The purpose of this study is to use a brain imaging method called PIB PET to determine dementia subtypes in patients with Parkinson's disease. The ultimate goal of this project is to be able to identify individuals with PD who are at risk of developing dementia, and to distinguish the underlying cause of dementia.

The purpose of this study is to use a brain imaging method called PIB PET to determine dementia subtypes in patients with Parkinson's disease. The ultimate goal of this project is to be able to identify individuals with PD who are at risk of developing dementia, and to distinguish the underlying cause of dementia. We will be including both PD and normal subjects in this study. This a long term study and we are considering including a total of 320 participants in this protocol.

Inclusion Criteria:

• PD patients must exhibit three of the following cardinal signs: rest tremor, rigidity, bradykinesia, or postural instability; or two of these features with one of the first three displaying asymmetry.

Exclusion Criteria:

• history of head trauma, major neurological or psychiatric diseases other than Parkinson disease and dementia, e.g. stroke, multiple sclerosis, depression or schizophrenia
• severe systemic diseases
• inability to lie still for 90 minutes
• metallic implants, pacemakers, or any other contraindication to MRI
• refusal to consent to brain donation

Participants with and without Parkinson disease will be recruited from the Movement Disorders Center at Washington University, the St. Louis metro area, and throughout the midwest region.