This is a renewal of Program Project P01AG04953. It represents a closely integrated series of studies on the cognitive and neurophysiological concomitants of the early stages of Alzheimer's disease (AD). The Central hypothesis of the research program is that AD follows a lengthy tracjectory before full blown symptoms are evident and that, in late-onset cases, disease is the result of multiple converging factors. By merging the measurement of several aspects of cognition and brain function, patients in the very earliest stages of AD can be identified with considerable accuracy. Three interrelated areas are included: Neuropsychological assessment (Project 1), single photon emission computed tomography (SPECT) (Project 2) and functional magnetic resonance imaging (fMR) (Project 3). Four cores will provide essential support to the projects: The Administrative and Clinical core (Core A) will be responsible for subject recruitment, evaluation, and follow-up, the Data Management and Statistical Core (Core B) with maintain a Core Data Base and complete complex statistical analyses; the Genetics Core (Core C) will provide genotyping and the Image Analysis Core (Core D) will perform MRI image analysis relevant to the other projects.