Current surgical treatments for Parkinson's disease have associated risks that may prevent patients from being offered surgery called "deep brain stimulation" or DBS. This is mainly because electrodes have to be placed through brain tissue to reach the target. Stimulation at the surface of the brain might be a potential alternative, but current research has not shown consistent results, and this may be because the mechanism of action is not clear. In this study, we aim to stimulate and record the brain at the surface to help answer this question and potentially improve the consistency and effectiveness of this treatment.