, because my father had obtained a fellowship to work with Wolfgang Köhler, an eminent Gestalt psychologist, who at that time was head of the Psychological Institute at the University of Berlin.

I was born in Berlin in 1931 and lived there during the first 2 years of my life. It was only natural, therefore, that the first language I had learned was German. Speaking predominantly in German continued after we had moved back to Hungary. This was due to two prime reasons. We spoke German at home because my father, who had written many of his papers and some of his books in German, wanted to remain highly proficient in that language. The second reason was that due to the very busy life my parents led, they successively hired several fräuleins to take care of me. They were all German. Consequently, my Hungarian language skills were quite limited when I entered grammar school. As a result, the first 2 years in grammar school were rather difficult for me. In Hungarian education, a great deal of emphasis is put on memorization. For example, we had to commit many poems to memory. Poetry plays a notable role in Hungarian life, to the extent that sometimes it is said that in Hungary everyone is a poet. And the culture has indeed created numerous wonderful, outstanding poets. So one of the tasks we had in grammar school was to memorize poems, which we then had to recite in class. Because of my limited language skills I had great difficulties with this, in particular with poems containing infrequent words. It was almost like trying to memorize nonsense syllables. As a result, for a while I was considered to be mentally retarded. Countering this deficiency of mine I immersed myself in memorization. In the ensuing years I memorized hundreds of Hungarian folk songs as well as numerous piano compositions by Bach, Bartók, and Kodály. I especially loved Bartók’s works based on Hungarian folk songs, and I still have a copy of one of his music books entitled For Children. I am proud of the fact that I had actually met Béla Bartók in my early teens. His house was just down the street from where we lived.

In spite of my father’s busy life, he devoted considerable time to my upbringing. He taught me to ski and skate from a very early age, he started me playing the piano, and then made sure I had the best piano teachers. He also supervised me as I was learning to write. I am left-handed and my father was determined to make me write right-handed. Initially he gave me copying assignments and instructed me to use my right hand. He would then leave the room briefly to attend to other tasks. Being rather obstreperous already then, I quickly switched hands to complete the assignment. Soon my father caught me doing this, so for each session he proceeded to tie my left hand down to the chair in which I was sitting. So in the end my father won out and I learned to write right-handed. This training had its benefits because it made me more or less ambidextrous.

My oldest child, my son David, is also left-handed. But I have never had the inclination to force him to learn to write right-handed. Back in the days of my youth left-handed people were often considered inferior and clumsy. My father’s motivation was perhaps to prevent people viewing me as a clumsy dolt.

My mother worked in the Hungarian equivalent of the Library of Congress. She would bring home numerous books for me to read, making it one of her projects for me to become an avid reader. My favorite author at that time was Jules Verne. I had read almost all of his books translated into Hungarian. 20,000 Leagues under the Sea sticks out in my mind probably because this book was also turned into a movie I have seen.

In Hungary one of the most popular vacation sites is Lake Balaton, which is the largest lake in Central Europe. My parents and I had spent time there repeatedly during some of the summers because my father was engaged in research at an institute in one of the smaller towns along the lake named Tihany; some of this work was carried out on fish. My father was also a pilot and loved gliding. I joined him on numerous occasions, as I also did later in my life when we lived in Florida. Soaring silently in the sky in gliders was an exhilarating experience.

After the first two grades in grammar school, I was sent to a private boarding school. I learned subsequently that this happened because my parents had decided to get a divorce. This private school was located in one of the plushest sections of the Buda, on the top of a hill with a very large garden. It was a secure place, originally the property of a rather well-to-do family, surrounded by a beautiful high iron fence. The entrance gate was always locked. The road up to the palatial house was serpentine. Three-quarters of the way up there was a striking, large statue of Venus overlooking the valley below. This statue had gained a special significance for me. Although I was only 9 years old at the time, at this boarding school I fell madly in love with one of the girls named Ágnes. We managed to get together on several occasions in the evening at the base of the Venus statue. In my mind’s eye I can still see Venus basking in the light of the full moon.

Sadly, some 30 years later when I returned to Budapest for a visit after the Iron Curtain had been lifted, I visited this school, which by then had reverted to a private home. The entrance gate was all rusty and askew. I walked up the hill to Venus only to see that one of her upper arms had broken off and parts of her legs had also crumbled, revealing the rusted metal posts underneath. Looking at this sad scene, I was reminded of my passionate love, which had long faded into the past. After leaving this school for upper school, I never saw Ágnes again. I still wonder occasionally what happened to her.

At this school I also made friends with two boys who were identical twins. I got to know them well enough to be able to tell them apart. We played many games together. One day, playing soccer on the large terrace adjoining the house, one of the twins kicked the ball over the railing. We ran to the edge hoping not to lose sight of the ball only to see it land on the ground and gain speed rolling down the long hill and disappear. This was a major crime and we had to do anything to find the ball. The twins, in desperation, suggested that we walk down the hill and while doing so keep chanting “The devil will help us find it.” Well, we spent quite a bit of time doing this, but the devil was of no help. By this time several other students joined us to find the ball. Not much caring for this chanting ploy to find the ball, I now suggested an alternative. We got hold of another soccer ball and I had my friend kick it in the same manner as he did initially. The rest of us, spread out, watched the descent of the ball. We kept running down the hill as the ball kept rolling. Eventually it came to rest near the fence close to the entrance gate. And, lo and behold, there was the other ball just a few feet away. This event gained me accolades and played a role in my becoming sort of a leader of our little group of boys attending the school.

Our teacher, named Rózsa-néni, was a very tough, sometimes meanspirited individual. She was a firm and forceful teacher from whom we learned a lot. I did make her very angry once. During one of our spelling lessons she asked the class why the word hallani—which means to hear—is spelled with two l’s. In Hungarian, learning how to spell is actually quite easy because the words are spelled much as they are pronounced. She pointed to me to answer her question and I stood up as required. At a loss, I finally blurted out “because we have two ears.” This prompted laughter in the class. Our teacher felt I was making fun of her and ordered me to the front. Once there she told me to hold out my hand—I extended my left hand—which she then smacked sharply with a ruler. The right answer, of course, is “because it sounds that way.”

This teacher had one interesting habit. She often had some sliced bread on a plate when she was teaching, and she would tear off a central piece and proceed to knead it with her fingers. Eventually she would discard the wellkneaded piece of bread only to repeat the process. My twin friends got into the habit of collecting the discards and put them on a shelf inside a wooden cabinet in our common bedroom, where the 15 boys attending the school had slept. The dozens of these odd creations looked a bit like little modern sculptures with captivating, highly varied shapes. Today they could probably be sold in an antique store.

Our teacher, who was born in one of the small towns of central Hungary, Öcsöd, had two sisters who still lived in that little town. One of them, named Eti-néni, often visited at the school. For reasons I cannot remember, we became quite friendly. This led to another significant set of experiences in my early life. I spent several summers with this family in the town of Öcsöd, which exposed me to an entirely different form of life steeped in agriculture. I made a good friend there, Pinka János, whose father was a carpenter. János and I ended up spending a lot of time in his father’s shop. Initially, father Pinka was most reluctant to let me touch anything there because I was left-handed and he considered lefties clumsy and inferior. But eventually he realized that I had considerable manual skills—I was in fact more skillful than János—so he ended up giving me numerous little tasks, as a result of which I learned a great deal about woodwork and carpentry that had many long-term benefits in my life.

War Years

When in the early 1940s I entered secondary school in Budapest, called gymnasium in many European countries, I became a close friend with a fellow student. We used to meet before classes started in the morning and frequently took walks in a park near the school. One day we talked about friendships and he proclaimed emotionally, “We will always be best friends!” I agreed with him heartily. A few days later, when we met again, he was wearing a yellow star on his jacket. I looked at it and my first thought was, being rather naive and ill-informed, that he had won some sort of award. He then explained to me that he was Jewish and a new rule had just come into effect: every Jew in Hungary, as in several other European countries, was required to always wear the yellow Star of David. A few days later my friend did not show up to meet me in the morning. I have not laid eyes on him ever again.

Shortly after this incident, the bombing of Budapest started in earnest. Hundreds of planes flew over the city, mostly at night, dropping thousands of bombs causing extensive damage and killing many. During part of this period I lived with my grandparents on my father’s side because they had a large apartment overlooking the Danube River that was closer to my school than the homes of my parents. I adored my grandmother who was a vivacious, beautiful woman with whom I had discussed many things about life, especially about the nature of war. She was a fine pianist and a great art collector. One of her favorite art productions was the Sicilian Triskelion symbol, which appears in many different forms, always consisting of three interlocked legs or spirals, often with a central human face. The symbol is part of the Sicilian flag, is the basis of the roundel of the Irish Air Corps and a great many other displays throughout the world. My grandmother’s prime collection consisted of various pieces of China-ware decorated with the Triskelion. She even had a pendant made with this symbol that she always wore.

The warning signals for the frequent bombing raids were sirens going off throughout the city. When this happened, we were instructed to go down to the basement for safety. My grandmother was claustrophobic and refused to comply. So instead, perhaps spitefully, she often took a walk on the deserted streets during the raids. One day, after the sirens had sounded the second time, indicating that we could leave the basement, my grandmother was not in our apartment. In fact, she never came back and was never found. There was extensive bombing damage in the neighborhood the night this happened, and we presumed that she had become a victim. Subsequently, I spent time trying to find her body without success. I had thought I could locate her because of the Triskelion pendant she had always worn.

After this terrible incident I moved back to my father’s and stepmother’s place in one of the suburbs of Budapest, the so-called Hüvösvölgy. This was a beautiful house with a large garden that had numerous fruit trees. It had belonged to my stepmother’s well-to-do parents. Her father was the CEO of the Hungarian Railroads. Shortly after I moved there, the Russian invasion of Hungary started. After further bombing raids and the relentless sound of the slowly approaching cannons, the Russian Army reached Budapest. A prolonged battle arose between them and the Germans, who gradually withdrew, except for a small contingency that had set up fortifications in the Castle of Buda, which ended up resembling wars in the Middle Ages where castles were surrounded and then invaded. The Castle was under siege for several days. The Germans then broke out in an effort to escape. Every one of them was killed. By this time the city had been devastated. There were thousands of burned-out vehicles and tanks along many of the main roads and dead bodies everywhere. To slow the advance of the Russians, the Germans had blown up all the bridges on the Danube that connected Buda and Pest, and they also destroyed endless miles of railroad tracks using a specially designed giant railroad car that had a device on it that broke the tracks every few yards with a twisting motion.

During the battle in Budapest, as the Russians advanced slowly, our house in the Hüvösvölgy became a headquarters for the commanders of one of the Russian divisions. We were confined to one room in the house. The conduct of the Russians was merciless. Rape was one of the most common occurrences. On one occasion, upon entering the large kitchen of our house, I got a momentary glimpse of such a rape. Three soldiers held down the stripped body of one of our help, a young woman whose job had been to look after my little sister, while a fourth soldier kneeled between her legs with his pants down. A fifth solider quickly slammed the door in my face but not soon enough to obliterate this image that is still vividly in my head.

The Russians caused major damage to our house, breaking dishes, toilets, and bathtubs. One drunken night—their alcohol consumption was obscene—two of the officers sat down in front of our beautiful grand piano, on which my father had started my piano lessons, and used a hammer to hit the keys, breaking them irreparably.

Mercifully, the Russian army left after a few weeks, advancing toward Germany, leaving behind devastation. Due to the fierce combat and profuse killings, in addition to the burned-out vehicles and tanks, there were weapons and explosives strewn everywhere. To prevent their reuse, the Russian soldiers would remove the firing pins and throw them away. Being at loose ends at this time since the schools were not running, a good friend of mine and I got involved in all sorts of nefarious activities. One of our favorite games became to find the thrown-away firing pins and match them to the rifles and machine guns strewn all over the place. We had some success and actually had put together a little weapons arsenal, including stacks of various bullets. We hid these in the basement of a nearby deserted, bombed-out house. We never fired any of these weapons but, going into the nearby woods, we would take rifle ammunition and after removing the bullet would lay down the casing, pour out a bit of the gun powder, and then light it. We then quickly crouched behind nearby trees until the explosion took place which, of course, had not much of an effect on anything. My favorite weapon in our arsenal was a shiny little pistol—pistols were very rare in the rubble—but we never managed to find bullets for it.

Perhaps one of the goriest undertakings during this period was to bury the thousands who had died during this phase of the war. The smell of death was rampant as the dead bodies began to decompose once spring approached and the snows melted. Groups were organized to find the bodies and take them to collection sites. Because of the acute shortages in Budapest, the wood to make coffins was also in short supply. To minimize this problem, one unseemly, but unavoidable practice became to construct foreshortened coffins into which the decomposing bodies had been placed with the lower legs bent over 180 degrees at the knees. Gradually the city was cleared of the dead and their odor dissipated.

Another consequence of the extensive damage to the roads and the destruction of the railway system was acute food shortage. One item that remained in reasonable supply was dried beans. To prevent us from developing an aversion to them, clever means had been devised in many households to prepare them in all sorts of different ways. Beans were often prepared for breakfast, lunch, and dinner. But to this day I find it next to impossible to eat beans.

About 6 months after the Russian invasion, the city was cleared of the dead, and the roads were repaired as were the railroad tracks. Reconstruction had begun and the schools reopened. Life gradually returned to normal but did so without ever erasing the impressions and memories of these war years. A new government was formed dominated by communists.

Around this time I spent another summer in Öcsöd. With so much of Europe devastated, these were difficult times. I joined a little workforce whose task was to raise silk worms for the purpose of harvesting silk for a company that made clothing. We were told that our reward, after several weeks of hard work, would be a new pair of shoes for each of us. This undertaking had its source in the fact that one of the most common trees, many of which still line the roads on the Hungarian Plains, is the mulberry whose leaves silk worms love to eat. So we spent our days climbing these trees collecting leaves in big sacks. The worms were ravenous. Their demand was so great that by the latter part of the summer most of the trees in the area had become bare. We had to walk to progressively more distant locations to collect leaves, which wore out our shoes; so we were really looking forward to our promised earnings. Mercifully, the worms eventually got to the stage of weaving their silk cocoons. Once completed, the cocoons were packed into large boxes and were carted away to the factory that created silk clothing. Disappointingly, after our work had been finished, we were informed that the undertaking was less successful than had been anticipated. As a result we did not receive shoes. Instead, they gave each of us a pair of leather shoe soles. In those days all shoes were made of leather and their soles often had to be replaced.

Getting back to Budapest at the end of that summer, I went to live with my mother in her family’s villa in another beautiful part of Buda. This villa, which was also on large grounds, had three floors. My mother and I lived on the ground floor and my cousin Andrea, with whom I became close friends, on the top floor.

My grandfather, who had the villa built originally, well before the war, was a powerful, innovative, and fearless individual. He was the CEO of the Anglo-Hungarian bank and consequently was financially well off. He also bought a car at that time, a Mercedes. The single-lane driveway to the garage was a long one and he did not like having to drive the car that distance in reverse to get back onto the street. So he had the garage modified to contain two rotaries. Once the car was driven onto one of them, pressing a button rotated the car around 180 degrees with an electric motor. He had two of them built, I suppose, because he was planning to buy a second car—something that was seldom done in those days. Creating these rotaries may have been a clever idea, but the system kept breaking down until it could no longer be repaired. So my grandfather just parked his car at the beginning of the driveway when he got home from work in the evening.

Another unusual idea that my grandfather had came about because he snored loudly at night, which made the life of my grandmother miserable. He wanted to continue having the two of them sleep together, so he had a huge new bed built in their bedroom with a central partition that could be pulled down from the ceiling. The partition was reasonably well sound proofed. My cousin Andrea and I tried this out one day when my grandparents were away. We lay down on the bed and then I started to make loud snoring sounds. She then pulled down the partition and yelled, “Can you hear me?” Indeed, she was barely audible.

My grandfather never did buy a second car and soon he became fatally ill and passed away shortly before World War II got under way.

Once I moved into the villa with my mother after the war, my cousin Andrea and I became inseparable. We had many friends in the neighborhood and frequently we played a game in our yard that was popular at the time called Number War. The game has two teams, a defending one and an attacking one. The site of the defending team is generally marked by a flag, which was the object to be seized by the attacking team. We wore cardboard plaques attached to our heads with four numbers on each. The two teams were identified by virtue of having different color plaques. Whenever the numbers worn by an individual were correctly yelled out by a member of the opposing team, the warrior was declared to be dead and had to leave the area. To prevent the reading of the numbers, the participants hid their heads behind trees, bushes, and buildings, peering out sideways to peruse the scene. This was, and probably still is, an absorbing game, which at the time was especially popular among Boy Scouts.

Andrea’s father, my uncle, often took exception to my conduct, sometimes deservedly so, and meted out punishment by forbidding me to play with my cousin. One of these arose when I figured out a way for speeding up my descent from the top floor of our villa where Andrea lived to the ground floor where I stayed with my mother. The elegant circular staircase had an inner railing with a nice smooth polished wood balustrade secured with glazed iron posts to a continuous marble ledge next to the inside portion of the steps. I learned to hook my arm around the top of the railing and place the soles of my shoes onto the marble ledge. This allowed me to slide down to the first floor rapidly. The speed of descent could be controlled by varying the force with which I squeezed my arm. Due to my frequent slides down the staircase, the inner portion of the marble ledge gradually became quite shiny in contrast with its outer portion. One day my uncle came home as I was whizzing down the staircase. He had already noticed the shininess of the marble but did not know its source. He told me I must stop this unseemly practice, but of course I did not obey him. He caught me again flying down the steps a few days later and furiously forbade me to see my cousin Andrea for a week.

On another occasion the lights went out on the top floor and my uncle accused me of being the culprit. I had nothing to do with this, and in short order I fixed the problem by replacing a burned-out fuse. This did not help things and I received another week’s punishment.

To combat this frequently occurring separation from Andrea, I tried to come up with some way of communicating with her. At this time there were still numerous bombed-out buildings in the neighborhood which had not yet been repaired. Some of the ruined material was stacked at the edge of streets for eventual removal. Common here were discarded wires, some of them telephone wires. For reasons I cannot remember, I started to collect such wires. I then had the idea that perhaps I could communicate with Andrea using the Morse code, which at that time was a prime communication system. Many of us had memorized the code. Andrea’s room on the top floor of the villa was on the same back side of the building as mine on the ground floor. So after a lot of fiddling, I had put together two telegraph keys that produced an audible click with each press. I then connected our rooms, leading the wires I had twisted together through the windows and up the outside wall next to a down spout. Soon we were communicating with each other using this system, although it was not uncommon that we had difficulties understanding each other. When this happened, we would rush into the stairway and yell toward each other from the ground floor to the top floor. The most common yell was, “What did you say?”

During one of the punishment days when we were yelling like this my uncle entered the villa. Seeing us talking when we had been forbidden to do so resulted in another week’s punishment. So we devised a safety procedure to minimize this happening: Whenever any of our parents came home unexpectedly while we were beeping away, we quickly sent an SOS signal (). Fortunately, my uncle never found out about our Morse code system. Otherwise I might have been punished for life.

A few years ago Andrea, who now lives in Beirut, sent me a postcard. On the top of the face page are the words in bold, “Morse Code,” and below are the letters of the alphabet with the dots and dashes of the code for each. I have posted this card on the wall of my office to the left of my computer. Looking at it now reminds me of these long-ago times and makes me realize how much the world has changed since then. No one nowadays knows much about the Morse code. New technologies in communication and the computer revolution have obliterated it.

Another fun thing Andrea and I did while we lived together in the villa, for which we were not punished, was stargazing. I had become enamored with the night sky and went on to memorize the constellations. Our yard in the villa was well suited for this purpose as it was located near the top of the hill, providing thereby an excellent view of the sky. We would spend hours outside at night with a map and a flashlight in hand; gradually we learned a great many of the constellations. Some years later I learned that David Hubel also had a passion for the stars. On one of our trips, as described in a subsequent section, we embellished this knowledge in Australia.

The political climate and the many changes instituted by the Hungarian government pressured by the Russian domination spelled an uncertain future. My father soon realized that his prospects in Hungary as a research scientist and university professor were in serious jeopardy. So he decided to leave the country. He was offered a position in America and so in 1947 he, my stepmother, and my half-sister emigrated legally. Their beautiful home in Budapest, following extensive repairs, was rented out to the U.S. Ambassador to Hungary.

Once my father, stepmother, and my sister Christina, who was 7 years old at this time, got settled in the United States, procedures began to enable me to join them. I was put through the emigration process and was very fortunate because, having been born in Germany, I was on the German quota system, which had more slots and thereby allowed more immigrants to enter the United States than Hungarians. So in 1948 I left Hungary. I took the train to Prague and then flew to London, where after a few days I boarded the Queen Elizabeth that landed in New York after five stormy days.

The Queen Elizabeth was a remarkable ship, the largest of its kind in the world at the time, 83,673 tons. It was extremely fast. During the war years it was used to transport troops. Due to its speed, it typically sailed solo because no other ship could keep up with it. Many years later when I flew to Hong Kong, as we were approaching the airport there, the pilot pointed out the hull of the Queen Elizabeth, which was lying on its side, half submerged in the harbor. The ship had been decommissioned and the intent was to turn it into a museum. Due to a major fire that had erupted during this conversion, the ship was destroyed. Her sister ship, also owned by the Cunard Line, fared better. This ship, the Queen Mary, has also been converted into a museum but with success. She is still beautiful and now resides in the harbor at Long Beach, California.

Initial Years in the United States

Once I arrived in New York, I was looked after by a friend of the family. They were wonderful and took me to museums, to the Statue of Liberty, and to the top of the Rockefeller Center. I was then put on a train that took me to Jacksonville, Florida, where my father and stepmother picked me up. We drove to Orange Park, some 12 miles from Jacksonville. This is the place where my father worked in the Yerkes Laboratories, which some of the locals called the Monkey Farm. The head of the laboratory was Karl Lashley.

While living in Orange Park, my father often took me to the Yerkes Laboratories, where I assisted him in his experiments, some of which at the time were concerned with examining detour behavior. This work was done in several species of animals. We tested cats at home in the evening in a maze I had built with my father. On many weekends we took trips to the Marineland Aquarium. Here my father carried out experiments examining detour behavior on octopi. It was most instructive for me to become familiar with this intriguing species.

The investigators at the Yerkes Laboratories formed an impressive group. I have met several of them: Karl Lashley, Henry Nissen, Josephine Semmes, Edward Evarts, Karl A. Pribram, and Robert A. Blum. Blum and his wife, a childless couple, were rearing a really cute baby chimp in their home. I learned later, as is so often the case, that as this chimp grew older it became unmanageable and had to be returned to the enclosures at the Yerkes Laboratories. Pribram, an eminent neurosurgeon, kindly sent me a copy of his book, Brain and Perception, in 1991.

Henry Nissen was a gentle, wonderful person with a house right on the St. Johns River. I was invited to visit his place on numerous occasions, and I became a good friend of his daughter, Joanna. Some years later, Henry, who carried out developmental studies, went to remove an infant from a chimp called Helene. The chimp, who turned out not to have been sufficiently tranquilized, attacked him, resulting in serious damage to his back from which Henry never recovered. His health deteriorated, and in 1958 he committed suicide.

Karl Lashley was a most lively individual and quite a jokester. He was an avid sailor like my father. One day I had the honor of sailing with him on his beautiful yawl named Skidbladnir. Having learned that I had some sailing experience, he instructed me to take over at the wheel. While sailing against the wind on starboard, he instructed me to come about to port, which is normally achieved by turning the wheel clockwise. When I did this, instead of what I had expected, the boat did the opposite and bore off staying on starboard. I was dumbfounded. Lashley laughed merrily and told me that he had reversed the steering arrangement by twisting the line that connects the wheel to the rudder into a figure eight. I am not sure whether he did this because it was an easy way to tighten up a loose connection or to play games on his friends.

Lashley became world famous for his research achievements, the most controversial of which was his equipotentiality theory according to which all areas of cortex are equally important in learning (Lashley, 1929). This theory by now has been proven to be quite wrong. I sometimes can’t help but think that Lashley had proposed it as yet another one of his jokes.

In 1965 the Yerkes Laboratories was moved to Atlanta. I visited there once many years later and was surprised to recognize an old, graying chimp I had known back in Orange Park in 1949.

During the two summers I had spent in Florida I worked two different jobs. One of these was as a caretaker and counselor in a summer camp called Camp Seminole. This camp was quite close to Henry Nissen’s house, which was one of the reasons I visited him so often. The camp was fun but nothing much of interest happened there other than my learning how to play baseball. The second summer I worked as a waiter and host at a restaurant called the Rainbow Grill. I remember the owner and his wife fondly; they were very kind people who often allowed me to spend the night at their home right next to the grill when I had worked late hours. At the Rainbow Grill I met up and became friends with a very interesting person by the name of Bobby Byers. He taught me many things about life, mostly about its seamier sides. He was a hunter and instructed me in how to shoot pistols and rifles, reminding me of our weapons collection in Budapest. Mostly everything Bobby and I did ended up in competition. We shot at various targets with his weapons and he beat me regularly, but gradually I got better. We played chess a great deal, which was one of my hobbies at the time. Having read several books on chess, I became fairly good at it and I ended up beating him most of the time. This only propelled him to want to play me more, determined to better me. Bobby also taught me about prostitutes with whom he apparently often dealt. Sometimes he would pick one up at the Rainbow Grill or when we were driving around in the seedier parts of Jacksonville. This was where I drew the line, as I did not want to be educated in this aspect of life.

Bobby had served as a pilot in the U.S. Navy and was eventually dishonorably discharged for repeatedly flying too low. He was often at loose ends. Bobby liked to drink and once he crashed his mother’s car and suffered some rather deep cuts on his face. Some years later Bobby got a job as a pilot to fly crop dusters. One day, flying too low, he crashed. The plane blew up and burned him to cinders.

In early 1949 my father spent time carrying out experiments on rats in the laboratory of B. F. Skinner at Harvard. While there, one day he went on a skiing trip to Mt. Washington. As he was heading down at Tuckerman’s Ravine, he fell into a crevice near a large boulder and was killed. He was just 41 years old. His name is now listed in the Sherman Adams Summit Building on top of Mt. Washington along with 140 other individuals who have perished on the Presidential Range. The large boulder is now called Schiller’s Rock.

After my father died, my stepmother found a position as a teacher at one of the top private schools in Jacksonville, the Bartram School. Since this was a girl’s school, I could not join her there. So I ended up in Charleston, South Carolina, where I lived with another friend of my father’s, Jim Anliker, a physician who held a position in the Anatomy Department at the Charleston Medical School.

While I lived in Charleston my stepmother and Karl Lashley fell in love and married in 1956. This ended up being a rather short marriage because Lashley died unexpectedly when they took a trip to France in 1958; he was 68 years old. My stepmother died in 1988. Her major scientific contribution was a book she had edited in 1957 entitled Instinctive Behavior, which contained an introduction by Lashley and chapters by Konrad Lorenz, Jakob von Üxkull, Nicholas Tinbergen, and my father (Schiller, 1957).

Jim Anliker took great care of me in Charleston. He got me a job in the Anatomy Department where he worked. I had two responsibilities. One was to tend after a group of monkeys housed in the animal quarters. The other was to help out keeping things in order in the department. The least appealing part of this job was to clean up the large room in which the medical students dissected cadavers.

The staff in the Anatomy Department was very friendly and helpful. I got involved in photography and learned how to develop film and make enlargements in the darkroom of the department. I was given a 35mm Leica camera by my stepmother and ended up taking innumerable pictures and spending many hours processing them in this darkroom, which fortunately was otherwise quite unused. How different things are now! With a digital camera one can get an instant view of the pictures taken and erase the unwanted ones. Those selected can be processed without ever going into a dark room.

Jim Anliker is a great pianist and organ player. One of his passions at the time was to explore the sounds and quirks of various organs in the Charleston area. I accompanied him to numerous churches where my task was to record his organ playing on a tape recorder. Many years later Jim moved to Boston. I visited him there once. He had a rather large apartment there in which he had several pianos. I had spent an enchanted evening there listening to him playing various classical pieces and explaining to me how the pianos differed. Some years later I spent another enchanted evening like this when I visited Mickey Goldberg at his home. Mickey is also a superb pianist. He played several classic pieces, which made the experience much like going to a concert.

Jim Anliker had yet another interesting attribute. He was an avid collector of unusual, enigmatic, and profound quotes. He printed these quotes on slips of paper, which he then mounted on his office walls, increasing their number week by week. I loved this hobby of his, so to this day I do the same thing but with a bit more moderation. Worth noting perhaps are three of these which are on the same wall as Andrea’s Morse code card: Knowledge is folly, except grace guide it (George Herbert). All predictions are wrong. That is one of the few certainties granted to mankind (Milan Kundera). Except that I had changed the word predictions to hypotheses. The third is a cartoon by Barsotti that displays a disheveled, sweating guy who appears to be walking on a road in the direction indicated by an arrow on which the word truth is inscribed. Looking down one can see that this guy is actually on a treadmill.

Jim Anliker and I had rented a wonderful apartment on the top floor of a house owned by a Mr. Gibbs, who, as it turned out, was an English teacher at the high school I had attended during the 11th and 12th grades in 1949– 1951. Gracefully, he took it upon himself to improve my English and I was proud to receive an A in his class. Mr. Gibbs was color blind, which was the first source of my interest in color vision. He told me one day that he had just gotten a ticket for running a red light in Charleston. This happened at a site where for some obscure reason the green light was on top and the red on the bottom. Since he could not differentiate these colors, he inferred them on the basis of their position. I was surprised, and always being a skeptic, the next day I went to check it out. This was indeed the case; the red light was on the bottom, green on top. I can only presume that this mistake has been corrected by now.

I led a very busy life in Charleston and, once again, made several good friends. Having become a reasonably proficient swimmer in Hungary at an early age, I thought I might be good enough to become a member of the school swimming team. It turned out that I was. To do really well, I swam endless laps on a daily basis at the local YMCA. This effort paid off. I competed in the breast stroke, the free style, and the medley relay at the numerous meets we had and I managed to come in first every time. This was really because these teams were not very strong. One of the rewards of this was that at the senior closing graduation ceremonies I received one of the two trophies that had been given out. The other one went to the star quarterback of the football team who was also a good friend. But we both were big frogs in a small pond. My friend never became a starting quarterback in college.

During my last year in high school I had the good fortune of being mentored by the psychoanalyst David Rapaport, who was yet another friend of my father’s. Originally also from Hungary, David Rapaport became a major figure in clinical medicine. He held a position at the Austen Riggs Center in Stockbridge, Massachusetts, where he was a good friend of Erik Erikson’s. Rapaport was a remarkable scholar, who had written several books. The two-volume book entitled Diagnostic Psychological Testing, which collectively came to more than 1000 pages, was first published in 1946 and went through 15 printings. Another book he had written, entitled The Organization and Pathology of Thought, was first published in 1951 and went through four printings.

Rapaport took me under his wing and I spent several years working with him at the Austen Riggs Center in Stockbridge, Massachusetts, which at the time was a psychoanalytically based institution for the treatment of the neurotic youngsters of wealthy families. I worked there through two summers and while in graduate school at Clark I took weekly 1-day trips to Stockbridge. During one of those summers I also served as a tennis instructor in the Austen Riggs athletic center. Erik Erikson’s wife was in charge of this program. Tennis had become another of my passions around that time. As a result, I had the privilege of interacting with her as well as with Erik on quite a number of occasions. Surprisingly, by virtue of being involved in tennis, I had met Richard Dyer-Bennet and ended up playing with him many times. I remember that several years later, when I was at MIT, Richard gave a concert at our Kresge Auditorium to a packed audience. In the middle of one of his songs he suddenly went silent, a silence that was broken when he proceeded to tell the audience that he had momentarily forgotten the words of the second verse of the song. Following another brief pause, the words came back to him and he continued. Upon finishing he received a thunderous ovation. Sadly Richard died in 1991 at the age of 78.

During the summers I was at the Austen Riggs Center I received rigorous training in assessing and criticizing the books and articles Rapaport had assigned to me to read. We met daily one on one. He trained me extensively in Freudian theory. I had to read many of Freud’s books, most notably among them the Interpretation of Dreams. Initially he lent me his copy of the book for me to read in which he had some notes and comments on just about every page. Subsequently I got my own copy, which I still have. In this book, trying to imitate Rapaport, I made notes and comments on many pages.

One of the minor accounts in this book now comes to mind. A patient seen regularly by Freud had challenged his central contention that dreams are wish fulfillments. She told Freud that she had a dream the night before in which she wanted to give a dinner party, but when she went to the store to purchase what was needed for the dinner, she found the store closed. So she asserted that her dream was not a wish fulfillment. Freud did not bat an eye (I am just saying this since I was not there). You just did not want to give a dinner party, he asserted with certainty. In the book he elaborates his reasons fairly convincingly.

Subsequently I often wondered about why dreaming had become so pervasive in mammals. Animals, just like humans, dream regularly and I doubt that they have what can be identified as ids, egos, and superegos. Subsequently, as a result of work I did that involved the immobilization of one eye in rhesus monkeys, as described a little later, I came up with a much less profound idea about why dreaming evolved in the first place. My theory asserts that dreaming came about to induce eye movements during sleep, as in REM (rapid eye movement) sleep, which assures that the eyes remain well rounded and the corneas remain smooth and polished. When the eyes are prevented from moving, they become misshapen and the corneas become ridged. I have learned that animals that hibernate also move their eyes about during hibernation, presumably by virtue of dreaming about something. But then in their dreams maybe they are roaming about freely in warm weather with plenty of food around. Wishes fulfilled.

This training with Rapaport came in very handy. Subsequently I taught a course on personality for a while at MIT as well as sections in other courses on Freudian theory.

Another person I recall during the time I had spent at the Austen Riggs Center is Daniel Kahneman, who had also worked with David Rapaport. Kahneman received the Nobel Prize in Economics in 2002. While at the Austen Riggs Center, we played around with some experiments that subsequently I pursued in more detail. Kahneman is now at Princeton. I met him there recently at the wedding celebration of Charlie Gross and Joyce Carol Oates; it was wonderful to reminisce about our time with Rapaport, whom we both held in awe.

The crowning influence of Rapaport in my graduate training was my Ph.D. thesis in which several aspects of learning were examined based on a theory Rapaport had developed which was called the Theory of Attention Cathexis. Rapaport did not participate in the last phases of this thesis work because he suddenly died of a heart attack in 1960. He was only 49 years old. I had the honor of being one of his pallbearers. Some years later I joined forces with another disciple of Rapaport, Fred Schwartz, to write a monograph on this theory (Schwartz et al., 1970).

The most satisfying project I had carried out at the Austen Riggs Center was actually one that George Klein had inspired me to do. George was a close friend of Rapaport’s and visited the Austen Riggs Center frequently. He was a professor at NYU. He was both incisive and generous. In the course of several discussions we had, he brought up the idea of us doing a developmental study using the color-word interference test devised by Stroop. The Stroop test involves the naming and reading of colors when the colors and words are in harmony and when they are in conflict, such as the word red printed in blue ink. Klein had carried out such experiments on adults and the idea now was to determine how the interference arises in development. We got permission at two schools to do this work, one in Pittsfield and the other in Newton, Massachusetts, where I now live. The test takes only about 10 minutes per subject. I ran 240 subjects starting with students in the first grade and also tested college students. The experiment was a lot of fun to run, and the results were gratifying, showing a dramatic rise in the interference that occurs in the naming of colors when they are in conflict with the color words during the first, second, and third grades as the kids learned to read. This is followed by a subsequent decline in the magnitude of the interference. George helped me with the data analysis and the writing of the paper, but then he refused to be a coauthor, saying that he wanted this to be my sole work (Schiller, 1966). This was certainly most magnanimous of him. I took this disposition to heart and subsequently had many students who had done independent work in my laboratory, which was then published by them independently as well. George Klein, like David Rapaport, passed away quite young. He died in 1971 at the age of 53.

I spent two summers at the Austen Riggs Center. Before and after that I spent summers as a counselor in a summer camp in Vermont. I came to work in this camp because it was the place where my stepmother and my sister, Christina, spent their summers. My mother was the executive secretary. The camp was founded in 1939 by Kenneth Webb and his wife, Susan Webb. The camp originally had two sections at opposite ends of the lake, one for boys and the other for girls called Camp Timberlake and Camp Indian Brook. Subsequently a third area was added in-between for older kids. I was a canoe instructor for the boys and took them on extended canoe trips to places like Lake Saranac and Lake Memphremagog and the upper Connecticut River. To be able to teach canoeing and to take canoe trips, the first summer before camp started, Webb sent me to a most instructive canoe school in northern Vermont. He paid for this. One wild canoe trip we took once I was back at Camp Timberlake was down the rushing waters of the upper Connecticut River, where we managed to crash up one of the canoes, which terminated all subsequent canoe trips on this river.

Another great attraction at this camp was horseback riding. We had stables and many horses. My sister Christina became deeply involved in this aspect of the camp, to the extent that eventually horses became her profession. She attended Smith College, where she continued to pursue this passion. Christina now has a place in Florida called the Quiet Hill Farm, which specializes in equestrian jumpers. She has trained hundreds of kids there, some of whom, including her daughter, have participated in numerous competitions. Christina often serves as a judge at such events to this day.

The creator of these summer camps, Ken Webb, died in 1984 at the age of 82. His wife, Susan, became active in politics in subsequent years. She wrote a book entitled The Susan Howard Webb Story: A Memoir. She celebrated her 100th birthday in 1995.

At the camp I became a close friend of Frank Sieverts, with whom I have had several adventures. One summer Frank and I decided not to go to camp. Instead, we made plans to go to Alaska. We met up at Swarthmore, where Frank was a student at the time. On the way we decided to stop off in Thiensville, Wisconsin, where Frank’s parents lived. This is a little town just north of Milwaukee near Lake Michigan. Once we got there, we had a change of heart and decided not to go to Alaska after all. Instead, we both got jobs and spent the entire summer in Thiensville. I found a job with a construction company where I became a dump-truck driver. We worked more than 10 hours a day. My prime job was to cargo gravel from gravel pits to construction sites. Often my task was to lay down gravel smoothly on newly made driveways. This was accomplished by driving the truck slowly forward or backward and gradually raising the truck bed to pour out the gravel evenly. There was a strong motivation to do this well because otherwise I had to do a lot of shoveling to create an even surface.

Another summer, this time after we had worked at Camp Timberlake, Frank and I decided to go to Colorado to do some serious mountain climbing. I had read up on rope climbing and, at considerable expense, purchased a coil of climbing rope along with the appropriate implements that included pitons used to secure the rope to the rocks as we were climbing.

This trip was both exhilarating and disastrous. We went to Estes Park and then, to acclimate, spent several days doing ordinary hiking. One of these hikes was to the top of Longs Peak along a relatively ordinary, if steep trail. We then decided to get into real rope climbing. We hiked up to the east face of Longs Peak that consisted of a virtually sheer cliff of several thousand feet. About halfway up there was a more or less horizontal break in the cliff, which is named Broadway. Broadway is barely a foot or two in width at most places. We had gotten hold of reports describing the layout of the cliff and strategies for scaling it. We made it up to Broadway without incident. It took quite a few relays to get to this point. Due to other climbers, there were numerous pitons nailed into the rock walls, so I only had to hammer in just a few of them along the way. Each end of the rope was tied to our waist. I would climb along until the rope was stretched to its end. I would then secure my position and wait until Frank climbed up to join me; I made sure to keep the rope taut between us by coiling it as Frank got closer. We then walked along Broadway until we got a steep glacier that stretched up to near the peak of the mountain. We took one relay at which point Frank took over the lead because he had boots better suited for the glacier than did I. I secured myself in a good sized crevice between the glacier and the rock formation and Frank proceeded up. I soon lost sight of him as he moved around a rocky protrusion. Then, suddenly, I heard him scream and saw him slide around the protrusion along the glacier gaining speed. This was a terrible moment because I realized that once he slid down to Broadway he would be propelled over the ledge and catapult down toward the base of the mountain more than 1000 feet below. For a moment I thought my only chance to survive was to untie the rope from my waist so that he would not drag both of us to our deaths. But I realized there was not enough time for that. So I quickly pulled as much of the rope as I could toward me. Once he slid past me I threw the rope around my neck and used both hands to try to slow his slide. Miraculously, I managed to bring him to a halt just as he hit Broadway. But this was at a considerable expense. The abrasion of the rope caused welts on my neck as well as on my hands. They were quite deep and some of my fingers began to bleed profusely. I tried to stanch the bleeding with my shirt and handkerchief. After moderate success I climbed down slowly to where Frank was waiting. The hike back down and then to Estes Park seemed like an eternity as we had to take numerous relays with Frank now taking the lead by letting me go first and keeping the rope taut as I descended. Once we got to Estes Park we went to a hospital where they bandaged me up. One of my hands was completely encased and I had extensive bandages also around my neck.

The next day we decided to head home. Running short on money we thought it most advisable to hitchhike back east. In the outskirts of Estes Park we were picked up by two friendly guys who were driving a brand new car. Their friendliness was fueled by the beer they were drinking. As we were driving down along the long and steep downhill road from Estes Park at a moderate speed, a car passed us rather closely. For reasons still unclear to me, this enraged our driver who proceeded to recklessly pass this car right back going around a curve. As soon as he did so, it became evident that the curve was too sharp for him to make it. With the tires screeching, the right side of the car slammed into the sheer rock to the right of the road which then propelled us to the other side where the left side of the car smacked into the retaining guard rail, luckily preventing us from catapulting into the abyss. Eventually we came to a halt. Hanging on for dear life my hands started to bleed again. We were instructed to get out of the car and disappear. We did so with haste, noticing as we did so that this lovely new car had become a total wreck. Two near-death accidents in a row.

We managed other rides, first to Denver and then to Chicago, where Frank and I parted company. He headed back to Thiensville and I back to Duke. Given my grotesque appearance with all the bandages, hitchhiking became difficult, so eventually I took the train from Pittsburgh to Durham, North Carolina, leaving me broke.

Subsequently Frank and I sent letters to each other on several occasions with newspaper clippings of deadly accidents suffered by climbers in the Rocky Mountains. Looking at my right hand now I see that the marks left by the burns from the climbing rope are still in evidence.

Frank and I remained in contact for several years thereafter. I visited him at Swarthmore a few times where his roommate was Michael Dukakis. Subsequently Frank became a specialist in refugee and relief issues at the State Department and then an executive in the Washington office of the International Committee of the Red Cross. He died in 2004 at the age of 70. We were close friends and I mourn his loss.

In the early 1950s my cousin Andrea, her father Andrew, and her mother also immigrated to the United States. They set up residence in Queens, New York, where I visited them on several occasions. I made sure to be well behaved on these occasions. My uncle was a famous newspaper reporter in Hungary, had spent time as a foreign correspondent in Turkey during the war, and in the United States had started a company in the 1950s that provided information of recent news events called Deadline Data. He worked inordinately hard and read numerous newspapers every day. This relentless hard work had created problems with his eyes and subsequently with his heart. He had quadruple bypass surgery, which was declared to be a success. But my uncle died a few days thereafter. In his will he left me a beautiful winter coat which he had purchased shortly before his death. I still wear this coat every now and then to remind me of my uncle.

College Undergraduate Years

Upon my arrival at Duke in the fall of 1951 one of my first tasks was to secure a job because my financial situation was precarious. I landed a fine job in the cafeterias, where my job the first year was to clear tables during and after one of the three meals offered daily. This took up to two hours a day. For this work I was given free meals, which was most generous indeed. In subsequent years I was “promoted” to work at the dishwasher center in the main kitchen area, where my task was to take the clean dishes and silverware as they emerged on a continuous belt from the gigantic dishwasher. The dishes were then stacked on large rolling carts.

Working with me was an interesting character whose nickname was Hooksie. He earned this name by virtue of the fact that when he played basketball—we often played together on pick-up teams—every shot he made was a hook shot yielding a low success rate. I have never seen him take a regular shot. Hooksie was a couple of years ahead of me in school. When time came close to his departure from Duke, one day as we were stacking the dishes I asked him: “Hooksie, aren’t you going to miss your friends here?” Hooksie looked at me, raised his hand dismissively in an abortive hook shot and said: “There’s friends everywhere.”

The athletic department was apparently well aware of my swimming skills and they wanted me to join the Duke swimming team after I won a race among the incoming freshmen in breast stroke. By this time I was sick of swimming and could not face spending several hours a day in the pool taking laps. So I declined. Instead, I joined the soccer team and played varsity soccer for 4 years. This was a lot of fun because we took numerous trips to play matches at various universities. We had some really fine players; two of them became all-Americans, and one year we won the Atlantic Coast championship.

Starting shortly before going to Duke, as already noted, I had become enamored of tennis and very much wanted to make the varsity tennis team. I had become friendly with several members of the team. The coach was supportive and I soon got the job of stringing tennis racquets. Finally, my junior year I made the team, although I never held a position higher than #6. Our number-one player that year was Buzzy Hettleman, an excellent athlete, whose first name was Kalman, a Hungarian name. Originally his grandfather’s name, it subsequently became a family name so that most members of his family have this as a middle name. Like me, Buzzy served 2 years in the Army after graduating from Duke as we had a conscription system at that time. He also served in Germany and on one occasion, when I was in Stuttgart, we met up to play tennis. We just hit because I was no match for him. This was a lot of fun for me in spite of the fact that he assured me, after we were done, that I hit the majority of my ground strokes out of bounds. Buzzy went on to an illustrious career and has published a book recently about education in the United States entitled It’s the Classroom, Stupid (Hettleman, 2010).

Due to the high scores I had gotten on the college entrance exams in chemistry, I was placed into an advanced chemistry course my first year at Duke. By this time my infatuation with chemistry, induced by a remarkable teacher at the Charleston high school, has faded and I ended up not doing well in this course. Instead, I became involved in psychology. Karl Zener was the director of graduate studies at the time I was at Duke and became chair of the Psychology Department in 1961. He was yet another friend of my father’s. He and several other members of the department were most supportive of the students and provided opportunities to run little experiments. I spent quite some time examining visual discrimination in fish. This work was done under the supervision of Gregory Kimble who had written an influential book entitled Principles of General Psychology.

An unpleasant incident at Duke occurred as a consequence of one of the despicable practices this institution had at that time: Freshmen were required to wear blue caps called dinks, so everyone they encountered could tell right off that they were just mere frosh. One evening, as I was walking back to my dorm on the campus, I was accosted by three townies. The relationship between the Durham population and Duke was always tense and animosity was rampant. These townies I encountered demanded my dink, which I gave them fearfully. During the following days I walked around the campus dink-less. Soon I was called in front of a judiciary committee whose members were mostly upper classmen. I was told that unless I started to wear my dink right away I would have to wear a yellow dink, which was the mark of students who had committed misdemeanors. I was also told and that unless I obeyed, I would lose my job at the cafeteria. I explained what had happened and accused Duke for being lax in providing student protection on campus. The committee, which I consequently considered a bunch of quislings, did not care. I also told them that as long as they paid for it I would be happy to buy a yellow dink. They refused that too. I then went to the Duke Dope Shop—I do not know where that name came from—as I intended to buy a yellow dink myself. My obstreperousness failed because I was told that they could only sell a yellow dink if I had gotten written approval from the administration. So in the end I was compelled to buy a second blue dink so I would not lose my cafeteria job. As an ineffectual protest, I drew a picture of the famous Duke chapel wearing a yellow dink on its spire.

In spite of this incident, my life at Duke remains memorable. It is at Duke that I had met and fell in love with Ann Howell. We got married shortly after I graduated from Duke. By that time I was in the U.S. Army, a requirement then due to our conscription system at the time.

In the Army

So after getting my B.A. degree at Duke, I had to serve 2 years in the Army. Initially this requirement filled me with deep resentment. This feeling gradually receded as a result of the incredible experiences I had during this period. To the extent, in fact, that now I sometimes feel that having a conscription system has important benefits. It matures individuals and expands their horizons by exposing them to new experiences and new situations. It also serves to bring different factions of our society together and assures that the Armed Services are a part of our nation, not a separate, isolated entity.

In the 8 weeks of basic training I learned how to use a great variety of weapons and how to kill. This was not new to me, having had extensive exposure to war and death during World War II and having done quite a bit of shooting with Bobby Byers. One minor aspect of this training, relevant to my future work on vision, was how to shoot a rifle at night without night goggles. We were instructed to aim by looking off to the side a bit so that the image would impact on perifoveal regions of the retina that contain both rods and cones; rods are absent in the fovea. The existence of two these two kinds of photoreceptors, the rods and cones, was discovered by Max J. S. Schültze in the 1860s when he developed a new procedure to stain neurons in the retina (Schültze, 1866). Initially no one believed him. Now it is a true, basic fact. In trying to figure out what the rods are for, he cleverly noticed that they were absent in the fovea where night vision is quite poor. Noting this he hypothesized, correctly, that rods are for night vision. Had the Nobel Prize been in effect at that time, he would surely have been awarded it.

After basic training I was sent to clerk-typist school where I learned to touch type. I did not realize at the time that in my life I would be spending hours every day in front of a computer banging away on a keyboard. This training alone made my service in the Army worthwhile.

I was then sent to Frankfurt, Germany, where I became a clerk-typist in the medical section of the Fifth Corps Headquarters that was housed in the I.G. Farben Hochhaus, a large building in the outskirts of the city. One curious arrangement in this tall building was that it had continuous elevators with open doors. The cars moved slowly and we had to time carefully the entering and exiting of the elevator. Numerous accidents occurred, mostly minor, making it evident why this elevator design had demised.

For the first few months in Frankfurt I was billeted in a caserne the Germans had used during World War II. It was located in the outskirts of the city, as was the 5th Corps Headquarters which had belonged to a paint conglomerate that manufactured mostly explosives during the war. Neither of these building complexes was damaged much by the relentless bombing raids during the war which had destroyed and leveled large sections of the city, including the opera house.

