Modulating interhemispheric prefrontal dynamics of aggressive behavior: sex differences and the association with personal disposition

A growing body of evidence has shown the key role of the dorsolateral prefrontal cortex (dlPFC) in aggressive behavior, along with the chance of modulating it by means of transcranial direct current stimulation (tDCS). However, the functional interplay between the two cerebral hemispheres in the regulation of aggressive behavior is still unclear. To address this issue, we assessed the effect of bi-hemispheric prefrontal tDCS in 76 healthy adults with a cross-over, double-blind, sham-controlled design. Half of the participants received the anodal stimulation over the right dlPFC and the cathodal stimulation over the left dlPFC (right anodal/left cathodal; Experiment 1), whereas the other half received the anodal stimulation over the left dlPFC and the cathodal stimulation over the right dlPFC (right cathodal/left anodal; Experiment 2). During tDCS, participants underwent the Point Subtraction Aggression Paradigm. All participants were also given self-report questionnaires measuring individual levels of aggression, impulsivity, and empathy to test whether these constructs were associated with the neuromodulation of aggressive responses at the Point Subtraction Aggression Paradigm. Results show a significant increase in aggressive reactions to provocation during right anodal/left cathodal prefrontal tDCS only within males, highlighting a sex-specific effect of the prefrontal neuromodulation that is also associated with individual levels of aggression. These findings provide a new insight into the brain mechanisms that regulate aggressiveness, their sex differences, and their association with dispositional aggressive tendencies.