Distortion product otoacoustic emissions in the amphibian ear

By comparing the range of emission frequencies with that of neural characteristic frequencies of the amphibian and basilar papillae, the emission generation site may be inferred. Spontaneous otoacoustic emissions in the amphibian car seem to originate from the amphibian papilla. In contrast, distortion product otoacoustic emission are presumably generated by both the amphibian and the basilar papillae. Distortion products from the amphibian papilla are very sensitive to ischemia; distortion products from the basilar papilla are less sensitive. These results suggest that the basilar papilla may not include an active amplifier. In support of this hypothesis, we show that distortion products from the basilar papilla show only a weak temperature dependence. These emissions are possibly independent of metabolic rate. The basilar papilla in frogs may be the only passive vertebrate hearing organ. In contrast, emissions from the amphibian papilla are clearly temperature dependent, consistent with active auditory processing.