(A) The design of the fine odor discrimination test. Mice were deprived of water for 2 days and trained to identify distilled water. The distilled water was coupled with an odor mixture of mango and almond; however, mango was the main component. In another dish, bitter water was coupled with a mixture in which almond was the main component. Different proportions of the odors were used for the performance test. (B) Test performance of young (3- to 4-month-old) WT and Wip1-Tg mice shows no differences in fine odor discrimination. Data are mean ± SEM. (C) Test performance of old (16- to 18-month-old) WT and Wip1-Tg mice shows a significantly better fine odor discrimination of Wip1-Tg. Data are mean ± SEM. (D) Representative images and quantification of EdU labeling (2-hour pulse) of neural progenitors. Mice were treated with AraC for 1 month (described in Methods). Insets show colabeling of EdU, DCX, and DAPI. Note a decrease in both EdU- and DCX-positive cells in AraC-treated mice. Data are mean ± SEM. (E) Representative images and quantification of EdU-positive cells 1 month after EdU labeling in control mice and in mice treated with AraC. AraC treatment started right before EdU injection. Data are mean ± SEM. (F) Test performance of AraC-treated and control 1-year-old Wip1-Tg mice. Note that there is a significant reduction in performance after AraC treatment. Data are mean ± SEM. *P < 0.05; ***P < 0.005. Scale bar: 200 μm (D and E); 100 μm (D, inset); 40 μm (E, inset).