FIG. 9.

Decreasing outer hair cell (OHC) gain can improve discrimination in noise and widen the dynamic range for individual auditory nerve fibers. Discriminability (d') for a 5-dB increment in tone level is shown for a high spontaneous rate fiber with a characteristic frequency of 8 kHz. The thin dashed line shows results when the OHC gain is full on (i.e., ∆G = 0 dB, simulating the no-MOCR condition). The solid and dashed lines with increasing thickness show results as OHC gain is decreased to simulate the MOCR. The noise level increases across panels. A d' of 1 was designated as threshold, shown by the horizontal dotted line. Filled and open triangles show physiological data from Kawase et al. (1993) without and with the fixed-level contralateral noise, as in Figure 6.