Figure 3. Normal fiber input-output curves and latencies vary with stimulus waveform.

(A) response probability, averaged over 500 Monte Carlo trials, of normal simulated fibers to varying current intensities of cathodic monophasic, anodic monophasic, cathode-first biphasic, and anode-first biphasic stimuli (markers). These response profiles are fit with a CDF (lines). (B) Input/output functions using similar stimuli produced from recordings from spiral ganglion central axons in response to intracochlear electrical stimulation by Shepherd and Javel in 1999 for comparison (reprinted with permission). (C) Mean latency between stimulus onset and action potential arrival at node 32 is plotted as a function of stimulus current for each of the 4 stimulus waveforms applied to normally myelinated fibers (n = 500 monte carlos). Error bars represent jitter, the variance of the latency distribution. Solid markers and lines correspond to monophasic stimuli while empty markers and dashed lines correspond to biphasic stimuli. Black markers and lines indicate waveforms with cathode leading phases while red ones indicate anodic leading phases. (D) Latency-intensity functions for responses to monopolar stimuli recorded from cats by Miller and Colleagues. Monophasic pulses (top panel) were 39 μs in duration while biphasic stimuli (bottom panel) were 100 μs/phase with no interphase gap. Cathodic monophasic and CF stimuli plotted as filled markers while anodic monophasic and AF plotted as open markers. AF latencies separated into long (open circles) and short (open squares) populations. Adapted, with permission, from Miller et al., 1999.