The main objective of this research project is to provide a comprehensive clinical database of patients with Alzheimer's disease (AD) and other forms of dementia, individuals with mild cognitive impairment (MCI), and age-matched normal controls. The study will also attempt to identify cognitively normal individuals at genetically defined risk for Alzheimer's disease through genetic screening.

All participants are seen annually. Autopsies to establish diagnoses in patients with dementia, patients with mild MCI, and cognitively normal elderly control subjects will also be conducted.

All participants are seen annually. In addition to a detailed neurological examination, participants will receive a standardized battery of neuropsychological tests and will undergo genetic testing. The investigators will provide standardized periodic longitudinal assessment of the research participants. Autopsies to establish neurohistopathological diagnoses in clinically well-characterized patients with dementia, patients with mild MCI, and cognitively normal elderly control subjects will also be conducted.

Inclusion Criteria:

For patients with MCI, or dementia, the presence of cognitive deficits including memory, language, and executive function.

Exclusion Criteria:

Presence of non-neurological medical conditions interfering with cognition.

Individuals with Alzheimer's disease, mild cognitive impairment, other forms of dementia, and normal elderly individuals.