ABR frequency tuning curves in dolphins

Abstract

Tone-tone masking was used to determine auditory brain-stem response tuning curves in dolphins (Tursiops truncatus) in a simultaneous-masking paradigm. The Q10 of the curves was as large as 16-19 in the frequency range 64-128 kHz. In the range 45-16 kHz, Q10 decreased proportionally to the frequency with the bandwidth of the curves being constant, about 3.5-4 kHz at the 10-dB level. Tuning curves below 45 kHz are supposed to reflect broad spectral bandwidth of the probe's effective part which is no longer than 0.5 ms, irrespective of actual probe duration. Tuning curves above 64 kHz are supposed to reflect the real frequency tuning of the dolphin's auditory system.

Frequency tuning curves of the dolphin's hearing: envelope-following response study

“…The active electrode was placed in the dorsal part of the head, at the midline, 6 8 cm behind the blowhole, above the water surface. This site was shown to be the best for ABR recording, and the used electrode position made it possible to compare recorded responses with those described earlier using the same recording technique (Popov and Supin 1990;Supin et al 1993). The reference electrode was in the back near the dorsal fin, also above the water surface.…”

“…Our previous work (Supin et al 1993) has demonstrated that this method is effective to investigate frequency tuning in dolphins. The ABR can be recorded easily from the dolphin's head surface, without any surgical procedure and anesthesia.…”

“…Such probe was satisfactory at frequencies above 64 kHz where tuning curves were wider than the stimulus bandwidth. It was not appropriate, however, at frequencies below 64 kHz where tuning curves were expected to be narrower (Supin et al 1993). …”

“…Just as in our preceding work (Supin et al 1993), we used in this study the simultaneous masking paradigm and choose the near-complete masking criterion to obtain tuning curves. Since long amplitudemodulated sound bursts must be used to evoke EFR and recovery time of evoked potentials in the dolphin's auditory system is as short as a few Stimuli milliseconds or less (Popov and Supin 1990), no significant forward masking of such long probes might be expected.…”

Evolutionary adaptations for the temporal processing of natural sounds by the anuran peripheral auditory system

“…We investigated temporal processing using auditory evoked potentials (AEPs). AEPs measure neural activity from the auditory nerve and brainstem in response to acoustic stimuli, and they are a common tool for studying auditory processing in humans and other animals (Brittan-Powell et al, 2010a,b;Gall et al, 2013;Hall, 2007;Henry and Lucas, 2008;Higgs et al, 2002;Katbamna et al, 1992;Kenyon et al, 1998;Ladich and Fay, 2013;Popov and Supin, 1990;Supin et al, 1993). We used two well-established AEP techniques that have been used previously to investigate temporal processing: the auditory steady-state response (ASSR) evoked by AM tones and the auditory brainstem response (ABR) evoked by paired acoustic clicks (Burkard and Deegan, 1984;Dolphin and Mountain, 1992;Gall et al, 2013;Henry and Lucas, 2008;Mann et al, 2005;Purcell et al, 2004;Wysocki and Ladich, 2005).…”