Revealing neural mechanisms underlying various social behaviors by optogenetics and physiological methods, from the viewpoint of social memory engram in the hippocampus.
Optogenetic analysis of neural circuits for social behavior.
For animals who form a society, it is crucial to remember and recognize different conspecific individuals (i.e. having “social memory”), and exhibit appropriate social behavior towards each other. Using optogenetic techniques, we demonstrated that ventral CA1 (vCA1) pyramidal neurons in the hippocampus store social memory (social memory engram). Even if the memory seemed lost after long separation periods, optogenetic activation of the engram can fully restore that social memory. Additionally, artificial association between social engram encoding the memory of a specific individual with fear or reward events can elicit avoidance.
On the other hand, one tiny dissonance in social memory can easily disrupt the appropriate social behavior, even in humans. Social impairments caused by genetic mutation, especially those related to familiarization with other individuals, are commonly exhibited by patients diagnosed with autism spectrum disorder. Autistic patients have difficulty either with social memory itself, or showing typical behavior of social familiarity driven by social memory. We attempt to reveal the mysterious underpinnings of social memory in autism, while aiming at the ultimate goal of our lab — the improvement of autism treatment.
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