Fig. 4. Older adult (10–12 months age) Met^cKO mice showed impaired MWM spatial memory learning.

(A) Older adult Met^cKO mice showed faster learning during the 8-day acquisition phase (Ctrl, N = 12; cKO, N = 12. group factor, F_(1,22) = 71.2, p < 0.0001), with Day 5 through Day 8 exhibited statistically significant differences (** p < 0.01, * p < 0.05, two way rmANOVA with post hoc Sidak’s MCT). (B) Met^cKO mice spent similar amount of time near the pool wall area during the 8-day training, as indicated by the percent of thigmotaxis time. Main effect of group, F_(1,22) = 3.67, p = 0.07). Inset, Met^cKO mice also showed similar swim speed. Ctrl, 8.60 ± 0.49 cm/sec; cKO, 8.09 ± 0.62 cm/sec. t₍₂₂₎ = 0.64, p = 0.53. (C) Met^cKO mice show significantly less time in the target quadrant during probe trial (Ctrl, 45.1 ± 1.87 sec, N = 12; cKO, 33.2 ± 2.01 sec, N = 12. t₍₂₂₎ = 4.33, ***p = 0.0003, unpaired t test); and significantly decreased number of platform crosses (Median (range) for Ctrl, 3.0 (1.0–6.0) crosses; cKO, 1.0 (0–3) crosses, N = 12 for both groups. p = 0.007, Mann-Whitney U test). (D) Met^cKO mice exhibited faster learning during the reverse training phase. F_(1,20) = 10.79, p = 0.0037 for the group effect, two-way rmANOVA. A significantly longer time was needed to locate the new platform at day 11. p = 0.017, post hoc Sidak’s MCT. (E) Met^cKO mice spent less time in the new target quadrant location (Ctrl, 55.3 ± 3.28 sec; cKO, 44.2 ± 2.12 sec. p = 0.0005, two-way rmANOVA with post hoc Sidak’s MCT) and more time in the opposite quadrant (Ctrl, 10.8 ± 3.3 sec; cKO, 21.5 ± 2.5 sec. p = 0.0025).