Investigations of Dementia in Parkinson Disease

This study is using advanced brain MRI scans to investigate why some people with Parkinson's disease develop dementia (memory loss and thinking problems) while others do not, in order to find early warning signs. **You may be eligible if...** - You have been diagnosed with Parkinson's disease, showing at least three of the classic signs: resting tremor (shaking at rest), muscle stiffness, slowness of movement, or balance problems — or at least two of these with one side more affected **You may NOT be eligible if...** - You have a history of significant head trauma - You have other major neurological or psychiatric conditions such as stroke, multiple sclerosis, depression, or schizophrenia - You have severe medical illnesses - You cannot lie still for 90 minutes (required for the MRI) - You have metal implants, a pacemaker, or other conditions that make MRI unsafe - You refuse to consent to donating your brain for research after death Talk to your doctor to see if this trial is right for you.