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PET STUDY: LOOKING INSIDE THE MINDS OF MURDERERS
What stops us from killing an irritating neighbor, a disloyal friend, or a total stranger with a pair of
shoes we'd like to own? Or -- to rephrase the question -- what fails to stop some people from
committing such murders?
The answer may lie, at least in part, in our frontal lobes. Much of the behavior that makes us
"civilized"-self-control, maturity, judgment, tactfulness, reasoning-is regulated by this area of
the brain. But new research suggests that a specific region of the frontal lobes, the prefrontal
cortex, may function very differently in murderers than in the rest of us.
PET (positron emission tomography) measures the uptake of glucose, the "fuel" of the brain, by
different brain areas. In a preliminary study, Adrian Raine and colleagues used PET to study
differences between 22 murderers (or individuals who had unsuccessfully attempted to commit
murders) and 22 carefully matched control subjects during cognitive testing.
The researchers found that the murderers had much lower levels of glucose uptake in the prefrontal
cortex than controls. The differences were not related to age, gender, handedness, ethnicity,
motivation, history of head injury, or presence of schizophrenia. In addition, no subjects were
taking psychoactive drugs at the time of the test.
Their data, Raine and his colleagues say, strongly suggest that "deficits localized to the prefrontal
cortex may be related to violence" in some offenders. They note that "frontal damage is associated
with impulsivity, loss of self-control, immaturity, lack of tact, inability to modify and inhibit
behavior appropriately, and poor social judgment."
The researchers suggest that prefrontal cortex dysfunction may interact with environmental, social,
and psychological influences, leading to criminal behavior. For instance, they note, such
dysfunction may result in school failure, unemployment, and poverty, "thereby predisposing to a
criminal and violent way of life."
Raine et al. caution that their findings are preliminary, and that the defects they found could be
linked to psychoactive drug use, hyperactivity, epilepsy, or organic brain disorder, all of which are
common in violent criminals. They note, however, that "it is not easy to see how such
heterogeneous conditions... could systematically result in the selective prefrontal deficit observed."
See also Crime Times, Vol. 1, No. 1/2, Page 4.
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"Selective reductions in prefrontal glucose metabolism in murderers," Adrian Raine, Monte S.
Buchsbaum, Jill Stanley, Steven Lottenberg, Leonard Abel, and Jacqueline Stoddard, Biol.
Psychiatry, 36, September 1, 1994. Address: Adrian Raine, Department of Psychology, S.G.M.
Building, University of Southern California, Los Angeles, CA 90089-1061.
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