Figure 7. Dependence of correlogram magnitude and delay on “ILD”. Abscissa: “ILD”, using 70 dB SPL as reference. Upper panels are for fibers with CF < 3.8 kHz. Lower panels are for fibers with CF > 3.8 kHz. A, B, Ordinate: correlation index (CI) i.e., the maximum of the correlogram normalized for the number of spikes. CI = 1 indicates the number of coincidences as expected from chance. Each line joins measurements on one fiber. While the CI tends to be maximum at 0 “ILD” in low-CF fibers, it decreases with increasing “ILD” in high-CF fibers. Note the difference in ordinate scale between A and B. C, D, Ordinate: delay of the primary peak of the correlogram. Negative values (i.e., lead of the reference level of 70 dB SPL) are plotted upward. At negative “ILD”, i.e., lower SPL than the reference SPL of 70 dB, the responses at 70 dB generally lead relative to the (lower) test SPL. At positive “ILD” the responses at 70 dB generally lag relative to the (higher) test SPL, but at low CFs (C) many “paradoxical” latency shifts are observed. The data highlighted with a thick gray line and white “x” symbols illustrate measurements for the two fibers of Figure 3. The data are calculated on splined difcors for the low CF data (A, C, N = 175 fibers) and on splined sumcors for the high CF data (B, D, N = 40 fibers).