Middle ear sensitivity in anurans and reptiles measured by light scattering spectroscopy

Moffat, Anne J. M.; Capranica, Robert R.

doi:10.1007/bf01352294

Cited by 47 publications

(23 citation statements)

References 53 publications

(56 reference statements)

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“…The lowest threshold in air at 61 dB SPL corresponds to a tympanic disc vibration of approximately 3.6 mm s 21 (0.5 nm displacement at 500 Hz). Direct measurements of disc transfer function using light scattering spectroscopy [35] showed peak amplitudes of 15-50 nm at 500 Hz and 90 dB SPL sound pressure, so these measurements are comparable. Whole-body vibrograms had a best frequency of 100-200 Hz, lower than both sound and disc vibration audiograms.…”

Section: Discussionmentioning

confidence: 88%

Specialization for underwater hearing by the tympanic middle ear of the turtle,Trachemys scripta elegans

Christensen‐Dalsgaard

Brandt

Willis

et al. 2012

Proc. R. Soc. B.

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Turtles, like other amphibious animals, face a trade-off between terrestrial and aquatic hearing. We used laser vibrometry and auditory brainstem responses to measure their sensitivity to vibration stimuli and to airborne versus underwater sound. Turtles are most sensitive to sound underwater, and their sensitivity depends on the large middle ear, which has a compliant tympanic disc attached to the columella. Behind the disc, the middle ear is a large air-filled cavity with a volume of approximately 0.5 ml and a resonance frequency of approximately 500 Hz underwater. Laser vibrometry measurements underwater showed peak vibrations at 500-600 Hz with a maximum of 300 mm s 21 Pa 21 , approximately 100 times more than the surrounding water. In air, the auditory brainstem response audiogram showed a best sensitivity to sound of 300-500 Hz. Audiograms before and after removing the skin covering reveal that the cartilaginous tympanic disc shows unchanged sensitivity, indicating that the tympanic disc, and not the overlying skin, is the key sound receiver. If air and water thresholds are compared in terms of sound intensity, thresholds in water are approximately 20-30 dB lower than in air. Therefore, this tympanic ear is specialized for underwater hearing, most probably because sound-induced pulsations of the air in the middle ear cavity drive the tympanic disc.

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Section: Discussionmentioning

confidence: 88%

Specialization for underwater hearing by the tympanic middle ear of the turtle,Trachemys scripta elegans

Christensen‐Dalsgaard

Brandt

Willis

et al. 2012

Proc. R. Soc. B.

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“…The auditory range, reflected in the distribution of characteristic frequencies from about 30-700 Hz was also comparable to the range found in intact chelonia at room temperature, although Adrian et al (1938) noted that the upper frequency limit of the nerve responses was temperature-sensitive, being reduced to about 200 Hz at 10 'C. The sensitivity of the middle ear transfer in Pseudemys has been found to fall off quite steeply above 650 Hz (Moffat & Capranica, 1978) which coincides with the upper limit of the distribution of c.f.s in the auditory nerve.…”

Section: Discussionmentioning

confidence: 88%

“…If one allows for a 20 db difference in auditory nerve fibre thresholds between the two species (making the assumption that all this difference derives from the lower sensitivity of the middle ear, there is evidence to support the view that at least 10 db can be accounted for in this way: e.g. Moffat & Capranica 1978) the basilar membrane displacement in the turtle might be closer to + 0*02 nm at 40 db s.p.l. At this sound pressure, corresponding approximately to the animal's behavioural threshold (Fig.…”

Section: Nature Of the Resonancementioning

confidence: 99%

The frequency selectivity of auditory nerve fibres and hair cells in the cochlea of the turtle

