Parkinson's disease (PD) is a progressive neurological disease that has effects on both movement and mental health. One of the most common mental health complications of PD is depression. Up to 30% of Parkinson's patients will experience depression at some point. We aim to investigate whether transcranial direct current stimulation (tDCS), a type of electrical stimulation for the brain, can improve depression in PD as well as improve motor function in PD.