Network-based biOmarker Discovery of Neurodegenerative Diseases Using Multimodal Connectivity

Inclusion Criteria: * For all participants: * French mother tongue * right-handed * with a level of education equal to or higher than the Certificat d'Études Primaires (Primary School Certificate) * Free of any medical or psychiatric condition likely to interfere with cognition (excluding diagnosis for patients) * Affiliated with a social security scheme * Having received oral and written information about the protocol and having signed a consent form to participate in this research. DCS+ group: \- Meeting the diagnostic criteria for "subjective cognitive decline-plus" (Jessen criteria (Jessen et al., 2014). Alzheimer's patients "Mild Cognitive Impairment due to Alzheimer's Disease," "MCI-MA": \- Meeting the diagnostic criteria for "Mild neurocognitive disorder due to Alzheimer's disease" (criteria of (Albert et al., 2011)) De novo" Parkinsonian patients, "MPdn": \- Presenting with newly diagnosed ("de novo") Parkinson's disease and free of cognitive deficits (criteria of Postuma et al., 2015 (Postuma et al., 2015)) Parkinsonian patients with "Mild Cognitive Impairment, "MCI-MP": \- Presenting Parkinson's disease associated with "mild neurocognitive impairment" (criteria of Litvan et al., 2012 (Litvan et al., 2012)) Exclusion Criteria: * All participants (healthy volunteers and patients) * Contraindications to MRI : * Abdominal circumference + upper limbs sticking to the body \> 200 cm; * Implantable pacemaker or defibrillator; * Neurosurgical clips; * Cochlear implants ; * Neural or peripheral stimulator; * Intra-orbital or encephalic metallic foreign bodies; * Endoprostheses fitted less than 4 weeks ago and osteosynthesis devices fitted less than 6 weeks ago; * Claustrophobia. * Pregnant or breast-feeding women; * Adults under legal protection (safeguard of justice, curatorship, guardianship), persons deprived of liberty. Patients only * Score \>2 on the modified Hachinski scale (Hachinski et al., 2012) * Dementia according to McKhann criteria (McKhann et al., 2011) * Sensory deficit interfering with experimental tests Healthy volunteers only \- Cognitive impairment (MoCA score \< 26)