Effect of genotype and age on gait.

<p>Data are expressed as mean ± SEM of the following number of each age and genotype: young (wt = 8, ko = 9), middle-aged (wt = 11, ko = 14) and old (wt = 18, ko = 23) male mice. Asterisks above bars indicate significant difference between age-matched wt and ko groups. Asterisks above lines indicate significant difference between indicated means. *<i>P</i><0.05; **<i>P</i><0.01; ***<i>P</i><0.001.