Psychopaths often violate social norms, are manipulative, impulsive and sensation-seeking and appear to feel no empathy or remorse. Previous studies have found that the amygdala - a part of the brain that processes emotions - and the orbitofrontal cortex (which handles impulses and decision-making) are structurally and functionally different in psychopaths. Researchers from the Institute of Psychiatry in London used brain-scanning technology to compare the brains of nine criminal psychopaths (who had been convicted of a variety of offences including murder and rape) with nine normal, law-abiding people. They found that the connections between the amygdala and the orbitofrontal cortex were much weaker in the psychopaths. It is not known whether the brain differences are present from birth or whether they develop throughout the psychopaths' lives. More studies are needed but the psychopaths are not the most amenable of participants in research.

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http://uk.reuters.com/article/idUKTRE5764NI20090810?feedType=RSS&feedName=healthNews&sp=true