Objective: The aims of the present study were to (i) investigate the effect of subthalamic deep brain stimulation (STN-DBS) on motor learning in Parkinson’s disease (PD) with respect to symptom alleviation and (ii) to characterize the modulated subcortical resting state network associated with improved motor learning.

Background: The STN depicts a unique nexus at the interface of cortical, basal ganglia and cerebellar circuits. Subthalamic neuromodulation is hypothesized to elicit motor circuit alterations, leading to complex motor and non-motor effects. The implications of these motor circuits on motor learning are well established, but evidence for STN-DBS induced changes in motor learning is sparse. We hypothesized that STN-DBS improves motor learning in PD patients through modulation of basal ganglia cerebellar network communication.

Methods: Twenty PD patients undergoing STN-DBS and twenty age-matched healthy subjects performed a visuomotor task. Participants were instructed to perform reach movements towards a target-circle on a display in front of them. A learning coefficient (LC) was defined as the spearman correlation of the performance time over time to give a direct measure of trial to trial improvement throughout the experiment. Clinical symptom severity (UPDRS Part III) was assessed at the time of the experiment and correlated with LCs. The active DBS contacts in the STN were localized (www.lead-dbs.org) and normative resting state connectivity analysis between the active contacts and the cerebellum was conducted.

Results: We show that motor learning is impaired in PD patients when compared to healthy controls and is restored by STN-DBS. Importantly, the clinical impairment correlates with motor learning for both stimulation conditions independently and pooled across conditions. Resting state connectivity analysis revealed that DBS induced improvement in motor learning is correlated with the coupling profile of the active DBS contact to the cerebellum. Stronger spatial correlation to an optimal cerebellar connectivity map is associated with higher DBS induced improvement in motor learning.

Conclusions: We demonstrate that impairment in motor learning is correlated with parkinsonian motor symptom severity and that it is partly restored through subthalamic DBS. We hypothesize that DBS induced modulation of a cerebellar – subthalamic network could account for improved motor learning.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/subthalamic-neuromodulation-restores-motor-learning-in-parkinsons-disease/