MAPT and Cognitive impairment: According to the most recent guidelines (McKhann et al. 2011; Dubois et al. 2014), AD can be diagnosed before the appearance of any cognitive or behavioral symptoms, i.e., in a preclinical (before any objective cognitive deficit) or prodromal (mild cognitive impairment, AD-MCI) stage (Petersen et al. 2009), based on pathophysiological diagnostic markers revealed by CSF and positron emission tomography (PET) biomarkers of Aβ-1-42 and tau in the brain.