Figure 4.

(A) Spontaneous locomotor activity in the open field. Male littermates (12–14 weeks old) were tested for spontaneous locomotor activity by monitoring their movements in 15-min intervals (mean ± SE). No significant differences among Kv3.1^+/+, Kv3.1^+/−, and Kv3.1^−/− animals were observed. (B) Test for coordinated motor skill. Heterozygous and homozygous male littermates (n = 5 each) were placed on a rotating rod, revolving initially at 5 rpm and accelerating at 10 rpm/min. Performances of individual animals over a 4-day period are plotted. Each column of data represents the five trials of the same animal on that day. The order of animals is the same for each day. Kv3.1^+/− mice performed significantly better than their Kv3.1^−/− littermates (P < 10⁻⁶, ANOVA test). (C) The mean performances for each day are plotted for 4 consecutive days. 129SvEMS mice did not learn during the training period, and the initial differences between Kv3.1^+/− (or wild-type) and Kv3.1^−/− littermates remained. In contrast, mice of heterogeneous background [F₂ offsprings of (C57BL/6 × 129SvEMS)F₁ hybrids] improved their performances during the training period; however, the differences between homozygous and heterozygous mutants remained. (D) Active avoidance test. Wild-type and homozygous mutants behaved identically. Before training (i.e., on the first day of the test), Kv3.1^+/+ and Kv3.1^−/− mice avoided electrical footshocks approximately once out of 10 trials. Three days after the 5-day training period, the performance of wild-type and mutant mice had improved several-fold and remained at that level at least for an additional 7 days.