Fig. 2

L2–L5 interneurons are dispensable for intralimb coordination during locomotion. Representative illustrations of intralimb movements during a control and c DOX^ON stepping, as described by three hindlimb segments (iliac crest–hip, hip–ankle, and ankle–toe) and two hindlimb angles (proximal (blue): iliac crest–hip–ankle angle, distal (purple): hip–ankle–toe angle). Proximal and distal angles are shown for five select instances throughout one step cycle. b, d Two-dimensional stick figures of hindlimb stepping at Control and DOX^ON time points, respectively (from the same stepping passes shown in (a, c); sampling rate = 100 Hz). Silencing L2–L5 interneurons increased vertical movements in the hip (d, black horizontal trace) while preserving normal hindlimb range of motion (Supplementary Figure 2). Onset times of peak angular excursions (e–h, blue and purple hashmarks) were analyzed to assess the temporal coordination between proximal and distal angles (see Methods for detail) (traces = excursions of proximal and distal angles; shaded region = stance phase; 0/1 in circular plot denotes normal, in phase coordinated movements; individual circles = intralimb coordination value for one step cycle; LHL left hindlimb; RHL right hindlimb). i Proximal-to-distal intralimb movements of the left and right hindlimb (as well as between limb pairs) remained unaffected during silencing (n = 130 and 150 intralimb cycles for collapsed Control and DOX^ON time points, respectively; white inset = normal variability at control time points). All comparisons in (i) were p > 0.5 (Watson’s nonparametric two-sample U ² test; LHL: Control vs. DOX^ON U ² = 0.04232; RHL: Control vs. DOX^ON U ² = −0.13874; Control: LHL vs. RHL U ² = −0.00653; DOX^ON: LHL vs. RHL U ² = 0.01623; Control LHL vs. DOX^ON RHL: U ² = 0.04225; Control RHL vs. DOX^ON LHL: U ² = 0.04232). Illustrations by A. Pocratsky