Social Closeness and Reward Sensitivity Enhance Corticostriatal Function during Experiences of Shared Rewards

Description: While prior research has demonstrated enhanced striatal response when sharing rewards with close social connections, less is known about how individual differences affect VS activation and connectivity when experiencing rewards within social contexts. Given that self-reported sensitivity and level of substance use have been associated with differences in VS activation, we set out to investigate whether these two factors would be independently associated with enhancements to neural reward responses from social contexts. In this pre-registered study, participants (N=45) underwent fMRI while playing a card guessing game in which correct or incorrect guesses resulted in monetary gains and losses that were shared evenly with either a close friend, stranger (confederate), or non-human partner. Consistent with our prior work, we found increased VS activation when sharing rewards with a socially close peer as opposed to an out-of-network stranger. Reward sensitivity negatively moderated the degree of this enhancement. We also found enhanced connectivity between the VS and temporoparietal junction in the social closeness condition. Finally, our exploratory analyses revealed that reward sensitivity and substance use moderate positively moderate VS connectivity with the right fusiform face area when winning in social context. These findings demonstrate that responsivity to social closeness may be tied to individual reward sensitivity or sub-clinical substance use habits; together these factors may inform predictions of risk for future mental health disorders.