Today's "Nature": Exploring the mystery of a hundred years of memory, why some smells always remind people of the past

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Some smells and sounds will magically open the valve of memory and remind you of the streets in your childhood, the dining table at your grandmother's house, or the scene of your first date
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Psychologists began to study this memory phenomenon more than one hundred years ago
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In the 1890 classic "The Principles of Psychology" (The Principles of Psychology), the famous American psychologist William James once specifically described it
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This ability to remember irrelevant items (such as smells and locations, sounds and events) is called "associative memory" and is one of the most basic forms of memory in daily life
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In Alzheimer's disease and other diseases that affect the cognitive function of the brain, the patient's associated memory ability will decline
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However, so far, the mechanism behind how the brain forms associative memories has remained a mystery
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In a research paper just launched in the top academic journal "Nature", neuroscientists at the University of California, Irvine (UC Irvine) for the first time found a specific type of memory in the medial temporal lobe, the memory center of the brain.
Neurons have discovered that they are responsible for acquiring new associative memories, and found a way to control these associative memory neurons
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These special neurons are located in the lateral entorhinal cortex (LEC) of the medial temporal lobe and are called fan cells
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▲The location of sector cells in the mouse brain (picture source: Reference [2]) The researchers used electrophysiological recording and optogenetic methods to record the activity of the sector cells in mice, and found that when the mice learned to be unrelated to the original The fan-shaped cells play an important role when the specific scent of scent is associated with reward
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Without these cells, mice can recall the associations they have learned, but cannot form new associations, indicating that fan-shaped cells are necessary for the successful acquisition of new association memories
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Another important finding of this study is that sector cells encode associated memories that are controlled by dopamine signals
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Dopamine is a chemical substance that acts in the brain when we experience pleasure or reward
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▲Study diagram (picture source: reference [2]) Using fiber photometry (fibre photometry) technology to record changes in neuron activity, the researchers found that dopamine sends a novelty-induced reward expectation signal to the lateral entorhinal cortex
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If the dopamine signal in this area is inhibited, the sector cells will be destroyed to form new associated memories
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"We never thought that dopamine is involved in the memory circuit," said Professor Kei Igarashi, who led the study.
"However, as the evidence accumulates, it is clear that dopamine is involved
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" The researchers pointed out that these findings are about understanding how the brain is.
An important step in the formation of associative memory, and lay the foundation for future development of treatments to alleviate the loss of associative memory in Alzheimer's disease
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Reference materials: [1] Lee, JY, Jun, H.
, Soma, S.
et al.
Dopamine facilitates associative memory encoding in the entorhinal cortex.
Nature (2021).
https://doi.
org/10.
1038/s41586-021 -03948-8[2] New research “sniffs out” how associative memories are formed.
Retrieved Sep.
23, 2021 from https://news.
uci.
edu/2021/09/22/new-research-sniffs-out- how-associative-memories-are-formed/