Objective: We characterized different aspects of bimanual coordination in patients with PD, including inter-limb coupling, and then determined whether they were altered by therapeutic modulation of basal ganglia function through subthalamic (STN) deep brain stimulation (DBS) or dopaminergic medication.

Background: Patients with Parkinson’s disease (PD) often present with bimanual coordination deficits. However, the exact origin of this deficit remains unclear. One aspect of bimanual coordination is inter-limb coupling. This is a specific feature characterized by the harmonization of movement parameters between limbs.

Methods: Twenty PD patients were tested before STN DBS surgery; with and without medication. Post- surgery, patients were also tested with their stimulators on and off, as well as with and without medication. Patients were asked to perform a unimanual and bimanual rapid repetitive diadochokinesis task (pronation-supination). The difference in mean amplitude and mean duration of cycles between hands was computed in order to assess inter-limb coupling. Also, mean angular velocity of both hands and structural coupling between hands, as assessed by Pearson correlations, were also computed for the bimanual task.

Results: There was a positive effect of medication and stimulation on mean angular velocity, which relates to clinical improvement. PD patients exhibited temporal inter-limb coupling that was not altered by either medication or STN stimulation. However, PD patients did not exhibit spatial inter-limb coupling. Again, this was not altered by medication or stimulation.

Conclusions: The current study demonstrated that temporal inter-limb coupling was not impaired in PD and it was not affected by either dopaminergic medication or STN DBS. In contrast, PD patients demonstrated a lack of spatial inter-limb coupling which was not improved by either therapeutic interventions. Collectively, the results suggest that structures independent of the dopaminergic system and basal ganglia may mediate temporal and spatial inter-limb coupling.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-inter-limb-coupling-modified-by-subthalamic-deep-brain-stimulation-and-dopaminergic-medication-in-parkinsons-disease/