Crawford

Fettiplace

1980

The Journal of Physiology

245

175

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SUMMARY1. The electrical responses of single auditory nerve fibres or cochlear hair cells were recorded in the isolated half-head of the turtle Pseudemys scripta elegant. Responses to sound stimuli presented to the tympanum could be recorded for at least 4 hr after isolation.2. Impulses were recorded extracellularly from single auditory nerve fibres. For tones of suprathreshold intensity the impulses occurred with a preferred phase relation (i.e. they were phase-locked) to the cycles of the sound stimulus. Nerve 3. Intracellular recordings were made from hair cells in the basilar papilla. Following injection of a fluorescent dye into a cell through the recording electrode, the dye was localized in a single hair cell in a transverse section of the cochlea.4. Hair cells had resting potentials of about -50 mV, and, to low frequency tones, gave periodic responses graded with the intensity and frequency of the stimulus. Recordings were obtained from cells with characteristic frequencies between 70 and 670 Hz.5. The voltage response to a pure tone at low sound pressure was sinusoidal for all frequencies of stimulation; at higher sound pressures a number of non-linearities were apparent in the response wave form. One of these was a steady depolarizing component, which, relative to the periodic component of the response, was most prominent at high frequencies.6. The amplitude of the response evoked in a hair cell by a low intensity tone was linearly related to the sound pressure; for loud sounds, the response eventually reached a saturating amplitude, which in some cells was as great as 30-45 mV peakto-peak.7. The linear sensitivity of a hair cell is defined as the r.m.s. voltage for a linear response of the cell at its c.f. divided by the sound pressure at the tympanum. In the most sensitive cells this value was 30-90 mV/Pa. 8. If the frequency selectivity of a hair cell was expressed in terms of the sound pressure needed to produce a constant amplitude of response, the sharpness of this frequency selectivity was found to be virtually independent of the response criterion for responses between 1 and 10 mV; in the cells which gave the largest responses, the

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“…The mechanism behind such correlations has been investigated by diverse methodologies (Majeau-Chargois and McDanall Whitehead, 1971;Chung et al, 1978;Chung et al, 1981;Pettigrew et al, 1981;Hetherington, 1992;Boatright-Horowitz and Megela-Simmons, 1995). At another level, Moffat and Capranica (Moffat and Capranica, 1978) suggested that due to the size effect on TM resonance, the middle ear may act as a first frequency filter, as suggested by Manley for lizards (Manley, 1972). However, in most of these previous studies, the function of the middle ear was not unambiguously separated from possible participation or effects of the inner ear (including its mechanically loading the middle ear).…”

Section: Sexual Diergism Of Hearing In the Bullfrog: The Frequency Domentioning

confidence: 99%

“…The intersexual vocal communication of anurans was already described in the fourth century BC by Aristotle (Aristotle, 1984), who said that male frogs croak to attract the females, and in recent decades, this area has generated an assortment of investigations and reviews, such as Bogert (Bogert, 1960) and Schneider (Schneider, 1990). In particular, the structure and function of the anuran ear have attracted research and reviews (Capranica, 1978;Purgue and Narins, 2000;Mason, 2007). But despite recent advances (Mason and Narins, 2002a;Mason and Narins, 2002b;Mason et al, 2003;Werner, 2003), the riddle of sexually dimorphic (dually formed) and diergic [dually functioning (Rhodes and Rubin, 1999)] anuran ears has not yet been solved.…”

Section: Introductionmentioning

confidence: 99%

Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight

Werner

Pylka

Schneider

et al. 2009

Journal of Experimental Biology

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SUMMARYThe dimorphic ear of the bullfrog, Rana catesbeiana, has long been enigmatic. The male's tympanic membrane (TM) area approximates twice the area of the female's; however, similar size differences in the area of the columellar footplate were not observed between the sexes. Hence, the male's hearing is expected to be more sensitive than the female's but this is not the case. Asking what offsets the advantage of the large TM, we applied a series of experiments to the auditory system. Male and female audiograms based on stimulation with airborne sound and on both multi-unit responses from the brain and alternating cochlear potentials ('microphonics') showed equal sensitivity and a small difference in frequency response; at low frequencies the male was more sensitive than the female. Amputating the columella and stimulating the stump with mechanical vibration showed that for an equal microphonic response, the male's footplate vibrated with lower amplitude than the female's footplate. Mechanically stimulating the TM of the intact ear replicated this result, excluding the involvement of the mechanical lever. The TM of the male weighs five times the TM of the female, and artificial loading of the TM of either sex greatly reduced the ear's sensitivity. Hence, the male's excessive area ratio (TM to columellar footplate) is offset by the heavier cartilage cushion on the male's TM, damping the TM's response to sound. This is corroborated by experimentally artificially loading the TM. The product of area ratio and footplate vibration amplitude would result in similar stimulation of the inner ear in the two sexes.

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Middle ear sensitivity in anurans and reptiles measured by light scattering spectroscopy

Cited by 47 publications

References 53 publications

Specialization for underwater hearing by the tympanic middle ear of the turtle,Trachemys scripta elegans

Specialization for underwater hearing by the tympanic middle ear of the turtle,Trachemys scripta elegans

The frequency selectivity of auditory nerve fibres and hair cells in the cochlea of the turtle

Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight

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