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Hello everyone, SCIENSPOT is a podcast that shines a spotlight on the latest scientific technology from Japan.
Your host is REN from SCIEN-TALK.
社会的記憶の神経メカニズム
Today, we are looking at a discovery about how our brains manage social memory,
the complex ability to remember people and their characteristics.
Our research group read why University of Tokyo has uncovered the neural coding system
the brains use to organize information about specific individuals and their attributes.
Every day, we encounter various people and our brain must quickly recognize who they are
and recall the associated memories.
This mechanism is called social memory.
In mammals, including humans, a small sub-region of the hippocampus,
the brain's memory center, called the ventral CA1 region, is known to be viral for strong social memories.
Scientists knew that this idea stored memories of acquaintances,
but they didn't know how the neurons in that region organized information
about attributes like gender and genetic string within those individual memories.
The researchers used detailed neural recording techniques in mice to record the activity within the brain region.
Mice were trained to form social memories of four other mice that differed in two attributes,
gender, male or female, and genetic string.
When the subject mouse recorded these memories,
the researchers found that the social memory neurons were actually two distinct types.
First one is identity cells.
These cells responded with selectivity to a specific individual regarding all their general attributes.
Second one is property cells.
These cells responded to an attribute, like female or the string, regardless of the specific individual.
The data showed that the combination of identity cells and property cells
社会的記憶の神経メカニズム
was used to represent the memory of a particular friend.
In fact, they could predict with high accuracy which the four individuals the mice were recording
simply by looking at the pattern of activity in the neurons.
They also found the activity of these social memory cells was strongly regulated by the hippocampal theta wave.
The identity and property cells tended to fire close to the throw of the theta wave,
suggesting the theta wave acts as a crucial timing mechanism or unit for recalling social memories.
Finally, the team used advanced techniques including optogenetics and the conditioned place preference test
to experimentally access and manipulate the memories.
When they artificially activated the memory cells associated with female mice,
the subject mouse spent significantly more time and location associated with that activation.
This confirmed that the memory of the female mice had a positive rewarding property.
Crucially, this reward was found to be delivered specifically by activating the property cells
that encode the shared female attribute.
Think of the brain's social memory system as a library database.
To recall a friend, the system doesn't just use a single, comprehensive file.
Instead, it used two linked records, a unique identity ID,
that is a unique photo and name of the friend funded by identity cells,
and common property tags like female or colleague handled by property cells.
The brain retrieves the memory by combining the two.
Furthermore, certain property tags, like the female tag in this study,
come preloaded with a positive emotional reward chip.
This research is highly significant because it reveals that the brain processes social information
社会的記憶のメカニズム
in a layered, compound manner,
and distinguishing between the specific individual and their genetic attributes.
This dual coding system advances our understanding of how complex social information is stored.
Crucially, this finding offers new insights into the mechanisms underlying disorders
where social memory is impaired, such as autism spectrum disorder.
It gives us hope for future research into treatments for these conditions.
That's all for today's SciencePod.
This podcast is broadcast in both Japanese and English.
I'd love for you to listen to the podcast and post your thoughts with the hashtag SciencePod.
Thank you for listening and see you next time.
