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Manley GA. Conditions Underlying the Appearance of Spontaneous Otoacoustic Emissions in Mammals. J Assoc Res Otolaryngol 2024:10.1007/s10162-024-00950-5. [PMID: 38760548 DOI: 10.1007/s10162-024-00950-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 04/28/2024] [Indexed: 05/19/2024] Open
Abstract
Across the wide range of land vertebrate species, spontaneous otoacoustic emissions (SOAE) are common, but not always found. The reasons for the differences between species of the various groups in their emission patterns are often not well understood, particularly within mammals. This review examines the question as to what determines in mammals whether SOAE are emitted or not, and suggests that the coupling between hair-cell regions diminishes when the space constant of frequency distribution becomes larger. The reduced coupling is assumed to result in a greater likelihood of SOAE being emitted.
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Affiliation(s)
- Geoffrey A Manley
- Cochlear and Auditory Brainstem Physiology, Department of Neuroscience, School of Medicine and Health Sciences, Cluster of Excellence "Hearing4all", Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany.
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Austin TT, Woodrow C, Pinchin J, Montealegre-Z F, Warren B. Effects of age and noise on tympanal displacement in the Desert Locust. JOURNAL OF INSECT PHYSIOLOGY 2024; 152:104595. [PMID: 38052320 DOI: 10.1016/j.jinsphys.2023.104595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 11/21/2023] [Accepted: 12/02/2023] [Indexed: 12/07/2023]
Abstract
Insect cuticle is an evolutionary-malleable exoskeleton that has specialised for various functions. Insects that detect the pressure component of sound bear specialised sound-capturing tympani evolved from cuticular thinning. Whilst the outer layer of insect cuticle is composed of non-living chitin, its mechanical properties change during development and aging. Here, we measured the displacements of the tympanum of the desert Locust, Schistocerca gregaria, to understand biomechanical changes as a function of age and noise-exposure. We found that the stiffness of the tympanum decreases within 12 h of noise-exposure and increases as a function of age, independent of noise-exposure. Noise-induced changes were dynamic with an increased tympanum displacement to sound within 12 h post noise-exposure. Within 24 h, however, the tone-evoked displacement of the tympanum decreased below that of control Locusts. After 48 h, the tone-evoked displacement of the tympanum was not significantly different to Locusts not exposed to noise. Tympanal displacements reduced predictably with age and repeatably noise-exposed Locusts (every three days) did not differ from their non-noise-exposed counterparts. Changes in the biomechanics of the tympanum may explain an age-dependent decrease in auditory detection in tympanal insects.
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Affiliation(s)
- Thomas T Austin
- College of Life Sciences, University of Leicester, Leicester LE1 7RH, UK
| | - Charlie Woodrow
- School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Lincoln LN6 7DL, UK
| | - James Pinchin
- Faculty of Engineering, University of Nottingham, University Park, Nottinghamshire NG7 2RD, UK
| | - Fernando Montealegre-Z
- School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Lincoln LN6 7DL, UK
| | - Ben Warren
- College of Life Sciences, University of Leicester, Leicester LE1 7RH, UK.
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Manley GA. Otoacoustic Emissions in Non-Mammals. Audiol Res 2022; 12:260-272. [PMID: 35645197 PMCID: PMC9149831 DOI: 10.3390/audiolres12030027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 05/06/2022] [Accepted: 05/09/2022] [Indexed: 01/27/2023] Open
Abstract
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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Affiliation(s)
- Geoffrey A Manley
- Department of Neuroscience, Faculty of Medicine, University of Oldenburg, 26129 Oldenburg, Germany
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Signatures of cochlear processing in neuronal coding of auditory information. Mol Cell Neurosci 2022; 120:103732. [PMID: 35489636 DOI: 10.1016/j.mcn.2022.103732] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 04/19/2022] [Accepted: 04/21/2022] [Indexed: 11/22/2022] Open
Abstract
The vertebrate ear is endowed with remarkable perceptual capabilities. The faintest sounds produce vibrations of magnitudes comparable to those generated by thermal noise and can nonetheless be detected through efficient amplification of small acoustic stimuli. Two mechanisms have been proposed to underlie such sound amplification in the mammalian cochlea: somatic electromotility and active hair-bundle motility. These biomechanical mechanisms may work in concert to tune auditory sensitivity. In addition to amplitude sensitivity, the hearing system shows exceptional frequency discrimination allowing mammals to distinguish complex sounds with great accuracy. For instance, although the wide hearing range of humans encompasses frequencies from 20 Hz to 20 kHz, our frequency resolution extends to one-thirtieth of the interval between successive keys on a piano. In this article, we review the different cochlear mechanisms underlying sound encoding in the auditory system, with a particular focus on the frequency decomposition of sounds. The relation between peak frequency of activation and location along the cochlea - known as tonotopy - arises from multiple gradients in biophysical properties of the sensory epithelium. Tonotopic mapping represents a major organizational principle both in the peripheral hearing system and in higher processing levels and permits the spectral decomposition of complex tones. The ribbon synapses connecting sensory hair cells to auditory afferents and the downstream spiral ganglion neurons are also tuned to process periodic stimuli according to their preferred frequency. Though sensory hair cells and neurons necessarily filter signals beyond a few kHz, many animals can hear well beyond this range. We finally describe how the cochlear structure shapes the neural code for further processing in order to send meaningful information to the brain. Both the phase-locked response of auditory nerve fibers and tonotopy are key to decode sound frequency information and place specific constraints on the downstream neuronal network.
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Manley GA. An evolutionary approach to middle-ear prostheses. Hear Res 2020; 400:108144. [PMID: 33310566 DOI: 10.1016/j.heares.2020.108144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 11/25/2020] [Accepted: 12/02/2020] [Indexed: 11/20/2022]
Abstract
The erroneous idea that mammalian three-ossicle middle ears are superior to single-ossicle ones has influenced thinking about prostheses. Evolutionary facts and measurements indicate that single-ossicle ears are equivalent and more flexible, supporting - in spite of new technological reconstruction techniques - their continued use as prostheses.
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Affiliation(s)
- Geoffrey A Manley
- Cochlear and Auditory Brainstem Physiology, Department of Neuroscience, School of Medicine and Health Sciences, Cluster of Excellence "Hearing4all", Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany.
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Wit HP, Manley GA, van Dijk P. Modeling the characteristics of spontaneous otoacoustic emissions in lizards. Hear Res 2019; 385:107840. [PMID: 31760263 DOI: 10.1016/j.heares.2019.107840] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 11/01/2019] [Accepted: 11/02/2019] [Indexed: 11/19/2022]
Abstract
Lizard auditory papillae have proven to be an attractive object for modelling the production of spontaneous otoacoustic emissions (SOAE). Here we use an established model (Vilfan and Duke, 2008) and extend it by exploring the effect of varying the number of oscillating elements, the strength of the parameters that describe the coupling between oscillators, the strength of the oscillators, and additive noise. The most remarkable result is that the actual number of oscillating elements hardly influences the spectral pattern, explaining why spectra from very different papillar dimensions are similar. Furthermore, the spacing between spectral peaks primarily depends on the reactive coupling between the oscillator elements. This is consistent with observed differences between lizard species with respect to tectorial covering of hair cells and SOAE peak spacings. Thus, the model provides a basic understanding of the variation in SOAE properties across lizard species.
