Parkinson’s disease alters ability to learn from rewards

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Parkinson’s disease alters patient’s ability to learn from rewards while treatment affects ability to learn from negative outcome — research reveals possible link to depression, impulse control disorders.

Once viewed primarily as a motor disorder, Parkinson’s disease also disrupts learning and memory. These impairments may be partially caused by medications used to treat the motor symptoms.

A new neuropsychological memory test is helping to uncover how Parkinson’s disease can alter people’s ability to learn about the consequences of the choices they make. The test was developed by Dr. Mark Gluck, professor of neuroscience at the Center for Molecular and Behavioral Neuroscience at Rutgers University, Newark, working with co-researchers at Rutgers, New York University, and in Hungary.

As reported in a forthcoming article in the journal Brain, Gluck and co-researchers Nikoletta Bodi and Szabolcs Keri of Semmelweis University, Hungary, found that non-medicated patients in the early stages of Parkinson’s were selectively impaired at learning from reward.

Patients in Hungary were tested using a novel feedback-learning task developed by Gluck and his colleagues: Catherine E. Myers, research professor, Rutgers University, Newark; and Nathaniel Daw, assistant professor, New York University.

The research was supported by a Dekker Foundation Award from the Bachman-Strauss Dystonia and Parkinson Foundation.

“What we are seeing in recently diagnosed patients is that prior to being put on any medications, they exhibit a selective impairment in their ability to learn from positive (rewarding) outcomes while their sensitivity to learning from negative (or punishing) outcomes is normal,” says Gluck, director of Rutgers’ Center for Collaborative Research on Cognition and Parkinson’s Disease.

This selective deficit in learning from reward is not surprising, says Gluck, because scientists have long known that dopamine is used to carry reward information throughout the brain. Parkinson’s patients, however, have lost most of their dopamine-producing cells by the time they are first diagnosed with the disease. This decrease in their ability to process rewarding outcomes could be one reason why many Parkinson’s patients experience depression, says Gluck. “It’s not just that they have an awful disease, but they have lost the ability to process the rewarding aspects of life.”

The ability to test the effects on feedback learning in early onset Parkinson’s disease could provide additional insight into the impact of dopamine loss on cognition and behavior. It also could pave the way for identifying which Parkinson’s patients are most likely to experience agonist-related feedback problems so they can be treated with alternate medications.

Source: Rutgers University, USA

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