The Georgetown University Memory Disorders Program, part of the Department of Neurology, is conducting pilot studies of the feasibility of various diagnostic tests for Alzheimer's disease, mild cognitive impairment and other neurodegenerative diseases. Further, this study is assessing longitudinal changes in biological, lifestyle, and cognitive assessment collection. The primary goal of this study is to examine the feasibility of biochemical assays, genetic testing, and cognitive and lifestyle assessments in the ante-mortem diagnosis of Alzheimer's disease, mild cognitive impairment and other neurodegenerative diseases. This research involves genetic and cognitive status testing but the findings will not be shared with research subjects. This will be accomplished ex vivo using blood, and/or cerebrospinal fluid (CSF) specimens from patients with a diagnosis of probable Alzheimer's disease, mild cognitive impairment, or other neurodegenerative diseases and from normal controls.