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Affiliation(s)
- Hero P Wit
- University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, Groningen, the Netherlands; University of Groningen, Graduate School of Medical Sciences (Research School of Behavioral and Cognitive Neurosciences), Groningen, the Netherlands.
| | - Geoffrey A Manley
- Cochlear and Auditory Brainstem Physiology, Department of Neuroscience, School of Medicine and Health Sciences, Cluster of Excellence "Hearing4all", Research Center Neuroscience, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany
| | - P van Dijk
- University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, Groningen, the Netherlands; University of Groningen, Graduate School of Medical Sciences (Research School of Behavioral and Cognitive Neurosciences), Groningen, the Netherlands
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Engler S, Köppl C, Manley GA, de Kleine E, van Dijk P. Suppression tuning of spontaneous otoacoustic emissions in the barn owl (Tyto alba). Hear Res 2019; 385:107835. [PMID: 31710933 DOI: 10.1016/j.heares.2019.107835] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 09/30/2019] [Accepted: 10/27/2019] [Indexed: 11/20/2022]
Abstract
Spontaneous otoacoustic emissions (SOAEs) have been observed in a variety of different vertebrates, including humans and barn owls (Tyto alba). The underlying mechanisms producing the SOAEs and the meaning of their characteristics regarding the frequency selectivity of an individual and species are, however, still under debate. In the present study, we measured SOAE spectra in lightly anesthetized barn owls and suppressed their amplitudes by presenting pure tones at different frequencies and sound levels. Suppression effects were quantified by deriving suppression tuning curves (STCs) with a criterion of 2 dB suppression. SOAEs were found in 100% of ears (n = 14), with an average of 12.7 SOAEs per ear. Across the whole SOAE frequency range of 3.4-10.2 kHz, the distances between neighboring SOAEs were relatively uniform, with a median distance of 430 Hz. The majority (87.6%) of SOAEs were recorded at frequencies that fall within the barn owl's auditory fovea (5-10 kHz). The STCs were V-shaped and sharply tuned, similar to STCs from humans and other species. Between 5 and 10 kHz, the median Q10dB value of STC was 4.87 and was thus lower than that of owl single-unit neural data. There was no evidence for secondary STC side lobes, as seen in humans. The best thresholds of the STCs varied from 7.0 to 57.5 dB SPL and correlated with SOAE level, such that smaller SOAEs tended to require a higher sound level to be suppressed. While similar, the frequency-threshold curves of auditory-nerve fibers and STCs of SOAEs differ in some respects in their tuning characteristics indicating that SOAE suppression tuning in the barn owl may not directly reflect neural tuning in primary auditory nerve fibers.
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Affiliation(s)
- Sina Engler
- University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioural and Cognitive Neurosciences, University of Groningen, The Netherlands.
| | - Christine Köppl
- Cluster of Excellence "Hearing4all" and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany
| | - Geoffrey A Manley
- Cluster of Excellence "Hearing4all" and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, 26129, Oldenburg, Germany
| | - Emile de Kleine
- University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioural and Cognitive Neurosciences, University of Groningen, The Netherlands
| | - Pim van Dijk
- University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioural and Cognitive Neurosciences, University of Groningen, The Netherlands
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Naert G, Pasdelou MP, Le Prell CG. Use of the guinea pig in studies on the development and prevention of acquired sensorineural hearing loss, with an emphasis on noise. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:3743. [PMID: 31795705 PMCID: PMC7195866 DOI: 10.1121/1.5132711] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 07/30/2019] [Accepted: 08/12/2019] [Indexed: 05/10/2023]
Abstract
Guinea pigs have been used in diverse studies to better understand acquired hearing loss induced by noise and ototoxic drugs. The guinea pig has its best hearing at slightly higher frequencies relative to humans, but its hearing is more similar to humans than the rat or mouse. Like other rodents, it is more vulnerable to noise injury than the human or nonhuman primate models. There is a wealth of information on auditory function and vulnerability of the inner ear to diverse insults in the guinea pig. With respect to the assessment of potential otoprotective agents, guinea pigs are also docile animals that are relatively easy to dose via systemic injections or gavage. Of interest, the cochlea and the round window are easily accessible, notably for direct cochlear therapy, as in the chinchilla, making the guinea pig a most relevant and suitable model for hearing. This article reviews the use of the guinea pig in basic auditory research, provides detailed discussion of its use in studies on noise injury and other injuries leading to acquired sensorineural hearing loss, and lists some therapeutics assessed in these laboratory animal models to prevent acquired sensorineural hearing loss.
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Affiliation(s)
| | | | - Colleen G Le Prell
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas 75080, USA
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Harper T, Rougier GW. Petrosal morphology and cochlear function in Mesozoic stem therians. PLoS One 2019; 14:e0209457. [PMID: 31412094 PMCID: PMC6693738 DOI: 10.1371/journal.pone.0209457] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 06/07/2019] [Indexed: 11/19/2022] Open
Abstract
Here we describe the bony anatomy of the inner ear and surrounding structures seen in three plesiomorphic crown mammalian petrosal specimens. Our study sample includes the triconodont Priacodon fruitaensis from the Upper Jurassic of North America, and two isolated stem therian petrosal specimens colloquially known as the Höövör petrosals, recovered from Aptian-Albian sediments in Mongolia. The second Höövör petrosal is here described at length for the first time. All three of these petrosals and a comparative sample of extant mammalian taxa have been imaged using micro-CT, allowing for detailed anatomical descriptions of the osteological correlates of functionally significant neurovascular features, especially along the abneural wall of the cochlear canal. The high resolution imaging provided here clarifies several hypotheses regarding the mosaic evolution of features of the cochlear endocast in early mammals. In particular, these images demonstrate that the membranous cochlear duct adhered to the bony cochlear canal abneurally to a secondary bony lamina before the appearance of an opposing primary bony lamina or tractus foraminosus. Additionally, while corroborating the general trend of reduction of venous sinuses and plexuses within the pars cochlearis seen in crownward mammaliaforms generally, the Höövör petrosals show the localized enlargement of a portion of the intrapetrosal venous plexus. This new vascular feature is here interpreted as the bony accommodation for the vein of cochlear aqueduct, a structure that is solely, or predominantly, responsible for the venous drainage of the cochlear apparatus in extant therians. Given that our fossil stem therian inner ear specimens appear to have very limited high-frequency capabilities, the development of these modern vascular features of the cochlear endocast suggest that neither the initiation or enlargement of the stria vascularis (a unique mammalian organ) was originally associated with the capacity for high-frequency hearing or precise sound-source localization.
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Affiliation(s)
- Tony Harper
- Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Guillermo W. Rougier
- Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky, United States of America
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Wu F, Wang R. Transition between multimode oscillations in a loaded hair bundle. CHAOS (WOODBURY, N.Y.) 2019; 29:083135. [PMID: 31472489 DOI: 10.1063/1.5109752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 08/13/2019] [Indexed: 06/10/2023]
Abstract
In this paper, we study the dynamics of an autonomous system for a hair bundle subject to mechanical load. We demonstrated the spontaneous oscillations that arise owing to interactions between the linear stiffness and the adapting stiffness. It is found that by varying the linear stiffness, the system can induce a weakly chaotic attractor in a certain region where the stable periodic orbit is infinitely close to a parabolic curve composed of unstable equilibrium points. By altering the adapting stiffness associated with the calcium concentration, the system is able to trigger the transition from the bistable resting state, through a pair of symmetric Hopf bifurcation, into the bistable limit cycle, even to the chaotic attractor. At a negative adapting stiffness, the system exhibits a double-scroll chaotic attractor. According to the method of qualitative theory of fast-slow decomposition, the trajectory of a double-scroll chaotic attractor in the whole system depends upon the symmetric fold/fold bifurcation in a fast system. Furthermore, the control of the adapting stiffness in the improved system with two slow variables can trigger a new transition from the bistable resting state into the chaotic attractor, even to the hyperchaotic attractor by observing the Lyapunov exponent.
