While the intraneuronal physiological concentration of tau is ~2 μM (Avila, 2010), extracellular tau concentrations in the cerebrospinal fluid (CSF) are 279–596 nM in AD patients and 29–134 nM in cognitively normal, age-matched controls (Tato et al., 1995; Han et al., 2017). This evidence concerns the gene MAPT and Alzheimer disease.