Light/dark test. Bars represent (A) the latency to enter, (B) the percentage of time spent in the dark compartment (C) and the number of light/dark transitions by C57BL/6J (n = 10) and C57BL/6N (n = 9) male mice, aged 8 to 10 weeks. Data are mean ± SEM, *P < 0.05 (t-test). (D) Rotarod motor learning performance over 4 days. Symbols and lines represent daily latencies (mean ± SEM) to fall from rotating rod at acceleration from 4 to 40 rpm in 300 seconds by C57BL/6J (n = 10) and C57BL/6N (n = 10) male mice, aged 9 to 11 weeks. *P < 0.05, **P < 0.005, ***P < 0.0001 J versus. N (t-test); °P < 0.05, °°P < 0.005, °°°P < 0.0001 versus day 1, Fisher's (least squares difference).