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Affiliation(s)
- Fuqiang Wu
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
| | - Runxia Wang
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China
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Roongthumskul Y, Ó Maoiléidigh D, Hudspeth AJ. Bilateral Spontaneous Otoacoustic Emissions Show Coupling between Active Oscillators in the Two Ears. Biophys J 2019; 116:2023-2034. [PMID: 31010667 PMCID: PMC6531668 DOI: 10.1016/j.bpj.2019.02.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 02/08/2019] [Accepted: 02/28/2019] [Indexed: 11/03/2022] Open
Abstract
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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Affiliation(s)
- Yuttana Roongthumskul
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York
| | - Dáibhid Ó Maoiléidigh
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York; Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California
| | - A J Hudspeth
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York.
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Ó Maoiléidigh D, Ricci AJ. A Bundle of Mechanisms: Inner-Ear Hair-Cell Mechanotransduction. Trends Neurosci 2019; 42:221-236. [PMID: 30661717 PMCID: PMC6402798 DOI: 10.1016/j.tins.2018.12.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 10/27/2022]
Abstract
In the inner ear, the deflection of hair bundles, the sensory organelles of hair cells, activates mechanically-gated channels (MGCs). Hair bundles monitor orientation of the head, its angular and linear acceleration, and detect sound. Force applied to MGCs is shaped by intrinsic hair-bundle properties, by the mechanical load on the bundle, and by the filter imparted by the environment of the hair bundle. Channel gating and adaptation, the ability of the bundle to reset its operating point, contribute to hair-bundle mechanics. Recent data from mammalian hair cells challenge longstanding hypotheses regarding adaptation mechanisms and hair-bundle coherence. Variations between hair bundles from different organs in hair-bundle mechanics, mechanical load, channel gating, and adaptation may allow a hair bundle to selectively respond to specific sensory stimuli.
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Affiliation(s)
- Dáibhid Ó Maoiléidigh
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine, Stanford CA 94305, USA
| | - Anthony J Ricci
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine, Stanford CA 94305, USA.
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Corey DP, Ó Maoiléidigh D, Ashmore JF. Mechanical Transduction Processes in the Hair Cell. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/978-3-319-52073-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
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Edri Y, Bozovic D, Yochelis A. Frequency locking in auditory hair cells: Distinguishing between additive and parametric forcing. EUROPHYSICS LETTERS 2016; 116:28002. [PMID: 33859450 PMCID: PMC8046175 DOI: 10.1209/0295-5075/116/28002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
- The auditory system displays remarkable sensitivity and frequency discrimination, attributes shown to rely on an amplification process that involves a mechanical as well as a biochemical response. Models that display proximity to an oscillatory onset (also known as Hopf bifurcation) exhibit a resonant response to distinct frequencies of incoming sound, and can explain many features of the amplification phenomenology. To understand the dynamics of this resonance, frequency locking is examined in a system near the Hopf bifurcation and subject to two types of driving forces: additive and parametric. Derivation of a universal amplitude equation that contains both forcing terms enables a study of their relative impact on the hair cell response. In the parametric case, although the resonant solutions are 1 : 1 frequency locked, they show the coexistence of solutions obeying a phase shift of π, a feature typical of the 2 : 1 resonance. Different characteristics are predicted for the transition from unlocked to locked solutions, leading to smooth or abrupt dynamics in response to different types of forcing. The theoretical framework provides a more realistic model of the auditory system, which incorporates a direct modulation of the internal control parameter by an applied drive. The results presented here can be generalized to many other media, including Faraday waves, chemical reactions, and elastically driven cardiomyocytes, which are known to exhibit resonant behavior.
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Affiliation(s)
- Yuval Edri
- Department of Physics, Ben-Gurion University of the Negev - Beer-Sheva, Israel
- Physics Department, Nuclear Research Center Negev - P.O. Box 9001, Beer-Sheva 84190, Israel
| | - Dolores Bozovic
- Department of Physics and Astronomy and California NanoSystems Institute, University of California Los Angeles Los Angeles, CA, 90025, USA
| | - Arik Yochelis
- Department of Solar Energy and Environmental Physics, Swiss Institute for Dryland Environmental and Energy Research, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus 8499000 Midreshet Ben-Gurion, Israel
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Manley GA, van Dijk P. Frequency selectivity of the human cochlea: Suppression tuning of spontaneous otoacoustic emissions. Hear Res 2016; 336:53-62. [PMID: 27139323 DOI: 10.1016/j.heares.2016.04.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 03/25/2016] [Accepted: 04/15/2016] [Indexed: 11/16/2022]
Abstract
Frequency selectivity is a key functional property of the inner ear and since hearing research began, the frequency resolution of the human ear has been a central question. In contrast to animal studies, which permit invasive recording of neural activity, human studies must rely on indirect methods to determine hearing selectivity. Psychophysical studies, which used masking of a tone by other sounds, indicate a modest frequency selectivity in humans. By contrast, estimates using the phase delays of stimulus-frequency otoacoustic emissions (SFOAE) predict a remarkably high selectivity, unique among mammals. An alternative measure of cochlear frequency selectivity are suppression tuning curves of spontaneous otoacoustic emissions (SOAE). Several animal studies show that these measures are in excellent agreement with neural frequency selectivity. Here we contribute a large data set from normal-hearing young humans on suppression tuning curves (STC) of spontaneous otoacoustic emissions (SOAE). The frequency selectivities of human STC measured near threshold levels agree with the earlier, much lower, psychophysical estimates. They differ, however, from the typical patterns seen in animal auditory nerve data in that the selectivity is remarkably independent of frequency. In addition, SOAE are suppressed by higher-level tones in narrow frequency bands clearly above the main suppression frequencies. These narrow suppression bands suggest interactions between the suppressor tone and a cochlear standing wave corresponding to the SOAE frequency being suppressed. The data show that the relationship between pre-neural mechanical processing in the cochlea and neural coding at the hair-cell/auditory nerve synapse needs to be reconsidered.
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Affiliation(s)
- Geoffrey A Manley
- Cochlear and Auditory Brainstem Physiology, Department of Neuroscience, School of Medicine and Health Sciences, Cluster of Excellence "Hearing4all", Research Centre Neurosensory Science, Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany
| | - Pim van Dijk
- University of Groningen, University Medical Center Groningen, Department of Otorhinolaryngology/Head and Neck Surgery, P.O. Box 30.001, 9700 RB Groningen, The Netherlands; University of Groningen, Graduate School of Medical Sciences, Research School of Behavioural and Cognitive Neuroscience, The Netherlands.
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Abstract
It is pointed out that the mystery of how biological systems measure their lengths vanishes away if one premises that they have discovered a way to generate linear waves analogous to compressional sound. These can be used to detect length at either large or small scales using echo timing and fringe counting. It is shown that suitable linear chemical potential waves can, in fact, be manufactured by tuning to criticality conventional reaction-diffusion with a small number substance. Min oscillations in Escherichia coli are cited as precedent resonant length measurement using chemical potential waves analogous to laser detection. Mitotic structures in eukaryotes are identified as candidates for such an effect at higher frequency. The engineering principle is shown to be very general and functionally the same as that used by hearing organs.
