Structural brain characteristics associated with appetitive aggression in martial artists

Introduction Perception and practice of violence have hedonistic aspects that are associated with positive arousal (appetitive aggression). Earlier studies have primarily investigated the etiology of aggressive behavior in forensic and psychiatric samples. To deal with possible confounds (e.g. hospitalization, co-morbidities), the present study examined structural brain characteristics in healthy people inclined to violence (martial artists) in comparison to healthy controls not showing violent behavior.

Methods In an age-matched, healthy and male sample of 26 martial artists and 26 control subjects we measured different aggression parameters using a self-assessment test battery. All participants underwent structural T1-weighted Magnetic Resonance Imaging (MRI). Grey matter (GM) differences were analyzed with voxel-based morphometry using SPM12 and CAT12.

Results On whole brain level, martial artists compared to control subjects showed an increased mean GM concentration in four different clusters comprising the left superior frontal and middle gyrus, the left medial frontal cortex, the left anterior cingulate gyrus as well as the superior occipital gyrus (p < .001, uncorr.). Brain characteristics in two of these clusters were positively associated with appetitive aggression (r = .308*, p < .05; r = .351*, p < .05).

Conclusion The present study shows structural brain characteristics associated with aggression. A lateralization effect for the left hemisphere becomes evident. In contrast to earlier studies, confounds evoked by the presence of a psychiatric disorder or an incarceration were controlled. Further analyses of differences in the cortical thickness are planned.