MAPT and Alzheimer disease: Tau pathology is observed early in the brainstem and entorhinal cortex (Braak et al., 2011), and its progression in the cortex from entorhinal cortex to hippocampus to neocortex corresponds to the progression of AD symptoms (Duyckaerts et al., 1997; Grober et al., 1999; Jucker and Walker, 2013).