Here's some info:
Neuroscience is beginning to open the hood on psychopathy. The scientist-author of this article has spent the last 15 years imaging the brains of psychopaths in prison, and has accumulated the world’s largest forensic database on the psychopathic brain. The findings from this data and others, summarized in Part IV, strongly suggest that all psychopaths share common neurological traits that are becoming relatively easy to diagnose using functional magnetic resonance imaging (fMRI).
Here are some of the results/conclusions:
What does all this mean? First, it suggests that the story of psychopathy is largely limbic and paralimbic rather than prefrontal. This dovetails nicely with the central paradox of the psychopath: he is completely rational but morally insane. He is missing the moral core, a core that appears intimately involved with the paralimbic regions. If the key to psychopathy lies in these lower regions, then it is no mystery that the psychopath is able to recruit his higher functions to navigate the world. In fact, when he gives a moral response, it seems the psychopath must recruit frontal areas to mimic his dysfunctional paralimbic areas. That is, the psychopath must think about right and wrong while the rest of us feel it. He knows morality’s words but not its music.
Second, these neurological results should go a long way toward ending the debate about whether psychopathy is just too difficult to diagnose to justify inclusion in the DSM. Any lingering doubts about the clinical reliability of the Hare instruments disappear now that those instruments have been shown to be robustly predictive of a demonstrable neurological condition.