Feeling left out or just surprised? Neural correlates of social exclusion and over-inclusion in adolescence

Abstract Social belonging is an important human drive that influences mood and behavior. Neural responses to social exclusion are well-characterized, but the specificity of these responses to processing rejection-related affective distress is unknown. The present study compares neural responses to exclusion and over-inclusion, a condition that similarly violates fairness expectations but does not involve rejection, with a focus on implications for models of dorsal anterior cingulate cortex (dACC) and anterior insula (AI) function. In an fMRI adaptation of the Cyberball paradigm with adolescents 11.1-17.7 years of age (N=69), we employed parametric modulators to examine scaling of neural signal with cumulative exclusion and inclusion events, an approach that overcomes arbitrary definitions of condition onsets/offsets imposed on fluid, continuous gameplay. We identified positive scaling of dACC and posterior insula response with cumulative exclusion events, but these same regions exhibited trending signal decreases with cumulative inclusion events. Furthermore, areas within the dACC and insula also responded to context incongruency (throws to the participant in the exclusion run; throws between computer players in the over-inclusion run). Taken together, these findings caution against interpretations that responses in these regions uniquely reflect aspects of affective distress within social rejection paradigms. We further identified that the left ventrolateral PFC, rostromedial PFC, and left intraparietal sulcus responded similarly to cumulative exclusion and inclusion. These findings shed light on which neural regions exhibit patterns of differential sensitivity to exclusion or over-inclusion, as well as those that are more broadly engaged by both types of social interaction.