Because the spread of NFTs, indicated by increasing Braak stages (Figure 1A), correlates more strongly with cognitive decline in AD than extracellular Aβ pathology, it is hypothesized that propagation of tau aggregates contributes to the dendritic spine or synapse loss (Braak et al., 2006; Scholl et al., 2016). This evidence concerns the gene MAPT and Alzheimer disease.