1
|
Neal SJ, Rajasekaran A, Jusić N, Taylor L, Read M, Alfandari D, Pignoni F, Moody SA. Using Xenopus to discover new candidate genes involved in BOR and other congenital hearing loss syndromes. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2024; 342:212-240. [PMID: 37830236 PMCID: PMC11014897 DOI: 10.1002/jez.b.23222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 08/15/2023] [Accepted: 09/14/2023] [Indexed: 10/14/2023]
Abstract
Hearing in infants is essential for brain development, acquisition of verbal language skills, and development of social interactions. Therefore, it is important to diagnose hearing loss soon after birth so that interventions can be provided as early as possible. Most newborns in the United States are screened for hearing deficits and commercially available next-generation sequencing hearing loss panels often can identify the causative gene, which may also identify congenital defects in other organs. One of the most prevalent autosomal dominant congenital hearing loss syndromes is branchio-oto-renal syndrome (BOR), which also presents with defects in craniofacial structures and the kidney. Currently, mutations in three genes, SIX1, SIX5, and EYA1, are known to be causative in about half of the BOR patients that have been tested. To uncover new candidate genes that could be added to congenital hearing loss genetic screens, we have combined the power of Drosophila mutants and protein biochemical assays with the embryological advantages of Xenopus, a key aquatic animal model with a high level of genomic similarity to human, to identify potential Six1 transcriptional targets and interacting proteins that play a role during otic development. We review our transcriptomic, yeast 2-hybrid, and proteomic approaches that have revealed a large number of new candidates. We also discuss how we have begun to identify how Six1 and co-factors interact to direct developmental events necessary for normal otic development.
Collapse
Affiliation(s)
- Scott J. Neal
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Anindita Rajasekaran
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Nisveta Jusić
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Louis Taylor
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Mai Read
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Dominique Alfandari
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Francesca Pignoni
- Department of Neuroscience and Physiology, Upstate Medical University, Syracuse, NY, USA
| | - Sally A. Moody
- Department of Anatomy and Cell Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
| |
Collapse
|
2
|
Maria B, Tonini JF, Rebouças R, Toledo LF. Hidden shifts in allometry scaling between sound production and perception in anurans. PeerJ 2023; 11:e16322. [PMID: 37941929 PMCID: PMC10629387 DOI: 10.7717/peerj.16322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 09/29/2023] [Indexed: 11/10/2023] Open
Abstract
Background Animal communication consists of signal production and perception, which are crucial for social interactions. The main form used by anurans is auditory communication, in most cases produced as advertisement calls. Furthermore, sound perception happens mainly through an external tympanic membrane, and plays an important role in social behavior. In this study, we evaluated the influence of body and tympanic membrane sizes on call frequency across the phylogeny of anurans. Methods We use data on snout-vent length, tympanic membrane diameter, and dominant frequency of the advertisement call from the literature and from natural history museum collections. We mapped these traits across the anuran phylogeny and tested different models of diversification. Our final dataset includes data on body size, tympanic membrane size, and call dominant frequency of 735 anuran species. Results The best explanatory model includes body and tympanum size with no interaction term. Although our results show that call frequency is strongly constrained by body and tympanum size, we identify five evolutionary shifts in allometry from that ancestral constraint. We relate these evolutionary shifts to the background noise experienced by populations. Body size is important for myriad ecological interactions and tympanum size is strongly associated with female call frequency preferences. Thus, allometric escape in frog calls might arise through environmental selection such as breeding in fast flowing or soundscape competition, as well as sexual selection linked to tympanum size.
