Vol. 3, No. 4, 1997 Page 7 
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Vol. 3, No. 4, 1997 Page 7 |
In 1995, Adrian Raine and colleagues reported the first results of their positron emission tomography (PET) studies of the brains of murderers found not guilty by reason of insanity (see related article, Crime Times, Vol. 1, No. 1/2, Pages 1&6). Comparing 22 murderers to 22 carefully matched control subjects, the researchers found that the murderers had much lower levels of glucose uptake in the prefrontal cortex.
Raine et al. have now expanded their study to include 41 murderers (39 men and 2 women), matched with 41 control subjects. "To our knowledge," they say, "this is the largest sample of violent offenders assessed on functional brain imaging." The researchers controlled for handedness, age, sex, ethnicity, and presence or absence of head injury. In addition, the six schizophrenic murderers were matched with six schizophrenic control subjects.
Again, the group of murderers showed reduced glucose metabolism in the prefrontal cortex. "Damage to this brain region," Raine et al. note, "can result in impulsivity, loss of self-control, immaturity, altered emotionality, and the inability to modify behavior, which can all in turn facilitate aggressive acts." Other abnormalities seen in the murderers included reduced glucose metabolism in the superior parietal gyrus, left angular gyrus, and the corpus callosum, and abnormal asymmetries of activity in the amygdala, thalamus, and medial temporal lobe. Defects of these brain areas, the researchers say, also have been linked to violence or to cognitive defects associated with criminality.
These results, the researchers say, "provide initial indications of a network of abnormal cortical and subcortical brain processes that may predispose to violence in murderers pleading not guilty by reason of insanity." The researchers do not believe the various mental disorders of the murderers distorted their findings, because, they say, "differences in brain functioning in murderers show a different pattern to that observed in other mental disorders." And although prefrontal dysfunction may be common to many mental disorders, Raine et al. say, the abnormalities they found in other brain areas "may lead to a pathway toward violence as opposed to other conditions."
"Brain abnormalities in murderers indicated by positron emission tomography," Adrian Raine, Monte Buchsbaum, and Lori LaCasse, Biological Psychiatry, Vol. 42, 1997, pp. 495-508. Address: Adrian Raine, Dept. of Psychology, S.G.M. Bldg., University of Southern California, Los Angeles, CA 90089-1061.