The Effects of Air Pressure on Spontaneous Otoacoustic Emissions of Lizards

Dijk, Pim van; Manley, Geoffrey A.

doi:10.1007/s10162-013-0385-0

Cited by 10 publications

(5 citation statements)

References 35 publications

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“…As far as we know, there is only one report of experimentally observed frequency shifts of lizard SOAEs. Van Dijk and Manley [2013] found that small changes of air pressure against the eardrum of five lizard species led to changes in frequency of otoacoustic emissions. These changes, both up and down, and for both increases and decreases in pressure, had a magnitude of a few percent (Van Dijk and Manley [2013], Fig.…”

Section: Discussionmentioning

confidence: 99%

Frequency Shifts in a Local Oscillator Model for the Generation of Spontaneous Otoacoustic Emissions by the Lizard Ear

Wit¹,

Bell²

2023

Audiol Neurotol

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Introduction: In order to understand human hearing, it helps to understand how the ears of lower vertebrates, like, for instance, lizards, function. A key feature in common is that the ears of both humans and lizards emit faint, pure tones known as spontaneous otoacoustic emissions (SOAEs). More than four decades after their discovery, the mechanism underlying these emissions is still imperfectly understood, although it is known that they are important for improving the sensitivity and sharpness of hearing. In both humans and lizards, the frequencies of SOAEs change by a few percent when static pressure is applied to the tympanic membrane. For the human ear, this observation is normally explained by a so-called global oscillator model (such as with Shera’s coherent reflection model), in which the emissions result from standing waves, and external pressure changes the boundary conditions – the stiffness of the oval and round windows – which then has a global effect on the SOAE frequencies. Methods: Here we investigate how changing parameters of an earlier developed local oscillator model for the lizard ear can change the frequencies of the SOAEs. A major feature of the model is that each oscillator is coupled only to its immediate neighbours. The oscillators then cluster into groups of identical frequency, and each of these so-called frequency plateaus can be taken to represent an SOAE. Results: Even though the natural (unperturbed) frequencies of all the oscillators remain fixed, here we find for several model parameters that by slightly changing their value the frequency plateaus – the SOAEs – shift by a few percent. Plots of how these changes alter SOAE frequencies are given, and their magnitude corresponds well with observations of SOAE changes in lizards. Discussion: Investigation of the influence of the change of parameters in an earlier developed local oscillator model for the lizard ear shows that a local oscillator model can explain small SOAE frequency changes as well as a global oscillator model.

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Section: Discussionmentioning

confidence: 99%

Frequency Shifts in a Local Oscillator Model for the Generation of Spontaneous Otoacoustic Emissions by the Lizard Ear

Wit¹,

Bell²

2023

Audiol Neurotol

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“…For the last 29 years, SOAE have been extensively studied in a range of lizard species [ 4 , 5 , 9 , 14 , 18 , 23 , 24 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ]. In this brief review, only some main features of these studies can be covered.…”

Section: Otoacoustic Emissions In Non-mammalian Land Vertebrate Groupsmentioning

confidence: 99%

“…The differences now observed in inner-ear auditory epithelia necessitate that in this review, each taxon be dealt with separately, which explains the taxonomic arrangement of the details described in the following sections. On the other hand, the middle ears, all of which consist functionally of one ossicle (anatomically with at least two sub-components) [ 3 ], will be ignored since there is currently no evidence that middle ears subtly affect the characteristics of otoacoustic emissions (OAE) unless there is an air-pressure difference across the eardrum [ 4 , 5 ].…”

Section: Introductionmentioning

confidence: 99%

Otoacoustic Emissions in Non-Mammals

Manley

2022

Audiology Research

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Otoacoustic emissions (OAE) that were sound-induced, current-induced, or spontaneous have been measured in non-mammalian land vertebrates, including in amphibians, reptiles, and birds. There are no forms of emissions known from mammals that have not also been observed in non-mammals. In each group and species, the emission frequencies clearly lie in the range known to be processed by the hair cells of the respective hearing organs. With some notable exceptions, the patterns underlying the measured spectra, input-output functions, suppression threshold curves, etc., show strong similarities to OAE measured in mammals. These profound similarities are presumably traceable to the fact that emissions are produced by active hair-cell mechanisms that are themselves dependent upon comparable nonlinear cellular processes. The differences observed—for example, in the width of spontaneous emission peaks and delay times in interactions between peaks—should provide insights into how hair-cell activity is coupled within the organ and thus partially routed out into the middle ear.

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“…Finally, altering the air pressure in the ear canal strongly affects SOAEs: extreme pressure changes typically attenuate the emissions. The associated shifts in SOAE frequency are complex and vary widely between species ( 9 , 10 , 11 ). In addition to altering the acoustic impedance of the middle ear, changes in ear-canal pressure might influence the intracochlear noise level or the active process underlying the emissions ( 10 , 11 , 12 ).…”

Section: Introductionmentioning

confidence: 99%

Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears

Roongthumskul

Maoiléidigh

Hudspeth

2019

Biophysical Journal

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Spontaneous otoacoustic emissions (SOAEs) are weak sounds that emanate from the ears of tetrapods in the absence of acoustic stimulation. These emissions are an epiphenomenon of the inner ear's active process, which enhances the auditory system’s sensitivity to weak sounds, but their mechanism of production remains a matter of debate. We recorded SOAEs simultaneously from the two ears of the tokay gecko and found that binaural emissions could be strongly correlated: some emissions occurred at the same frequency in both ears and were highly synchronized. Suppression of the emissions in one ear often changed the amplitude or shifted the frequency of emissions in the other. Decreasing the frequency of emissions from one ear by lowering its temperature usually reduced the frequency of the contralateral emissions. To understand the relationship between binaural SOAEs, we developed a mathematical model of the eardrums as noisy nonlinear oscillators coupled by the air within an animal’s mouth. By according with the model, the results indicate that some SOAEs are generated bilaterally through acoustic coupling across the oral cavity. The model predicts that sound localization through the acoustic coupling between ears is influenced by the active processes of both ears.

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The Effects of Air Pressure on Spontaneous Otoacoustic Emissions of Lizards

Cited by 10 publications

References 35 publications

Frequency Shifts in a Local Oscillator Model for the Generation of Spontaneous Otoacoustic Emissions by the Lizard Ear

Frequency Shifts in a Local Oscillator Model for the Generation of Spontaneous Otoacoustic Emissions by the Lizard Ear

Otoacoustic Emissions in Non-Mammals

Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears

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