The goal of this clinical trial is to determine the relative efficacy of fMRI model guided Transcranial Direct Current Stimulation (mgTDCS) in improving the depressive symptoms of patients with Parkinson's Disease (PD). The main questions it aims to answer are: 1) Can the use of mgTDCS significantly improve the self-reported level of depression and apathy in patients with PD from pre-intervention to post-intervention compared to a sham control? 2) Can the use of mgTDCS significantly normalize the cortical eeg alpha asymmetry so commonly seen in depressed patients compared to sham mgTDCS? 3) Can the use of mgTDCS significantly improve scores on neuropsychological tests of working memory?

This study seeks to expand the growing body of literature on the use of a particular type of low voltage electrical stimulation known as Transcranial Direct Current Stimulation (TDCS) to reduce the symptoms of Parkinson's Disease (PD). One common disorder that can result from, and/or be exacerbated by PD is Major Depressive Disorder. In particular, apathy has been noted as a common and detrimental component for those with PD. While many studies have been performed on PD patients using TDCS, the consensus in the literature is that results are widely variable.

Participants will:

• complete self-report measures and neuropsychological tests
• undergo eeg recording pre and post intervention
• participate in 15, 46 minute sessions (2 13 minute stimulation sessions with 20 minutes of rest between) of mgTDCS over the course of 4-5 weeks Researchers will compare active mgTDCS to Sham mgTDCS to see if active mgTDCS is more effective. A non Parkinson's group of depressed controls who are age-matched to the PD patients will serve to determine if treatment effects are specific to PD or generalize to depression more generally.

Inclusion Criteria:

• 19 to 65 years in age.
• Parkinson's Group must have a physician dx of Parkinson's Disease
• Must meet exhibit elevated levels of depression on the Beck Depression Inventory (scores of 20 or above).
• Must be willing and able to travel of the Psychology Department for EEG and tDCS sessions.
• Participants who have undergone surgery for Deep Brain Stimulation implantation may be enrolled if advised to and monitored by their physician.
• Read and understand spoken English.

Exclusion Criteria:

• No history of or being treated for epilepsy or other seizure disorders.
• No history of penetrating head wounds or TBI greater than mild TBI.
• No history of atypical Parkinson's

Participants will not be told whether they are receiving tDCS or SHAM tDCS in order to reduce subject expectancy bias.