Michael Torrice in Science:
Whether it involves gambling away one's life savings or committing one murder after another, a psychopath inevitably leaves the rest of us wondering: What was going on in his head? Now researchers report that part of the answer may be hypersensitivity to rewards, which may create a pathological drive for money, sex, and status.
All psychopaths share two characteristic traits: an inability to empathize with others' emotions, such as the fear in a person's face, and impulsive, anti-social behavior, such as reckless risk taking or excessive aggression. Neuroscientists have pinpointed neural mechanisms that may cause psychopaths' lack of empathy. But very little research has looked at what leads to impulsivity-which in some ways might be more important, because it can help predict a psychopath's tendency towards violent crime.
Neuroscientist Joshua Buckholtz of Vanderbilt University in Nashville and his colleagues decided to focus on a system of interconnected brain regions called the mesolimbic system, which motivate us to hunt for rewards by releasing the neurotransmitter dopamine. Drugs like heroine-to which psychopaths are also more susceptible—can push circuits in this system into overdrive, leaving addicts compulsively seeking another hit. The researchers hypothesized that psychopaths might also overreact to other rewards.
To test their hypothesis, the scientists studied how normal personality is affected by variations in the nucleus accumbens, a part of the mesolimbic system involved in motivation.
More here.