Social decision making, hierarchy and emotional contagion are interconnected by the basolateral amygdala

Abstract Decisions in social contexts might lead to choices favoring self- or others-interest, depending on the relationships between individuals. Prosocial and helping behaviors are evolutionary conserved across mammals. However, the neurobiological bases of choices that benefit others at a personal cost are not understood. Here, we revealed the role of the basolateral amygdala (BLA) in altruistic and selfish choices. We developed a two-choice social decision-making task in which mice could decide to share or not a positive reinforcement with their conspecifics. Preference for altruistic choices was more evident in males and if the conspecific was familiar. In particular, altruistic choices were associated with social dominance and affective state matching between individuals. Chemogenetic BLA neuronal silencing induced lower ranking hierarchy and less preference for altruistic choices. This provides a neurobiological comparative model of altruistic and selfish choices versus dominance hierarchy and emotional contagion, with relevance to pathologies associated with dysfunctions in social decision-making.