Differential neural and behavioural responses to social vs nonsocial rewards in adults

Description: Social rewards (e.g. smiles) powerfully shape human behaviour, starting from early childhood. Yet, the neural pathways involved in differential processing of social and non-social rewards remain poorly investigated. To address this gap in knowledge, social and nonsocial reward images matched on valence, arousal, and low-level stimulus properties were presented to 40 adults in a 3T fMRI study. We found greater activity in the amygdala, medial orbitofrontal cortex (mOFC) and right fusiform gyrus (rFG) in response to social than nonsocial rewards. Multi-voxel pattern analysis (MVPA) analysis corroborated these findings by demonstrating that activity in mOFC and rFG distinguishes between social and nonsocial stimuli with significantly greater than chance. Individual differences in the functional connectivity between these regions was inversely proportional to autistic traits. Reduced functional connectivity between these regions may contribute to the lower social reward responsivity in individuals with high autistic traits, as also noted from their lower valence ratings to social rewards. This study provides evidence for a new experimental paradigm to test social reward processing at a behavioural and neural level, and how individual differences therein can be investigated as one important dimension to quantify neurodiversity.