Derived guinea pig compound VIIIth nerve action potentials to continuous pure tones

Journal of Experimental Biology

Malmkvist

Nielsen

et al. 2013

SUMMARYAmerican mink (Neovison vison) kits are born altricial and fully dependent on maternal care, for which the kits' vocalizations appear essential. We used auditory brainstem responses (ABRs) to determine: (1) hearing sensitivity of adult females from two breeding lines known to differ in maternal behaviour and (2) development of hearing in kits 8-52days of age. We also studied sound production in 20 kits throughout postnatal days 1 to 44. Adult female mink had a broad hearing range from 1kHz to above 70kHz, with peak sensitivity (threshold of 20dB SPL) at 8-10kHz, and no difference in sensitivity between the two breeding lines (P>0.22) to explain the difference in maternal care. Mink kits showed no signs of hearing up to postnatal day 24. From day 30, all kits had ABRs indicative of hearing. Hearing sensitivity increased with age, but was still below the adult level at postnatal day 52. When separated from their mothers, kits vocalized loudly. Until the age of 22days, 90% of all kits vocalized with no significant decline with age (P=0.27). From day 25, concurrent with the start of hearing, the number of vocalizing kits decreased with age (P<0.001), in particular in kits that were re-tested (P=0.004). Large numbers of mink are kept in fur industry farms, and our results are important to the understanding of sound communication, which is part of their natural behaviour. Our results also suggest mink as an interesting model for studying the development of mammalian hearing and its correlation to sound production.

Section: Testing Hearing In Adults and Kitsmentioning

confidence: 92%

Section: Testing Hearing In Adults and Kitsmentioning

confidence: 99%

Development of vocalization and hearing in American mink (Neovison vison).

Journal of Experimental Biology

Malmkvist

Nielsen

et al. 2013

“…In all cases, audiograms were measured by stimulating alternately with a brief pulse and with the pulse with an added tonal masker. Sensitivity to the masker was assayed by subtracting masked from unmasked responses [20,21]. The masked ABR enabled us to measure auditory responses at very low frequencies, where it is difficult to get a good response using tone burst ABR measurements.…”

Section: Methodsmentioning

confidence: 99%

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

Christensen‐Dalsgaard

Willis

et al. 2012

Proc. R. Soc. B.

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.

“…Following this increase in discharge, the auditory neurons are refractory and respond to a lesser degree or not at all to a subsequent stimulation. This phenomenon is known as forward masking, and can be used to determine thresholds of pure tones in evoked potential studies (Berlin et al, 1991;Christensen-Dalsgaard et al, 2011;Manley and Kraus, 2010).…”

Section: Masked Evoked Potentialsmentioning

confidence: 99%

Hearing with an atympanic ear: good vibration and poor sound-pressure detection in the royal python,Python regius

Christensen

Christensen‐Dalsgaard

Journal of Experimental Biology

et al. 2012

SUMMARYSnakes lack both an outer ear and a tympanic middle ear, which in most tetrapods provide impedance matching between the air and inner ear fluids and hence improve pressure hearing in air. Snakes would therefore be expected to have very poor pressure hearing and generally be insensitive to airborne sound, whereas the connection of the middle ear bone to the jaw bones in snakes should confer acute sensitivity to substrate vibrations. Some studies have nevertheless claimed that snakes are quite sensitive to both vibration and sound pressure. Here we test the two hypotheses that: (1) snakes are sensitive to sound pressure and (2) snakes are sensitive to vibrations, but cannot hear the sound pressure per se. Vibration and sound-pressure sensitivities were quantified by measuring brainstem evoked potentials in 11 royal pythons, Python regius. Vibrograms and audiograms showed greatest sensitivity at low frequencies of 80-160Hz, with sensitivities of -54dBre.1ms -2 and 78dBre.20mPa, respectively. To investigate whether pythons detect sound pressure or sound-induced head vibrations, we measured the sound-induced head vibrations in three dimensions when snakes were exposed to sound pressure at threshold levels. In general, head vibrations induced by threshold-level sound pressure were equal to or greater than those induced by threshold-level vibrations, and therefore sound-pressure sensitivity can be explained by sound-induced head vibration. From this we conclude that pythons, and possibly all snakes, lost effective pressure hearing with the complete reduction of a functional outer and middle ear, but have an acute vibration sensitivity that may be used for communication and detection of predators and prey.Supplementary material available online at