MAPT and Cognitive impairment: In their study, Quiroz et al. [45] revealed that increased levels of tau were observed in medial temporal lobe areas in carriers of unimpaired PSEN1 E280A mutation in their late 30s, and that noticeable formation of tau tangle in neocortical areas was seen in one cognitively unaffected carrier as well as in individuals with mild cognitive impairment.