Simple Test May Help Track Dopamine Loss in Parkinson’s Patients

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dot-test-parkinsonsA simple test may be able to gauge what more complex technological tests could not perceive. Dopamine loss, a hallmark of Parkinson’s disease, is currently very difficult to assess, according to Katherine R. Gamble, a psychology Ph.D. student at Georgetown University who helped create a new test. The test is technologically simple, but gives an insight into dopamine loss previously not possible.

Gamble said, “Use of this test, called the Triplets Learning Task (TLT), may provide some help for physicians who treat people with Parkinson’s disease, but we still have much work to do to better understand its utility.”

The TLT tests implicit learning, a form of learning that occurs without awareness or intent. According to Janice Wood, implicit learning relies on the caudate nucleus, an area of the brain affected by loss of dopamine.

Gamble explained the test is a sequential learning task which doesn’t require complex motor skills, which tend to decline in Parkinson’s patients.

Throughout the test, participants are shown four open circles, and they are told to respond only when a green dot is shown. Two red circles would be flashed, then finally a green. However, unknown to the participants, the first red dot always predicted the location of the green dot. Healthy participants implicitly learn the patterns, making them faster and more accurate over time.

In this study, 27 participants with Parkinson’s implicitly learned the dot pattern with training, but over time the loss of dopamine appeared to negatively impact the learning compared to healthy control participants.

“Their performance began to decline toward the end of training, suggesting that people with Parkinson’s disease lack the neural resources in the caudate, such as dopamine, to complete the learning task,” Gamble stated.

“This work is important in that it may be a non-invasive way to evaluate the level of dopamine deficiency in PD patients, and which may lead to future ways to improve clinical treatment of PD patients,” said Steven E. Lo, M.D., associate professor of neurology at Georgetown University Medical Center, and a co-author of the study.

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