Beam walk performance of YAC and WT mice. The average time to cross the beam (A, C) and the average number of foot slips on the beam (B, D) are shown for beam walk experiments performed with 11 mm round beam (A, B) and 5 mm square beam (C, D). The data for WT mice (open circles, n = 11) and YAC mice (filled circles, n = 15) are shown as mean ± SEM at 2, 4 and 6 month time points. *p < 0.05; **p < 0.01; ***p < 0.001.