Frontal lobe asymmetry and impulsive aggression : a reinforcement sensitivity study.

The current study compared impulsive aggressive individuals and nonaggressive controls using frontal cortical EEG activity. Impulsive aggression is a reactive or emotionally charged violent response characterized by a loss of behavioral control. Previous physiological studies have found impulsive aggressors (IAs) have sensory and informational processing deficits. Undergraduate male volunteers (n = 15 IAs, n = 15 controls) completed a resting EEG and two affective picture tasks intended to manipulate emotional state. IAs showed more right frontal cortical activity than controls at lateral frontal electrodes at rest [t(28) = 2.470, p = .020] and had similar asymmetry indices throughout the two emotional paradigms [t(14) = .890, ns]. Controls, however, were able to engage the Behavioral Inhibition System (BIS) during withdrawal-related stimuli [t(14) = 2.576, p = .022]. An interaction between group and picture task [F(2, 14) = 3.818, p = .028] reinforced this result. Results indicated that IAs have an overactive BIS and thus cannot appropriate the proper biological systems in response to emotional stimuli. Future directions are discussed.