 tDCS intervention: Subjects will be randomized to receive either a real or sham tDCS intervention. Each intervention will consist of 10, 20-minute treatments completed over 2 consecutive weeks i.e., 5 per week, following previously established protocols. A single, weekly maintenance treatment will then be provided for the following 12 weeks note: for depression, maintenance tDCS is most often provided once every two weeks; we will take a more conservative approach here in this first long-term study for FOG in PD. 