MAPT and Alzheimer disease: Emerging evidence from post-mortem brains (DeVos et al., 2018) and positron emission tomography (PET) scans (Franzmeier et al., 2020; Hoenig et al., 2018; Jones et al., 2017; Vogel et al., 2020) from individuals with AD have begun to hint that tau spreads through functionally connected neural networks in human brains; however, most of that data are correlative.