Research Hit: How Your Brain Stores Fearful Memories of Others

Research into mice shows social fearful memories being recorded in their brains

Our brains must be sensitive to social threat - this is a major threat I would have thought?
Indeed and this is precisely what Pegah Kassraian et al. of Columbia University investigated to give us some clear answers of how social threatening and socially safe memories are saved.

How on earth can you do this with mice?
Good question - remember mice are also social creatures and their brains are good models for us human beings but being far less complex, of course.
We already know that the hippocampus is a key memory area that this also stores various memories - notably physical locations (many memories are also distributed across the brain).
In this experiment they had mice scamper off and they met a stranger mouse in one location and in this location they were given a mild electric shock to trigger threat and negativity with this individual. In the opposite direction they also came across a strenger mouse but were not shocked. This was the “safe place”.
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And what happened?
Well, as to be expected they quickly learned where the safe place was but the interesting bit is that they focused on two regions of the hippocampus known as CA1 and CA2.
A common method in research nowadays is to silence various regions chemically or with methods such as laser activation/deactivation. In this experiment they could then silence these particular brain regions separately and then see what happens to behaviour after this silencing.
In the normal situation the mice would avoid the location and stranger where they got zapped and go towards the safe location.
Silencing these regions CA1 and CA2 had different effects.

How different?
Well when they silenced CA1 the mice could no longer remember where they had been shocked but still avoided the mouse that had been in that location. So they remembered a social threat but not the location. Or in other words CA1 is a region that seems dedicated (also supporting previous research) that stores locations and places.
The opposite happened when CA2 was silenced - the mice remembered the location but became indiscriminately afraid of both mice.

So regions in the hippocampus record different types of memory - and we need both to operate together.
Yes, social threat is recorded in CA2 and location threat in CA1. Using both gives more nuanced and complete picture. And fascinating to know that single small brain regions in our hippocampus records social threat!

Nice to know where social threat sits in our brain
Indeed. We do need to see that this translates into human beings also.

By Andy Habermacher of Leading Brains
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Pegah Kassraian, Shivani K. Bigler, Diana M. Gilly Suarez, et al.
The hippocampal CA2 region discriminates social threat from social safety.
Nature Neuroscience, 2024
DOI: 10.1038/s41593-024-01771-8