⁃ General criteria for AD and control groups:

• Male and/or female;

• Age between 50-85 years;

• Having given their free, informed, 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);

• Patient benefiting from a social security scheme

⁃ AD group:

• Diagnosis of Alzheimer's disease according to the international ATN criteria of Albert et al, (1) who had a diagnostic lumbar puncture and CSF biomarker assay and brain imaging with analysis of hippocampal atrophy; topographic and pathophysiological markers must be positive to confirm the etiopathogenic diagnosis;

• Mild to moderate stage with MMSE score between 10 and 26 ;

• Symptomatic treatments specific to Alzheimer's disease (acetylcholinesterase inhibitors and memantine) and psychotropic treatments (anxiolytics, antidepressants, neuroleptics) are authorized but must be at fixed doses for more than 3 months ;

⁃ Control group:

⁃ \- Patients seen in memory consultation for concern of having AD but for whom the workup is normal. These patients will have had a diagnostic lumbar puncture during the same memory consultation.

⁃ Neurotypical group criteria:

• Male and/or female ;

• Age between 18-35 years or between 50-85 years;

• Having given their free, informed, written and signed consent by the participant and the investigator (at the latest on the day of inclusion and before any examination required by the research);

• Patients without cognitive complaints seen in memory consultation but for whom the assessment is normal or young subjects recruited by advertisement. These participants will have an ex-post determination of plasma Aß and tau biomarkers.