Dopamine-independent effects of combining transcranial direct current stimulation with cued gait training on cortical excitability and functional mobility in Parkinson's disease

Objective: To investigate the dopamine-dependent effect of combining transcranial direct current stimulation (tDCS) with visually cued gait training on cortical excitability and functional mobility in individuals with Parkinson's disease. Design: A pilot, randomized, double-blind, controlled trial. Methods: Twenty-two patients with Parkinson's disease were randomly assigned to 2 groups: (i) active anodal tDCS over the supplementary motor area (experimental group), or (ii) sham tDCS (control group). After tDCS, both groups participated in a visually cued gait training. Functional mobility was evaluated with the Timed Up and Go test (TUG). Cortical excitability was assessed by active motor threshold and motor-evoked potential amplitudes elicited by transcranial magnetic stimulation in patients in on and off medication states. Results: In the TUG test both groups achieved improvements either in on or off medication condition compared with baseline. However, for both medication conditions, these gains were maintained only in the experimental group during 1-month follow-up, compared with baseline. In the experimental group, enhancement of cortical excitability was observed at post-intervention and 1-month follow-up (both only for the "on" phase) compared with baseline. Conclusion: These findings suggest that tDCS, independent of dopaminergic medication state, might prolong the positive effect induced by cued gait training on functional mobility.