The dopamine connection : learning likes and dislikes
For those who have wondered why they like or dislike certain things, or how they decide what to order from a menu, a team of researchers at the University of Colorado at Boulder says it's dopamine.
A CU-Boulder team studying Parkinson's disease patients found strong evidence that dopamine in the brain plays a key role in how people implicitly learn to make choices that lead to good outcomes, while avoiding bad ones.
Often people will 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 disease often have difficulty making these kinds of choices, Frank said.
To understand why, they developed a computer model of the effects of Parkinson's disease and the medications used to treat it in the brain. From this model they predicted that Parkinson's patients would differ in their decision making depending on whether or not they were taking their medication, which they confirmed in a subsequent study.
They found that patients on their medication were overly influenced by positive outcomes, while those who were off their medication were more influenced by negative outcomes, according to Frank.
"Because Parkinson's disease is caused by lower levels of the brain chemical 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.
Dopamine also plays a critical role in many other neurological conditions including attention deficit disorder, schizophrenia and drug addiction, so these findings may have broader implications, according to Frank. For example, by more precisely understanding the detailed effects of dopamine in the brain, drugs could be designed to more directly target beneficial actions, without as many unwanted side effects.
"This research clearly showed that current Parkinson's medications have undesirable side effects on learning and decision making," Frank said. Other researchers have documented a sudden onset of gambling episodes associated with patients taking these medications. These episodes may have been caused by the increased sensitivity to positive outcomes caused by the medications, together with an insensitivity to losses, he said.
"When experiencing a loss, dopamine levels are normally low in the brain, and the medication may prevent this from happening," Frank said.