The findings are thought to be the first of their kind and could possibly lead to the development of better treatment methods for people with this personality disorder. Psychopathy includes traits such as callousness, manipulation, sensation-seeking and antisocial behaviors.
Psychopathy affects 20 percent to 30 percent of men and women in U.S. prisons, compared with about 1 percent of the general population. Psychopaths are responsible for a disproportionate amount of repeat crime and violence.
The study included 80 prisoners, aged 18 to 50, in a U.S. correctional facility who were assessed for levels of psychopathy. The researchers then used functional MRI to monitor the prisoners' brain activity in response to depictions of people being intentionally hurt and facial expression showing pain.
Prisoners who had high levels of psychopathy had lower-than-normal activation in areas of the brain including the amygdala, which plays an important role in feeling concern for and valuing the well-being of other people, according to the study, which was published online April 24 in the journal JAMA Psychiatry.
"A marked lack of empathy is a hallmark characteristic of individuals with psychopathy," study lead author Jean Decety, a professor of psychology and psychiatry at the University of Chicago, said in a university news release.
Decety is an expert on the biological basis of empathy.
"This is the first time that neural processes associated with empathic processing have been directly examined in individuals with psychopathy, especially in response to the perception of other people in pain or distress," he said.