Collapse
Affiliation(s)
- Bruna Maria
- Laboratório de História Natural de Anfíbios Brasileiros, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil
| | - João F.R. Tonini
- Department of Biology, University of Richmond, Richmond, VA, United States of America
| | - Raoni Rebouças
- Laboratório de História Natural de Anfíbios Brasileiros, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil
- Laboratório de Ecologia Evolutiva de Anfíbios, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais, Brazil
- Programa de Pós Graduação em Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
| | - Luís Felipe Toledo
- Laboratório de História Natural de Anfíbios Brasileiros, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil
| |
Collapse
|
3
|
Descending projections to the auditory midbrain: evolutionary considerations. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2023; 209:131-143. [PMID: 36323876 PMCID: PMC9898193 DOI: 10.1007/s00359-022-01588-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 10/12/2022] [Accepted: 10/14/2022] [Indexed: 11/06/2022]
Abstract
The mammalian inferior colliculus (IC) is massively innervated by multiple descending projection systems. In addition to a large projection from the auditory cortex (AC) primarily targeting the non-lemniscal portions of the IC, there are less well-characterized projections from non-auditory regions of the cortex, amygdala, posterior thalamus and the brachium of the IC. By comparison, the frog auditory midbrain, known as the torus semicircularis, is a large auditory integration center that also receives descending input, but primarily from the posterior thalamus and without a projection from a putative cortical homolog: the dorsal pallium. Although descending projections have been implicated in many types of behaviors, a unified understanding of their function has not yet emerged. Here, we take a comparative approach to understanding the various top-down modulators of the IC to gain insights into their functions. One key question that we identify is whether thalamotectal projections in mammals and amphibians are homologous and whether they interact with evolutionarily more newly derived projections from the cerebral cortex. We also consider the behavioral significance of these descending pathways, given anurans' ability to navigate complex acoustic landscapes without the benefit of a corticocollicular projection. Finally, we suggest experimental approaches to answer these questions.
Collapse
|
4
|
An In Vitro Study on Prestin Analog Gene in the Bullfrog Hearing Organs. Neural Plast 2020; 2020:3570732. [PMID: 32714383 PMCID: PMC7352134 DOI: 10.1155/2020/3570732] [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: 02/07/2020] [Revised: 04/22/2020] [Accepted: 05/20/2020] [Indexed: 11/18/2022] Open
Abstract
The prestin-based active process in the mammalian outer hair cells (OHCs) is believed to play a crucial role in auditory signal amplification in the cochlea. Prestin belongs to an anion transporter family (SLC26A). It is densely expressed in the OHC lateral plasma membrane and functions as a voltage-dependent motor protein. Analog genes can be found in the genome of nonmammalian species, but their functions in hearing are poorly understood. In the present study, we used the gerbil prestin sequence as a template and identified an analog gene in the bullfrog genome. We expressed the gene in a stable cell line (HEK293T) and performed patch-clamp recording. We found that these cells exhibited prominent nonlinear capacitance (NLC), a widely accepted assay for prestin functioning as a motor protein. Upon close examination, the key parameters of this NLC are comparable to that conferred by the gerbil prestin, and nontransfected cells failed to display NLC. Lastly, we performed patch-clamp recording in HCs of all three hearing organs in bullfrog. HCs in both the sacculus and the amphibian papilla exhibited a capacitance profile that is similar to NLC while HCs in the basilar papilla showed no sign of NLC. Whether or not this NLC-like capacitance change is involved in auditory signal amplification certainly requires further examination; our results represent the first and necessary step in revealing possible roles of prestin in the active hearing processes found in many nonmammalian species.
Collapse
|
5
|
Neilson KM, Abbruzzesse G, Kenyon K, Bartolo V, Krohn P, Alfandari D, Moody SA. Pa2G4 is a novel Six1 co-factor that is required for neural crest and otic development. Dev Biol 2017; 421:171-182. [PMID: 27940157 PMCID: PMC5221411 DOI: 10.1016/j.ydbio.2016.11.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 11/15/2016] [Accepted: 11/28/2016] [Indexed: 11/29/2022]
Abstract
Mutations in SIX1 and in its co-factor, EYA1, underlie Branchiootorenal Spectrum disorder (BOS), which is characterized by variable branchial arch, otic and kidney malformations. However, mutations in these two genes are identified in only half of patients. We screened for other potential co-factors, and herein characterize one of them, Pa2G4 (aka Ebp1/Plfap). In human embryonic kidney cells, Pa2G4 binds to Six1 and interferes with the Six1-Eya1 complex. In Xenopus embryos, knock-down of Pa2G4 leads to down-regulation of neural border zone, neural crest and cranial placode genes, and concomitant expansion of neural plate genes. Gain-of-function leads to a broader neural border zone, expanded neural crest and altered cranial placode domains. In loss-of-function assays, the later developing otocyst is reduced in size, which impacts gene expression. In contrast, the size of the otocyst in gain-of-function assays is not changed but the expression domains of several otocyst genes are reduced. Together these findings establish an interaction between Pa2G4 and Six1, and demonstrate that it has an important role in the development of tissues affected in BOS. Thereby, we suggest that pa2g4 is a potential candidate gene for BOS.
