Clues to Criminal Mind Found in Prefontal Cortex

Not all criminal brains are created equal, a new study suggests. The study, published in the May 15 Biological Psychiatry, was conducted by Adrian Raine, Ph.D., a professor of psychology at the University of Southern California, and colleagues. Raine is an international authority on the psychophysiology of criminals.

During the past few years, evidence has been building that the prefrontal cortex—a region involved in judgment, planning, and decision making—is often not the same in criminals and potential criminals as in the general population.

In 2000, for example, Raine and coworkers reported that the prefrontal cortex of violent, antisocial men was smaller than that of controls (Psychiatric News, March 3, 2000). In 2002, two University of Connecticut scientists reported that brain-wave responses to a memory task were less potent in the prefrontal cortex of teens with conduct disorder than in the prefrontal cortex of teens without the disorder (Psychiatric News, April 5, 2002).

But how might the prefrontal cortex of successful criminals (those who avoid capture) compare with that of unsuccessful criminals (those who get caught)?

Raine and his team used five temporary employment agencies in Los Angeles to recruit volunteers for their study. They gave the volunteers various tests including the Psychopathy Checklist–Revised, Structured Clinical Interview for the DSM-IV Mental Disorders (SCID I), and SCID Axis II Personality Disorders (SCID II) to determine whether they had psychopathic characteristics and, if so, to what degree. The researchers also determined whether subjects had committed any crimes by examining state court records and by asking subjects directly whether they had committed any offenses. To minimize the chance that subjects would not admit to having committed crimes, the investigators assured them that any admission they made would be confidential. The scientists were able to do so because they had obtained a certificate of confidentiality from the secretary of Health and Human Services.

The researchers used the test results and crime information to compose a study sample of 52 subjects—13 with high psychopathy scores who had escaped detection for their crimes, 16 with high psychopathy scores who had been detected and convicted for their criminal acts, and 23 control subjects.

The scientists then used structural magnetic resonance imaging (MRI) to determine the volume of prefrontal gray matter in each of the subjects. They found that the volume of prefrontal gray matter in the unsuccessful psychopaths was 22 percent smaller than in the control subjects—a highly significant difference. The volume of prefrontal gray matter was a little smaller in the successful psychopaths than in the control subjects, but the difference was not significant.

These results remained the same even when possibly confounding factors such as age, socioeconomic status, substance abuse, or a history of head injury were taken into consideration.

Although Raine and his team are not sure how to interpret these findings, they propose a possible explanation in their study report: “In contrast to unsuccessful psychopaths, successful psychopaths show a relative sparing of prefrontal gray matter. Relatively intact prefrontal structure may provide successful psychopaths with both the cognitive resources to successfully manipulate and con others as well as sufficiently good decision-making skills in risky situations to avoid legal detection and capture.

“In contrast, prefrontal structural deficits may render unsuccessful psychopaths particularly susceptible to poor decision making; interpersonally inappropriate, impulsive, disinhibited, unregulated, reward-driven antisocial behavior; and reduced sensitivity to environmental cues signaling danger and capture.”

The study was funded by the National Institute of Mental Health and the Wacker Foundation.

An abstract of “Volume Reduction in Prefrontal Gray Matter in Unsuccessful Criminal Psychopaths” is posted online at<www.journals.elsevierhealth.com/periodicals/bps/article/PIIS0006322305000983/abstract>.▪