MAPT and memory impairment: Interestingly, these studies suggest that possession of APOE4 does in fact result in phenotypic differences between APOE4+ vs. APOE4− AD patients, with APOE4+ AD patients appearing to possess relatively more tau accumulation and brain atrophy in the medial temporal lobe, resulting in greater memory impairment, than APOE4− AD patients, while APOE4− AD patients appear to possess relatively more fronto-parietal lobe tau accumulation and brain atrophy, resulting in greater impairment in executive function, visuospatial abilities, and language, than APOE4+ AD patients (Fig. 1).