Shortly after starting my service in the medical section, I was severely reprimanded by the colonel in charge. After firmly standing at attention, as instructed, he berated me for trying to be an individualist soldier. I was mystified. Yelling at me, he then told me that I was wearing my belt backward—something no one had noticed before. Initially I could not fathom what he meant. Turns out that being a lefty, I always put my belt on my pants starting on the left side, so that once the end of the belt came around, its tip emerged to the right of the belt buckle. He made me reverse this right then and there. After leaving the service I have returned to my former evil ways of wearing belt buckles “backward.” Our sterling colonel did not seem to notice that I was wearing my watch on my right wrist, which I did, of course, to be an individualist.

One of my fellow clerk typists in the office was quite a character— Corporal Black. His hobby was race-car driving. He raced most weekends at various locations in the area. We became well acquainted and he taught me a great many things about driving. It was like learning this skill all over again. Ever since then I had always purchased stick-shift cars.

During the summer of 1956, my wife, Ann, joined me after having graduated from Duke. The Army was most generous, and we were allowed to live in a rented apartment in the city. We purchased a Volkswagen Beetle— which came with a stick shift—and took many trips visiting places in Switzerland, France, and Italy. Frank Sieverts visited us once and we reminisced about our past exploits, mostly about Longs Peak.

The major occurrence while I served in the Army in Frankfurt was the outbreak of the Hungarian revolution. When this happened I rushed to the intelligence division of the 5th Corps headquarters and told the general in charge, who kindly consented to see me, that I speak fluent Hungarian and therefore could be of some help dealing with this crisis. The general looked me up and down and dismissed my offer. “The Army is always prepared,” he told me. “Ever hear of Monterey?” I shook my head. “It’s a school in California where selected individuals in the armed forces are taught various languages in 9 months, including Hungarian. After they master a language they do whatever is required. So we have trained people to deal with this situation.”

He went on to accuse me of using this as a ruse to get out of the impending field exercise and dismissed me. A few days later we did go on this field exercise in a forest near Frankfurt. One of my jobs was to erect a large tent with several other noncommissioned soldiers. We drove to the site in a large truck, which in addition to the tent had some wooden posts sticking out in the back. I learned from one of the soldiers that these were a part of the four-poster bed for the general. Honest!

The next day a jeep arrived at the site to pick me up. I was driven back to Frankfurt. The Army kept great records and had established from my forms that I spoke Hungarian. I was then sent to Stuttgart for 3 weeks for intelligence training. That is when I met up with Buzzy Hettleman to play tennis as noted earlier.

After this intelligence training I was sent to Munich, which at the time was the prime location to which Hungarian refugees had been sent by train. I worked in a small intelligence outfit in a beautiful villa that, right after the war, had been confiscated from a high-ranking Nazi. My job was to interrogate Hungarian refugees for military information. This was a fascinating job. I met many Hungarians from many walks of life. One of them actually provided us with some rather useful information about Russian fortifications near the Yugoslavian border. We had one other Hungarian enlisted noncommissioned officer in our group, and we also had two trainees from Monterey “ready to do whatever is required.” Except they could not do so. Their language skills were dismal, and I ended up having to interrogate many of the refugees that had originally been assigned to them.

My wife joined me from Frankfurt shortly after I had started my intelligence work in Munich. Again, we were allowed to live in a rented apartment, this time in a lovely suburb of Munich, Schwabing. Because of the nature of my service, I was told never to wear an Army uniform. So I blended in well. Luckily, I still spoke German fairly well, so we lived comfortably in the city. We loved living there, visiting the museums of the numerous remarkable sites nearby. We even rented sailboats on several occasions on the Starnberger Lake south of Munich.

During this period I spent a great deal of time studying for the GREs. My wife, an English major, was of great help in expanding my vocabulary. I learned hundreds of new words in preparation for the test. I ended up doing quite well, but still remember one analogy question I could not answer. This question asked something like this: a monkey is to cage as chicken is to—followed by four words. One of the words on this list from which the choice had to be made was coop. I made the wrong choice as I had no idea what the word coop meant. But I do now!

I was delighted to learn that I was accepted into the graduate program of the Psychology Department at Clark University, which actually was the only place to which I had applied. The chairman at the time was Heinz Werner, yet another acquaintance of my father’s. Due to my training with David Rapaport and George Klein, I had developed a strong interest in mental illness and in development. Werner was a developmental psychologist who had written an influential book at the time entitled Comparative Psychology of Mental Development (Werner, 1940).

Graduate Training at Clark

In the fall of 1957 my wife and I arrived in Worcester to start my graduate training at Clark University. This was a dramatic change after my 2 years in the U.S. Army. A repeated reminder of our time in Germany was the Volkswagen Beetle, which we had bought there and then had shipped back to the States. We continued to have this car for many years because we were both fond of it.

At Clark I was reminded daily of Rapaport and the research I had been doing with him because as one walked up to the top floor of our building where the Psychology Department resided, one passed by a statue of Freud. The reason for this was that Freud, before he became world famous, was once invited to Clark University to give a presentation back in 1909. This occasion is still heralded there, and a photo depicting Freud with several other prominent individuals is on display. They are Stanley Hall, after whom the building housing the Psychology Department had been named, Carl Jung, A. A. Brill, Ernest Jones, and the Hungarian Sandor Ferenczi. Prominent figures, now largely forgotten.

My supervisor at Clark was Morton Wiener. At that time he had worked on subliminal perception and got me involved in experiments studying this phenomenon. At this time subliminal perception became a popular topic because it was claimed that when at movie houses the word Drink Coca-Cola was flashed subliminally between frames, viewers would rush out in droves during the intermission to purchase the product. Based on our research we argued that rather than it being some mysterious, extrasensory event, subliminal perception is actually due to the perception of partial cues. As it turned out, this was the first published research article that had my name on it (Wiener et al., 1960).

While this research on subliminal perception was a fun undertaking, it did not hold my interest long; my interest shifted to examine visual illusions and visual masking. To carry out this new line of research, I designed a five-field stereoscopic tachistoscope, which enabled us to carry out interocular experiments. Stimuli in this device could be flashed on separately for each eye either simultaneously or successively. The department had a nice little shop, which fortunately was little used. I got permission to work there and I was able to do so without anyone else bothering me. Morton Wiener provided funds for the electronic device that could drive the fluorescent lights in the five compartments of the device. Once constructed, I carried out experiments on illusions and visual masking. In both of these types of experiments the question we addressed was to what extent various illusions and masking effects occur before or after the input from the two eyes has converged in various cortical areas. By carrying out the experiments on illusions systematically, we showed that the Ebbinghaus, Poggendroff, Müller-Lyer, and Ponzo illusions occur centrally, not peripherally. This was a debate at the time. Our ability to present stimuli interocularly for brief durations minimized binocular rivalry. The magnitude of the illusory effect was similar for binocular and interocular presentation conditions, which was not the case, as reported in some other studies in which much longer duration presentations were used that did induce binocular rivalry.

Several years later I returned to the study of illusions. In a recent study with Christina Carvey we examined the Hermann Grid illusion, which according to Gunter Baumgartner is attributable to the center-surround organization of retinal ganglion cells. By systematically varying stimulus conditions, we established that this theory is wrong and that the illusory effect is attributable to cortical mechanisms (Schiller et al., 2006).

After the initial work on illusions using the five-field tachistoscope, I turned to the study of visual masking which occupied parts of my research efforts for several subsequent years. This work was inspired by a wonderful series of experiments Heinz Werner had carried out on contour interactions in the 1930s (Werner, 1940). One line of this work had examined temporal interactions generally called metacontrast masking. When a disk and a ring are presented in rapid sequence, with the contours of the inner portion of the ring and the preceding disk shared, the disk is not perceived when the interval between the presentations of the two images is between 60 and 100 milliseconds. The conditions under which this effect occurs have been extensively studied by several investigators. Upon reading this work and carrying out informal little experiments, I became fully aware of the fact that there are several different types of masking. For some of these a monotonic function is obtained with the strongest effect occurring when the two stimuli appear in succession without a temporal interval. Such masking is dramatic when two homogeneous stimuli are presented in the same location but with the second stimulus being bigger and having a higher contrast than the first; this kind of masking earned the name brightness masking. A third effect, also yielding a monotonic function, is pattern masking when, for example, the first stimulus is a letter and the second a crisscross pattern with both having similar contrasts. What I wanted to determine was where in the visual system these masking effects occur. The first step in this effort was to determine whether masking occurs at a peripheral or a central level in the visual system. Using the stereoscopic tachistoscope I had built enabled us to address this question by presenting both stimuli either to the same eye or by presenting them interocularly. This work was carried out in a series of experiments that continued even after I became a postdoctoral fellow at MIT. Our basic finding was that brightness masking occurred only when both of the two successive stimuli were presented to the same eye, whereas pattern masking and metacontrast occurred even under interocular presentation conditions (Schiller, 1969).

Heinz Werner, like Rapaport, died while I was still in graduate school. This was 1964 when he was 74 years old. His position was then taken over by Seymour Wapner.

While carrying out this work on visual masking I decided that it would be beneficial to get a clinical degree in psychology, especially since I had extensive exposure to topics pertaining to mental illness, predominantly as a result of working with David Rapaport. The upshot of this was that I took a clinical internship during my fourth year at the Worcester State Hospital. This ended up being a most interesting and eye-opening experience. After some initial training I saw patients on a daily basis carrying out psychotherapy. I was closely supervised by a wonderful psychiatrist who was willing to spend many hours discussing the cases and instructing me in the conduct of the therapy. He was a very busy person and on several occasions I met up with him at his house in the evening to be supervised. Here I was stunned to find out that his wife was a morbidly depressed individual who spent most of her time in bed. He was working on this problem and was confident that she would overcome this situation. I never learned whether this was indeed the case.

I remember two patients in particular I saw during my internship. One of them was admitted after an acute case of catatonia. She could barely move and her jaws seemed to be locked so she could hardly speak. During the many months I worked with her she improved gradually and was eventually discharged. A little later she sent me a letter thanking me for curing her. I felt most embarrassed about this because I think I really had little to do with her improvement. It is known that often, after such a sudden onset of a psychological disorder, improvement occurs over time with or without psychotherapy. Sadly, what is also known is that when, after the “cured” individuals return to the same setting that precipitated the initial episode, they will often have another breakdown. This is the revolving door phenomenon in mental hospitals.

The second case was one in which the patient had been pulled over on the Massachusetts Turnpike for driving erratically. When the officer approached him, he vociferously announced that he is Jesus Christ. He ended up, of course, in the Worcester State Hospital. He remained Jesus Christ for quite some time while I was “treating” him. We had the most bizarre conversations, I must say, but eventually he relented, calmed down, and a few months later was discharged to return to the situation that precipitated the psychotic episode. I never heard from or about this person again. For all I know, he is now Jesus Christ again.

While my clinical training at the Worcester State Hospital was most interesting and instructive, I realized that this kind of work was not my cup of tea. I wanted to return to research full time.

During the latter part of my stay at Clark I began to look into possible postdoctoral opportunities. In particular, I wanted to learn neurophysiological methods so I could carry out experiments at the single-cell level to explain visual masking. The person I turned to was another friend of my father’s, Hans-Lukas Teuber. He held a position in Psychophysiology Laboratory at the New York University-Bellevue Medical Center in New York and lived in Dobbs Ferry. I visited him several times at his house, and we discussed possible research opportunities as a postdoctoral fellow in great detail. We took long walks in the neighboring woods, where he told me about the exciting work of David Hubel and Torsten Wiesel, work that I subsequently read repeatedly in great detail. Teuber had just accepted a position as chair of the Psychology Department at MIT and so my prospect was to join him here. I was delighted to have this opportunity.

Postdoctoral Work

So after graduating from Clark University, I became a postdoctoral fellow at MIT with Hans-Lukas Teuber. This period was not only quite productive but was also central in forming the future directions of my research. Teuber was a remarkably supportive mentor who allowed me to work in several different areas. He provided me with ample space and funds to carry out several lines of research.

When I arrived at MIT, the Department of Psychology, of which Teuber had become the chair, was still largely unformed. It was Teuber’s task to organize and build this department. He had an interesting vision. He did not want a department that dealt only with psychological issues. He wanted a much broader representation that included brain science. He did this effectively by making a series of outstanding appointments. Notable among these was Walle Nauta, who was a famous neuroanatomist. One of the students trained in his laboratory is Ann Graybiel, who subsequently became a faculty member of our department, has been inducted in National Academy of Sciences and recently became an Institute Professor at MIT. Walle Nauta was a striking personality with whom I had extensive contact. It turned out that he was also an avid sailor and had a sailboat just like mine (a Thistle). He and I were in the same yacht club in Boston Harbor and during the spring, summer, and fall seasons we sailed races just about every weekend. This club had several outstanding sailors, including Joe Duplin who sailed Stars and won the world Star championship one year. One day, when he was at loose ends at the club, Duplin volunteered to crew for me and provided me with many cues to improve my sailing skills. One of these I still vividly remember. As we were sailing along, one my cleats got jammed temporarily. He firmly instructed me to replace it right away: “Once it jams, it will jam again,” he assured me. This is true for most things, so I have learned to take his advice in hand. Whenever something in my laboratory malfunctions, I replace it to prevent it from happening again.

The other outstanding sailor, also in the Thistle class, and the winner of most of our Thistle class races, was Hatch Brown. I mention him because subsequently he became the sailing master at MIT. MIT is situated right along the Charles River and sailing is taken quite seriously here. During the weekends and on most weekdays, the river is festooned with hundreds of sailboats, many of them from the MIT Sailing Pavilion. Some of us in the department take advantage of this luxury and sail out of the pavilion periodically. Sadly, the Charles River is quite polluted in spite of repeated projects to “clean up the Charles.” On a rather windy day, some years ago, I shipped in about two feet of water into the boat I was sailing, narrowly missing a capsize. Looking down after the boat had been righted, my shoes under the dark brown turgid water could not be seen. While the ocean waters in Boston Harbor are not exactly clear, they are much less polluted than the Charles. So capsizing there, which had happened to me several times, was not nearly as disconcerting.

Shortly after becoming a postdoc at MIT, I became friendly with Steve Chorover and Charlie Gross. We spent a lot of time together and were often referred to as the three musketeers in the department. I ended up carrying out numerous experimental projects with both of them as will be described later.

The first line of work I did at MIT was a continuation of the examination of visual masking. Teuber provided financial support to build a new five-field tachistoscope in one of the instrument shops at MIT. This turned out to be a real Cadillac in comparison with the one I had built at Clark. The displays in each field could be adjusted with millimeter precision. The base of the device was made of a ¾ inch thick aluminum plate. In collaboration with Marylin Smith and Alan Greenfield, we carried out several experiments to further test masking under both monocular and interocular conditions (Schiller, 1969; Schiller et al., 1966, 1969).

Teuber also strongly encouraged me to learn single-cell recording techniques to enable me to study the neurophysiological underpinnings of visual masking. I carefully read the technique sections of many papers, particularly those of Hubel and Wiesel and of Peter Bishop in Australia. I was given the funds to purchase the necessary equipment, which included optic benches, a Xenon arc lamp, stereotaxic instruments, amplifiers, microdrives, oscilloscopes, and printers. I learned how to operate on animals to enable me to record from single cells in the brain. Particularly difficult for me was to learn how to make good microelectrodes. This was a time before I met David Hubel, but I was friendly with one of his students, Michael, who was the son of Francis Crick; he invited me over to the Hubel laboratory at the Harvard Medical School, and he ran me through the process of making varnish-coated tungsten microelectrodes. These are the ones I then used in the experiments recording from the lateral geniculate nucleus of the cat. I found, perhaps not surprisingly, that brightness masking had its source in the retina. The rapidity with which information is processed through the retina to the retinal ganglion cells is contrast dependent. When visual stimuli have low contrast, the processing takes longer than when they have high contrast. Consequently, the response of the retinal ganglion cell to the dim stimulus is taken over by the response elicited by the subsequent bright masking stimulus. I carried out this work on my own and was consequently the sole author on the resultant paper (Schiller, 1968, 1969).

Concurrently with doing these masking experiments I started a project with Steve Chorover that examined retrograde amnesia, an area Teuber had encouraged us to pursue. We trained rats on several tasks and then administered electroconvulsive shock to induce memory loss. In the first set of experiments we used the Hebb Williams maze. This is a most clever device in which, using partitions, the route from the entrance to the location of the reward the rat was after could be endlessly varied. We brought in numerous hooded rats, which we initially allowed to roam around in large groups to become familiar with this wonderful maze. One day, looking as the ceaseless running around of the cute rats, Steve remarked: “Seething ratmanity.” The things one remembers!

Initially these experiments were unsuccessful. Electroconvulsive shock administered after a rat had learned a particular maze pattern did not interfere with what had been learned. So we decided to start something different. Based on the work of some other investigators, we built a one-trial learning apparatus which had a little pedestal in the center of an enclosure and an electric grid below. The natural tendency of all rats, once they were placed on the pedestal, was to step down onto the grid. When they did so they received a mild electric shock. The next time they were placed on the pedestal they did not step down. This exemplified one-trial learning. During the experiments we then took the rat out after the animal had stepped down and we administered electroconvulsive shock. Much to our dismay, these treated animals the next day remained crouched on the pedestal. Their onetrial learning was not interfered with by the electroconvulsive shock.

For a while we were stumped and began to doubt much of the literature on retrograde amnesia. But then Steve had a great idea. Right down the street from our laboratory there was a fastener factory we were always aware of because of the constant humming of the machinery that stamped out the fasteners. Steve suggested that we attach fasteners to the rats’ ears so that when they stepped down in the apparatus they could receive electroconvulsive shock instantly. So we went to the factory, where the staff was extremely helpful and friendly. They supplied us with boxes of fasteners for our experiment. We got so many of them that we could still run these experiments today were we so inclined. We then proceeded to administer instant electroconvulsive shock and suddenly got dramatic results. When the shock was administered right after the step-down and up to a 30-second delay, the animals the next day, once placed on the pedestal, stepped down right away as if they had never encountered the situation before. We referred to this as short-term retrograde amnesia and published a paper in Science describing the work, which received considerable attention (Chorover et al., 1965).

Steve Chorover and I were quite feverish at this time and we got involved in several other projects. To further pursue the metacontrast effect, Steve and I carried out an experiment in which we collected evoked potential data in the human posterior cortex. As reported in a Science paper, we found that even when the masking was optimal, the evoked potential generated by the first stimulus, the disk in the disk-ring sequence, was of the same magnitude as when it was clearly visible, indicating that this effect occurs at higher levels in the visual system (Schiller et al., 1966). These findings were in consonance with a study Marylin Smith and I had carried out examining metacontrast, showing that if a forced-choice discrimination task is used in which two rings are presented to the left and right of the initial fixation, subjects could always specify whether the preceding disk had been presented with the left or the right ring. Furthermore, the response latencies were the same throughout the various temporal intervals used between the appearance of the disk and the ring. The results we obtained in these experiments led me to suggest that the metacontrast effect is linked to apparent motion; when a stimulus like a disk appears successively at two locations, motion is perceived and the initial location is discounted (Schiller, 1969; Schiller et al., 1968).

We also carried out several other experiments examining learning and retrograde amnesia. One of these studies, in rats, examined the effects of spreading depression and callosal sectioning. This work was inspired by Jan Bures, who had done a great deal of work on spreading depression. We also carried out some conditioning experiments in planaria, which we had collected from under the rocks in the waters of nearby lakes in Cambridge. Work using planaria was hot at the time resulting in many publications in The Worm Runner’s Digest. In one series of studies James V. McConnell reported a cannibalistic experiment in which planaria were fed chopped-up soul mates that had been trained in a conditioning experiment in which the conditioned stimulus was light and the unconditioned stimulus was electric shock. The claim was that as a result of this feeding, planaria learned faster when the planaria fed to them had been conditioned than when they were unconditioned. Our work was simply interested in retrograde amnesia, so we tried to interfere with the conditioning using a variety of means. Nothing of much significance came of this work and we never published anything on the planaria work. But doing the experiments was certainly a lot of fun. What I did learn from these efforts is that you need to keep your nose to the grindstone because the majority of experiments one undertakes to study the brain do not work out at all or yield little of significance.

So to keep my nose to the grindstone, I also became involved in research with Charles Gross and George Gerstein, which examined the functions of inferotemporal cortex using single-cell recording methods. One of my jobs was to make the microelectrodes for the recording since I had some experience with this. At that time a great article had come out in Science by Myron Wolbarsht, describing a new platinum-iridium electrode coated with molten glass (Wolbarsht et al., 1960). Not only do these electrodes record well, they are extremely sturdy and can penetrate the dura, making it possible to record neuronal activity in trained, alert monkeys with ease and without discomfort. I learned how to make these electrodes and I still use them extensively to this day. The ones I make, at least in my opinion, are superior to the ones one can buy. Myron is presently a professor of psychology at Duke.

Working with George Gerstein was most instructive. He is a gifted neuroscientist with excellent computer skills. He instituted the poststimulus time histograms which we use to this day to present single-cell recording results.

At the time this work was under way, Charlie was offered a position at Harvard, which he accepted. There he continued the work on inferotemporal cortex that has made a major impact in the field. His autobiography appears in Volume 6 of this series. Charlie, like me, is a canoeist and frequently vacationed on Lake George. This is a beautiful, clear lake in New York State ideally suited for canoeing. It has a great many islands with camp sites. My wife and my children joined Charlie at Lake George on several occasions. I had bought a canoe shortly after working at Camp Timberlake which we took along for these excursions. We also took numerous canoe trips exploring lakes and rivers in New England. On some of these trips we were joined by the people who worked in my laboratory.

For many summers my family and I rented a house on an island called Sutton just off Mount Desert Island in Maine. Quite a few young children vacationed there, and I instituted the Number War game I as described earlier. Charlie Gross joined us there once and we had a great time playing this game. On another occasion David Hubel came for a visit and he too thoroughly enjoyed the game. To the extent that once when he invited me to give a talk at Harvard, most of his introduction consisted of an engaging and funny description of this game.

Another memorable occasion I spent with David Hubel was at a winter conference in Teton Village. He, Marge Livingstone, Ralph Freeman, and I rented a lovely condominium. We did a lot of skiing together and in the evenings had extensive discussions, much of it centering on binocular vision and stereoscopic depth perception, which have been extensively studied by Marge, David, and Ralph. These discussions were one of the early sources of my interest in this area of research which I am still pursuing as described in the next section.

Shortly after I had become an Assistant Professor in the department, Emilio Bizzi came to MIT. We soon got to know each other and began a series of experiments in my laboratory working with alert monkeys. This was a major advance in my training. Emilio had worked at the NIH with Ed Evarts, who had devised techniques to record from behaving, alert monkeys. I soon learned these procedures from Emilio and use them to this day. Ed Evarts was the Chief of the Laboratory of Neurophysiology at the National Institute of Mental Health and in 1974–1975 was president of the Society for Neuroscience. He was always in excellent shape and did a lot of running daily. Quite unexpectedly, Ed died in his office in 1985 from a myocardial infarction. He was just 59 years old.

At the NIH Emilio did recordings in the frontal eye fields of alert monkeys that yielded major new discoveries about the neural mechanisms underlying eye-movement control. In the work we did after he came to MIT, we recorded from the frontal eye fields examining the role of this area in head movements and smooth pursuit eye movements. We found cells specifically involved in both of these motor acts in addition to the cells Emilio had discovered earlier that discharged in association with saccadic eye movements (Bizzi et al., 1970). Emilio went on to a brilliant career. He is a member of the National Academy of Sciences and the President of the American Academy of Arts and Sciences. He was chairman of our department from 1986 to 1998. His autobiography appears in Volume 6 of this series.

In 1964 I became an Assistant Professor at MIT. The first three students who obtained their Ph.D.s in my laboratory were Marylin Smith, Larry Squire, and Michael Stryker. All three carried out independent research in this undertaking.

Research from 1970 until the Present

The research I carried out with Emilio Bizzi opened up the floodgates in my laboratory. In the following six subsections I summarize this body of work, which can also be viewed on our Web site (http://web.mit.edu/bcs/schillerlab/).

The Neural Control of Eye Movements

After the studies Emilio Bizzi and I carried out on the frontal eye field, I wanted to examine the role of various subcortical areas in eye-movement control. The first set of experiments I carried out on my own, recording from single neurons in the oculomotor, trochlear, and abducens nuclei whose axons innervate the eye muscles. This was rewarding work yielding straight forward results, thanks in part to the fact that the extraocular muscles are not segmented; the fibers in each muscle run the entire length of the muscle. Consequently, the activity of a single neuron that innervates a fiber corresponds directly to the movement of the eye. The rate of maintained activity in these neurons defines the positional angular deviation of the eye in orbit. When quantified, this reveals a linear relationship between the neuronal activity and the angular deviation of the eye in orbit. These same cells produce saccadic eye movements by virtue of high-frequency bursts that rapidly contract the muscle; the duration of the burst defines the amplitude of the saccade generated (Schiller, 1970).

While doing this work, David Robinson visited MIT and we were both surprised to learn that he and I were doing highly similar experiments that involved recording in the brainstem oculomotor centers. Our findings were in complete agreement. David suggested that we publish this work concurrently in two different journals, which we did. I have gotten together with David, who has an engineering background, many times since then. David is a brilliant, wonderful individual who has made seminal contributions to our understanding of eye-movement control (Robinson, 1975).

After the work on the brainstem oculomotor centers we moved on to study the superior colliculus. To initiate this work I first developed a surgical procedure to immobilize one eye in monkeys which would allow us to map visual receptive fields and hence establish the relationship between the location of the receptive fields of neurons in the superior colliculus and the physical dimensions of the eye movements that monkeys make with their intact eye. I dissected numerous brains and eventually succeeded in this quest. In the ensuing work we both recorded and electrically stimulated the superior colliculus. I was joined in this effort by Fritz Koerner, Michael Stryker, Sean True, and Julie Sandell. We succeeded in deriving the basic operational characteristics of this structure for the generation of saccadic eye movements (Schiller, 1984; Schiller et al., 1971, 1972). On the basis of our work we concluded that the superior colliculus carries a vector code: When cells in the intermediate and deep layers of the colliculus discharge vigorously, a saccadic eye movement is generated that shifts the center of gaze into the receptive fields of the active neurons. In a similar fashion, electrical stimulation of collicular neurons generates saccades that shift the center of gaze into the receptive fields of the stimulated neurons. What is computed then is the location of the receptive fields of these neurons relative to the fovea. The signal generated is sent down to the brainstem oculomotor centers to produce the desired eye movement that shifts the center of gaze into the receptive field of the activated neurons. Since the visual field is laid out in a neat topographic order in the superior colliculus, different subregions in this structure code different vector saccades. Concurrent work by Wurtz and Goldberg as well as by Robinson were largely in agreement with this view (Robinson, 1972; Wurtz et al., 1971).

An unexpected reward subsequent to the submission of our first paper on the superior colliculus work was an invitation to a conference in Canberra, Australia, that I received, actually before the paper made it to print. This happened because Peter Bishop, who had organized this meeting, had been the referee and was, luckily, impressed by the work. David Hubel, Ann Graybiel, and I joined forces to take this long trip. We were advised to travel with stopovers and decided to visit Tahiti for a few days. There we rented a car and explored the island, taking hikes to scale some of the steep mountains and walking the black sand beaches.

The meeting in Canberra was certainly an august occasion. It began with brief speeches by the prime minister of Australia and the American ambassador. Bob Wurtz and I presented our findings about the collicular control of eye movements. Among the numerous other outstanding presentations, I particularly remember those that dealt with the various classes of retinal ganglion cells initially identified by Enroth-Cugell and Robson and named the X, Y, and W cells (Enroth-Cugell et al., 1966). The extensive research carried out on this topic in Canberra was reported by several investigators (Bishop et al., 1972). This work was of great interest to me, and subsequently I carried out numerous studies examining the parallel channels that originate in the retina as described later.

An interesting aspect of our visit was encountering native Australian animals, such as the kangaroo, koala, wombat, wallaby, and the emu bird. Upon seeing the emu I thought it might be fun to come to Australia for a bit to study emu eye movements. David Hubel and I took numerous photographs during our excursions. On one occasion David, who by the way is also left-handed, spotted a koala sleeping in a tree squeezed between two adjoining branches that had the shape of the letter Y. Subsequently he allowed me to add this picture to a collage of more than 100 neuroscientists, which was published in an article I was asked to write for the 1986 jubilee issue of Vision Research (Schiller, 1986). The task was to describe the advances that had been made during the preceding 25 years in visual neuroscience—which was a lot more than what had been made since the beginning of times until 1960. The inscription to the sleeping koala picture in the paper says: The koala bear, whose visual system has not been studied, suggesting yet another hypothesis for Y cell function. I am not sure that the participants of this symposium much appreciated this flippancy—if they have ever noted it. The original photos from this paper are mounted in the hallway next to my office for everyone to view. Recently I did something on the morbid side: I marked those in the collage who are now dead by attaching small red labels next to their photos. Several people in our department have asked what these labels mean. I find it dismaying that of the 114 individuals whose portraits appear in this collage 16 are now dead; among them are Stephen Kuffler, Robert Rodieck, Gian Poggio, David Marr, Otto Creutzfeldt, Irving Diamond, James Sprague, Richard Young, and Roger Sperry.

Perhaps the most memorable occasion during this visit to Australia arose when David Hubel, Ann Graybiel, and I went to visit an observatory in Canberra. David, like me, had quite an interest in the constellations. In particular, we wanted to get a good view of the Southern Cross. David had made an appointment with one of the astronomers at the observatory. He was a most friendly, kind person who set up two telescopes through which we could view stars and a planet. This astronomer, however, had the worst stutter we had ever encountered. Pointing to one of the telescopes for us to look through, he tried to explain that it was pointing at the planet M . . . M . . . M . . . M . . . Mars. So everything he told us—we had asked about the major constellations in the Southern Hemisphere—took just about forever to get out. Yet this was a remarkable evening that satisfied our curiosity about the Southern Constellations.

After returning from this trip, in the next set of experiments we went on to examine the visual inputs to the superior colliculus by antidromically activating neurons in the retina, by reversibly inactivating area V1 with cooling, and by selectively blocking the midget and parasol systems in the lateral geniculate nucleus. In this effort I was joined by Joseph Malpeli, Carol Colby, Susan Volman, Julie Sandell, Max Cynader, Nancy Berman, Michael Stryker, and Stan Schein. This work established that the direct retinal input to the superior colliculus, which connects to the superficial gray layer of this structure, comes predominantly from small retinal ganglion cells that fall in the category of W cells as initially identified by Enroth-Cugell and Robson (1966). The input from area V1 to the superior colliculus comes from complex cells that reside in layer 5 and are driven exclusively by input from the parasol system, which I will describe in more detail in the next section. We also showed that when area V1 is inactivated, neurons below the superficial gray layer of the superior colliculus can no longer be driven by visual stimuli, indicating that in higher mammals this structure is under the control of the cortex. When tested, even many months after removal of area V1, these cells cannot be activated with visual stimuli (Schiller et al., 1974).

We then proceeded to expand our effort by examining the role of various cortical areas in the generation of saccadic eye movements. In our initial effort to study the cortex we electrically stimulated various regions using microelectrodes to determine from which areas saccadic eye movements can be generated. This work revealed, as did the work of many other investigators, that quite a few cortical areas contribute to eye-movement generation. Notable in our work were areas V1, V2, LIP, the FEF, and the MEF. In this effort I was joined by Edward Tehovnik who has the distinction of having spent the longest time in my laboratory, more than 20 years. Ed was extremely productive during this time period and published more than 40 papers, many of them independently. He made a major contribution to establishing the functional characteristics of the MEF. This structure, unlike most others we had studied in the cortex, carries a place code; electrical stimulation shifts the eye to a particular orbital position and keeps the eye there. Different subregions of this structure shift the eye to different orbital positions. The other areas, V1, V2, LIP, and the FEF, when stimulated, produce saccades similar to those obtained in the superior colliculus; a constant vector saccade is generated, the amplitude and direction of which depends on the subregion stimulated within each area. As in the superior colliculus, in area V1 the stimulation generates a saccade that shifts the center of gaze into the receptive field of the stimulated neurons. Prolonged stimulation in V1, V2, and the FEF produces a staircase of identical saccades (Schiller, 1998).

The next question we posed is how the activity in these cortical areas reaches the brainstem. We discovered that after the superior colliculus has been removed, electrical stimulation still evoked saccadic eye movements from the FEF and MEF, but failed to do so from the posterior cortex, even many months after collicular removal. These findings suggested, as supported by anatomical studies, that the frontal cortex has connections that reach the brainstem oculomotor centers directly (Schiller, 1977, 1998).

We then proceeded to examine what kinds of deficits arise in eyemovement generation when the superior colliculus and various cortical areas are removed. At this time we were also engaged in studying express saccade generation. Initially we were greatly surprised to obtain a bimodal distribution of saccadic latencies when monkeys made eye movements to singly appearing visual targets. I am ashamed to say that I first accused my postdoctoral collaborator at the time, a gifted computer programmer, John Maunsell, of having made a mistake in his program that collected eyemovement records. After a careful examination of his program he assured me that the effect was a real one. Shortly thereafter a paper came out by Fischer and Boch documenting this effect and naming the first phase of the bimodal distribution express saccades (Fischer et al., 1983). This discovery triggered hundreds of experiments. We have also published numerous papers on the topic. As an aside, Fischer once told me that the first time he saw the bimodal distribution of saccadic latencies he too thought it was due to a computer programming error.

Our lesion studies showed that after collicular removal express saccades are eliminated and after FEF lesions monkeys have difficulties in target selection. However, after each of these lesions, as long as they were made bilaterally, monkeys continued to make eye movements quite well, even when tested just 4 or 5 days after the lesions. This was not the case, however, after unilateral collicular lesions, which induce extreme deviations of the eye toward the side of the lesions as well as circling behavior. These deficits persist for many months and have been noted in other studies as well that denoted severe deficits after unilateral brain infarcts (Schiller, 1998; Schiller, et al., 1979, 1980).

The most significant finding in these lesion studies was that after bilateral removal of both the superior colliculi and the frontal eye fields, monkeys became incapable of making visually guided eye movements at all; their eyes appeared fixed in orbit looking straight ahead. We have documented these effects, from which there was practically no recovery, by filming the animals, films I had shown at a great many presentations.

In an elegant set of experiments around this time Wurtz and Hikosaka established that the generation of each eye movement involves a complex interaction between excitatory and inhibitory processes (Hikosaka et al., 1985). They showed that when a GABA agonist is injected into the colliculus, which increases inhibition, monkeys have major difficulties in generating saccadic eye movements with the vectors represented by the affected neurons. Conversely, they showed that when a GABA antagonist was infused, thereby reducing inhibition, the monkeys could not help generating saccades with the vectors represented by the disinhibited neurons. Subsequent work identified some of the complex circuitry involved in the generation of saccadic eye movements (e.g. Schiller et al., 2005). We expanded on this work by carrying out similar experiments in the cortex, showing that in the FEF the effects obtained were just like those in the superior colliculus. We have furthermore shown that infusion of both of these substances into area V1 eliminated the generation of saccades with vectors that would have shifted the center of gaze into the receptive field of the affected neurons (Schiller et al., 2005). We presume this happened because visual processing in area V1 is disrupted by both of these agents.

The upshot of all of these experiments was our proposition that visually guided saccadic eye movements are controlled by two parallel systems, which we called the anterior and the posterior. The posterior system gains access to the brainstem through the superior colliculus and plays a central role in the rapid and accurate execution of saccadic eye movements, whereas the anterior system plays an important role in the process of selecting visual targets in the visual scene to which saccadic eye movements are to be made. Humans make about three saccades per second, some 170,000 saccades a day. With each shift in gaze, a decision has to be made as to where to shift the eye next, except in situations when only single stimulus appears on a homogeneous background, as would be the case when a bird materializes in the blue sky. We carry out most of these calculations without being aware of them.

Further work examining the role of cortical areas in visually guided eye movements has been carried out in my laboratory independently by Jeff Schall. After leaving my laboratory Jeff became a professor in the Department of Psychology at Vanderbilt University, where he continues his outstanding work studying the functions of the frontal lobe.

The Midget and Parasol Systems of the Retina

Two major retinal ganglion systems that originate in the retinae of higher mammals are the midget and parasol. As several studies have established, including the ones Joe Malpeli and I carried out, the midget and parasol retinal ganglion cells project to different sublamina of the lateral geniculate nucleus of the thalamus; the midget cells project into the parvocellular layers and the parasol cells into the magnocellular layers (Schiller et al., 1978). Joe Malpeli came to my laboratory as a postdoctoral fellow in 1974 right after obtaining his Ph.D. at Johns Hopkins. He received his undergraduate degree at MIT in 1967, so joining my laboratory was like coming home. Joe is a most innovative individual with outstanding manual skills. He created several types of hardware for our work, including a metal-coated glass microelectrode that could be used to both record and inject various pharmacological agents into various brain regions (Malpeli et al., 1979). We used these electrodes in several experiments in our efforts to learn about the functions of the midget and parasol systems. Joe Malpeli and I were joined by several other students and collaborators in this effort. They included Carol Colby, Stan Schein, John Maunsell, Eliot Charles, and Nikos Logothetis.

In the first set of experiments we set out to determine the extent to which inputs to area V1 from the midget and parasol systems remain separate or converge on single cells. To accomplish this, thanks to Joe Malpeli’s skills, we reversibly inactivated either the midget system or the parasol system while recording from individual neurons in area V1. The inactivation was achieved predominantly by infusing lidocaine into either the parvocellular layers or magnocellular layers of the lateral geniculate nucleus (LGN), thereby blocking the input to V1 from either the midget or parasol systems. This was difficult and time-consuming work as it required us to place our electrodes in the LGN and in area V1 at sites where the neurons in these two areas had overlapping receptive fields, thereby assuring us that the small injections in the LGN affected those cells that connected with the cortical neurons we were studying. The results obtained with this work showed that more than 30% of V1 cells receive convergent input from the midget and parasol systems. However, as already noted, the layer V complex cells that project to the superior colliculus are driven exclusively by the parasol system. Subsequently John Maunsell’s group examined the projections of the midget and parasol systems to areas V4 and MT and showed in an elegant series of studies that area MT is driven predominantly by the parasol system, whereas V4 receives input from both systems (Ferrera et al., 1992; Maunsell et al., 1990).

We next turned to the question of what the functions are of the midget and parasol systems. To answer this question, we carried out a long series of experiments in which we used psychophysical procedures to assess several visual functions after either the midget or parasol systems had been blocked as a result of small lesions made in the magnocellular or parvocellular layers of the LGN. These experiments revealed that the midget system processes color, fine pattern detail, and stereopsis, whereas the parasol system plays a central role in the processing of motion and motion parallax for depth perception. The conclusion we came to is that these two systems have emerged in the course of evolution to extend the range of vision, with the midget system extending it into the high spatial frequency domain and in wavelength analysis for color vision, and the parasol system extending it into the high temporal frequency domain (Schiller, 1993; Schiller et al., 1990).

Our ability to carry out this work was greatly aided by developing a set of computerized systems to collect quantitative data using randomized sequences of stimulus presentations. In the initial work, the computer programs were created by Andreas Polit and Sean True using a PDP 11/20 computer. Visual stimuli were presented first using optic benches I had put together with stepping motors that allowed randomized presentations of bar orientations and lengths, directions of movement, and varied spatial frequency gratings that could be moved across the receptive fields of neurons in recording experiments. Subsequently we used color monitors whose resolution to this day does not come close to the resolution one can get with optic benches.

The new computer system was then used in several experiments. With Susan Volman and Barbara Finlay, we made a detailed quantitative study of neurons in area V1 following in the footsteps of Hubel and Wiesel. We did this work during the time we examined the cortico-tectal projections. When we started that work and identified the cortical neurons that projected their axons to the colliculus, we did not realize how low the probability was of finding such neurons using antidromic stimulation methods. As we were advancing the electrodes in the cortex, we kept obtaining beautiful responses from one neuron after another; having such a neat system to study the receptive field organization of neurons, we could not resist examining every well-isolated cell. We ended up obtaining detailed data from more than 200 cells, 45 of which projected to the superior colliculus. Our quantitative work confirmed Hubel and Wiesel’s remarkable discovery of the simple and complex cells in V1. We furthermore identified several subclasses of simple cells, some of which received input only from the ON system, some from the OFF system, and some from both. The ON and OFF systems will be discussed in the next section. We found that virtually all simple cells were directionally selective. The majority of complex cells were also direction selective. What we failed to show, however, is that the third category of cells Hubel and Wiesel had identified, the hypercomplex cells, form a separate, distinct category. The prime definition of these cells was that they are “end-stopped,” which meant that they responded much more vigorously to short bars presented in their receptive fields than to long bars. Quantitative analysis of the length tuning curves we obtained revealed that the degree of end stopping varies over a broad range in both simple and complex cells, indicating thereby that the attribute of end-stopping does not yield a distinct third population of cells in area V1.

We published our findings on this recording work in area V1 in five successive papers in the Journal of Neurophysiology in 1976. Shortly after it was published I received a letter from Vernon Mountcastle in which he complimented us profusely, especially for the quantitative methods we had used. He went on, however, to point out two errors in the figure legends—there were a total of 75 figures with legends in the five papers—errors which no one, including of course myself, had previously spotted. What a scholar! Vernon Mountcastle’s autobiography appears in Volume 6 of this series.

A second line of work utilizing our computer system constituted Michael Stryker and Helen Sherk’s thesis at this time. They decided to examine quantitatively the claim made by Colin Blakemore that in kittens that had been reared in a restricted environment during the first 3 months of their lives, by exposing them daily to either only horizontal or vertical gratings, most neurons acquired the orientation specificity corresponding to the conditions under which they had been raised. The data Helen and Michael collected were carried out without them knowing how the animal had been reared. Each cell’s orientation selectivity tuning was obtained with the automated computer system (Stryker et al., 1975). This work, which created quite a stir at the time, failed to replicate the initial findings by Blakemore and Van Sluyters (1974). On the lighter side, when Michael Stryker presented these findings at a neuroscience meeting, he wore a custom-made striped shirt that had vertical stripes in front and horizontal stripes in the back.

A significant additional fact that arose pertaining to this work came about when Helen Sherk had the idea of determining just how the stripes on the walls of the circular chamber, in which the kittens were placed daily, impinged on the retina. She did this by taking photographs from the cat’s eye point of view. This revealed something quite unexpected. The projections of both the horizontal and vertical stripes formed many different orientations on the retinal surface. So no wonder that in area V1 of these animals neurons with many different orientations were found. On the whole, however, the orientation tuning properties of cells in these specially reared cats were not nearly as sharp as in normally reared animals.

In 1977 a major disaster struck our department at MIT. While Hans-Lukas Teuber was vacationing with his wife, Marianne, in the British Virgin Islands, they took a swim and the strong tide there swept Lukas out to sea. In his effort to swim back, he became exhausted and had a fatal heart attack. He was just 60 years old. Dick Held took over ably as the Department Chair, a position he held until 1986 at which time Emilio Bizzi took over followed by our present chairman, Mriganka Sur in 1998. Since its inception in 1961, our department has grown by leaps and bounds. We now have 47 faculty members, 95 graduate students, and 180 postdocs and research investigators. The department, since its inception, has awarded 329 Ph.D. degrees. Eight of our faculty have been inducted into the National Academy of Sciences: Edward Adelson, Emilio Bizzi, Robert Desimone, Ann Graybiel, Richard Held, Nancy Kanwisher, Susumu Tonegawa, and myself. A more detailed description of our department is provided on our Web site (http://bcs.mit.edu). The autobiographies of Richard Held and Emilio Bizzi appear in Volume 6 of this series.

The ON and OFF Channels of the Retina

As a result of the work on the midget and parasol systems, we developed a strong interest in the retina, especially in the origin and functions of the ON and OFF systems as well as the midget and parasol systems.

The basic response characteristics of the retinal ganglion cells were first established by Haldan Keffer Hartline who had recorded from isolated retinal ganglion cell axons and studied their characteristics by shining beams of light into the eye (Hartline, 1938). He found that some cells responded when the light was turned on, some when the light was turned off, and some responded to both events. He called them the ON, OFF, and ON/OFF cells, names used to this day. He received the Nobel Prize for this work in 1967. The initial idea that has emerged from this work was that the function of the ON and OFF cells was to signal, respectively, the appearance and the termination of a visual stimulus. Subsequently several different hypotheses have been advanced as to why there are ON and OFF ganglion cells in living organisms. Two subsequent discoveries played a central role in the formulation of these hypotheses. The first, largely attributable to Kuffler, was that retinal ganglion cells, as well as cells in the lateral geniculate nucleus, have antagonistic center/surround organization; small spots of light presented in the center of the receptive fields of neurons—the small region in the visual field to which these cells responded—produced vigorous responses, whereas large spots barely activated the cell (Kuffler, 1953). The second set of discoveries was made by Hubel and Wiesel, which showed that in the visual cortex neurons are selective to the orientation of edges and to the direction of motion of visual stimuli (Hubel et al., 2005). Hubel and Wiesel received the Nobel Prize in 1981 for their remarkable discoveries. Taking all of these new findings into account, theories have been advanced proposing that the ON and OFF systems originating in the retina evolved to produce the center/surround organization in these cells and to produce orientation and direction selectivities in the cortex.

One of the central features of visual processing is to analyze information in the visual scene based both on the perception of lightness and darkness. Due to the composition of their surfaces, some objects absorb light and some reflect it and typically do so selectively for different wavelengths, thereby giving rise to the perception of color. Living organisms need to and are capable of processing information based on both increases and decreases in the number of photons that enter the eye. Consequently, another idea about the ON and OFF systems has been that they emerged in the course of evolution so that both light increment and decrement could be processed rapidly in the visual system (Schiller, 1995).

Critical examination of these ideas became possible when several additional discoveries had been made about the workings of the retina. Werblin and Dowling developed procedures that enabled them to record intracellularly in the retina (Werblin et al., 1969). This work, carried out in the mudpuppy (Necturus maculosus), yielded remarkable and unexpected discoveries. Werblin and Dowling found that all photoreceptors hyperpolarize to light. The neurotransmitter of all photoreceptors is glutamate as has been established in several laboratories. The ON and OFF systems arise at the level of the bipolar cells. The ON and OFF bipolar cells have different neurotransmitter receptor sites. Those of the OFF bipolars are sign conserving and therefore respond in a similar fashion to the incoming light as do the photoreceptors. The ON bipolars on the other hand have a unique metabotropic receptor mGluR6 that inverts the incoming signal from the photoreceptors. Thus, in the course of evolution a double-ended system has been created from the single-ended one seen in the photoreceptors, thereby creating a situation that makes it possible to send excitatory signals into the central nervous system for both light incremental and light decremental information. Dowling and Werblin also established that the photoreceptors, horizontal cells, and bipolar cells only generate graded potentials. Action potentials are produced in all ganglion cells and in some of the amacrine cells. As a result of these remarkable achievements, Dowling was inducted into the National Academy of Sciences, which now has about 2500 elected members from all sciences, with about 50 in section 28 named Systems Neuroscience. Dowling’s autobiography appears in Volume 4 of this series.

In 1981 a remarkable paper was published in Science by Slaughter and Miller, who also carried out their work in the mudpuppy. They applied a glutamate neurotransmitter analog, 2-amino-4-phonobutyrate (APB) to the retina, which had been created by Watkins and Evans in England, and found that it silenced the ON system by blocking the responses of the ON bipolar cells (Slaughter et al., 1981). The OFF system was unaffected. This work opened up the floodgates for carrying out research aimed at determining why the ON and OFF systems have emerged in the course of evolution.

I became greatly interested in this work and began an extensive series of experiments to study the ON and OFF channels of the visual system. As a first step in this effort I wanted to determine whether the discoveries made by Slaughter and Miller also apply to mammals. To accomplish this we proceeded to develop methods that enabled us to infuse APB into the eye of monkeys while recording in the lateral geniculate nucleus and various cortical areas.

I carried out this work in collaboration with several students in my laboratory who included Michael Stryker, John Maunsell and Julie Sandell, Andrew Knapp, and Robert Dolan. Our procedures took awhile to develop. We decided to infuse solutions into the eye through a fine tube and also placed a larger tube at a lower location that allowed the infused solution to escape from the eye. Well, when we first did this, due to the viscosity of the vitreous, the solution could not escape from the eye, thereby increasing the intraocular pressure to a level that terminated the activity of neurons in the retina. We then tried several procedures to overcome this problem. One was to apply hyaluronic acid that breaks up and liquefies the vitreous. This worked, but it caused some mild discoloration. So instead, we turned to a method that sounds terrible but has been commonly used by ophthalmologists. We used the equivalent of an eggbeater, a miniature one, that could be inserted into the vitreous through the larger tube. Twirling it around gently broke up the vitreous effectively without causing any discoloration or damage to the retina. So we ended up using this procedure but then ran into another unexpected problem. Once we started to infuse saline into the eye, thinking it was the appropriate control solution, the neurons again became unresponsive in short order. Looking into this problem, we learned that the composition of the vitreous is complex and that one needs to create a solution which has electrolytes akin to those in the vitreous. Fortunately, Cunningham and Miller (1976) created a perfusate that is similar in composition to the vitreous. Once we had succeeded in concocting this rather complex solution to be appropriate for the monkey, we had a major success: infusion of this substance into the eye did not alter the responses of neurons when their receptive fields were stimulated with light spots. We were then able, through another container, to infuse this solution with APB added and to then wash it out subsequently. Thereby we could assess neuronal responses before, during, and after the administration of APB.

