From the first large studies monitoring the mental functioning of the same group of healthy humans over many years, scientists have uncovered unexpected results.

Touch is the sense by which we determine the characteristics of objects: size, shape, and texture.

Insulation covering wires preserves the strength of the electrical signals that travel through them. The myelin sheath covering axons serves a similar purpose.

Medical professionals have come to rely on even more specialized forms of the MRI machine, each suited to spotting specific warning signs.

One of the most common and least understood neurobiological disorders, Tourette syndrome is an inherited disorder that affects about 200,000 Americans. Males are affected three to four times as often as females.

PET is one of the most important techniques for measuring blood flow or energy consumption in the brain. This method of measuring brain function is based on the detection of radioactivity emitted when positrons, positively charged particles, undergo radioactive decay in the brain.

Our best insights into how the normal brain ages come from long-term studies of the nervous system that began decades ago.

Optical imaging relies on shining weak lasers through the skull to visualize brain activity. These techniques are inexpensive and relatively portable. They are also silent and safe: Because only extremely weak lasers are used, these methods can be used to study everyone, even infants.

The brain uses a variety of chemicals called neurotransmitters to communicate between brain cells.

Researchers throughout the world are pursuing a variety of new ways to repair or replace neurons and other cells in the brain. For the most part, these experimental approaches are still being worked out in animals and cannot be considered therapies for humans at this time.