STUDY Dopamine leads to good choices

The chemical also plays a role in drug addiction.
SCRIPPS HOWARD
Researchers have found that the brain chemical dopamine is a critical ingredient in helping people make choices that lead to good outcomes while avoiding those with negative consequences.
The finding by a team at the University of Colorado at Boulder expands understanding of how the brain works and could lead to better treatments for brain disorders such as schizophrenia and attention-deficit disorder. The results were published online by the journal Science.
The study, led by graduate student Michael Frank, grew out of evaluations on Parkinson's-disease patients when they were taking medications that boost dopamine production in the brain and when they were off the medicines.
Brain disease
Parkinson's, a degenerative brain disease known for restricting movement and causing muscle rigidity and tremors, also affects mental performance, but not always negatively. Patients with the disease do worse on cognitive tasks that require learning from both positive and negative feedback -- the carrot and the stick, as the researchers put it.
They learn better in tasks that rely only on the stick, or negative reinforcement. But when they're on medications that boost dopamine, their decision-making is overly influenced by the prospect of positive outcomes.
Healthy people often get a "gut feeling" that allows them to make a choice depending on how often it was associated with positive outcomes in the past. But people with Parkinson's often have difficulty making these kinds of choices, Frank explained.
"Because Parkinson's disease is caused by lower levels of dopamine, and the medications increase concentrations of this chemical, these results provide strong evidence that dopamine levels play a critical role in developing our likes and dislikes," Frank said.
Drug addiction
Dopamine also plays a role in other neurological conditions, including drug addiction, and the research also helps understand brain function overall, said Randall O'Reilly, an associate professor of psychology at the university who took part in the study.
"Studying Parkinson's patients helps us to understand how healthy people learn, showing us what's going on under the hood," O'Reilly said. "It's kind of like when your car makes a funny noise and you discover how the fan belt works. In this case, we looked at a disease that has showed us more about dopamine's role in the learning system of the brain."
Frank said that with more precise understanding of the effects of dopamine on the brain, it might be possible to design drugs that more directly target beneficial actions without as many unwanted side effects on learning and decision-making.