Deep Brain Stimulation of the nbM to Treat Mild Cognitive Impairment in Parkinson's Disease

Inclusion Criteria: * Informed consent signed by the subject. * Parkinson's disease per UK Parkinson's Disease Society Brain Bank (Queens Square) criteria * Diagnosis of PD-MCI, amnestic subtype per MDS criteria (Level II assessment) * DBS candidate for GPi targeting per the consensus committee * 50 - 75 years of age * Primary English speaking * Minimum of 10 years of education * Motorically and cognitively capable of completing evaluations and consent * Medically cleared for surgery and anesthesia * Subject must be on stable doses of any medication used to treat PD or cognition for 3 months prior to study entry * Female subjects with child-bearing potential have a negative serum pregnancy test prior to DBS surgery - Exclusion Criteria: * Dementia per DSM-V criteria * Condition precluding MRI * History of supraspinal CNS disease other than PD * Medical condition or required medication compromising cognition * Alcohol use of more than 4 drinks per day * Currently uncontrolled moderate-severe depression (BDI\>20) * History of suicide attempt in the year preceding study screening * History of schizophrenia, delusions, or currently uncontrolled visual hallucinations * Use of cholinesterase inhibitor * Subjects who require rTMS, ECT, diathermy, or repeat MRI procedures to treat a medical condition. * Subjects with a history of seizure disorder * Subjects who have made a suicide attempt within the prior year, * Subjects with any medical contraindications to undergoing DBS surgery (eg, infection, coagulopathy, or significant cardiac or other medical risk factors for surgery) * Subjects with an implanted stimulator such as a cardiac pacemaker, defibrillator, neurostimulator and cochlear implant * Subjects who are pregnant or nursing.