1. Population: Age between 70 and 85 years-old, living at home (Participants living in nursing homes are not included).
2. Condition: OABD type 1, type 2 and type 3 assessed by the DSM5 criteria
3. Stable: no MDE or hypomanic state within the last 6 months
4. Ambulatory setting only
5. General condition: Successful Gait speed test from the Short Physical Performance Battery (SPPB): beingable to walk 4 meters in 4 seconds (SPPB NIH Toolbox)44
6. Person affiliated to a social security regime
7. Patients who have given their free, informed and written consent to take part in the study
You may not be if
1. Psychiatric conditions and or co-morbidities
1. Unipolar depression
2. Recurrent unipolar depression
3. Substance use disorder according to DSM5 criteria. Benzodiaepine and/or z-drugs dependence are accepted.
2. Neurological and cerebral co-morbidities
1. Major Cognitive Disorder: significant cognitive decline characterized by extensive cognitive tests or at least a standardized clinical evaluation AND at least loss of autonomy in complex instrumental daily living function, not related to delirium (DSM5 criteria)
2. Medical history of known degenerative disorders: Alzheimer's disease, Lobar Degenerative Fronto-temporal disorders, Lewy Body disease, corticobasal degenerative disorder, Supranuclear Palsy, epilepsy.
3. Medical history of known Parkinson's disease (according to the Movement Disorder Society (MDS)45 criteria)
4. Medical history of known stroke
5. Severe Parkinsonism (defined by MDS-Unified Parkinson's Disease Rating Scale46 \> 20)
3. MRI contra-indications: metallic implants, severe claustrophobia
4. Adults under legal protection (safeguard of justice, curatorship, guardianship), persons deprived of their liberty.
