Valence-dependent Synaptic Plasticity Drives Approach and Avoidance Behavior in Social Context

The nature of social interactions determines engagement or avoidance with conspecifics. Here, we explore the circuit mechanisms that guide approach or avoidance behavior in mice based on the valence of previous social interactions. We identify a novel circuit connecting D1 receptor expressing neurons of the anterior insular cortex (AIC) to D1R expressing neurons of the nucleus accumbens (NAc). These cells become active during social interactions in a valence-dependent manner. Lower frequency patterns encoded appetitive interactions, while aversive interactions led to higher activation. These activity patterns elicited distinct forms of synaptic plasticity in the accumbal target neurons, which were causal for subsequent approach or avoidance behavior. Our results unravel the synaptic mechanisms instructing behavior after the social interaction of opposite valence.