FIG. 6.

Spatial learning and memory in the hidden-platform Morris water maze task. (a) Average of the escape latency for each day for hidden-platform Morris water maze training sessions. Four trials were performed each day for 5 consecutive days (n = 20 for each genotype). No difference was observed between the two genotypes, indicating that the mutant mice learned equally well. All data points represent the mean (± standard error of the mean). (b) The probe tests were performed at three different retention time points (1, 4, and 7 days after the last day of acquisition for the hidden-platform task). Different groups of mice were used at each time point. One day after training, no difference was observed between the genotypes (n = 10 for each genotype), indicating that the learning and acquisition of initial memory are normal for NLRR4^−/− mice. Four and seven days after the last training, the time that NLRR4^−/− mice spent in the target quadrant was significantly less than that of wild-type mice. Statistical significance was calculated by the Scheffe's test following two-way analysis of variance. *, P < 0.05. (n = 10 for each genotype and each time point). (c) Swimming speeds were calculated from these movement data. No differences were observed between the genotypes during the training sessions. (d) Time spent in each quadrant of the pool 4 days after training. The time spent by NLRR4^−/− mice in the target quadrant was shorter than that by the wild-type control mice.