Pain in Parkinson's Disease: Exploration of the Serotonin System in Positron Emission Tomography (PET [18F]-MPPF)

Inclusion Criteria: * Patients with PD defined according to United Kingdom Parkinson's Disease Brain Bank (UKPDSBB) criteria * Patients with stable anti-parkinsonian treatment for at least 4 weeks prior to inclusion * Patients with a Montreal Cognitive Assessment (MoCA) score \> 25 * Patients with a Hospital Anxiety and Depression Scale (HADS)-D score ≥ 11 * Person affiliated or benefiting from a social security scheme. * Free, informed and written consent signed by the participant and the investigator (at the latest on the day of inclusion and before any examination required by the research). • For patients with pain * Patients with PD-related central pain defined according to the criteria of Marques et al, 2019 * Patients with chronic central pain (i.e. present for at least 3 months) * Patients who have average pain over the previous month according to a VAS ≥ 4. • For patients without pain * Patients who do not have pain defined as VAS ≤ 4, meaning that it does not interfere with daily activity. Exclusion Criteria: * Patients treated with second line therapy * Patients with a history of significant psychiatric pathology according to the investigator * Patients treated with drugs interacting with 5HT1A receptors in the previous 4 weeks * Patients with contraindication to MRI * Patients refusing to be informed of an abnormality discovered during brain imaging * Patients with dyskinesias judged by the investigator to be disabling for imaging. * Patients under guardianship or other legal protection, deprived of their liberty by judicial or administrative decision * Pregnant woman, breastfeeding woman