Transcranial direct current stimulation (TDCS) over supplementary motor area (SMA) improves upper limb movement in individuals with Parkinson's disease


One of the most debilitating aspects of Parkinson's disease (PD) is slowness of reactions and movements, termed bradykinesia. Previous studies have shown functional improvements following the application of transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique. For example, in healthy participants, reaction time (RT) was significantly facilitated following tDCS applied over supplementary motor area (SMA). Therefore, we investigated the influence of tDCS applied over the SMA in individuals with PD. Ten volunteers with idiopathic PD presenting with freezing of gait (FoG) were asked to perform two RT tasks as quickly as possible following an auditory go-signal: 1) an upper limb movement requiring a 20° right elbow extension, and 2) gait initiation from a quiet standing position. Participants performed 20 RT trials of the elbow extension task followed by 10 gait initiation trials. After these first blocks of trials, participants either received sham- or anodal-tDCS over the SMA (counterbalanced), and then performed a second set of trials in each task after an 8 minute rest period. Participants performed the same testing one week later but received the other tDCS protocol. For both tasks, no significant RT differences were found due to tDCS. However, in the upper limb task there was a significant effect of tDCS on kinematic parameters, whereby in post-anodal trials participants showed significantly shorter movement time (p=.002) and shorter time to peak displacement (p=.006). These results provide evidence that anodal-tDCS over SMA may contribute to improvements in upper limb movement quality for individuals with PD.

Acknowledgments: Supported by NSERC and the Ontario Ministry of Research and Innovation and Science