MAPT and Alzheimer disease: Clinical PET studies demonstrated high and different distribution of [18F]THK-5351 retention in sites susceptible to tau deposition in AD and non-AD conditions such as Parkinsonian syndromes (Harada et al., 2016; Kikuchi et al., 2016; Brendel et al., 2017; Ishiki et al., 2017; Shimizu et al., 2018; Schonecker et al., 2019; Hsu et al., 2020; Ezura et al., 2021; Figure 2).