Response differences in gerbil and guinea pig auditory nerve fibers for low frequency sinusoidal acoustic stimuli

Abstract

Time locked responses of auditory nerve fibers to a 50-Hz sinusoidal acoustic stimulus were studied in both guinea pigs and gerbils. Whereas the time locked responses of all guinea pig fibers resulted in single peaked histograms, those of gerbil auditory nerve fibers resulted in either single, double, or triple peaked histograms. Generally speaking, single peaked histograms are associated with gerbil fibers having CFs below about 2 kHz, double peaked histograms with fibers having CFs between 2 kHz and 8 kHz, and triple peaked histograms with fibers having CFs above 8 kHz. Although the shapes of the histograms vary with stimulus level, the locations of the peaks of maximum response are essentially invariant over the range of stimulus intensities used. In guinea pigs, the relative latency of peak response increases progressively with increasing fiber CF. In gerbils, the same is true only for fibers having CFs below about 2 kHz. Accordingly, there does not appear to be a CF independent preferred time of occurrence of neural response relative to the acoustic stimulus in either species.