Watarai, A.; Tao, K.; Okuyama, T.

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 medial amygdala (MeA) or the hippocampal dorsal CA2 region (dCA2) disrupted the representation of sex and the sexual dimorphism of social memory valence. Selective reactivation of overlapping neural populations of distinct female social memories representing the female sex was sufficient to induce preference. Thus, vCA1 neurons employ dual coding schemes to represent the identities and social properties of familiar conspecifics as a cohesive memory.