Figure 7. The Psen1 c.548G>T KI/KI mice in the Psen2-null background exhibit mild spatial memory impairment. A–D, Psen1 c.548G>TKI/KI and littermate wild-type control mice at 18–20 months of age were subjected to training in the hidden platform water maze for 12 d (four trials a day) followed by four trials of training in the visible platform version of the task. The escape latency (A) and swimming speed (B) of KI/KI mice (n = 5) are similar to that of littermate controls (n = 7) during the 12 d training phase of the hidden platform water maze task. C, KI/KI and littermate control mice also displayed similar quadrant occupancy in the post-training probe trial administered 24 h after the final training session. D, The escape latency in the visible platform version of the task is normal in KI/KI mice. E–H, Psen1 c.548G>T KI/KI;Psen2−/− and littermate control mice at 6–8 months of age were subjected to training in the hidden platform water maze for 12 d (four trials a day) followed by four trials of training in the visible platform version of the task. E, F, The escape latency (F = 0.032; df = 1, 17; p = 0.8601) and swimming speed (F = 3.549; df = 1,17; p = 0.0768) of Psen1 c.548G>T KI/KI;Psen2−/− mice (n = 11) are similar as littermate controls (n = 8) during the 12 d training phase in the hidden platform. G, However, during the probe trial 24 h after the final training session at day 12, Psen1 c.548G>T KI/KI;Psen2−/− mice show significant reduction in quadrant occunpancy (p = 0.0267), suggesting mild impairment of spatial memory. H, Psen1 c.548G>T KI/KI;Psen2−/− mice performed normally in the visible cue task. AL, Adjacent left quadrant; T, target quadrant; AR, adjacent right quadrant; OP, opposite quadrant. All data are expressed as mean ± SEM. *p < 0.05.