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Fruth F, Jülicher F, Lindner B. An active oscillator model describes the statistics of spontaneous otoacoustic emissions. Biophys J 2015; 107:815-24. [PMID: 25140416 DOI: 10.1016/j.bpj.2014.06.047] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 06/10/2014] [Accepted: 06/18/2014] [Indexed: 11/26/2022] Open
Abstract
Even in the absence of external stimulation, the cochleas of most humans emit very faint sounds below the threshold of hearing, sounds that are known as spontaneous otoacoustic emissions. They are a signature of the active amplification mechanism in the cochlea. Emissions occur at frequencies that are unique for an individual and change little over time. The statistics of a population of ears exhibit characteristic features such as a preferred relative frequency distance between emissions (interemission intervals). We propose a simplified cochlea model comprising an array of active nonlinear oscillators coupled both hydrodynamically and viscoelastically. The oscillators are subject to a weak spatial disorder that lends individuality to the simulated cochlea. Our model captures basic statistical features of the emissions: distributions of 1), emission frequencies; 2), number of emissions per ear; and 3), interemission intervals. In addition, the model reproduces systematic changes of the interemission intervals with frequency. We show that the mechanism for the preferred interemission interval in our model is the occurrence of synchronized clusters of oscillators.
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Affiliation(s)
- Florian Fruth
- Bernstein Center for Computational Neuroscience, Berlin, Germany; Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.
| | - Frank Jülicher
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Benjamin Lindner
- Bernstein Center for Computational Neuroscience, Berlin, Germany; Department of Physics, Humboldt University Berlin, Berlin, Germany.
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Bergevin C, Manley GA, Köppl C. Salient features of otoacoustic emissions are common across tetrapod groups and suggest shared properties of generation mechanisms. Proc Natl Acad Sci U S A 2015; 112:3362-7. [PMID: 25737537 PMCID: PMC4371923 DOI: 10.1073/pnas.1418569112] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Otoacoustic emissions (OAEs) are faint sounds generated by healthy inner ears that provide a window into the study of auditory mechanics. All vertebrate classes exhibit OAEs to varying degrees, yet the biophysical origins are still not well understood. Here, we analyzed both spontaneous (SOAE) and stimulus-frequency (SFOAE) otoacoustic emissions from a bird (barn owl, Tyto alba) and a lizard (green anole, Anolis carolinensis). These species possess highly disparate macromorphologies of the inner ear relative to each other and to mammals, thereby allowing for novel insights into the biomechanical mechanisms underlying OAE generation. All ears exhibited robust OAE activity, and our chief observation was that SFOAE phase accumulation between adjacent SOAE peak frequencies clustered about an integral number of cycles. Being highly similar to published results from human ears, we argue that these data indicate a common underlying generator mechanism of OAEs across all vertebrates, despite the absence of morphological features thought essential to mammalian cochlear mechanics. We suggest that otoacoustic emissions originate from phase coherence in a system of coupled oscillators, which is consistent with the notion of "coherent reflection" but does not explicitly require a mammalian-type traveling wave. Furthermore, comparison between SFOAE delays and auditory nerve fiber responses for the barn owl strengthens the notion that most OAE delay can be attributed to tuning.
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Affiliation(s)
- Christopher Bergevin
- Department of Physics & Astronomy and Centre for Vision Research, York University, Toronto, ON, M3J 1P3, Canada; and
| | - Geoffrey A Manley
- Cluster of Excellence "Hearing4all," Research Center Neurosensory Science, and Department of Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany
| | - Christine Köppl
- Cluster of Excellence "Hearing4all," Research Center Neurosensory Science, and Department of Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University, 26129 Oldenburg, Germany
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19
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Control of a hair bundle's mechanosensory function by its mechanical load. Proc Natl Acad Sci U S A 2015; 112:E1000-9. [PMID: 25691749 DOI: 10.1073/pnas.1501453112] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hair cells, the sensory receptors of the internal ear, subserve different functions in various receptor organs: they detect oscillatory stimuli in the auditory system, but transduce constant and step stimuli in the vestibular and lateral-line systems. We show that a hair cell's function can be controlled experimentally by adjusting its mechanical load. By making bundles from a single organ operate as any of four distinct types of signal detector, we demonstrate that altering only a few key parameters can fundamentally change a sensory cell's role. The motions of a single hair bundle can resemble those of a bundle from the amphibian vestibular system, the reptilian auditory system, or the mammalian auditory system, demonstrating an essential similarity of bundles across species and receptor organs.
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20
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Mhatre N. Active amplification in insect ears: mechanics, models and molecules. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2014; 201:19-37. [PMID: 25502323 DOI: 10.1007/s00359-014-0969-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 11/15/2014] [Accepted: 11/17/2014] [Indexed: 12/29/2022]
Abstract
Active amplification in auditory systems is a unique and sophisticated mechanism that expends energy in amplifying the mechanical input to the auditory system, to increase its sensitivity and acuity. Although known for decades from vertebrates, active auditory amplification was only discovered in insects relatively recently. It was first discovered from two dipterans, mosquitoes and flies, who hear with their light and compliant antennae; only recently has it been observed in the stiffer and heavier tympanal ears of an orthopteran. The discovery of active amplification in two distinct insect lineages with independently evolved ears, suggests that the trait may be ancestral, and other insects may possess it as well. This opens up extensive research possibilities in the field of acoustic communication, not just in auditory biophysics, but also in behaviour and neurobiology. The scope of this review is to establish benchmarks for identifying the presence of active amplification in an auditory system and to review the evidence we currently have from different insect ears. I also review some of the models that have been posited to explain the mechanism, both from vertebrates and insects and then review the current mechanical, neurobiological and genetic evidence for each of these models.
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Affiliation(s)
- Natasha Mhatre
- School of Biological Sciences, University of Bristol, Woodland road, Bristol, BS8 1UG, UK,
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21
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Amro RM, Neiman AB. Effect of bidirectional mechanoelectrical coupling on spontaneous oscillations and sensitivity in a model of hair cells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 90:052704. [PMID: 25493813 DOI: 10.1103/physreve.90.052704] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Indexed: 06/04/2023]
Abstract
Sensory hair cells of amphibians exhibit spontaneous activity in their hair bundles and membrane potentials, reflecting two distinct active amplification mechanisms employed in these peripheral mechanosensors. We use a two-compartment model of the bullfrog's saccular hair cell to study how the interaction between its mechanical and electrical compartments affects the emergence of distinct dynamical regimes, and the role of this interaction in shaping the response of the hair cell to weak mechanical stimuli. The model employs a Hodgkin-Huxley-type system for the basolateral electrical compartment and a nonlinear hair bundle oscillator for the mechanical compartment, which are coupled bidirectionally. In the model, forward coupling is provided by the mechanoelectrical transduction current, flowing from the hair bundle to the cell soma. Backward coupling is due to reverse electromechanical transduction, whereby variations of the membrane potential affect adaptation processes in the hair bundle. We isolate oscillation regions in the parameter space of the model and show that bidirectional coupling affects significantly the dynamics of the cell. In particular, self-sustained oscillations of the hair bundles and membrane potential can result from bidirectional coupling, and the coherence of spontaneous oscillations can be maximized by tuning the coupling strength. Consistent with previous experimental work, the model demonstrates that dynamical regimes of the hair bundle change in response to variations in the conductances of basolateral ion channels. We show that sensitivity of the hair cell to weak mechanical stimuli can be maximized by varying coupling strength, and that stochasticity of the hair bundle compartment is a limiting factor of the sensitivity.
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Affiliation(s)
- Rami M Amro
- Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA and Neuroscience Program, Ohio University, Athens, Ohio 45701, USA
| | - Alexander B Neiman
- Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA and Neuroscience Program, Ohio University, Athens, Ohio 45701, USA
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22
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Martin P. All that jazz coming out of my ears. Biophys J 2014; 107:800-2. [PMID: 25140414 DOI: 10.1016/j.bpj.2014.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/03/2014] [Accepted: 07/07/2014] [Indexed: 11/28/2022] Open
Affiliation(s)
- Pascal Martin
- Laboratoire Physico-Chimie Curie, Centre National de la Recherche Scientifique, UMR168, Paris, France; Institut Curie, Centre de Recherche, Paris, France; and Université Pierre et Marie Curie, Paris, France.
