This study is for people with Parkinson's Disease who already have a deep brain stimulator. It looks at how changing the brain stimulation might help with thinking skills, called *cognition*. This study uses a special kind of brain stimulation called *theta burst stimulation*, which is compared to regular stimulation. Participants will take tests to see how well they think and move. The study lasts for one year, and involves changes to the stimulation settings at different times. Participants will have brain scans called fMRI (functional magnetic resonance imaging) at specific times during the study to check brain activity. You must be over 18 and have stable medication to join. People with epilepsy, dementia, or major substance abuse cannot join.

• The study is one year long with different phases and testing.
• Participants will have brain scans and take thinking and movement tests.
• People with certain medical histories can't participate.