Adaptation, Suppression and Tuning in Amphibian Acoustical Fibers

Abstract

I report observations made on saccular and amphibian-papillar afferent axons of the American bullfrog, Rana catesbeiana. The bullfrog amphibian papilla is an auditory endorgan whose afferents exhibit characteristic frequencies (cf’s) ranging from 1 kHz down to slightly more than 100 Hz, with substantial sensitivity extending below 50 Hz (Capranica, 1976). In many afferents with cf’s below 500 Hz, one observes two well-known phenomena: (1) adaptation to continuous tones at cf and other frequencies, and (2) suppression of responses to continuous tones at cf or other frequencies by addition of a high-intensity tone at a frequency approximately 300–400 Hz above cf (Capranica and Moffat, 1980). The bullfrog saccule is a seismic endorgan whose afferents exhibit cf’s ranging approximately from 10 Hz to 150 Hz, with substantial sensitivity extending to 200 Hz (Koyama et al., 1980). Afferents from this endorgan exhibit neither adaptation nor two-tone suppression.