Neuroimaging Core Abstract The ABC-DS Neuroimaging Core, led by Drs. Adam Brickman and Brad Christian, will apply state-of-the art positron emission tomography (PET) and magnetic resonance imaging (MRI) neuroimaging techniques to quantitate amyloid, tau, and neurodegeneration (AT(N)) in Down syndrome (DS) according to current pathophysiological models of Alzheimer’s disease (AD) together with related cerebrovascular, microstructural, and functional biomarkers. The specific aims of the Neuroimaging Core are to: (1) oversee the harmonized acquisition of PET and MRI data at each of the 8 clinical performance sites; (2) quantitate primary outcome measures for each neuroimaging modality; (3) integrate the processed neuroimaging data into a ABC-DS database to support the proposed projects; and (4) provide curated primary outcome variables and raw neuroimaging data to the wider scientific community. The overall scanning protocols will follow those developed by the Alzheimer’s Disease Neuroimaging Initiative (ADNI) for MRI (structural and functional) and PET (amyloid, tau, FDG). The outcome variables are derived by modality-specific analytic nodes, with each modality analyzed by a single laboratory with expertise in that neuroimaging biomarker. The Core will utilize NIA-sponsored resources that currently support ongoing large-scale AD neuroimaging initiatives (e.g. ADNI, Dominantly Inherited Alzheimer Network (DIAN)) to provide a fully developed data-access pipeline that encourages scientific investigation of neuroimaging biomarkers in DS.