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Abstract
Uniquely among human senses, hearing is not simply a passive response to stimulation. Our auditory system is instead enhanced by an active process in cochlear hair cells that amplifies acoustic signals several hundred-fold, sharpens frequency selectivity and broadens the ear's dynamic range. Active motility of the mechanoreceptive hair bundles underlies the active process in amphibians and some reptiles; in mammals, this mechanism operates in conjunction with prestin-based somatic motility. Both individual hair bundles and the cochlea as a whole operate near a dynamical instability, the Hopf bifurcation, which accounts for the cardinal features of the active process.
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Manley GA. Fundamentals of Hearing in Amniote Vertebrates. PERSPECTIVES ON AUDITORY RESEARCH 2014. [DOI: 10.1007/978-1-4614-9102-6_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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25
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Geurten B, Spalthoff C, Göpfert M. Insect Hearing: Active Amplification in Tympanal Ears. Curr Biol 2013; 23:R950-2. [DOI: 10.1016/j.cub.2013.09.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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26
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Mora EC, Cobo-Cuan A, Macías-Escrivá F, Pérez M, Nowotny M, Kössl M. Mechanical tuning of the moth ear: distortion-product otoacoustic emissions and tympanal vibrations. J Exp Biol 2013; 216:3863-72. [PMID: 23868848 DOI: 10.1242/jeb.085902] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mechanical tuning of the ear in the moth Empyreuma pugione was investigated by distortion-product otoacoustic emissions (DPOAE) and laser Doppler vibrometry (LDV). DPOAE audiograms were assessed using a novel protocol that may be advantageous for non-invasive auditory studies in insects. To evoke DPOAE, two-tone stimuli within frequency and level ranges that generated a large matrix of values (960 frequency-level combinations) were used to examine the acoustic space in which the moth tympanum shows its best mechanical and acoustical responses. The DPOAE tuning curve derived from the response matrix resembles that obtained previously by electrophysiology, and is V-shaped and tuned to frequencies between 25 and 45 kHz with low Q10dB values of 1.21±0.26. In addition, while using a comparable stimulation regime, mechanical distortion in the displacement of the moth's tympanal membrane at the stigma was recorded with a laser Doppler vibrometer. The corresponding mechanical vibration audiograms were compared with DPOAE audiograms. Both types of audiograms have comparable shape, but most of the mechanical response fields are shifted towards lower frequencies. We showed for the first time in moths that DPOAE have a pronounced analogy in the vibration of the tympanic membrane where they may originate. Our work supports previous studies that point to the stigma (and the internally associated transduction machinery) as an important place of sound amplification in the moth ear, but also suggests a complex mechanical role for the rest of the transparent zone.
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Affiliation(s)
- Emanuel C Mora
- Research Group in Bioacoustics and Neuroethology, Department of Animal and Human Biology, Faculty of Biology, Havana University, 25 St. No. 455, Vedado, CP. 10400, Havana, Cuba
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27
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Mhatre N, Robert D. A tympanal insect ear exploits a critical oscillator for active amplification and tuning. Curr Biol 2013; 23:1952-7. [PMID: 24076240 PMCID: PMC3793861 DOI: 10.1016/j.cub.2013.08.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 06/23/2013] [Accepted: 08/05/2013] [Indexed: 11/05/2022]
Abstract
A dominant theme of acoustic communication is the partitioning of acoustic space into exclusive, species-specific niches to enable efficient information transfer. In insects, acoustic niche partitioning is achieved through auditory frequency filtering, brought about by the mechanical properties of their ears [1]. The tuning of the antennal ears of mosquitoes [2] and flies [3], however, arises from active amplification, a process similar to that at work in the mammalian cochlea [4]. Yet, the presence of active amplification in the other type of insect ears—tympanal ears—has remained uncertain [5]. Here we demonstrate the presence of active amplification and adaptive tuning in the tympanal ear of a phylogenetically basal insect, a tree cricket. We also show that the tree cricket exploits critical oscillator-like mechanics, enabling high auditory sensitivity and tuning to conspecific songs. These findings imply that sophisticated auditory mechanisms may have appeared even earlier in the evolution of hearing and acoustic communication than currently appreciated. Our findings also raise the possibility that frequency discrimination and directional hearing in tympanal systems may rely on physiological nonlinearities, in addition to mechanical properties, effectively lifting some of the physical constraints placed on insects by their small size [6] and prompting an extensive reexamination of invertebrate audition. The tympanal ears of a tree cricket use active amplification Active amplification and not passive resonance determines tuning to song frequency Active amplification and tuning have an “on” and an “off” state Crickets are the phylogenetically oldest insects with active auditory amplification
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Affiliation(s)
- Natasha Mhatre
- School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK.
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28
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van Dijk P, Manley GA. The effects of air pressure on spontaneous otoacoustic emissions of lizards. J Assoc Res Otolaryngol 2013; 14:309-19. [PMID: 23568746 PMCID: PMC3642271 DOI: 10.1007/s10162-013-0385-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 03/14/2013] [Indexed: 11/29/2022] Open
Abstract
Small changes of air pressure outside the eardrum of five lizard species led to changes in frequency, level, and peak width of spontaneous otoacoustic emissions (SOAE). In contrast to humans, these changes generally occurred at very small pressures (<20 mbar). As in humans, SOAE amplitudes were generally reduced. Changes of SOAE frequency were both positive and negative, while in humans, they are mostly positive. In addition, in lizards, these effects often showed obvious hysteresis and non-repeatability. The correlation between peak width and height was negative in two species (comparable to humans) and positive in one species. In two other species, no correlation was found. Consequently, a simple oscillator model that explained the negative correlation in humans could not be generally applied to lizards. This presumably reflects the fact that in lizards, the spontaneous otoacoustic emission of sound from the ear consists of a combination of stable oscillations (as in humans), unstable narrow-band oscillations, and broad-band emissions, evident as "plateaus" in emission spectra.
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Affiliation(s)
- Pim van Dijk
- />Department of Otorhinolaryngology, Head & Neck Surgery, University Medical Center Groningen, University of Groningen, P.O. Box 30001, 9700 RB Groningen, The Netherlands
- />Graduate School of Medical Sciences, Research School of Behavioral and Cognitive Neurosciences, University of Groningen, Groningen, The Netherlands
| | - Geoffrey A. Manley
- />Cochlear and Auditory Brainstem Physiology, Department of Neuroscience, Faculty VI, Carl von Ossietzky University, 26111 Oldenburg, Germany
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29
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Effects of cochlear loading on the motility of active outer hair cells. Proc Natl Acad Sci U S A 2013; 110:5474-9. [PMID: 23509256 DOI: 10.1073/pnas.1302911110] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Outer hair cells (OHCs) power the amplification of sound-induced vibrations in the mammalian inner ear through an active process that involves hair-bundle motility and somatic motility. It is unclear, though, how either mechanism can be effective at high frequencies, especially when OHCs are mechanically loaded by other structures in the cochlea. We address this issue by developing a model of an active OHC on the basis of observations from isolated cells, then we use the model to predict the response of an active OHC in the intact cochlea. We find that active hair-bundle motility amplifies the receptor potential that drives somatic motility. Inertial loading of a hair bundle by the tectorial membrane reduces the bundle's reactive load, allowing the OHC's active motility to influence the motion of the cochlear partition. The system exhibits enhanced sensitivity and tuning only when it operates near a dynamical instability, a Hopf bifurcation. This analysis clarifies the roles of cochlear structures and shows how the two mechanisms of motility function synergistically to create the cochlear amplifier. The results suggest that somatic motility evolved to enhance a preexisting amplifier based on active hair-bundle motility, thus allowing mammals to hear high-frequency sounds.
