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Of Biscotti and Memories

  • Published19 Aug 2013
  • Author Leanne Boucher
  • Source BrainFacts/SfN
Marcel Proust
Marcel Proust (Wikipedia)

Ever had the experience of smelling something and then being automatically transported back in time? It’s as though your olfactory sense is the “on” switch to your memories.

The French novelist Marcel Proust captures this phenomenon so much more eloquently that I ever could in his novel, Swann's Way (1913). He writes,

But when from a long-distant past nothing subsists, after the people are dead, after the things are broken and scattered, taste and smell alone, more fragile but more enduring, more immaterial, more persistent, more faithful, remain poised a long time, like souls, remembering, waiting, hoping, amid the ruins of all the rest; and bear unflinchingly, in the tiny and almost impalpable drop of their essence, the vast structure of recollection.

The Proust Phenomenon, as it is referred to, is the experience of a strong emotional memory triggered by the smell of something. Think of all the times you’ve walked into your grandparents’ or parents’ houses and have smelled something cooking on the stove and all of a sudden you’re a kid again running around their knees, tripping on your feet, grabbing the tablecloth on your way down to the floor, silverware and dishes raining down on your head.

Or you walk into a hospital for a routine visit to your doctor and you smell the antiseptic they used when your Grandma was sick and you are transported back to that terrible hellish time.

Or you’re walking in the mall and you get a whiff of someone’s perfume or cologne and you immediately picture your first love and you on your first date when you first awkwardly said “I love you” to each other.

All these memories are what we call autobiographical memories, a type of episodic memory, because they are specific to the person who is remembering them. Different areas of the brain encode, process, and store different types of memories.

The amygdala is an almond-shaped structure located in the medial temporal lobe (i.e. the sides of your head) that is involved in processing emotional memories. It is connected to many areas of the brain, including the hippocampus, a seahorse-shaped structure involved in the formation of new memories. (Neat 3-D animation of the hippocampus can be found here; the amygdala is just at the tip of the hippocampus.)

How do we know which areas are involved in what types of memories? Neuroscientists use a variety of brain imaging techniques to study brain function including functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and computerized tomography (CT), to name a just a few. These techniques allow neuroscientists to take a picture of the brain while a person is doing some task.

For example, in a PET study, people are placed in a scanner after being injected with a small amount of a radioisotope (this is relatively safe) while they do some task. The PET scanner measures the amount of blood flow to/from a particular area of the brain by measuring the amount of radioisotope present in the brain matter. The idea is that if an area of the brain is being used during the task, blood will flow to that area.

Researchers Zald and Pardo (1997) utilized PET to study what areas of the brain were involved with processing aversive olfactory stimuli. Among other findings, they found that the amygdalae (both the left and right amygdala) were involved in the processing of aversive olfactory stimuli. This is consistent with research that shows that the amygdala is connected to the olfactory bulb where smell is processed in the brain (see Park et al., 2013 for a recent study).

The findings from brain studies such as this one can be bolstered by behavioral studies that show that olfactory cues are best when recalling autobiographical events. Chu and Down (2002) conducted two experiments in which they had participants relate a word to an event from their past (i.e. an autobiographical memory). The word was a “smell word” such as chocolate, peppermint, etc.

So for example, if I gave you the word chocolate, you would have three minutes to talk out loud about an event in your life that you associate with the word chocolate. Participants then rated their memories on a number of dimensions, such as how pleasant the memory was, on a 1-7 scale.

Then, participants were instructed to do one of three things: 1) they were given the “smell word” again and were told to try to recall any more details; 2) they were told that smelling helps memory sometimes, so please smell this jar and see if you can recall any more details; or 3) they were told that smelling helps memory sometimes, so please smell this jar and see if you can recall any more details. You read that right – the instructions in the #2 and #3 conditions are identical. The difference is that in #2, the smell matched the word they had previously associated with the memory (congruent condition); in #3, the smell did not match (incongruent condition).

Once again, participants rated their memories on a number of dimensions on a scale of 1-7. The researchers found that autobiographical memories cued by matching olfactory cues were rated more positively and contained more details compared to other types of cues. Thus, olfaction seems to do a pretty good job at helping us remember events from our past. Furthermore, not only do we remember more, but Matsunaga and colleagues found that we become more relaxed, less anxious, and are in a much better mood when one smells a “nostalgic odor” as compared to a neutral odor.

Proust was not a neuroscientist (although there is a fascinating book with a title declaring that he was), but he was able to describe beautifully the experience and the feelings one gets when reminded of better times. In perhaps a more well-known verse from Proust, he describes a time when he remembered having tea with his Aunt, a memory triggered by dipping a madeleine in some tea. He writes,

No sooner had the warm liquid mixed with the crumbs touched my palate than a shudder ran through me and I stopped, intent upon the extraordinary thing that was happening to me. An exquisite pleasure had invaded my senses, something isolated, detached, with no suggestion of its origin. And at once the vicissitudes of life had become indifferent to me, its disasters innocuous, its brevity illusory – this new sensation having had on me the effect which love has of filling me with a precious essence; or rather this essence was not in me it was me.
Biscotti

This is perhaps why comfort food is so comforting. For me, one smell of a Stella Doro biscotti and I’m whisked back to my childhood eating those cookies with my grandparents in their kitchen. I smile thinking about all the good times we spent in that kitchen through the years and I thank my amygdala for being so well connected.



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BrainFacts/SfN

Chu, S. & Downes, J.J. (2002). Proust nose best: odors are better cues of autobiographical memory. Memory and Cognition, 30(4), 511-518. Link

Matsunaga, M., Isowa, T., Yamakawa, K., Kawanishi, Y., Tsuboi, H., Kaneko, H., Sadato, N., Oshida, A., Katayama, A., Kashiwagi, M., & Ohira, H. (2011). Psychological and physiological responses to odor-evoked autobiographic memory. Neuro Endocrinology Letters, 32(6), 774-780. Link

Park, S.K., Kim, J.H., Yang, E.S., Ahn, D.K., Moon, C., & Bae, Y.C. (2013). Ultrastructure and synaptic connectivity of main and accessory olfactory bulb efferent projections terminating in the rat anterior piriform cortex and medial amygdala. Brain Structure and Function. [Epub ahead of print] Link

Zald, D.H. & Pardo, J.V. (1997). Emotion, olfaction, and the human amygdala: Amygdala activation during aversive olfactorystimulation. Proceedings of the National Academy Sciences, 94(8), 4119–4124. Link

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