FIG. 4.

Simulated rate-level functions for a high spontaneous rate model neuron with a characteristic frequency (CF) of 8 kHz illustrate that outer hair cell (OHC) gain reduction produced anti-masking effects in single AN fiber responses. The tone frequency is at CF, and it is presented in a noise masker that is at 10 dB SL. Dashed lines are the response to the tone + noise (thicker line) or noise alone immediately following the signal (thinner line). Solid lines show responses to the tone + noise (thicker line) and noise alone (thinner line) when the gain of the OHC module is reduced by the ∆G values shown. The maximum driven rate, shown by the vertical arrows, is the difference between the maximum response to the tone + noise and the response to the noise at low tone levels. The vertical bars at the right of each line are the standard deviation across runs for each condition. Note that the saturated rates for these model responses are somewhat higher than expected for AN fiber responses because they represent the spike rate before the effects of refractoriness (see “Methods” section).