MAPT and Cognitive impairment: Furthermore, [18F]AV1451 PET demonstrated cortical retention consistent with the known distribution of tau (Xia et al. 2013; Arnold et al. 1991; Schwarz et al. 2016) and a strong association with dementia severity and cognitive impairment (Ossenkoppele et al. 2016; Cho et al. 2016) (Fig. 1).