In Vivo Involvement of the Cholinergic and Dopaminergic Systems in the Pathophysiology of Apathy.

Inclusion Criteria: * Patient of legal age and younger than 75 years * Patient with a Rankin score less then or equal to 2 and with or without apathy, demonstrated by AI scales at 3 months after stroke (apathetic patient = AI scale score \> 2) * Affiliate or beneficiary of a social security scheme * Subjects (female study subjects and female partners of male participants) using highly effective contraceptive methods (intra-uterine device, progestin or estrogen-progestin contraceptive, sterilization) * 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) Exclusion Criteria: * Patients over 75 years old * Taking of any pharmacological treatment likely to affect cholinergic systems at the time of PET-scan: Amitriptyline, Atropine, Brompheniramine, Chlorphenamine, Chlorpromazine, Clomipramine, Clozapine, Dimenhydrinate, Diphenhydramine, Doxepine, Hyoscyamine, Imipramine, Meclozine, Nortriptyline, Oxybutynine, Promethazine, Scopolamine, Trimipramine, Hydroxyzine. * Taking of any pharmacological treatment likely to affect dopaminergic systems at the time of PET-scan: glucagon, haloperidol, reserpin * Taking of any selective serotonine reuptake inhibitors treatment * White matter T2 hyperintense lesions (Fazekas score \> 3) * NYHA Class III to IV Heart Failure Patient * Patients with allergy or conter-indication to entacapone * Subjects with positive pregnancy test (BHCG dosage and Urine dipstick), and/or currently breast-feeding * Patients unable to come back to hospital for at least 2-follow-up visits * Patient with a chronic neurological disorder or severe psychiatric disorder * Patient with cognitive impairment (MoCA\<24) and depression (CES-D score \> 17 for men and \>23 for women) * Patient presenting a counter-indication for MRI * Patient presenting a counter-indication for TEP with \[18F\]-FEOBV or \[18F\]-FDOPA (known allergy) * Patient who underwent a PET examination in the previous month * Patient with state of health not allowing a displacement in the department of imaging of the CHU: bedridden state, state of health very deteriorated * Patient deprived of liberty by judicial or administrative decision * Patient under legal protection or unable to express its own consent * Subject within exclusion period from another clinical trial