Collapse
Affiliation(s)
- Karen M Neilson
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
| | - Genevieve Abbruzzesse
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Kristy Kenyon
- Department of Biology, Hobart and William Smith Colleges, Geneva, NY, USA
| | - Vanessa Bartolo
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Patrick Krohn
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
| | - Dominique Alfandari
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Sally A Moody
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA.
| |
Collapse
|
6
|
Do Green Treefrogs Use Social Information to Orient Outside the Breeding Season? Zool Stud 2016; 55:e17. [PMID: 31966162 DOI: 10.6620/zs.2016.55-17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 01/01/2016] [Indexed: 11/18/2022]
Abstract
Gerlinde Höbel and Ashley Christie (2016) To decide efficiently where to forage, rest or breed, animals need information about their environment, which they may gather by monitoring the behavior of others. For example, attending to the signals of conspecifics or heterospecifics with similar habitat requirements may facilitate habitat choice. Such social information use seems taxonomically widespread, yet there is currently a dearth of information for amphibians. Anuran amphibians, with their highly developed auditory system and robust phonotaxis towards advertisement calls when searching for mates seem predisposed to use this hearing capability in other behavioral contexts. We conducted playback experiments to test whether anurans exploit acoustic signals in a non-reproductive context. In our experiments female Green Treefrogs did not show phonotaxis to signals associated with the presence of other frogs, and the orientation and speed of their movement was not different from animals randomly moving inside a silent arena. Previous studies documenting social information use in anurans have tested reproductively active frogs during the breeding season. By contrast, our study examined non-reproductive animals, and these did not approach social signals. We propose two non-exclusive hypotheses for this observed difference in phonotaxis behavior: (1) attending to social signals is restricted to ecologically most relevant time periods in a frogs life (i.e., finding breeding sites during the mating season), or (2) the ability of acoustic signals to stimulate the auditory system may be influenced by hormone levels regulating the reproductive state.
Collapse
|
7
|
Moody SA, Neilson KM, Kenyon KL, Alfandari D, Pignoni F. Using Xenopus to discover new genes involved in branchiootorenal spectrum disorders. Comp Biochem Physiol C Toxicol Pharmacol 2015; 178:16-24. [PMID: 26117063 PMCID: PMC4662879 DOI: 10.1016/j.cbpc.2015.06.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 06/16/2015] [Accepted: 06/17/2015] [Indexed: 12/14/2022]
Abstract
Congenital hearing loss is an important clinical problem because, without early intervention, affected children do not properly acquire language and consequently have difficulties developing social skills. Although most newborns in the US are screened for hearing deficits, even earlier diagnosis can be made with prenatal genetic screening. Genetic screening that identifies the relevant mutated gene can also warn about potential congenital defects in organs not related to hearing. We will discuss efforts to identify new candidate genes that underlie the Branchiootorenal spectrum disorders in which affected children have hearing deficits and are also at risk for kidney defects. Mutations in two genes, SIX1 and EYA1, have been identified in about half of the patients tested. To uncover new candidate genes, we have used the aquatic animal model, Xenopus laevis, to identify genes that are part of the developmental genetic pathway of Six1 during otic and kidney development. We have already identified a large number of potential Six1 transcriptional targets and candidate co-factor proteins that are expressed at the right time and in the correct tissues to interact with Six1 during development. We discuss the advantages of using this system for gene discovery in a human congenital hearing loss syndrome.
Collapse
Affiliation(s)
- Sally A Moody
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA.
