Anodal tDCS of the Primary Motor Cortex and Motor Sequence Learning in a Large Sample of Patients with Parkinson’s Disease

Objectives: Parkinson’s disease (PD) has been associated with impaired motor sequence learning (also known as procedural learning). In the current study, we determined the potential of anodal transcranial direct current stimulation delivered over the primary motor cortex to promote the acquisition of sequential movement in a large sample of patients with idiopathic PD and matched controls. Methods: Thirty-one idiopathic PD patients and 33 healthy controls, matched for age, gender, and education, participated in the study. Both groups received anodal and sham transcranial direct current stimulation delivered over the primary motor cortex during the acquisition of a novel sequence movement in the Serial Reaction Time task. Results: Motor sequence learning proved to be intact in patients relative to controls. Compared to sham stimulation, anodal transcranial direct current stimulation of the primary motor cortex did not significantly improve motor sequence learning in patients, nor controls. Conclusions: Anodal transcranial direct current stimulation delivered over the primary motor cortex did not exert a positive effect on the acquisition of sequential movement in patients with Parkinson’s disease. More research is needed to establish the determinants associated with a positive effect of tDCS on sequential skill in PD, such as medication status, the amount of tDCS stimulation needed, as well as the brain regions that need to be targeted to elicit a beneficial response.