Training-Specific Neural Plasticity in Spinal Reflexes after Incomplete Spinal Cord Injury

Figure 2

The cutaneomuscular reflex (CMR) during walking in a single participant. Average EMG traces from the soleus (a) and tibialis anterior (b) muscles, time-locked to the beginning of the stimulus (time = 0), are shown for the 8 bins of the walking cycle from participant P12 after subtraction of the background EMG during unperturbed walking. The number of acceptable reflexes within each time bin (bin number) across the step cycle is indicated on the far right. Data were obtained after the first rest period (i.e., at Month 4) prior to Endurance Training. Triple pulses (200 Hz; 0.3 ms pulse width; at ~1.5x motor threshold for the abductor hallucis brevis (AHB) muscle) were applied to the posterior tibial nerve behind the medial malleolus during walking on a treadmill. Responses displayed are matched for M-wave amplitudes, measured from the AHB (see Data Analyses for details). Responses for each of the 8 bins of the walking cycle were quantified by averaging the EMG between vertical dashed lines in (a) and (b) and plotted as a function of time in the walking cycle in (c) and (d). Correspondences of the bin numbers with stance (ST) and swing (SW) phases are shown by the solid and open bars, respectively, at the bottom of the graphs. Horizontal arrows in (c) and (d) indicate maximum inhibition and excitation.