This work has established several facts: First, the ON cells in the LGN were silenced in the monkey when low concentrations of APB were infused into the eye; OFF cells were largely unaffected, showing that the neurotransmitter system is similar in the monkey to that seen in the mudpuppy. Second, we found that while ON-center cells in the LGN were totally silenced by the APB, the responses and the center-surround organization of OFF cells was unaffected. Thirdly, in the cortex cells that normally respond to both light increment and light decrement stopped responding to light edges when APB was infused into the eye without affecting the responses made to dark edges. Fourth, the orientation, direction, and spatial frequency selectivity of cortical cells was unaffected by the APB infusion. These findings established that the ON and OFF systems did not arise for the purpose of creating center/surround organization in the retinal ganglion cells and the lateral geniculate nucleus and also did not arise for the purpose of creating orientation, direction, and spatial-frequency selectivity in the cortex.

We then proceeded to examine how visual perception is affected by the selective blocking of the ON system. We did this in monkeys trained to make a variety of visual discriminations. In this phase of the work APB was injected into the eye with a fine-gauge hypodermic needle while the animal was briefly anesthetized. This effectively blocked the ON system in the injected eye for a few hours. The prime effect of blocking the ON system using this procedure was that monkeys had difficulties detecting light increment, such as a light spot on a gray background, but did not have any problem detecting light decremental cues such as a dark spot on the same background. Furthermore, any residual response made to light incremental stimuli had very long latencies.

These findings pertain to conditions under daylight viewing when the cone photoreceptors are operative. The rod photoreceptors that process information under dark-adapted conditions are organized in a different fashion. In monkeys and in other primates there are only depolarizing rod bipolars as had been established in several studies, including one I had carried out in collaboration with Robert Dolan who obtained his Ph.D. working in my lab in 1992 (Dolan et al., 1989; Wassle et al., 1991). The rod bipolars, like the ON cone bipolars, have mGluR6 neurotransmitter receptor sites whose responses to light are blocked by APB. We showed that monkeys lose the ability to process any visual information under dark adapted conditions after APB is infused into the eye; in other words the monkeys became night blind. All effects produced by APB infusion into the retina with these procedures were temporary. After the APB was broken down by natural processes in the retina, normal vision returned.

Our studies using APB led to the affirmation of the following inferences: In the course of evolution a double-ended system emerged from the single ended system of the cone photoreceptors by creating the mGluR6 neurotransmitter receptors in ON bipolar cells, which makes it possible to process both light incremental and light decremental information in the retina rapidly and effectively. Objects in the visual scene reflect some wavelengths and absorb others. Consequently, as we move our eyes about, we perceive objects in the visual scene by virtue of either increases or decreases in the number of photons entering the eye. Thus, a fish in the ocean can respond rapidly both to a predator that swoops up from below and is lit up by the reflection of the incoming sunlight from its body and to a dark bird in the sky, like an osprey, that is about to swoop down to catch the fish. Thus, light incremental and light decremental information can be effectively and rapidly processed by virtue of the ON and OFF systems in diurnal animals. This can also be readily seen in humans; we can effectively read dark letters on a white background as well as light letters on a dark background. The former is much more common, of course, as it is a lot cheaper to produce books and newspapers with black letters on white paper rather than the other way around. So when we read books, magazines, and newspapers, the OFF system does most of the work. An overview of these findings is published in Progress in Retinal and Eye Research, Volume 15 (Schiller, 1995).

Andy Knapp, who was then a graduate student working in my lab and had participated in some of this work, went on to carry out an independent set of experiments with APB. In a set of elegant studies it was established that there is yet another type of ganglion cells in the retina, the directionally selective cells of Dogiel that project into the accessory optic system. These cells, in concert with the vestibular system, play a central role in stabilizing the retina with respect to the visual scene to prevent blurring when the body or the visual scene is in motion. These cells play a central role in the generation of optokinetic nystagmus that can be seen when a grating is moved across the visual field, resulting in pursuit eye movements interrupted by resetting saccadic eye movements. Simpson and his collaborators discovered that in the rabbit these cells receive input only from ON bipolar cells (Simpson et al., 1979). What Andy Knapp then showed is that when APB was infused into the eye to block the responses of these cells, the optokinetic response was eliminated. Similar work in monkeys, however, did not create this deficit, suggesting that in this species the cells of Dogiel receive input from both the ON and OFF systems (Knapp et al., 1984).

Julie Sandell, who had also participated in several of our studies, went on to carry out an entirely independent project for her Ph.D. thesis. Her work examined the distribution of NADPH diaphorase in the rat brain. This thesis has the distinction of being the longest among the ones that have come from my laboratory, 97 pages.

Studies of Extrastriate Cortex

In the 1980s we began yet another series of experiments examining the functions of area V4 in the monkey. Thanks to a remarkable group of collaborators, we have made considerable progress in this quest. The investigators who have taken a major role in this effort, which has also produced several Ph.D. theses, included Paul Haenny, Karl Zipser, Kyoungmin Lee, Victor Lamme, John Maunsell, Andreas Tolias, Eliot Charles, Nikos Logothetis, Rufin Vogels, and Yoshihisa Osada. This work was carried out on two fronts: single-cell recordings and lesion studies examining the effects of removing areas V4 and MT on visual processing. In agreement with the outstanding work in Bob Desimone’s laboratory, at that time at the NIH and who now is the head of the McGovern Institute here at MIT, this work established that area V4 is far more complex than had been thought (Moran and Desimone, 1985). Before these studies it was believed that area V4 specializes in the processing of wavelength information for color vision (Zeki, 1980).

The single-cell recording studies we and Desimone’s lab carried out revealed that area V4 processes several dynamic aspects of visual information processing (Desimone and Schein, 1987; Moran and Desimone, 1985). Most likely, because of extensive interconnections with other cortical areas, the activity of neurons in V4 is greatly influenced by the decision processes made in stimulus selection and in pattern analysis. When monkeys are trained to either ignore or pay attention to the same visual stimulus, V4 neurons respond quite differently. Furthermore, the responses of neurons are modulated by contextual stimuli that impinge in regions outside their classically defined receptive fields as well as by the eye movements monkeys make (Haenny et al., 1988; Schiller et al., 1991; Tolias et al., 2001).

Our psychophysical studies showed that when area V4 is removed, relatively minor deficits occur in color vision, but a major deficit arises in the ability of monkeys to select target stimuli in the visual scene that are smaller or have less contrast than the other stimuli with which they appear. One of the tasks in vision is to be able to ferret out subtle stimuli in the visual scene, as is especially important in the animal kingdom in defeating camouflage. It appears that area V4 plays a central role in this process.

In one set of related experiments we also examined how visual processing is affected in monkeys by the removal of both areas V4 and MT. We were surprised to find that many basic visual capacities, such as perception of color, shape, motion, and stereoscopic depth were only moderately compromised. This suggested to us that area V1 sends projections to several areas in addition to V4 and MT, areas which are also involved in multiple aspects of visual processing (Schiller, 1993).

After working on these projects, most of the collaborators in my lab moved on to fine careers. Yoshihisa Osada, who was a visiting professor, returned to Japan, where he runs a busy laboratory at Rikkyo University. He invited me twice to meetings there and was a most gracious host. I stayed with him and he took me to visit many interesting sites in Japan, including the Japanese Alps, where we took a wonderful hike. Paul Haenny returned to Switzerland to his medical practice. He also was a gracious host when I visited him once and I stayed at his home. After Nikos Logothetis moved to the Max Planck, as already noted, I visited him several times as we continued our collaborations. John Maunsell is now an eminent professor at the Harvard Medical School, where he runs a busy laboratory; we meet up occasionally.

Visual Prosthetics

Largely as a result of the extensive electrical stimulation work Ed Tehovnik carried out in my laboratory (Tehovnik et al., 2009), we moved on recently to examine the feasibility of creating a prosthetic device for the blind based on electrical stimulation of area V1. We have published an article entitled “Visual Prosthesis,” in which we advocate that this is kind of work be carried out in animals as had been done in the highly successful creation of the cochlear implant (Schiller et al., 2008). We were both surprised and delighted that this paper has created considerable interest and controversy.

Depth Work

Some years ago, as a result of discussions with David Hubel, Marge Livingstone, Ralph Freeman, Bela Julesz, Gian Poggio, and several other investigators, I became interested in several aspects of depth processing and carried out quite a few experiments on the topic. Part of this work has examined which brain areas are involved in the processing of various depth cues and where the information provided by these cues is integrated. We have studied stereopsis, motion parallax, and shading. In this effort, recording work, which constituted the Ph.D. thesis of An Cao, showed that already in area V1 there are neurons that process information about differential velocity which provides the essential motion parallax information for depth (Cao and Schiller, 2003).

Recently we devised a display system based on the Bela Julesz randomdot stereograms that allows us to present disparity, shading, and differential velocity cues for motion parallax separately and in various combinations.

A new direction that has emerged from this effort is the examination of brain organization in normal, stereo-deficient and stereo-blind humans with various etiologies using functional magnetic resonance imaging. Stereodeficient and stereo-blind individuals comprise 5% to 10% of the population in the United States. I am aided in this ongoing effort by a team of collaborators that includes Steve Shannon, Geoffrey Kendall, Michelle Kwak, Nikos Logothetis, Johannes Haushofer, and Warren Slocum. Warren has been working in my laboratory since 1991. Since that time he has written most of the computer programs we use in our research and has done extensive data analysis. He is coauthor on many of our published research articles (Tehovnik, et al., 2009).

Collaborators

In my research career I have had more than 50 students, postdoctoral fellows, and associates join my laboratory, which has produced 21 Ph.D. theses and publications with 62 different coauthors. I have been most fortunate in attracting so many remarkable and brilliant individuals. Many of them have gone on to outstanding careers in neuroscience. I am proud of the fact that three of them have been elected into the National Academy of Sciences and into the American Academy of Arts and Sciences: Larry Squire, Nikos Logothetis, and Michael Stryker. Nikos, after leaving my laboratory, moved to the Max Planck Institute in Tübingen, Germany, where he created one of the largest neuroscience labs in the world and became one of the most outstanding experts in functional magnetic resonance imaging research. Larry is now a professor of psychiatry, neurosciences, and psychology at the University of California, San Diego, where he has done outstanding work examining learning and memory; he was president of the of the Society for Neuroscience in 1993–1994. Michael is now at the University of California, San Francisco, where he served as department chair of the Physiology Department from 1994 to 2005.

Here I now provide an alphabetical list of those who have worked in my laboratory over the 49 years of its existence. The asterisks denote those who earned their Ph.D.s based on the research carried out in my laboratory. Much of the Ph.D. work, as stipulated, was carried out independently by these students as reflected in the fact that on many of the ensuing publications I do not appear as a coauthor.

Karl Arrington

Geoffrey Kendall

Jacob Richter

*Nancy Berman

Jennifer Kendall

*Julie Sandell

*An Cao

*Andrew Knapp

Jeffrey Schall

Christina Carvey

Fritz Koerner

Stan Schein

*Eliot Charles

*Michael Kuperstein

*Helen Sherk

*Ron Chase

Michelle Kwak

Warren Slocum

*I-han Chou

Victor Lamme

Stelios Smirnakis

*Carol Colby

*Kyoungmin Lee

*Marylin Smith

*Janet Conway

Tai Sing Lee

*Marc Sommer

Denice Couch-Helwig

Audie Leventhal

*Larry Squire

*Max Cynader

Nikos Logothetis

Renata Stebbins

*Robert Dolan

Joe Malpeli

*Michael Stryker

Barbara Finlay

Scott Mann

Edward Tehovnik

Alan Greenfield

John Maunsell

Robert Thau

Paul Haenny

Jamie Mazer

*Andreas Tolias

Johannes Haushofer

Robert.M. McPeek

Sean True

Shaul Hochstein

Tirin Moore

Rufin Vogels

Anya Hurlbert

Marilee Ogren

Veronica Weiner

*Ron Kalil

Yoshihisa Osada

Ying Zhang

*Karl Zipser

Family

While I was in graduate school at Clark University in Worcester, Massachusetts, my wife Ann worked at the Worcester State Hospital assisting a psychiatrist in research. After we moved to Cambridge, Massachusetts, upon my becoming a postdoctoral fellow, she secured a job with Hans-Lukas Teuber that involved testing patients with brain injuries, mostly at the Boston VA hospital. Ann was an English major at Duke University with excellent writing skills. In the 1970s she became interested in the history of architecture, which has resulted in her writing a biography about Charles F. McKim, who was the head of the architectural firm McKim, Mead, and White; at the turn of the 19th and 20th centuries, this was the largest architectural firm in the world. In the Boston area they are perhaps best known for building Boston Symphony Hall and the Boston Public Library. Ann’s biography is a scholarly piece of work that comes to 411 pages, but it never got published because in 1999 she died of leukemia.

We have three children, David, Kyle, and Sarah. Ann was a devoted mother who took prime responsibility raising the kids. She stopped working to spend all her time raising them. The kids were trained in sports from an early age. David became a fine swimmer, skier, and lacrosse player, to the extent that after college he played professional lacrosse in Australia for a year and then spent one winter as a ski instructor. All three kids earned MBA degrees. David is now employed by Blackrock and Kyle is Director of Business Management for the GEO Group, Inc. Kyle is a gifted guitarist and plays professionally with a band he has put together. My daughter Sarah took on an entirely different line of work; she is now employed by a radio station in Philadelphia, where she has a daily radio show.

I now have five grandchildren ranging in age from 4 to 21. David and his wife Michelle have two young girls, Madeline and Chloe; Kyle and his wife Gaby have three children, Andrea, Monica, and Nicole. The oldest, Andrea, is a junior at Princeton.

I still have family in Hungary and we have been in contact with each other on quite a few occasions. Because of the Cold War and the Iron Curtain, after immigrating to the United States in 1948, I did not return for a visit to Budapest until 1968. Although we had kept in contact by mail, I had not laid eyes on my mother during these 20 intervening years, so it was quite an experience to meet up with her. We talked endlessly and soon closed this great time gap. Most recently, I visited in Budapest when I was asked to give a presentation in honor of being inducted into the Hungarian Academy of Sciences. I stayed with my cousin Paul Rudas, who runs a computer company. They now spend much of their time in England where his wife, Klara Breuer-Rudas is Deputy Head of Mission at the Hungarian Embassy in London. Their young son, who is attending school there, has become quite the Englishman.

On another occasion, some years ago, after Michael Stryker and I had attended a conference in Turkey, we visited in Budapest and spent a memorable evening with my family at the house of Paul Rudas’ twin brother, Peter. His wife, Márti, has made an extensive study of Hungarian folk music and has written about it. We spent much of the evening singing Hungarian folk songs. Sadly, a few years ago my cousin Peter Rudas died in a car accident. Their two children, Anna and Klári, are about to earn their Ph.D. degrees.

My cousin Andrea, about whom I wrote at the beginning of this chapter, still lives in Beirut, Lebanon. I have not seen her in several years because she does not like to travel and because I have not had the opportunity to go to Beirut.

Hobbies

I pursue several hobbies. I have learned to play a number of musical instruments, none of them well. First the piano, then the recorder that is well suited for playing Hungarian folk songs, the guitar, and lastly the banjo, which in spite of a great many hours of effort I have never managed to play even half decently. Initially, my piano playing centered on classical music and involved memorizing most of Bach’s two- and three-part inventions and Béla Bartók’s folk songs. Later on in life I have turned to improvisations and put together several medleys in which, intermingled with well-known folk tunes and popular melodies, I play some of my own compositions.

After coming to the United States, another hobby I pursued for a while was to translate Hungarian short stories. I remember one of these in particular by the great satirist Karinthy Frigyes. In this short story, entitled “Barabbas,” the crowd at the Passover feast that has chosen to commute the death sentence of Barabbas is given a second chance. Each individual now vehemently screams, “Jesus, Jesus, Jesus.” But the collective sound Pontius Pilate hears through the airwaves is, “Barabbas, Barabbas, Barabbas.” So Jesus is crucified again.

These translations inspired me to write short stories which are based largely on my life experiences. I have written many of them, and each starts with a full-page abstract drawing relevant to the story with the title in the center. At this stage these are private and few people have read them. Perhaps one of these days I will have the temerity to put them together into a book. In one of these stories a grandmother becomes victim of a bombing raid during World War II. Her body is found by her grandson after a long search by recognizing the Triskelion pendant on the neck of her decomposed body. The grandson carts her home and with his grandfather buries her in a full-sized coffin they constructed from dining room furniture at a time when due to short wood supply most of the dead were buried in foreshortened coffins. The initial page is a drawing which in the center has the title, The Pendant with the Triskelion and a full-sized coffin below. Surrounding this display is an array of foreshortened coffins as described in the War Years section of this chapter.

Another hobby I actively pursue now is artwork that has several forms. I make sculptures, suncatchers, a variety of hangings, abstract pictures generated on the computer, and photographs. I have created several hundreds of them. My office area and my home are overwhelmed by these productions. Recently, with the help of Christina Carvey, we have created a new Web site on which some of my artwork can be viewed (www.richfieldstudios.com).

At this time in my life, undeniably, retirement is looming on the horizon. When I reach that stage and if still healthy, I will continue my busy existence. I have a contract to write a book on Vision and the Visual System, which I shall start working on at that time. I also plan to spend more time with my hobbies. After retiring, I will most likely have to sell my house in Newton, MA, where I now live and move into a retirement home—one that has a well-equipped shop. When I get to this point, I can only hope that my friend from our Duke days, Hooksie, was right: “There’s friends everywhere.”

Selected Bibliography

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Gordon M. Shepherd

BORN:

Ames, Iowa

July 21, 1933

EDUCATION:

Iowa State College, B.S., 1955

Harvard Medical School, M.D., 1959

Oxford University, D.Phil., 1962

APPOINTMENTS:

National Institutes of Health, Office of Mathematical Research: Surgeon, U.S. Public Health Service (Biophysics) (1962)

Karolinska Institute, Stockholm, Physiology Department II: Visiting Scientist, Special Fellow, U.S.P.H.S. (1964)

Retina Foundation, Boston: Research Associate (1966)

Massachusetts Institute of Technology, Biology Department: Research Associate (1967)

Yale University School of Medicine, Physiology Department (1967–1978): Assistant Professor, Associate Professor

Neurobiology Department (1978–present): Professor

Yale University, Deputy Provost for Biomedical Sciences (1991–1995)

Visiting Appointments: University of Pennsylvania, Visiting Scientist, Neurology Institute (1971–1972); Collège de France, Paris, Visiting Professor and Lecturer (1986); Oxford University, Astor Visiting Lecturer (2009)

HONORS AND AWARDS (SELECTED):

Association for Chemoreception Sciences (AChemS). Chairperson (1981)

Javits Award, National Institute of Deafness and Other Communicative Disorders (1985–1992)

R.H. Wright Award in Olfactory Research, Simon Fraser University (1987)

Stanley K. Freeman Award, Association for Chemoreception Sciences (AChemS) (1988)

Journal of Neurophysiology (Editor-in-Chief) (1989–1995)

Journal of Neuroscience (Editor-in-Chief) (1999–2003)

Honorary degrees, University of Copenhagen (1999); University of Pavia (2006)

Member, American Academy of Arts and Sciences (2006)

Fellow, American Association for the Advancement of Science (2008)

President, Cajal Club (2008–2010)

Gordon M. Shepherd has carried out fundamental studies of the integrative properties of dendrites, dendritic spines, and synaptic microcircuits, using the olfactory bulb as a model system. His contributions include the first physiologically based circuit diagram of a brain region; electrophysiological analysis and computational prediction with Wilfrid Rall of dendrodendritic synaptic interactions for feedback and lateral inhibition; discovery of the representation of odors by spatial activity patterns in the olfactory glomerular layer; and databases and neuroinformatics tools for dendritic properties, computational neuronal models, and brain microcircuits. Among his books are The Synaptic Organization of the Brain (5th ed.), Neurobiology (3rd ed.), Foundations of the Neuron Doctrine, Creating Modern Neuroscience, and Handbook of Brain Microcircuits.

Gordon M. Shepherd

I was born “at the bottom of the Depression,” as we used to say with a certain amount of pride. My generation was the last to have childhood memories of those years, so harsh for so many, though muted for a child growing up in a middle-class academic family in a small midwestern college town. The economic recovery followed by World War II in the early 1940s instilled in us a belief that we could overcome adversity, together with a belief in progress.

My father, Geoffrey Shepherd, had immigrated in 1908 as a boy to Canada with his family, settling on a ranch, West Plains, in southwestern Saskatchewan just over the border from Montana. His father and brother survived their first winter in a sod hut, so in that real sense I come from pioneer stock. He raised us on stories of the “pioneer spirit,” of their survival in the hardscrabble landscape and harsh climate of the northwest plains, where hot summers brought their plague of drought and grasshoppers, and bitter winters required feeding the cattle at forty degrees below zero. There was a quiet heroism about it, a grandeur of the vast and open plains, that exerted its pull on me from his stories and our visits there. Wrenching himself from his family and the ranch, he earned a college education and followed a friend to Ames, Iowa, to become a graduate student at Iowa State College in agricultural economics, one of the premier programs in the country.

My mother was Eleanor Murray, a third-generation Scot in the United States, who grew up in Cedar Rapids, Iowa, went to Coe College, and worked for several years as an editor in the U.S. State Department in Washington. She was a sister of Bill Murray, one of father’s graduate school roommates at Iowa State. She and father married in 1931. I thus had both an immigrant’s and a native born citizen’s view of life in these United States.

Despite the Depression, in 1935, as a young faculty member at Iowa State, father took us on a study tour to Europe for several months. I was later entertained as a child by stories of the adventures of a 2-year-old in Paris, Copenhagen, Norway, and the United Kingdom. It must have planted some internationalist engrams in my young brain.

In 1938 my parents built a new house on Oakland Street near the college. This wooded street was a remarkable neighborhood, with a mixture of academics and townsfolk. For me it was the best possible place to grow up, giving one a sense of the value of learning, together with a sense of common human values. Iowa State at midcentury was an extraordinary institution.

Despite having a “cow-college” image, its academic standards were high and its faculty was world class. Our neighbors and friends included Henry Gilman in chemistry (NAS, FRS), Jay Lush in animal genetics (NAS), Frank Spedding in atomic physics (NAS), and George Snedecor, whose textbook on statistics was a best-seller worldwide. A few blocks away was Paul Errington, one of the country’s leading naturalists. The chair of father’s department was Ted Schultz, later a Nobel Prize winner in Economics. Rainer Schickele, the future PDQ Bach’s father, was also in economics; Ken Boulding, future president of AAAS, was in sociology. Uncle Bill later twice ran for governor and founded Living History Farms. Christian Petersen was the sculptor-in-residence at the college. My parents gave me art lessons from Velma Rayness, a regional painter.

Perhaps most intriguingly (though we didn’t know it at the time), the digital computer was invented by one of our neighbors. In a court case in the 1970s, it was determined that around 1940, John Atanasoff, then a member of the Iowa State physics faculty, had invented the first digital computer, whose working principles were used, though without acknowledgement at the time, for the subsequent building of the ENIAC. Although only 7 at the time, I remember seeing him and his family outside their house during my roamings about the neighborhood.

In 1941–1942 we lived in Washington, D.C., while father was recruited into the planning for agricultural price controls for the inevitable war. On December 7, 1941, we were a witness to history. Out for an afternoon drive, we went by the old State Department Building (now the Executive Office Annex) where mother had worked. In addition to roses blooming in December, we saw a knot of people by a side door with several black limousines parked nearby. People there said that Japanese ambassadors were meeting inside with Secretary of State Cordell Hull; something bad had happened at Pearl Harbor in Hawaii. Soon the ambassadors hustled out to their cars; I snapped a photo with my box camera; World War II was about to start.

Because of the Depression and the war, our life in Ames centered very much on the neighborhood. I was lucky to have good buddies to play with. In this connection I was intrigued to read David Hubel’s memoir about his own childhood, in which he related how children of modest means of that era were left to their own devices for play and projects. That was certainly true for us: days were filled with backyard sports, card games, reading the comics, listening to the radio, palling around. We played our part in the war effort by engaging in pitched battles with mud balls as grenades in the back ravine. During the winter we would gather at my cousins’ house down the street to have sandwiches by the fire, play canasta, and listen to the Sunday night lineup of radio comedies. Caroling at Christmas was a neighborhood tradition.

During the war we daily followed the battlefronts in the newspapers. The maps gave graphic testimony to the grinding progress of the Allies. I think my interest in maps as representations of knowledge began at that time. The tide of success in the war of course was more evidence of our belief in human progress.

After the war, as a teenager, I began to read. Mother directed me to Thomas Hardy, whom I liked, both for the aphorisms about human nature embedded in his narratives, and the way he described the entire environment within which the individual characters worked out their fates. At 16, I made $15 on the offer of my Grandfather Murray for memorizing Gray’s Elegy. Having spent the first 12 years of my life under FDR, I got interested in the presidents and memorized them all. On frequent visits to my Murray grandparents, I absorbed U.S. history from books in their library and wrote my own history of the presidents, complete with text, pictures from magazines, and electoral maps for each campaign, created with a home mimeograph—author and publisher at age 15! On one occasion I accompanied my grandparents to a meeting of veterans of the 1898 Spanish-American War, in which grandfather had served as a medical officer just out of medical school. In the show was a hypnotist, the only time I’ve seen people stretched out like boards between two chairs. I doubted then, and since then, that I could let go of my consciousness to have that done to me (if it really happened!).

The exploding of the atomic bombs in Japan in August of 1945 gave rise to a lot of news and information about the physics behind the bomb. Father was much interested in this, stimulated by Spedding’s role, and we absorbed numerous magazine articles and several books explaining the periodic table, uranium and plutonium (Iowa State was important in its production), nuclear fission, and so on. I was impressed with how the bomb was a product of both experiment and theory, and began to think of this as the natural way to carry out any kind of science.

Although my main aim in life at that stage was sports, I was too scrawny to get on the varsity, so I began to be interested in science in a small way: listened to my crystal radio, learned Morse code, built a radio, feasted on the Hallicrafters catalogs with their enticements to build your own TV (strange how 2” screens in big clumsy boxes quickly became obsolete, but now those little screens seem to be the future, housed in thin slivers of plastic).

A curious side event was Grandmother Murray being named American Mother of the Year in 1947. She had been an early feminist, chair of the city School Board in the 1920s, and had written extensively on family matters and then international affairs. It also reflected of course her five children and their spouses, who were successful in various ways in academia, medicine, and the military. They became increasingly important role models.

In the early 1940s father began publishing a textbook in agricultural economics, which eventually went into seven editions over the next 40 years, followed by two other textbooks. So there were often index cards spread over the living room floor as mother prepared the indexes, a condition that seemed a normal part of home life.

Summers were a time to find a job. Fortunately, through my friend Bob Brayton’s dad, we got on a crew of buddies detasselling corn during the teenage years. Although the Iowa summer temperature often was in the high 90s, we all felt lucky to have a job and a steady income (50 cents an hour). Later I spent the summers of 1951 and 1952 on the home ranch in Canada working for my rancher cousin Jack. It was an exhilarating experience, actually to be living the life father had lived, among the broad sweeps of the prairie and under the enormous sky, working with Jack and neighbors, handling animals, branding, building fences, putting up hay. For a while I tried to imagine a career for myself as a rancher. But reality set in, and after the second summer I hungered for the life of the mind. However, that experience reinforced my feelings of closeness with good people battling adversity to scratch out a living in the real world.

My high school academic record was relatively indifferent. I was lucky to have fast-friends: Dick Day who every week it seemed had a new theory to challenge me, and Bob Brayton who stimulated my interest in math and science. Among my high school teachers, Ronald Easter taught physics and chemistry with discipline, and Mary McNally especially opened my eyes to world literature. My biology teacher Richard Trump in a recent memoir recalls that I could be a bit flippant. When we graduated we were asked what we thought we would become in life; I answered “I don’t know what I will be, but I know I won’t be a doctor.”

Iowa State

With my lackluster record I was not going to compete for any scholarships to go to eastern colleges. And I couldn’t very well argue that I needed to go to a college with a better faculty than Iowa State where my father taught! Anyway, my buddies were going there. Furthermore, with four siblings we had to save money, and tuition at Iowa State was just $54 a quarter. Even at that, mother found the Laverne Noyes full-tuition fellowship for children of World War I veterans, which father had been in Canada.

An interesting sidelight along the way was that television was just starting in the Midwest in the late 1940s, and Iowa State’s radio station, WOI, got one of the first licenses. I had taken part in a radio program of ‘Penrod and Sam’ (playing Penrod) in 1948, so was on the spot as the station shifted over to television, occasionally serving as floor director for a WOI-TV-produced talk show. When I started out in college in 1951, they employed student announcers, so I sat in the broadcast booth and did the announcing at the breaks. I can still remember my lines: ‘This is WOI-TV, Channel 4 [sic], in Ames. WOI-TV, the first educationally owned television station in the nation, is dedicated to bringing the best the College has to offer, in programs of education, entertainment, and public service. The time is eight o’clock, and Wonder Bread is good bread . . .’ the last indicating how the station was functioning at the border between public and commercial. One of the programs I announced was “Through the Magic Window,” created and produced for children by my cousin Joy Ringham, which was popular all over the Midwest. We realized at the time that we were extremely lucky to be in on the ground floor of the television era; there were people all over the country begging to have my simple job of announcing program breaks. Much later I had occasion to meet John Chancellor, the NBC TV commentator. He was telling others about his early experiences in television news around 1950, so for fun I challenged him that I had been in television before he had. It was close! TV beckoned as a career, but I was more interested in exploring academic careers.

At Iowa State I started out in economics but couldn’t work up much interest. It seemed to be all about money—how dull. Later I read a quote from George Bernard Shaw: “I started out in economics, but cheerfulness kept breaking in.” My sentiments exactly. Fortunately, at Christmas of my sophomore year my cousin David Murray, then a student at Washington University Medical School, got married. At the gathering of the clan I hung out with Dave, Grandfather Murray in general practice, and Uncle Ed in epidemiology at Harvard, eager to understand their knowledgeable exchanges about medical matters. I immediately decided this was the guild I wanted to join.

From then on courses in the premed curriculum were interesting and challenging, and my academic record improved significantly. My two most inspiring teachers were Howard Hamilton, who had revised Lillie’s Embryology of the Chick, and taught an outstanding course in experimental embryology, and Keith Huntress, who gave a marvelous course in modern poetry, which gave me a deep sense of how to use words carefully to convey meaning. These influences have lasted a lifetime. I also was a student assistant to Norman Graebner, a leading American historian, helping him add to his thousands of index cards. It made me toy with the idea of becoming a historian, which father rapidly squelched; my aim should be a career of practical value!

For the summers of 1953 and 1954 I traveled east to bunk in with Uncle Ed Murray in Cambridge, Massachusetts, working as an operating room technician at Mount Auburn Hospital in Cambridge. The job and the Harvard ambience were quite a change from the ranch, but having the family connection made me feel equally at home. The second summer I interviewed for a job with George Wislocki, chair of Anatomy at Harvard, who had contributed to identifying the hypothalamo-pituitary portal system. His interview technique was straightforward; after a brief welcome, he said: “How good are you?” “Very good,” I replied. By all rights I should have signed on, with a chance to work with members of the Harvard faculty, but the job consisted entirely of looking after rats in the animal room and I was afraid of allergies, with which my brother was plagued.

I applied to three medical schools: Iowa, Cornell, and Harvard. Iowa accepted me; Cornell to my astonishment offered me a full scholarship; and Harvard accepted me with partial support. It was hard to turn down the Cornell offer, but with a Harvard Ph.D. father, one uncle at the public health school, and another a Harvard graduate from an old Boston family, the die was cast.

Shortly before graduating from college, I heard from a physicist neighbor, Joe Keller, about Norbert Wiener’s “cybernetics,” read his book, and decided that I wanted to study how brain circuits control human behavior. Over a half century later I’m still working at it.

Harvard

Starting medical school, I wanted to plunge into brain research. I tried to get into the medical sciences group, but it was full. I talked to J. C .R. Licklider at MIT, known for his involvement in information technology and cybernetics, but no position. So medical school began to be a bit frustrating. In our histology class Pat Wall came over from MIT to teach the neuroanatomy part. I asked him for the best introduction to neuroanatomy, and after a moment’s hesitation he said with his characteristic twinkle: Herrick’s Brain of the Tiger Salamander. I went out and bought a used copy for a dollar. Herrick showed how one could construct a complete wiring diagram of a “simple” vertebrate brain. I guess this planted the seed of later microcircuit wiring diagrams in my own brain.

Through Pat I was able to land a summer job at MIT with Walter Rosenblith (later Provost), in Norbert Wiener’s old RLE barracks laboratory. My job was to take part in experiments on auditory evoked potentials in cats and run an early analog computer to do auto and cross correlations of the responses. It was an exciting time, with a large group of young people who became leaders in auditory physiology, including Moise Goldstein, Larry Frishkopf, Dan Geisler, and Nelson Kiang. Fourier transforms were the method of the day. I realized that this kind of linear mathematical approach was not going to give me the kinds of insights I wanted into neural function at the cell level. I also interacted quite a bit with Karl Pribram, visiting there for the summer, and also got to know Jerry Lettvin, whose laboratory was in the same building. Although our study didn’t lead to a publication, a subsequent study applying the computer to auto and cross correlations of cardiac arrhythmias with classmate Van Angelakos was my first paper, in 1957. This was an early example of the application of computers to electrophysiology. With this start, I’ve worked with experiment and computation my entire career.

In the next summer, of 1957, I fulfilled a need I had long felt to engage in foreign service. Several Murray ancestors had been missionaries, and Uncle Ed had had a storied career, teaching at Robert College in Turkey, exploring the interior of Asia (reported in two National Geographic articles), studying Brill-Zinsser disease in Yugoslavia, and now working on trachoma in the Middle East. I got help from the chair of neurology, Derek Denny-Brown, to arrange an externship in neurology at the American University Hospital in Beirut, with added support from Ed to study inclusion blenorrhea, an eye disease like trachoma, in the Palestinian refugee camps in Lebanon. It was a fascinating time, the summer after Suez. My new Arab friends at the University were alive with strong feelings about Suez and Palestine. Many had lost their homes in 1948. To learn some background I audited a course on modern Middle East history taught by Albert Hourani, an Oxford don and a world expert in this subject. I took detailed notes, which I still study, of his wise observations on how politics works in the Middle East. In the hospital, I attended a young British woman in an iron lung who had contracted polio in Iran, surely one of the last persons stricken with that disease. Through the neurologist Fuad Sabra, my host, I also met his brother-in-law, Charles Malik, the Lebanese philosopher and politician, who was soon to be president of the UN general assembly. It was a memorable evening observing him receiving the local politicians in his home. At one point he shook his head and confided to me, “I only wish to return to my books and my refractions.” Accessing one’s memories through refraction rather than reflection I found intriguing.

Although I enjoyed my medical classes I knew my heart was in research, so began looking for a laboratory after medical school. Spring of 1958 took me to the Federation Meetings in Philadelphia, where I heard an inspiring talk by Charles Phillips of Oxford University reporting the first intracellular recordings in the brain above the spinal cord, from Betz cells in monkey motor cortex. Vernon Mountcastle reported on his discovery of cortical columns at the same meeting, so those were exciting times. I decided I wanted to work with Phillips on the local circuits that mediate the cortical re-excitation and recurrent inhibition that he had discovered. Fortunately a fellow medical student from Iowa, Rex Jameson, had returned from his Rhodes Scholarship at Oxford, and put me in touch with a former Oxford student, Elmer Pfefferkorn, who knew Phillips. After meeting and talking about my plans with Elmer, I wrote to Phillips. He wrote back with the words: “Any friend of Elmer Pfefferkorn needs no further introduction to me.” It was the way science worked in those days. I was lucky to receive a USPHS postdoctoral fellowship in 1959 and have been supported by the USPHS and/or NIH ever since (50 years and counting).

Also during my last year in medical school I visited my friend Dick Day in Washington, D.C., where he fixed me up on a blind date for New Year’s Eve with someone he had just met. Her name was Karen Margrethe Gadegaard, a Danish exchange student at Vassar, a young woman full of joie de vivre who he said would be more than a match for me. Indeed she was, and has been ever since. That summer Grethe applied to St Hugh’s College in Oxford and was accepted. We were married in her village church in Humlum, Denmark, and began our studies at Oxford in September 1959.

Oxford

Europe was still recovering from the war, and life in both Denmark and Britain was frugal. Television was not a part of our lives in either place. Buildings in Oxford were covered in soot; renovations were just beginning. Students at Oxford wore black gowns (“sub-fusc”) and got around on bicycles. Phillips had arranged a wonderful flat for us, at the top of the ancient Priory in Iffley village, from which one could see the spires of Oxford floating in the distant haze. We cycled into Oxford every morning down the Iffley Road and across Magdalen Bridge. I was attached to Trinity, where Phillips was a tutor. Grethe and I spent many pleasant lunches on the Trinity lawn admiring the herbal border or at the White Horse among the patrons playing push ha’p’ny.

I started out as a postdoctoral fellow and shifted to work for a D.Phil. (as it’s called in Oxford), both firsts for Phillips. When I arrived he was stimulating the motor cortex and recording from the spinal cord to carry out his pioneering studies of the control of the hand. However, my mind was set on cortical circuits. He remembered that his colleague Tom Powell had suggested the olfactory bulb as an ideal model for functional analysis of a cortical system, and after a joint meeting we launched this as a new project. Nothing at the time was known about the cellular physiology of the olfactory bulb. So I went off to Blackwell’s to buy the two volumes of Cajal’s Histologie du Systeme Nerveux and burned into my brain those black-etched images of the neurons in the olfactory bulb and throughout the brain.

The fact that this was a project on the olfactory bulb in a motor systems laboratory indicates the degree of freedom there was in research in those days. In fact, I still have a letter from Phillips before I arrived, emphasizing that in thinking about a project I must not feel restricted to what he was doing.

Phillips led the way in setting up the preparation for working on the olfactory bulb in the rabbit. He and Tom worked with me through the fall, during which we ascertained that stimulating the lateral olfactory tract with single shocks elicited antidromic action potentials in presumed mitral cells, that this was followed by long-lasting inhibition, and that the shocks elicited a succession of field potentials which could be used to identify the layer of mitral cell body recordings. He then turned the project over to me to pursue for a doctoral thesis.

It was just at the end of the era when one was expected to build one’s own amplifier. Fortunately the Tektronix 502A oscilloscope was just arriving in England. To control vibrations, Phillips had the shop build a massive animal holder out of steel pipe (while wheeling it down the corridor it slipped and made a small gash in the linoleum; the mechanic George Johnson quipped: “You’ve made your mark at Oxford.” Fifty years later the mark is still there!). For micropipettes, we used the microforge built by the machinist Edgar Schuster. Pulling micropipettes on that pioneering setup required extremely steady nerves! Schuster also custom-built us a head-holder for the rabbit. The laboratory technical assistant was Charles Carr, a meticulous and amiable gentleman, who as a young man in the 1930s had been the last technician hired by Sherrington, a rather nice connection to my scientific lineage (Phillips a student of Eccles a student of Sherrington).

As I took over the project, and began to compare the physiological results with those images of Cajal, I realized in an “aha” moment that my project from then on would not be about the olfactory bulb, but about dendrites and axon collaterals. That has been my use of the olfactory bulb, as a model, ever since.

The first priority was to correlate the field potentials with the bulbar layers. As it happened, Tom Powell had just returned from collaborating with Vernon Mountcastle on their classic papers correlating the functional columns with the anatomy of the cortex. We therefore applied Tom’s methods directly to the olfactory bulb, a correlation between layers and field potentials that has been useful in olfactory bulb studies ever since.

In brief, the study demonstrated self and lateral inhibition of mitral cells. We established this first for antidromic activation from the lateral olfactory tract, and then for orthodromic activation after I devised a new method for activating orthodromic volleys by delivering somewhat longer electrical shocks to the olfactory nerve bundles in the dorsal recess of the nasal cavity. At the time it wasn’t known that fine (0.2 μm diameter) unmyelinated fibers were electrically excitable. Based on recordings from presumed granule cells, I inferred from those images of Cajal that the inhibition was mediated through the granule cell superficial process. I reported the first recordings at a Physiological Society meeting in January 1961, joining the many who have been through that ordeal by fire (with Hodgkin, Huxley, Katz, and others sitting in the audience, whose murmur of doubt about a result could crush any aspirations toward a career in science—or so it felt).

Three papers reporting these results were published in the Journal of Physiology in 1963, the year after I had left Oxford. I made explicit the inhibitory feedback circuit through the granule cell with a circuit diagram. The only precedent for such a diagram was by Eccles in the spinal cord (this was before the cerebellar studies of Eccles et al.), so I assume this must have been one of the first circuit wiring diagrams for a region in the vertebrate brain. The advantage of the diagram was that it provided testable hypotheses for the connectivity mediating the physiological properties. The connectivity for the granule-to-mitral inhibition seemed strong, though it required thinking of the dendrite as being “axon-like,” as well as having a prolonged inhibitory action in the absence of action potentials, unlike a Renshaw cell.

The connectivity for the mitral-to-granule excitatory activation was postulated to occur through deep collaterals of the mitral cell axons.

Those were halcyon years in Phillips’ laboratory. Not only did I have the freedom to pursue my own project, but I had freedom from a formal thesis program. This may seem antisocial, but I had had four intense years in medical school, and just wanted to get into a laboratory and do electrophysiological experiments. I recall on one occasion a visitor from the United States, Hermann Rahn, I believe, who was conversing with department members at afternoon tea, curious about comparing Ph.D. programs. What kind of course work do you have? None. What kind of seminar program do you have? None. What kind of prelims do you have? None. What kind of social support for the students do you have? None. He was stunned. I just sat there, quite content with my nonexistent program.

There were giants for inspiration. Francis Crick, Louis Leakey, and Peter Medawar gave talks; I visited Niko Tinbergen to ask about ethological studies involving smell; Gilbert Ryle spent an evening with us at the Osler Society; Eccles came by on one of his trips; there were tea time chats with Maurice Pirenne, the pioneer visual psychophysicist; my first seminar was to le Gros Clark and his department.

In the spring of 1962 I passed my “viva” (the Oxford oral exam), carried out as a conversation for a couple of hours with George Gordon of the department and J. A. B. Gray of UC London. Meanwhile, Grethe was succeeding in her examinations for her B.A. in English Literature.

National lnstitutes of Health

During the last year I looked for a job in the United States I had some correspondence with Donald Griffin, the well-known auditory physiologist, with the idea of learning more about sensory physiology of another system, but in the end he had no position. I had met Torsten Wiesel and thought that it would be great to work out the circuits underlying their simple and complex cells, but they were not taking students at the time (life was too exciting for them!). Through Tom Powell I contacted Mountcastle to pursue the circuits in the columns in the cortex, he wrote back that he wished he could take me, but he already had 10 in the laboratory and just couldn’t handle any more. Things were looking a bit bleak.

In the spring I had run across theoretical papers by Wilfrid Rall on currents and potentials around dendrites. Since dendrites were now my field, and I had an underlying interest in applying theory to experiments, I wrote to him about the specific field potentials correlated with different layers and different physiological actions, asking whether he would he be interested in applying his methods to them to obtain a rigorous relation between the field potentials and the neuronal elements that had generated them.

Wil wrote back that he was interested. It then depended on finding a position quickly, which he was able to do when Wade Marshall and Karl Frank offered us a slot in the Laboratory of Neurophysiology at NIH. Until then Wil had worked mainly on the motoneuron, then the model neuron for intracellular studies, so again I was taking advantage of the expertise of a motor system laboratory to apply it to the olfactory bulb.

In late August Grethe and I sailed on the Nieuw Amsterdam for New York, and on to Bethesda. I then had to take and pass the exams for admittance to the Public Health Service, to serve my 2 years in the uniformed services, and to start the new job. It was a long month to be without a salary, but nothing ventured, nothing gained.

As with Phillips, I was Wil’s first postdoctoral student. It was early in his career, at a time when he was attempting to establish the new field of computational neuroscience in the face of considerable opposition, not least by his former mentor, John Eccles. I learned at first hand how unduly harsh criticism can bring hardship to a young investigator and deny deserved recognition. Through it all Wil was a gentleman, and he has remained so, one of the finest people I have known.

I spent 2 years with Wil, leaving experimental work to undertake with him a computational reconstruction of the activation of mitral and granule cells. Our project was to see whether we could simulate the field potentials from the intracellular potentials more accurately than had been done previously in other systems, by taking advantage of the symmetry of the olfactory bulb layers and the correlation with the single-cell recordings and the simplified anatomy. Wil had figured out how to simulate the intracellular potentials using his new compartmental method, and how to simulate the extracellular potentials using a potential divider model. Fortunately my recordings were sufficient to provide the needed physiological data, as well as a very tight correlation with laminar depth due to the methods with Powell.

By August of 1964 we had the simulations of mitral cell followed by granule cell responses. While discussing one day how the granule cells might be activated, the “aha” moment occurred. We hit on the idea that it must be through the same mitral cell lateral dendrites that were then inhibited. Wil’s protocol book contains our speculation that these “dendrodendritic synapses” provide a mechanism for “lateral inhibition” in the olfactory bulb. There was no evidence for this kind of interaction between dendrites at the time. However, I had come to know Tom Reese and Milton Brightman, who were about to undertake an electron microscopical study of the olfactory bulb, so I told them to be on the lookout for such synapses.

Shortly after I had left for a further fellowship in Stockholm, Reese and Brightman found synapses between mitral and granule cell dendrites oriented in opposite directions. Wil attended their seminar and immediately told them how the synapses fit with our model. It was a case of the model predicting the fine structure and explaining the physiology, rather than the other way around as is the usual case with models. Over the next few months we put together a paper on this multidisciplinary study, probably the first to combine electrophysiology, electron microscopy, and compartmental modeling. We submitted it to Science, who promptly rejected it as “not of general interest.” It was published in Experimental Neurology in January 1966 and opened up several new lines of investigation as described later in this chapter.

Karolinska

Meanwhile, at the Karolinska Institute in Stockholm, I had joined David Ottoson to learn about olfaction, in order to apply this knowledge to understanding how the bulbar circuits mediate smell perception. Ottoson was widely known for his discovery in 1956 of the electroolfactogram (EOG), the summed potential response of the olfactory epithelium to odor stimulation. He had then worked with Stephen Kuffler at Woods Hole, where he and Charles Edwards discovered the site of impulse initiation far out on the axon initial segment in the crayfish stretch receptor, one of the classical studies on the integrative organization of the neuron. He had returned to Stockholm intending to pursue studies of the receptor, but crayfish were not then obtainable, so he was forced to develop a new preparation of the isolated muscle spindle of the frog.

I worked with David, also as his first postdoctoral student, for the next 2 years on that preparation. Although it was a diversion from my main interest in brain mechanisms, it gave me an extensive background in sensory reception in general, as well as an introduction to the broad field of olfactory studies, summarized in a review (Ottoson and Shepherd, 1967).

We had a great time in Stockholm, living in the new Wenner-Gren Center and enjoying the ready access to the rich culture of that city. The proximity to Grethe’s home in Denmark was also a big plus. At the end of our stay, in the summer of 1966, I worked with Grethe’s 85-year-old father, a master carpenter, and her brother, an engineering student, to build a summer house near her home in Humlum where the family could stay when we visited. It is on a site called Toftum Bjerge (Toftum Mountain), one of the highest peaks in Denmark—50 meters above sea level! Toftum has been a summer home for us ever since.

At that point I could look back on 7 years of postdoctoral training after graduating from medical school. It was a rich experience, with training in a series of different but interrelated experimental and theoretical approaches to neural organization and mechanisms. I often tell my students to take advantage of these opportunities in your early training; it is the time when you build up the capital that you will invest throughout your career.

Yale

During my time at NIH I had visited with my good friend from Oxford, John Nicholls, at Woods Hole where he was working with Stephen Kuffler. I discussed with Kuffler my interest in finding a job on returning to the United States and my aspiration to create a multidisciplinary unit emulating his neurobiology department at Harvard. He put me in touch with both his close colleague and friend, Cuy Hunt, who was the new chair of physiology at Yale, and John Gergely at the Retina Foundation in Boston. The Retina Foundation seemed like a better prospect for setting up my multidisciplinary unit, so with the enthusiasm and naiveté of youth I arranged to return to the United States to a position there in September 1966. Unfortunately, it turned out not to provide the expected opportunities. Through Pat Wall I moved to MIT for the remainder of the year and was fortunate to be reinvited by Cuy to Yale. We moved there in July 1967.

My time with Ottoson, though rewarding in many ways, was for starting my career a mixed blessing, because he had become the target of heavy criticism by Lloyd Beidler and his students in the United States, who questioned whether the EOG was an artifact. This had little justification scientifically and had severely set back Ottoson’s career in Sweden. Again I saw the unfortunate effects of overly harsh criticism. It meant that when I returned to the United States I was out of favor with the field of olfaction.

To start with, this didn’t matter to me very much, because I considered my field to be cortical organization. My first RO1 grant, awarded in September 1966 while at the Retina Foundation, was entitled “Basic Mechanisms of Cortical Integration”; my site visitors were Carlos Eyzaguirre and Larry Kruger. That grant has served as the foundation for the laboratory, providing 43 years of continuous funding and counting. I also received a Research Career Development Award (RCDA)—site visitor David Lloyd, a former colleague of Cuy Hunt. I came with no startup package, which as far as I knew didn’t exist; I was just happy to land at Yale on my feet. With a $30,000 grant from NINDS and $14,000 salary I had enough to start a laboratory.

It was in an atmosphere of challenging new ideas that I set up the new laboratory in the Physiology Department at the medical school at 333 Cedar Street at Yale in 1967. It was an exciting time there, because the school was going through a transformation in the 1960s from the old school to the new. Five of the six departments were seeking chairs, so it had the feeling of a new school inventing itself. The department was an exciting mix of outstanding young people: among the neurophysiologists were membrane physiologists (Knox Chandler had trained with Hodgkin; Larry Cohen had coinvented voltage-sensitive dyes) and cell physiologists (Bob Martin had trained with Katz, John Nicholls with Kuffler; Charles Michael did Hubel-Wiesel studies).

