This study is looking at how brain activity changes in people with Parkinson's Disease (PD), particularly when they experience "fluctuations" in their symptoms. *Parkinson's Disease* is a condition that affects movement and can cause symptoms like shaking, stiffness, and slow movement. But it can also cause non-motor symptoms like mood changes or tiredness, which are less understood.

Researchers will study 30 people with PD who have a device called *Deep Brain Stimulation* (*DBS*). They will record brain activity using special equipment like EEG (Electroencephalogram) and DBS to see how it changes with medication. The study will last about three years, with participants visiting the study centers for tests.

• The study requires multiple visits to the centers over 36 months.
• Participants must have PD and be using or candidates for DBS.
• There are no direct treatments involved, just observing brain activity.

This research could help doctors understand PD better and improve treatments in the future. Participants will need to be on stable medication and can't have severe symptoms that would interfere with the tests.