| | - Karen M Neilson
- Department of Anatomy and Regenerative Biology, George Washington University, School of Medicine and Health Sciences, Washington, DC, USA
| | - Kristy L Kenyon
- Department of Biology, Hobart and William Smith Colleges, Geneva, NY, USA
| | - Dominique Alfandari
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA, USA
| | - Francesca Pignoni
- Department of Ophthalmology, Upstate Medical University, Syracuse, NY, USA
| |
Collapse
|
8
|
Do Green Treefrogs (Hyla cinerea) Eavesdrop on Prey Calls? J HERPETOL 2014. [DOI: 10.1670/13-032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
9
|
Moreno-Gómez FN, Sueur J, Soto-Gamboa M, Penna M. Female frog auditory sensitivity, male calls, and background noise: potential influences on the evolution of a peculiar matched filter. Biol J Linn Soc Lond 2013. [DOI: 10.1111/bij.12156] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Felipe N. Moreno-Gómez
- Instituto de Ciencias Ambientales y Evolutivas; Facultad de Ciencias; Universidad Austral de Chile; Avenida Rector Eduardo Morales Miranda, Edificio Pugín, Casilla(Box) 567 Valdivia Chile
| | - Jérôme Sueur
- Département Systématique et Evolution; Muséum National d'Histoire naturelle; UMR CNRS 7205 OSEB, 45 rue Buffon F-75005 Paris France
| | - Mauricio Soto-Gamboa
- Instituto de Ciencias Ambientales y Evolutivas; Facultad de Ciencias; Universidad Austral de Chile; Avenida Rector Eduardo Morales Miranda, Edificio Pugín, Casilla(Box) 567 Valdivia Chile
| | - Mario Penna
- Programa de Fisiología y Biofísica; Instituto de Ciencias Biomédicas; Facultad de Medicina; Universidad de Chile; Casilla 70005, Correo 7 Santiago Chile
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Manley GA, Narins PM, Fay RR. Experiments in comparative hearing: Georg von Békésy and beyond. Hear Res 2012; 293:44-50. [PMID: 22560960 DOI: 10.1016/j.heares.2012.04.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Revised: 04/16/2012] [Accepted: 04/17/2012] [Indexed: 11/17/2022]
Abstract
Georg von Békésy was one of the first comparative auditory researchers. He not only studied basilar membrane (BM) movements in a range of mammals of widely different sizes, he also worked on the chicken basilar papilla and the frog middle ear. We show that, in mammals, at least, his data do not differ from those that could be collected using modern techniques but with the same, very loud sounds. There is in all cases a major difference to frequency maps collected using low-level sounds. In contrast, the same cannot be said of his chicken data, perhaps due to the different roles played by the BM in mammals and birds. In lizards, the BM is not tuned and it is perhaps good that Békésy did not begin with those species and get discouraged in his seminal comparative work.
Collapse
Affiliation(s)
- Geoffrey A Manley
- Cochlear and Auditory Brainstem Physiology, IBU, Faculty V, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Strasse 9-11, 26129 Oldenburg, Germany.
| | | | | |
Collapse
|
12
|
Schoffelen RLM, Segenhout JM, van Dijk P. Input-output characteristics of the tectorial membrane in the frog basilar papilla. Hear Res 2010; 268:75-84. [PMID: 20457241 DOI: 10.1016/j.heares.2010.04.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2009] [Revised: 04/27/2010] [Accepted: 04/30/2010] [Indexed: 10/19/2022]
Abstract
The basilar papilla (BP) in the frog inner ear is a relatively simple auditory receptor. Its hair cells are embedded in a stiff support structure, with the stereovilli connecting to a flexible tectorial membrane (TM). Acoustic energy passing the papilla presumably causes displacement of the TM, which in turn deflects the stereovilli and stimulates the hair cells. In this paper we present optical measurements of the mechanical response of the TM to various stimulus levels. Results were obtained from 3 specimens (4 ears). The phase of the displaced area of the TM was constant across stimulus levels. Phase differences between the orthogonal spatial motion components were either close to 0 degrees or 180 degrees. These findings were consistent with a TM motion along the epithelium surface. The TM response was linear for stimulus levels up to -30 dB (re. 1 microm) at the operculum. This amplitude was estimated to exceed that at which neural responses saturate. Apparently, saturation of the neural response in the frog inner ear is not based on saturation of the mechanical response of the tectorial membrane.
Collapse
Affiliation(s)
- Richard L M Schoffelen
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, The Netherlands
| | | | | |
Collapse
|
13
|
Somatic motility and hair bundle mechanics, are both necessary for cochlear amplification? Hear Res 2010; 273:109-22. [PMID: 20430075 DOI: 10.1016/j.heares.2010.03.094] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 03/02/2010] [Accepted: 03/08/2010] [Indexed: 11/22/2022]
Abstract
Hearing organs have evolved to detect sounds across several orders of magnitude of both intensity and frequency. Detection limits are at the atomic level despite the energy associated with sound being limited thermodynamically. Several mechanisms have evolved to account for the remarkable frequency selectivity, dynamic range, and sensitivity of these various hearing organs, together termed the active process or cochlear amplifier. Similarities between hearing organs of disparate species provides insight into the factors driving the development of the cochlear amplifier. These properties include: a tonotopic map, the emergence of a two hair cell system, the separation of efferent and afferent innervations, the role of the tectorial membrane, and the shift from intrinsic tuning and amplification to a more end organ driven process. Two major contributors to the active process are hair bundle mechanics and outer hair cell electromotility, the former present in all hair cell organs tested, the latter only present in mammalian cochlear outer hair cells. Both of these processes have advantages and disadvantages, and how these processes interact to generate the active process in the mammalian system is highly disputed. A hypothesis is put forth suggesting that hair bundle mechanics provides amplification and filtering in most hair cells, while in mammalian cochlea, outer hair cell motility provides the amplification on a cycle by cycle basis driven by the hair bundle that provides frequency selectivity (in concert with the tectorial membrane) and compressive nonlinearity. Separating components of the active process may provide additional sites for regulation of this process.
