Fig. 6.

Spinal cord stimulation (SCS) evokes direct and indirect primary afferent recruitment at comparable thresholds. SCS was applied contacting (0 μm; A) or 200 µm above (B) T9/T10 during recording of a lumbar dorsal root (DR). Stimulus amplitude was incrementally increased (1–200 µA, 200 µs; i), and the recruitment threshold for direct primary afferent recruitment and synaptically mediated primary afferent activity (indirect) was identified post hoc (ii). Mean threshold (x̄) for indirect recruitment was not significantly higher than that observed for direct recruitment when SCS was applied contacting (0 μm; n = 4 animals, 15.2 ± 10.1 vs. 13.0 ± 6.9 μA, respectively) or 200 µm above (n = 5 animals; 49.8 ± 48.3 vs. 48.0 ± 52.3 μA, respectively; Aii and Bii, paired t test). Arrows indicate direct recruitment, dashed boxes denote indirect recruitment, and shaded boxes depict stimulation artifact. Black lines are the average of 6 traces.