(A) Representative morphological reconstructions of dye-filled IO neurons in wild-type (top) and SCA1-KI (bottom) mice at 14 weeks of age (an early symptomatic timepoint). (B–I) The dendritic arbors of SCA1-KI IO neurons are larger and more complex than wild-type controls. SCA1-KI IO neurons exhibit a greater number of dendritic tips (B) and dendritic bifurcations (C), as well as a marked increase in total dendritic length (D) and Hausdorff dimension (E) (a three-dimensional measure of object complexity). The overall span of IO neurons, shown as height (F), width (G), and depth (H), is largely unchanged between the two genotypes. No change in IO soma size (measured by surface area) was detected between the two genotypes (I). Data are expressed as mean ± SEM. Statistical significance derived by unpaired t-test with Welch’s correction, * = P < 0.05, ** = P < 0.01, ns = not significant. Nwild-type = 9 cells from 7 mice, NSCA1-KI = 10 cells from 7 mice.