MAPT and Alzheimer disease: Two studies (Ikeda, Haga, & Kosaka, 1990; Yamaguchi, Nakazato, Shoji, Takatama, & Hirai, 1991) indicated that premature, diffuse amyloid plaques were present in the frontal lobe of AD patients, while more mature plaques were located in the temporal lobe; from these results, we hypothesized that mature plaques likely interacted with tau protein to produce negative effects.