(A) Schematic of the LocoMouse setup with two dark boxes, glass corridor, motion sensors, high speed (400fps) camera, and mirror. Mice freely cross the corridor. (B) An example of side and bottom views captured in a single via mirror reflection. Continuous tracks (in x, y, z) for nose, paws and tail segments obtained from LocoMouse tracking are plotted on top of the frame. (C) Sagittal sections of mouse cerebellum from littermate control (left) and a reeler mouse (right) illustrate dramatic cerebellar reorganization in reeler. (D) Histogram of walking speeds for reeler (green N = 7 mice, n = 2439) and littermate controls (grey, N = 12, n = 2515). Walking speed distributions are significantly different, reelers mice walk slower (ind. t-test p=<0.001***). (E–G) Stride length (E), cadence (F, 1/stride duration) and stance duration (G) of the front right (FR) paw vs walking speed for reeler (green) and littermates (grey). For each parameter, thin lines with shadows represent median values ± 25th, 75th percentiles. Thick lines represent the predictions calculated using the equations previously derived from the mixed-effect models described in Machado et al., 2015. No significant difference was observed between littermate controls and reeler mice (main effects: stride length: F1,90=2.16, p=0.14; cadence: F1,90 = 0.7, p=0.4; stance duration: F1,90=2.97, p=0.09). (H) Average instantaneous forward (x) velocity of FR paw (top) and hind right (HR) paw (bottom), normalized to the swing phase. Line thickness represents increasing speed. Reeler (green), size-matched controls (black; N = 11; n = 3412). Reeler mice showed sig. higher avg. swing velocity (F1,104 = 4.59, p=0.03), but no difference in peak inst. velocity (F1,104 = 0.87, p=0.35). Hind paws showed lower peak velocity than size-matched controls (F1,103 = 14.1, p=<0.0001). (I) side-to-side (y)-excursion for FR and HR paws, relative to body midline. There are changes in peak to peak trajectories for both paws (FR: F1,96=197.4, p=<0.0001; HR: F1,103=353.9, p=<0.0001). (J) Average vertical (z) position of FR paw (top) and HR paw (bottom) relative to ground during swing. Reelers mice have larger vertical movement than size-matched controls (FR: F1,96=205.5, p=<0.0001; HR: F1,103=11.9, p=<0.0001). (K) x-y position of four paws relative to the body center during swing for reeler and size-matched controls. There was no significant difference in width of base of support (F1,101=2.4, p=0.12).