Psychopaths who kill and rape have faulty connections between the part of the brain dealing with emotions and that which handles impulses and decision-making, scientists have found.
In a study of psychopaths who had committed murder, manslaughter, multiple rape, strangulation and false imprisonment, the British scientists found that roads linking the two crucial brain areas had "potholes," while those of non-psychopaths were in good shape.
The study opens up the possibility of developing treatments for dangerous psychopaths in the future, said Dr Michael Craig of the Institute of Psychiatry at London's King's College Hospital, and may have profound implications for doctors, researchers and the criminal justice system.
"These were particular serious offenders with psychopathy and without any other mental illnesses," he told Reuters in an interview.
"Essentially what we found is that the connections in the psychopaths were not as good as the connections in the non-psychopaths. I would describe them as roads between the two areas — and we found that in the psychopaths, the roads had potholes and weren't very well maintained."
TIMING IS KEY
The scientists cautioned against suggestions the study could lead to screening of potential psychopathic criminals before they are able to commit crimes, saying their findings had not established how, when or why the brain links were damaged.
"The most exciting question now...is when do the potholes come — are people born with them, do they develop early in life, or are they a consequence of something else?"
Psychopathic extremes have been portrayed in Hollywood blockbusters by characters like the serial killer and cannibal Hannibal Lecter. Psychopaths often violate social norms, are manipulative, impulsive and sensation-seeking, and appear to feel no empathy or remorse.
Craig, who conducted the study, published in the journal Molecular Psychiatry with colleagues Declan Murphy and Dr Marco Catani, stressed that the numbers in brain scan study were small, with only nine psychopaths analyzed and compared with nine non-psychopaths.
"Trying to get people of this particular type to take part in a study, and also then deal with all the security you need to get them into a brain scanner, is not an easy feat," he said.
The study used a new brain imaging technology to further analyze psychopaths' brains after previous studies found that the amygdala part of the brain, which processes emotions, and orbitofrontal cortex, which handles impulses and decisions, are structurally and functionally different in psychopaths.
"Up until recently the technology hasn't been available to look at the connections between those two brain areas in any meaningful way," Craig said.
But a new technique, called diffusion tensor magnetic resonance imaging (DT-MRI), allowed the researchers to look at the white matter tract linking the two key brain areas.
As well as finding clear structural deficits in the tract in psychopathic brains, they also found the degree of abnormality was significantly linked to the degree of psychopathy.
"As for the moral significance for society, and how society wants to deal with these things, that is a little premature," said Craig. "This is a small study and the important thing it raises is that more research needs to be done."