Follow your heart? Examining heart rate variability as a predictor of neural reactivity to social rejection - A network approach to individual differences in social threat sensitivity

Frontal midline (FM) theta (4–8 Hz) reactivity to unexpected social rejection seems to be an important correlate of a neural threat-detection system. Neurovisceral integration theory proposes that the functioning of such systems is indexed by heart rate variability (HRV). Here, we tested this by examining whether baseline HRV predicts FM-theta reactivity to unexpected rejection feedback. Additionally, we examined whether this alleged heart-brain connection differs based on individual differences in personality and behavioral constructs relevant to social threat sensitivity. Female undergraduates (n = 149; mean age = 19.7 years) performed the social-judgment paradigm, where they communicated their expectations about being liked/disliked by unfamiliar peers who had allegedly evaluated them, and received peer-feedback indicating social acceptance/rejection. We used community structure analysis to subtract subgroups, based on self-esteem, social feedback expectations, and response speed of providing expectations. Results provided evidence of two distinct subgroups: optimistic vs. pessimistic in light of social threat. Baseline HRV did not predict FM-theta reactivity to unexpected rejection, and this relationship was not modulated by the subgroups. Both subgroups showed a significant FM-theta power increase following unexpected rejection. Additionally, the optimistic subgroup was uniquely characterized by a FM-theta power increase following rejection (as against acceptance) feedback. Supporting prior studies, our results suggest that enhanced FM-theta signals the need for cognitive control when faced with unexpected outcomes, and extend this by suggesting that differences in social threat sensitivity may determine whether an outcome is deemed meaningful enough to signal the need for cognitive control.