MAPT and Alzheimer disease: Fifth, the comparison of the frontal pole in the postmortem study against the medial and lateral frontal cortices in the tau PET study may introduce a bias, as these regions have been differentially implicated in behavioural disturbances.41 Sixth, although we did not specifically focus on the dysexecutive variant of AD in this study, executive deficits comprised one of the 6 core phenotypic inclusion criteria.