Washington D.C: The memories of the COVID-19 pandemic are likely to be etched in human 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 to separate memories can remain precise and robust," added Udakis.
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.