MAPT and Cognitive impairment: Additionally, neuronally derived extracellular vesicles (NDEVs) from patients with mild cognitive impairment (MCI), AD and AD model systems were able to deliver pathological tau to unaffected cells, seed tau aggregation in cell culture and in wild type mice, and induce long-distance propagation of tau pathology (Baker et al., 2016; Polanco et al., 2016; Winston et al., 2016, 2019; Wang et al., 2017).