Starting out was greatly facilitated when in the first few months Lew Haberly came to the laboratory as my first graduate student. His impeccable skills and thoughtful analysis set the bar for everyone that followed, which continued in earnest after I returned from a year at Penn, first with Tom Getchell, then John Kauer and Bill Stewart.

This started a tradition in the laboratory of matching the talents of every new person to a new direction in our research. I’ll attempt to organize the discoveries that ensued over the years, thanks to over 60 outstanding students and visitors.

Dendrodendritic Synapses

During 1967 I made several trips to NIH to finish the study with Wil, which was published at the end of 1968 in the Journal of Neurophysiology. Surprisingly, the paper was immediately of broad interest for several reasons.

First, our study was among the first wave of reports of the circuit organization of different parts of the brain. Dowling and Boycott, followed by Werblin and Dowling, provided parallel evidence for the circuit organization of the retina, also involving reciprocal dendrodendritic-like synapses. Soon dendrodendritic synapses were reported in the different nuclei of the thalamus by Ralston (1969), Famiglietti and Peters (1971), and Morest (1971). Eccles and his associates published their studies of cerebellar circuits (Eccles et al., 1966). It was interesting to be contributing to the new ideas brought forth by these and other laboratories. An opportunity to attempt a synthesis came with a year’s sabbatical as the visiting scientist of the Neurology Institute at Penn in 1971–1972, at the new Monell Institute and with my friend Sol Erulkar; out of it came a course and then a book on The Synaptic Organization of the Brain.

A second reason for wider interest was that we had solved the puzzle of the granule cell—how could a cell in the central nervous system be a neuron if it lacked an axon? The cell received synaptic input onto its dendritic spines, like other spiny neurons, and sent its synaptic output from the same spines. It therefore had a synaptic output like all other neurons. Similar evidence was obtained in the retina for the reciprocal synapses between bipolar and amacrine cells.

A related reason was that the dendrodendritic mechanism posited a specific role for the granule cell spine: feedback and lateral inhibition. This was I believe the first specific function for a dendritic spine; 40 years later it is still one of the clearest roles for a spine.

The mechanism posited a specific role for an action potential spreading into the lateral dendrite: activation of the dendrodendritic synapses to bring about feedback and lateral inhibition. More recently similar backpropagating action potentials have been assumed to play important roles in the dendrites, though their functions are still being elucidated.

The dendrodendritic synapses also required revision of the functional concepts of the neuron doctrine. Revisions had been started by a seminal paper by Ted Bullock in 1959, summarizing the multiple ways that neurons were being shown to interact. Since Cajal the concept of the neuron doctrine had included the idea that neurons receive their input in their soma and dendrites and send their outputs through their axon. The dendrodendritic synapses showed that this no longer held: dendrites could be sites of output as well as input. Furthermore, these input-output operations could occur locally, as semi-independent integrative units, without involving the entire cell. This resulted in a paper in 1972 on “The Neuron Doctrine: A Revision of Functional Concepts,” the first of a series of papers and a book on the conceptual foundations of modern neuroscience.

Finally there was the fact that our study involved the earliest use of Wil’s compartmental approach to build computational models of neurons. Wil deserved all the credit for this great contribution to neuroscience. My role in our collaboration was to help fine-tune the models and match them precisely to my experimental studies of the anatomy and physiology of the olfactory bulb. The principles of dendritic electrotonus and active properties involved have guided my work ever since. We often discussed how we envisaged the time when it would be possible for physiologists to carry out computational analysis in the laboratory of the cells they were working on, in parallel with experimental analysis, so that each approach could test the hypotheses developed by the other. It took a generation for that to begin to happen. One feels fortunate to see that prediction realized and to have contributed to it.

Glomerular Dendrodendritic Interactions

One of my first studies in the new lab was to obtain physiological evidence for dendrodendritic synapses in the olfactory glomerulus, which seemed pretty impenetrable—a literal “Gordian knot.” However, a strategy of using very weak peri-threshold paired volleys in the olfactory nerves produced evidence for inhibitory actions between mitral and PG cells that appeared to be mediated between glomerular dendrites. When detailed EM studies of the synaptic connections in the glomerulus were carried out by Price and Pinching, I was able to reconstruct their findings, even from their 1970 abstract, and fit them precisely into a circuit consistent with the physiology. That provided a “basic circuit” diagram of the olfactory glomerulus to go with the mitral-granule interactions and the initial overall circuit diagram from my Oxford days. This was published in a review on the synaptic organization of the olfactory bulb commissioned by Eccles in Physiological Reviews in 1972. These diagrams have been used by others and greatly modified and extended by work in the field ever since. When Tom Getchell joined the lab, we produced two Journal of Physiology papers with this approach in 1975. Physiological analysis of the glomerulus then lay fallow in the field for a quarter of a century.

Olfactory Cortex Basic Circuit

Lew Haberly came to the lab with recordings of spike responses in rat olfactory cortex to odor stimuli, so it was natural to launch a study of the circuit organization of the cortex. We thought the dog would be an optimal preparation for this study, but a dog undergoing anesthesia was too hard on our sensibilities. We opted instead for the opossum, with its large nose, olfactory bulb, and olfactory cortex—one of many new preparations introduced over the years. As a tune-up we recorded local evoked field potentials in the olfactory bulb to focal stimulation of the lateral olfactory tract, showing that there is a topographical relation between the tract and the bulb. This study also showed how Wil’s field potential model facilitated the interpretation of local field potentials. This model still awaits more general use, as local field potentials are increasingly employed in analyzing neural systems.

Lew then turned for his doctoral thesis to an in-depth analysis of the functional organization of the olfactory cortex, using intracellular, extracellular, and field potential responses evoked by LOT shocks. His correlation of the field potentials with the cortical layers is still used today. He was midway through documenting the lateral inhibition implied by Walter Freeman’s earlier linear systems analysis when Maria Biedenbach, working with Chuck Stevens in Washington, reported recordings implicating inhibitory interneurons activated by pyramidal cell axon collaterals. Undaunted, Lew carried out an early current source density analysis of the field potentials. He was one of the first to include a conductance shift between layers in CSD (current source density) analysis, which revealed a hitherto unrecognized excitatory collateral feedback system. Almost concurrently, Joe Price’s anatomical studies revealed the axon collaterals for this system, which came to be called the “long association fibers.” When added to the LOT input and the inhibitory interactions, it completed a new basic circuit for the olfactory cortex. This study was published in three papers in the Journal of Neurophysiology (Haberly, 1973a, 1973b; Haberly and Shepherd, 1973).

This basic cortical circuit was central to the account of cortical organization soon published in the first and succeeding editions of the synaptic organization book. Lew then used the circuit, particularly the long association fibers, to introduce the concept of the cortex functioning as a “content addressable memory” for processing complex odor stimuli, in analogy with the face area of the visual neocortex (Haberly, 1985). A similar basic circuit was then invoked by Connors and Kriegstein (1985) in their study of the organization of turtle dorsal cortex. Several papers have pointed out the key features of this circuit, which may have been a fundamental plan for the emergence of neocortex, a concept still being developed.

Dendrodendritic Interactions and Lateral Inhibition

Despite the attractions of the cortex, a high priority for the lab was obviously testing the mitral-granule cell dendrodendritic model. I tried to get further evidence with Sol Erulkar during my stay at Penn in 1972, but the in vivo preparation was too unstable. It was frustrating, because we were not keeping up with the work on circuit organization of the retina, cerebellum, and other regions. The introduction of in vitro slices of hippocampus in the early 1970s showed the way we had to go. The opportunity came when Martha Nowycky and Kensaku Mori joined the laboratory in the late 1970s. In thinking about an in vitro preparation, I had been impressed by hearing from my friend Denis Baylor that in his study of the turtle retina he could work on one retina one day and take the other retina out of the refrigerator and work on it the next day. There must be something about the turtle that made for a good in vitro preparation!

Martha was initially interested in the dopamine projection from the brainstem, so we removed the entire turtle brain and made a hemi-brain and brainstem preparation for in vitro study, which enabled one to stimulate the brainstem as well as the olfactory tract and olfactory nerves and record from the olfactory bulb. At about the same time Rodolfo and his colleagues were reporting a perfused preparation of the brainstem. I was very concerned about the viability of our unperfused preparation, but Kensaku carried out an initial intracellular study showing long-lasting inhibitory postsynaptic potentials (IPSPs) in mitral cells following lateral olfactory tract (LOT) stimulation, just what I had found in the rabbit 20 years earlier. He and Martha then did a thorough study showing the calcium component of the action potential, successive short-term IPSPs, and a very long-lasting IPSP in the mitral cell, reported in three papers in the Journal of Physiology in 1981. Two more papers in the Journal of Neurophysiology used pharmacological manipulations to characterize long-lasting synaptic excitation, including autoexcitation, in the distal tuft of the mitral cell. After Kensaku returned to Japan we published two more papers from his studies, on fast prepotentials and on excitatory and inhibitory interactions in the distal dendrites, so the turtle was a productive innovation, thanks largely to Kensaku’s consummate intracellular recording skills.

Martha’s first abstract on the isolated turtle brain preparation at the SFN meeting in 1978 prompted Roger Nicoll and Craig Jahr in San Francisco to exploit the turtle olfactory bulb too. An interesting sidelight is that they were able to demonstrate feedback inhibition after current injection into a recorded mitral cell, which we could never get. A few years later, after NMDA receptors had been characterized, we all realized, chatting together one day, that this was due to the fact that they had used a Mg²⁺ free Ringer solution, whereas we had used the standard Ringer containing Mg²⁺. According to Roger and Craig, when they started they checked for what Ringer fluid to use from an old publication of Katz’s on muscle, where he happened to be working in Mg²⁺ free Ringer! Such is the life of the laboratory.

Topographical Relations between Epithelium and Bulb

For carrying forward the study of the intrinsic circuits of the olfactory bulb, we realized we needed to know how the input related to them. In the 1950s le Gros Clark used degeneration in the nose after local ablations of the olfactory bulb to reveal a rough topographical organization from epithelium to bulb. Adrian had then showed that multispike recordings from the anterior and posterior part of the bulb showed differential responses to different odors, suggesting a spatial representation of odor molecules.

One of the most used tools for demonstrating axonal projections of that time was the Nauta degenerating method. A colleague, Bob Eager, pointed out that it had never been proved that one could stain fine unmyelinated C fibers, such as in the olfactory nerve. A biology graduate student, Lanay Jordan Land, undertook the project, and with focal ablations of the olfactory nerve bundles in different parts of the nasal cavity was able to show degenerating terminals restricted to subsets of olfactory glomeruli. We developed a flat map method for representing the localization of these projections in the glomerular layer. This became the prototype for flat maps used later by ourselves, and now generally adopted in the field, for representing functional activity in the olfactory glomerular layer.

The topographical organization of the projection was further documented by the use of radioactively labeled amino acid pledgets placed in different locations in the olfactory cavity. In the retina this approach had produced dramatic images of tightly organized projections from retina to lateral geniculate nucleus. The organization in the bulb was less dramatic, due to the fact that it was related to the molecular identity of the receptor cells rather than the location in the nasal cavity. These and other anatomical mapping experiments became obsolete with the discovery of the olfactory receptors by Buck and Axel in 1991, and their use in precisely mapping the projection by Buck and Axel, Peter Mombaerts, and others. Nonetheless, the mapping of the olfactory projection, by both anatomical and functional methods, gave ample evidence of some kind of underlying organization, so that the new results were received by prepared minds.

Functional Mapping of Odor Responses with 2DG

As I was finishing my doctoral studies at Oxford in 1962 I paid a visit to Adrian to discuss how my results might relate to his ideas about the representation of odors by spatial patterns of mitral cell activity in the olfactory bulb. What was the mechanism underlying the spatial patterns? I don’t remember the details of our conversation, but I do remember his final advice: “Look to the glomeruli.”

During the late 1960s and early 1970s, David Moulton and others tried various approaches to this problem in mammals. John Kauer, during his doctoral studies with Moulton, introduced the salamander olfactory bulb for this purpose. But the electrophysiological approach was difficult without knowledge of the spatial organization of the input as one had in the visual system that was exploited so brilliantly during this time by Hubel and Wiesel. What chance did we have!?

The solution came from a chance encounter with Ed Evarts, another pioneer of motor cortex. On a visit to Yale he was chatting with John and myself in the corridor, and said, by the way, there is a new activity marker called 2-deoxyglucose (2DG) that Frank Sharp in his laboratory was working on in collaboration with the founder of the method, Lou Sokoloff. It wasn’t certain how useful it would be because it mainly labeled active synapses, not cell bodies. John and I looked at each other in another “aha” moment: this was exactly the tool we needed to label activity elicited by odor stimulation in the synaptic-rich olfactory glomeruli, at a distance from the mitral cell bodies.

In December I visited Frank at NIH and we carried out the first experiments on waking rats injected with 2DG and exposed for 45 minutes to different odors, including the most natural odors we could put our hands on at the time, cheese from the local supermarket. Frank did the histology and autoradiographs, and after the holiday he called excitedly that it had worked! There were dots and spots of activity over the olfactory bulb in the films. John joined us for further experiments at NIH, and we soon had the first publication of the application of functional localization in the olfactory bulb. This was true localization, virtually to the level of single glomeruli or groups of glomeruli, a significant step from the multispike unlocalized gradients reported by Adrian. We had “looked to the glomeruli” and found the mechanism! Once again, a motor laboratory had contributed to the olfactory bulb model for basic mechanisms of cortical integration; Frank’s efforts were monumental, and Ed’s support crucial.

Nowadays we would have insisted on publication in a high-profile journal, but we couldn’t preempt the first paper on the Sokoloff method that hadn’t yet been submitted to Science. So we submitted ours to Brain Research, and it came out in the same year (Sharp et al., 1975). The impact was muted, for several reasons. There were few laboratories interested in the olfactory bulb; the 2DG isotope was expensive; few in the brain imaging field were interested in olfactory imaging. Nonetheless, we had the excitement of opening the new field of functional imaging of the olfactory bulb, as well as contributing to the new field of functional brain imaging using positron emission tomography (PET). Again, the use of the olfactory bulb as a model system had produced results of general interest.

Follow-up studies established the basic properties of the patterns. The most intense activity was localized to the glomerular layer (Sharp et al., 1977). The patterns in the glomerular layer were displayed using the flat-map representation of the glomerular layer introduced in our previous topographical study. The patterns with different odors were overlapping but distinct. The patterns increased in extent with increasing odor concentration (Stewart et al., 1979). From these properties it could be suggested that the patterns could contribute to the encoding of odor identity as well as odor concentration. These basic properties have been confirmed by many subsequent laboratories, using many different methods in many different species.

The 2DG method also led to the discovery of a new subsystem in the olfactory pathway. This started with a suggestion by a medical student, Marty Teicher, who had worked on the suckling pheromone in rat pups for his Ph.D. at Princeton with Elliott Blass, to see what the 2DG method would show in the suckling pups. Bill Stewart led this project, which showed an intense 2DG spot of activity in the posterior olfactory bulb. We first suspected this might be in the accessory olfactory bulb, but correlation of the 2DG activity with the anatomy revealed that the focus was over a group of glomeruli that we called a “modified glomerular complex” in the medial posterior aspect of the main olfactory bulb, tucked up against the side of the accessory olfactory bulb. We set this unexpected finding aside for several months, not knowing whether to believe it or not, and finally invited a reigning expert on olfactory anatomy, Jim Hinds, to come to give advice on whether it was real. We decided it was (Teicher et al., 1979). The MGC has subsequently been shown to be a part of the “necklace glomeruli” surrounding the AOB, with its own special properties within the main olfactory pathway.

This finding occurred at about the same time as the discovery of the “macroglomerular complex” in the antennal lobe of insects, correlated with pheromone activation. Up to that time there was little recognition of similarities between vertebrate and insect olfactory pathways, despite an early suggestion that they were analogous. Our contemporary studies laid out the case for considering the modules in the insect as true glomeruli, which was rapidly adopted by the field, and is a central concept today in analyzing the underlying principles of glomerular organization. This led to many interesting interactions between our lab and many labs involved in insect olfaction, including John Hildebrand in Arizona, Jurgen Boeckh in Regensburg, and Barry Ache in Florida. The fundamental cross-phyla role of the glomeruli in olfactory processing was summarized by Hildebrand and Shepherd (1997).

With the 2DG method there was much to do for the lab, in addition to the ongoing electrophysiological studies of the dendrodendritic synapses noted earlier. For a decade or more there were only two other labs doing functional imaging, both with 2DG: Michael Leon and Andre Holley. This was characteristic of the early days of olfactory research; only one or a few labs doing a particular approach, which left the field open, but impoverished of colleagues, concepts, and competition.

Fortunately we had outstanding students to do the work. In addition to Bill Stewart and John Kauer, Charles Greer came in the late 1970s, and soon after Doron Lancet and Patty Pedersen. Charlie first focused on the physiological basis of the activity labeling, recording the 2DG labeling in the olfactory bulb in response to volleys in the olfactory nerve bundles. In both turtles (Greer and Shepherd, 1982) and rats (Greer et al., 1983), this showed that only a few hundred volleys could give intense labeling. He then carried out a developmental study in rat pups, showing the emergence of odor-specific patterns in the second postnatal weeks (Greer et al., 1982). Patty Pedersen focused on the suckling-induced patterns and found evidence for 2DG activity there in utero (Pedersen et al., 1983).

With Pavel Jastreboff, a recent émigré from Poland, a major effort was made to identify the receptor cells projecting to the MGC, using retrograde labeling of HRP after injections into the MGC area. The labeled cells were in restricted areas of the main olfactory epithelium (Jastreboff et al., 1984) and showed evidence of radial and laminar clones within the epithelium, a finding that still deserves follow-up. A more complete study of the topographical relations between bulb and epithelium followed (Pedersen et al., 1986), consistent with a similar study by Astic and Saucier.

With Doron we made a major effort toward improving the resolution of the 2DG method. The use of tritiated 2DG gave the first clear localization of odor-induced activity to individual glomeruli (Lancet et al., 2000, 2002). A subsequent study used rapid freezing combined with electron microscopy, carried out with Dennis Landis at the MGH in Boston, gave the first evidence of 2DG localization at the cellular level (Benson et al., 1985). We then turned our attention to new projects, returning to odor mapping with new methods later in the 1990s (see later discussion).

Finally, of course, all this work predated the discovery of the olfactory receptor molecules. The lab also helped to take the first steps in that direction, after weathering some transitional challenges.

Transition Years

By the mid 1970s, into my 40s, the lab was thus alive with new projects and new people working on odor maps and cell electrophysiology. One might assume that all was running smoothly, but in fact it was a period of uncertainty for myself and indeed for the future of funding for this kind of research.

Funding through the physiology study section at NIH was extremely tight. We were now focusing on problems in the sense of smell, and there was not much interest in the neurology institute in this tiny subject. The future of research in olfaction was in fact so dire that an NSF/NIH committee was formed in the late 1970s to consider how to ensure its survival. Out of this came the recommendation to set up a new society, called the Association for Chemoreception Sciences (surely the most sibilants you could pack into a society’s name), shortened to AChemS. The first meeting was held in 1978, with Max Mozell as the chair. Linda Bartoshuk was the second, I was the third, and Bruce Halpern was the fourth. Our goal was to be as successful as ARVO, whose annual meeting in Florida had helped to boost the field of vision research.

The early membership of AChemS was predominantly psychophysicists in taste and smell, all from colleges, universities, or institutes; to begin with I was the only investigator from a medical school. It was symptomatic of how taste and smell were not yet in the mainstream of modern cellular and molecular science, with the resources possible in a medical school setting. Fortunately, within a few years we began to attract other anatomists and physiologists, so that by the time Linda Buck and Richard Axel discovered the olfactory receptors in 1991 the society was ready to receive a big influx of molecular biologists and patch electrophysiologists, many from medical schools, and to assume a central role in the rise of modern studies in taste and smell.

During this time the new “National Institute for Deafness . . . ” was set up. Taste and smell, along with somatosensation, were transferred to the new institute under the humbling added words “ . . . and Other Communicative Disorders.” It was rather demoralizing to become an anonymous “other,” but there was no other home. My main grant barely made it through renewal, for only 3 years, in 1977, and I was lucky to get funded through Terry Dolan at NSF for 3 years to support the new 2DG work. So it was a relief when the R01 grant was renewed for the first time for the full 5 years in 1980, and we could look forward to a little stability and long-term planning. A Javits Award in 1985 was welcome recognition for that highly productive period of the lab.

In addition to funding problems, the place of integrative neuroscience in physiology at Yale, focused as it was on nonneural membrane physiology, was also uncertain. This was resolved with the recruitment of Pasko Rakic in 1978 to head a new Section of Neuroanatomy, together with Pat Goldman-Rakic. My position was shifted to the new section to help give it a critical mass. In 1980 we moved the lab to new quarters on the clinical side of Cedar Street, nearer the labs of the Section of Neurosurgery under Bill Collins, a staunch supporter of our 2DG work. In return we provided leadership for the Neurosurgical Research Laboratories, through Bill Stewart, John Kauer, and ultimately Charles Greer. Charlie has been a rock of support for both neurosurgery and ourselves, as well as becoming the director of the Interdepartmental Neuroscience Program for graduate studies at Yale. Life with Pasko and Pat and the new faculty was immediately rewarding, and it has been ever since. I couldn’t have asked for a more supportive chair than Pasko, and a more loyal and inspiring colleague than Pat.

A dash of uncertainty was added in 1978 when I was invited to take the chair of Neurophysiology in Copenhagen, Denmark. Being married to a Dane, with a summer house in Denmark, didn’t make this seem impossible as a career and life move. However, the visit revealed that the building housing the Institute of Neurophysiology was being abandoned, and the neurophysiology department in it absorbed into the new Panum Institute along with all the other medical science departments. Moreover, it was a strongly anti-authoritarian period in Danish life, when the chairmanship of a department was supposed to rotate among all the staff, including secretaries and other staff! Although we had to turn down the invitation, we have remained close to Jørn Hounsgaard, Henrik Jahnsen, Jens Midtgaard, and others through annual visits during our summers in Denmark.

Also attractive was an invitation in 1982 to take a chair at Oxford. I felt a strong pull to return to the place where we had had such a good student life together, but reality quickly set in when we learned of a salary far below the modest salary I was making at Yale. My Yale dean, Bob Berliner, quipped that he “didn’t know whether he could lower Gordon’s salary enough to meet the Oxford offer!” So that too had to be declined. However, we have had continuing rewarding contacts with Oxford, through our daughter Kirsten’s and her future husband Alastair’s D.Phils. in the mid-1990s, a mini-sabbatical with Julian Jack during that time, Kirsten becoming a don at St. Catherine’s, and a recent sabbatical with Kia Nobre in the fall of 2009 as an Astor Visiting Lecturer.

Dendritic Spines

The dendritic spines of olfactory granule cells were central to the dendro-dendritic model for lateral inhibition and stimulated new research by Wil and myself. Wil, with colleague John Rinzel, drew attention to the ability of the spine neck to control the electrical coupling between the synapse on the spine head and the dendritic trunk as a possible basis for activity-dependent change that could underlie learning and memory. I pointed out that it could control metabolic coupling as well. These suggestions, from theoretical studies, helped to stimulate a new field searching for the cellular changes that might underlie long-term potentiation (LTP).

Our dendrodendritic model was based on separate models for the mitral and granule cell. To complete the model, I carried out a computational study with friend Bob Brayton, then at the IBM Watson Research Center, in which we connected the two cells and reproduced the feedback and lateral inhibition (Shepherd and Brayton, 1979). It was possibly the first synaptic circuit simulated computationally.

At about the same time Scientific American invited me to contribute an article on our work. I had been following the news of the development of the first integrated computer chips and took the opportunity to title the article “Microcircuits in the Nervous System,” applying the term to the specific synaptic circuits that had been identified in the olfactory bulb, retina, and several other brain regions. Eric Kandel, Jack Byrne and colleagues used the term at about the same time to refer to the reflex circuit under study in Aplysia. The term stuck, and is now in common usage to refer to circuits at many levels of organization in the brain.

A new chapter in spine studies opened with the postulate that spines may have active properties. Wil led the way with collaborators John Miller and Idan Segev, showing how active properties in a spine boosted the response in the dendrites (Miller et al., 1985; Segev and Rall, 1987). Concurrently, Brayton and I showed how the active properties could confer logic gates on synaptic interactions in distal dendrites of pyramidal cells (Shepherd et al., 1985; Shepherd and Brayton, 1987). Subsequently we showed computationally with Ted Carnevale that logic gates were also formed with active properties confined only to the dendritic shaft (Woolf et al., 1989). This work helped stimulate a study by Softky (1994) on exquisite coincidence detection by active spines, and more recently the two-layer network of Poirazi et al. (2003).

The early work on spines was summarized in an invited review (Shepherd, 1996), well before any direct experimental evidence was available. It has been pointed out that these early computational studies from the 1970s to 1990s helped lay the basis for understanding spine functions, a conceptual foundation leading to the dramatic results obtained since the late 1990s by direct microscopic observations linked to new genetic and optical recording approaches.

During this time we didn’t forget granule cell spines. These continued to be, and perhaps still are, the only spines with a specific input-output function: mediation of feedback and lateral inhibition of the mitral cells, as proposed in our model and supported by the experimental evidence. A key question was how the local function of a spine related to the global function of the dendritic tree. To answer this, Tom Woolf carried out a thesis study beginning with the fine structure of the granule cell and its spines with Charlie Greer (Woolf et al., 1990). He generated Golgi-stained granule cells which he simulated computationally, and analyzed how excitatory postsynaptic potentials (EPSPs) in individual spines would summate within the dendritic tree to communicate with each other and generate action potentials in the cell body (Woolf et al., 1991). Finally, he analyzed the movement of Ca++ in and out of a spine (Woolf and Greer, 1992). The study has provided a basis for subsequent experimental analysis of these questions. My review (Shepherd, 1996) listed some 30 possible functions of spines, few as well documented as those of the granule cell.

Olfactory Transduction

By the 1980s we had an idea of how the olfactory receptor cell responses were represented in the activity patterns of the olfactory glomeruli. The next step was to understand the nature of the transduction mechanism in the receptor cells themselves.

As explained earlier, the olfactory bulb for us began as a model for cortical integration, and for the first decade of work in the 1960s I kept that as a focus. However, it was obvious that it was going to be necessary to understand the natural stimulus—odors—for this system. I had hoped to begin this study with Ottoson, but his experimental work was devoted exclusively to the muscle spindle. I then got in touch with David Moulton, the reigning expert on olfactory bulb physiology, who had just joined the new Monell Center for Chemical Senses in Philadelphia, and arranged to spend part of my sabbatical year 1971–1972 at Penn with him. It was another thing I tell my students: always be willing to travel to acquire new methods and expertise.

As the Monell Center was getting off the ground, it was exciting to interact with Morley Kare, and with Tom and Marilyn Getchell just arrived from Northwestern, and John Kauer and Michael Meredith as graduate students with Moulton. Tom had just carried out studies of olfactory receptor cell responses with Bob Gesteland, using the new carbon-coated electrode for this purpose, and Marilyn had carried out the first studies of the nature of the olfactory receptors using protein-blocking agents.

The most important result of my visit was that Tom elected to withdraw from his faculty position at Penn and join the lab as a postdoctoral fellow for further electrophysiological training. Together we carried out the study of the glomerular responses mentioned earlier. John soon joined the lab too. We further developed his system of quantitatively controlled odor stimulation through a solenoid-triggered three-concentric nozzle device, which allowed step pulses of odor to be delivered and cleared from the head space over the exposed epithelium. The result was one of the first classifications of olfactory bulb odor responses, into excitatory, excitatory-inhibitory, and inhibitory responses (Kauer and Shepherd, 1976).

Tom then used this step-pulse nozzle system to analyze responses of salamander olfactory receptor cells (Getchell and Shepherd, 1978a, 1978b). This showed that there is a response latency of several hundred milliseconds, and that virtually all the responses were excitatory. The mainly excitatory responses were an important step away from the bewildering variety and complexity of receptor cell odor responses that had been reported up to then. This was confirmed by subsequent intracellular and patch recordings in vertebrate receptor cells. The long latency was eventually explained by the second messenger cascade activated by the G-protein coupled receptors.

The next step was to develop an isolated epithelial preparation, which was undertaken with John and new recruits Leona Masukawa and Britta Hedlund. This resulted in several papers, showing the high input resistance of receptor cells, which would make them extremely sensitive to low levels of odor concentration, and the low input resistance of supporting cells due to high K conductance and gap junctions between them (Masukawa et al., 1985). A study of patch recordings of the receptor cells to odor stimuli was begun by an undergraduate, Jessica Hopfield, which produced some of the first patch recordings in the receptor cells. On this basis, I suggested to Jeff Gold, a retinal physiologist at Yale, that we should collaborate on carrying forward this project.

My interest in the nature of the olfactory receptors had been piqued by many stimulating conversations with Doron Lancet. He had come from a background of molecular immunology, with the long-term goal of attacking this problem. Before he left the lab in 1981 I made him compose a list of comparisons between the immunoglobulins and the predicted olfactory receptors. That list hangs in the lab today, with the key prediction that the receptors would be numerous in number. After setting up his own lab in Israel, Doron took the first step into the modern era of olfactory receptors by showing that a cell-free preparation of the cilia was stimulated by odors to produce cAMP, suggesting a G-protein coupled receptor activating a cAMP second messenger cascade (Pace et al., 1985).

Nature asked me to write a commentary, where I thought it would be useful to compare this proposed cascade with the cyclic G cascade that had just been shown in photoreceptors by Fesenko. In consultation with Jeff, I suggested that the olfactory receptors could lead to activation of the sensory channel either by adenylate cyclase or by cyclic AMP itself. To my knowledge, it was the first explicit suggestion of this mechanism. Jeff then carried out the study with his student Nakamura confirming this prediction that cyclic AMP directly activates a cyclic nucleotide gated channel (Nakamura and Gold, 1987); they kindly acknowledged I had stimulated them to do the study.

The race was then on to identify the receptor. The route lay through the intermediates of the cascade, identified in outstanding studies in several laboratories, those of Doron, Randy Reed, and Benjamin Kaupp. This was biochemical work outside our own expertise. However, we continued to be interested in the physiological approach, which received a big push when Stuart Firestein came to the lab. Stuart had trained in a retinal lab with one of the pioneers of retina functional organization, Frank Werblin, and had just obtained the first odor responses, recorded with patch pipettes in salamander receptor cells. He joined the lab in the late 1980s. The first study with Stuart showed the time course of the receptor current in response to odor applied directly to the cilia; this was the first demonstration that the cilia are the site of odor transduction. Stuart was on the lookout for others to join in the fun, and soon Frank Zufall from Hans Hatt’s lab in Munich and then Terese Leinders-Zufall arrived to launch a new era of work on odor transduction. We had just begun with the first characterization of the pharmacological properties of the second messenger pathway (Darrow et al., 1990) and the membrane properties of the cyclic nucleotide gated channels (Firestein et al., 1991) when, in 1991, Buck and Axel reported the finding of a large family of G-protein coupled receptors (GPRCs) that appeared to be the long-sought olfactory receptors. We immediately began interacting with Richard, who visited the lab in February, and with Linda, who made her first trip to AChemS in April.

Although there was much excitement over the discovery, there was initially no functional evidence that these receptors were odor sensitive. Furthermore, they showed up in other tissues, especially testes. However, the receptors were received positively by the olfactory community largely because they fit with several expectations. First, they were a large family, as predicted by Doron. They belonged to the GPCR family, as predicted by the studies of the components of the cascade. They provided a binding pocket similar to that of other GPCRs, as indicated by studies by Catherine Strader. I had discussed these possibilities in my Wright lectures in Vancouver in 1987, and subsequently in a conference on the olfactory bulb as a model system in 1990, published in 1991. Later that year Stuart and I attended a conference in Paris on olfactory transduction, in which we together with Doron introduced the idea that a single cell could express a single receptor with a broad response spectrum. Stuart and I also suggested that a new pharmacology of the receptors could arise with characterization of odor agonists and antagonists. The first idea has become one of the cornerstones of the molecular biology of olfaction (all the credit to the brilliant experiments of Axel and Buck and others); the second is being pursued by Stuart and several laboratories for its possible contribution to complex processing at the transduction level.

Expression of the receptors in heterologous cell systems immediately was pursued by several laboratories, but with no success. This turned out to be an exasperatingly difficult problem, due apparently to the receptors hanging up in the endoplasmic reticulum on their way to the membrane. To obtain evidence regarding the functional nature of the receptors, we carried out a study based on a report many years previously by Frank Margolis and subsequently documented by us (Hedlund and Shepherd, 1985) that a cholinergic blocker could bind selectively to the olfactory epithelium. We found that the receptor potentials were blocked by cholinergic antagonists, but not by other neurotransmitter receptor blockers (Firestein and Shepherd, 1992). This appeared to be the first physiological evidence for the GPCR nature of the olfactory receptors.

Stuart and Frank, soon joined by Trese, produced a series of fundamental studies of the odor transduction mechanism. This included inhibition of the CNG channels by intracellular calcium (Zufall et al., 1991), voltage-dependence of the odor response (Firestein and Shepherd, 1995), and modulation of the CNG channels by carbon monoxide (Leinders-Zufall et al., 1995) and by cyclic GMP (Leinders-Zufall et al., 1996). Charlie Greer, established with his own laboratory as head of research in neurosurgery, joined us to identify odor-induced calcium transients in single olfactory cilia (Leinders-Zufall et al., 1997, 1998). Trese’s key role in these experiments is obvious.

By then these guys were moving on to new faculty positions. Before leaving, an outstanding graduate student, Haixing Zhao, joined Stuart; with John Carlson they set out to obtain physiological evidence that the olfactory receptors were really odor receptors. The project moved with Stuart when he took up his new position at Columbia, where they used transfection with adenovirus to show that the I7 receptor was sensitive to octanal and related aldehydes (Zhao et al., 1998). This landmark study opened up the new field of olfactory receptor physiology. John has gone on to become a leader in insect olfaction.

Minghong Ma, who trained with John Koester at Columbia, joined the lab in the late 1990s to carry on the physiological study of the receptors. Most studies to that date, including our own, had been done on freshly dissociated cells. To develop a more physiological prep, and one that would retain the anatomical relations between the cells, we developed an in vitro preparation of the olfactory epithelium, a segment of epithelium we called a “swatch” (like a swatch of cloth) (Ma et al., 1999). Utilizing both patch recordings from the receptor knobs and Ca++ imaging, Minghong characterized the preferential cell responses within populations of up to several hundred cells (Ma and Shepherd, 2000). With a new postdoctoral fellow, Xavier Grosmaitre from Paris, she next characterized for the first time the response properties of cells in the septal organ (Ma et al., 2003). This led to a collaboration with Anne Vassalli and Peter Mombaerts, using swatches from genetargeted mice to characterize the odor specificity of the MOR23 olfactory receptor (Grosmaitre et al., 2006), work completed after Minghong had moved to her new position at Penn. According to Peter, it was the first demonstration of the physiological properties of a singly expressed olfactory receptor.

Our saga with the receptors had an additional chapter. In a discussion with a modeler, Ralph Linster, in the early 1980s, I suggested a collaboration on a model of olfactory encoding, to which he replied: “To get started, what are the primitives?” I had to admit nobody knew. I began to discuss this in a short review given to AChemS in 1985, entitled “A Molecular Vocabulary for Olfaction,” which involved comparisons between the immune and olfactory systems along the lines of my discussions with Doron. The primitives of the olfactory molecules appeared to be individual atoms, much smaller than the amino acids and peptides of immune antigens. In analogy with pharmacological determinants, I suggested we call them determinants or odotopes, to distinguish them from the much larger immune epitopes. In the end, it is probably best to call them determinants.

With the discovery of the receptors, and assuming expression data would soon follow, I initiated a computational modeling study with an outstanding Yale undergraduate, Michael Singer. This was focused on answering the question about the primitives of the odor stimulus: how is the information contained in the odor molecule transferred to the olfactory receptors? The receptor model was built on the rhodopsin coordinates. The first results showed a close correlation with the expression data of Heinz Breer for the O5 receptor (Singer and Shepherd, 1994). Subsequent studies explored the nature of the odor molecule–odor receptor interaction. Michael’s study of I7 gave a close fit with the experimental data of Firestein and Zhao (Singer, 2000). Another study with Bill Goddard’s dynamic modeling group at CalTech gave close correlations with other receptors (Floriano et al., 2000).

Without strong expression data these modeling studies were another example of a methodology preceding the means to utilize the results. Nonetheless, it gave us a clear idea that the primitives of the olfactory system are the determinants of the odor molecules that are transduced by their interactions with specific amino acid residues within the binding pocket of the receptors. It is a working hypothesis that continues to be useful in current studies by many new laboratories drawn to this great challenge in receptor biology.

Olfactory Bulb Dendritic Physiology Again

In the early 1990s we again took up the physiology of olfactory bulb dendrites. Paul Trombley, from Gary Westbrook’s lab, joined us to carry out several studies of synaptic interactions between olfactory bulb cells in tissue culture. We then carried out a study on our old friend, the isolated olfactory bulb of the turtle. Amazing as it is, at that late date the neurotransmitter of the olfactory receptor cell axons was still unknown. David Berkowicz and Paul used the isolated turtle olfactory bulb to demonstrate for the first time that glutamate is the neurotransmitter of the olfactory nerves onto the mitral cells (Berkowicz et al., 1994).

During the late 1980s and early 1990s I began receiving increasing inquiries from Chinese students to join the lab, which ran up against my policy to interview all candidates, or have a colleague I could consult who knew the candidate. The opportunity to meet colleagues in China came with a trip to Japan in 1993, to which we added a week in China. Grethe and I were warmly received in Beijing by Renji Zhang. He gave us a guided tour of the Great Wall, and he and his wife Lily and daughter entertained us in their home. With Xiaocheng Gu we toured the Secret City and Tiananmen Square. We then visited the Brain Institute in Shanghai, hosted by Ching Ping Wu, who had studied with Charles Phillips in Oxford soon after I left. I gave a chalk talk to a large group of graduate students, led by one of them, Wei Chen. Getting to know the great Chinese electrophysiologist Hsiang-Tung Chang was especially memorable.

Among all the students I met, Wei made the strongest impression. Fortunately, he soon wrote me inquiring about a postdoctoral position and joined us in 1994. After a year of trying several different projects in the lab, he came to me one day and said: “Gordon, I have decided to devote my career to the olfactory bulb.” It was the same spirit in which I had made a similar decision in 1959.

Our first task was to develop a tissue slice of the rat olfactory bulb, which we did building on our experience with the in vitro turtle bulb and the recent introduction of the rat olfactory bulb slice by Nickell and Shipley. Wei first carried out a study characterizing some membrane and synaptic properties of mitral cells (Chen and Shepherd, 1997). About that time it was reported, using the new dual patch technique, that action potential initiation in the initial axonal segment, with backpropagation into the dendrites, is the rule in all nerve cells. However, Per Andersen had provided extracellular evidence back in the late 1950s that forward spike propagation occurs in hippocampal dendrites. With its synaptic excitatory input confined to the most distal dendritic tuft, the mitral cell was the perfect model to test the rule. Joined by my colleague Jens Midtgaard from Copenhagen, Wei carried out dual patch recordings and determined that the rule held at low levels of distal dendritic activation, but the initiation site shifted toward the distal site with higher levels. The report was published in Science (Chen et al., 1997) and stimulated a number of studies in other systems, with similar results. We subsequently carried out a computational study with Gongyu Shen and Michael Hines in which we could precisely model this shift (Shen et al., 1999). A further study showed how the site could shift back and forth in a “ping-pong” fashion, also modeled computationally (Chen et al., 2002).

Wei then turned to the dendrodendritic synaptic interactions. Using caged glutamate, he and Wenhui Xiong obtained evidence that the release of GABA from the granule cell spine onto mitral cell lateral dendrites could occur in the absence of voltage-gated Ca channels, suggesting that the Ca++ for vesicle release came from the influx into the spine due to the neighboring dendrodendritic excitatory synapse from the lateral dendrite (Chen et al., 2000). This innovative finding also stimulated follow-up studies from other laboratories.

A question unresolved since our original dendrodendritic model was whether the action potential generated at the cell body of the mitral cell spreads into the lateral dendrites passively or by active invasion. Wei and Wenhui attacked this problem with brilliant results: with patch recordings and Ca++ imaging they showed that the action potential could spread through the entire lateral dendrite, up to a millimeter in length (Chen and Xiong, 2002). They also showed that the invasion could be blocked by stimulating at a point in the granule cell layer. This also gave rise to follow-up experiments in other laboratories, suggesting that the amount of invasion is controlled by the amount of feedback inhibition along the way. This finding had great significance in showing how long distance communication could occur within the olfactory bulb microcircuit.

With Wei in the lab we could rely on a steady stream of students from the best schools in China. Wei seemed to know them all! Changping Jia came to study the synaptic organization of the rat accessory olfactory bulb (Jia et al., 1999). Gongyu Shen carried out the detailed mitral cell modeling mentioned earlier. Zhishang Zhou analyzed dendritic excitability and Ca++ signaling in the mitral cell dendritic tuft (Zhou et al., 2006) and plateau potentials in juxtaglomerular cells (Zhou et al., 2006). For building our two-photon setup Andong Xia joined us from China for several extended stays. After Wei had become an assistant professor in neurobiology, Max Fletcher from Don Wilson’s lab and Shin Nagayama from Kensaku Mori’s lab joined our combined labs, introducing new methods for visualization of activated dendrites in the glomerulus. After 14 fruitful years, Wei moved on to join the faculty at the University of Texas in Houston, in 2008.

Odor Mapping with High-Resolution Functional Magnetic Resonance Imaging

Our odor mapping studies during the 1970s and early 1980s were exciting in opening a new field of study, but they were also frustrating, because the 2DG patterns were another example of a discovery predating the technological means to exploit it. In particular, pseudo-color representation of spatial patterns was not generally available until the 1990s. More efficient activity markers operating over shorter time periods were also needed. In the early 1980s John Kauer and I advised Larry Cohen and his colleagues on launching the use of voltage-sensitive dyes for this purpose, which John then used to great advantage in the salamander. Being optically based, observations were limited to the dorsal surface of the olfactory bulb, which John exploited brilliantly in the salamander because of the way the laminae open onto the dorsal surface. In the 1990s other optical methods were introduced, especially intrinsic imaging and Ca imaging, both providing what appeared to be glomerular resolution.

I was eager to take up our study of odor maps again, but was looking especially for a successor to 2DG that would allow multiple trials of different odors in the same animal, with labeling throughout the glomerular layer, at a glomerular resolution. I had been impressed with the resolution down to 10 micron pixels in anatomical magnetic resonance imaging (MRI) images of the brain in rodents. Fortunately we had a leading center for fMRI at Yale, so Charlie Greer and I went to Bob Shulman and Doug Rothman to ask whether they would be interested in a collaboration on the olfactory bulb using functional imaging. They certainly would! And they showed us a recent result of imaging a single activated barrel in barrel cortex in the rat. They brought great enthusiasm and consummate expertise to the project. Our initial study showed patterns centered on the glomerular layer similar to those with 2DG (Yang et al., 1998). At this point Fuqiang Xu joined the lab from Tim McClintock’s lab in Kentucky and worked with Fahmeed Hyder and the Shulman team to demonstrate resolution at the single glomerular level using a 7.4 Tesla magnet.

Fuqiang and I pursued the odor mapping project, focusing on mice with a view to bringing in gene-targeted animals eventually. The mouse olfactory bulb is a very small structure, but Fuqiang succeeded in getting laminar resolution, which enabled us to delimit the olfactory glomerular layer in each slab and reconstruct the entire glomerular BOLD pattern for a given odor stimulus. Our first study showed that an aldehyde series from C4 to C8 produced extensive glomerular activity patterns which were overlapping but different, confirming the basic properties we had identified with 2DG back in the late 1970s, but all trials in the same animal and at shorter odor exposures (Xu et al., 2003). It also confirmed that the main activity for many odor stimuli is in the medial and lateral aspects of the olfactory bulb.

We next asked whether so-called pheromones activate only the accessory olfactory bulb, a common belief in the field that I had long doubted. Fuqiang, with Diego Restrepo and his student Michelle Schaefer in Denver, carried out these experiments beautifully, showing that a “pheromone” molecule could activate the main olfactory bulb as well as the accessory olfactory bulb, and ordinary odor molecules could also do both (Xu et al., 2005). This was consistent with several other studies then and subsequently. This has further significance in implying that humans also process “pheromone” odors through their main olfactory bulb, because we lack a functional adult vomeronasal organ (see Commentary in Shepherd, 2006).

In revealing the patterns where the responses are strongest, on the medial and lateral surfaces, the results provide a necessary complement to the more easily obtained, but weaker, optical activity of the dorsal glomeruli. Fuqiang achieved recognition for his work when he returned to China in 2008 as one of the select “100 outstanding young scientists” of China.

It was particularly rewarding to have olfactory studies contribute to the development of high-resolution fMRI, pushing from 7 to 9 and 11 Tesla magnets and beyond. Olfactory studies should be able to continue to play this role in the future, aiming at glomerular spatial resolution and subsecond time resolution.

Lateral Connectivity and Distributed Dendrodendritic Inhibition

The fMRI patterns left no doubt that odor stimulation leads to extensive activation in the glomerular layer. This posed the problem of how lateral inhibition mediated by granule cells could operate over such spread-out patterns.

A possible mechanism emerged from a project by postdoctoral fellow David Willhite involving tracing connectivity in the olfactory bulb using pseudorabies virus. The expectation had been that following an injection in the glomerular layer one would see diffuse labeling within the mitral and granule cell populations around the injection site. Surprisingly, discrete columns of labeled cells were seen, widely distributed in a mosaic pattern (Willhite et al., 2006). An individual column appeared to be centered on a single glomerulus, suggesting a “glomerular unit,” each unit containing the granule cells synaptically connected to the mitral cells connected to the single glomerulus. Though connectivity induced by the virus cannot be ruled out, the formation of the columnar pattern remains unique. The functional implication is that lateral inhibition could be mediated through these distributed connections, in contrast to a local center-surround organization.

There was no precedent for this type of organization. As it happened, independent support for this new idea came from a computational modeling study carried out by Michele Migliore. Michele had begun to collaborate with us on analyzing dendritic active properties in the early 2000s, coauthoring two reviews on comparing integrative properties of dendrites across different neuron types (Migliore and Shepherd, 2002, 2005). We then launched a computational study to begin to build a model of the mitral-granule processing network, building on the Shen 1999 mitral cell model and adding a granule cell model. We purposely began with a reduced three-mitral-cell model, in order to work through all the possible constraints on the network. In doing so, Michele reported that the only way to get strong lateral inhibition over long distances was to have the granule cells activated by action potentials propagating throughout the length of the mitral cell lateral dendrites, which of course was just what Chen and Xiong (2002) had shown.

It was another “aha” moment, bringing together the experimental and computational results with the connectivity findings to adapt our original model to provide for distributed lateral inhibition in the processing of distributed odor images. Keeping up traditions, this new model was rejected when submitted for publication, forming a kind of bookend to the rejection of the original model 40 years earlier, as noted earlier. It was finally published (Migliore and Shepherd, 2007), initiating a series of studies still in progress on scaling up to a full realistic simulation of the mitral-granule cell interactions. Combined with the evidence for the determinants transduced by the binding pocket of the olfactory receptors, and the basic circuit of the olfactory cortex for a content-addressable representation of the images, one has a logical sequence for understanding the neural basis of the perception of smell up to orbitofrontal cortex, as earlier hypothesized (Shepherd, 1991).

Human Smell and Human Evolution

In the 1980s I was asked for a quote for the National Geographic article on smell, and I began to think about how our animal research related to human smell. During a sabbatical with Jacques Glowinski at the College de France in Paris, I became acquainted with Jean-Didier Vincent and through him came my first contacts with French wine producers and connoisseurs. This led to participation in a French radio program on smell by Jean-Didier and Alan Prochiantz in the early 2000s; several interactions with the wine industry, including private tastings at Petrus and Château d’Yquem (heady stuff for a kid from Iowa); and participation in several international meetings on food and flavor. The field of olfaction had been focused on orthonasal smell produced by sniffing in, but taste physiologists like Bruce Halpern and flavor physiologists like Terry Acree and Andrew Taylor knew about food in the mouth as the source of flavor, and they knew that most of flavor is due to smell, specifically retronasal smell, by breathing out through the nasopharynx. When this message sank in, I became convinced that the olfactory field had been missing the importance of smell for humans; it was retronasal, not orthonasal, smell. The problem was that the smell component in flavor is almost entirely hidden, and ascribed to “taste” because it appears to come from the mouth.

At the Weurmann Flavor Research Symposium in 2001, I suggested that odor images are formed in humans, that these must play an important role in the perception of human flavor, and that smell must therefore have played an important role in the evolution of human cuisines. This was directly opposed to the traditional view of the decline of smell during human evolution, which appeared to be confirmed by the research on the olfactory receptor genes, which showed that the number of functional olfactory receptor genes declined in number within vertebrates from over 1000 in rodents to only 350 in humans. This assumed that our sensory and cognitive capacities are determined by our peripheral receptors. But a better hypothesis is that the enormous overgrowth of the cerebral cortex during evolution endowed the human with an accordingly enhanced ability for complex processing of its inputs, including the elaboration of much more complex flavors by humans compared with other species.

