Impact of Microglial Activation on Synaptic Density in Alzheimer's Disease

Inclusion Criteria: General Inclusion Criteria: * Adult (older than 18 years) * Women old enough to procreate under effective contraception * Signed consent * Absence of general or systemic disorders that may interfere with cognition. Inclusion criteria for EOAD and LOAD patients: * Progressive amnestic syndrome, associated or not with other cognitive impairments, * CDR = 0.5 or 1 * Absence of general or systemic disorders that may interfere with cognition or PET imaging analysis, * Absence of brain lesions as determined by MRI carried out within the framework of usual care. * Presence of CSF biomarkers profile suggestive of AD Inclusion criteria for controls: * absence of subjective problems with memory and normal scores on the MMSE (MMSE \> 27) with no more than one word missing. * older than 50 years old. * Scores on the Free and Cued Selective Reminding Test (FCSRT) of \>25 for free recall and \>44 for total recall. * absence of general or systemic disorders that may interfere with cognition at follow-up. Controls will be matched to AD patients for age and education level. Exclusion Criteria: * Subject with a psychiatric evolutionary and/or poorly checked pathology (left to the judgement of the investigator). * Subject with a grave, severe or unstable pathology (left to the judgement of the investigator) the nature of which can interfere with the variables of evaluation. * Current auto-immune disease * Subject presenting contraindications to the 3T MRI * Known or supposed histories (≤5 years) of severe alcoholism or misuse of drugs * Vascular, inflammatory or expansive, visible lesion in the MRI which can interfere on the criteria of diagnosis. * No health insurance * Pregnant, breast-feeding woman or planning a pregnancy in two years of follow-up. * Diagnosis or history of other possible etiology of dementia, including but not limited to other neurodegenerative disorders. * Person placed under the protection of justice * Patient under guardianship or curatorship