CROSS-SECTIONAL OBJECTIVES~To measure 18F-RO6958948 retention in selected participants of ALFA-related studies as a function of amyloid levels.~To study the relation between 18F-RO6958948 retention and amyloid levels.~To characterize imaging correlates as a function of tau and amyloid levels.~To study the role of tau retention on cognitive performance.~To define predictors of tau retention.~LONGITUDINAL OBJECTIVES~To measure tau accumulation and spreading in participants of the ALFA-related studies of BBRC as a function of baseline amyloid levels.~To study the dynamic relation between tau spreading and amyloid levels longitudinally.~To define predictors of tau spreading.
This study will characterize tau tracer retention by Positron Emission Tomography (PET) as a function of amyloid levels transversally and longitudinally.