[초청강연] Projection-specific mechanisms of learning and memory

My laboratory is investigating the molecular and cellular mechanism underlying behaviors mainly
learning/memory and social behaviors in mice. In particular, we are interested in dissecting cell types and
neural projections and finding underlying plasticity mechanisms selectively subserving these brain functions in
healthy and diseased brains. For example, we are studying the impacts of mutations in RAS signaling pathway
on the function and plasticity of distinct hippocampal cell types including glia. In this seminar, I will introduce
and discuss our recent finding showing that mPFC-nucleus accumbens circuit is selectively involved in social
memory in mice. While mPFC is known to play important roles in social behaviors, how early social experiences
affect the mPFC and its subcortical circuit remains unclear. We found that mice singly housed for 8 weeks after
weaning (SH) show a social recognition/memory deficit, even after 4 weeks of re-socialization. In SH mice,
prefrontal infralimbic (IL) neurons projecting to the shell region of nucleus accumbens (NAcSh) show
decreased excitability compared to group housed (GH) mice. NAcSh-projecting IL neurons are activated when
GH mice encounter a familiar conspecific, which not observed in SH mice. Chemogenetic inhibition of NAcSh-
projecting IL neurons in normal mice impairs social recognition memory without affecting social preference,
while activation of these neurons reverses social recognition deficit in SH mice. Our findings demonstrate that
early social experience critically affects the mPFC IL-NAcSh projection, the activation of which is required for
the social recognition by encoding information for social familiarity.