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30
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Mechanical overstimulation of hair bundles: suppression and recovery of active motility. PLoS One 2013; 8:e58143. [PMID: 23505461 PMCID: PMC3591416 DOI: 10.1371/journal.pone.0058143] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Accepted: 01/30/2013] [Indexed: 11/19/2022] Open
Abstract
We explore the effects of high-amplitude mechanical stimuli on hair bundles of the bullfrog sacculus. Under in vitro conditions, these bundles exhibit spontaneous limit cycle oscillations. Prolonged deflection exerted two effects. First, it induced an offset in the position of the bundle. Recovery to the original position displayed two distinct time scales, suggesting the existence of two adaptive mechanisms. Second, the stimulus suppressed spontaneous oscillations, indicating a change in the hair bundle’s dynamic state. After cessation of the stimulus, active bundle motility recovered with time. Both effects were dependent on the duration of the imposed stimulus. External calcium concentration also affected the recovery to the oscillatory state. Our results indicate that both offset in the bundle position and calcium concentration control the dynamic state of the bundle.
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31
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Olson ES, Duifhuis H, Steele CR. Von Békésy and cochlear mechanics. Hear Res 2012; 293:31-43. [PMID: 22633943 PMCID: PMC3572775 DOI: 10.1016/j.heares.2012.04.017] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 04/17/2012] [Accepted: 04/23/2012] [Indexed: 10/28/2022]
Abstract
Georg Békésy laid the foundation for cochlear mechanics, foremost by demonstrating the traveling wave that is the substrate for mammalian cochlear mechanical processing. He made mechanical measurements and physical models in order to understand that fundamental cochlear response. In this tribute to Békésy we make a bridge between modern traveling wave observations and those of Békésy, discuss the mechanical properties and measurements that he considered to be so important, and touch on the range of computational traveling wave models.
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Affiliation(s)
| | - Hendrikus Duifhuis
- Faculty of Mathematics and Natural Sciences, University of Groningen, Netherlands
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32
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Wit HP, van Dijk P, Manley GA. A model for the relation between stimulus frequency and spontaneous otoacoustic emissions in lizard papillae. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2012; 132:3273-3279. [PMID: 23145611 DOI: 10.1121/1.4754535] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Spontaneous otoacoustic emissions (SOAEs) and stimulus frequency otoacoustic emissions (SFOAEs) have been described from lizard ears. Although there are several models for these systems, none has modeled the characteristics of both of these types of otoacoustic emissions based upon their being derived from hair cells as active oscillators. Data from the ears of two lizard species, one lacking a tectorial membrane and one with a chain of tectorial sallets, as described by Bergevin et al. ["Coupled, active oscillators and lizard otoacoustic emissions," AIP Conf. Proc. 1403, 453 (2008)], are modeled as an array of coupled self-sustained oscillators. The model, originally developed by Vilfan and Duke ["Frequency clustering in spontaneous otoacoustic emissions from a lizard's ear," Biophys. J. 95, 4622-4630 (2008)], well describes both the amplitude and phase characteristics of SFOAEs and the relation between SFOAEs and SOAEs.
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Affiliation(s)
- Hero P Wit
- Department of Otorhinolaryngology/Head and Neck Surgery, University of Groningen, University Medical Center Groningen, P.O. Box 30.001, 9700RB Groningen, The Netherlands.
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Fredrickson-Hemsing L, Strimbu CE, Roongthumskul Y, Bozovic D. Dynamics of freely oscillating and coupled hair cell bundles under mechanical deflection. Biophys J 2012; 102:1785-92. [PMID: 22768934 DOI: 10.1016/j.bpj.2012.03.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 02/21/2012] [Accepted: 03/02/2012] [Indexed: 10/28/2022] Open
Abstract
In vitro, attachment to the overlying membrane was found to affect the resting position of the hair cell bundles of the bullfrog sacculus. To assess the effects of such a deflection on mechanically decoupled hair bundles, comparable offsets were imposed on decoupled spontaneously oscillating bundles. Strong modulation was observed in their dynamic state under deflection, with qualitative changes in the oscillation profile, amplitude, and characteristic frequency of oscillation seen in response to stimulus. Large offsets were found to arrest spontaneous oscillation, with subsequent recovery upon reversal of the stimulus. The dynamic state of the hair bundle displayed hysteresis and a dependence on the direction of the imposed offset. The coupled system of hair bundles, with the overlying membrane left on top of the preparation, also exhibited a dependence on offset position, with an increase in the linear response function observed under deflections in the inhibitory direction.
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34
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Patel SH, Salvi JD, Maoiléidigh DÓ, Hudspeth AJ. Frequency-selective exocytosis by ribbon synapses of hair cells in the bullfrog's amphibian papilla. J Neurosci 2012; 32:13433-8. [PMID: 23015434 PMCID: PMC3468150 DOI: 10.1523/jneurosci.1246-12.2012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 07/31/2012] [Accepted: 08/05/2012] [Indexed: 01/25/2023] Open
Abstract
The activity of auditory afferent fibers depends strongly on the frequency of stimulation. Although the bullfrog's amphibian papilla lacks the flexible basilar membrane that effects tuning in mammals, its afferents display comparable frequency selectivity. Seeking additional mechanisms of tuning in this organ, we monitored the synaptic output of hair cells by measuring changes in their membrane capacitance during sinusoidal electrical stimulation at various frequencies. Using perforated-patch recordings, we found that individual hair cells displayed frequency selectivity in synaptic exocytosis within the frequency range sensed by the amphibian papilla. Moreover, each cell's tuning varied in accordance with its tonotopic position. Using confocal imaging, we observed a tonotopic gradient in the concentration of proteinaceous Ca(2+) buffers. A model for synaptic release suggests that this gradient maintains the sharpness of tuning. We conclude that hair cells of the amphibian papilla use synaptic tuning as an additional mechanism for sharpening their frequency selectivity.
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Affiliation(s)
- Suchit H. Patel
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York 10065
| | - Joshua D. Salvi
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York 10065
| | - Dáibhid Ó Maoiléidigh
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York 10065
| | - A. J. Hudspeth
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York 10065
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35
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Abstract
It has been proposed that OAEs be classified not on the basis of the stimuli used to evoke them, but on the mechanisms that produce them (Shera and Guinan, 1999). One branch of this taxonomy focuses on a coherent reflection model and explicitly describes interrelationships between spontaneous emissions (SOAEs) and stimulus-frequency emissions (SFOAEs). The present study empirically examines SOAEs and SFOAEs from individual ears within the context of model predictions, using a low stimulus level (20 dB SPL) to evoke SFOAEs. Emissions were recorded from ears of normal-hearing young adults, both with and without prominent SOAE activity. When spontaneous activity was observed, SFOAEs demonstrated a localized increase about the SOAE peaks. The converse was not necessarily true though, i.e., robust SFOAEs could be measured where no SOAE peaks were observed. There was no significant difference in SFOAE phase-gradient delays between those with and without observable SOAE activity. However, delays were larger for a 20 dB SPL stimulus level than those previously reported for 40 dB SPL. The total amount of SFOAE phase accumulation occurring between adjacent SOAE peaks tended to cluster about an integral number of cycles. Overall, the present data appear congruous with predictions stemming from the coherent reflection model and support the notion that such comparisons ideally are made with emissions evoked using relatively lower stimulus levels.
