REDUCED PREFRONTAL AND INCREASED SUBCORTICAL BRAIN FUNCTIONING ASSESSED USING POSITRON-EMISSION-TOMOGRAPHY IN PREDATORY AND AFFECTIVE MURDERERS

There appear to be no brain imaging studies investigating which brain mechanisms subserve affective, impulsive violence versus planned, pred atory violence. It was hypothesized that affectively violent offenders would have lower prefrontal activity; higher subcortical activity, an d reduced prefrontal/subcortical ratios relative to controls, while pr edatory violent offenders would show relatively normal brain functioni ng. Glucose metabolism was assessed using positron emission tomography in 41 comparisons, 15 predatory murderers, and nine affective murdere rs in left and right hemisphere prefrontal (medial and lateral) and su bcortical (amygdala, midbrain, hippocampus, and thalamus) regions. Aff ective murderers relative to comparisons had lower left and right pref rontal functioning, higher right hemisphere subcortical functioning, a nd lower right hemisphere prefrontal/subcortical ratios. In contrast, predatory murderers had prefrontal functioning that was more equivalen t to comparisons, while also having excessively high right subcortical activity. Results support the hypothesis that emotional, unplanned im pulsive murderers are less able to regulate and control aggressive imp ulses generated from subcortical structures due to deficient prefronta l regulation. It is hypothesized that excessive subcortical activity p redisposes to aggressive behaviour, but that while predatory murderers have sufficiently good prefrontal functioning to regulate these aggre ssive impulses, the affective murderers lack such prefrontal control o ver emotion regulation. (C) 1998 John Wiley & Sons, Ltd.