Dissociating neural circuits of social and prosocial reward in rat helping behavior

Helping behavior in rodents provides a powerful model for studying neurobiological underpinnings of prosocial motivation. Previously, rats allowed to release a trapped conspecific demonstrated prosocial motivation selectively toward ingroup members. Here, a refined version of the helping behavior test (HBT) allowed trapped rats to be freed without ensuing social contact, dissociating social from prosocial reward. In this "separated" HBT (SHBT), helping was not biased, as rats equally released ingroup and outgroup members. Whole-brain c-Fos mapping revealed a subset of the standard HBT prosocial brain network engaged in the SHBT. Observed absence of activity in the nucleus accumbens (NAc) instigated a chemogenetic investigation of this region. NAc activity was not necessary for helping, but significantly reduced affiliative behavior. The recruitment of Oxtr+ cells in sensory cortices suggests modulated sensory processing. Together, these findings dissociate neural circuits underlying social and prosocial motivation and provide a mechanistic framework for studying mammalian prosocial behavior.