ANF density. ANF densities were measured in the middle region of the cochlear tissues from male and female CBA/CaJ mice at 6, 17, and 24 months of age: 6 m (10, 5 males and 5 females), 17 m (10, 5 males and 5 females), 24 m (7, 4 males and 3 females). Data are shown as means ± SEM. Two-way ANOVA with Bonferroni’s multiple comparisons test was performed. m, months of age; M, male; F, female; ANF, auditory nerve fiber.