Striatum and Hippocampus on Different Time Scales

Inclusion Criteria: * Huntington's disease gene carriers * Patient included in the BioHD protocol * Age from 18 to 90 years old * Symptomatic patient * TFC ≥ 11 * UHDRS motor\> 5 * Native language: French * Affiliation to a social security or to another social protection * Signature of informed consent • Patients with Alzheimer's disease * MMS from 20 to 26 (included) * Age: from 60 to 90 years old * Native language: French * Progressive deterioration of memory reported by patient or caregiver for more than 6 months * Profile at RL /RI 16: no significant improvement with indexing * Episodic memory disorder isolated or associated with other cognitive disorders * MRI: Atrophy of the median temporal lobe * Affiliation to a social security or to another social protection * Signature of informed consent • Healthy subjects * Healthy subject included in the BioHD protocol * MMS ≥ 26 * Age from 18 to 90 years old * Native language: French * Affiliation to a social security or to another social protection * Signature of informed consent Exclusion Criteria: * Huntington's disease gene carriers * Intellectual deterioration preventing understanding of the protocol * Other dementia than Huntington's disease * Patient living alone at home * Major depression * Patient under legal protection * Patient deprived of liberty * Pregnant or breastfeeding woman, situation known to the investigator * Inability to handle an electronic tablet * Patients with Alzheimer's disease * Intellectual deterioration preventing understanding of the protocol * Patient living alone at home * Sudden onset of memory impairment * Early onset of the following symptoms: difficulty in walking, convulsions, changes in behavior * Focal neurological characteristics including hemiparesis, sensory loss, visual field deficit * Early extrapyramidal sign * Other dementia than Alzheimer's disease * Major depression * Cerebrovascular disease * Toxic, metabolic or infectious anomaly * Patient under legal protection * Patient deprived of liberty * Pregnant or breastfeeding woman, situation known to the investigator * Inability to handle an electronic tablet * Healthy subjects * Intellectual deterioration preventing understanding of the protocol * Known neurological or psychiatric illness * Patient under legal protection * Subject deprived of liberty * Pregnant or breastfeeding woman, situation known to the investigator * Inability to handle an electronic tablet