Compound action potentials (CAPs) evoked by conventional electrostimulation and by 12-ns PEF. (a) nsPEF elicit CAPs similar to conventional stimuli, but are selective for the excitation of fast fibers. Shown are CAP traces evoked by nsPEF at three different pulse voltages (solid lines) and by conventional stimulation (dashed line; stimulation parameters are given in the legends). Note that nsPEF at 7.2 kV elicits slightly larger response of the fastest fibers (Aα, first peak) than 250 µs, 2 V stimulation (330 and 300 µV, respectively) while the response of slower fibers (Aβ, the second peak) is 9-fold smaller (7 and 65 µV). (b) A 1-min, 100 stimuli/s tetanus using 12-ns, 11.6 kV pulses did not cause nerve damage. During the tetanus, CAP expectedly became smaller (central panel), but after a 1-min rest CAP evoked by conventional stimulation (right panel) was the same as before the stimulation (left panel; also shown by a dotted line in the right panel).