The impact of non-invasive brain stimulation on pain in Parkinson's.

This study will use a randomised controlled trial using transcranial direct current stimulation (tDCS). Upon study entry, participants will be assigned to one of the following 2 groups: 1. Anodal (active) tDCS 2. Sham (control) tDCS Active tDCS Participants in the active tDCS groups (the anodal (active) group) will receive 20 minutes of constant current 1.5 mA (equivalent to 0.08 mA/cm2). Stimulation over the left dorsal lateral prefrontal cortex (DLPFC). This level is consistent with safety guidelines (Nitsche et al., 2008) and is well tolerated in those with Parkinson's Disease (PD; Lawrence et al., 2018). tDCS will be delivered by a constant current stimulator (Soterix®), which is administered using two 35 cm 2 sponge electrodes that have been soaked in saline solution. The anode electrode will be placed over F3 according to the 10-20 international system for EEG electrode placement, to stimulate the left DLPFC. The cathode (neutral) electrode will be position on the left side of the forehead. There will be a period of 30 seconds at the beginning and end of the tDCS for ramp up/down. This intervention will be administered by the project PhD student who will be fully trained on the the set-up and administration of tDCS. The intervention will be delivered face-to-face and individually. Participants will receive 20 mins of tDCS, twice a week, for four weeks (8 sessions in total).