Project 1: Project Summary/Abstract The Adult Children Study (ACS) is an ongoing evaluation of middle to older adults at risk for development of Alzheimer disease (AD). In Project 1 of the ACS, we use a combination of advanced imaging techniques to explore the earliest signs of AD pathology. Using positron emission tomography (PET) we test for amyloid and tau protein deposits in the brain, using Pittsburgh Compound B C11 (PiB) and Flortaucipir F18 (FTP) and we examine brain structural networks, pathology and physiology using magnetic resonance imaging (MRI). While amyloid deposits can be present up to 20 years before dementia symptoms, tau deposits are closely linked with cognitive decline. We will evaluate the structural and functional changes in the brain associated with the transition from the asymptomatic (preclinical) phase of AD into the symptomatic stages of AD dementia. We will generate unique brain maps for each imaging modality and we will then examine these maps in relation to one another, to develop an integrated understanding of the imaging changes which occur during the transition from asymptomatic and symptomatic AD. We will combine this information with information about lifestyle, exercise, diet, inflammation, and blood and cerebrospinal fluid (CSF) tests obtained in the other ACS Cores and Projects in order to better understand what factors lead to AD dementia.