Comparison of the response of the two-fiber populations in the auditory nerve of the alligator lizard

Abstract

The basilar papilla of the alligator lizard (Gerrhonotus multicarinatus) contains two anatomically distinct hair cell populations. The apical population has unidirectional orientation and is associated with a tectorial membrane. The dorsal population has bidirectional orientation and free-standing cilia. On the basis of tuning curve properties, the primary auditory nerve fibers have been categorized into low (<0.9 kHz) and high (>0.9 kHz) CF populations. These two populations have been associated with the apical and basal regions of the papilla, respectively [Weiss, Mulroy, Turper, and Pike, J. Acoust. Soc. Am. 55, S84(A) (1974)]. The objective of the present study was to determine if other measures of the physiological response of the fibers could distinguish the two fiber populations. Action potentials were recorded from single, primary auditory nerve fibers in response to click, tone burst, and noise burst stimuli. The data indicate significant differences in the response of the two-fiber populations to the same acoustic stimulus. It is proposed that these physiological differences result primarily from the anatomical differences of the associated hair cell populations. [Work supported, in part, by NIH grants NS07287, NS06459, and NS05475, the Deafness Research Foundation, and Henry Ford Hospital.]