MAPT and Alzheimer disease: Finally, in a study by Mattsson et al. that also utilized the 18F-AV-1451 tau PET ligand, again on a mixed group of MCI and AD patients (65 patients total), the authors reported an increased tau load in the entorhinal cortex (relative to the whole cortex) of APOE4+ patients compared to APOE4− patients, whereas the tau load in the parietal and occipital lobes was higher in APOE4− patients compared to APOE4+ patients [90].