Tau pathology is found in the medial temporal lobe (MTL) of most older adults, even those without cognitive impairment (Crary et al. 2014), but its accumulation in other areas of the cortex is thought to represent a transition to Alzheimer's disease and is associated with neurodegeneration and cognitive decline (Aschenbrenner et al. 2018; Iaccarino et al. 2018). This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.