Collapse
|
14
|
Van Dijk P, Mason MJ, Schoffelen RLM, Narins PM, Meenderink SWF. Mechanics of the frog ear. Hear Res 2010; 273:46-58. [PMID: 20149854 DOI: 10.1016/j.heares.2010.02.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 02/01/2010] [Accepted: 02/03/2010] [Indexed: 11/18/2022]
Abstract
The frog inner ear contains three regions that are sensitive to airborne sound and which are functionally distinct. (1) The responses of nerve fibres innervating the low-frequency, rostral part of the amphibian papilla (AP) are complex. Electrical tuning of hair cells presumably contributes to the frequency selectivity of these responses. (2) The caudal part of the AP covers the mid-frequency portion of the frog's auditory range. It shares the ability to generate both evoked and spontaneous otoacoustic emissions with the mammalian cochlea and other vertebrate ears. (3) The basilar papilla functions mainly as a single auditory filter. Its simple anatomy and function provide a model system for testing hypotheses concerning emission generation. Group delays of stimulus-frequency otoacoustic emissions (SFOAEs) from the basilar papilla are accounted for by assuming that they result from forward and reverse transmission through the middle ear, a mechanical delay due to tectorial membrane filtering and a rapid forward and reverse propagation through the inner ear fluids, with negligible delay.
Collapse
Affiliation(s)
- Pim Van Dijk
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, The Netherlands.
| | | | | | | | | |
Collapse
|
15
|
Multiple roles for the tectorial membrane in the active cochlea. Hear Res 2009; 266:26-35. [PMID: 19853029 DOI: 10.1016/j.heares.2009.10.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 10/12/2009] [Accepted: 10/13/2009] [Indexed: 11/28/2022]
Abstract
This review is concerned with experimental results that reveal multiple roles for the tectorial membrane in active signal processing in the mammalian cochlea. We discuss the dynamic mechanical properties of the tectorial membrane as a mechanical system with several degrees of freedom and how its different modes of movement can lead to hair-cell excitation. The role of the tectorial membrane in distributing energy along the cochlear partition and how it channels this energy to the inner hair cells is described.
Collapse
|
16
|
Tuning of the tectorial membrane in the basilar papilla of the northern leopard frog. J Assoc Res Otolaryngol 2009; 10:309-20. [PMID: 19488819 PMCID: PMC2717376 DOI: 10.1007/s10162-009-0167-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Accepted: 03/09/2009] [Indexed: 11/29/2022] Open
Abstract
The basilar papilla (BP) in the frog inner ear is a relatively simple auditory receptor. Its hair cells are embedded in a stiff support structure, with the stereovilli connecting to a flexible tectorial membrane (TM). Acoustic energy passing the papilla presumably causes displacement of the TM, which in turn deflects the stereovilli and stimulates the hair cells. Auditory neurons that contact the BP’s hair cells are known to have nearly identical characteristic frequencies and frequency selectivity. In this paper, we present optical measurements of the mechanical response of the TM. Results were obtained from five specimens. The TM displacement was essentially in phase across the membrane, with the largest amplitudes occurring near the hair cells. The response was tuned to a frequency near 2 kHz. The phase accumulated over at least 270° across the measured frequencies. The tuning quality Q10dB values were calculated; the average Q10dB was 2.0 ± 0.8 (standard deviation). Our results are comparable to those of neural-tuning curves in the same and a similar species. Also, they are in agreement with the response of an associated structure—the contact membrane—in a closely related species. Our data provides evidence for a mechanical basis for the frequency selectivity of the frog’s BP.
Collapse
|