Parkinson's Patients Show Brain Response to Placebo

In patients with Parkinson’s disease, learning-related brain activity improves just as much with placebo as real treatment, according to a new study published in Nature Neuroscience.

Researchers from the University of Colorado Boulder and Columbia University found that the dopamine-rich areas of the brain governing the ability to associate actions with rewards—which is typically impaired by the neurological disorder—are equally active whether an individual with Parkinson’s disease receives medication or placebo.

"This finding demonstrates a link between brain dopamine, expectation, and learning," said study co-author Tor Wager, PhD, in a press release. "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."

For their study, Dr. Wager and his co-authors used functional magnetic resonance imaging to examine the brains of 18 Parkinson’s patients as they played a computer game that monitored reward learning. All subjects played the game 3 times: once when they were not taking any medication, when they took real medication, and when they took a placebo.

“We found that the mere expectation of dopamine release enhanced reward learning and modulated learning-related signals in the striatum and the ventromedial prefrontal cortex. These effects were selective to learning from reward: neither medication nor placebo had an effect on learning to avoid monetary loss,” the authors wrote. “These findings suggest a neurobiological mechanism by which expectations shape learning.”

The study was funded by the Michael J. Fox Foundation for Parkinson's Research.