TEMPORAL PATTERNS OF THE RESPONSES OF AUDITORY-NERVE FIBERS TO LOW-FREQUENCY TONES

The temporal response patterns of auditory-nerve fibers to low-frequen cy tones were studied in anesthetized cats using period histograms. 'P eak-splitting' was observed mostly in fibers with lower characteristic frequencies (CF < 2 kHz) and with lower-frequency stimulation (less t han or equal to 500 Hz). The occurrence of peak-splitting, the number of peaks, and the time between the peaks were all dependent upon the s timulus frequency. The phases of responses, although complex functions of stimulus frequency, intensity, and the fiber's CF, clearly showed traveling-wave characteristics for all frequencies at or above 100 Hz. The amount of phase change with intensity was generally small for low er-frequency stimuli (< similar to 50 degrees), although larger phase changes (e.g., similar to 180 degrees) were occasionally seen with hig her-frequency stimuli. At 50 and 100 Hz, the phase of neural responses in the basal region roughly corresponds to the maximum velocity of th e basilar membrane towards scala tympani (as inferred from cochlear mi crophonic recordings).