Normal individuals who scored high on a measure of impulsive/antisocial traits display a hypersensitive brain reward system, according to a brain imaging study by researchers at Vanderbilt University. The findings provide the first evidence of differences in the brain's reward system that may underlie vulnerability to what's typically referred to as psychopathy.
The study in the current issue of the journal Nature Neuroscience was funded by the National Institute on Drug Abuse (NIDA), a component of the National Institutes of Health.
Psychopathy is a personality disorder characterized by a combination of superficial charm, manipulative and antisocial behavior, sensation-seeking and impulsivity, blunted empathy and punishment sensitivity, and shallow emotional experiences. Psychopathy is a particularly robust predictor of criminal behavior and recidivism.
Since psychopathic individuals are at increased risk for developing substance use problems, the Vanderbilt team decided to investigate possible links between the brain's reward system (activated by abused substances and natural reward), and a behavioral trait (impulsive/antisociality) characteristic of psychopathy. Researchers used two different technologies to measure the brain's reward response.
In the first experiment, positron emission tomography (PET) was used to image the brain's dopamine response in subjects who received a low oral dose of amphetamine. Dopamine is a brain chemical associated with reward and motivation.
In the second experiment, the same subjects participated in a game, in which they could make (or lose) money while their brains were being scanned using functional magnetic resonance imaging (fMRI) .
The results in both cases show that individuals who scored high on a personality assessment that teases out traits like egocentricity, manipulating others, and risk taking had a hypersensitive dopamine response system. The picture
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