The Effect of Single Session Transcranial Direct Current Stimulation on Sequential Motor Learning in Parkinson's Disease

Parkinson's disease is characterised by deficits of motor control triggered by impaired basal ganglia function, such as bradykinesia and tremor. Beyond the visibly recognisable motor symptoms of Parkinson's disease, the ability to learn a sequence of movements is also compromised and poses a significant barrier to effective rehabilitation. In healthy individuals, transcranial direct current stimulation applied over the primary motor cortex during motor task practice has been shown to significantly improve motor learning compared to placebo conditions. The present study sought to examine the effect of a single session of transcranial direct current stimulation applied over the primary motor cortex in people with Parkinson's disease on sequential motor learning performance. Participants learnt two finger tapping sequences, with task difficulty indexed by sequence length, and task consolidation further examined using a dual-task paradigm. Task related cortical haemodynamic activity was recorded using functional near-infrared spectroscopy.