Imaging Depression in Parkinson's Disease

This study is trying to better understand depression in people with Parkinson's disease by using brain imaging scans (PET). It also tests whether ketamine (a fast-acting medication) can help relieve depression symptoms in these patients. **You may be eligible if...** - You are between 40 and 80 years old - You have a clinical diagnosis of Parkinson's disease - If you have depression related to Parkinson's, your symptoms are at least moderate in severity (score of 15 or higher on a standard depression scale) - Women of childbearing age must have a negative pregnancy test **You may NOT be eligible if...** - You have significant memory problems or dementia (MoCA score below 21) - You have another major psychiatric disorder besides depression - You have uncontrolled medical conditions (heart disease, kidney disease, seizures, or brain injury) that could put you at risk - You have had excessive radiation exposure from research studies in the past year - You take certain seizure medications that could affect brain scan results - For the ketamine part: you have uncontrolled high blood pressure (140/90 mmHg or above) or a history of substance abuse Talk to your doctor to see if this trial is right for you.