New research 'sniffs out' how associative memories are formed

Date:
September 22, 2021
Source:
University of California - Irvine
Summary:
Has the scent of freshly baked chocolate chip cookies ever taken
you back to afternoons at your grandmother's house? Has an old
song ever brought back memories of a first date? The ability to
remember relationships between unrelated items (an odor and a
location, a song and an event) is known as associative memory.



FULL STORY ==========================================================================
Has the scent of freshly baked chocolate chip cookies ever taken you back
to afternoons at your grandmother's house? Has an old song ever brought
back memories of a first date? The ability to remember relationships
between unrelated items (an odor and a location, a song and an event)
is known as associative memory.


========================================================================== Psychologists began studying associative memory in the 1800s, with William James describing the phenomenon in his 1890 classic The Principles of Psychology.Scientists today agree that the structures responsible for the formation of associative memory are found in the medial temporal lobe,
or the famous "memory center" of the brain, but the particular cells
involved, and how those cells are controlled, have remained a mystery
until now.

Neuroscientists at the University of California, Irvine have discovered specific types of neurons within the memory center of the brain that are responsible for acquiring new associative memories. Additionally, they
have discovered how these associative memory neurons are controlled. We
rely on associative memories in our everyday lives and this research is
an important step in understanding the detailed mechanism of how these
types of memories are formed in the brain.

"Although associative memory is one of the most basic forms of memory
in our everyday life, mechanisms underlying associative memory remain
unclear" said lead researcher Kei Igarashi, faculty fellow of the Center
for the Neurobiology of Learning and Memory and assistant professor of
anatomy & neurobiology at the UCI School of Medicine.

The study published today in the journal Nature, reports for the first
time, that specific cells in the lateral entorhinal cortex of the medial temporal lobe, called fan cells, are required for the acquisition of new associative memories and that these cells are controlled by dopamine,
a brain chemical known to be involved in our experience of pleasure
or reward.

In the study, researchers used electrophysiological recordings and
optogenetics to record and control activity from fan cells in mice
as they learn to associate specific odors with rewards. This approach
led researchers to discover that fan cells compute and represent the association of the two new unrelated items (odor and reward). These
fan cells are required for successful acquisition of new associative
memories. Without these cells, pre-learned associations can be retrieved,
but the new associations cannot be acquired.

Additionally acquiring new associations also requires dopamine.

"We never expected that dopamine is involved in the memory
circuit. However, when the evidence accumulated, it gradually became
clear that dopamine is involved," said Igarashi. "These experiments were
like a detective story for us, and we are excited about the results."
This discovery is an important piece in the puzzle of understanding
how memories are formed in the brain and lays a foundation on which
other researchers can continue to build. Associative memory abilities
are known to decline in neurodegenerative diseases like Alzheimer's
Disease. Understanding the neurobiological mechanism of how these memories
are formed is the first step to developing therapeutics to slow the loss
of associative memory abilities in Alzheimer's Disease.

========================================================================== Story Source: Materials provided by
University_of_California_-_Irvine. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Lee, J.Y., Jun, H., Soma, S. et al. Dopamine facilitates associative
memory encoding in the entorhinal cortex. Nature, 2021 DOI:
10.1038/ s41586-021-03948-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210922133058.htm

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