Neuroscientists have known for many years that the neurotransmitter dopamine plays a major role in drug addiction.
More recently, scientists have discovered that dopamine also plays a big part in basic risk-taking behavior.
For example, Time wrote in 2007:
In 2008, Time noted:Everyone can learn from their mistakes -- but some people have genes that may make it harder. That's the message from German researchers, writing in tomorrow's issue of the journal Science, who have shown how a common gene variant affects some people's ability to respond to, and learn from, the negative repercussions of their actions...
Those men, it turns out, had a particular gene variant, or allele, that reduces the density of receptors for dopamine -- a neurotransmitter that plays a key role in motivation, pleasure and addiction -- in certain areas of the brain...
It's the first strong physiological evidence that the density of dopamine receptors may affect how people respond to negative inputs. Previous studies have established a strong link between a low density of dopamine receptors and addiction, obesity and compulsive gambling -- conditions that suggest an impaired ability to learn from the consequences of bad decisions.
A new study by researchers at Vanderbilt University in Nashville and Albert Einstein College of Medicine in New York City suggests a biological explanation for why certain people tend to live life on the edge -- it involves the neurotransmitter dopamine, the brain's feel-good chemical...Dopamine is responsible for making us feel satisfied after a filling meal, happy when our favorite football team wins, or really happy when we use stimulating drugs like amphetamines or cocaine, which can artificially squeeze more dopamine out of the nerve cells in our brain. It's also responsible for the high we feel when we do something daring, like skiing down a double black diamond slope or skydiving out of a plane. In the risk taker's brain, researchers report in the Journal of Neuroscience, there appear to be fewer dopamine-inhibiting receptors -- meaning that daredevils' brains are more saturated with the chemical, predisposing them to keep taking risks and chasing the next high: driving too fast, drinking too much, overspending or even taking drugs.
David Zald, a professor of psychology and psychiatry at Vanderbilt, studied whether the brains of those thrill seekers differed in any way from those of the less adventuresome when it comes to dopamine. He gave 34 men and women a questionnaire to assess their novelty-seeking tendencies, then scanned their brains using a technique called positron emission tomography to figure out how many dopamine receptors the participants had. Zald and his team were on the lookout for a particular dopamine-regulating receptor, which monitors levels of the neurotransmitter and signals brain cells to stop churning it out when there's enough.
Earlier studies in rats had shown that animals that tend to explore and take more risks in new environments also tend to have fewer of these inhibitory receptors, and Zald wanted to find out if the same was true in people.
"This is one of those situations where the data came out essentially perfectly," he says. "The results were exactly as we predicted they would be, based on the animal data." That is, like the rats, humans who were more spontaneous and eager to take risks had fewer dopamine-regulating receptors than those who were more cautious.
The findings support Zald's theory that people who take risks get an unusually big hit of dopamine each time they have a novel experience, because their brains are not able to inhibit the neurotransmitter adequately. That blast makes them feel good, so they keep returning for the rush from similarly risky or new behaviors, just like the addict seeking the next high.
"This finding is really interesting," says Dr. Bruce Cohen, director of the Frazier Research Institute at McLean Hospital in Boston and a professor of psychiatry at Harvard Medical School. "It's a piece of the puzzle to understanding why we like novelty, and why we get addicted to substances ... Dopamine is an important piece of reward."
As PhysOrg writes:
Abnormalities in how the nucleus accumbens, highlighted here, processes dopamine have been found in individuals with psychopathic traits and may be linked to violent, criminal behavior. Credit: Gregory R.Samanez-Larkin and Joshua W. BuckholtzThe brains of psychopaths appear to be wired to keep seeking a reward at any cost, new research from Vanderbilt University finds. The research uncovers the role of the brain's reward system in psychopathy and opens a new area of study for understanding what drives these individuals.
"This study underscores the importance of neurological research as it relates to behavior," Dr. Francis S. Collins, director of the National Institutes of Health, said. "The findings may help us find new ways to intervene before a personality trait becomes antisocial behavior."
The results were published March 14, 2010, in Nature Neuroscience.
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