Understanding and Preventing Violence, Volume 2: Biobehavioral Influences (1994)
Chapter: NEUROIMAGING APPROACH
some types of violent offenders has been provided by the measurement of psychophysiologic variables (i.e., assaying autonomic and CNS functions by means of recordings from the periphery of the body). Included among these variables are heart rate and skin conductance (autonomic nervous system variables), as well as EEG and event-related brain potentials (central nervous system variables). Differences among criminals, delinquents and conduct-disordered children on the one hand, and control subjects, on the other, have been shown to exist in resting heart rate (lower in offenders and in persons characterized as fearless) (Raine et al., 1990a; Raine and Jones, 1987; Venables and Raine, 1987; Kagan, 1989). Some offenders have also been shown to have lower skin conductance responses to orienting stimuli than controls, although the reverse may be true for criminal offenders designated as psychopathic (Siddle et al., 1973; Raine et al., 1990b).
With respect to EEG studies, many have reported an excess of slow wave activity in the records of incarcerated criminal offenders. It is unclear whether this is best interpreted as the effects of underarousal in the prison setting, developmental anomalies, or the sequela of brain damage (Williams, 1969; Hare, 1980).
Event-related brain potentials (ERPs), in particular the P300 component, have been studied in a number of disordered populations. The P300 wave, which is an index of the allocation of attention to a stimulus (Duncan, 1990), is an example of a "cognitive" component of the ERP. These components vary as a function of some information processing requirement or task administered to the subjects. The P300 has been found to be larger in some groups of psychopathic criminals (Raine and Venables, 1988). The interpretation of this finding is unclear, although it suggests that these persons process information differently from normal subjects.
NEUROIMAGING APPROACH
Perhaps the most recent technical development in research into the antecedents of violence involves the application of new brain imaging techniques. Positron emission tomography and regional cerebral blood flow (RCBF) techniques allow direct and indirect assessments of glucose metabolism (or blood flow in the case of RCBF) throughout the brain either during a resting state or during performance of a certain task. As such, PET and RCBF techniques assess brain function. Conversely, computerized tomography and magnetic resonance imaging (MRI) techniques, while providing detailed images, assess brain structure only.
