The study will use a combination of functional, structural, and cognitive measures to detect early effects of amyloid deposition, and will utilize PIB retention in order to characterize the relationship of amyloid to neuropsychological and imaging markers of prodromal AD. The relationship of PIB retention to genetic, plasma and cerebrospinal fluid (CSF) biomarkers will be explored. These preliminary data will be used to determine whether asymptomatic older individuals with high amyloid burden will subsequently manifest cognitive impairment and eventually progress to clinical AD. When completed, this project will either provide evidence that the presence of amyloid deposition is a useful biomarker for incipient AD or raise the possibility that amyloid deposition examined in isolation is insufficient to predict early symptoms and progression of AD.