 Medical or psychiatric disorders that might complicate the assessment of dementia i.e., mental retardation, alcohol abuse, drug abuse, HIV A disability that may prevent the subject from completing all study requirements e.g., blindness, deafness, language difficulty Recent intake of drugs known to cause major organ system toxicity or CNS alteration e.g. sedation Diseases of the dementia type other than AD i.e., vascular dementia, frontotemporal dementia, Lewy Body Disease, Huntingtons disease Presence of non-MRI compatible implantsdevices Prohibited Medications: Warfarin or other anticoagulants for subjects that choose to provide a CSF sample by lumbar puncture, investigational agents. 