Representation of sex-specific social memory in ventral CA1 neurons.

Recognizing familiar individuals is crucial for adaptive social interactions among animals. However, the multidimensional nature of social memory encompassing sexual information remains unelucidated. We found that neurons in the ventral CA1 region (vCA1) of the mouse hippocampus encoded the identities and social properties, specifically sex and strain, of familiar conspecifics by using both rate and theta-based temporal coding. Optogenetic reactivation of social memories of females, but not males, induced place preference. Ablation of the upstream hippocampal dorsal CA2 region or the medial amygdala disrupted the representation of sex and the sexual dichotomy of social memory valence. Thus, vCA1 neurons use dual coding schemes to represent the identities and social properties of familiar conspecifics as a cohesive memory.