Figure 5.

Dose response for the spinal and the hindlimb EMG recordings. A, Average evoked spinal response [ECAP, evoked synaptic activity potential ESAP (S1, S2); upper panel] and average evoked EMG (tibialis anterior hindlimb muscle; lower panel) response from 20 low-frequency pulses of epidural stimulation (Fig. 1A) of spinal cord at varying current intensities, ranging from 200 to 1000 μA, in a representative single rat. Identified waveform components of the spinal response are labeled for 1000 μA, when observable, as P1, N1, P2, N2, S1, and S2 (ESAP). ESAP (S1) becomes more distinct with increasing current intensity. Two types of EMG responses were observed: those occurring before 20 ms, referred to as EMG (blue), and those occurring after 30 ms, referred to as late-EMG (green). B1, Dose–response curve for the ECAP (brown), ESAP (S1; pink), EMG (blue) and late-EMG (green) responses. The left axis represents the amplitude for ECAP and ESAP (S1); the right axis represents the RMS for EMG responses. Each data point represents mean ± SEM (20 trials). B2, Latencies plotted as a function of current intensities. N1 (brown), P2 (black), N2 (dark green), and S1 (ESAP, pink). Latency for the EMG and late-EMG is defined as the latency of the first peak in the EMG/late-EMG response. Data represented as mean ± SEM. ECAP- Evoked Compound Action Potential; ESAP - Evoked Synaptic Activity Potential; P1, N1, P2 - ECAP waveforms; S1 & S2 - ESAP waveforms. Figure Contributions: Mahima Sharma and Vividha Bhaskar performed the experiments. Mahima Sharma analyzed the data.