Psychopathic traits in normal individuals are associated with increased release of the neurotransmitter dopamine in response to pharmacological and monetary rewards. These results, published online this week in Nature Neuroscience, suggest that the impulsivity, antisocial behavior and substance abuse associated with psychopathy might be due to hyper-reactivity of the dopaminergic reward system.
Joshua Buckholtz and colleagues measured a range of psychopathic traits in a group of volunteers. They also measured dopamine release and brain activation in the nucleus accumbens ― an area where in animal studies has been linked to impulsive and aggressive traits of substance abuse. The scientists found that dopamine release in response to amphetamine administration was correlated with the individual scores on the impulsive-antisocial aspect of the trait scores. This score was also correlated with brain activation in anticipation of a monetary reward.
It has previously been suggested that psychopathy is a deficiency of emotion, with research emphasizing deficits in fear processing and empathy and the brain pathways thought to underlie these functions. These results suggest another important neural mechanism of the disease which may be particularly related to the problems of substance abuse that are associated with psychopathy.