Frontal alpha asymmetry and callous-unemotional traits in imprisoned violent offenders: A pilot study.

Based on the approach-withdrawal model of hemispheric asymmetry, anger and aggression have been linked to an approach-related pattern, characterized by stronger relative left-hemispheric anterior cortical activity. Recent work suggests that also in individuals with extremely violent tendencies, such as imprisoned offenders, approach-related asymmetry may be associated with self-reported trait anger and aggression. A putative association between alpha asymmetry and further characteristics relevant for aggression, such as callous-unemotional (CU) traits, remains to be explored. CU traits may increase the probability of aggressive behavior; nevertheless, they may also enable individuals to inhibit and postpone the overt display of aggression until circumstances grant its strongest impact. In the current exploratory study, we measured trait aggression, CU traits, and resting-state EEG asymmetry in the alpha band (8-13 Hz) in imprisoned violent offenders in a German high security prison. Results revealed that particularly trait callousness was associated with stronger relative right-hemispheric anterior cortical activity (i.e., a withdrawal-related pattern). An association between alpha asymmetry and aggression was not replicated. These preliminary findings suggest that, due to the involved emotional and interpersonal detachment, callousness might be withdrawal related, despite its potential to bring about aggressive behavior. They also imply that the identification of putative clinical subtypes in prisoners is required, as varying psychopathology might undermine an association between alpha asymmetry and aggression.