Scientists have developed a new neuropsychological memory test that could uncover how Parkinson's disease can alter people's ability to learn about the consequences of the choices they make.
Using the novel feedback-learning task on patients in Hungary, Dr. Mark Gluck at Rutgers' research team found that non-medicated patients in the early stages of Parkinson's were selectively impaired at learning from reward.
"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," said Gluck.
The researchers at Rutgers University, Newark, observed that the reward-learning deficit in un-medicated Parkinson's patients is quite opposite to that in patients who begin treatment with dopamine agonists-a standard therapy for treating the disease's motor symptoms.
On dopamine agonists, a patient's ability to learn from positive rewarding outcomes improved to normal levels, but their ability to learn from negative (or punishing) outcomes, which had previously been normal, was now impaired.
Gluck said that an increased sensitivity to learning from events that results in positive outcomes, coupled with a decrease in the ability to learn from negative outcomes, could explain why some Parkinson patients treated with dopamine agonists develop impulse-control disorders, including pathological gambling, hypersexuality, alcoholism, and compulsive eating and shopping.
Such behaviors can be understood as reward-seeking behaviors in the absence of appropriate sensitivity to their negative consequences.
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.
The findings of the study have been published in the journal Brain.