Fig. 2

Data from the preliminary animal showing the proximal stimulation maintained throughout the trials (a, b, gray bars at top of each figure) and matching trials where the proximal stimulation was stopped before the ramp (c, d). At a Sub_Block level of 50% there is no block (a, b, c, d). Zero ramps produce secondary onset (a, c, grey arrows) and are the control trials in every group of trials. A ramp of 1.25 s still produces a tiny secondary onset that is partially obscured by the proximal twitches (b) but is visible and measurable in “D” (circles). This figure shows why proximal stimulation was stopped before the ramp for the definitive trials. It shows that complete block was obtained in the Post_Sub_Block phase and demonstrates that the proximal stimulation does not enhance the onset response (b, d), but in fact can obscure it. The decreasing twitch heights seen in B are examples of partial block, in which only some of the motor fibers are blocked