9 msec) and fires at higher amplitude compared

to 7 days. There is notable variability in ST2 firing patterns, as ST2 duration was on average +33.6 ± 46.13% longer at 21 days (Fig. 6). In low (BBB = 16), but not high performing animals, ST2 activation occurs with knee flexion instead of extension during yield (Fig. 5). To determine whether differences in ST2 duration were linear with recovery, burst durations were normalized (percent change postinjury) and correlated with open field BBB scores. A high correlation between ST2 burst duration and BBB scores (r2 = 0.9697; P < 0.05) indicates that smaller changes in burst duration occur in high-performing animals (Fig. 8). Figure 7 Average burst Inhibitors,research,lifescience,medical duration relative to stance onset. Burst durations were measured relative to stance onset Inhibitors,research,lifescience,medical (“0”) and averaged before (solid) and 21 days (hatched) after injury. Average EMG onset and offset times are marked by the beginning ... Figure 8 ST2 burst duration predicts click here recovery in the open field. Normalized burst durations

were correlated with BBB scores ranging from 15 to 19. TA, LG, and ST1 display shortened burst durations relative to normal that do not correlate with open field performance … Changes in ST reflect task specificity To determine whether different forms of TM locomotion alter muscle recruitment after SCI, we compared flat or 10% downslope Inhibitors,research,lifescience,medical grade TM walking in the same animals. Similar to 7 days and 21 days, flat TM walking at 13 days showed delayed activation of ST1 and shorter-burst durations relative to normal. Inhibitors,research,lifescience,medical During flat walking, a single prolonged burst with an indiscriminate reset period occurs in ST and ST2 is negligible (Fig. 9). TM walking at a downslope grade required a different recruitment pattern that was identified by changes in the ST. Downslope walking

produced later, and less activation of TA for ankle dorsiflexion and recruitment of LG was unchanged (data not Inhibitors,research,lifescience,medical shown). In the ST, downslope walking re-established a dual-burst pattern (Fig. 9). Notably, ST2 fired at a greater amplitude with a more defined onset/offset period during downslope walking than flat TM walking (Fig. 9). While downslope walking produced a reset period between ST1 and ST2 within the time period described for Naives, the muscle was not silent. Figure 9 Task-specific changes in locomotion alter below ST recruitment after mild SCI. EMG recordings are shown for the same animal as Naive, and 13 days after injury while walking on flat or 10% downhill TM surface grades. Stick figure diagrams at 60 Hz show a representative … Discussion Overview of the current study The current work identifies fundamental components of locomotor control that are impaired after recovery from SCI. Despite rapid improvements acutely after injury, deficits persist and normal locomotion does not return by chronic periods.