Brain mechanisms to regulate reactions to social exclusion

Social exclusion is an experience that most humans face daily. Social exclusion, especially when prolonged, can change the brain, undermine health, and reduce life expectancy. Mostly relevant to these negative outcomes, however, is how people respond to it. To date, one of the chief contributions of neuroscience to the understanding of social exclusion is that it is truly, and automatically, a painful experience. Nevertheless, social pain’s automatic components in the brainstem, anterior cingulate and insular cortices, are counterbalanced by the controlled, regulatory function of the prefrontal cortex. In particular, the right ventrolateral prefrontal cortex (VLPFC) is a brain region that appears to be critical for the regulation of social pain. The present set of experiments tests the hypothesis that modulating the cortical excitability of the right VLPFC may regulate emotional and behavioral responses to social exclusion. Participants received transcranical direct current stimulation (tDCS) over the right VLPFC in anodal, sham (Study 1 and 3) and cathodal (Study 2) modality. Five minutes before the end of the tDCS stimulation, participants were randomly assigned to a manipulation of inclusionary status (i.e., Cyberball). In Study 1 and 2, feelings of social pain and negative emotions were assessed. In Study 3, behavioral aggression was measured. In Study 1, we found that anodal tDCS over the right VLPFC decreased pain following social exclusion. In particular, anodal tDCS but not sham stimulation reduced pain unpleasantness and hurt feelings in excluded participants whereas no effects of tDCS stimulation emerged for included participants. In Study 2, we found that cathodal tDCS over rVLPFC leaded to reversed effects, increased feelings of social pain, hurt feelings, and negative emotions resulting from social exclusion. Crucially, in this study, cathodal stimulation was applied over a control region (the right posterior parietal cortex) and no effects on people’s emotional reactions caused by social exclusion were found. Finally, in Study 3, socially excluded participants given anodal stimulation were less aggressive than those given sham stimulation. Among socially included participants, no aggression differences emerged between the anodal and sham stimulation. Crucially, excluded participants who received anodal stimulation were no more aggressive than included participants. Overall, these studies suggest that the right vLPFC plays a key role in regulating responses to social exclusion and that it is possible to up-regulate and down-regulate reactions to social exclusion by modulating cortical activity of the right vLPFC. These modulatory findings fit well with the critical role of the vLPFC in self-regulation and inhibition of many other impulses such as gambling, substance abuse, and poor financial decisions.