Brain structure and function and social exclusion reactivity in the Cyberball game

Social exclusion or rejection is a universal stressor, and strong responses to rejection have been related to various mental health issues. Previous studies have shown that peer rejection and rejection reactivity are associated with concurrent activity in the insula, striatum, cingulate, parietal and prefrontal cortex. To date however, studies have only looked at peer rejection in relation to the state of the brain during rejection, not more stable brain characteristics. Identifying which brain areas are different among those that respond more to rejection could help us understand more of the biological underpinnings of those more sensitive to rejection and ultimately alleviate associated mental health issues. Here we studied how brain structure and resting state functional connectivity are related to rejection reactivity outside of the scanner, in a population-based sample of 1,814 9-to-12-year-olds. Observed emotional facial expressions and self-reported feelings during social exclusion were measured using the Cyberball paradigm, which took place outside of the MRI scanner. We assessed structural brain morphology using T1-weighted magnetic resonance imaging, white matter microstructure using diffusion tensor imaging, and functional connectivity using resting-state functional imaging. Stronger resting-state functional connectivity between the dorsal striatum, visual, and sensori-motor networks, and between the cingulo-operculum and dorsal attention network was positively related to negative emotional facial expressions during peer rejection. No associations were detected between functional connectivity and self-reported rejection reactivity, nor between gray or white matter (micro-)structure and observed or reported rejection reactivity. The dorsal striatum is related to automated behavior and the resting state functional connectivity between these and the other networks may indicate why some children are more expressive in their reaction to social exclusion. Moreover, the cingulo-operculum network overlaps with the insula and dorsal anterior cingulate cortex, areas related to pain processing. These findings are in line with earlier studies showing a neural substrate for feeling ‘hurt’ when socially excluded, and indicate specific resting-state functional connectivity related to increased risk of feeling hurt.