During this time Richard Wrangham was developing his well-known theory that the early control of fire enabled a complex cuisine that played a large role in the enhanced nutrition that literally fueled the larger brain of Homo erectus. He kindly invited me to give a seminar at the Harvard anthropology department in 2003 where I presented my hypothesis. This was developed in an article for PLoS Biology in 2004 entitled “The Human Sense of Smell: Is It Better Than We Think?” My colleague Avery Gilbert sent me an amusing e-mail with the comment that what I really meant was: “The human sense of smell: is it better because we think?” That was exactly the point! Support for this idea soon came from human fMRI experiments by Dana Small, showing that combined taste and retronasal smell stimuli recruited additional association cortical areas. Odor images and the extensive brain regions involved in flavor perception were brought together in an Insight article for Nature in 2006 entitled “Odor Images and the Flavor System of the Human Brain.”

Obviously, the role of the olfactory system needs to be reassessed for its importance in primate and humans. A pioneer has been Matthias Laska, who spent several years with us as a visiting scientist. His earlier results in the monkey suggested that primates, including humans, should be classified as “macrosmats” rather than “microsmats” (and this was only for orthonasal smell). This reassessment needs to be extended not by simple measures of sizes of different regions, but rather by the increasing knowledge of genetic makeup, microcircuit organization, brain imaging, and behavioral testing. A major challenge in food science as well as for any theory of the role of nutrition in evolution is therefore to understand the relation between the brain, the flavor of a food, and its nutritive value. This new field could be called “neurogastronomy”.

Neuroinformatics

Our experience over the years with computational modeling led us into an entirely new field. In the 1980s molecular biology surged forward, critically aided by the gene and protein databases produced by the new field of bioinformatics. Neuroscience in this respect remained a digital backwater. The Institute of Medicine formed a committee in 1990 to bring neuroscience into the new age, chaired by Joseph Martin. Among the working groups, I cochaired with Vint Cerf, an Internet pioneer, a subcommittee on databases for cell structure and function. The final report was entitled Mapping the Brain and Its Functions: Integrating Enabling Technologies into Neuroscience Research (Pechura and Martin, 1991). Discussions began on a funding program to create a new field of neuroinformatics. Several of us urged that it be called the “Human Brain Project,” with a vision of transforming neuroscience in the way the “Human Genome Project” was transforming molecular biology.

The program started in 1993, with a dozen or so laboratories among the first funded. We had a great advantage at Yale in Perry Miller, who had set up a Yale Center for Medical Informatics in the 1980s to support research in molecular biology. He and I had interacted a bit before, and he enthusiastically joined the new effort. We entitled our grant “SenseLab: Integrating Multidisciplinary Sensory Data,” with the aim of creating databases of neuronal data to support building computational models to aid experimental analysis of olfactory cells and circuits, with extension to other brain regions as well.

We began by responding to a request by several labs to provide a database to assist them in cloning and sequencing the thousand or more olfactory receptor genes. Thus was created Olfactory Receptor Database (ORDB). With the completion of the Human Genome Project around 2000, several labs produced their own terminology, with different nomenclatures for the same genes. This problem was discussed at a meeting at Cold Spring Harbor in 1991 on the “Molecular Biology of Chemosensory Receptors: The First Decade.” The recommendation was for ORDB to organize the several nomenclature schemes so that the different names could be identified for the same gene/protein. Michael Singer and Chiquito Crasto took responsibility for initiating this, Chiquito building it up to the present inventory of over 14,000 chemical sensory genes, receiving some 200,000 Internet hits per month.

To support our research on dendrites, we decided to archive key membrane properties: transmitter receptors, membrane channels, and transmitters. For this we invented a format for canonical dendritic trees with proximal, middle, and distal compartments, enabling identification of the combinations of membrane properties that contribute to the integrative operations of a given neuron. A unique tool enabled searches for arbitrary families of properties across neurons, much as blast searches reveal families across sequence banks. The initial construction of this multidomain database was carried out by a recent Yale graduate, Jason Mirsky, with key input from the informatics group (Mirsky et al., 1998). Over the years it has grown to comprise over 30 principal neurons and interneurons in over a dozen key brain regions, receiving some 60,000 hits per month.

In 1996 Michael Hines joined our research group, bringing his deep experience in creating and maintaining the simulation program NEURON. Like all other compartmental approaches to modeling neurons, it was in the direct lineage from Wil Rall’s original methods that we used in our olfactory bulb study. Just as in my work with Wil, I’ve benefited from the quiet expertise that Michael brings to the modeling enterprise, and the focus on interpreting experimental results. Michael made possible two new ventures in SenseLab. One was the opportunity to bring neuron modeling back into the lab, with the results noted earlier. The other was the construction of a new database, ModelDB. This has enabled us to address one of the most critical problems for computational modeling as a field: Models traditionally were constructed and published by a student in the lab, who then moved on in his or her career, so that testing the results by others required creating a new model from scratch, which was rarely done. Without this capability, computational modeling lacked the credentials that every scientific field must have: rapid testing of published results.

For this purpose we created ModelDB. Tom Morse soon joined the lab and took over responsibility for this project. It has grown to comprise over 600 computational models at this writing, with over 100,000 hits per month. Some of the models are of circuits, which have been moved to a new MicrocircuitDB to make them more easily accessible as interest increases in building realistic network models.

As molecular biologists identify genes expressed in different cells, it is convenient to have a database where they can be archived. Cell Properties Database (CellPropDB) was created for that purpose. It is complementary on the one hand to NeuronDB, and on the other to brain atlas databases such as the Allen Brain Atlas, enabling users to determine quickly the types of genes expressed in a given cell type, or to go from CellPropDB to an atlas to see other genes expressed in the cells of that region.

For olfactory research, in addition to ORDB is OdorDB, archiving the range of odors that have been shown to activate different specific olfactory receptors, and OdorMapDB, archiving 2DG and fMRI maps from the lab. The latter was created by postdoctoral fellow Nian Liu, who also built software (OdorMapBuilder and OdorMapComparer) for constructing the odor maps in the work with Fuqiang.

Our most recent project is a new database called BrainPharm, aimed at expanding NeuronDB to include molecular properties involved in neurological disorders such as Alzheimer’s disease.

The early years of the Human Brain Project involved a struggle for recognition. The director, Steve Koslow, organized numerous panels at national and international meetings to spread the word about the importance of sharing data in common databases but experimental neuroscientists were skeptical; at some meetings we panelists outnumbered the audience! A big boost came in 2004 when Huda Akil made neuroinformatics a signature focus of her presidency of the Society for Neuroscience. It came at a propitious time when, after a decade, the HBP was folding. In its place was put the Neuroscience Database Gateway (NDG), initiated by our SenseLab project, that was a portal to all the HBP project Web sites. This in turn led to an NIH Blueprint program funded by NIDA called the Neuroscience Information Framework (NIF), chaired first by Dan Gardner of Cornell and currently by Maryann Martone of San Diego. SenseLab is one of the five groups charged with creating this portal to the extraordinary range of neuroscience data. Also supporting the growth of neuroinformatics and data sharing is the International Neuroinformatics Coordinating Facility (INCF) in Stockholm, in which we also play a part.

At this stage in my career, focusing on the spread of effective databases in support of neuroscience research seems like one of the most important contributions I can make. Sharing data is at the heart of the collegiality I believe is essential for the scientific enterprise. Its effectiveness is shown by the rise of molecular biology; we need that same spirit for a surge in shared data in neuroscience to achieve an integrated understanding of brain and mind.

Cognitive Neuroscience

In 1984 the McDonnell Foundation convened a meeting to discuss how to support the formation of a new field of cognitive neuroscience. We recommended starting by setting up a summer school in the subject, expecting a couple of dozen students. Over 300 applied! The first summer school was held at Harvard, with the course directors Steve Kosslyn, Michel Posner, and myself. We continued to put on the summer school over the next 4 years at Dartmouth, hosted by Michael Gazzaniga, with similarly high numbers of students. I’m still meeting cognitive neuroscientists who remember that summer school as the start of their careers in the new field.

History of Neuroscience

Notwithstanding my father’s injunction against being distracted by history, I had developed a deep interest in the historical origins of neuroscience from my first encounter with Cajal in Oxford. In 1985 I suggested to then Society for Neuroscience president, Bill Willis, that the society should have a committee on the history of neuroscience led by neuroscientists themselves. I was joined by Ted Jones in presenting the proposal at the next council meeting, which, after a vigorous debate, led to setting up a Committee on the History of Neuroscience, with myself as the first chair, followed by Ted. The annual Lecture in the History of Neuroscience was first given in 1985 by Julius Axelrod, which completely bowled us (and Julie) over by attracting an audience of some 2000. The lectures have continued to be among the most popular at the meetings, belying the received wisdom that modern young neuroscientists aren’t interested in anything more than a week old! The present series of autobiographies under Larry Squire continues that tradition.

Conceptual Challenges

The focus in this account has been on the original research, experimental and computational, that has driven the work of the lab. Part of the fun of doing the research has been to see how it can enlarge the conceptual basis of our understanding of brain function.

The implications of our dendrodendritic study for revising the neuron doctrine led to stimulating interactions with Sandy Palay, Ted Bullock, and others. My review on this subject, published in 1971 in the Yale Journal of Biology and Medicine, not what one would now call a high-profile journal, nonetheless brought over 500 reprint requests! This led to a full account in 1991 of the classical work in Foundations of the Neuron Doctrine on the centenary of Waldeyer’s original review in 1991. (Some have assumed that I was blindly supporting the neuron doctrine; rather, I was laying out its full history in order to suggest how to revise it, as was done in the final chapter).

In 1985 a volume was published to celebrate the career of Carl Pfaffman. I used the opportunity to suggest the idea that the glomerulus constitutes a “labeled line,” albeit a broadly tuned one, in odor processing (most believed that a labeled line had to be responsive to only one ligand).

I’m not a Proust scholar, but you can’t work on the olfactory system and avoid him. The more I had read the famous passage about the instant memory evoked by the cookie and the cup of tea, the more I doubted it. The result was an essay with a scholar of modern English literature which pointed out that in fact it took Proust a page and a half of concerted effort to dredge up the memory from the past. We provided the reader with a tour of the brain pathways and mechanisms that would have been involved (Shepherd and Shepherd-Barr, 1989, 2009).

My work with Wil Rall instilled a lifelong commitment to realistic modeling of nerve cells and circuits. A direct challenge was neural networks, which came on the scene in the 1980s. John Hopfield sought me out to discuss his new approach at the same time that David Rumelhart and Jay McClelland were popularizing parallel circuits. My response has been that devices that can simulate functions similar to those of the nervous system are greatly to be welcomed, for their practical use and for the insights they can give into functions at the system level. However, networks that represent nerve cells as simple nodes with all-to-all connectivity are extremely un-neural in their architecture, as explained in a review (Shepherd, 1989) and numerous talks since. The power of the brain lies in the computational depth of its dendrites and microcircuits. When these get incorporated into neural nets, the revolution will really start!

In addition to introducing new concepts, one also has the opportunity to introduce new terms required by one’s research. “Dendrodendritic synapses,” “odor images,” and “microcircuits” seem to have entered the general vocubulary; perhaps “human brain flavor system” and “neurogas-tronomy” will too! New fields to which this work has contributed have included computational models of dendrites, dendritic spines, dendroden-dritic synapses, odor images, olfactory receptor models, synaptic organization, microcircuits, and neuroinformatics.

Books

With so many challenges in the lab, one may wonder why one would take out time to write books. However, it’s been a particular privilege to be able to publish several books giving new syntheses of our own and others’ work. Most have been with Oxford University Press, starting with my editor and long-time friend Jeffrey House in 1974, and including Fiona Stevens and recently Craig Panner.

The Synaptic Organization of the Brain (1974) as noted was based on a course on the newly breaking studies, taught while a visiting professor at Penn in 1972. I began teaching the subject as a graduate course at Yale in 1976 and have just finished using the fifth edition to teach the most recent class 34 years later. Neurobiology (1983) was written to introduce undergraduate students to the new ways of understanding the functional organization of the brain. Although not dislodging Kandel et al. from its well-deserved popularity, the book nonetheless has been translated into five languages, and the third edition is still being sold. Foundations of the Neuron Doctrine (1991) was my homage to all the classical histologists I studied in my early work at Oxford, with much help from Grethe on the translations. Creating Modern Neuroscience: The Revolutionary 1950s (2010) has been my tribute to all my teachers, colleagues, and other great figures from the 1950s. The collected papers of Wilfrid Rall, with commentaries by his colleagues, was published as Theoretical Foundation of Dendritic Function (1995) with coeditors Idan Segev and John Rinzel. Handbook of Brain Micro-circuits (2010), coedited with Sten Grillner, is the continuance of the main message in The Synaptic Organization of the Brain, distilled to focus on basic microcircuits and extended to over 50 brain regions.

Various Offices

A scientist rightly tithes time to various offices to support his or her field. My efforts included various contributions. The main ones were 6 years as editor-in-chief of the Journal of Neurophysiology, followed by the same office for 4 years for the Journal of Neuroscience. The former occurred as e-mail was becoming widespread, the latter as the Internet age began, so the times were exciting. My main focus in running a journal was getting quality editors who in turn get the reviewers who are the best possible fit with the subject matter of the article. Given a good fit, collegial criticism will bring the field forward in the best possible way.

At Yale, my main contributions were as director of medical studies for our department, followed by director of graduate studies for the nascent Interdepartmental Neuroscience Program, followed by Deputy Provost for Biomedical Sciences. The latter provided fascinating experience and insights into the governance of a university. I enjoyed the job greatly, while at the same time was relieved to return unscathed to the lab! Bart Giamatti once asked me to be master of Pierson College, which would have been stimulating, but too much of a diversion from the lab.

Among other duties, serving as advisor to programs and institutions in the United Kingdom, France, Germany, Denmark, Sweden, and Switzerland, as well as in the United States, has been particularly interesting and I hope useful.

Friends and Awards

The rewards of a life of research have been in having many great colleagues and in enjoying the intellectual stimulation of opening new fields. The additional awards listed at the start of this essay have been icing on the cake, for which I am grateful to the brave souls who put up my name for them. Visiting appointments have been especially rewarding. Warm friends and colleagues around the world, in addition to those already mentioned, have been Pierre-Marie Lledo, Alain Prochiantz, JacSue and Phillip Ascher, Serge Charpak, and Henri Korn in Paris, Tomas Høkfelt in Stockholm, and Yoshi Yoshihara in Japan. Among the recognition, I especially appreciated the honorary degrees in Copenhagen, reflecting my connection through Grethe and to colleagues in Denmark, and Pavia, reflecting my connection to the origins of neuroscience and to Golgi, through Paolo Mazzarello, Golgi’s outstanding biographer.

Family

An active life running a lab and writing has to be balanced with family life. Grethe, a reference librarian and gardener, has made it all possible, maintaining our homes in Hamden and Toftum and leading us all with the right values. Gordon M. G. is making his own career in neuroscience at Northwestern. Kirsten is a don at Oxford in English literature and theater. Lisbeth cofounded Unis-Cité, a youth service corps in France, and now runs a green nonprofit in the U.S.. The ideals that they and their spouses and our seven grandchildren live by give hope for the future.

I’ve also had plenty of stimulation from my four younger siblings. Geoffrey has published 15 books in economics and Margaret 17 as a calligrapher; I’m still trying to catch up! Alison was chief of staff to the Alameda County CA Supervisor for many years. Doug was a caring husband and father, bravely battling asthma all his life.

Also close to me growing up were cousin Dave Murray, who became President of the American College of Surgeons, and Jean Murray Sutherland, Elizabethan scholar and a pillar of strength as her husband Tom survived 6 years as a hostage in Lebanon, which helps to put one’s own strivings in perspective.

Students

It seems appropriate to end this essay with one of the most important contributions a lab can make, as a training site for the next generation of scientists. I was hugely fortunate in the talented young people who joined me. There were two rules in taking them on. I took responsibility for mentoring them toward independent positions when they left, and they were free to pursue whatever subjects they wished, including what they had worked on in the lab. As a result, I’ve had great times with a growing family of colleagues. The reward has been to see them make successful lives in neuroscience as well as other walks of life. The list speaks for itself. I thank them all.

On my 75th birthday some 80 students, collaborators, family, and friends gathered from 11 countries for an all-day symposium. It was the best lab meeting ever!

Students

Graduate Students

1967–1971

Lewis Haberly, Ph.D.

1969–1972

Lanay Jordan Land, Ph.D.

1985–1990

Thomas Woolf, Ph.D.

1986–1990

Ben Strowbridge, Ph.D.

1991–1994

David Berkowicz

1994–1998

Paul Kingston, Ph.D.

1995–2000

Michael Singer, M.D., Ph.D.

2005–2007

Janna Nawroth

2006–2007

Johannes Richter

2006–2009

Arjun Masurkar, M.D., Ph.D.

2007–2009

Aurelie Pala

2007–2011

Matthew Phillips, Ph.D.

Postdoctoral Fellows and Research Associates

1972–1973

Lanay Jordan Land

1973–1974

Thomas V. Getchell

1973–1976

John S. Kauer

1976–1978

William B. Stewart

1977–1982

Martha C. Nowycky

1977–1978

Ulrich Waldow

1978–1980

Kensaku Mori

1978–1981

Charles Greer

1980–1981

Doron Lancet

1981–1985

Patricia Pedersen

1982–1985

Thane Benson

1982–1985

Leona Masukawa

1982–1984

Britta Hedlund

1987–1989

Masato Higashima

1987–1988

Joan Hamilton

1988–1990

Stuart Firestein

1988–1991

Ferenc Pongracz

1990–1991

David Berkowicz

1990–1995

Paul Trombley

1990–1995

Anne Williamson

1990–1997

Frank Zufall

1994–1997

Trese Leinders-Zufall

1994–1996

Bret Peterson

1995

Mark Rand

1996–1999

Emmanouil Skofous

1997–2000

Changping Jia

1994–2000

Wei Chen

1996–2003

Minghong Ma

2000–2001

Andong Xia

2000–2004

Zhishang Zhou

2000–present

Thomas Morse

2001–2002

Buqing Mao

2000–2002

Andrew Davison

2001–2003

Xavier Grosmaitre

2002–2004

Fan Jia

2002–2005

Shaoquin Zeng

2001–2005

Nian Liu

1998–2006

Luis Marenco

1998–2007

Fuqiang Xu

2000–2007

Chiquito Crasto

2003–2010

David Willhite

2005–2008

Shin Nagayama

2005–2008

Max Fletcher

2009–present

Tom McTavish

2011–present

Yuguo Yu

Programmers and Technicians

1996–1998

Jason Mirsky

2002–2003

Jian Liu

2004–2010

Hetal Petal

Yale Undergraduates

1985–1986

Jessica Hopfield

1987–1988

Rob Rosenberg

1988–1989

Pratik Mukherjee

1989–1990

Bruce Darrow

1989–1990

Karen Rosewater

1993–1995

Michael Singer

1995

Winnie Au

1995–1996

Uzman Rabbani

1996–1997

Jason Smith

1999–2000

Jasen Yang

2000–2001

Rishikesh Dalal

2004–2006

Catherine Nguyen

2005–2006

Dipa Joshi

2006–2008

Andrew Chang

2007–2008

Hayley Ryan

2007–2008

Maria Thomas

2008–2010

David Kim Also:

2002–2004

Peter Bail

Visiting Scientists

1980–1981

Norbert Halasz

1981

Burton Slotnick

1982

Dennis Lincoln

1982–1984

Pawel Jastreboff

1983

Norihiko Onoda

1984–1986

Anker Hansen

1985

Hinrich Sass

1996–2000

Jens Midtgaard

1998–2000

Gongyu Shen

1999–2000

Michael Meredith

2001–present

Michele Migliore

2003–2006

Matthias Laska

Selected Bibliography

Articles

Ahmad I., Leinders-Zufall T., Kocsis J.D., Shepherd G.M., Zufall F. and Barnstable C.J. (1994). Retinal ganglion cells express a cGMP-gated cation conductance activatable by nitric oxide donors. Neuron 12: 155–165.

Angelakos E.T. and Shepherd G.M. (1957). Autocorrelation of EKG during ventricular fibrillation. Circ. Res. 5: 657–658.

Benson T.E., Burd G.D., Greer C.A., Landis D.M.D. and Shepherd G.M. (1985). High-resolution 2-deoxyglucose autoradiography in quick-frozen slabs of neonatal rat olfactory bulb. Brain Res. 339: 67–78.

Berkowicz D.A., Trombley P.Q. and Shepherd G.M. (1994). Evidence for glutamate as the olfactory receptor cell neurotransmitter. J. Neurophysiol. 71: 2557–1561.

Carnevale N.T., Woolf T.B. and Shepherd G.M. (1990). Neuron simulations with SABER. J. Neurosci. Methods 33: 135–148.

Chen W., Lee S., Kato K., Spencer D.D., Shepherd G.M. and Williamson A. (1996). Long-term modifications of synaptic efficacy in the human inferior and middle temporal cortex. Proc. Natl. Acad. Sci. 93: 8011–8015.

Chen W.R. and Shepherd G.M. (1997). Membrane and synaptic properties of mitral cells in slices of rat olfactory bulb. Brain Res. 745: 189–196.

Chen W.R., Shen G.Y., Shepherd G.M., Hines M.L. and Midtgaard J. (2002). Multiple modes of action potential initiation and propagation in mitral cell primary dendrite. J. Neurophysiol. 88: 2755–2764.

Chen W.R., Midtgaard J. and Shepherd G.M. (1997). Forward and backward propagation of dendritic impulses and their synaptic control in mitral cells. Science 278: 463–467.

Chen W.R., Xiong W. and Shepherd G.M. (2000). Analysis of relations between NMDA receptors and GABA release at olfactory bulb reciprocal synapses. Neuron 25:625–633.

Crasto C., Marenco L., Miller P. and Shepherd G.M. (2002). Olfactory Receptor Database: a metadata-driven automated population from sources of gene and protein sequences. Nucleic Acids Res. 30: 354–360.

Crasto C., Marenco L.N., Migliore M., Mao B., Nadkarni P.M., Miller P. and Shepherd G.M. (2003). Text mining neuroscience journal articles to populate neuLroscience databases. Neuroinformatics 1: 215–238.

Firestein S. and Shepherd G.M. (1992). Neurotransmitter antagonists block some odor responses in olfactory receptor neurons. NeuroReport 3: 661–664.

Firestein S. and Shepherd G.M. (1995). Interaction of anionic and cationic currents leads to a voltage dependence in the odor response of olfactory receptor neurons. J. Neurophysiol. 73: 562–567.

Firestein S., Darrow B. and Shepherd G.M. (1991). Activation of the sensory current in salamander olfactory receptor neurons depends on a G protein-mediated cAMP second messenger system. Neuron 6: 825–835.

Firestein S., Zufall F. and Shepherd G.M. (1991). Single odor sensitive channels in olfactory receptor neurons are also gated by cyclic nucleotides. J. Neurosci. 11: 3565–3572.

Firestein S., Shepherd G.M. and Werblin F.S. (1990). Time course of the membrane current underlying sensory transduction in salamander olfactory receptor neurones. J. Physiol. (London) 430: 135–158.

Floriano W.B., Vaidehi N., Goddard W.A., Singer M.S. and Shepherd G.M. (2000). Molecular mechanisms underlying differential odor responses of a mouse olfactory receptor. Proc. Natl. Acad. Sci. USA 97: 10712–10716.

Getchell T.V. and Shepherd G.M. (1975). Short-axon cells in the olfactory bulb: dendrodendritic synaptic interactions. J. Physiol. 251: 523–548.

Getchell T.V. and Shepherd G.M. (1975). Synaptic actions on mitral and tufted cells elicited by olfactory nerve volleys in the rabbit. J. Physiol. 251:497–522.

Getchell T.V. and Shepherd G.M. (1978). Adaptive properties of olfactory receptors analysed with odour pulses of varying durations. J. Physiol. 282: 541–560.

Getchell T.V. and Shepherd G.M. (1978). Responses of olfactory receptor cells to step pulses of odour at different concentrations in the salamander. J. Physiol. 282: 512–540.

Greer C.A. and Shepherd G.M. (1982). Mitral cell degeneration and sensory function in the neurological mutant mouse Purkinje Cell Degeneration (PCD). Brain Res. 235: 156–161.

Greer C.A., Mori K. and Shepherd G.M. (1981). Localization of synaptic responses in the in vitro turtle olfactory bulb using the 14C-2-deoxyglucose method. Brain Res. 217: 295–303.

Greer C.A., Stewart W.B., Kauer J.S. and Shepherd G.M. (1981). Topographical and laminar localization of 2-deoxyglucose uptake in rat olfactory bulb induced by electrical stimulation of olfactory nerves. Brain Res. 217: 279–293.

Greer C.A., Stewart W.B., Teicher M.H. and Shepherd G.M. (1982). Functional development of the olfactory bulb and a unique glomerular complex in the neonatal rat. J. Neurosci. 2: 1744–1759.

Grosmaitre, X., Vassalli A., Mombaerts P., Shepherd G.M. and Ma M. (2006). Odorant responses of olfactory sensory neurons expressing the odorant receptor MOR23: a patch clamp analysis in gene-targeted mice. Proc. Natl. Acad. Sci. USA 103: 1970–1975.

Haberly L.B. and Shepherd G.M. (1973). Current density analysis of summed evoked potentials in opposum prepyriform cortex. J. Neurophysiol. 36: 789–802.

Halasz N., Nowycky M., Hokfelt T., Shepherd G.M., Markey K. and Goldstein M. (1982). Dopaminergic periglomerular cells in the turtle olfactory bulb. Brain Res. Bull. 9: 383–389.

Halasz N., Nowycky M.C. and Shepherd G.M. (1983). Autoradiographic analysis of 3H-dopamine and 3H-dopa in the turtle olfactory bulb. Neurosci. 8: 705–715.

Healy M.D., Smith J.E., Singer M.S., Nadkarni P.M., Skoufos E., Miller P.L. and Shepherd G.M. (1997). Olfactory Receptor Database (ORDB): a resource for sharing and analyzing published and unpublished data. Chemical Senses 22: 321–326.

Hedlund B. and Shepherd G.M. (1983). Biochemical studies on muscarinic receptors in the salamander olfactory epithelium. FEBS Letters 162: 428–431.

Hedlund B., Masukawa L.M. and Shepherd G.M. (1987). Excitable properties of olfactory receptor neurons. J. Neurosci. 7: 2338–234.

Jastreboff P.J., Pedersen P.E., Greer C.A., Stewart W.B., Kauer J.S., Benson T.E. and Shepherd G.M. (1984). Specific olfactory receptor populations projecting to identified glomeruli in the rat olfactory bulb. Proc. Natl. Acad. Sci. 81: 5250–5254.

Jia C.P., Chen W.R. and Shepherd G.M. (1999). Synaptic organization and neurotransmitters in the rat accessory olfactory bulb. J. Neurophysiol. 81: 345–355.

Joshi, D., Volkl M., Shepherd G.M. and Laska M. (2006). Olfactory sensitivity for enantiomers and their racemic mixtures—a comparative study in CD-1 mice and spider monkeys. Chem. Senses. 31:655–664.

Kauer J.C. and Shepherd G.M. (1975). Olfactory stimulation with controlled and monitored step pulses of odor. Brain Res. 85: 108–113.

Kauer J.S. and Shepherd G.M. (1977). Analysis of the onset phase of olfactory bulb unit responses to odor pulses in the salamander. J. Physiol. 272:495–516.

Kauer J.S., Reddy D., Duckrow R.B. and Shepherd G.M. (1984). A simplified method for computerized densitometry of complex shapes in 2-deoxyglucose autoradiographs. J. Neurosci. Methods 11: 143–158.

Krieger N.R., Kauer J.S., Shepherd G.M. and Greengard P. (1977). Dopamine-sensitive adenylate cyclase within laminae of the olfactory tubercle. Brain Res. 131: 303–312.

Lancet D., Greer C.A., Kauer J.S. and Shepherd G.M. (1982). Mapping of odor-related neuronal activity in the olfactory bulb by high-resolution 2-deoxyglucose autoradiography. Proc. Natl. Acad. Sci. 79: 670–674.

Lancet D., Kauer J.S., Greer C.A. and Shepherd G.M. (1981). High resolution 2-deoxyglucose localization in olfactory epithelium. Chem. Senses 6: 343–349.

Land L.J. and Shepherd G.M. (1974). Autoradiographic analysis of olfactory receptor projections in the rabbit. Brain Res. 70: 506–510.

Land L.J., Eager R.P. and Shepherd G.M. (1970). Olfactory nerve projections to the olfactory bulb in rabbit: demonstration by means of a simplified ammonacal silver degenerative method. Brain Res. 23: 250–254.

Laska, M. and Shepherd G.M. (2006) Olfactory discrimination ability of CD-1 mice for a large array of enantiomers. Neuroscience. 144:295–301.

Laska M., D. and Joshi Shepherd G.M. (2006). Olfactory sensitivity for aliphatic aldehydes in CD-1 mice. Behav Brain Res. 167: 349–54.

Laska, M. and Joshi D. and G.M. Shepherd (2007). Olfactory discrimination ability of CD-1 mice for aliphatic aldehydes as a function of stimulus concentration. J Comp. Physiol. A. Neuroethol. Sens. Neural Behav. Physiol. 193: 955–961.

Lecoq, J., Tiret P., Najac M., Shepherd G.M., Greer C.A. and Charpak S. (2009). Odor-evoked oxygen consumption by action potential and synaptic transmission in the olfactory bulb. J. Neurosci. 29: 1424–1433.

Leinders-Zufall T., Greer C.A., Shepherd G.M. and Zufall F. (1998). Imaging odor-induced calcium transients in single olfactory cilia: specificity of activation and role in transduction. J. Neurosci. 18: 5630–5639.

Leinders-Zufall T., Shepherd G.M. and Zufall F. (1995). Regulation of cyclic nucleotide-gated channels and membrane excitability in olfactory receptor cells by carbon monoxide. J. Neurophysiol. 74: 1498–1508.

Leinders-Zufall T., Shepherd G.M. and Zufall F. (1996). Modulation by cyclic GMP of the odor sensitivity of vertebrate olfactory receptor cells. Proc. Roy. Soc. Lond. B 263: 803–811.

Leinders-Zufall T., Rosenboom H., Barnstable C.J., Shepherd G.M. and Zufall F., F. (1995). A calcium-permeable cGMP-activated cation conductance in hippocampal neurons. NeuroReport 6: 1761–1765.

Leinders-Zufall T., Rand M.N., Shepherd G.M., Greer C.A. and Zufall F. (1997). Calcium entry through cyclic nucleotide-gated cannels in individual cilia of olfactory receptor cells: spatiotemporal dynamics. J. Neurosci. 17: 4136–4148.

Liu, N., Xu F., Miller P.L. and Shepherd G.M. (2007). OdorMapComparer: an application for quantitative analyses and comparisons of fMRI brain odor maps. Neuroinformatics. 5: 105–114.

Liu N., Xu F.Q., Marenco L., Miller P. and Shepherd G.M. (2004). Informatics approaches to functional MRI odor mapping of the rodent olfactory bulb: Odor-MapBuilder and OdorMapDB. Neuroinformatics 2: 3–18.

Ma M. and Shepherd G.M. (2000). Spatial relations of odor responses monitored by Ca²⁺ imaging in an intact mouse olfactory epithelial preparation. Proc. Natl. Acad. Sci. USA 97: 12869–12874.

Ma M., Chen W.R. and Shepherd G.M. (1999). Electrophysiological characterization of odor responses of rat and mouse olfctory receptor neurons in isolated epithelial patches. J. Neurosci. Methods 92: 31–40.

Ma M., Grosmaitre X., Iwema C.L., Baker H., Greer C.A. and Shepherd G.M. (2003). Olfactory signal transduction in the mouse septal organ. J. Neurosci. 23: 317–324.

Man, O., Willhite D.C., Crasto C.J., Shepherd G.M. and Gilad Y. (2007). A framework for exploring functional variability in olfactory receptor genes. PLoS ONE Aug 1;2:e682. PMID: 17668060.

Masukawa L.M., Hansen A.J. and Shepherd G.M. (1991). Distribution of single-channel conductances in cultured rat hippocampal neurons. Cell. Molec. Neurobiol. 11: 231–243.

Masukawa L.M., Hedlund B. and Shepherd G.M. (1985). Changes in the electrical properties of olfactory epithelial cells in the tiger salamander after olfactory nerve transection. J. Neurosci. 5: 136–141.

Masukawa L.M., Hedlund B. and Shepherd G.M. (1985). Electrophysiological properties of identified cells in the in vitro olfactory epithelium of the tiger salamander. J. Neurosci. 5: 128–135.

Masukawa L.M., Kauer J.S. and Shepherd G.M. (1983). Intracellular recordings from two cell types in an in vitro preparation of the salamander olfactory epithelium. Neurosci. Lett. 35: 59–64.

Migliore M. and Shepherd G.M. (2007). Dendritic action potentials connect distributed dendrodendritic circuits. J. Comput. Neurosci. Aug 3; [Epub ahead of print]

Migliore, M., Inzirillo, C. and Shepherd G.M. (2007). Learning mechanism for column formation in the olfactory bulb. Frontiers in Integrative Neurosci. 1: 12.

Migliore M., Hines M.L. and Shepherd G.M. (2005). The role of distal dendritic gap junctions in synchronization of mitral cell axonal output. J. Comput. Neurosci. 18: 151–161.

Mirsky J. S., Healy M.D., Nadkarni P.M., Skoufos E., Hines M., Miller P.L. and Shepherd G.M. (1998). Database tools for integrating and searching membrane property data correlated with neuronal morphology. J. Neurosci. Methods 82: 105–121.

Mori K. and Shepherd G.M. (1979). Synaptic excitation and long-lasting inhibition of mitral cells in the in vitro turtle olfactory bulb. Brain Res. 172: 155–159.

Mori K., Nowycky M.C. and Shepherd G.M. (1982). Impulse activity in presynaptic dendrites: analysis of mitral cells in the isolated turtle olfactory bulb. J. Neurosci. 2: 497–502.

Mori K., Nowycky M.C. and Shepherd G.M. (1984). Synaptic excitatory and inhibitory interactions at distal dendritic sites on mitral cells in the isolated turtle olfactory bulb. J. Neurosci. 4: 2291–2296.

Mori K., Nowycky M.C. and Shepherd G.M. (1981). Analysis of a long-duration inhibitory potential in mitral cells in the isolated turtle olfactory bulb. J. Physiol. 314: 311–320.

Mori K., Nowycky M.C. and Shepherd G.M. (1981). Analysis of synaptic potentials in mitral cells in the isolated turtle olfactory bulb. J. Physiol. 314: 295–309.

Mori K., Nowycky M.C. and Shepherd G.M. (1981). Electrophysiological analysis of mitral cells in the isolated turtle olfactory bulb. J. Physiol. 314: 281–294.

Nawroth J.C., Greeer C.A., Chen W.R., Laughlin S.B. and Shepherd G.M. (2007). An energy budget for the olfactory glomerulus. J. Neurosci. 27: 9790–9800.

Nowycky M.C., Mori K. and Shepherd G.M. (1981). Blockade of synaptic inhibition reveals long-lasting synaptic excitation in isolated turtle olfactory bulb. J. Neurophysiol. 46: 649–658.

Nowycky M.C., Mori K. and Shepherd G.M. (1981). GABAergic mechanisms of dendrodendritic synapses in isolated turtle olfactory bulb. J. Neurophysiol. 46: 639–648.

Nowycky M.C., Halasz N. and Shepherd G.M. (1983). Evoked field potential analysis of dopaminergic mechanisms in the isolated turtle olfactory bulb. Neurosci. 8: 717–722.

Ottoson D. and Shepherd G.M. (1965). Receptor potentials and impulse generation in the isolated spindle during controlled extension. Cold Spr. Harb. Symp. Quant. Biol. 30: 105–114.

Ottoson D. and Shepherd G.M. (1968). Changes of length within the frog muscle spindle during stretch as shown by stroboscopic photomicroscopy. Nature 220: 912–914.

Ottoson D. and Shepherd G.M. (1969). Relation of afferent nerve excitability to impulse generation in the frog spindle. Acta Physiol. Scand. 75: 49–63.

Ottoson D. and Shepherd G.M. (1970). Length changes within isolated frog muscle spindle during and after stretching. J. Physiol. 207: 747–759.

Ottoson D. and Shepherd G.M. (1970). Steps in impulse generation in the isolated muscle spindle. Act. Physiol. Scand. 79: 423–430.

Ottoson D. and Shepherd G.M. (1970). Synchronization of activity in afferent branches within the frog’s muscle spindle. Acta Physiol. Scand. 80:492–50l.

Ottoson D. and Shepherd G.M. (1971). Transducer characteristics of the muscle spindle as revealed by its receptor potential. Acta Physiol. Scand. 82:545–554.

Ottoson D., McReynolds J.S. and Shepherd G.M. (1969). Sensitivity of isolated frog muscle spindle during and after stretching. J. Neurophysiol. 32: 24–34.

Pedersen P.E., Stewart W.B., Greer C.A. and Shepherd G.M. (1983). Evidence for olfactory function in utero. Science 221: 478–480.

Pederson P.E., Jastreboff P.J., Stewart W.B. and Shepherd G.M. (1986). Mapping of an olfactory receptor population that projects to a specific region in the rat olfactory bulb. J. Comp. Neurol. 250: 93–108.

Peterson B.E., Healy M.D., Nadkarni P.M., Miller P.L. and Shepherd G.M. (1996). ModelDB: An environment for running and storing computational models and their results applied to neuroscience. J. Am. Med. Informatics Assoc. 3: 389–398.

Phillips C.C., Powell T.S. and Shepherd G.M. (1963). Response of mitral cells to stimulation of the lateral olfactory tract in the rabbit. J. Physiol. 168: 65–88.

Pongracz F., Poolos N.P., Kocsis J.D. and Shepherd G.M. (1992). A model of NMDA receptor-mediated activity in dendrites of hippocampal CA1 pyramidal neurons. J. Neurophysiol. 68: 2248–2259.

Pongracz F., Firestein S. and Shepherd G.M. (1991). Electrotonic structure of olfactory sensory neurons analysed by intracellular and whole cell patch techniques. J. Neurophysiol. 65: 747–758.

Pongracz F., McClintock T.S., Ache B. and Shepherd G.M. (1993). Signal transmission in lobster olfactory receptor cells: significance of electronic structure revealed by a compartmental model. Neurosci. 55: 325–338.

Rall W. and Shepherd G.M. (1968). Theoretical reconstruction of field potentials and dendro-dendritic synaptic interactions in olfactory bulb. J. Neurophysiol. 31: 884–915.

Rall W., Shepherd G.M., Reese T.S. and Brightman M.W. (1966). Dendro-dendritic synaptic pathway for inhibition in the olfactory bulb. Exp. Neurol. 14: 44–56.

Saghatelyan A., Roux P., Migliore M., Rochefort C., Desmaisons D., Charneau P., Shepherd G.M. and Lledo P-M. (2005). Activity-dependent adjustments of the inhibitory network in the olfactory bulb following early postnatal deprivation. Neuron 46: 103–116.

Sharp F.R., Kauer J.S. and Shepherd G.M. (1975). Local sites of activity-related glucose metabolism in rat olfactory bulb during odor stimulation. Brain Res. 98: 596–600.

Sharp F.R., J.S. and Kauer Shepherd G.M. (1977). Laminar analysis of 2-deoxyglucose uptake in olfactory bulb and olfactory cortex of rabbit and rat. J. Neurophysiol. 40: 800–813.

Shen G., Chen W.R., Midtgaard J., Shepherd G.M. and Hines M.L. (1999). Computational analysis of action potential initiation in mitral cell soma and dendrites based on dual patch recordings. J. Neurophysiol. 82: 3006–3020.

Shepherd G.M. (1963). Neuronal systems controlling mitral cell excitability. J. Physiol. 168: 101–117.

Shepherd G.M. (1963). Responses of mitral cells to olfactory nerve volleys in the rabbit. J. Physiol. 168: 89–100.

Shepherd G.M. (1966). The orientation of mitral cell dendrites. Exp. Neurol. 14: 390–395.

Shepherd G.M. (1971). Physiological evidence for dendrodendritic synaptic interaction in the rabbit’s olfactory glomerulus. Brain Res. 32: 212–217.

Shepherd G.M. and Ottoson D. (1965). Response of the isolated muscle spindle to different rates of stretching. Cold Spr. Harb. Symp. Quant. Biol. 30: 95–103.

Shepherd G.M. and Haberly L.B. (1970). Partial activation of olfactory bulb: analysis of field potentials and topographical relation between bulb and lateral olfactory tract. J. Neurophysiol. 33: 643–653.

Shepherd G.M. and Brayton R.K. (1979). Computer simulation of a dendrodendritic synaptic circuit for self-and lateral inhibition in the olfactory bulb. Brain Res. 175: 377–382.

Shepherd G.M. and Brayton R.K. (1987). Logic operations are properties of computer simulated interactions between excitable dendritic spines. Neurosci. 21: 151–166.

Shepherd G.M., Brayton R.K., Miller J.F., Segev I., Rinzel J. and Rall W. (1985). Signal enhancement in distal cortical dendrites by means of inter-actions between active dendritic spines. Proc. Nat. Acad. Sci. 82: 2192–2195.

Shepherd G.M., Woolf T.B. and Carnevale N.T. (1989). Comparisons between active properties of distal dendritic branches and spines: implications for neuronal computations. J. Cogn. Neurosci. 1: 273–286.

Singer M.S. and Shepherd G.M. (1994). Molecular modeling of ligand-receptor interactions in the OR5 olfactory receptor. NeuroReport 5: 1297–1300.

Singer M.S. and Shepherd G.M. (1996). Positive selection moments identify functionally important residues in mammalian olfactory receptors. Receptors & Channels 4: 141–147.

Singer M.S., Shepherd G.M. and Greer C.A. (1995). Olfactory receptors guide axons. Nature 377: 19–20.

Singer M.S., Oliveira L., Vriend G. and Shepherd G.M. (1995). Correlated mutation analysis identifies critical ligand-binding residues in olfactory receptor molecules. Receptors & Channels. 3: 89–95.

Singer M.S., Hughes T.E., Shepherd G.M. and Greer C.A. (1998). Identification of olfactory receptor mRNA sequences from the rat olfactory bulb glomerular layer. NeuroReport 9: 3745–3748.

Skoufos E., Marenco L., Nadkarni P.M., Miller P.L. and Shepherd G.M. (2000). Olfactory Receptor Database: a sensory chemoreceptor resource. Nucleic Acids Res. 28: 341–343.

Stewart W.B., Kauer J.S. and Shepherd G.M. (1979). Functional organization of the rat olfactory bulb analyzed by the 2-deoxyglucose method. J. Comp. Neurol. 185: 715–734.

Strowbridge B.W., Bean A.J., Spencer D.D., Roth R.H., Shepherd G.M. and Robbins R.J. (1992). Low levels of somatostatin-like immunoreactivity in neocortex resected from presumed seizure foci in epileptic patients. Brain Res. 587: 164–168.

Strowbridge B.W., Masukawa L.M., Spencer D.D. and Shepherd G.M. (1992). Hyper-excitability associated with localizable lesions in epileptic patients. Brain Res. 587: 158–163.

Teicher M.H., Stewart W.B., Kauer J.S. and Shepherd G.M. (1980). Suckling pheromone stimulation of a modified glomerular region in the developing rat olfactory bulb revealed by the 2-deoxyglucose method. Brain Res. 194: 530–535.

Trombley P. Q. and Shepherd G.M. (1994). Glycine exerts potent inhibitory actions on mammalian olfactory bulb neurons. J. Neurophysiol. 71: 761–767.

Trombley P.Q. and Shepherd G.M. (1992). Noradrenergic inhibition of synaptic transmission between mitral and granule cells in mammalian olfactory bulb cultures. J. Neurosci. 12: 3985–3991.

Waldow U., Nowycky M.C. and Shepherd G.M. (1981). Evoked potential and single unit responses to olfactory nerve volleys in the isolated turtle olfactory bulb. Brain Res.: 267–283.

Willhite, D.C., Nguyen K.T., Masurkar A.V., Greer C.A., Shepherd G.M. and Chen W.R. (2006). Viral tracing identified distributed columnar organization in the olfactory bulb. Proc. Natl. Acad. Sci. USA 103: 12592–12597.

Williamson A., Spencer D.D. and Shepherd G.M. (1993). Comparison between the membrane and synaptic properties of human and rodent dentate granule cells. Brain Res. 662: 194–202.

Woolf T.B., Shepherd G.M. and Greer C.A. (1991). Local information processing in dendritic trees: subsets of spines in granule cells of the mammalian olfactory bulb. J. Neurosci. 11: 1837–1854.

Woolf T.B., Shepherd G.M. and Greer C.A. (1991). Serial reconstructions of granule cell spines in the mammalian olfactory bulb. Synapse 7: 181–192.

Xu F., Shafer M., Kida I., Rothman R.L., Hyder F., Restrepo D. and Shepherd G.M. (2005). Comparison of responses in the mouse olfactory bulbs to odors and pheromones. J. Comp. Neurol. 489: 491–500.

Xu F.Q, Liu N, Kida I., Rothman D.L., Hyder F. and Shepherd G.M. (2003). Odor maps of aldehydes and esters revealed by fMRI in the glomerular layer of the mouse olfactory bulb. Proc. Nat. Acad. Sci. USA 100: 11029–11034.

Yang X., Renken R., Hyder F., Siddeek M., Greer C.A., Shepherd G.M. and Shulman R.G. (1998). Dynamic mapping at the laminar level of odor-elicited responses in rat olfactory bulb by functional MRI. Proc. Natl. Acad. Sci. USA 95: 7715–7720.

Zhang X., Rogers M., Tian H., Zhang X., Zou D-J., Liu J., Ma M., Shepherd G.M. and Firestein S. (2004). High-throughput microarray detection of olfactory receptor gene expression in the mouse. Proc. Natl. Acad. Sci. USA 101: 14168–14173.

Zhou, Z., Xiong W., Masurkar A.V., Chen an W.R. and d Shepherd G.M. (2006). Dendritic calcium plateau potentials modulate input-output properties of juxtaglomerular cells in the rat olfactory bulb. J. Neurophysiol. 96: 2354–2363.

Zhou, Z., Xiong W., Zeng S., Xia A., Shepherd G.M., Greer C.A. and Chen W.R. (2006). Dendritic excitability and calcium signalling in the mitral cell distal glomerular tuft. Eur. J. Neurosci. 24: 1623–1632.

Zufall F., Shepherd G.M. and Firestein S. (1991). Inhibition of the olfactory cyclic nucleotide gated ion channel by intracellular calcium. Proc. Roy. Soc. Lond. B. 246: 225–230.

Zufall F., Firestein S. and Shepherd G.M. (1991). Analysis of single cyclic nucleotide gated channels in olfactory receptor cells. J. Neurosci. 11: 3573–3580.

Reviews and Chapters

Albus, J.S., Bekey G.A., Holland J.H., Kanwisher N.G., Krichmar J.L., Mishkin M., Modhja D.S., Raichle M.E., Shepherd G.M. and Tononi G. (2007). A proposal for a Decade of the Mind initiative. Science 317: 1321.

Breer H. and Shepherd G.M. (1993). Implications of the NO/cGMP system for olfaction. Trends Neurosci. 16: 5–9.

Bug, W.J,, Ascoli G.A., Grethe J.S., Gupta A., Fennema-Notestin C., e A.R., Laird, S.D., Larson, D., Rubin G.M., Shepherd J.A. and Turner Martone M.E. (2008). The NIFSTD and BIRNLex vocabularies: building comprehensive ontologies for neuroscience. Neuroinformatics 6: 175–194.

BXu F.Q., Greer C.A. and Shepherd G.M. (2000). Odor maps in the olfactory bulb. J. Comp. Neurol. 422: 489–495.

Chen W.R. and Shepherd G.M. (2002). Putting odor maps in sync. Nature Neurosci. 5: 505–506.

Chen, W.R. and Shepherd G.M. (2006). The olfactory glomerulus: a cortical module with specific functions. J. Neurocytol. 34: 353–360.

Cheung, K.H., Lim E., Samwald M., Chen H., Marenco L., Holford M.E., Morse T.M., Mutalik P., Shepherd G.M. and Miller P.L. (2009). Approaches to neuroscience data integration. Brief Bioinform. 10: 345–353.

Crasto C., Singer M.S. and Shepherd G.M. (2001). The olfactory receptor family album. Genome Biology (online)

Crasto, C.J. and Shepherd G.M. (2007). Managing knowledge in neuroscience. Methods Mol. Biol. 401: 3–21.

Crasto, C.J., Marenco L.N., Liu N., Morse T.M., Cheung K.H., Lai P.C., Bahl G., Masiar P., Lam H.Y., Lim E., Chen H., Nadkarni P., Migliore M., Miller P.L. and Shepherd G.M. (2007). SenseLab: new developments in disseminating neuroscience information. Brief Bioinform. 8(3): 150–62.

Davison, A.P., Morse T.M., Migliore M., Shepherd G.M. and Hines M.L. (2004). Semi-automated population of an online database of neuronal models (ModelDB) with citation information, using PubMed for validation. Neuroinformatics 2:327–332.

Gardner, D. and Shepherd G.M. (2004). A gateway to the future of neuroinformatics. Neuroinformatics. 2: 271–274.

Gardner, D., Toga A.W., Ascoli G.A., Beatty J.T., Brinkley J.F., Dale A.M., Fox P.T., Gardner E.P., George J.S., Goddard N., Harris K.M., Herskovits E.H., Hines M.L., Jacobs G.A., Jacobs R.E., Jones E.G., Kennedy D.N., Kimberg D.Y., Mazziotta J.C., Miller P.L., Mori S., Mountain D.C., Reiss A.L., Rosen G.D., Rottenberg D.A., Shepherd G.M., Smalheiser N.R., Smith K.P., Strachan T., Van D.C., Essen R.W. and Williams Wong S.T. (2003). Towards effective and rewarding data sharing. Neuroinformatics 1: 289–295.

