Inclusion Criteria:  Diagnosis of Parkinson's disease based on presence of at least 2 cardinal features (tremor, rigidity or bradykinesia) OR healthy adult with no neurologic disease Age > 18 years old  Exclusion Criteria:  Dementia as indicated by score on Montreal Cognitive Assessment < 19 Active hallucinations or psychosis Contraindications to MRI (metal implant, claustrophobia)