MAPT and Alzheimer disease: The work by Sato et al. helped to change our understanding of tau in AD; the increase in total‐tau and phosphorylated‐tau seen extracellularly in AD represents an active secretion of phosphorylated and non‐phosphorylated N‐terminal tau fragments from live neurons exposed to Aβ, not passive release from dying neurons (Zetterberg, 2018).