Evaluation of Neurocognitive Changes in Parkinson's Disease After Low Frequency Burst Stimulation

In this single-center pilot study, the investigators will study both acute and chronic changes to neurocognitive and motor performance in response to interleaving gamma/theta (theta burst) stimulation compared to standard-of-care gamma stimulation. This study will be a randomized double-blinded crossover study. Each patient's baseline voltage intensity will be unchanged. During the first outpatient visit, a baseline assessment (under baseline stimulation parameters, including frequency, pulse width and voltage) consisting of motor and cognitive tests will first be performed. After one week of titration on the theta burst stimulation paradigm, all patients will randomized to either baseline or theta burst stimulation settings for one week. Motor testing (UPDRS) and neuropsychological testing will be performed after this week. Each patient will then be programmed to the other stimulation paradigm for another week. At the end of this third week, neuropsychological and motor testing will again be performed. Patients will again be randomized into either baseline gamma stimulation or theta burst stimulation for the chronic phase of the study. Repeat neuropsychological and motor testing will be performed at three months. Each patient will switched to the other stimulation strategy and repeat neuropsychological and motor testing will be performed after another three months. After the first 6 months, patients will be placed on open-label theta burst stimulation for 6 months (total of one year). At the end of one year, patients will undergo repeat neuropsychological and motor testing, after which they will be reprogrammed to their initial settings or given the option to remain on theta burst stimulation parameters. Functional magnetic resonance imaging will be acquired during baseline, week 15, and week 27 visits for patients with compatible devices that meet the inclusion criteria.