MAPT and Alzheimer disease: The levels of two major tau species were measured and these were compared to levels of total tau (henceforth referred to as T-Tau): (1) Tau phosphorylated on Thr231 is one of the key sites phosphorylated in AD, occurring before structural changes to the tau molecule (Luna-Munoz et al., 2005) (henceforth referred to as P-Tau) and; (2) Tau dephosphorylated on Ser 195, 198, 199, and 202 using Tau-1 antibody (henceforth referred to as nP-tau).