In a recent paper in Nature Neuroscience, two researchers at the Scripps Research Institute in Florida report that obese rats with extended access to what they deemed “palatable food” — bacon, sausage, cheesecake, pound cake, frosting and chocolate — exhibited compulsive like eating behavior, much like rats with extended access to cocaine or heroin . This compulsive eating meant that they continued eating despite negative ramifications, in this case a flash of light signaling an oncoming electric shock administered to their foot. This lack of control over behavior with known negative consequences is a hallmark of both drug addiction and obesity. The investigators found that just like drug addicted rats, these obese rats had fewer striatal (a region of the forebrain) dopamine D2 receptors; this is responsible for the observed dampening of their neural reward responses to the food, which caused them to continue to eat, seeking that elusive high.
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.