A comparative study of hearing ability in ® shes : the auditory brainstem

Auditory brainstem response (ABR) techniques, an electrophysiological far-®eld recording method widely used in clinical evaluation of human hearing, were adapted for ®shes to overcome the major limitations of traditional behavioral and electrophysiological methods (e.g., invasive surgery, lengthy training of ®shes, etc.) used for ®sh hearing research. Responses to clicks and tone bursts of di€erent frequencies and amplitudes were recorded with cutaneous electrodes. To evaluate the e€ectiveness of this method, the auditory sensitivity of a hearing specialist (gold®sh, Carassius auratus) and a hearing generalist (oscar, Astronotus ocellatus) was investigated and compared to audiograms obtained through psychophysical methods. The ABRs could be obtained between 100 Hz and 2000 Hz (oscar), and up to 5000 Hz (gold®sh). The ABR audiograms are similar to those obtained by behavioral methods in both species. The ABR audiogram of curarized (i.e., Flaxediltreated) gold®sh did not di€er signi®cantly from two previously published behavioral curves but was lower than that obtained from uncurarized ®sh. In the oscar, ABR audiometry resulted in lower thresholds and a larger bandwidth than observed in behavioral tests. Comparison between methods revealed the advantages of this technique: rapid evaluation of hearing in untrained ®shes, and no limitations on repeated testing of