Temperature effects on auditory nerve fiber response in the American bullfrog.

Single fiber recordings were made from auditory nerve fibers of the American bullfrog (Rana catesbeiana). As temperature was raised: (1) Best frequencies of fibers from the amphibian papilla (N = 15) increased. Below 600 Hz best frequency changes up to 0.06 oct/degrees C were found; above 600 Hz changes were less than 0.03 oct/degrees C. In the basilar papilla (N = 4) no significant increase of best frequency was found. (2) Spike rates in response to fixed-RMS-amplitude stimuli increased considerably: Q10 of spike rate ranged from 5 to 10. (3) Spontaneous activity, found in basilar papilla fibers, increased with average Q10 = 1.6 (+/- 0.3). (4) A conspicuous change of tuning quality factor Q10 dB was only observed in two fibers, that were taken to low temperatures (less than 16 degrees C). (5) the nearly linear frequency vs. phase relation in amphibian papilla shifts to higher frequency (along with shift of best frequency), while its average slope remains nearly unchanged.