In a clear example of how psychology and medicine interact, a new study of Parkinson’s disease shows the powerful effect of expectation on the brain. In the study, participants’ learning-related brain activity responded as well to a placebo as it did to real medication.
Researchers from the University of Colorado at Boulder (CU-Boulder) and Columbia University, New York, NY, report their findings in the journal Nature Neuroscience.
Previous studies have suggested that the brain systems affected by Parkinson’s disease can respond to patients’ expectations about treatment.
Study co-author Tor Wager, an associate professor of psychology and neuroscience at CU-Boulder, says the study “highlights important links between psychology and medicine.”
Parkinson’s disease is a motor disorder that occurs when the brain loses cells that produce dopamine – a brain chemical that helps control reward and pleasure and also regulates movement and emotional responses.
The disease has four main symptoms: trembling in the hands, limbs, jaw and face; stiffness of the trunk and limbs; slowness of movement; and problems with balance and coordination. The symptoms of Parkinson’s disease, which rarely strike before the age of 50, gradually worsen to the point where doing normal everyday things like, walking, talking, eating and taking care of oneself becomes very difficult.
Research shows that people with Parkinson’s struggle with “reward learning,” and find it difficult to make motivated decisions to seek positive outcomes. Reward learning depends on brain cells that secrete dopamine in response to rewarded actions – such as when pressing buttons leads to receiving money.
In Parkinson’s disease, patients are given the dopamine-boosting drug L-dopa to compensate for the loss of dopamine-producing brain cells.
In their study, Prof. Wager and colleagues invited 18 Parkinson’s patients to play a computer game while they took functional magnetic resonance imaging (fMRI) scans of their brains.
The computer game measured reward learning by getting the participants – through trial and error – to discover which of two symbols was more likely to result in a better outcome. There were two types of outcome: a small reward of money or avoiding the loss of money.
As the researchers took scans of their brains, the participants played the game three times. One time was with neither placebo nor medication, another time they took orange juice containing medication, and they also played the game when they took orange juice containing placebo.
On the times when they played the game and took the orange juice, the patients did not know whether it contained the real medication or a placebo.
When they compared the game results with the brain scan data, the researchers found the the striatum and the ventromedial prefrontal cortex – dopamine-rich areas of the brain associated with reward learning – were just as active when the participants played the game under the influence of the placebo as when they were under the influence of the active drug.
Prof. Wager says the results show there is a link between brain dopamine, expectation and learning and:
“Recognizing that expectation and positive emotions matter has the potential to improve the quality of life for Parkinson’s patients, and may also offer clues to how placebos may be effective in treating other types of diseases.”
Funds for the study came from the Michael J. Fox Foundation for Parkinson’s Research.
Estimates suggest there are 6.3 million people worldwide of all races and cultures with Parkinson’s disease, which tends to affect men slightly more than women.
Medical News Today recently reported a new study that followed thousands of people for 12 years and found medium daily exercise is linked to a lower risk of Parkinson’s disease.