Figure 3.

Induction of a stumbling corrective reaction is independent of proprioceptive sensory feedback from the muscle spindles. A, Hip, knee, and ankle joint angles, relative toe x- and y-coordinates (toe height) synchronized with raw EMG activity of flexor (Ip, St, TA) and extensor (VL, Gs) muscles. Electrical stimulation of the saphenous nerve during swing phase is indicated by the darker gray region inside the third swing phase. Green arrows point to the activity of the flexor muscle elicited by the stimulation. Stick diagram reconstruction of a swing phase before SCR (i), an SCR (ii), and a swing phase after SCR (iii) are illustrated below. B, Trajectories of the hindlimb paw during SCR are very stereotyped in wild-type animals (top) but are disorganized in Egr3-KO mice (bottom). The colored lines are individual swings, and the bold line is the pooled average from one animal. The average posterior paw position at swing onset and the anterior paw position at swing offset are illustrated as open and closed circles, respectively. The point of nerve stimulation is indicated by the gray circle. C, Changes in control swing and SCR durations (p = 0.016) and distances between the paw position from liftoff to touchdown (swing amplitude) in SCR events in wild-type mice (p < 0.001). No changes were observed in swing duration (p = 0.074) and swing amplitude (p = 0.534) during SCR events in Egr3-KO mice.