Auditory sensitivity of the saccule in the American toad (Bufo americanus)

Summary Single unit recordings in the posterior nerve branchlet from the saccule have shown that, in the American toad (Bufo americanus), approximately 30% of the fibers respond to airborne sounds in a way similar to fibers from the two known auditory organs, the amphibian and basilar papillae. In response to tones, saccule fibers have best excitatory frequencies which fall into two disjoint populations: units in the low-frequency-sensitive group (below 300 Hz) show tone-on-tone suppression while those in the high-frequency-sensitive group (700–1,200 Hz) show no evidence of peripheral inhibition. Saccule units have somewhat higher thresholds than those from the other auditory organs. It is suggested that the high-frequency-sensitive fibers might be useful for discriminating mating calls in an intense chorus while the low-frequency-sensitive units likely respond to other high intensity sounds in the environment.Research supported by the U.S. Public Health Service (NIH grant NS-09244).