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36
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Progress in cochlear physiology after Békésy. Hear Res 2012; 293:12-20. [PMID: 22633944 DOI: 10.1016/j.heares.2012.05.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 05/08/2012] [Accepted: 05/10/2012] [Indexed: 11/20/2022]
Abstract
In the fifty years since Békésy was awarded the Nobel Prize, cochlear physiology has blossomed. Many topics that are now current are things Békésy could not have imagined. In this review we start by describing progress in understanding the origin of cochlear gross potentials, particularly the cochlear microphonic, an area in which Békésy had extensive experience. We then review progress in areas of cochlear physiology that were mostly unknown to Békésy, including: (1) stereocilia mechano-electrical transduction, force production, and response amplification, (2) outer hair cell (OHC) somatic motility and its molecular basis in prestin, (3) cochlear amplification and related micromechanics, including the evidence that prestin is the main motor for cochlear amplification, (4) the influence of the tectorial membrane, (5) cochlear micromechanics and the mechanical drives to inner hair cell stereocilia, (6) otoacoustic emissions, and (7) olivocochlear efferents and their influence on cochlear physiology. We then return to a subject that Békésy knew well: cochlear fluids and standing currents, as well as our present understanding of energy dependence on the lateral wall of the cochlea. Finally, we touch on cochlear pathologies including noise damage and aging, with an emphasis on where the field might go in the future.
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37
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Phantom tones and suppressive masking by active nonlinear oscillation of the hair-cell bundle. Proc Natl Acad Sci U S A 2012; 109:E1344-51. [PMID: 22556264 DOI: 10.1073/pnas.1202426109] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Processing of two-tone stimuli by the auditory system introduces prominent masking of one frequency component by the other as well as additional "phantom" tones that are absent in the sound input. Mechanical correlates of these psychophysical phenomena have been observed in sound-evoked mechanical vibrations of the mammalian cochlea and are thought to originate in sensory hair cells from the intrinsic nonlinearity associated with mechano-electrical transduction by ion channels. However, nonlinearity of the transducer is not sufficient to explain the rich phenomenology of two-tone interferences in hearing. Here we show that active oscillatory movements of single hair-cell bundles elicit two-tone suppression and distortions that are shaped by nonlinear amplification of periodic stimuli near the characteristic frequency of spontaneous oscillations. When both stimulus frequencies enter the bandwidth of the hair-bundle amplifier, two-tone interferences display level functions that are characteristic both of human psychoacoustics and of in vivo mechanical measurements in auditory organs. Our work distinguishes the frequency-dependent nonlinearity that emerges from the active process that drives the hair bundle into spontaneous oscillations from the passive nonlinear compliance associated with the direct gating of transduction channels by mechanical force. Numerical simulations based on a generic description of an active dynamical system poised near an oscillatory instability--a Hopf bifurcation--account quantitatively for our experimental observations. In return, we conclude that the properties of two-tone interferences in hearing betray the workings of self-sustained "critical" oscillators, which function as nonlinear amplifying elements in the inner ear.
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Strimbu CE, Fredrickson-Hemsing L, Bozovic D. Coupling and elastic loading affect the active response by the inner ear hair cell bundles. PLoS One 2012; 7:e33862. [PMID: 22479461 PMCID: PMC3313926 DOI: 10.1371/journal.pone.0033862] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 02/18/2012] [Indexed: 11/19/2022] Open
Abstract
Active hair bundle motility has been proposed to underlie the amplification mechanism in the auditory endorgans of non-mammals and in the vestibular systems of all vertebrates, and to constitute a crucial component of cochlear amplification in mammals. We used semi-intact in vitro preparations of the bullfrog sacculus to study the effects of elastic mechanical loading on both natively coupled and freely oscillating hair bundles. For the latter, we attached glass fibers of different stiffness to the stereocilia and observed the induced changes in the spontaneous bundle movement. When driven with sinusoidal deflections, hair bundles displayed phase-locked response indicative of an Arnold Tongue, with the frequency selectivity highest at low amplitudes and decreasing under stronger stimulation. A striking broadening of the mode-locked response was seen with increasing stiffness of the load, until approximate impedance matching, where the phase-locked response remained flat over the physiological range of frequencies. When the otolithic membrane was left intact atop the preparation, the natural loading of the bundles likewise decreased their frequency selectivity with respect to that observed in freely oscillating bundles. To probe for signatures of the active process under natural loading and coupling conditions, we applied transient mechanical stimuli to the otolithic membrane. Following the pulses, the underlying bundles displayed active movement in the opposite direction, analogous to the twitches observed in individual cells. Tracking features in the otolithic membrane indicated that it moved in phase with the bundles. Hence, synchronous active motility evoked in the system of coupled hair bundles by external input is sufficient to displace large overlying structures.
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Affiliation(s)
- Clark Elliott Strimbu
- Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, California, United States of America
| | - Lea Fredrickson-Hemsing
- Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, California, United States of America
| | - Dolores Bozovic
- Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, California, United States of America
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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The physical basis of active mechanosensitivity by the hair-cell bundle. Curr Opin Otolaryngol Head Neck Surg 2011; 19:369-75. [DOI: 10.1097/moo.0b013e32834a8c33] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Moir HM, Jackson JC, Windmill JFC. No evidence for DPOAEs in the mechanical motion of the locust tympanum. J Exp Biol 2011; 214:3165-72. [DOI: 10.1242/jeb.056465] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Distortion-product otoacoustic emissions (DPOAEs) are present in non-linear hearing organs, and for low-intensity sounds are a by-product of active processes. In vertebrate ears they are considered to be due to hair cell amplification of sound in the cochlea; however, certain animals lacking a cochlea and hair cells are also reported to be capable of DPOAEs. In the Insecta, DPOAEs have been recorded from the locust auditory organ. However, the site of generation of these DPOAEs and the physiological mechanisms causing their presence in the locust ear are not yet understood, despite there being a number of potential places in the tympanal organ that could be capable of generating DPOAEs. This study aimed to record locust tympanal membrane vibration using a laser Doppler vibrometer in order to identify a distinct place of DPOAE generation on the membrane. Two species of locust were investigated over a range of frequencies and levels of acoustic stimulus, mirroring earlier acoustic recording studies; however, the current experiments were carried out in an open acoustic system. The laser measurements did not find any evidence of mechanical motion on the tympanal membrane related to the expected DPOAE frequencies. The results of the current study therefore could not confirm the presence of DPOAEs in the locust ear through the mechanics of the tympanal membrane. Experiments were also carried out to test how membrane behaviour altered when the animals were in a state of hypoxia, as this was previously found to decrease DPOAE magnitude, suggesting a metabolic sensitivity. However, hypoxia did not have any significant effect on the membrane mechanics. The location of the mechanical generation of DPOAEs in the locust's ear, and therefore the basis for the related physiological mechanisms, thus remains unknown.
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Affiliation(s)
- Hannah M. Moir
- Centre for Ultrasonic Engineering, Department of Electronic and Electrical Engineering, University of Strathclyde, Royal College Building, 204 George Street, Glasgow G1 1XW, UK
| | - Joseph C. Jackson
- Centre for Ultrasonic Engineering, Department of Electronic and Electrical Engineering, University of Strathclyde, Royal College Building, 204 George Street, Glasgow G1 1XW, UK
| | - James F. C. Windmill
- Centre for Ultrasonic Engineering, Department of Electronic and Electrical Engineering, University of Strathclyde, Royal College Building, 204 George Street, Glasgow G1 1XW, UK
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Stasiunas A, Verikas A, Bacauskiene M, Miliauskas R. An adaptive panoramic filter bank as a qualitative model of the filtering system of the cochlea: the peculiarities in linear and nonlinear mode. Med Eng Phys 2011; 34:187-94. [PMID: 21803637 DOI: 10.1016/j.medengphy.2011.07.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 07/02/2011] [Accepted: 07/11/2011] [Indexed: 10/18/2022]
Abstract
Outer hair cells in the cochlea of the ear, together with the local structures of the basilar membrane, reticular lamina and tectorial membrane constitute the adaptive primary filters (PF) of the second order. We used them for designing a serial-parallel signal filtering system. We determined a rational number of the PF included in Gaussian channels of the system, summation weights of the output signals, and distribution of the PF along the basilar membrane. A Gaussian panoramic filter bank each channel of which consists of five PF is presented as an example. The properties of the PF, the channel and the filter bank operating in the linear and nonlinear modes are determined during adaptation and under efferent control. The results suggest that application of biological filtering principles can be useful for designing cochlear implants with new speech encoding strategies.
