Balance beam balance performance of WT and YAC128 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-walking performed with 11 mm round beam (A, B), and 5 mm square beam (C, D). The data for WT control (Ctrl) mice (open blue circles), YAC128 (YAC) control mice (filled blue circles), WT mice fed with Early-TBZ (open red squares), YAC128 mice fed with Early-TBZ (filled red squares), WT mice fed with Late-TBZ (open black triangles), and YAC128 mice fed with Late-TBZ (filled black triangles) are shown as mean ± SEM at 2, 6, 8, 11 and 13 month time points. Control YAC128 mice exhibited a progressive impairment in beam-walking ability with age and beam difficulty compared with control WT mice. The significant differences (p < 0.05) between control YAC128 and control WT groups were observed at 9, 11 and 13 months of age on 11 mm beam; and at 6, 9, 11 and 13 months of age on 5 mm beam. Feeding TBZ to WT mice had no significant effects on beam performance compared to control WT group. Early-TBZ feeding significantly (p < 0.05) improved the beam performance of YAC128 mice at 9, 11 and 13 months of age on 11 mm beam, and at 6, 9,11 and 13 months of age on 5 mm beam. Late-TBZ feeding also significantly (p < 0.05) improved the beam performance of YAC128 mice at 9, 11 and 13 months of age on both 11 mm and 5 mm beam.