Research unravels what makes memories so detailed and enduring

Date:
September 8, 2020
Source:
University of Bristol
Summary:
Researchers report a breakthrough in understanding how memories
can be so distinct and long-lasting without getting muddled up.



FULL STORY ==========================================================================
In years to come, our personal memories of the COVID-19 pandemic are
likely to be etched in our minds with precision and clarity, distinct
from other memories of 2020. The process which makes this possible has
eluded scientists for many decades, but research led by the University
of Bristol has made a breakthrough in understanding how memories can be
so distinct and long-lasting without getting muddled up.


==========================================================================
The study, published in Nature Communications, describes a newly
discovered mechanism of learning in the brain shown to stabilise memories
and reduce interference between them. Its findings also provide new
insight into how humans form expectations and make accurate predictions
about what could happen in future.

Memories are created when the connections between the nerve cells
which send and receive signals from the brain are made stronger. This
process has long been associated with changes to connections that
excite neighbouring nerve cells in the hippocampus, a region of the
brain crucial for memory formation.

These excitatory connections must be balanced with inhibitory connections, which dampen nerve cell activity, for healthy brain function. The role
of changes to inhibitory connection strength had not previously been
considered and the researchers found that inhibitory connections between
nerve cells, known as neurons, can similarly be strengthened.

Working together with computational neuroscientists at Imperial College
London, the researchers showed how this allows the stabilisation of
memory representations.

Their findings uncover for the first time how two different types of
inhibitory connections (from parvalbumin and somatostatin expressing
neurons) can also vary and increase their strength, just like excitatory connections. Moreover, computational modelling demonstrated this
inhibitory learning enables the hippocampus to stabilise changes to
excitatory connection strength, which prevents interfering information
from disrupting memories.



========================================================================== First author Dr Matt Udakis, Research Associate at the School of
Physiology, Pharmacology and Neuroscience, said: "We were all really
excited when we discovered these two types of inhibitory neurons could
alter their connections and partake in learning.

""It provides an explanation for what we all know to be true; that
memories do not disappear as soon as we encounter a new experience. These
new findings will help us understand why that is.

"The computer modelling gave us important new insight into how inhibitory learning enables memories to be stable over time and not be susceptible to interference. That's really important as it has previously been unclear
how separate memories can remain precise and robust." The research was
funded by the UKRI's Biotechnology and Biological Sciences Research
Council, which has awarded the teams further funding to develop this
research and test their predictions from these findings by measuring
the stability of memory representations.

Senior author Professor Jack Mellor, Professor in Neuroscience at
the Centre for Synaptic Plasticity, said: "Memories form the basis
of our expectations about future events and enable us to make more
accurate predictions. What the brain is constantly doing is matching our expectations to reality, finding out where mismatches occur, and using
this information to determine what we need to learn.

"We believe what we have discovered plays a crucial role in assessing
how accurate our predictions are and therefore what is important new information.

In the current climate, our ability to manage our expectations and
make accurate predictions has never been more important." "This is
also a great example of how research at the interface of two different disciplines can deliver exciting science with truly new insights. Memory researchers within Bristol Neuroscience form one of the largest
communities of memory-focussed research in the UK spanning a broad range
of expertise and approaches. It was a great opportunity to work together
and start to answer these big questions, which neuroscientists have been grappling with for decades and have wide-reaching implications."

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


========================================================================== Journal Reference:
1. Matt Udakis, Victor Pedrosa, Sophie E. L. Chamberlain, Claudia
Clopath,
Jack R. Mellor. Interneuron-specific plasticity at parvalbumin
and somatostatin inhibitory synapses onto CA1 pyramidal neurons
shapes hippocampal output. Nature Communications, 2020; 11 (1)
DOI: 10.1038/ s41467-020-18074-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200908131139.htm

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