The same reward system in the brain that hooks people to drugs might also explain why some people act like psychopaths.
We know that cold-blooded criminals lack empathy and fear — and are, by societal standards, a bit odd. But new research shows that it is not the traits that psychopaths lack that make them behave badly, it's the traits that they do have. Not only are psychopaths impulsive, they like to take risks and seek out rewards.
So-called psychopathic traits have been linked to a disruption in the dopamine reward circuitry in the brain. And it is this disruption that drives psychopaths to want money, sex, or fame, in extreme ways.
Why do you want to unravel the brains of psychopaths?
Crime is expensive. Understanding what goes on in the brain of a psychopath is a very social and scientific question.
In the last 10 years, we've come to understand a great deal more about the brain regions involved in predisposing individuals to psychopathy. They lack fear, have a deficit of empathy, and have a disregard for others. But those aren't the best predictors of criminality in a psychopath.
We know that psychopaths have these impulsive, anti-social traits and have socially devious behavior. But we don't know a lot about the brain circuitry involved in those psychopathic traits.
But you didn't actually use psychopaths in your study did you?
The point of the study was to understand the circuitry, which are strongly tied to risky criminal behavior. We used community volunteers. Psychopathy operates along a continuum and incarcerated criminals are at the far end of that spectrum. None of the subjects in the study would meet the criteria for psychopathy.
Why are psychopaths anti-social?
That's the core question: Why do they exhibit profound levels of profound antisocial behavior? They have a hyper-reactive dopamine reward system.
So tell me what happened in the study.
First, we got a sample of these community volunteers. Then we measured their psychopathic inventory by giving them a personality test to measure psychopathic traits [ranging from manipulativeness, egocentricity, aggression and risk taking].
We gave them speed. And used positron emission tomography, or PET, to measure dopamine levels in the brain. And we used a functional magnetic imaging, or fMRI, to image brain activity [to measure the brain reward system], while they were preforming a task.
We gave them an opportunity to win money. We looked to see if people with increased psychopathic traits had increased dopamine levels after we gave them speed. We wanted to see if they showed increased brain activity when they had the opportunity to earn money. It ranged from 20 cents to $5. And yes, they got to keep the money.
The people who scored higher on the measure of psychopathic traits, showed higher dopamine levels in brain reward regions after we gave them the drug. And they also showed greater activity when they had an opportunity to win the task. We know amphetamines cause dopamine levels to rise.
We'd like to do a study of incarcerated psychopaths to see if they show similar brain patterns.
Image at bottom: Josh Buckholtz/Vanderbilt University
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