A Test to Determine Rate of Dopamine Loss in PARKINSON’S DISEASE






Loss of dopamine in neurons is a given in the cause of PARKINSON’S DISEASE, but there has been no non-invasive way to measure how much dopamine has been lost or what the rate of dopamine loss might be.  Clinical treatment and dopamine replacement therapies could be made more exact if this could be determined.

A team of investigators from the Cognitive Aging Laboratory at Georgetown University have devised a test that may help neurologists determine the amounts of dopamine lost  on an individual basis for people with PARKINSON’S DISEASE.  It is an amazingly simple test, but the early small study has shown good results.

The Triplet-Learning Task (TLT) was developed by Katherine R. Gamble, who is a psychology student working on a Ph.D. Her senior investigator is Darlene Howard, Ph.D. .  It is based on implicit learning, a type of learning that occurs without awareness.  The brain region that is involved in implicit learning is the caudate nucleus, which is also affected by the loss of dopamine in PARKINSON’S DISEASE..

The test does not involve any complex motor skills: it is a sequential learning task.  Subjects are shown four open circles and two red dots.  They are asked to respond when a green dot appears.  After a bit of practice, subjects quickly learn how to determine where that green dot will appear and their response time become fasters and their responses more accurate.  However, with a loss of dopamine, response time becomes slower and accuracy falters.    This may prove to be a valuable, non-invasive test to help neurologists determine what stage of the disease process the patient is experiencing  or to measure if the amount of dopamine replacement is adequate or effective.



Georgetown University Medical Center (2013, November 9). Simple dot test may help gauge progression of dopamine loss in Parkinson’s disease. ScienceDaily. Retrieved November 12, 2013, from http://www.sciencedaily.com­/releases/2013/11/131109192838.htm


Review by Marcia McCall


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