Investigations of Dementia in Parkinson Disease

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.