MAPT and Mental deterioration: Two of the most remarkable features of AD are: (i) the stereotypic pattern of Aβ and tangle spreading through interconnected areas of the brain (Braak and Braak, 1991) that is closely related to cognitive decline years before the onset of clinical symptoms; and (ii) the ability of pathogenic misfolded Aβ and tau to serve as templates to convert their innocuous counterparts into toxic forms in a prion-like manner (Clavaguera et al., 2009; Jucker and Walker, 2011, 2013).