MAPT and Alzheimer disease: In the cortex part, the expression of Aβ42 oligomer was increased significantly in the whole cerebral cortex, but not in the hippocampus, of the exposure group as compared with the control group (P < 0.05); but with only a trend and without a significant difference appearing in P-tau, the other pathological target protein of Alzheimer disease, between the two groups (Fig. 7).