MRI Study of Brain Activity in Healthy Adults and Individuals With Parkinsonism and Rapid Eye Movement Disorder.

Inclusion Criteria: * Healthy Control • Age 35-85 Parkinson Disease (PD) Age 35-85 Diagnosis of clinically definite PD made by a movement disorders specialist, with evidence of the following features: * Presence of bradykinesia and 1 or both of the following: 1. Rest tremor 2. Rigidity * Asymmetric Onset * Progressive motor symptoms * Levodopa responsive * Duration at least 1 but not more than 10 years * Hoehn and Yahr Stage 1-2 Progressive Supranuclear Palsy (PSP) Age 40-85 Diagnosis of clinically definite PSP, with the following features: * Gradually progressive disorder. * Onset after age 39 * Supranuclear palsy\* and postural instability with falls in the first year of disease onset\*. * No evidence of other disease. Parkinsonism of Other or Undetermined Cause (POC) Age 35-85 Diagnosis of parkinsonism of undetermined other other cause by a movement disorders specialist, with the following features: * Signs and symptoms of Parkinsonism including 1. Bradykinesia 2. Mixed or resting tremor 3. Rigidity 4. Characteristic deficits of gait and balance associated with Parkinsonism Essential Tremor (ET) Age 35-85 Diagnosis of essential tremor, with the following features: * A 2+ postural tremor of at least 1 arm (a head tremor may also be present, but is not sufficient for diagnosis) * On examination, there must be 1. a 2+ kinetic tremor during at least 4 tasks, or; 2. a 2+ kinetic tremor on 1 task and a 3+ kinetic tremor on a second task; tasks include pouring water, using a spoon to drink water, drinking water, finger-to-nose, and drawing a spiral * If on examination, the tremor is present in the dominant hand, then by report, it must interfere with at least 1 activity of daily living. REM Behavior Disorder (RBD) Age 25 - 85 Documented diagnosis of REM sleep behavior disorder (RBD) by a sleep medicine specialist, with the following clinical features: * Presence of REM sleep without atonia on polysomnography * At least one of the following conditions: 1. Sleep-related, behaviors by history (eg, dream enactment behavior) 2. Abnormal REM sleep behavior documented during PSG monitoring Exclusion Criteria: Healthy Control * Pregnancy * First-degree blood relative affected by PD * Neurodegenerative disease * History of repeated head injury, encephalitis, brain surgery, stroke, dementia, neuroleptic exposure, or serious medical illness that may interfere with participation. Parkinson Disease (PD) * Any exclusion criteria that would exclude a healthy control patient * Atypical features indicative of a Parkinson-Plus disorder Progressive Supranuclear Palsy (PSP) * Any exclusion criteria that would exclude a healthy control patient * Any finding atypical for PSP * Neuroradiologic evidence of relevant structural abnormality unrelated to appropriate changes known to be associated with PSP Parkinsonism of Other or Undetermined Cause (POC) * Any exclusion criteria that would exclude a healthy control patient * Signs and symptoms suggestive of clear diagnosis of idiopathic Parkinson disease, Progressive Supranuclear Palsy, or Essential Tremor Essential Tremor (ET) * Any exclusion criteria that would exclude a healthy control patient * No other potential etiologic factors for the tremor * Any first-degree blood relative affected by PD * History of neurodegenerative disease REM Behavior Disorder (RBD) * Any exclusion criteria that would exclude a healthy control patient * Sleep disorder not better explained by another sleep disorder, medical or neurological disorder, mental disorder, medication use, or substance use disorder