MAPT and Alzheimer disease: We propose that tau PET did not identify the relatively high tau burdens seen in the neuropathological assessment of CA1 and the parahippocampal gyrus because, at the level of the lateral geniculate nucleus, these areas develop far more robust tauopathy only in late stages of AD neuropathological change,15, 16 that are more likely to be associated with a terminal Clinical Dementia Rating of 3 than 0.5 or 1.