Dissociating prefrontal contribution to reactive and proactive aggression: a transcranial direct current stimulation study

Increasing evidence suggests that the dorsolateral prefrontal cortex (dlPFC) plays a crucial role in aggression and that it may be possible to modulate this behavior using transcranial direct current stimulation (tDCS). Nevertheless, no previous study has specifically examined the differential effects of bilateral tDCS on reactive and proactive aggression, making the present research the first to explore this distinction using neuromodulation. With this aim, we examined the effect of bi-hemispheric prefrontal tDCS in 30 healthy adults using a double-blind, sham-controlled design. All participants received three types of stimulation over the dlPFC: right anodal/left cathodal, right cathodal/left anodal, and sham tDCS. During the stimulation, participants underwent a modified version of the Taylor Aggression Paradigm, which included two different tasks: one for measuring proactive aggression (i.e., pTAP) and one for reactive aggression (i.e., rTAP). They were also given self-report questionnaires measuring individual levels of aggression, impulsivity, and empathy to test whether these constructs were associated with aggressive responses at the pTAP and rTAP. Results showed increased proactive aggression in males with both active montages, while reactive aggression increased only with right cathodal/left anodal tDCS. Females exhibited increased proactive aggression during right cathodal/left anodal tDCS, but decreased reactive aggression during right anodal/left cathodal stimulation. These findings suggest sex-dependent modulation of aggression via dlPFC stimulation. The relevance of these results extends beyond healthy individuals, as dlPFC dysfunction is a common feature in several psychiatric disorders associated with aggressive behavior. Understanding how tDCS modulates these distinct forms of aggression in healthy populations can inform future research on its therapeutic potential within clinical settings.