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Affiliation(s)
- Antanas Stasiunas
- Department of Electrical & Control Equipment, Kaunas University of Technology, LT-51368, Kaunas, Lithuania
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Köppl C. Birds – same thing, but different? Convergent evolution in the avian and mammalian auditory systems provides informative comparative models. Hear Res 2011; 273:65-71. [DOI: 10.1016/j.heares.2010.03.095] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 02/26/2010] [Accepted: 03/01/2010] [Indexed: 10/19/2022]
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Manley GA, Fuchs PA. Recent advances in comparative hearing. Hear Res 2011; 273:1-6. [PMID: 21236326 DOI: 10.1016/j.heares.2011.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 01/10/2011] [Accepted: 01/10/2011] [Indexed: 10/18/2022]
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Möckel D, Seyfarth EA, Kössl M. Otoacoustic emissions in bushcricket ears: general characteristics and the influence of the neuroactive insecticide pymetrozine. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2010; 197:193-202. [PMID: 21052684 DOI: 10.1007/s00359-010-0599-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 10/05/2010] [Accepted: 10/08/2010] [Indexed: 10/18/2022]
Abstract
The tympanal organ of the bushcricket Mecopoda elongata emits pronounced distortion-product otoacoustic emissions (DPOAEs). Their characteristics are comparable to those measured in other insects, such as locusts and moths, with the 2f1-f2 emission being the most prominent one. Yet the site of their generation is still unclear. The spatial separation between the sound receiving spiracle and the hearing organ in this species allows manipulations of the sensory cells without interfering with the acoustical measurements. We tried to interfere with the DPOAE generation by pharmacologically influencing the tympanal organ using the insecticide pymetrozine. The compound appears to act selectively on scolopidia, i.e., the mechanosensor type characteristically constituting tympanal organs. Pymetrozine solutions were applied as closely as possible to the scolopidia via a cuticle opening in the tibia, distally to the organ. Applications of pymetrozine at concentrations between 10(-3) and 10(-7) M to the tympanal organ led to a pronounced and irreversible decrease of the DPOAE amplitudes.
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Affiliation(s)
- Doreen Möckel
- Institut für Zellbiologie und Neurowissenschaft, J. W. Goethe-Universität, Biologie Campus, Haus A, Siesmayerstrasse 70, 60323, Frankfurt am Main, Germany.
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Abstract
This composite article is intended to give the experts in the field of cochlear mechanics an opportunity to voice their personal opinion on the one mechanism they believe dominates cochlear amplification in mammals. A collection of these ideas are presented here for the auditory community and others interested in the cochlear amplifier. Each expert has given their own personal view on the topic and at the end of their commentary they have suggested several experiments that would be required for the decisive mechanism underlying the cochlear amplifier. These experiments are presently lacking but if successfully performed would have an enormous impact on our understanding of the cochlear amplifier.
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Ramunno-Johnson D, Strimbu C, Kao A, Fredrickson Hemsing L, Bozovic D. Effects of the somatic ion channels upon spontaneous mechanical oscillations in hair bundles of the inner ear. Hear Res 2010; 268:163-71. [DOI: 10.1016/j.heares.2010.05.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 05/21/2010] [Accepted: 05/25/2010] [Indexed: 11/28/2022]
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Gelfand M, Piro O, Magnasco MO, Hudspeth AJ. Interactions between hair cells shape spontaneous otoacoustic emissions in a model of the tokay gecko's cochlea. PLoS One 2010; 5:e11116. [PMID: 20559557 PMCID: PMC2886102 DOI: 10.1371/journal.pone.0011116] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Accepted: 05/19/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The hearing of tetrapods including humans is enhanced by an active process that amplifies the mechanical inputs associated with sound, sharpens frequency selectivity, and compresses the range of responsiveness. The most striking manifestation of the active process is spontaneous otoacoustic emission, the unprovoked emergence of sound from an ear. Hair cells, the sensory receptors of the inner ear, are known to provide the energy for such emissions; it is unclear, though, how ensembles of such cells collude to power observable emissions. METHODOLOGY AND PRINCIPAL FINDINGS We have measured and modeled spontaneous otoacoustic emissions from the ear of the tokay gecko, a convenient experimental subject that produces robust emissions. Using a van der Pol formulation to represent each cluster of hair cells within a tonotopic array, we have examined the factors that influence the cooperative interaction between oscillators. CONCLUSIONS AND SIGNIFICANCE A model that includes viscous interactions between adjacent hair cells fails to produce emissions similar to those observed experimentally. In contrast, elastic coupling yields realistic results, especially if the oscillators near the ends of the array are weakened so as to minimize boundary effects. Introducing stochastic irregularity in the strength of oscillators stabilizes peaks in the spectrum of modeled emissions, further increasing the similarity to the responses of actual ears. Finally, and again in agreement with experimental findings, the inclusion of a pure-tone external stimulus repels the spectral peaks of spontaneous emissions. Our results suggest that elastic coupling between oscillators of slightly differing strength explains several properties of the spontaneous otoacoustic emissions in the gecko.
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Affiliation(s)
- Michael Gelfand
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York, United States of America
| | - Oreste Piro
- Departament de Física and Institute for Cross-Disciplinary Physics and Complex Systems (IFISC), Spanish National Research Council (CSIC) - University of the Balearic Islands (UIB), Universitat de les Illes Balears, Palma de Mallorca, Spain
| | - Marcelo O. Magnasco
- Laboratory of Mathematical Physics, The Rockefeller University, New York, New York, United States of America
| | - A. J. Hudspeth
- Howard Hughes Medical Institute and Laboratory of Sensory Neuroscience, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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Hudspeth AJ, Jülicher F, Martin P. A critique of the critical cochlea: Hopf--a bifurcation--is better than none. J Neurophysiol 2010; 104:1219-29. [PMID: 20538769 DOI: 10.1152/jn.00437.2010] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The sense of hearing achieves its striking sensitivity, frequency selectivity, and dynamic range through an active process mediated by the inner ear's mechanoreceptive hair cells. Although the active process renders hearing highly nonlinear and produces a wealth of complex behaviors, these various characteristics may be understood as consequences of a simple phenomenon: the Hopf bifurcation. Any critical oscillator operating near this dynamic instability manifests the properties demonstrated for hearing: amplification with a specific form of compressive nonlinearity and frequency tuning whose sharpness depends on the degree of amplification. Critical oscillation also explains spontaneous otoacoustic emissions as well as the spectrum and level dependence of the ear's distortion products. Although this has not been realized, several valuable theories of cochlear function have achieved their success by incorporating critical oscillators.
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Affiliation(s)
- A J Hudspeth
- The Rockefeller University, HHMI and Laboratory of Sensory Neuroscience, Campus Box 314, 1230 York Avenue, New York, NY 10065-6399, USA.
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Strimbu C, Kao A, Tokuda J, Ramunno-Johnson D, Bozovic D. Dynamic state and evoked motility in coupled hair bundles of the bullfrog sacculus. Hear Res 2010; 265:38-45. [DOI: 10.1016/j.heares.2010.03.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 03/03/2010] [Accepted: 03/05/2010] [Indexed: 10/19/2022]
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