Why do we forget? New theory proposes 'forgetting' is actually a form of learning

Date:
January 13, 2022
Source:
Trinity College Dublin
Summary:
We create countless memories as we live our lives but many of these
we forget. Why? Counter to the general assumption that memories
simply decay with time, 'forgetting' might not be a bad thing --
that is according to scientists who believe it may represent a
form of learning.



FULL STORY ==========================================================================
We create countless memories as we live our lives but many of these
we forget.

Why? Counter to the general assumption that memories simply decay with
time, 'forgetting' might not be a bad thing -- that is according to
scientists who believe it may represent a form of learning.


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The scientists behind the new theory -- outlined today in leading
international journal Nature Reviews Neuroscience --suggest that changes
in our ability to access specific memories are based on environmental
feedback and predictability. Rather than being a bug, forgetting may be
a functional feature of the brain, allowing it to interact dynamically
with the environment.

In a changing world like the one we and many other organisms live in, forgetting some memories can be beneficial as this can lead to more
flexible behaviour and better decision-making. If memories were gained
in circumstances that are not wholly relevant to the current environment, forgetting them can be a positive change that improves our wellbeing.

So, in effect, the scientists believe we learn to forget some memories
while retaining others that are important. Forgetting of course comes at
the cost of lost information, but a growing body of research indicates
that, at least in some cases, forgetting is due to altered memory access
rather than memory loss.

The new theory has been proposed by Dr Toma's Ryan, Associate Professor
in the School of Biochemistry and Immunology and the Trinity College
Institute of Neuroscience at Trinity College Dublin, and Dr Paul
Frankland, Professor in the Department of Psychology at the University
of Toronto and the Hospital for Sick Children in Toronto.

Both Dr Ryan and Dr Frankland are fellows of the Canadian global research organization CIFAR, which enabled this collaboration through its Child &
Brain Development program, which is pursuing interdisciplinary work in
this area.



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Dr Ryan, whose research team is based in the Trinity Biomedical Sciences Institute (TBSI), said: "Memories are stored in ensembles of neurons
called 'engram cells' and successful recall of these memories involves
the reactivation of these ensembles. The logical extension of this
is that forgetting occurs when engram cells cannot be reactivated. The
memories themselves are still there, but if the specific ensembles cannot
be activated they can't be recalled. It's as if the memories are stored
in a safe but you can't remember the code to unlock it.

"Our new theory proposes that forgetting is due to circuit remodelling
that switches engram cells from an accessible to an inaccessible
state. Because the rate of forgetting is impacted by environmental
conditions, we propose that forgetting is actually a form of learning
that alters memory accessibility in line with the environment and how predictable it is." Dr Frankland added: "There are multiple ways in
which our brains forget, but all of them act to make the engram -- the
physical embodiment of a memory -- harder to access." Speaking to the
case of pathological forgetting in disease, Dr Ryan and Dr Frankland
note: "Importantly, we believe that this 'natural forgetting' is
reversible in certain circumstances, and that in disease states --
such as in people living with Alzheimer's disease for example -- these
natural forgetting mechanisms are hijacked, which results in greatly
reduced engram cell accessibility and pathological memory loss."
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Content may be edited for style and length.


========================================================================== Journal Reference:
1. Toma's J. Ryan, Paul W. Frankland. Forgetting as a form of adaptive
engram cell plasticity. Nature Reviews Neuroscience, 2022; DOI:
10.1038/ s41583-021-00548-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220113111421.htm
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