Use of auditory brainstem response (ARR) for fish auditory sensitivity study [abstract]

Hong Y. Yan, Todd N. Kenyon and Friedrich Ladich (1997). Use of auditory brainstem response (ARR) for fish auditory sensitivity study [abstract]. Bioacoustics, Volume 8 (3-4): 251

Traditionally psychoacoustical or electrophysiological methods have been used to study the auditory sensitivity of fishes. No invasive procedures are used in obtaining behavioural audiograms. The training procedures involved are tedious, time consuming and not applicable to every species. Electro- physiological recordings from auditory nerves or endorgans (e.g., microphonics) provide additional ways of auditory sensitivity assessment. Technical difficulties and limited sampling site(s) prevent rapid and complete understanding of fish hearing ability. In an attempt to expedite the fish audition ability research, an auditory brainstem response (ABR) recording protocol is developed to provide measurements of hearing ability of several species of fish. The ARRS represent far field potentials generated by the hearing endorgans, fibre tracts and nuclei of the ascending auditory pathway. Therefore audiograms generated by ABR technique can provide a quick and more complete understanding of fish hearing ability. A tungsten reference electrode is placed in between the nares of the fish while the recording electrode is placed on the top of the fish's head to conduct ABR recording. The fish is immobilized with an injection of Flexedil, and a gravity-feed respirator (with aerated water) is used to keep the fish alive during the recording. Pure tone bursts (100 Hz to 3 kHz) or click signals are provided through a speaker mounted above the tested animals. A hydrophone is placed adjacent to the ear region of the 5sh and traces of hydrophone output (i.e. the sound likely to be perceived by the 8sh are used to compare with ARR waves generated by the fish. For comparison purposes fish species used are a hearing specialist (fathead minnow, Pimephales promelas), a generalist (oscar Astronotus ocellatus) and a labyrinth fish with an accessory hearing enhancing structure (blue gourami Trichogaster trichopterus). Easy set-up of ARR recording devices and commercially available systems (e.g. Tucker-Davis Technologies) facilitate quick ARR measurement of the auditory ability of fishes. This technique can be used to investigate the relationship between acoustic signals generated by sonic fish and their auditory sensitivity.