Gardner, D., Akil H., Ascoli G.A., Bowden D.M., Bug W., Donohue D.E., Goldberg D.H., Grafstein B., Grethe J.S., Gupta A., Halavi M., Kennedy D.N., Marenco L., Martone M.E., Miller P.L., Müller H.M., Robert A., Shepherd G.M., Sternberg P.W., Van D.C. and Essen Williams R.W. (2008). The neuroscience information framework: a data and knowledge environment for neuroscience. Neuroinformatics 6: 149–160.

Gazzaniga, M.S., Van Horn J.D., Bloom F., Shepherd G.M., Raichle M. and Jones E. (2006). Continuing progress in neuroinformatics. Science. 311: 176.

Halasz N. and Shepherd G.M. (1983). Neurochemistry of the vertebrate olfactory bulb. Neurosci. 10: 579–619.

Halasz N., Nowycky M.C., Shepherd G.M. and Hokfelt T. (1985). Catecholaminergic contributions to the neuronal machinery of the olfactory bulb: autoradiographic, immunohistochemical and evoked field potential studies. Chem. Senses 10: 203–218.

Hildebrand J.G. and Shepherd G.M. (1997). Molecular mechanisms of olfactory discrimination: converging evidence for common principles across phyla. Annu. Rev. Neurosci. 20: 595–631.

Hines M.L., Morse T., Migliore M., Carnevale N.T. and Shepherd G.M. (2004). ModelDB: a database to support computational neuroscience. J. Comput. Neurosci. 17: 7–11.

Jensen R.V. and Shepherd G.M.. (1992). NMDA-activated conductances provide short-term memory for dendritic spine logic computations. CNS*92 Proc. Conf. Comput. Neural Systems

Kauer J. S., White J. and Shepherd G.M. (1995). Olfactory bulb. In The Handbook of Brain Theory and Neural Networks (ed. Arbib M. A.). Cambridge, MA: MIT Press, pp. 665–669.

Lancet D., Greer C.A., Kauer J.S. and Shepherd G.M. (1982). Autoradiographic mapping of neuronal activity in the olfactory system of awake behaving vertebrates. In Chemoreception and the Determination of Behavior (eds. J.E. and Steiner Ganchrow J.R.). London: Information Retrieval pp. 47–56.

Ma M. and Shepherd G.M. (2002). Recordings from vertebrate olfactory receptor neurons: from isolated cells to intact epithelial preparations. In Methods in Chemosensory Research. (ed. S. A. Simon and M.A.L. Nicolelis) New York: CRC Press, pp. 65–78.

MacLeish P., Kinnamon S., Shepherd G.M. and Saccos-Sach J. i (1999). Sensory transduction. In Fundamental Neuroscience (ed. Zigmond M.). New York: Academic Press, pp. 671–717

Marenco L., Crasto C.J., Liu N., Migliore M., Liu J., Morse T.M., Hines M.L., Nadkarni P.M., Miller P.L. and Shepherd G.M. (2005). SenseLab: a decade of experience with multilevel, multidisciplinary neuroscience databases. In Databasing the Brain. From Data to Knowledge (Neuroinformatics) (ed. S.H. Koslow and S. Subramaniam). New York: Wiley-Liss, pp. 343–348.

Marenco, L., Ascoli G.A., Martone M.E., Shepherd G.M. and Miller P.L. (2008). The NIF LinkOut broker: a web resource to facilitate federated data integration using NCBI identifiers. Neuroinformatics 6: 219–227.

Marenco, L., Li Y., Martone M.E., Sternberg P.W., Shepherd G.M. and Miller P.L. (2008). Issues in the design of a pilot concept-based query interface for the neuroinformatics information framework. Neuroinformatics 6: 229–239.

Matus A. and Shepherd G.M. (2000). The millennium of the dendrite. Neuron 27: 431–434.

Migliore M. and Shepherd G.M. (2002). Emerging rules for the distributions of active dendritic conductances. Nature Neurosci. Revs. 3: 362–370.

Migliore, M. and Shepherd G.M. (2005). Opinion: an integrated approach to classifying neuronal phenotypes. Nat. Rev. Neurosci. 10: 810–818.

Migliore, M., Morse T.M., Davison A.P., Marenco L., Shepherd G.M. and Hines M.L. (2003). ModelDB: making models publicly accessible to support computational neuroscience. Neuroinformatics 1: 135–139.

Miller P.L., Marenco L., Shepherd G.M. and Nadkarni P.M. (2005). Entity-attribute-value database approaches for heterogeneous, evolving neuroscience data. In Databasing the Brain. From Data to Knowledge (Neuroinformatics) (ed. S.H. Koslow and S. Subramaniam). New York: Wiley-Liss, pp. 83–98.

Mori K. and Shepherd G.M. (1994). Emerging principles of molecular signal processing by mitral/tufted cells in the olfactory bulb. Seminars in Cell Biology 5: 65–74.

Ottoson D. and Shepherd G.M. (1967). Experiments and concepts in olfactory physiology. Progr. Brain Res. 23: 83–138.

Ottoson D. and Shepherd G.M. (1971). Transducer properties and integrative mechanisms in the frog’s muscle spindle. In Principles of Receptor Physiology. Handbook of Sensory Physiology, Vol. I. (ed. Lowenstein W.R.). New York: Springer, pp. 442–449.

Pedersen P.E., Greer C.A. and Shepherd G.M. (1985). Early development of olfactory function. In Handbook of Behavioral Neurobiology, Vol. 1. Developmental Processes in Psychobiology and Neurobiology (ed. Blass E.M.). New York: Plenum Press, pp. 163–203.

Pederson P.E., Shepherd G.M. and Greer C.A. (1987). Cytochrome oxidase staining in the olfactory epithelium and bulb of normal and odor-deprived neonatal rats. In Olfaction and Taste IX (eds. Roper S. and Atema J.) Ann. N.Y. Acad. Sci. 510: 544–546.

Reese T.S. and Shepherd G.M. (1972). Dendro-dendritic synapses in the central nervous system. In The Structure and Function of Synapses (eds. Pappas G.D. and Purpura D.P.). New York: Raven, pp. 121–136.

Shepherd G.M (1985). Are there labelled lines in the olfactory pathway? In Taste,Olfaction and the Central Nervous System (ed. by Pfaff D.W.). New York: Rockefeller, pp. 307–321.

Shepherd G.M (1985). The olfactory system: the uses of neural space for a nonspatial modality. In Contemporary Sensory Neurobiology (eds. M. and Correia Perachio A.A.). New York: Alan R. Liss, pp. 99–114.

Shepherd G.M. (1970). The olfactory bulb as a simple cortical system: experimental analysis and functional implications. In The Neurosciences: Second Study Program. (ed. Schmitt F.O.). New York: Rockefeller, pp. 539–552.

Shepherd G.M. (1972). Synaptic organization of the mammalian olfactory bulb. Physiol. Rev. 52: 864–917.

Shepherd G.M. (1972). The neuron doctrine: a revision of functional concepts. Yale J. Biol. Med. 45: 584–599.

Shepherd G.M. (1975). Axons, dendrites and synapses. In Cole Symposium on Membranes, Ions and Impulses. (ed. Moore J.). Fed. Proc. 34: 1395–1397.

Shepherd G.M. (1975). Models of local circuit neuron function in the olfactory bulb. In Local Circuit Neurons (ed. Rakic P.). NRP Bulletin, pp. 344–352.

Shepherd G.M. (1976). Olfactory stimulation. In Neuroanatomical Functional Mapping as Determined by the Radioactive 2-Deoxyglucose Method (eds. Plum F. and Sampson F.). NRP Bulletin, pp. 478–484.

Shepherd G.M. (1977). Central processing of olfactory signals. In Chemical Signals in Vertebrates (eds. Muller-Schwarze D. and Mozell M.M.). New York: Plenum. pp. 489–498.

Shepherd G.M. (1977). The olfactory bulb: a simple system in the mammalian brain. In Handbook of Physiology, Sect. l, The Nervous System; Part l, Cellular Biology of Neurons (ed. Kandel E.R.). Bethesda: American Physiological Society, pp. 945–968.

Shepherd G.M. (1978). Introduction. Symposium on Neurochemistry of Olfactory Circuits. In Society for Neuroscience Symposium, Vol. IV. (ed. Ferrendelli J.A.). Bethesda: Society for Neuroscience, pp. 129–130.

Shepherd G.M. (1978). Localization of activity in the olfactory bulb by the deoxyglucose method. In Society for Neuroscience Symposium, Vol. IV. (ed. Ferrendelli J.A.). Bethesda: Society for Neuroscience, pp. 219–225.

Shepherd G.M. (1978). Microcircuits in the nervous system. Scientific American. Feb:

Shepherd G.M. (1979). Introductions to chapters on: Introduction to Local Circuits; Spikeless and Electronic Information Processing; Structural Aspects of Local Circuits. In The Neurosciences: Fourth Study Program (eds. Schmitt F.O. and Worden F.G.). Cambridge: MIT, pp. 107, 315, 371.

Shepherd G.M. (1979). The functional analysis of local circuits in the olfactory bulb. In The Neurosciences: Fourth Study Program (eds. Schmitt F.O. and Worden F.G.. Cambridge: MIT, pp. 129–144.

Shepherd G.M. (1985). Olfactory transduction: Welcome whiff of biochemistry. Nature 316: 214–215.

Shepherd G.M. (1986). Apical dendritic spines of cortical pyramidal cells: remarks on their possible roles in higher brain functions, including memory. In Synapses, Circuits, and the Beginnings of Memory (ed. Lynch G.) Cambridge, MA: MIT Press, pp. 85–98

Shepherd G.M. (1986). Neurobiology: microcircuits to see by. Nature 319: 452–453.

Shepherd G.M. (1987) The olfactory bulb. In Encyclopedia of Neuroscience (ed. Adelman G.). Boston: Birkhauser, pp. 879–881.

Shepherd G.M. (1987). A molecular vocabulary for olfaction. In Olfaction and Taste X (eds. Roper S. and Atema J.) Ann. N.Y. Acad. Sci. 510: 98–103.

Shepherd G.M. (1987). Dendrites, dendrodendritic interactions. In Encyclopedia of Neuroscience (ed. Adelman G.). Boston: Birkhauser, pp. 317–318.

Shepherd G.M. (1988). A basic circuit for cortical organization. In Perspectives on Memory Research (ed. Gazzaniga M.C.). Cambridge, MA: MIT Press, pp. 93–134.

Shepherd G.M. (1989). Studies of development and plasticity in the olfactory sensory neuron. J. Physiol. Paris 83: 240–245.

Shepherd G.M. (1990). The significance of real neuron architectures for neural network simulations. In Computational Neuroscience (ed. Schwartz E.). Cambridge, MA: MIT Press, pp. 82–96.

Shepherd G.M. (1991). Computational structure of the olfactory system. In Olfaction: A Model for Computational Neuroscience (ed. Eichenbaum H. and Davis J.). Cambridge, Mass.: MIT Press, pp. 3–42. revised from Shepherd, G.M. (1990) Contribution toward a theory of olfaction. In R.H. Wright Lectures on Olfactory Research (ed. K. Colbow). Simon Fraser University, pp. 61–109.]

Shepherd G.M. (1991). Sensory transduction: joining the mainstream of membrane signalling. Cell 67: 845–851.

Shepherd G.M. (1992). Canonical neurons and their computational organization. In Single Neuron Computation (ed. McKenna T., Davis J. and Zornetzer S.F.). Cambridge, MA: MIT Press, pp. 27–59.

Shepherd G.M. (1992). Modules for molecules. Nature 358: 457–458.

Shepherd G.M. (1993). Current issues in the molecular biology of olfaction. Chem. Senses 18: 191–198.

Shepherd G.M. (1993). Specificity and redundancy in the organization of the olfactory system. Microscopy Res. Tech. 24: 106–112.

Shepherd G.M. (1994). Discrimination of molecular signals by the olfactory system. Neuron 13: 771–790.

Shepherd G.M. (1995). Commentaries. In The Theoretical Foundation of Dendritic Function. Selected Papers of Wilfrid Rall. (ed. Segev I., Rinzel J. and Shepherd G.M.). Cambridge, MA: MIT Press, pp. xx–xx.

Shepherd G.M. (1995). Olfactory cortex. In The Encyclopedia of Learning and Memory (ed. Thompson R. F.). New York: Macmillan.

Shepherd G.M. (1995). Synaptic transmission. In Encyclopedia of Science and Technology. New York: McGraw-Hill.

Shepherd G.M. (1995). Toward a molecular basis of perception. In The Cognitive Neurosciences: A Handbook for the Field (ed. Gazzaniga M.S.). Cambridge, MA: MIT Press, pp. 105–122.

Shepherd G.M. (1996). Synaptic circuits and physiological operations in the central nervous system. In Human Physiology: From Cellular Mechanisms to Integration (eds. Greger R., Koepchen H.P., Mommaerts W. and Windhorst U.). New York: Springer, pp. 497–508.

Shepherd G.M. (1996). The dendritic spine: a multifunctional integrative unit. J. Neurophysiol. 75: 2197–2210.

Shepherd G.M. (1998). Dendrites, dendrodendritic synapses. In Encyclopedia of Neuroscience. 2nd ed. (ed. G. Adelman, & Smith B.H.) New York: Elsevier (CD ROM)

Shepherd G.M. (1998). The neuron doctrine. In Encyclopedia of Neuroscience. 2nd ed. (ed. G. Adelman, & Smith B.H.) New York: Elsevier (CD ROM)

Shepherd G.M. (1999). Foreword to Camillo Golgi, by P. Mazzarello. New York: Oxford University Press, pp. .

Shepherd G.M. (1999). Information processing in dendrites. In Fundamental Neuroscience (ed. Zigmond M.). New York: Academic Press, pp. 363–388

Shepherd G.M. (1999). Perspective on the synapse. In The Drunken Synapse (ed. Y. Liu and W.A. Hunt). New York: Plenum, pp.

Shepherd G.M. (1999). The legacy of Camillo Golgi for modern concepts of brain organization. J. Hist. Neuroscience 8: 209–214.

Shepherd G.M. (1999). The neuron. In MIT Encyclopedia of the Cognitive Sciences.

Shepherd G.M. (2000). Complementarity beyond physics (1928–1962). Niels Bohr Collected Works. (ed. D. Favhrholdt). Endeavour. 24: 180–181.

Shepherd G.M. (2003). Sharing the mighty mouse. Neuroinformatics 1: 411–413.

Shepherd G.M. (2003). The single capillary and the active brain. Proc. Natl. Acad. Sci. USA 100: 12535–12536.

Shepherd G.M. (2004). Implications of recent research on olfaction for the neural basis of flavor in humans: challenges and opportunities. In Handbook of Flavor Characterization. Sensory Analysis, Chemistry, and Physiology (ed. K.D. Deibler and J. Delwiche). New York: Marcel Dekker, pp. 93–104.

Shepherd G.M. (2004). The human sense of smell: are we better than we think? PLOS Biology 2:E146. Epub May 2004, 11.

Shepherd G.M. (2005). Outline of a theory of olfactory processing and its relevance to humans. Chem. Senses 30: Suppl 1:i3–i5

Shepherd G.M. (2005). Perception without a thalamus: how does olfaction do it? Neuron 46: 166–168.

Shepherd, G.M. (2006). Smell images and the flavour system in the human brain. Nature (Insight) 444: 316–321.

Shepherd G.M. (2007). Perspectives on olfactory processing, conscious perception, and orbitofrontal cortex. In Linking Affect to Action. Orbitofrontal Cortex (ed. J. Gottfried, G. Schoenbaum, E. Murray and S. Ramus). New York: New York Academy of Science, 1121: 87–101.

Shepherd G.M. (2008). Neuron Doctrine. New Encyclopedia of Neuroscience.

Shepherd G.M. (2009). Olfaction. In Oxford Companion to Consciousness. New York: Oxford University Press.

Shepherd G.M. (2009). Overview of the chemical senses. New Encyclopedia of Neuroscience.

Shepherd G.M. (2009). Passive membrane properties of axons and dendrites. Fundamental Neuroscience. Third Edition. (eds. Bloom F. et al). New York: Academic Press.

Shepherd G.M. (2009). Symposium overview and historical perspective: dendroden-dritic synapses: past, present, and future. Ann. NY Acad. Sci. 1170: 215–223.

Shepherd G.M. (2009) Information processing in complex dendrites. In Fundamental Neuroscience (Third Edition). (ed. Bloom F. et al ). New York: Academic Press.

Shepherd G.M. (1981). Synaptic and impulse loci in olfactory bulb dendritic circuits. In Neurones Without Impulses: Their Significance for Vertebrate and Invertebrate Nervous Systems. (eds. Roberts A. and Bush B.M.H.). Society of Experimental Biology Seminar Series 6. London: Cambridge University pp. 255–267.

Shepherd G.M. (1981). The nerve impulse and the nature of nervous function. In Neurones Without Impulses: Their Significance for Vertebrate and Invertebrate Nervous Systems. (eds. Roberts A. and Bush B.M.H.). Society of Experimental Biology Seminar Series 6. London: Cambridge University Press, pp. 1–27.

Shepherd G.M. (1981). The olfactory glomerulus: its significance for sensory processing. In Brain Mechanisms of Sensation (eds. Katzuki Y. and Norgren R.). New York: Wiley, pp. xx–xx.

Shepherd G.M. and Koch C. (1990). Dendritic electrotonus and synaptic integration. In The Synaptic Organization of the Brain (ed. Shepherd G.M.). New York: Oxford University Press, pp. 439–473.

Shepherd G.M. and Koch C. (1990). Introduction to synaptic circuits. In The Synaptic Organization of the Brain (ed. Shepherd G.M.). New York: Oxford University Press, pp. 3–31.

Shepherd G.M. and Greer C.A. (1988). The dendritic spine: adaptations of structure and function for different types of synaptic integration. In Intrinsic Determinants of Neuronal Form (ed. Lassek R.). pp. 245–262.

Shepherd G.M. and Greer C.A. (1990). Olfactory bulb. In The Synaptic Organization of the Brain (ed. Shepherd G.M.). New York: Oxford University Press, pp. 133–169.

Shepherd G.M. and Greer C.A. (1998). Olfactory bulb. In The Synaptic Organization of the Brain (ed. G.M. Shepherd). New York: Oxford University Press, pp. 159–204

Shepherd G.M. and Charpak S. (2008). The olfactory glomeruus: a model for neuro-glio-vascular biology. Neuron 58: 827–829.

Shepherd G.M. and Firestein S. (1991). Making scents of olfactory transduction. Current Biology 1: 204–206.

Shepherd G.M. and Firestein S. (1991). Toward a pharmacology of odor receptors and the processing of odor images. J. Steroid Biochem. Molec. Biol. 39: 583–592.

Shepherd G.M. and Erulkar S.D. (1997). Centennial of the synapse: from Sherrington to the molecular biology of the synapse and beyond. Trends Neurosci. 20: 385–392.

Shepherd G.M., Crasto C. and Singer M.S. (2003). Olfactory genes and flavour perception: implications for the evolution of human cuisines. In Flavour Research at the Dawn of the Twenty-First Century. Proceedings of the 10th Weurman Flavour Research Symposium (ed. J-L. Le Quere and P.X. Etievant) London: Lavoiser/Intercept, pp. 263–268.

Shepherd G.M., Mirsky J.S., Healy M.D., Singer M.S., Skoufos E., Hines M.S., Nadkarni P.M. and Miller P.L. (1998). The Human Brain Project: neuroinformatics tools for integrating, searching, and modeling multidisciplinary neuroscience data. Trends Neurosci. 21: 460–468.

Shepherd G.M., Nowycky M.C., Greer C.A. and Mori K. (1981). Multiple overlapping circuits within olfactory and basal forebrain systems. In Neural Communication and Control: Facts and Theories (ed. Szekely G.) New York: Pergamon Press, pp. xx–xx.

Shepherd G.M., Healy M.D., Singer M.S., Peterson B.E., Mirsky J.S., Wright L., Smith J.E. and Nadkarni P.M. and P.L. Miller (1997). SenseLab: a project in multidisciplinary, multilevel sensory integration. In Neuroinformatics: An Overview of the Human Brain Project (eds. E.H. Koslow and M.F. Huerta). New York: Lawrence Erlbaum, pp. 21–56.

Shepherd G.M., Singer M.S. and Greer C.A. (1996). Olfactory receptors: a large gene family with broad affinities and multiple functions. The Neuroscientist 2: 262–271.

Shepherd G.M., Pedersen P.E. and Greer C.A. (1987). Development of olfactory specificity in the albino rat: a model system. In Perinatal Development: A Psychobiological Perspective (eds. Krasnegor N.A., Blass E.M., Hofer B.A. and Smotherman W.P.) New York: Academic Press, pp. 129–144.

Shepherd G.M., Getchell T.V. and Mistretta C.M. (1986). Questions of taste and smell. Nature 324: 17–18.

Shepherd G.M., Getchell T.V. and Kauer J.S. (1975). Analysis of structure-function relations in the olfactory pathway. In The Nervous System, Vol. l. The Basic Neurosciences. (ed. Tower D.B.). New York: Raven Press, pp. 207–220.

Shepherd G.M., Chen W.R., Willhite D., Migliore M. and Greer C.A. (2007). The olfactory granule cell: from classical enigma to central role in olfactory processing. Brain Res. Rev. 03.005.

Shepherd, G.M.. (2006). Behaviour: smells, brains and hormones. Nature. 439: 149–151.

Shepherd-Barr K. and Shepherd G.M. (1998). Madeleines and neuromodernism: reassessing mechanisms of autobiographical memory in Proust. Auto/Biography Studies 13: 39–60.

Shepherd-Barr K. and Shepherd G.M. (2009). The Proust Effect. Encyclopedia of Neuroscience. New York: Elsevier.

Singer M.S. and Shepherd G.M. (1997). Toward a rational structure-function analysis of odor molecules: the olfactory receptor TM4 domain. In Flavours and Fragrances (ed. Swift K.A.D.) Cambridge: Roy. Soc. Chemistry, pp. 3–10

Singer M.S. and Shepherd G.M. (2002). Olfactory receptors. In Wiley Encyclopedia of Molecular Medicine. New York: John Wiley, pp. 2320–2323.

Smith D. and Shepherd G.M. (1999). Taste and olfaction. In Fundamental Neuroscience (ed. Zigmond M.). New York: Academic Press, pp. 719–759.

Stewart W.B. and Shepherd G.M. (1985). The chemical senses: taste and smell. In Scientific Basis of Clinical Neurology (eds. Swash M. and Kennard C.). London: Churchill Livingstone, pp. 214–224.

Trombley P.Q and Shepherd G.M. (1993). Synaptic transmission and modulation in the olfactory bulb. Curr. Opinion Neurobiol. 3: 540–547.

Trombley P.Q. and Shepherd G.M. (1998). The olfactory bulb. In Encyclopedia of Neuroscience. 2nd ed. (ed. G. Adelman and B.H. Smith) New York: Elsevier (CD ROM)

Wilson M. and Shepherd G.M. (1995). Olfactory cortex. In The Handbook of Brain Theory and Neural Networks (ed. Arbib M. A.). Cambridge, MA: MIT Press, pp. 669–673.

Xu F., Greer C. and Shepherd G.M. (2002). Application of fMRI in olfactory studies. In Methods in Chemosensory Research (ed. S.A. Simon and M.A.L. Nicolelis) New York: CRC Press, pp. 465–476.

Zufall F., Barnstable C. and Shepherd G.M. (1997). Cyclic nucleotide-gated channels as regulators of CNS development and plasticity. Curr. Opin. Neurobiol. 7: 404–412.

Zufall F., Firestein S.F. and Shepherd G.M. (1994). Cyclic nucleotide-gated ion channels and sensory transduction in olfactory receptor neurons. Ann. Rev. Biophysics Biomolecular Structure 23: 577–607.

Thesis and Books

Segev I., Rinzel J. and Shepherd G. M. (Eds.). (1995). The Theoretical Foundation of Dendritic Function. Selected Papers of Wilfrid Rall. Cambridge, MA: MIT Press.

Shepherd G.M. (1962). Transmission in the Olfactory Pathway. D. Phil. Thesis in Physiology: Oxford University.

Shepherd G.M. (1974). The Synaptic Organization of the Brain. New York: Oxford University Press.

Shepherd G.M. (1979). The Synaptic Organization of the Brain (Second Edition). New York: Oxford University Press.

Shepherd G.M. (1983). Neurobiology. New York: Oxford University Press. (Spanish edition, 1985; Russian edition, 1987).

Shepherd G.M. (1988). Neurobiology (Second Edition). New York: Oxford University Press. (Japanese edition, 1990; Chinese edition, 1992; German edition, 1994).

Shepherd G.M. (1991). Foundations of the Neuron Doctrine. New York: Oxford University Press.

Shepherd G.M. (1994). Neurobiology (Third Edition). New York: Oxford University Press.

Shepherd G.M. (2010). Creating Modern Neuroscience. The Revolutionary 1950s. New York: Oxford University Press.

Shepherd G.M. (Ed.) (1990). The Synaptic Organization of the Brain (Third Edition). New York: Oxford University Press.

Shepherd G.M. (Ed.) (1998). The Synaptic Organization of the Brain (Fourth Edition). New York: Oxford University Press.

Shepherd G.M. (Ed.) (2004). The Synaptic Organization of the Brain (Fifth Edition). New York: OxfordUniversityPress.

Shepherd G.M. and Grillner S. (Eds.) (2010). Handbook of Brain Microcircuits. New York: Oxford University Press.

Miscellaneous

Shepherd GM. (2002). Supporting databases for neuroscience research. J. Neurosci. Mar 1; 22(5): 1497.

Shepherd G.M. (1999–2002). Editorials as Editor-in-Chief of J. Neurosci.

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Robert H. Wurtz

BORN:

Saint Louis, Missouri

March 28, 1936

EDUCATION:

Oberlin College, A.B, Chemistry (1958)

University of Michigan, Ph.D., Physiological Psychology (1962)

APPOINTMENTS:

Research Fellow, Departments of Physiology and Neurology, Washington University School of Medicine (1962–1965)

Research Associate, Committee for Nuclear Information (1962–1963)

Research Fellow, National Institute of Neurological Diseases and Blindness, NIH (1965–1966)

Physiologist, National Institute of Mental Health, NIH (1966–1978)

Visiting Scientist, Physiological Laboratory, Cambridge University (1975–1976)

Founding Chief, Laboratory of Sensorimotor Research, National Eye Institute, NIH (1978–2002)

Chief, Section on Visual Motor Integration, Laboratory of Sensorimotor Research, NEI, NIH (2002–present)

NIH Distinguished Investigator (2008–present)

HONORS AND AWARDS (SELECTED):

W. Alden Spencer Award, Columbia University (1987)

National Academy of Sciences (1988)

American Academy of Arts and Sciences (1990)

President, Society for Neuroscience (1991)

Karl Spencer Lashley Award, American Philosophical Society (1995)

Friedenwald Award, Association for Research in Vision and Ophthalmology (1996)

Distinguished Scientific Contribution Award, American Psychological Association (1997)

Institute of Medicine of the National Academy of Sciences (1997)

Dan David Prize for the Future Time Dimension: “Brain Sciences” (2004)

Ralph W. Gerard Prize of the Society for Neuroscience (2006)

Honorary Doctor of Science, Oberlin College (2009)

Grass Lecture, Society for Neuroscience (2009)

Gruber Neuroscience Prize (2010)

Robert H. Wurtz developed methods for studying the visual system in awake behaving monkeys, a technique now widely used for the study of higher brain functions. He has pioneered the use of this technique to explore the neuronal basis of active vision, the integration of the visual, oculomotor, and cognitive functions underlying visual perception. He has done so in collaboration with a series of postdoctoral fellows, many of whom have gone on to become leaders in the field of systems neuroscience. His discoveries with these collaborators include establishing the functional organization of the primate superior colliculus, its role in generating saccadic eye movements, and its contribution to higher functions, including visual attention; the identification of a brain circuit for a corollary discharge of eye movements and the possible contribution of this corollary to stable visual perception; the circuit connecting the basal ganglia to the superior colliculus and the nature of its inhibitory action; the contribution of cortical visual motion processing to perception, pursuit eye movements, and the registration of large field optic flow. He was founding Chief of the Laboratory of Sensorimotor Research in the National Eye Institute of the National Institutes of Health.

Robert H. Wurtz

I try to write a scientific paper in a way that states a question, explains the methods to address it, gives the answer, and then discusses what it means. Like the biographical sketch above, it is a formal archival report.

But both in the limited experiment and in the larger life, these reports give none of the real course of events. All the twists and turns of real science and a scientist’s life are converted into a straight line from goal to achievement. In this autobiographical sketch I try to give the real why of experiments and of my life in doing the experiments.

My scientific life spans the rise of neuroscience as a scientific discipline with my own work dedicated to exploring systems within the brain. I hope my comments provide a little insight into the development of my nook of systems neuroscience. I also hope it might encourage younger scientists to realize that mistakes are not fatal, only failing to take the risks that can produce mistakes is fatal. Of course I am the main beneficiary of this autobiography because it provides a sobering summary of where so much time has gone so fast. I am grateful to Larry Squire for his very flattering invitation; I would never have done this otherwise.

The Beginning (1936–1954)

My father hated his job. I start my commentary with such a seemingly irrelevant statement because I think it shaped the course of my life in science. I was shaped somewhat by inherent abilities, but more by the circumstances in which I grew up. I now realize that none was more important than my family, teachers, and friends, and none of those rivals the influence of my father.

My father was born in Indianapolis, Indiana, in 1887 during a sojourn his father made for several years from St Louis. He was named Robert after his father, who was a tool and die maker designing the blades that slice the patterns into picture frame molding. My Grandmother Wurtz was so unhappy so far from her friends in St Louis that my grandparents moved back to St Louis where four brothers and a sister followed my father into a family in turmoil. My grandmother was simply unable to take care of the children, and so my father was raised by an aunt who looked after him until his early teens. She was a nurturing guardian, and her carpenter husband generated my father’s interest in carpentry. Those interests were passed on to me as a child, and then to my son who now is a carpenter. My Grandfather Wurtz descended into alcoholism, and the family became increasingly financially stressed. As the children reached an age when they could work, necessity required they do so. My father had just finished sixth grade when he went to work. He loved school but was forced to leave when he had learned reading, writing, and arithmetic. He became one of the most educated people I have met, but that was later, and entirely on his own.

He worked at a variety of jobs in St Louis, few of which I know, but he eventually worked in candy stores, and by the time I was born he was factory superintendent for the Mavrakos Candy Company, a St Louis confectionary landmark. This job rewarded his management ability. He planned the production schedules and supervised a substantial work force, the majority of whom were the women chocolate dippers, those who dipped the variety of centers into chocolate by hand. They liked him and gave him a wallet every Christmas which, since he used only a change purse, provided me a supply I have only recently exhausted. The founder-owner apparently recognized my father’s ability to keep things running efficiently, and for someone with little education, the job paid well. The 6 day per week regime, 1 week vacation, and continuing conflicts between owner and workers left him exhausted. He was also an avid socialist who emotionally sided with the poorly paid workers, not the management.

My mother hired him at Mavrakos. She was the bookkeeper for the company, did the initial job interviews, and was clearly one of the super-competent women who ran things as underlings because they were women. My mother was the daughter of first-generation immigrants from Yorkshire and Lancashire, England. My grandfather, Harry Popplewell, emigrated after his farmer and innkeeper father died of tetanus when his hand became caught in a mowing machine. Harry was the youngest son, would inherit nothing, had little future in England, and with his wife and young son, traveled to St Louis, Missouri, at the behest of a relative who lived there. My Grandmother Popplewell was terrified at the sight of her first black man, and both always recalled being startled at seeing their first lightening bugs. My grandfather did what he knew; he became a livestock trader, a rough and tumble expression of free enterprise in growing St Louis in the decade before the 1904 World’s Fair. As a child, I was riveted by his tales, but I suspect I missed the best ones when my grandmother, sensing the impending story, invited me to help her with the dishes. Alice, my mother, was born in 1901, was a late last child after her three brothers, and the favorite of my grandmother.

The initial relationship between my mother and father moved beyond work, and they were married by a justice of the peace, and honeymooned by driving to Springfield, Illinois, for a weekend. They had both been frugal, and they used their savings to invest in building a modest house in Webster Groves, a suburb of St Louis. My father deemed it to have the best public school system, and he was determined that I would have the education he did not. My mother thought education was desirable, but she did not bring the passion of my father to that goal. My mother wished she had become a certified public accountant; my father wished he were a concert violinist or a college professor. I absorbed the business bent of my mother and the intellectual bent of my father, but my father’s interests won out.

I was born in 1936, a late child for my father (in his 40s) and my mother (in her 30s), and an only child. My mother stopped work to care for me, which was the proper thing to do at the time, though there is no doubt that she would have preferred to continue working. I was frequently sick as a child with the usual round of childhood diseases, a seemingly continuous round of colds, and scarlet fever. My father continued working long hours, but we usually took trips to state parks on Sundays for picnics and hikes. The high point of the year was the summer vacation trip, which became longer after my father retired, and frequently included his favorite destination, Yellowstone National Park.

I liked school and did consistently well. I was inspired by my fifth and sixth grade teacher, Mary Moore, to read as much as possible, and she would suggest books, particularly on history, which became an enduring interest. I remember Francis Parkman’s The Oregon Trail as a riveting read. She also had me come in early several times a week to practice my abysmal handwriting, and my mother worked with me on spelling. Their considerable effort failed on both counts. I am convinced poor spelling at least is a built-in characteristic. A high school English teacher summed it up: “Young man, if your livelihood depends on spelling, you will starve,” and while I have been saved by the computer, the deficit persists. After a change in my e-mail system, I immediately got returns from friends: “Bob, turn on your spell check.”

While I excelled in school work through high school, a nagging disability dating from preschool years was a debilitating stutter. I was given speech therapy both in school and in private sessions with little benefit. Then in junior high school I gave a successful and well-rehearsed talk in the course of running for school president. The debate coach, Dorothy Weirich, suggested that I join the debate team. When I explained that I could not because of the stutter, she simply said that it was irrelevant, and that preparing for debates would help my speech. I agreed to do so with considerable anxiety, and over the high school years my stutter diminished as success in debates increased. Our team won the Missouri state debate championship in my senior year due in part to what I thought was my particularly effective final rebuttal. I had many devoted teachers, but the abilities I use every day result from Mary Moore in grade school and Dorothy Weirich in high school. My parents’ determination to provide me a good education shaped my life in ways they could never have imagined.

I adored my father, and the feelings were clearly mutual. His goal was to teach me everything he knew, and he never lost an opportunity to show me how to garden, take pictures, go camping, use carpentry tools, and adopt his attitude that anything can be repaired. He even guided me when I became obsessed with fishing and assuaged my anxiety over what to do if I catch a fish with an aphorism I have used throughout life: “First we will get the fish on the hook, and then we will worry about getting it off.” My father was greatly relieved when my fishing phase ended because he was a vegetarian who felt that there was no need for any animal to die for his lunch. But when I became interested in biology he strongly supported doing research on animals because there was good reason for an animal to die humanely to advance the knowledge from which we all benefit, including animals. He was always hopeful that I might become a scientist though of course regarded it as my decision and never proselytized. Among my aunts and uncles, I was regarded as a bright child, one who someday might even become a dentist.

My only failure in my father’s eyes was my limited success in playing the violin. His father had played the violin and taught him to play, and so my father began teaching me before kindergarten, and continued until I had private lessons. I played in the orchestras in grade school and junior and senior high school, but my talent was limited and my desire to practice was negligible. I think my father’s disappointment was ameliorated by my success in school and his own diligent practicing after he retired.

I was always shy, and so was not a participant in the social whirl of the suburban high school that was the topic of a TV network program “Sixteen in Webster Groves” filmed some years after I graduated. I was also a clumsy athlete, usually being placed in right field. In high school I accumulated a group of friends who were nerds in today’s vernacular. We were all interested in science, were sufficiently quick witted to maintain a lively patter. We had more unbridled discussions on world events than we ever had in the more staid classroom. We all went to college, all became scientists or engineers, and my interaction with them intensified my own interest in science. Our favorite science teacher was Evrard Leek, who taught a course in physics starting with classical mechanics. I can remember to this day the realization that physical phenomena like the force of a pulley system can be described by a simple equation. It was the first insight into what science was about. Essentially, the positive influence of my father as a child had been replaced by an equally positive and dominating one of a peer group.

Oberlin and Deciding What to Do When I Grew up (1954–1958)

I viewed the decision about what kind of college I should go to as a restatement of my father’s dictum: Find what you like to do and then spend your life doing it. I viewed college as the opportunity to find that out. So what I wanted was a liberal arts college, but I had little idea of how to even begin to make the choice. One of my high school group was applying to Swarthmore, and he said I should do so as well. I thought it was too far from home; I had never been away from my parents for more than a weekend. He then suggested Oberlin as being probably as good and only half the distance from St. Louis. So I applied, was accepted, and received a tuition scholarship. It had the advantage of providing a good education, and it had the reputation for actively supporting social causes. This latter point was a significant factor to me because my father’s socialism had given me the goal of leaving the world a better place than I had found it. In the fall of 1954, my parents drove me to Oberlin, and I was off to determine what I was going to be.

I began thinking I might major in chemistry, in part because of an inspirational second semester my freshman year taught by J. Arthur Campbell, who emphasized problem solving and not memory—the periodic table was always on the wall. This was my first inkling that I really did not have a great memory, and that I in part compensated by figuring things out, even those things most other students could just memorize. My sophomore year allowed me to look around and exposed me to two exciting areas of science. The first was experimental psychology, which instead of being an eclectic survey was taught from the point of view of the behaviorist,

B. F. Skinner. There was no pretense that the Skinnerian view was the only way to understand behavior, but it was taught by George Heise to show how behavior could be quantified and modeled. For me, it was to behavior what the simple equations had been for pulleys. It also included a required laboratory project in which I did a conditioning experiment on rats, which firmly established my interest in animals, their behavior, and what I could learn from the study of controlled behavior. The second was a course on the physiology of the nervous system taught by George Scott, which was skewed toward classic experiments which we repeated in the laboratory on frogs. It was interesting rather than riveting, but again it was the first introduction to the possibility of simple rules: all nerves carried the same impulses, but it was where the nerve started and ended that determined how a nervous system worked. The combination of the two courses opened up a new vista: if it were possible to measure behavior precisely and neuronal activity with equal precision, maybe it would be possible to study how the neuronal activity produced the behavior. While this was a novel thought for me, it was no intellectual breakthrough; the literature on the topic was substantial, as I learned in graduate school.

Among the other hodgepodge of courses I took in my exploration phase at Oberlin was the introductory economics course taught by Kenneth Rouse using Samuelson’s now famous textbook. This also demonstrated what could be learned by systematic analysis of a complex system, now an economic system rather than a nervous system. It was riveting, particularly national income economics, but after a follow-up course, I concluded that I liked the opportunity to test predictions of future behavior in the laboratory rather than gathering observations of past behavior. So by well into my junior year I settled on studying the nervous system. For this direction, there was another decision: medical school or graduate school, which I thought came down to how much I would like treating a single patient as opposed to solving a general problem.

I then had the opportunity to test my research abilities by attending a summer program after my junior year at the Jackson Laboratory in Bar Harbor, Maine, on a stipend provided by the National Institutes of Health (NIH)—the first of what was to become a lifetime of support for my training and research. A division of the Laboratory studied behavior, and I did a study supervised by John Fuller on whether there were differences in motivation for food between genetically obese mice and their normal siblings. I learned a lot about behavior (mice do not press bars like rats) and a bit about motivation in an incredibly profitable summer. I also decided that I probably did not have what it takes to do basic research, and I returned to Oberlin planning to apply to medical schools. I did apply, was accepted by several schools, and decided to go to Harvard. But as my senior year progressed, I increasingly had questions about my decision to abandon research. Would I really be able to remember all the disconnected facts of medical school? Did I really want to spend my life seeing patients? The latter was a realistic concern—I was never gregarious. I later scored off the bottom of the chart for psychology graduate students on a test of social interaction.

The turning point was when a fellow student said I should read Hebb’s then recent book, The Organization of Behavior. I bought it, read it through, and then reread the parts on “cell assemblies” and “phase sequences.” It was the first time I had a glimmer that it might be possible to explain at least simple behavior by understanding circuits of neurons in the brain. I understood that these were hypothetical circuits (but not how hypothetical), but this rekindled my thinking about brain and behavior in specific neuronal terms. Many years later I gave a seminar at Dalhousie University in Nova Scotia, where Hebb was an emeritus professor after retiring from McGill. He came, I met him, and I was able to express my appreciation for his inspiration. I doubt it was a notable event for him, but I was thoroughly rattled by his presence at the seminar.

After rethinking my decision for medical school throughout the fall and winter of my senior year, I decided that I was indeed most interested in experiments on the brain. I also thought that I would be happier in a university than a medical school environment, which for me has generated the ultimate irony: I have spent my entire life in the most rarefied of medical environments, the NIH. So I decided I should go to graduate school, not medical school. Sally Smith, a fellow student at Oberlin who I would marry later that year, was supportive of not only the decision at Oberlin but was immensely helpful and supportive throughout the hardest years of my life, in graduate school and in the postdoctoral years. My Oberlin advisor, however, thought I was “making a grave error.” But I think my father’s dictum of “work at what you love to do” had won out. While I have often wondered about the consequences of making the opposite decision, I have never doubted that I made the right one.

Deciding on graduate school in the spring of my senior year generated the obvious problem of getting into graduate school long after application deadlines. My Missouri draft board, which was always desperate to fill its quota because so many in my draft district went to college, also helped to keep my focus on getting into graduate school. The obvious route was to switch to being a graduate student at Harvard, but I did not see much study of the nervous system there. Harvard must have seen what I saw because within a few years Stephen Kuffler arrived and established the neurobiology group. Actually, the basic dilemma for graduate school was that behavior was studied primarily in psychology departments and the activity of the brain was studied in physiology departments. The closest combination of physiology and behavior was in an area referred to as physiological psychology and I opted for that. As in so many times in my life I got by “with a little help from my friends.” Steve Kaplan (who had pointed me toward Hebb) and Rae Kaplan were fellow students at Oberlin who went on to do Psychology at the University of Michigan in Ann Arbor, and they urged me to consider going to Michigan, and in particular pointed out the exciting experiments of James Olds. To make a long story short, I was admitted to Michigan largely through the benevolence of Bill McKeachie, the department chair. Olds took me on, sight unseen, as a research assistant.

Michigan and Jim Olds (1958–1962)

Psychology at Michigan covered the spectrum from learning in rats to clinical psychology. All graduate students took a first year course covering it all. For me such a survey was exceptionally valuable because I had continued my major in chemistry at Oberlin in order to graduate. Entering graduate students also took a set of proficiency tests in 10 areas of psychology. I passed only three: physiological, sensory, and developmental. When I had my first conference with my graduate advisor, he rightly asked why, if I had failed two-thirds of the tests, was I taking biochemistry and physiology rather than added psychology courses. My plan of course was to study not just behavior but brain and behavior and to do so I needed to know much more than what was available in the psychology department. Rather than backing off, I went on to take neurophysiology and neuroanatomy. This was possible because Jim Olds fully supported my logic, and of course I was just trying to construct a program that is now routine in what has become neuroscience.

In fact, I had gone to Ann Arbor in the summer before starting graduate school to start to reduce my course deficiencies in psychology, but the major benefit of the summer was the opportunity to work in the laboratory of Russell DeValois. This allowed me to see single-neuron recording in monkeys and participate in training monkeys to make color discriminations. I struggled through the summer to train a new world monkey to do a color discrimination, unfortunately one that Russ later showed it could not do. Russ was exceedingly generous, giving his time to someone who knew where the brain was but not much else. The experience sensitized me to the advantage of training monkeys, an advantage I put to use nearly a decade later.

I should say that I almost certainly got the position with Russ because he had graduated from Oberlin. At Oberlin I believe he had been one of the last of Stetson’s drivers, students who drove the Chair of Psychology, Raymond Stetson, to and from the department because of an infirmity. One of the earlier drivers was Roger Sperry, who many years later published a paper on mind and brain (Sperry, 1952) and credited Stetson for many of the ideas.

I basically went to Michigan because I was fascinated by the work of James Olds, who became my mentor during graduate school. Jim Olds was famous for his discovery with Peter Milner that electrical brain stimulation could act as a reward in addition to its well-known aversive or arousal effects. Before doing his postdoctoral work, the closest he had come to thinking about the brain was probably his article on “A Neural Model of Sign Gestalt Theory” while he was at Harvard (Olds, 1954). He decided on a change in direction, went to McGill to work in D. O. Hebb’s laboratory, and there joined a project with Milner exploring arousal following brain stimulation. Jim told me that he barely knew which end of the rat had the brain and that he learned everything he knew about rat behavior, implanting electrodes, and doing brain stimulation from Milner, whom he described as a brilliant experimenter. He thought that, while the entire experiment was dependent upon the skills of Milner, he did make a major contribution: he noticed that when they stimulated the rat while it was in a particular region of an open field, the rat tended to return to that part of the field. Jim told me this story in about 1958, and I did not have the good fortune to meet Peter Milner until nearly a half century later, in 2007. When I asked about his work with Olds, Milner’s description of the discovery was identical to that of Olds, including that Olds did not know one end of the rat from the other, but that it was Olds who made the critical observation in the open field test. I found this a remarkably parallel description by the protagonists, even though the descriptions were separated by nearly half a century. In their classic experiments, they gave the rat a bar to press to produce brain self-stimulation, and the results were immediately recognized as changing the landscape of the brain basis of motivation (Olds and Milner, 1954). The serendipitous discovery of brain self-stimulation catapulted Olds to prominence. I think it also shaped the way he did science.

My approach to science and my fundamental strategy for doing research was subsequently shaped by Jim Olds, and I am forever in his debt. His tragic drowning in 1976 prevented me from ever directly acknowledging my gratitude to him. I could not have done so earlier because it took me some time after graduate school to appreciate how fortunate I had been to work in his laboratory. And work I did. At that time Jim had a system for running groups of about 20 rats, each in its own Skinner box with a bar to press. One test was for the rewarding effect of stimulation. The rat pressed the bar to electrically stimulate a site in its brain, a counter recorded the number of presses, and in successive periods of about 10 minutes the current was raised, which gave a graph of bar presses versus stimulation current. The second test was for aversive effects of the same stimulation at the same site also at different current levels. Now the current was pulsed through the electrode at regular intervals and the rat could press the bar to escape the stimulation; the higher the rate of bar pressing, the greater the presumed aversive effect of the stimulation. Some sites produced self-stimulation, some escape, and some both, which Jim called ambivalent sites. There were some four or five groups run every weekday, and mine was the late afternoon run. I did this throughout my first year of graduate school, from September 1958 until the following summer. The work was tedious but tolerable, and it showed me how to do serious investigation of behavior: build a machine to produce data in adequate amounts to draw substantial conclusions.

I did not get off to a great start with Jim. As I was starting in his laboratory, he gave me a précis of what the experiments I was running were about, and he gave me his reprints to read. I wanted to make sure I was not missing anything (the days before Pub Med!) and I asked him, is that all? He cocked his head as he was wont to do when slightly irritated or amused, and said, “I have just given you my life’s work, and you ask me, is that all?” A month or so later I raised my arms to put on my lab coat, hit the bar going across the room from which the stimulating leads went down to each rat, and knocked the whole 20 foot bar to the floor. This would have been easily fixed were it not for the 20 little pools of mercury that acted to minimize twisted leads when the rats rotated in their boxes. So there was a mercury spill that required cleanup and repainting. I shuddered to think what Jim would do after the debacle, but he said nothing, presumably realizing my mortification and knowing that it was not the first time it had happened.

Jim Olds was direct and forceful, that is to say blunt, and as an insecure graduate student this was intimidating. Few graduate students continued working with him, and I was the first to do so from start to finish. A watershed for me occurred in the second year when for an experiment on cats we needed to take a sick cat with an implant to a veterinarian. At that time, the only way to have an animal treated was to take it to a small animal veterinarian, but I was loath to take a cat with a cranial implant into a waiting room. So we took another unimplanted cat with the same symptoms and asked for medication for both of them. Jim got word that I had paid to have a normal cat medicated, and he berated me for taking any cat that had just sneezed to the vet. At a pause, I explained my logic, and he cocked his head, and said, “That was perspicacious of you.” When I looked up the word, I realized it was a compliment. I had an easier time with Jim after that.

When I arrived at Michigan, Jim had told me that undergraduate rules for success no longer applied; as a graduate student grades were irrelevant, discovery was all: “Do what needs to be done to satisfy academic requirements, but direct your energy to research.” I took him seriously, and inadvertently tested his resolve. I took his course on motivation, got a C+ (comparable to an unthinkable D at Oberlin), but he never said a word. When I had enough credits for a Masters degree, I took the form for Jim’s signature, but he refused to sign it. If he did, he said I might think I had accomplished something, which I had not. These were good examples of the guidance I got from Jim, forceful and almost always correct. Finally, he would not permit any time to be taken from research for teaching—it was just a distraction from thinking about your research. He only relented after I had finished writing my thesis in my fourth year. I jointly taught an undergraduate psychology course, and, while I thoroughly enjoyed doing it, Jim was right on the time it took.

I came to realize that Olds regarded my first year of monotonous measurement of self-stimulation as both training and a test of my ability to stick with a project. I seemed to have passed the test, because toward the end of that first year he suggested a project that I would do largely on my own. The goal was to explore an aspect of self-stimulation that he thought was promising: whether the motivationally relevant cluster of nuclei in the amygdala produced rewarding or aversive responses in rats. I already knew how to do everything from electrode implanting to behavioral testing, so the project progressed rapidly, and I was able to show that stimulation of the corticomedial division of the amygdala produced more reward behavior and the basolateral division produced more aversive behavior.

