A new study says that the brain wiring of psychopaths is quite different from that of ordinary people.
The finding by British scientists could promise new approaches to diagnosing and treating the disorder.
The scientists used advanced brain-scanning techniques, and revealed that a critical connection between two regions of the brain appears to be abnormal in psychopaths.
Although the findings are preliminary and do not show that brain anatomy causes psychopathy, they suggest a plausible biological explanation for the antisocial and amoral behaviour that characterises the condition.
If the link to brain wiring can be proved it would raise the prospect of using brain scans to help in diagnosing psychopaths, and provide insights with which to develop new therapies.
However, the work is unlikely to lead to a foolproof brain scan that can detect psychopaths and predict criminality.
The insights from scans are likely to be too unreliable for such uses for the foreseeable future, even should the ethical barriers be overcome.
Psychopathy is a disorder in which people struggle to control their impulses, and behave manipulatively, aggressively, dishonestly or exploitatively towards others.
Psycopaths rarely show remorse for their actions. It is strongly associated with criminal behaviour and recidivism.
In the new study, a team led by Professor Declan Murphy, Michael Craig and Marco Catani, of the Institute of Psychiatry at King's College, London, compared the brain anatomy of pscyhopaths to that of ordinary people using a new scanning technique called diffusion tensor magnetic resonance imaging (DT-MRI).
They recruited nine men who had been diagnosed as psychopaths, through mental health services, including people who had convictions for attempted murder, manslaughter, multiple rapes and false imprisonment. None was currently serving a prison sentence.
Their brains were scanned using DT-MRI, and the results were compared with those obtained for normal volunteers of a similar age and IQ.
The team found that a white-matter tract called the uncinate fasciculus (UF), which connects parts of the brain called the amygdala and the orbitofrontal cortex (OFC), differed significantly between the psychopaths and the control group.
People who had been diagnosed with more extreme psychopathy showed greater degrees of abnormality in this tract.
Craig said the results were interesting because of the function of the two brain regions connected by the UF.
The amygdala is involved in emotional responses such as fear, disgust and pleasure, while the OFC is involved in higher decision-making.
"There needs to be a connection between these two areas of the brain, which deal with emotions and the control of emotions. If it doesn't work, you could see how that could lead to problems," The Times Online quoted Craig as saying.
Murphy said the findings offered the most compelling evidence yet that altered brain anatomy might be involved in psychopathy.
The results have been reported in the journal Molecular Psychiatry.