These tracers have been shown to be largely specific for the mixed 3R/4R PHF tau pathology characteristic of AD and Down syndrome and have helped further our understanding of tauopathies as well as the relationships among Aβ, tau, neurodegeneration, and cognitive decline in AD.4, 5, 6, 7, 8, 9, 10, 11. Here, MAPT is linked to Down syndrome.