By my second year of graduate work, Jim Olds had shifted his interests from mapping the motivational effects of brain stimulation to exploring how brain stimulation might provide the reinforcement for learning. He was looking for changes in activity during learning in single neurons in the brain. My contribution was to make the microelectrodes, and I was able to make stainless steel electrodes using insect pins and tungsten electrodes using the Hubel method (Hubel, 1957). They were probably not great, but they did record some cells some of the time. I then recorded cells in a number of projects after my amygdala experiments, including looking for changes in neurons before and after learning and asking whether there were changes in the brain related to visual attention. None of these projects produced any useful results, but they introduced me to learning and attention and emphasized to me the value of exploring where the results were uncertain. I had imprinted on Olds own exploratory method.

In the middle of my third year, Olds suggested that I use the selfstimulation study of the amygdala that I had done in my second year as the central part of my Ph.D. thesis. I coupled this with a largely unsuccessful attempt to establish a neuronal basis for self-stimulation by trying to see differences in neuronal activity in the amygdala locations where stimulation was rewarding as opposed to aversive. I gave my first scientific talk on the amygdala at the spring meeting of the American Physiological Society on a 1-day trip to and from Atlantic City. It was a talk on the afternoon of the last day of the meeting and there was even a question. When I sat down, the person next to me said, “That was an excellent talk” (due to Olds demanding coaching) and asked, “Do you know who asked the question?” I had not a clue. He said it was Alexander Forbes, a Professor at Harvard, a leading physiologist, and clearly one of the most considerate scientists of all time.

The trip was rushed and tense because our first child was due, but William Robert did not arrive until several weeks later. He was the most active boy imaginable and was into everything as soon as he could crawl. The only advantage of our tiny apartment was that we did not have much for him to get into.

I finished my thesis and submitted it in 1962. Jim did not approve of my prosaic title, “Self-Stimulation and Escape in Response to Stimulation of the Rat Amygdala,” but I thought it should convey exactly what the study was on, and his view was that it was my thesis. My memory is that the editor of the Michigan Daily, Tom Hayden, the California activist to be, was also taken by my title. He wrote an editorial related to mindless science and used my title as his inspiration. The title of our published paper became “Amygdaloid Stimulation and Operant Reinforcement in the Rat” (Wurtz and Olds, 1963).

As I neared the end of my time as a graduate student I was obviously thinking about what research direction to take. Vernon Mountcastle had given a seminar on his elegant recording in the somatosensory system, and I left thinking that he was listening to what neurons were saying while I was electrocuting them. Continuing brain stimulation did not seem very promising, and it turned out that real progress did not come in this area until the ability to manipulate transmitters and their receptors became possible much later. But the major advance for me came in a summer I spent at Woods Hole in 1961 as a Grass fellow. I had applied with the strong support of Olds and a project that proposed to study the brain of the squid during a conditioning task. This was to be done in my 2 months stay, which must have given the review committee a laugh, but it also fit with the Grass-sponsored Alexander Forbes lecture given by J. Z. Young, the world’s expert on the squid brain. My experiment did not work. I managed to record from the awake but restrained squid, but only from the optic nerve. The salient event of the summer, however, was a talk by David Hubel at one of the regular

Friday evening lectures. I had been unaware of the work and found it mesmerizing. David stayed several days after the lecture, and I was able to talk with him. He also invited me to stop by his laboratory at Harvard on my way back to Michigan in order to sit in on an experiment in which he and Torsten Wiesel were mapping the orientation specificity of V1 neurons using long penetrations. He even put us up overnight and invited us to dinner. To say that it was a life-changing visit would be an understatement. Unfortunately, during the dinner break the cat died, and it was only much later that I realized that they paused for dinner at home only occasionally. I thought for years that by associative learning I must be linked in the minds of Hubel and Wiesel to a dead cat.

Had there been a possibility of doing a postdoctoral fellowship with Hubel and Wiesel, my research direction would have been set. But that turned out not to be possible, and this let other issues command my attention. It is difficult now to appreciate the intensity of feelings about the threat of nuclear war that prevailed then. I had rung door bells in Ann Arbor for Kennedy, had listened to his inaugural speech (by taking the ground wire off the recording amplifier used to record neurons from the rat brain), but was dismayed at his failure to do anything other than increase the nuclear arms race. It all led to the inevitable question, Why would I be working on the brain if the world was about to be blown up in a nuclear war? So I decided to split my time for the next 2 years between being on the staff of the Committee for Nuclear Information in St Louis and a research fellow at Washington University. I expected Jim Olds to be disappointed with my direction, and he was. He was also remarkably supportive of my effort, but said he hoped I would return to science. His parting comment was that he thought I could become a department chair. When he saw my crestfallen look, he quickly added that he meant it as a compliment.

St Louis and Banning the Bomb (1962–1965)

The philosophy of the Committee for Nuclear Information, which consisted of scientists and physicians in St Louis, was that the issue of nuclear weapons was a political not a scientific one, but that intelligent political decisions depended on an understanding of the underlying science. It was the public that needed this understanding because that was the ultimate source of decisions in a democracy. In hindsight, this sounds a bit utopian, but in fact changes in political direction frequently do result from a welling up of public support or disapproval, as in the case of the Vietnam War. My role was as a scientist, contributing half my time to research and to articles that appeared in their publication that had a small circulation, but whose influence was magnified because its articles were frequently picked up by newspapers. A major leader was Barry Commoner, who had a keen eye for putting information out in ways that would attract attention. I also benefited from his ability to dismember my articles, particularly one on the effects of nuclear weapons (Wurtz, 1963). The decision to move testing underground, rather than ending it, was a brilliant political maneuver by the Kennedy administration. For the world it was a disaster because the nuclear arms race continued unabated, but the public interest in the nuclear threat largely vanished. For the Committee this led to discussions of what to do next. The key point that emerged was the recognition that nuclear fallout was only one environmental hazard, and that the real issue was the environment itself. In an exceptionally foresighted move, the group gave their publication a new name: Environment.

I felt that I had not accomplished much in the time I had spent with the Committee, nor had I done any serious research. At this point I realized that attempting to go in two major directions at the same time (ending nuclear war and understanding the brain) was beyond my capacity. Considerably disillusioned, I went back to brain research.

I was cheered, however, by the birth of our second child, Erica. She was not only a beautiful and happy child, but routinely demonstrated the phases of sleep that I was studying in one of my lab experiments. One night in particular, I was caring for her while Emilio Bizzi and I were discussing rapid eye movement sleep. Erica demonstrated the transition directly from wakefulness to rapid eye movement sleep that babies do readily, avoiding the slow wave sleep of adulthood. With William and now Erica I resolved to at least take Sunday off and went for picnics and hikes to many of the places near St Louis that I had gone to as a child with my father and mother. Bill and Erica liked the trips; their favorite was to the zoo.

My research fellowship at Washington University was in the Physiology Department, but my intellectual mentoring was in the Neurology and Neurosurgery Laboratories where interest in the brain was then centered. I continued on lines I had begun in Olds’ laboratory, starting with an attempt to see whether slow potentials in the brain, thought at least locally to reflect dendritic activity, changed during learning. But James O’Leary, chair of the Neurology Department, wisely thought anyone who studied slow potentials ought to know about their origins. Because it had recently been shown that the potentials varied with the phases of sleep, he suggested that I start by studying sleep, and my direct mentor Sidney Goldring concurred. So I adapted the laboratory’s DC electrodes to record from cats during sleep as a route to understanding the potentials (Wurtz, 1966). The more I learned, the clearer it became that I had no idea what the origin of the slow potentials was. The message I took from this series of experiments was that while recording brain electrical activity during an animal’s behavior was a frontier of neurophysiology, it was only a frontier if one knew what the source of the activity was in the brain.

I therefore switched to another project related to learning where I knew what I was recording, in this case in the marine mollusk, Aplysia californica. The experiment was to test Hebb’s hypothesis that a synapse was strengthened when the excitatory postsynaptic potential (EPSP) was followed by an action potential in the postsynaptic neuron, and weakened when it was not. Two factors made the test possible. A graduate student, Vincent Castellucci, was recording from Aplysia, and I was impressed with his skill and the ease with which the intracellular recording showed the EPSPs. The second factor was that Sid Goldring had participated in the LINC evaluation program, a program based at MIT to introduce computers into the laboratory, and the program had provided a computer which he had brought with him. I learned what it could do and how to program it (in assembly language). I realized that I could use the LINC “on line” to recognize a particular EPSP shape and have the computer within milliseconds pass current through the postsynaptic neuron to produce an action potential. Over time that EPSP should then come to more effectively drive the neuron. Vincent was a wonderful collaborator and, together with a summer student, we programmed the computer and did the experiment (Wurtz et al., 1967). It did not work; we found no effect of the contingent depolarization of the postsynaptic neuron. With the benefit of subsequent knowledge, I realized that a key factor might have been that I was depolarizing the cell body but in this invertebrate the synapses were down on the axon. To this day I regard this as one of my cleverest experiments, but of course a failed one.

I also realized that my understanding of neuronal physiology was very limited and, if I were to study neurons in the brain, I ought to know more about them. Many of my discussions in St Louis had been with Emilio Bizzi who had moved to Ed Evarts’s laboratory at the NIH. He urged me to come to the NIH and, after I visited him there, I could see his point. Largely through the good offices of O’Leary, Goldring, and Bill Landau in St Louis, Karl Frank at NIH agreed to let me come to use space that was available for a year. I was reluctant to leave such a supportive group in St Louis, but for a year it would be worth it. Just before I left I had the opportunity to give a talk at The Needlework Society, run that year by Bill Landow who gave my talk on slow potentials during sleep the title “Shifts That Pass in the Night.” My departure for the NIH was delayed by the terminal illness of my father, and I did not leave for the NIH until October 1965.

Developing Visual System Recording in Awake Monkeys at the NIH (1965–1969)

At the NIH I joined the Laboratory of Neurophysiology, which was jointly run by the National Institute of Mental Health (NIMH) and the National Institute of Neurological Diseases and Blindness (NINDB) with Wade Marshall of NIMH as chief of the Laboratory and Karl Frank of NINDB as chief of the Spinal Cord Section within the Laboratory. I quickly learned that names did not mean much, and that there was little relevance of which Institute you worked in. In the Spinal Cord Section, Karl was studying Aplysia; Phil Nelson, Norm Robbins, and Gerry Fischbach were studying development; and Bob Burke was actually studying the spinal cord. I continued recording from Aplysia and did reach my goal of understanding more about neuronal function, which of course then led to the question of whether to continue these experiments. I talked to and visited a young psychiatry resident at Harvard, Eric Kandel, whom I was convinced was actually succeeding in studying learning in Aplysia and, had I continued in that direction, there is no doubt I would have gone to Eric’s laboratory. But I realized that I missed studying the rich behavior of higher animals, including measurable cognitive behavior, and I began thinking more about returning to the study of neuronal systems in the brain of mammals.

I was increasingly drawn to the primate because of the ability to control its behavior through training and because much of behavior was so similar to that of humans. This interest was heightened by my contacts with Edward Evarts at the NIH who was studying limb movement in awake monkeys. I also returned to thinking about Hubel and Wiesel’s work and the insights into the organization of neurons that they had produced. Specifically, I thought that if I could do the Hubel and Wiesel experiments in awake monkeys, I might see activity beyond the visual responses in cortex, including correlates of such cognitive functions as perception and attention. As if all this would be in V1!

The obvious place to do this was Ed’s laboratory, but Ed had no position open. There was, however, a position in Ichiji Tasaki’s Laboratory of Neurobiology in NIMH. Tasaki was famous for discovering saltatory conduction of nerve impulses along myelinated nerves. He was then concentrating on nerve conduction in squid, including experiments that did not agree with Hodgkin and Huxley’s conclusions, which largely isolated him from the larger NIH community. He had also recorded from the brains of cats (I believe he was the first to have recorded single neurons in the lateral geniculate nucleus; Tasaki et al. 1954), and he headed a Laboratory that was intended for the study of the nervous system at many levels. I applied for the position and again almost certainly got it on the basis of the recommendations from St Louis because Tasaki knew my St Louis mentors well, having spent several years there shortly after the end of World War II. I explained to him what I wanted to do: study vision in awake monkeys. He did not wince or even blink, and summed up our conversation by saying, “I learn from Professor Squid, you learn from Professor Monkey”. Over the decade I was in his laboratory, I came to realize how outstanding a scientist Tasaki was both at the bench and in his innovative thinking. He was happy to have me, in part because I was off struggling with my Professor while he communed with his. I began in Tasaki’s laboratory on July 1, 1966. Instead of returning to St Louis in a year, I have stayed at the NIH for over 45 years.

The problem with studying the visual system in the awake monkey was the rapid or saccadic eye movements that moved the retina several times per second. These saccades are integral to our remarkable vision; our one high-resolution region in the fovea is directed to successive regions of interest by the saccades. Each time the eye moves, however, a stimulus falling on the receptive field (RF) of a neuron, as in Hubel and Wiesel’s experiments in anesthetized cats, would be displaced to a different part of the retina. If I were to study the visual system while it was actually being used for vision, I would have to solve this problem. The solution was obvious: study the RF of a given neuron while the monkey fixated for several seconds in order to obtain a reward, then let the monkey make saccades for a few seconds and then require it to fixate again. Instead of a continuous period for the analysis of the RF in the anesthetized animal, I would have a series of two to three-second time windows in which to study the RF. I had gone up to Hopkins to visit David Robinson’s laboratory and seen that Albert Fuchs had trained the monkeys to make saccades and pursuit eye movement to obtain a reward (Fuchs, 1967). Why should training the monkey not to move its eyes be any harder?

I got the answer to that quickly enough; monkeys liked to fixate but on what they chose, not what I chose. One look at what I wanted them to look at, and they were done. I was clearly going to have to reward them just for fixating. Here I followed one of the lessons from Olds’ laboratory: if you need to shape behavior by repetitive trials, build a machine to do it. I built a circuit out of a type of logic cards that I had used at Washington University. Each of these DigiBit cards had a logic element, such as an And gate, Or gate, or Flipflop, or a switch for an input or a relay for an output. It required knowing some tricks to get the circuit to work, but the circuit was in principle logical and therefore simple to diagram. I built a circuit that turned on a slit of light on a screen in front of the monkey when the monkey pressed a bar, and after a variable length of time, changed the slit orientation. If the monkey indicated it saw the change by releasing the bar, it received a fruit juice reward. For the stimulus I found a small indicator light that was designed for soft drink machines which had nine bulbs that projected through one of nine lenses onto the back of a small plastic screen. Changes of slit orientation were made by turning off one bulb and turning on another. It was a simple and rugged device that we continued using in the training setups for many years.

The goal of the training was to make the change in the stimulus so small that the monkey would have to direct its fovea toward it in order to detect the change. The training started out with large slits and large orientation changes, progressed to smaller slits and smaller changes, and ended with a small spot that just dimmed. The first monkey learned the task with amazing ease. Ethel was, however, a high-strung monkey and had the habit of biting her nails (a trait I have never seen again). By the ease of her training, I concluded she was an ideal monkey for the more complex tasks I expected to move on to promptly. I then began training another monkey and thinking about recording.

My laboratory room was in NIH Building 9, which housed all of the behavioral-based monkey experiments, and was one of the early NIH buildings. It was well worn and was scheduled for demolition. Forty-five years later it is still in use, but it is inadequate for housing monkeys and can only be used for humans. Another resident of Building 9 was Ed Evarts, who had just worked out the techniques for restraining the monkey’s head and implanting recording cylinders in the skull (Evarts, 1966; Evarts, 1968a; Evarts, 1968b). Ed had also modified a microdrive developed by David Hubel for advancing the microelectrode in the brain of awake cats (Hubel, 1959). The NIH had a central machine shop with superb machinists where Ed had all his parts made; Ed simply made me a list of what parts I would need and said to give the shop the list. I did just that, and I had what I needed within a few weeks. Setting up for recording was a dream, and Evarts always went out of his way to answer any question and address any problems. I also had had the generous help in learning how to handle the monkey from Hal Rosvold, who was Chief of the Section on Neuropsychology. He and Mort Mishkin, to whom I directed many a naïve question, were in the same building. It is difficult to imagine a more ideal environment for what I was trying to do.

I had learned to do the actual recording from awake monkeys by sitting in on experiments with Emilo Bizzi, who was then finishing up his experiments on the frontal eye field before moving to MIT. His recording room was in the dismal basement of Building 9, as was my office, and both were reached by an elevator whose every move seemed likely to be its last. I had already watched an experiment in my earlier brief visit to Hubel and Wiesel’s laboratory, so I knew what I needed the monkey to do. I also watched the surgical preparations and procedures of Mort and the specific implant procedures of Ed. So in November 1966, I did my first implant on the second trained monkey, putting on an Evarts’ head holder, and a recording chamber placed just anterior to the occipital bony crest.

During the training procedures I had to rely on the monkey’s performance to evaluate whether it fixated. With the monkey’s head now restrained for recording, I could at last measure the eye movements to see that it was actually fixating. Over the summer I had worked out an eye movement recording system based on the well-established electrooculogram that measures a DC potential across the eye; as the eye turns, the amplitude of the recorded potential changes. I pasted electrodes onto the monkey’s shaved skin near the eyes and, of course, this had to be done before each session. It was immediately clear that the monkey was fixating for the several seconds that I thought it was. It was equally clear that I could not measure the small drifts and microsaccades during fixation, so I would not know anything about such small movements. In order to minimize the effect of any residual eye movements, I resolved to study RFs that were at least 5° from the fovea.

I thus had the following: a monkey trained to fixate; a recording chamber over what I hoped was V1 cortex (then referred to as striate cortex); a microdrive moving a glass coated platinum electrode (Wolbarsht et al., 1960) that Ed had found would penetrate the dura; the EOG system that I hoped would record eye movements; a projector with a solenoid operated shutter that would project a stimulus on the RF just for the time that the monkey was fixating; all sequenced by DigiBits. While I had not done any of the specific tasks required by this experiment, I had had some experience in doing all the components such as making microelectrodes, training animals, and recording from neurons (Michigan), and recording DC potentials and DigiBit programming (St Louis). But here everything had to work at once, and nothing could be tested until the monkey’s head was restrained and that required that first surgery. Learning to get the eye electrodes pasted on so they stayed on, getting the microelectrodes through the dura, isolating spikes, and then getting the monkey to do the fixation task, all at the same time was the challenge I had not adequately anticipated. Over several intense weeks, this all worked well enough so that I could finally try to find the RF of an isolated V1 neuron.

My first goal of course was to see if the fixation in the awake monkey was good enough to verify that V1 neurons responded preferentially to oriented slits of light rather than just to spots of light. On the day before Thanksgiving, 1966, everything worked at the same time for the first time. I had a well-isolated neuron that responded much better to slits than to spots and best to a slit oriented slightly off the vertical. I was very thankful that Thanksgiving.

I was able to verify the orientation selectivity in the next week, but by that time the dura over the brain was sufficiently tough that I could not get electrodes through it and the recording on that side of the brain was over. I was incredibly relieved that the fixation was good enough to record neurons that showed orientation selectivity. I had essentially done the Hubel and Wiesel experiment just as I had seen them do it, but in the awake monkey. On the other hand, I had done nothing else. Because the method did work, I then needed to work on presenting different stimuli, collecting and storing the data, and making sense of it. Here my previous experience provided me with little support, and I spent most of the next year catching up on presenting the stimulus and looking at the neuronal activity. For the stimulus I had initially used a series of slides with several slit sizes and with eight orientations for each size accessible in a Carousel projector. I managed to replace this with a series of slits that I could rotate using a dove prism, and eventually with a slit diaphragm that produced a slit of any size that I rotated by hand on successive trials. This was all mounted on a drill press stand that allowed me to direct the slit toward the part of the field where I had located the RF with a handheld flashlight.

Displaying and saving the neuronal responses was more of a challenge. I first needed some way to convert the spikes into a pulse that could more readily be displayed and eventually stored. For this I copied the “raster” that Ed had built (Wall, 1959). A Schmidt trigger first converted spikes greater than a given amplitude into a voltage pulse, and then these pulses were displayed as dots on the sweep of the oscilloscope by intensifying the beam at the time of each spike. Ed’s device also had multiple discrimination channels so that up to three spikes could be separated. Ed laughed when he saw that I had duplicated the channels because in the years he had used it he had recorded two discriminable neurons only occasionally, and he thought if he recorded three at once it would be declared a national holiday. Storage of the data was on a Polaroid print of the raster on the storage oscilloscope screen or of individual spikes on a sweep triggered by the DigiBits. Many other problems had to be solved, but with a little flexibility in stimulus presentation and some data storage, I could proceed with experiments.

What I found was exciting in one respect, but disappointing in another. First and foremost I was able to identify neurons that responded best to oriented slits and to verify their distinction between simple cells and complex cells. I also found many neurons responding to spots as well as to slits (nonoriented cells) that were not seen in cats but were in monkeys (Hubel and Wiesel, 1968). I also found neurons responding to motion better in one direction than the opposite direction as found in the cat (Pettigrew et al., 1968). I was at the same time working on the visual response to stimuli during saccades, so the first publication on visual responses of V1 neurons was not published until 1969 (Wurtz, 1969c). On the one hand, I was disappointed that I did not see something new for my efforts, which I think was in part due to the qualitative analysis I did and in part due to my wild expectations of what V1 cortex might be doing. I would not, however, have expended all my effort just to show that Hubel and Wiesel were wrong because I was counting on their observations as the springboard for a leap into understanding the neuronal basis of cognitive function.

At this point, I did not get a lot of reinforcement from the field. This is understandable because I had not discovered anything new, just that what Hubel and Weisel had so elegantly demonstrated was readily observed in the awake monkey. I was encouraged when Torsten Wiesel made a brief stop at my laboratory, and when Gerald Westheimer viewed the verification of Hubel and Wiesel’s results in an awake animal as an essential advance in studying the visual system. Ed Evarts had been cautious about the outcome of the experiments because he worried that the quality of fixation of the trained monkeys might not be adequate to keep the stimulus on the RF, but he was impressed by the consistent visual responses to the same stimulus over a series of fixations. I also thought that, if a technique was worth the bother, the results obtained by using it would prove the point. So I did not think I needed any methods paper beyond the methods section of the V1 paper in 1969. This was a mistake that probably slowed adoption of the technique.

The Superior Colliculus (1969–1972)

After determining the RFs of V1 neurons, the next experiments I had in mind were the obvious ones related to how the visual system dealt with the incessant movements of the eyes. The particular question I thought was “low hanging fruit” was how the visual system reduced the blur of the visual field swept across the retina with each saccade, a process referred to as saccadic suppression. A controversy in the early 20th century was whether there was a “central anesthesia” that blocked out vision during the saccade (Holt, 1903) or whether there was simply a reduction in sensitivity (Dodge, 1905). Now I had the opportunity to address this question directly because I could record neuronal responses at the first cortical neurons in the visual pathway. Did they respond, or was there a central anesthesia that turned them off? They responded. In addition, by comparing how the V1 neurons responded as the eye swept over the visual field to how they responded to comparable visual motion when the eye was stationary, I could show a qualitative similarity that clearly ruled out central anaesthesia (Wurtz, 1969a; 1969b; Wurtz, 1968). I had the satisfaction of having discovered a little something at last.

If I did not see the active suppression in V1 perhaps I would see it in the other branch of the visual pathway that went not to cerebral cortex but to the roof of the midbrain, the superior colliculus (SC). So in early1969, I made some recordings in the brainstem that I hoped were in the superior colliculus, did histology, and found that I was indeed occasionally in the SC. I then shifted recording to the SC, but there was a big difference between SC and V1. Here I had no previous recording to simply verify. I thought I could get a general idea of the activity in the structure and then proceed with my planned experiments, which turned out to be exceptionally naïve. The next 3 years were going to be spent beginning to figure out the structure and function of the SC, not its relation to saccadic suppression. This was to be the first of many shifts in my experimental direction in which I started looking for one particular brain mechanism but would end up studying quite a different one.

My trepidation at the task was ameliorated by Michael Goldberg descending onto the scene in the guise of my first postdoctoral fellow. I say guise because within a year he had become a full collaborator. Mickey as a medical student at Harvard had spent a summer in Hubel and Wiesel’s laboratory. There he heard Peter Sterling’s favorable comments on my work after hearing my maiden talk at the fall American Physiological Society meetings (Wurtz, 1967). Mickey was specifically interested in the NIH postdoctoral matching program because of the doctor’s draft which funneled young doctors to the raging war in Vietnam. Happily, Ed Evarts did not have a position available, but Tasaki had provided me with one, so I did. The match was made, and Mickey showed up on July1, 1969. His coming was in my view the only known benefit of the Vietnam War.

But in spite of my amazing good luck in having Mickey come to the lab, the SC was still recalcitrant. We found neurons with visual responses as expected but also discovered neurons that discharged before saccades. To our dismay we also found a host of other neurons with many characteristics that we later realized were from the deepest layers of the SC. Before realizing that, the results were so confusing that after a particularly trying day, Mickey opined that he now understood why there was an SC in the brain: one example of every type of neuron in the brain had been placed there to provide practice for neurophysiologists.

With the aid of marks made by passing current through the microelectrode, we gradually came to recognize that neurons with only visual responses were in the superficial layers, and those with saccade-related activity were in the intermediate layers. We then concentrated on these neurons. Each time we obtained histology, however, we had to euthanize a trained monkey, so the problem of localizing where we were recording was a costly one, but it did give us a chance to look at the results we had while training the next monkey. Not all marks could be found, and correlation with recorded neurons was often ambiguous. The ultimate setback was at last having an absolutely certain mark on a nicely stained section perfect for an illustration but with a fatal problem: it had a fold in the mounted and stained section. This we remedied by placing a strip label over the fold that identified the SC layers (Fig. 1 in Wurtz and Goldberg, 1972a).

The tasks we used to explore the relation of the neurons to behavior became increasingly varied, and each time we changed the task, we had to change switches on the DigiBit control panel. For more complicated tasks, we had to change the wiring on the back panel. Figure 16.1 shows us with the recording equipment and the inset shows the back of the DigiBit panel. We resolved to switch to a computer, but not until finishing the ongoing set of experiments. We realized that we could study the brain or the computer, but not both. We worked diligently for over 2 years trying to put the SC pieces together. I remember recording one night when the whole laboratory building was totally abandoned except for us. It was the night of the moon landing. We decided to forgo watching TV because we were having particularly good luck recording; inner space won out over outer space.

Results of our experiments were published in four papers in 1972 after a note on saccade-related neurons in Science early in 1971 (Wurtz and Goldberg, 1971). The first of the four was on neurons with visual responses (Goldberg and Wurtz, 1972a), which established that the SC required only spots of light rather than oriented slits, had large RFs compared to V1, and had little directional selectivity. The latter point differed from the finding of directionally selective motion neurons in the cat (Sterling and Wickelgren, 1969), and we labored over several monkeys to make sure our failure to find them was not our error. They are not there, and it was not until later that directionality in the interaction of center and surround in SC was recognized (Davidson and Bender, 1991). We did see some suppression related to saccades, but this original purpose in studying the SC was lost in the excitement over all the other unexpected observations.

Fig. 16.1    Bob Wurtz and Mickey Goldberg in 1971 with the electronics used for recording from the superior colliculus. The inset shows the wiring of the DigiBits used to control the monkey’s behavior. The white tags indicate which wires had to be moved each time the behavioral task was changed and the correct pin location for that wire on each task.

The second paper was on enhanced visual responses related to shifts of attention (Goldberg and Wurtz, 1972b; Wurtz and Goldberg, 1972c), or more exactly our inference that the monkey attended to a stimulus before it made a saccade to the stimulus. We noticed this enhanced response by just listening to the visual response on the loud speaker; the response seemed stronger when the monkey made a saccade to the stimulus than when it did not. We devised a simple task in which we looked at the response to a spot of light in its RF while the monkey fixated and when it made a saccade to the same spot of light. The key criterion of an attention experiment was met because it was the same stimulus in both parts of the task, but the enhanced response only occurred when the monkey shifted its attention to the stimulus to use it as the target of the impending saccade. The enhanced response was not just a general arousal response because it did not occur with saccades to other regions of the visual field. To our knowledge this was the first potential single neuron correlate of attention found in the primate brain. It also was cited as one of the key observations underlying the development of the motor theory of attention by Rizzolatti and his collaborators (1983).

The third paper described the saccade-related neurons that became active before saccades to limited regions of the visual field (Wurtz and Goldberg, 1972a; 1971). We coined the term “movement field” for this region of the visual field as a parallel term to receptive field. The saccade-related activity was before the saccade and we struggled to avoid referring to it as a response to the saccade, a problem the current term “response field” for both visual and saccade activity ignores. We showed the size of the movement fields, that they were centered like the visual activity in the contralateral visual field, and that activity was related to saccades and the fast phase of nystagmus. The fourth paper tested the contribution this circuitry made to the generation of saccades by making electrolytic lesions in the SC and then testing the monkey’s ability to make saccades to the region of the visual field related to the lesion (Wurtz and Goldberg, 1972b). The result was astonishing. After seeing all this machinery from visual responses, to a shift of attention, to saccade-related activity, we expected the monkeys to be devastated by the SC lesion. They were not. Within a day when we tested them they could readily make saccades to the affected visual field, and they became better and more accurate over the following days, showing that whatever it did, the SC was not essential for the generation of saccades. What did not recover was the latency of the saccade; it was always lengthened no matter how long we studied the monkey after the SC lesion.

Use of the awake monkey in the SC experiments allowed us to show the transition from sensory processing to the generation of movement in the same structure, and to gather numerous clues on other modulations. But we missed working out the map for visual and movement processing (Robinson, 1972) because we did not use electrical stimulation as others did (Stryker and Schiller, 1975). We did, however, identify activity that we deemed was related to a cognitive function: visual attention. We therefore regarded the SC as playing a more global role than just the generation of saccades. This was in contrast to the view of the Schiller laboratory that the SC was more specifically related to saccade generation. These differing views were summarized in two articles in the same symposium in 1972 (Schiller, 1972; Wurtz and Goldberg, 1972d), but the resolution is clear: it probably contributes to both. In addition it is not an entity unto itself, but rather one step in a pathway descending from cerebral cortex and, as we found later, a step in a pathway ascending to cortex as well.

Refining Recording in the Visual System of Awake Monkeys

After recording in visual cortex and superior colliculus, it was clear that the visual system and its relation to perception and to eye movement could be studied in awake monkeys. The problem was that the barriers to doing so were substantial. It is worth a digression to emphasize the developments that have made recording in the visual system of awake monkeys more generally accessible.

The method of restraining the head and recording single neurons in monkeys was worked out by Evarts and, while there have been many changes, his fundamental methods are in use today. Recording eye movements was more of a problem. The best method was the magnetic search coil technique of David Robinson and Albert Fuchs (Fuchs and Robinson, 1966; Robinson, 1963) that gave remarkably low noise eye position information using a coil of wire surgically placed under the eye muscles. The drawback was that placement of the wires under the muscles could produce strabismus in the implanted eye. Since I was trying to study the normal functioning of the visual system, I was reluctant to incorporate a technique that could produce double vision. I therefore used the EOG method because it could produce no harm. But it was an awful system with noisy signals that were acceptable for recording the change of eye position saccades but had too much drift to register eye position. In planning experiments with Stuart Judge to see what would happen to V1 neurons when the visual image was stabilized, it became essential to measure the eye position exactly in order to produce the stabilization. After trying a number of approaches, including a contact lens carrying the eye coil as was done in humans and scleral reflection as was also used in humans, the best solution seemed to be a slight modification of the Robinson/Fuchs technique. Instead of threading the wire under the eye muscles and running the possibility of damage to the muscles, the new approach simply placed a preformed eye coil in front of the muscles but still under the conjunctiva. The report of the technique by Judge, Richmond, and Chu (1980a) is probably one of the most cited papers from our laboratory. It was a minor change, as was Robinson’s use of multistrand wire in the coil (so that one wire breaking would not end the usefulness of the coil), but the improved eye movement recording was a critical step in making the study of the visual system in the awake monkey a standard technique.

The ability to know where the eye was directed also made it possible to take another major step: training the monkey on more complex tasks to study cognitive behavior. With my original technique, I rewarded the monkey just for fixating, and I lost the opportunity to train the monkey on most cognitive tasks. Once eye position could be measured, the monkey’s fixation could be controlled by requiring the monkey to keep the eye within a given distance of the target in order for it to proceed to a more complex task for which the reward was now given. The awake monkey could now be used for the variety of tasks, including the complex discriminations and decisions that are now used in laboratories throughout the world.

More complex tasks required better control of the multiple events in the experiments: continuous recording of behavioral responses, eye position, neuronal activity, and modifications to the stimuli presented to the monkey. DigiBits would not suffice. My experience with the LINC computer in the Aplysia experiments had demonstrated to me both its power in controlling experiments and the time required to program it, largely in machine language. I had concluded that LINC rhymed with sink because of what it was for my time. So we made it until the early 1970s without the computer. Mickey and I began trying to tame a PDP12 (half LINC and half PDP 8) to run the monkey experiment in 1972 using a program called MonkRule, and he developed a subsequent program, Monk11, when he returned to monkey work in 1975. Later we used the Real Time Experimental system (REX) that was developed for the PDP11 by Hayes, Optican, and Richmond (1982), but in the field there were almost as many systems as there were awake monkey laboratories. The use of on-line computers has made possible the sophisticated paradigms to study behavior that are used today. The drop in computer prices, from 20K for the basic PDP11 to 2K for a basic PC, has reduced laboratory setup for awake monkey recording from extensive control and analysis hardware to the installation of a set of software programs.

One of the most costly aspects of recording from awake trained monkeys was that going to a new area of the brain usually entailed initial short periods of recording followed by weeks waiting for histology to verify the site of recording. Structural imaging of the brain using magnetic resonance imaging (MRI) has allowed localization to be at least estimated during the first experiment. While precise location still requires careful histology, the MRI has become the GPS for exploring new brain areas.

Two remaining problems in single neuron recording have also been addressed by advances in neuroscience methodology. The first problem is that while we are trying to identify a circuit within the brain of the awake monkey, this is usually not possible because we can only infer what the connections of a particular neuron are. Use of the classical techniques of antidromic and orthodromic activation of the neuron by electrically stimulating potential targets of the neuron’s output or sources of its input can establish these connections before further experiments are done. We have used these techniques between the basal ganglia and the SC (Hikosaka and Wurtz, 1983d), the SC and frontal cortex (Sommer and Wurtz, 2004a), and the SC and visual cortex (Berman and Wurtz, 2010).

The second problem is related to one of the major methods of studying the brain: the analysis of behavioral deficits following brain lesions, which can be used to extend the relation of neurons to behavior beyond just a correlation. A problem with this technique, however, is that the behavior studied is both the result of the lesion and the compensation within the brain for that lesion. But the use of transmitter agonists and antagonists that reversibly inactivate or activate a region of the brain (for example, bicculine and muscimol for GABA receptors) allows analysis of behavior within minutes of activation or inactivation, a time short enough to minimize any compensation. For example, ablation of the SC led us to conclude that the SC made minimal contributions to the guidance of saccades when the saccades were measured the day after the lesion (Wurtz and Goldberg, 1972b), but with SC inactivation with muscimol and saccades measured within minutes, deficits in saccade generation clearly were evident (Hikosaka and Wurtz, 1985). The possibility of activation and inactivation on a trial-by-trial basis (Chow et al., 2010; Han et al., 2009) would make this approach even more powerful. But even with current techniques, the combination of knowing the correlation of a specific set of neurons to behavior, and the ability to then perturb them to test any behavioral change, is one of the reasons the awake monkey technique has become one of the most powerful approaches in systems neuroscience. It is immensely satisfying to see whole sessions at the Society for Neuroscience meeting devoted to experiments on a functioning visual system, what I would refer to as active vision.

The Laboratory of Sensorimotor Research (1978–present)

In 1978 Carl Kupfer, the director of the National Eye Institute at the NIH, raised the possibility of a new laboratory within the NEI that studied the visual and oculomotor system in the best animal model of those systems, the old world monkey. Such a laboratory would collaborate with the neuro-ophthalmology branch of the NEI. The director of that branch was David Cogan, who had retired from Harvard and moved to the NEI, and I know that his interest in a collaborating monkey and clinical laboratory was a key factor in developing our new laboratory. But the lynchpin was Carl’s view of the relation of the NEI to vision research, namely, that the Institute would support research at all levels of the visual pathway, not just the eye as the Institute’s name implied. This attitude provided the substantial and sustained support for study of the brain that led to the explosion of basic knowledge about visual and oculomotor processing in the brain beginning in the 1970s.

It might be worth mentioning the advantages of a laboratory in the NIH intramural research program. The first is the obvious one of freedom from the grant cycle. Early on I became convinced that the intramural program provided support for exploration and the accompanying failures that the grant system did not. This was brought home by serving a full term on a study section; the proposals were incredibly conservative and the criticisms were frequently technical and mundane. I concluded that the best system is the retrospective one of the intramural program: what have you done with the support you have had? This decision is based on fact and enforced by regular reviews. In contrast, the grants system is based on proposals for future discoveries with a nod to reality in the requirement for preliminary data showing that the experiment has already been done. The second is the freedom to structure your own time. Lack of teaching and committee responsibilities allows for concentration on a problem and organizing your own time that for me has been liberating. The third is the ability to bring together a group of scientists interested in the same field of work. This is much more difficult at a university because of the demands of expertise for teaching across many areas.

The timing of the new laboratory was determined by the impending completion of a new wing in the NIH clinical center that would provide the NEI with new space in close proximity to the eye clinic. The Laboratory was formally in place on October 1, 1978, with one member, me, and no space other than what Dr. Tasaki and NIMH could afford to loan me. I chose the name Laboratory of Sensorimotor Research because I thought the name was broad enough to encompass what we would want to do, and the acronym LSR had a nice ring to it. For well into 2 years as the laboratory developed we would struggle with space, until our laboratory area in the new building was completed. Making appointments also proved challenging because NIH salaries were low, and only those already working for the government, or too young to know better, were candidates. I first managed to recruit Mickey Goldberg and David L. Robinson, who had a laboratory on the Navy Medical Center Campus across the street from the NIH. Lance Optican came after a fellowship with Fred Miles in Evarts NIMH Laboratory as a theoretical biologist, and then Fred Miles himself came as well. That completed the initial scientific staff; the expectation of hiring a neuroanatomist and a psychophysicist was never carried out.

There were two basic principles for the laboratory. First, each investigator did what he wanted to do; they had already demonstrated they could pick interesting directions. I have on occasion flattered myself that I had organized a laboratory the way one of my scientific heroes, Steve Kuffler, had done at Harvard: hire the best scientists possible and then let them alone. Second, while each of the investigators had their own laboratory rooms, all of the rest of the supply and equipment funds were pooled and distributed as needed. What sounds like a recipe for conflict turned out to give us all resources we were unlikely to have had as individuals. The give and take that was necessary for the system to work functioned flawlessly, not because it was a good system, but because of the good will and respect the investigators had for each other. In the 24 years I was Chief of the lab, I never experienced an angry encounter, and this among highly competitive scientists who were going to figure out how the brain works.

Once we were in our permanent space, I thought the LSR ran smoothly. What did not run smoothly was the planned interaction with the clinic. We all admired David Cogan, a wonderful person, a scholar of the visual and oculomotor system, an astute clinician, and endlessly helpful. One amusing case of his help was when Barry Richmond and I were doing retrobulbar blocks to paralyze a monkey’s eyes in a critical experiment on the origin of an SC input (Richmond and Wurtz, 1980). In order to eliminate any distress to the monkey we would briefly anesthetize it with gas through a face mask. David laughed when he saw it. He showed us how in patients one just held the eye lid closed, passed the needle through the locally anesthetized lid, and then injected the anesthetic in the back of the orbit. But the more extended interaction between the LSR and the clinic never developed. I think it was in part due to the friction of rubbing together two different ways of dong science: we in the LSR used quantitative measures of eye movements and neuronal responses, and we verified results by repeated experiments; David took videos of a patient’s eye movements and frequently based his striking insights on a single patient. There were a number of joint projects done between clinic and lab, but I feel to this day that I let down David (and Carl Kupfer). This did not dampen David’s personal generosity, and he remained a warm friend and trusted mentor until his death in 1993.

I think the research laboratory is one of the wonders of science. It provides facilities that are adequate to translate ideas into experiments. More important, it provides a community of scientists who not only share technical advances but evaluation of research in the field and criticism of the work of their colleagues. The LSR has for me provided these benefits, particularly the direct criticism of experimental plans or results in lab lunches and seminars. I regarded the criticism as pointed but polite, but most postdoctoral fellows would agree that giving a practice neuroscience talk in the LSR was much more harrowing than at the meeting itself. The 15-minute practice talk routinely generated an hour of suggestions and even disagreement among suggestions. Both the investigators themselves and the spirit of the lab I think contributed to attracting truly outstanding postdoctoral fellows, which of course just further enriched the interaction within the lab. I would be leaving out a key factor in my scientific life, if I did not acknowledge the enormous benefit I have derived from the LSR in particular and the NIH Intramural Research Program in general over 45 years. In that entire period I have never been told what to do, have been adequately supported, and have had a stream of talented fellows and supportive colleagues.

At the outset I never conceived of setting up a laboratory as something I would regard as one of my life’s achievements, but the way it has turned out, and with the scientists it has attracted as staff and as fellows, I certainly do now. I resigned as Laboratory Chief in 2003, with few qualms because of the confidence in my successors, Lance Optican and then Bruce Cumming.

During the organization of the LSR, I was also preoccupied with my two teenage children who were living with me during a period of separation and divorce from my wife Sally. Several years later, however, a happy event came my way when I developed more than a friendship with Emily Thach. After commuting for many months between St Louis and Bethesda, she moved to Bethesda with her daughter Sarah and her twin sons, Will and Jim. We were married shortly later and Emily has been the light of my life for the last 30 years.

Threads of Research at the National Institutes of Health (1972–2010)

My research was guided by a conviction that using the classical distinction between the visual and motor systems was an anachronism simply because a primate’s normal vision did not exist without eye movements. The visualmotor system was what I planned to study, but the field remained divided and the visual researchers regarded me as an oculomotor guy and the oculomotor types regarded me as an interloper from vision. Both were right. My view, however, was liberating and led me to follow a variety of problems on the visual-motor system. The unifying theme is that they all explored the neuronal basis of active vision, that is, the integration of the visual, oculomotor, and cognitive functions underlying visual perception and visually guided behavior. I did not, however, follow one problem to completion and then start another. I rarely felt that I had fully answered the question I set out to study and, at the end of an experimental phase, I frequently either did not know quite what to do next, knew what needed to be done but could not do it, or saw opportunities to ask questions on other problems that I thought were more exciting. The latter case was frequent because the technique of studying neurons in the functioning brain was just opening up and the primate has a very big brain.

Another factor was that, beyond my initial experiments on V1 cortex, I collaborated with postdoctoral fellows. The experimental problemss I addressed were obviously influenced by the interests of these fellows, and this also produced some shifts in direction. I have had only a small number of fellows (between one and five) working with me at any one time. I learned early on that even though my resources increased, my brain stayed the same size. A small group remained optimal. I have been unbelievably fortunate to have had such a series of bright, energetic, hard-working, young scientists come to my laboratory. I have been careful not to dispel the illusion that they are learning from me, when in fact I am getting new ways of doing things and continuing stimulation from them. What I officially do is now called mentoring. What I actually do is design and do experiments with the fellows and we both learn, as Tasaki would say, from Professor Monkey.

In the remaining part of this commentary I would like to recount a few of the experimental lines I have pursued with these wonderful fellows. I am probably already exceeding the patience of even the most enthusiastic reader, so I will concentrate on a few of the more extended threads, which means omitting many experiments. This means that some of my collaborators are nor adequately represented, not because their findings were not significant, but simply because the experiments do not fit into the few threads I have space to recount. I compensate for these omissions only partially by taking this opportunity to list my postdoctoral collaborators:

Michael Goldberg

1969–1972

Charles Duffy

1988–1993

David L Robinson

1971–1975

Douglas Munoz

1989–1992

Charles Mohler

1972–1976

Gregory Recanzone

1991–1994

Joan Baizer

1973–1976

Hiroshi Aizawa

1992–1996

Charlene Jarvis

1974–1975

Satoshi Eifuku

1994–1997

Barry Richmond

1976–1979

Michele Basso

1995–2000

Stuart Judge

1976–1979

Richard Krauzlis

1996–1998

Joanne Albano

1977–1983

Marc Sommer

1996–2005

Okihide Hikosaka

1979–1982

Martin Pare

1996–2000

William Newsome

1980–1984

Douglas Hanes

1997–2000

Akichika Mikami

1982–1984

Nicholas Port

1998–2005

Max Dursteler

1983–1986

Stefano Ferraina

1999–2001

Hidehiko Komatsu

1985–1988

James Cavanaugh

2000–present

David Waitzman

1986–1990

Kerry McAlonan

2001–present

Dwayne Yamasaki

1986–1991

Hiroyuki Nakahara

2002–2004

Jean-Pierre Roy

1987–1989

Rebecca Berman

2005–present

Terrence Ma

1987–1990

Wilsaan Joiner

2007–present

Saccadic Suppression

I had not found evidence for saccadic suppression in V1 neurons; they did not distinguish between nearly identical stimulus motion across a receptive field during fixation and similar stimulus motion produced by saccades. In contrast in the SC, Goldberg and I had found that some of the visual neurons showed a striking suppression of visual responses with saccades. David Lee Robinson and I verified this suppression of the visual response (Robinson and Wurtz, 1976), and we concluded that in the SC there was indeed the suppression I had expected to find in V1 cortex, and this brought some closure to the saccadic suppression search.

By the spring of 1975 I was anxious to take a break after nearly 10 years of recording in awake monkeys. It had been clear to me that I needed more knowledge of human perception and psychophysics to allow me to devise tests that measured perception in monkeys. This in turn would allow me to compare the neuronal activity I could now record in awake monkeys with their behavioral reports using the techniques of psychophysics. The NIH did not routinely offer sabbaticals; we were regarded as being on sabbatical all the time. A senior NIMH scientist, however, had canceled his plans for a sabbatical, and the opportunity was offered in the spring of 1975 to anyone who could start that summer. I had met Fergus Campbell, a psychophysicist at Cambridge University, a year earlier, he was willing for me to join his laboratory, and I arrived there in August 1975.

Cambridge was a major center for both visual physiology and psychophysics. The research roster in addition to Fergus included William Rushton, Horace Barlow, John Robson, Colin Blakemore, John Mollen, Michael Morgan, Oliver Braddick, Roger Carpenter, and David Tolhurst. Many showed up for afternoon tea with invariably interesting discussion and occasional cutting interactions in the finest English academic style. I expected to do psychophysics on Fergus’s specialty, visual spatial frequency, but when we talked about experimental directions, Fergus expressed interest in studying, of all things, saccadic suppression. We did, and over a year we did a variety of pilot experiments, interspersed with an endless stream of Fergus’s amusing anecdotes. After many false starts, we came to the conclusion that the suppression was heavily dependent on the visual masking of the clear visual image before and after the saccade acting on the blur during the saccade (Campbell and Wurtz, 1978). This was consistent with my failure to see active modulation in V1 and with previous work on masking (Matin et al., 1972).

My goal for the year had been to become knowledgeable and competent with psychophysical techniques and analysis. I failed on all counts. Partly this was due to the nature of the exploratory experiments we did and Fergus’s seat-of-the-pants approach, which was fun, but not the methodological experience I needed. More disruptive for my plans was the separation from my wife Sally that began when she moved to London as I stayed in Cambridge with Bill and Erica. Bill prospered during the year, but Erica missed her friends at home.

When I returned to Bethesda, Barry Richmond and Stuart Judge joined me, and we looked to see whether there was any indication of a masking effect in either V1 or SC. We found that there was and that it was strong enough to eliminate all but the strongest visual responses in V1 (Judge et al., 1980b). We also investigated whether the suppression we had seen previously in the SC visual neurons might be the result of some input from outside the visual system. One such input is referred to as a corollary discharge (Sperry, 1950) that is a signal sent from regions of the brain that generate a movement to other brain regions in order to inform those regions that a movement is about to occur. This corollary discharge could produce the suppression in the SC, but suppression could also have resulted from proprioceptive input from the eye muscle contraction. Barry and I addressed this issue by blocking eye movements (using Cogan’s retrobulbar block method) in order to reduce proprioception. The monkey should still be trying to make saccades, which would produce a corollary discharge, and we could see that it was doing so from the bursts of activity we recorded from eye muscle motor neurons. We found that suppression in the SC persisted and concluded that the SC visual suppression must be the result of a corollary discharge (Richmond and Wurtz, 1980), possibly from the saccade neurons in the SC intermediate layers (Lee et al., 2007).

I initially thought that saccadic suppression was a simple phenomenon that would be easy to investigate at a neuronal level. It was not. I think our long series of experiments show that the suppression results from both visual masking and a corollary discharge, and both factors operate at multiple levels along the visual pathways (Wurtz, 2008). This provides an exceptionally clear example of a seemingly simple cognitive phenomenon that is indeed served by simple brain mechanisms, but there are multiple such mechanisms and they act at multiple levels, a distributed modulation.

A Corollary Discharge to Frontal Cortex

The suppression of vision during saccades is an important mechanism for our normal vision, but the major issue is why our perception of the visual world does not appear to jump as the image on the retina does with each saccade. The classical explanation of von Helmholtz (1925) is that an “effort of will” informs the visual system of the impending saccade, the same idea as the corollary discharge of Sperry described earlier or the efference copy of von Holst and Mittelstaedt (1950). While Richmond and I were convinced in 1980 that we had seen the suppressive action of a corollary discharge acting on SC visual neurons, we had seen no evidence of the corollary itself. Identification of a corollary discharge in the primate brain remained largely hypothetical.

