Frequency-modulated up-chirp stimuli enhance the auditory brainstem response of the killer whale (Orcinus orca)

TitleFrequency-modulated up-chirp stimuli enhance the auditory brainstem response of the killer whale (Orcinus orca)
Publication TypeJournal Article
Year of Publication2019
AuthorsHouser, Dorian S., Mulsow Jason, Almunia Javier, and Finneran James J.
JournalThe Journal of the Acoustical Society of America
Volume146
Pagination289-296
EndNote Rec Number12685
Keywordsauditory evoked potentials,bioacoustics,zoology
Abstract

Previous studies suggested that frequency-modulated tonal stimuli where the frequency sweeps upward (up-chirps) may enhance auditory brainstem response (ABR) amplitudes in mammals. In this study, ABRs were measured in response to up-chirps in three killer whales (Orcinus orca) and compared to ABRs evoked by broadband clicks. Chirp durations ranged from 125 − 2000 μs. Chirp spectral content was either “uncompensated,” meaning the spectrum paralleled the transmitting response of the piezoelectric transducer, or “compensated,” where the spectral density level was flat (+/−4 dB) across the stimulus bandwidth (10 − 130 kHz). Compensated up-chirps consistently produced higher amplitude ABRs than uncompensated clicks with the same peak equivalent sound pressure level. ABR amplitude increased with up-chirp duration up to 1400 μs, although there was considerable variability between individuals. Results suggest that compensating stimuli for the response of transducers can have a dramatic effect on broadband ABRs, and that compensated up-chirps might be useful for testing whale species where large size makes far-field recording of ABRs at the skin surface difficult.