Individual differences in prosocial learning are represented in the hippocampal dorsal CA1

Learning from others is among the main expressions of humans’ social nature. Evolution has favored this capacity, which is conserved across mammals, for its environmental advantages and benefits for the species compared to trial-and-error learning. Animals can learn about danger by observing their conspecifics, but if or how they acquire prosocial behaviors is not understood. Here, we found that mice by observing a demonstrator learned to take actions that benefit others, which were goal-directed and flexible. We found that the hippocampal dorsal CA1 (dCA1) activity is required to learn a given observed prosocial behavior. Chemogenetic silencing of the dCA1 impaired the acquisition of a social preference in mice with high prosocial tendency. Fiber-photometry recording revealed individual differences in dCA1 activity patterns during observation that closely tracked the observer's later prosocial or selfish behavioral propensities. Optogenetic manipulations demonstrated that the dCA1 is key in acquiring observed social behaviors and can orient a mouse’s actions toward prosocial or selfish choices in future interactions. Our study provides a model of social transmission of knowledge that guides prosocial behavior in mice that can be relevant for studying neuropsychiatric and neurodevelopmental disorders, in which the ability to learn from others’ actions is often compromised.