APOE and Cognitive impairment: In terms of brain imaging evidence, studies using the tau PET tracer 18F-AV-1451, also known as 18F-flortaucipir, showed contradictory results, ranging from an association between medial temporal tau and apoE4 independently of Aβ in cognitive performance [407]; to establishing no association between medial temporal tau and apoE4 in cognitively normal individuals, mild cognitive impairment (MCI) or AD patients [408, 409].