The Role of Priors in Hallucinatory Perception in Parkinson's Disease

Inclusion Criteria: * Adults diagnosed with Parkinson's disease (with or without visual hallucinations) or healthy volunteers. * Age 18 - 85 years. * Consent to participate. Exclusion Criteria: * Currently participating in another clinical or therapeutic trial involving the testing of a drug treatment. * Inability to perform cognitive tests due to: Non-psychiatric (somatic) conditions likely to affect cognitive abilities. Peripheral sensory or motor deficits. Acute clinical conditions (e.g., agitation, impaired consciousness). * Diagnosis of dementia. * Individuals covered by Articles L1121-5 to L1121-8 of the French Public Health Code (Code de la Santé Publique), including: Pregnant women, women in labor, or breastfeeding mothers. Individuals deprived of liberty by judicial or administrative decision. Individuals receiving psychiatric care under Articles L. 3212-1 and L. 3213-1 (excluding those covered by Article L. 1121-8). Individuals admitted to a healthcare or social institution for purposes other than research. Minors or adults under legal guardianship or unable to express consent. \- Individuals with a hierarchical relationship to any professional involved in the study. Only for healthy volunteers: \- Personal history of diagnosed neurological disorders. Post-Inclusion Exclusion: \- Participants included in the study but found to have a MoCA score below 24 will be excluded from the study.