Isotopic Imaging for Prodromal Alzheimer's Disease

Inclusion Criteria for the group with memory problems: * patient consulting for memory problems * caucasian * memory complaint is validated by a clinical evaluation * cognitive performance is sufficiently well preserved so that a diagnostic of dementia cannot be made (according to the DSM-IV-R and NINCDS-ADRDA criteria) at the time of inclusion * the patient speaks French * presence of an informant * accepts to sign consent Inclusion Criteria for the group without memory problems (reference population): * at least four years of formal education * patient consulting for memory problems * memory problem reported by the patient is not validated by the consultation, nor by the battery of tests specified during screening * presence of an informant * Clinical Dementia Rating (CDR) = 0 * accepts to sign consent Exclusion Criteria: * Instrumental Activities of Daily Living (IADL): at least two items \> 1 * Anticholinesterasic treatments and/or memantin before study inclusion * major depressive syndrome, according to the Global Depressive Scale * Known neurodegenerative disease or general disease or major physical problems that could interfere with cognitive functioning and testing * Pathology that might lead to death in the short term (evolving cancer, non stable cardiopathy, hepatic, renal or respiratory insufficiency) * contra-indications for MRI, PET or SPECT scans * not affiliated with a social security regimen