19 October 2021

Ah, we meet … again?

The Back Page

Do you never forget a face, or are you a social goldfish?

Your Back Page correspondent somehow combines these qualities, being a super-recogniser of faces who forgets every other detail about a new acquaintance before they’ve even finished introducing themselves.

So this study about serotonin and formation of social memories – in mice – caught our attention.

Stanford professor of psychiatry Robert Malenka, postdoc Dr Xiaoting Wu and colleagues were able to identify the neurons that tell a mouse it’s interacting with a mouse it hasn’t met before and generate a memory for that other mouse.

They then were able to dial the activity of these neurons – known as the medial septum – down and up using optogenetics and two drug combinations, to either inhibit the formation of a new acquaintance memory altogether or to make it last 10 times as long.

They then were able to tie the whole process to serotonin: a novel encounter activates serotonin production, which in turn activates the medial septum via a particular serotonin-sensitive receptor. Blocking the flow of serotonin or this receptor molecule stopped social memories forming, but giving the mouse extra serotonin made the memories, again, last 10 times longer than normal.

If only there were a substance that mice, or people, could take before large gatherings that would facilitate and intensify social interactions by promoting the release of serotonin.

But the applications extend far beyond putting on better mouse parties, according to the team. Targeting just these serotonin receptors could improve social memory in people with conditions like depression and PTSD, they said.

And the same team has previously explored the use of MDMA in mouse models of autism spectrum disorder and found that the drug reversed sociability deficits in ASD and increased sociability in control mice. 

If you see something that makes you want to hug a stranger, send it to felicity@medicalrepublic.com.au

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