This changed after an astute observation by Marc Sommer (1998). Marc, along with Martin Pare and Stefano Ferraina, was testing whether we could identify a single final output signal from frontal and parietal cortex to the SC (Wurtz et al., 2001). We used antidromic stimulation from the colliculus to selectively activate the cortical output neurons with the expectation that we could thereby determine which signals (visual, visual-motor, motor) in frontal and parietal cortex were the final output signals. To my chagrin, all were represented in the output, which meant that we could not determine what the cortical processing had accomplished by looking for a single final output. Marc noticed, however, that in the frontal eye field area of frontal cortex, antidromic response was frequently followed by a later response that could be shown to be an orthodromic response from the SC to frontal eye field (Sommer and Wurtz, 1998). This led to identifying a relay in this pathway in a tiny area of the medial dorsal nucleus of the thalamus. The characteristics of the signals in the pathway and the consequences of its interruption for the control of saccades convinced us that we had at last identified a corollary discharge in the primate brain and one that went to cerebral cortex (Sommer and Wurtz, 2002; 2004a; 2004b).

The next issue was whether this pathway might contribute to our perception of visual stability during saccades by in some way countering the displacement of the image that occurs with each saccade. Without going into details, Goldberg and his collaborators (Duhamel et al., 1992; Umeno and Goldberg, 1997) had shown that there were neurons in parietal and frontal cortex whose receptive fields shifted in anticipation of an upcoming saccade. They suggested that this represented a “remapping” of the visual field with each saccade that might underlie our perception of visual stability. The remapping hypothesis required the input of a corollary discharge for saccades, and the obvious question was whether our corollary discharge was the one required by the shifting RFs. This question could be answered by inactivating the relay and seeing whether the shifts of the frontal eye field RFs were reduced. They were and this heroic experiment indicated that the corollary discharge might provide a necessary input for visual perception as well as for movement (Sommer and Wurtz, 2008; Wurtz, 2008). A key remaining question is whether the shifting RFS are related to stable visual perception, but all the techniques are available to answer that question.

So the corollary discharge, which had eluded me in my initial experiments on V1 cortex many years earlier, was found to project to regions of frontal cortex from layers in the SC via a pathway through thalamus, all of which were not even recognized when I was looking at V1. To me it is a striking illustration of how the success of asking questions about higher level functions depends on what is known about the basic organization of a system within the brain. The right question asked at the wrong place is one of the mistakes I think I have made most frequently. But it is rare that information about a brain system is sufficient to indicate in advance all the functions the system performs and what questions it is sensible to ask. I am quite sure hindsight will show I am continuing the same mistakes now.

Spatial Attention

Mickey Goldberg and I had established an enhanced visual response when the stimulus activating a superficial layer SC neuron became the target for an upcoming saccade. We suggested that this might be a possible correlate of attention. We had no measure of attention, however, and the argument was a logical one: saccades are made to visual targets and a shift of attention precedes saccades. We had found presaccadic activity in one SC layer and the enhanced visual response in the adjacent visual layer, so all the machinery for saccadic activity to act on visual activity was in adjacent layers. It was a controversial idea at the time, but it was also an experimental demonstration of a neuronal process that might underlie a major cognitive process, visual spatial attention. It also generated amusement; at one oculomotor after-dinner entertainment, visual enhancement was represented by a padded bra. Nonetheless, over the next several years we evaluated the enhancement, that is, the neuronal one.

Chuck Mohler and I first investigated how closely related the enhancement was to saccade generation. We found that the enhancement became larger as the saccade onset came closer to the time of target onset. This was consistent with saccade preparation being the source of the visual enhancement and with it reaching the SC superficial visual cells by an ascending projection from the intermediate layer, saccade-related neurons (Wurtz and Mohler, 1976b). We also tested whether the enhancement was more prominent when the monkey responded to the stimulus with a saccade as opposed to a hand movement during continuing fixation, at last studying my first trained monkey, Ethel. The enhancement was reduced with no saccade, and we concluded that the SC enhancement was better regarded as movement preparation rather than attentional shift (Wurtz and Mohler, 1976b). We also found that neurons in the frontal eye field showed stronger enhancement with saccades (Wurtz and Mohler, 1976a), but Bushnell, Goldberg, and Robinson (1981) later found that the enhancement in parietal cortex was present with or without saccades. This led to our generalization that parietal cortex was related to attention but that SC and frontal eye field were more closely related to saccade preparation (Wurtz et al., 1980; 1982).

The flaw in our conclusion was that we assumed that when the monkey did not make a saccade there was no preparatory activity for a saccade because no saccade was made. Subsequent experiments, however, showed that some SC saccade-related neurons we later referred to as buildup neurons began to discharge long before the saccade (Mohler and Wurtz, 1976; Munoz and Wurtz, 1995a) and did so even if the saccade was not actually made. In addition, the subsequently developed motor theory of attention (Rizzolatti, 1983) and the much later experimental support for it from experiments using covert shifts of attention (Moore et al., 2003) renewed the possibility that the neuronal mechanisms underlying visual spatial attention overlapped those for the preparation to make a saccade. This in turn raised the possibility that the now prevalent finding of neuronal modulation with attention in visual cortex could result from an input related to saccade preparation, including that ascending from SC. James Cavanaugh and I therefore tested the effect on attention by activating SC and testing the effect on visual motion processing that is likely to be restricted to cortical processing. We produced a shift of attention by a visual cue and also by low-level SC stimulation that did not evoke a saccade (Cavanaugh and Wurtz, 2004), as did a similar experiment from Bill Newsome’s laboratory (Muller et al., 2005). Later experiments suggested that the shift was not the result of attempting to look at a stimulation-produced visual phosphene (Cavanaugh et al., 2006). The satisfying aspect of these later experiments was that the mechanism of spatial visual attention, at least in some cases, might result simply from input from saccade preparation. The less than satisfying aspect is that we should have done the experiments at least 20 years earlier.

The possibility that ascending activity could produce attentional modulation also suggested that the projection from the SC to the thalamic reticular nucleus might modulate the retinal-cortical pathway via its projection to the lateral geniculate nucleus. Such an action of the thalamic reticular nucleus had been suggested by Francis Crick in his spotlight of attention hypothesis (Crick, 1984). Kerry McAlonan and Cavanaugh showed that both the reticular neurons and the LGN neurons were modulated with attention in ways consistent with the reticular neurons acting on the LGN (McAlonan et al., 2008), but whether this is related to the preparation to make saccades remains unknown.

Finally, we had good reason to believe that the SC was involved in target selection, since ablation had been shown to produce neglect in the contralateral visual field (Albano and Wurtz, 1978). Later experiments with Michele Basso showed that activity in the SC during target selection varied with the conditions of the selection: the amplitude of the buildup activity was increased as the certainty that a stimulus would be the target of the saccade increased (Basso and Wurtz, 1997; 1998).

The results of this series of experiments, widely spaced over time, supports the idea that the SC provides ascending signals that contribute to shifts of spatial attention, and clearly demonstrate that changes in the SC are integrally involved in target selection. This has become abundantly clear from other recent work (Keller et al., 2005; Lovejoy and Krauzlis, 2009). The major point, however, is that seeing the modulation of visual responses first in the SC visual cells and then in many cortical areas, and the possibility that this modulation may be related to the preparation to make a saccade, provides hope that cognitive processes may be understandable on the basis of simple neuronal circuits.

SC and the Basal Ganglia

After identifying types of neurons and layers of organization in the SC in the early 1970s, one of the obvious next steps was to try to use the SC to identify the larger circuits in the brain of which the SC was just one node. There were two ways to go: downward to see how the SC output was converted into the movement signals to produce saccades, or upward to see how the input to the SC influenced its activity. The downward direction was attractive because it would connect the map in the SC to the activity of neurons in the brain stem that decreased or increased their discharge before saccades. This direction also was particularly attractive because Okihide Hikosaka was coming to the lab, and he had completed elegant studies in the cat on one of the key brainstem neurons that the SC might act on, the inhibitory burst neurons. The drawback was that to be most informative the exact connections between the SC and these neurons would need to be worked out, and this seemed to be a daunting task. In contrast, a major input to the SC was from the basal ganglia. This input was unexplored, and if I looked on the study of the awake monkey as a window on cognition at higher levels in the brain, going upward to the basal ganglia made sense. This logic of stepping backward in the saccadic system is analogous to stepping forward in the visual pathway; it is just that we were starting near the end rather than near the beginning of the visual–motor pathway.

Okihide and I concentrated on the input from the basal ganglia to the SC. This arises in the substantia nigra pars reticulata which had recently been shown to have inhibitory input to the SC. Our first observation was that the pars reticulata neurons had high discharge rates and that they usually paused before saccades, just the inverse of what SC neurons did. This was, however, exactly what we would expect if the input to the SC was inhibitory because the pars reticulata pause would release the SC from inhibition just before the burst of the saccade-related neurons in the SC. We concluded that the SC was driven by a push-pull mechanism of excitation from one input (including that from the frontal eye field) and release from inhibition from the other input, the pars reticulata of the basal ganglia. It also became clear that the pause in activity in the pars reticulata varied with the behavioral conditions under which the saccade was made. For example, many pars reticulata neurons did not pause with saccades to plainly visible targets, but paused only with saccades guided by memory to the location of a previously flashed target. This led us to suggest that the basal ganglia might control movement from stored information, or more generally, with movements that could be regarded as voluntary (Hikosaka and Wurtz, 1983a; 1983b; 1983c; 1983d).

We also used two techniques, whose use in awake monkeys was novel at the time, in order to further establish the connection between the pars reticulata and the SC. The first was stimulation in SC to antidromically activate neurons in pars reticulata that project to SC. Here we expanded its use to determine where the axons terminated in the colliculus, and found low current threshold activation among the saccade neurons in the SC intermediate layers. The second technique was the local inactivation of the neurons we had studied in order to see if their absence or hyperactivity produced any behavioral changes (Hikosaka and Wurtz, 1985). We were able to mimic the tonic inhibitory effect of the pars reticulata on the SC by injecting an inhibitory transmitter agonist into the SC (the GABA agonist, muscimol) and reducing the inhibitory input with an antagonist (bicuculline). The inactivation of the SC in the awake monkey and the immediate monitoring of behavioral changes also revealed more dramatic deficits in saccade amplitude and velocity than Goldberg and I had seen on the day after an SC ablation. This suggested that the lack of a more severe deficit in the original experiments was the result of a recovery that had occurred between ablation and behavioral test.

Our work on the relation of the substantia nigra pars reticulata output of the basal ganglia as assayed in the SC was one of the first attempts to study the relation between two successive steps in a visual-motor brain circuit, in this case the circuit for controlling saccades. We were able to do so by using a trilogy of techniques: the relation of the neurons in the two structures to saccades, the connection of the neurons in the two structures by antidromic stimulation, and the effect of activation/inactivation of either structure on saccade generation. While there were obviously substantial limitations to what we could conclude, I think we demonstrated that the techniques needed to begin to dissect these circuits in the brain were now available.

Visual Motion in Awake Monkeys

After my initial forays into V1 cortex, the areas beyond V1 began to be identified (Zeki 1975), and I had the opportunity to investigate one of these areas, MT, when Bill Newsome came to the lab in 1980. Bill had investigated MT with John Allman and then David van Essen in the anesthetized monkey, and with Aki Mikami and Max Dursteller we explored MT in the awake monkey for the first time. We verified the expected directional selectivity for motion (Mikami et al. 1986a), and then went on to test the relation of MT neurons to apparent motion, the motion produced by successive flashes (the phi motion of the movies). We found that MT directionally selective neurons had the appropriate spatial and temporal properties to underlie one type of apparent motion seen in humans, the short range process (Braddick 1974), which was not the case for V1 neurons (Mikami et al. 1986b; Newsome et al. 1986).

Thus we had established that MT neurons could underlie the perception of apparent motion in ways that V1 could not. What we had not done was take the next step of showing that ablation within MT altered the monkey’s perception of apparent motion. This soon became possible because in our next experiments we developed a method for selectively ablating small regions of MT.

At the time of these experiments, the early 1980s, one of the major questions about cortical visual processing was whether different types of processing such as color, form, and motion, were represented differentially in separate extra-striate areas. Therefore, if motion were represented primarily in MT, and we ablated MT, we would expect to see a deficit in a behavior that depended on motion. We used a task that required the monkey to make a saccade to and then pursue a moving target because we could quantitatively measure the pursuit movement of the eye that precedes the saccade to the target. We made ibotenic acid lesions in MT affecting just one region of its retinotopic map of the visual field. We found a deficit in the use of the target moving in the visual field represented by the ablated MT (Newsome et al. 1985). The deficit was specific for the use of motion and not position, and I think this was one of the first behavioral demonstrations of dedicated processing in a specific extrastriate area (Newsome and Wurtz 1988). This was of course a demonstration related to eye movements, and Bill went on in collaboration with Tony Movshon to show the relation of MT to the perception of visual motion. My failure to move promptly to perceptual deficits following inactivation of MT was a carry over of my failure to integrate psychchophysical techniques and thinking into my plans after my time at Cambridge.

Subsequent experiments explored the extent of the contributions of both MT and the next visual motion area, MST, to the control of pursuit eye movements. We first found that the ibotenic acid lesion of MST produced a deficit in the maintenance of pursuit for targets moving toward the side of the lesion (Dürsteler et al. 1987). This was exactly the deficit seen in humans with cortical lesions, and we suggested that we had located the level of visual processing that leads to that deficit. Work with Hidehiko Komasu also showed that MST was probably a group of areas. One, a lateral-anterior area (MSTl) that represented regions close to the fovea, was related to pursuit maintenance and, when electrically stimulated, altered pursuit, Another, a dorsal-medial area (MSTd) was more responsive to full field visual stimulation (Komatsu and Wurtz 1988a; Komatsu and Wurtz 1988b).

When Charlie Duffy came to the lab we investigated whether the large fields of MSTd might be the area that responded to large field optic flow patterns, the patterns that are generated as we walk through our environment, and that Gibson (1954) had emphasized as critical for perception and movement. The neuronal responses in the area indicated that MSTd was such an area (Duffy and Wurtz 1991a; 1991b), as predicted by previous experiments using looming stimuli (Tanaka et al. 1986). Further experiments showed the types of flow stimuli that activated these neurons, and that the response of some neurons to the direction of stimulus motion depended upon the depth of that motion in the visual field as determined by their binocular disparity (Roy and Wurtz 1990).

When I was first recording from V1, I met James Gibson at Cornell and he urged me to use more than just spot and slit stimuli. But I could not see how the small V1 RFs could possibly respond to the large field optic flow Gibson was interested in. These studies in MSTd many years later revealed at last the types of neuronal responses Gibson had told me must be there, and so it was gratifying to find them even though it was too late to show them to him.

Our experiments in MT and MST were among the first to show the relation of the areas to perception (apparent motion), to the control of movement (smooth pursuit), the response to optic flow, and the response to disparity stimuli. These are lines that I have not followed beyond these initial experiments, but my collaborators obviously have done so with much sharper questions, better methods, and immense success.

The Function of Superior Colliculus Neuronal Elements

Most of my experiments have used the SC as the starting point for exploring the cerebral cortex by looking at the inputs from frontal and parietal cortex to SC (Wurtz et al., 2001), and the ascending pathways that modulate cortex via the thalamic medial dorsal or pulvinar nuclei (Berman and Wurtz, 2010; Sommer and Wurtz, 2008). What further exploration of the SC I did, after it burst on the scene in the early 1970s, was embedded in a much larger effort by a number of laboratories, particularly that of David Sparks.

Most of everyone’s effort was devoted to the saccade-related neurons in the intermediate SC layers. A significant advance in sorting out the types of saccade related-neurons followed the arrival of Doug Munoz who had studied the SC in cats with Dan Guitton (Munoz and Guitton, 1991; Munoz et al., 1991). In the monkey, the neurons with a burst of activity just before the saccade had been the center of interest. Other largely unstudied neurons, however, began to increase their activity hundreds of milliseconds before the saccade and frequently had little burst activity. We referred to these descriptively as buildup neurons (Munoz and Wurtz, 1995a) and, as I have already mentioned, I think the early activity of these neurons make them prime candidates for producing the modulations of activity in other layers of the SC and in other areas of the brain related to saccades.

Another finding derived from the cat investigations was the identification of “fixation neurons” in the rostral SC that represents the central visual field. Instead of becoming active before saccades, they became active when the monkey fixated (Munoz and Wurtz, 1993a). Because of their characteristics we considered them to be rostral extensions of the buildup neurons, but because when we inactivated them the monkey made irrepressible saccades and when we activated them there was prolonged fixation (Munoz and Wurtz, 1993b), we referred to the area as a fixation zone. Subsequent work of Rich Krauzlis and Michele Basso (Krauzlis et al., 2000; 1997) showed that these neurons might provide a position error that could be used either for saccades or smooth pursuit. Later work from Krauzlis’s lab showed that the rostral SC neurons were active before microsaccades in ways similar to the ways in which the rest of the SC became active before larger saccades (Hafed et al., 2009). This and other findings led to the view that these rostral neurons were the same as more caudal buildup neurons; they all inhibited activity in other SC areas when they were active. Activating or inactivating these rostral SC neurons did modify fixation and this must occur when the rostral neurons are active, but they are not a separate type of SC neuron, just a rostral extension of the buildup neurons as we recognized from the outset. Our use of the terms fixation neurons and fixation zone, with the benefit of hindsight, was less than optimal.

Another hypothesis based on the SC of the cat was that the duration of activity and thus the amplitude of a saccade was the result of a wave of activity that moved across the SC. In Doug Munoz’s recording from the monkey we saw not a wave but a spread or expansion of activity during a saccade (Munoz and Wurtz, 1995b). The sequence could be seen even more clearly by recordings at two SC sites (Port et al., 2000). I thought this was potentially a beautiful illustration of how activity across a map of movement could control the metrics of a movement. The characteristics of the spread, its timing, and other factors, however, made the proposal controversial, to say the least. The experimental result that convinced me that the activity did not control the amplitude of the saccade was that, when the spread was disrupted and presumably slowed by muscimol inactivation of the SC midway along the retinotopic map, the saccades did not become longer as predicted by a slower spread, but stayed the same or became shorter (Aizawa and Wurtz, 1998; Quaia et al., 1998). This left the observation of the spread a valid one in my view, but without a function. Hiro Nakahara had the idea that the spread was the inevitable result of the distortion of SC movement fields that results from the constriction of the magnification factor with eccentricity, and a simulation of a model produced results similar to our SC observations (Nakahara et al., 2006). I now think of the spread as a classic biological epiphenomena in that it directly results from the organization of a biological structure but does not indicate the function of the organization.

The SC would be one of the best understood regions of cerebral cortex, that is, if it were in cerebral cortex. With a layered structure, a retinotopic map, a limited number of neuron types, and the ability to quantitatively measure the eye movement behavior it controls, the SC has evolved into an ideal structure for modeling the transition from sensory input to movement output (Quaia et al., 1999; Wurtz and Optican, 1994), including its role in attention and target selection (Krauzlis et al., 2004). The SC also serves as the best window onto the transition from cerebral cortical processing for behavior to the brainstem execution of that behavior. More recently, the SC has begun to provide the first insights into what information the brainstem feeds back to the cerebral cortex.

Conclusion

In writing this I have had the disconcerting realization that I have been studying brain and behavior for over half a century, starting in 1958 in the laboratory of Jim Olds. The changes in studying systems in the brain over that time are staggering. Then, the relation of brain activity to behavior was studied primarily using the electroencephalogram (EEG). The EEG was a filtered electrical signal averaged over many thousands of neurons. Occasionally animals were trained, but only in simple conditioning tasks. Now in contrast, activity of individual neurons can be correlated with highly sophisticated behavioral tests.

Put another way, the questions have not radically changed, but the experimental power to answer them has. Fifty years ago, if we had questions about simple behaviors such as the generation of movement or about cognitive processes, such as attention and perception, we could not go into the brain and explore the neuronal activity contributing to these functions. Now we can record from single neurons in identified brain structures and measure how well their activity correlates to even cognitive behavior. We can then go beyond this correlation of neurons and behavior by selectively activating or inactivating local groups of neurons, and measuring how the behavior changes. Finally, by determining what neurons in one brain area are functionally connected to those in another area, we can at least begin to outline the circuits in the brain producing behavior. We can begin to see the neuronal mechanisms underlying behavior, not just the correlations.

If we judge success by how far our understanding of the brain has come compared to where we were 50 years ago, we have had stunning success, far beyond anything I could have imagined. But if we judge by how far we have to go, the challenge is immense and sobering. The challenge may be matched, however, by the emerging new techniques for studying hundreds of neurons at a time, knowing their types and connections, and manipulating their activity millisecond by millisecond. While the last 50 years have been exciting times for studying the brain, and it is an incredible gift to have participated in it, I envy those starting to study the brain now.

I am obviously expressing my view through my tiny window onto just one segment of neuroscience, systems neuroscience, and even then onto just the system I have studied. A universally recognized change, however, is that there is now a field called neuroscience. Particularly since the founding of the Society for Neuroscience in 1969, the multiple approaches to the study of the nervous system are recognized as parts of a common goal of understanding the brain and the behavior it produces. Students now need not apologize for studies in what used to be disparate areas but are now encompassed by neuroscience. News reports refer to neuroscience research as readily as they do to space research. I have been fortunate to have spanned this rise of neuroscience, seen its stunning advances, and contributed a bit to its development.

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Index

Abdullaev, Y. G., 578

Ache, B., 663

Adams, D. J., 168

Adams, B., 237

Adams, S., 597

Adrian, R. H., 157, 298, 499, 511, 661, 662

Aghajanian, G. K., 18, 19, 20

Agmon, A., 263, 264

Agnew, W. S., 155

Agopyan, N., 320

Aitkin, L. M., 445

Aizawa, H., 735, 745

Akbarian, S., 269

Akil, H., 269, 680

Albano, J. E., 735, 740

Alexander, G. E., 80, 83, 84

Almers, W., 164, 178

Alonso, M., 209, 216

Andersen, P., 392, 394–96, 673

Anderson, N. C., 511

Anderson, W. W., 148

Andersson, S. A., 395

Andreose, J. S., 425

Angelakos, E. T., 649

Anisman, H., 201

Ardenghi, P., 211

Ardestani, A., 90

Armstrong, C., 512

Armstrong, C. M., 153, 166, 168, 169, 171, 512

Asanuma, C., 260

Ashford, J. W., 85

Aston-Jones, G., 37

Aungle, P. G., 287

Axelrod, J., 16, 17, 20, 21, 26, 34, 544, 681

Babcock, D. F., 179

Baddeley, A., 80, 81, 84

Baird, A. A., 130

Baker, P. F., 157

Balaban, E., 364, 367, 368

Ball, R., 177

Barnes, S., 169, 171

Barrnett, R. J., 16, 17

Barros, D. A., 207, 209

Basso, M. A., 735, 740, 745

Batini, C., 369

Battenberg, E. L. F., 34

Bauer, R. H., 80

Baynes, K. B., 127, 130

Bayon, A., 36

Bekinschtein, P., 211, 215, 216, 217, 218

Belo, M., 370, 371

Benabid, A. L., 38

Ben-Ari, Y., 311, 316, 320

Bender, D. B., 728

Benson, D. L., 262

Benson, T. E., 664, 685

Berkowicz, D. A., 672, 685

Berlucchi, G., 104, 106

Berman, A. L., 260

Berman, N., 620, 633

Berman, R. A., 731, 735, 744

Bernabeu, R., 207, 208, 209

Bernstein, T., 510

Bevilaqua, L. R., 207, 209, 210, 211, 214, 215

Bezakova, G., 427

Bezanilla, F., 166

Bianchin, M., 207, 208

Billiard, J., 178

Billingham, R. E., 371

Bishop, P. O., 614, 619

Bizzi, E., 617, 618, 626, 718, 719, 722

Bjorklund, A., 544

Blakemore, C., 625, 626

Blass, E. M., 663

Blaustein, M. P., 157, 506

Bliss, T. V., 200, 205, 206, 208, 212, 383, 398–402, 404–6, 414, 429–31, 432

Bloom, F. E., 1–49

Boch, R., 622

Bogen, J. E., 102

Boies, S. W., 581

Bonini, J. S., 207, 208, 210, 211, 213

Borges, J. L., 190–91, 196, 218

Braddick, O., 736, 742

Brayton, R. K., 647, 666, 667

Breer, H., 672

Brenner, H. R., 415, 425

Brentani, R. R., 210

Bressler, S. L., 89

Brightman, M. W., 654

Brill, M. H., 65, 73, 518

Brioni, J. D., 200, 203

Brito, J. M., 360

Broide, R. S., 48

Brooks, D. J., 549

Brown, D. A., 175

Brown, D. D., 254, 650

Brugge, J. F., 445

Bucy, P. C., 77

Bunney, W. E., Jr., 269

Burns, J. M., 109

Burns, B. D., 301, 302, 398, 404

Burton, H., 259

Bushnell, M. C., 739

Cahalan, M. D., 167, 170

Cahill, L., 203

Cajal, S. R., 60, 65, 69, 70, 190, 248, 257, 258, 266–67, 402, 542, 651, 652, 658, 681

Caldwell, P. C., 160

Calloni, G. W., 362

Cameron-Curry, P., 362

Cammarota, M., 207, 209, 210, 211, 214, 215

Campbell, D. T., 166

Campbell, F. W., 302, 736

Cangiano, A., 415, 416, 417, 418

Cao, A., 632, 633

Carnevale, N. T., 522, 667

Carrasco, M. A., 202

Carvey, C. E., 610, 633, 636

Catterall, W. A., 164, 165

Cavalheiro, E. A., 200, 201

Cavanaugh, J., 735, 740

Cepko, C. L., 364

Chandler, W. K., 157, 166, 499, 500, 522, 656

Chang, H. C., 319, 673

Chang, H. T., 319

Charles, E. R., 623, 631, 634

Charpak, S., 684

Charrier, J. B., 366, 367

Chaumont, F., 345

Chaves, M. L. F., 203, 207

Chavkin, C., 39

Chen, W. R., 673, 674, 676, 685

Cherubini, E., 316

Chorover, S. L., 613, 614, 615

Choudary, P. V., 268

Chow, B. Y., 731

Chu, F. C., 730

Chu, N-s., 26

Chun, L. L. Y., 354

Clark, S. A., 7

Cohen, I., 424

Cohen, J., 37

Cohen, L. B., 160, 656, 674

Coitinho, A. S., 210

Colby, C. L., 620, 623, 634

Cole, K. S., 153, 163, 165, 489, 490, 494, 499, 510

Collingridge, G. L., 205, 206, 212

Conti, F., 167, 168

Conway, J. L., 634

Cooley, J. W., 500, 522

Coombs, J. S., 500, 501

Corballis, P. M., 130

Corbel, C., 370

Costa, E., 14–15, 16, 22, 30

Couly, G. F., 350, 351, 357, 358, 359, 360, 365

Crasto, C. J., 679, 685

Creutzfeldt, O. D., 73, 74, 75, 620

Creuzet, S., 350, 351, 356, 360

Crick, F., 125, 145, 301, 614, 653, 740

Croisille, Y. L., 342

Crossley, P. H., 365

Cruzblanca, H., 176

Dainty, J., 287

Dale, A. M., 295

Dalkara, T., 320, 321

Darrow, B., 670, 686

Davidson, R. M., 728

Davison, A. P., 685

DeFelipe, J., 262, 266

Desimone, R., 626, 631

Deyo, S. N., 35

Diamond, I. T., 250, 253, 537, 620

Dias, R. D., 202, 203

Docter, R. F., 72

Dodge, F. A., 149

Dodge, F. A. Jr., 150–51, 152, 498, 500, 515, 519, 522

Dolan, R. P., 628, 629, 634

Doron, K. W., 130

Dowling, J. E., 627, 628, 657

Dreifuss, J. J., 305

Duffy, C. J., 735, 743

Duhamel, J.-R., 738

Dulac, C., 362

Dunlap, K., 176

Dupin, E., 361, 362, 363

Durham, L., 242, 511, 604, 606

Dürsteler, M. R., 735, 743

Dwyer, T. M., 168

Eccles, J. C., 14, 25, 195, 237, 292–94, 296, 311, 319, 391, 394, 396, 397, 398, 401, 404, 409, 413, 500, 501, 652–54, 657–58

Edelman, G. M., 89, 367

Eichelman, W., 569

Eken, T., 421

Elder, G. C., 42

Eliassen, J. C., 130

Enroth-Cugell, C., 619, 621

Erdemli, G., 321

Erulkar, S. D., 657, 660

Etchevers, H. C., 351

Ettenberg, A., 35

Evangelista, A. M., 198

Evarts, E. V., 33, 596, 617, 662, 719, 720, 722, 724, 726, 729, 732

Falkenburger, B. H., 176, 177

Fan, J., 579

Fehilly, C. B., 370

Felleman, D. J., 450

Fendrich, R., 114, 117, 130

Ferraina, S., 735, 738

Ferrera, V. P., 624

Fin, C., 208

Firestein, S. F., 669, 670, 672, 685

Fischbach, G. D., 176, 720

Fischer, B., 622

Fischer, E. H., 164, 291

Fishman, H. M., 510

Floriano, W. B., 672

Fontaine, J., 346, 352, 355

Foote, S. L., 27, 34, 35, 39

Fossella, J. A., 579

Foxman, B. T., 130

Frankel, W. N., 300, 544

Frankenhaeuser, B., 149, 151, 157, 162, 165

Freedman, S., 315

French, E. D., 34

Frenkel, M., 544

Friedman, D. P., 261

Friess, S. L., 493

Fuchs, A. F., 721, 729

Fuhrman, F. A., 507

Fulginiti, S., 198

Fumagalli, G., 425

Funahashi, S., 84

Funnell, M. G., 130

Furini, C. R., 208

Furshpan, E. J., 147, 354

Fuster, J., 59–93

Gage, P. W., 512, 516

Galindo, A., 305

Games, D., 34, 47

Gans, C., 357

Garcia, D. E., 176

Gardner, D., 680

Gattoni, R. C., 199

Gazzaniga, M. S., 89, 99–130, 268, 575, 681

Getchell, T. V., 657, 658, 668, 685

Giarman, N. J., 19

Gibson, J. J., 744

Glickstein, M., 104

Goddard, W. A., 672

Godfraind, J.-M., 307, 318

Goldberg, J. M., 541, 542

Goldberg, M. E., 598, 619, 725, 726, 727, 728, 729, 731, 732, 735, 736, 738, 739, 742

Goldman, D. E., 494, 502, 506

Goldman-Rakic, P. S., 84, 665

Goldstein, M., 649

Goldstein, A., 29

Golshani, P., 263

Goronowitsch, N., 355

Gozzani, J. L., 200

Graham, A., 362

Grapin-Botton, A., 365

Graziano, A., 266, 268

Greatbatch, W., 491, 492, 509, 525

Greenfield, A., 614, 634

Greengard, P., 22

Greenwood, P., 130

Greer, C. A., 664–65, 667, 671, 675, 685

Grethe, J. S., 650, 651, 653, 655, 672, 683, 684

Grillner, S., 683

Grosmaitre, X., 671, 685

Gruart, A., 211

Guillemin, R., 29, 31, 33

Guitton, D., 744

Guy, N., 369

Haberly, L. B., 657, 659, 685

Haenny, P. E., 631, 632, 634

Hafed, Z. M., 745

Halasz, N., 686

Hallonet, M. E., 364

Hamill, O. P., 173

Hammond, W. S., 353, 356

Handy, T. C., 130

Hansen, A. J., 686

Harris, E. M., 496, 497, 504, 513

Hartline, H. K., 149, 152, 626

Harvey, J. A., 542, 543

Hashikawa, T., 267

Hayashi, J. H., 298, 304, 521

Hayek, F. A., 89

Heath, C. J., 255, 256, 258

Hebb, C. O., 295, 297

Hebb, D. O., 89, 295, 402–4, 456, 711, 712, 713

Hedlund, B., 669, 670, 685

Heller, A., 542, 543, 544

Helm, J. P., 4

Hendry, S. H. C., 261, 262, 263

Hennig, R., 421, 422

Henriksen, S. J., 28, 34, 38, 39

Henry, J. L., 310

Herlitze, S., 176

Herrington, J., 178, 179

Herz, A., 75

Hettleman, K. R., 605, 608

Hikosaka, O., 622, 731, 735, 741, 742

Hilgemann, D. W., 177

Hille, B., 141–183

Hillyard, S. A., 122

Hines, M. L., 519, 520, 521, 522, 523, 673, 679

Hirai, T., 261, 263

Hirdes, W., 176

Hirst, W., 122

His, W., 351

Hochachka, P. L., 318

Hodgkin, A. L., 7, 146, 153, 155, 157, 158, 159–60, 161, 163, 165, 166, 167, 168, 287, 309, 488, 494, 497, 499, 500, 508, 510, 652, 656, 720

Hoffer, B. J., 24

Hokfelt, T., 26, 544

Holt, E. B., 725

Holtzman, J. D., 116, 130

Honda, C. N., 263

Hondeghem, L. M., 170

Horowitz, L. F., 176

Hörstadius, S., 351, 355

Houssaint, E., 348, 349

Hubel, D. H., 71, 83, 244, 388, 389, 442, 457, 568, 594, 612, 614, 617, 619, 620, 625, 627, 632, 662, 715, 716, 717, 720, 721, 722, 723–725

Hunt, H. F., 542

Huntley, G. W., 263

Huntsman, M. M., 263

Hutsler, J. J., 130

Huxley, A. F., 7, 70, 146, 153, 155, 158, 159, 161, 163, 166, 170, 286, 287, 309, 488, 497, 499, 500, 502, 652, 720

Hyder, F., 675

Iversen, L. L., 20, 26, 28, 33, 35, 38

Iversen, S. D., 20, 33, 38

Izquierdo, I., 189–219

Jacobsen, C. F., 79, 80, 83

James, W., 212

Jansen, J. K., 406

Jasper, H., 71, 251, 260, 297, 302, 388

Jastreboff, P. J., 644, 664, 686

Jeffery, W. R., 357

Jenkins, W. M., 462, 463

Jensen, J. B., 176, 177

Jensen, R. V., 193

Jerusalinsky, D., 207, 208

Jervey, J. P., 85, 86

Jia, C. P., 674, 685

Jirikowski, G. F., 40

Johnston, M. C., 356

Jones, E., 233–270

Joshi, D., 686

Jouandet, M. L., 130

Joyner, R. W., 513, 514, 515, 518

Judge, S. J., 729, 730, 735, 737

Julian, F. J., 70, 494, 502, 506

Julien, J. P., 322

Jung, J., 343

Jung, S. R., 180

Kaas, J. H., 449, 450

Kaftan, E. J., 179

Kalhovde, J. M., 420

Kandel, E. R., 195, 209, 401, 496, 667, 683, 720

Kanwisher, N. G., 146, 626

Kao, C. Y., 507

Karapas, F., 544

Karten, H. J., 269

Katche, C., 217, 218

Kato, K., 304

Katz, B., 26, 151, 291–92, 301, 402, 412–13, 493, 498, 500, 507, 652, 656, 661

Katzung, B. G., 170

Kauer, J. S., 657, 662, 664, 665, 668, 674

Kawamura, H., 307

Keele, S. W., 568, 571

Keller, E. L., 740

Kelly, J. S., 305

Keynes, R. D., 160, 161, 168

Kilpatrick, R., 287

Kingstone, A., 130

Kinutani, M., 369, 370

Kirby, M. L., 359

Kitzes, L., 445

Klüver, H., 77

Knapp, A. G., 628, 630, 633

Koch, K. W., 87

Koda, L. Y., 34, 35

Koerner, F., 619, 633

Koh, D. S., 176, 179

Komatsu, H., 735, 743

Koob, G. F., 33, 34, 39, 42

Koppenhöfer, E., 169

Kosslyn, S. M., 123, 569, 681

Krauzlis, R. J., 735, 740, 745, 746

Krieger, N. R., 193

Križ, J. M., 322

Krnjevi , K., 279–323

Kupfer, D. J., 20

Lahav, R., 363

Lai, C., 40

Lamour, Y., 309, 320

Lancet, D., 664, 669, 685

Landis, D. M. D., 664

Landis, S. C., 26, 28, 354

Lashley, K. S., 102, 456, 576, 595, 596, 597

Laska, M., 678, 686

Laughlin, S. B., 118

Le Douarin, N. M., 335–373

Le Lièvre, C. S., 346, 350, 351, 352, 355, 356, 357

Leblond, J., 317, 321

Lecoin, L., 363

LeDoux, J. E., 77, 108, 118, 130

Lee, K., 631

Lee, K. M., 737

Leggio, M. G., 267

Leinders-Zufall, T., 670, 671, 685

Lerner, R. A., 38

Levi de Stein, M., 207

Liang, F., 263

Lima, R. H., 39, 210

Linden, L., 210

Lindgren, C. A., 521

Ling, N., 33

Lisiewicz, A., 309

Liu, X. B., 263

Liu, N., 680, 685

Lledo, P.-M., 684

Llinás, R. R., 266

Loeb, G., 452

Logothetis, D. E., 175

Logothetis, N. K., 623, 631–32, 633, 634

Lømo, T., 383–432

Loughlin, S. E., 35

Lovejoy, L. P., 740

Luck, S. J., 116

Lutz, T., 345

Lux, H. D., 75

Lynch, G., 125, 401, 402

Macchi, G., 261

MacDonald, J. F., 309

Maciejewski-Lenoir, D., 40

Mackie, K., 176

MacKinnon, R., 166

Malpeli, J., 620, 623, 624, 634

Mancini, R. E., 192

Manger, P. R., 265

Mangun, G. R., 130

Mao, B., 685

Marchetti, C., 176

Marenco, L. N., 685

Marichich, E. S., 197

Martin, C., 370

Martin, J. M., 463, 678

Martinez, S., 365

Martins, V. R., 210

Martone, M. E., 680

Masukawa, L. M., 669, 685

Masurkar, A. V., 685

Mathiesen, I., 425, 426

Matin, E., 736

Maunsell, J. H. R., 87, 622–24, 628, 631, 632, 634

May, P. R., 81–82

Mazzarello, P., 684

McAlonan, K., 735, 740

McCandliss, B. D., 578

McClintock, T. S., 675

McCormick, D. L., 266

McGaugh, J. H., 35, 203

McGaugh, J. L., 197, 200, 202, 203, 204, 206, 215, 216, 217, 567

McGinty, J. F., 39

McGonnell, I. M., 362

McNaughton, L. A., 402, 404

McPeek, R. M., 634

Medawar, P., 653

Medina, J. H., 203, 204, 205, 206, 207, 208, 209, 211, 212, 215, 217, 219

Mehlen, P., 367

Merlo, A. B., 196

Meryman, H. T., 492

Merzenich, M. M., 439–468

Mesulam, M.-M., 89

Metcalfe, J., 128

Meves, H., 157, 162, 166

Migliore, M., 676, 686

Mikami, A., 735, 742

Miledi, R., 293, 294, 301, 400, 408, 412–13, 507

Mirsky, J. S., 679, 685

Mishkin, M., 722

Mitchell, J. F., 296

Mitchell, R. F., 567

Mittelstaedt, H., 737

Mohler, C. W., 735, 739

Molinari, M., 267

Mombaerts, P., 661, 671

Mommaerts, W., 156

Moore, J. W., 477–525

Moore, R. Y., 35, 531–551

Morales, M., 40, 493

Moran, J., 631

Morris, M. E., 305, 311, 313

Morrison, J. H., 36, 39, 47

Morse, T. M., 680, 685

Mountcastle, V. B., 244, 250, 253, 442–44, 446, 455, 575, 625, 650, 652–53, 716

Mozell, M. M., 665

Mozhayeva, G. N., 171, 182

Mueller, D., 215

Muller, J. R., 740

Munoz, D. P., 735, 739, 744, 745

Murray, K. D., 268

Myskiw, J. C., 211

Nakahara, H., 735, 745

Nakamura, R. K., 108, 364, 669

Naquet, R., 201, 368, 369

Narahashi, T., 153, 505, 506, 507, 516, 522

Nasello, A. G., 197, 198

Nass, R. D., 114

Nataf, V., 363

Nathanson, N. M., 165, 174

Naumov, A. P., 171, 178, 179, 182

Nave, K-A., 40

Nawroth, J. C., 685

Nelson, R. J., 450

Netto, C. A., 203, 207

Neumcke, B., 167

Neville, H. J., 36

Newsome, W. T., 735, 740, 742, 743

Nguyen, T. T., 179

Nicholson, J. L., 42

Nicoll, R. A., 23, 176, 401, 660

Nistri, A., 309

Njå, A., 430

Noda, M., 174

Noma, A., 174, 318

Nonner, W., 151, 152, 162, 167

Northcutt, R. G., 357

Nowycky, M. C., 660, 685

Nudo, R. J., 456

Numa, S., 37

Ohkubo, Y., 360

Ojima, H., 267

Olson, L., 259

Optican, L. M., 730, 732, 734, 746

Orsingher, O. A., 197, 198

Östman, R., 193

Ottoson, D., 655, 656, 668

Paratcha, G., 208, 210

Pare, M., 735, 738

Park, Y. B., 179

Parker, C. W., 25

Patterson, P. H., 354

Paul, R. L., 445–46, 447

Pavlov, I. P., 214

Pearse, A. E. G., 355

Petersen, S. E., 122

Peterson, B. E., 462, 685

Pettigrew, J. D., 724

Phelps, E. A., 128

Phillips, C. C., 650, 651, 652, 653, 654, 673

Phillis, J. W., 296, 299, 300

Pickel, V. M., 26

Platt, J. B., 355

Plum, F., 114

Pongracz, F., 685

Pons, T. P., 265

Port, N. L., 745

Porter, R., 261

Posley, K. A., 87

Posner, J. B., 114, 564, 569

Posner, M. I., 122, 563–81, 681

Pourquié, O., 357

Prado de Carvalho, L., 200

Prado, V. F., 211

Premack, D., 107

Puil, E., 309

Pumain, R., 307, 320

Purpura, D. P., 25

Putnam, M. C., 130

Quaia, C., 745, 746

Quevedo, J., 207, 209

Quillfeldt, J. A., 207

Quintana, J., 84, 87

Quirk, G. J., 215

Rachid, C., 200

Raichle, M. E., 122, 563, 576, 577, 580

Rakic, P., 665

Rall, W., 395, 643, 653, 667, 682, 683

Ralston, E., 657

Ramon, F., 514, 515

Randi , M., 300

Rausell, E., 264, 265

Rayport, M., 119

Real, C., 363

Recanzone, G. H., 459, 735

Redwine, J. M., 48

Reese, T. S., 654

Reiffenstein, R. J., 307, 313

Reilly, J. F., 48

Reinhardt, W., 311

Renaud, L., 307

Rescorla, R. A., 200

Restrepo, D., 675

Reuter, H., 157

Reuter-Lorenz, P. A., 130

Ricci, G. F., 388

Richmond, B. J., 144, 730, 733, 735, 737

Richter, R. B., 538, 539, 540, 633, 685

Riley, J. N., 4, 5

Rimer, M., 424, 426

Rinzel, J., 666, 683

Risse, G. L., 114, 130

Rizzolatti, G., 107, 728, 740

Robson, J. G., 303, 619, 621, 736

Roche, J. P., 176

Rogers, M., 569

Rogers, J., 36

Ropert, N., 312, 320

Rosenkilde, C. E., 84

Rosenthal, J., 408, 410, 414

Roser, M. E., 130

Rossato, J. I., 207, 209, 210, 211, 215, 216, 217, 218

Roth, R. H., 19

Roth, L. J., 542

Rothbart, M. K., 578, 580

Rothman, D. L., 675

Roy, J. P., 735, 744

Rubinstein, J. L. R., 43

Rueda, M. R., 580

Sakmann, B., 408, 415, 522

Salaün, J., 372

Salmoiraghi, G. C., 12, 16, 22, 23, 24, 29

Sanna, P. P., 40

Saxen, L., 348

Schatzmann, H. J., 157

Schein, S. J., 620, 623, 633

Scheuer, T., 164

Schiller, P. H., 585–636, 729

Schindler, R. A., 452

Schmitt, F. O., 18, 33, 34, 35, 46, 367

Schreyer, D. J., 260

Schulman, J. A., 539

Schultze, M., 607

Schutz, R. A., 200

Schwark, H. D., 263

Schwartz, F., 601

Schwartz, S., 304, 305

Scott, W. R., 506

Segal, D. S., 33

Segal, M., 26

Segev, I., 667, 683

Seitz, N., 157

Shallice, T., 212

Shapiro, B. I., 170, 511

Shapiro, M. S., 176, 177

Sharp, F. R., 662

Shaw, T. I., 158, 507

Shen, G. Y., 673, 674, 676

Shepherd, G. M., 643–686

Shepherd-Barr, K., 682

Sherk, H., 626, 634

Shindy, W. W., 87, 88

Shoemaker, W. J., 33, 34, 35

Sidtis, J. J., 127, 130

Sierra, G., 76, 77, 80, 194

Sierra-Marcuño, G., 76

Siggins, G. R., 24–26, 28, 34, 39

Sigworth, F. J., 151

Simpson, J. I., 630

Singer, M. S., 125, 672, 685, 686

Skorpen, J., 423

Slater, C. R., 423, 432

Slaughter, M. M., 628

Slipczuk, L., 209, 211

Slocum, W. M., 633, 634

Smirnakis, S. M., 634

Smylie, C. S., 127

Snyder, S. H., 29

Soejima, M., 174

Solomon, R. L., 200

Sommer, M. A., 634, 731, 735, 738, 744

Sommer, T., 579

Sonenberg, N., 323

Sperry, R. W., 101, 102, 103, 104, 105, 129, 620

Squire, L. R., 91, 206, 213, 217, 373, 478, 574, 618, 633, 634, 681, 706

Steriade, M., 266, 312, 313

Sterling, P., 727

Sternberg, P. W., 567

Stewart, W. B., 657, 663, 664, 665, 685

Stockbridge, N., 520

Straschill, M., 75

Straughan, D. W., 300

Strichartz, G. R., 169

Strowbridge, B. W., 685

Stryker, M. P., 618, 619, 620, 625, 626, 628, 633, 634, 635, 729

Stuart, A. E., 515, 518, 669, 670, 671

Suh, B. C., 176, 177

Sur, M., 450, 626

Sutcliffe, J. G., 38, 40, 47

Swartz, B. E., 90

Szabo, G., 175

Szapiro, G., 214, 215

Takata, M., 507, 510, 511

Tanaka, K., 267, 744

Tang, Y. Y., 580

Tasaki, I., 147, 167, 166, 499, 720, 726, 732, 735

Taylor, R., 502, 503, 569

Tehovnik, E. J., 621, 632, 633, 634

Teicher, M. H., 663

Teillet, M. A., 346, 350, 352, 353, 354, 364, 367, 368, 369

Tekkök, S. B. 321

Terlau, H., 154

Thach, W. T., 260

Thibert, C., 367

Thompson, R., 458

Tighilet, B., 263

Toivonen, S., 348

Tolias, A. S., 631, 634

Tramo, M. J., 130

Trembleau, A., 40

Trentin, A., 362

Trombley, P. Q., 672, 685

True, S. D., 619, 624, 634

Tse, A., 178

Tse, F. W., 178

Turk, D. J., 130

Ulbricht, W., 162, 510

Umeno, M. M., 738

Uyeda, A. A., 68, 69, 76, 77

Valentino, K. L., 260

Van Horn, J. D., 130

Van Sluyters, R. C., 626

Vásquez, B. J., 195, 196, 197, 202

Vassalli, A., 671

Velletri Glass, A., 108, 113

Verduzco-Flores, S., 90

Vianna, M. R., 207, 213, 214, 215

Villa, A. E. P., 90

Vincenzi, F. F., 157

Viola, H., 209

Vogel, W., 102, 162, 169

Volpe, B. T., 114, 116, 130

von Helmholtz, H., 737

von Holst, E., 737

Waldow, U., 685

Wall, P. D., 649, 656, 724

Walsh, C., 364

Walz, R., 207, 209

Wang, X., 462

Warren, R. A., 263

Warrington, E. R., 212

Wassle, H., 629

Watanabe, Y., 83

Watkins, W. B., 299

Waxman, S. G., 518

Wedner, H. J., 25

Werblin, F. S., 627, 628, 657, 669

Werman, R., 304, 309

Werner, H., 162, 510, 609, 611

Wessinger, C. M., 114, 117, 130

Westerfield, M., 498, 500, 501, 516, 522

Westgaard, R. H., 405, 406, 414, 419

Whitcomb, E. R., 493

White, M. W., 452

Whitlock, J. R., 211, 212

Whittaker, V. P., 296

Wickelgren, B., 727

Wiener, M., 610

Wiesel, T. N., 61, 71, 253, 520, 568, 612, 614, 625, 627, 653, 662, 717, 720, 723, 724

Willhite, D. C., 676, 685

Williamson, A., 685

Wise, S. P., 235, 260

Wolbarsht, M. L., 616, 723

Wolff, E., 338–41, 344, 346, 361

Wolfman, C., 205, 207, 209

Wollmuth, L. P., 169, 176

Woodhull, A. M., 167, 170

Woolf, T. B., 667, 685

Worden, F. G., 74

Wu, C. C., 48

Wurtman, R. J., 544

Wurtz, R. H., 705–747

Xia, A., 674, 685

Xiong, W., 673

Yajeya, J., 84, 87

Yamamori, T., 354

Yang, J., 168, 686

Ye, J. H., 322

Yen, C. T., 261, 263

Yim, C. Y., 320

Yim, G. K. W., 305

Young, W. G., 39, 41, 47

Zeki, S. M., 631, 742

Zeng, S., 685

Zhao, Y. T., 320

Zieglgansberger, W., 34

Zigmond, M., 549

Ziller, C., 361

Zinn, C. G., 208

Zipser, D., 90

Zornetzer, S. F., 201

Zufall, F., 671