Objective: To investigate goal-directed behavior in people with Parkinson’s disease (with and without Parkin mutations) and healthy controls using a computer based task.

Background: In early idiopathic Parkinson’s disease (PD) there is initial loss of dopaminergic innervation to the caudal putamen, which governs habitual movement. With disease progression, however, this may spread to the rostral regions of the basal ganglia involved in goal-directed behaviour. Parkin gene mutations causes more diffuse dopaminergic denervation to basal ganglia including the more rostral caudate nucleus. We investigated the effect of these topographical differences using a computer based goal-directed movement learning task.

Methods: A cohort of PD patients (with and without Parkin mutations) and age-matched healthy controls repeatedly manipulated a joystick to move an unseen cursor on a laptop screen in two tasks: Task 1 involved moving the cursor to a seen target; Task 2, to an unseen target. By examining the curves of refined movements from Task 1 to Task 2 (which requires action selection by the basal ganglia) we can quantify the rate at which goal-directed movements are learned, independently of overall speed of movement. Standard clinical and neurocognitive data were also collected, including the Wisconsin Card Sorting Test.

Results: PD patients performed Task 1 equivalently to healthy controls. However, in Task 2, early refinement of goal-directed behaviour was impaired compared with healthy controls. Final performance of Task 2 was comparable to controls implying that motor task learning, although slower, approaches that of controls over time. We found differences in movement learning curves between patients with Parkin mutations were seen compared with non-Parkin participants.

Conclusions: This study paradigm displays the ability to quantitatively assess goal-directed movement in a manner that is independent of slowness of movement. The results above show that, in spite of bradykinesia, medicated PD patients perform goal-directed behaviour as well as controls, provided no action selection is required by the basal ganglia. If action selection is required, early refinement of goal directed behaviour becomes impaired compared to controls but approaches that of controls over time. There are subtle differences in motor learning in Parkin patients which may reflects the fact that Parkin PD is a nigrinopathy without any cortical pathology.

« Back to 2017 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/goal-directed-movement-in-idiopathic-parkinsons-disease-and-the-effect-of-parkin-mutations/