Contextual and cued fear memory in NLRR4−/− mice. (a) Freezing ratio for contextual fear at different retention delays for NLRR4−/− and wild-type mice (n = 13 for each genotype and each time point). No difference was found in the time spent on freezing behavior after 1 day of retention (wild-type, 58.7 ± 15.1%; NLRR4−/−, 59.5 ± 12.6%). Freezing behavior was significantly reduced in the NLRR4−/− mice after 4 days (wild-type, 59.5 ± 12.6%, NLRR4−/−, 20.1 ± 11.3%, Student's t test P < 0.001) and 7 days retention (wild-type, 57.2 ± 17.5%; NLRR4−/−, 17.8 ± 9.8%, Student's t test, P < 0.001). All data points represent the mean (± standard error of the mean). *, P < 0.001; **, P < 0.001. (b) Normal pain sensitivity of NLRR4−/− and wild-type mice. Pain sensitivities were calculated by the total pixels that mice moved before and after electric foot shock. All data points represent the mean (± standard error of the mean). (c) Percent of freezing time at preconditioned or conditioned stimuli after cued fear conditioning for NLRR4−/− and wild-type mice. Tests were performed 4 and 7 days after training. No significant difference between the genotypes was found for either time points (day 4 after training: wild-type, 45.1 ± 12.5%; NLRR4−/−, 49.2 ± 13.4%; day 7 after training: wild-type, 66.4 ± 20.7%; NLRR4−/−, 57.4 ± 27.7% [n = 10 for each genotype and each time point]). All data points represent the mean (± standard error of the mean).