Abnormal connections between brain regions
may contribute to psychopathic behavior

Psychopaths—people characterized by callousness, lack of empathy or remorse, shallow emotions, and manipulative behavior—make up much of the prison population and commit far more crimes than non-psychopathic criminals. Many studies hint that defects of the orbitofrontal cortex (OFC) play a role in psychopathic behavior, while other research implicates the amygdala. A new study, however, suggests that psychopathy may involve altered “connectivity” of a network that includes these two brain regions.

M. C. Craig and colleagues studied nine male psychopaths, all repeat violent offenders convicted of rape, attempted murder, or other serious crimes. Using diffusion tensor magnetic resonance imaging (DT-MRI), the researchers investigated the uncinate fasciculus (UF)—a band of fibers connecting the amygdala and orbitofrontal cortex.

The researchers say that compared to healthy male controls, the psychopaths showed evidence of reduced microstructural integrity in the UF. Within psychopaths, Craig and colleagues detected a correlation between measures of antisocial behavior and anatomical differences in the UF. Analysis of two tracts connecting other regions of the brain to the amygdala or OFC did not reveal similar anomalies.

To rule out the possibility that the findings stemmed from substance abuse, the researchers also compared the results from the psychopaths with results from a psychiatric control group with a history of drug and/or alcohol abuse and institutionalization. The psychopaths showed anomalies compared to this group as well.

The researchers say, “Taken together, our findings suggest that abnormal ‘connectivity’ in the amygdala-OFC limbic network may contribute to the neurobiological mechanisms underpinning the impulsive, antisocial behavior and emotional detachment associated with psychopathy.”

“Altered connections on the road to psychopathy,” M. C. Craig, M. Catani, Q. Deeley, R. Latham, E. Daly, R. Kanaan, M. Picchioni, P. K. McGuire, T. Fahy, and D. G. M. Murphy, Molecular Psychiatry, June 9, 2009 (epub prior to print publication). Address: m.craig@iop.kcl.ac.uk.