Orbitofrontal cortex reactivity to angry facial expression in a social interaction correlates with aggressive behavior

Altered neural processing of social signals such as angry facial expressions has been associated with increased aggressive behavior, but evidence for this relationship in healthy persons using ecologically valid experimental designs is lacking. We presented socially relevant videos of facial expressions in a functional magnetic resonance imaging (fMRI) version of the well-established Taylor Aggression Paradigm and investigated 41 healthy male participants, of whom 32 were included in the analysis. In each round of this competitive reaction time task, participants observed their opponent while he selected a punishment level for him, bearing either a neutral or angry facial expression. Afterward, participants in turn selected a punishment level for their opponent. Across participants, reactivity of the medial orbitofrontal cortex (OFC) to angry facial expressions was negatively related to aggressive behavior. Within participants and across trials, activity in the anterior cingulate cortex (ACC) was positively related to aggressive behavior specifically in response to angry expressions. Moreover, we found an effect of angry expressions on neural activity patterns during later stages of the task, demonstrating that the effect of angry expressions on neural reactivity is more than just a short-lived, stimulus-driven response. Our results underscore the importance of OFC and ACC for the shaping of socially adaptive responses to provocation.