A difference between the brains of psychopaths and ordinary people has been identified in a study that could promise new approaches to diagnosing and treating the disorder.

Research by British scientists using advanced brain-scanning techniques has revealed that a critical connection between two regions of the brain appears to be abnormal in psychopaths.

The findings are preliminary and do not show that brain anatomy causes psychopathy but 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.

The work is unlikely, however, 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. They rarely show remorse for their actions.

It is strongly associated with criminal behaviour and recidivism, and psychopaths are thought to make up about 15 per cent of the UK prison population. Criminals who are psychopaths commit 50 per cent more offences than those who do not have the disorder. The origins of the condition are unknown, though genetic and social explanations have been proposed. It is generally diagnosed through psychiatric assessment and questionnaires.

In the new research, 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 compared with those obtained for normal volunteers of a similar age and IQ. The results are published in the journal Molecular Psychiatry.

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.

Dr 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," Dr Craig said. "If it doesn't work, you could see how that could lead to problems."

Professor Murphy said the findings offered the most compelling evidence yet that altered brain anatomy might be involved in psychopathy.