MAPT and Cognitive impairment: While tauopathies present as a heterogenous mixture of paired helical filaments, straight filaments, twisted ribbons and oligomeric aggregates in the AD brain, oligomeric tau has recently emerged as the current research focus, owing to its strong cytotoxic effect in preclinical models and its prominence in early stages of AD and mild cognitive impairment (MCI) (Mufson et al., 2014; Guerrero-Muñoz et al., 2015).