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Iwasa KH. Of mice and chickens: Revisiting the RC time constant problem. Hear Res 2021; 423:108422. [PMID: 34965897 DOI: 10.1016/j.heares.2021.108422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Revised: 12/09/2021] [Accepted: 12/15/2021] [Indexed: 11/30/2022]
Abstract
Avian hair cells depend on electrical resonance for frequency selectivity. The upper bound of the frequency range is limited by the RC time constant of hair cells because the sharpness of tuning requires that the resonance frequency must be lower than the RC roll-off frequency. In contrast, tuned mechanical vibration of the inner ear is the basis of frequency selectivity of the mammalian ear. This mechanical vibration is supported by outer hair cells (OHC) with their electromotility (or piezoelectricity), which is driven by the receptor potential. Thus, it is also subjected to the RC time constant problem. Association of OHCs with a system with mechanical resonance leads to piezoelectric resonance. This resonance can nullify the membrane capacitance and solves the RC time constant problem for OHCs. Therefore, avian and mammalian ears solve the same problem in the opposite way.
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Affiliation(s)
- Kuni H Iwasa
- NIDCD, National Institutes of Health, Bethesda, MD 20892, USA.
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Caus Capdevila MQ, Sienknecht UJ, Köppl C. Developmental maturation of presynaptic ribbon numbers in chicken basilar-papilla hair cells and its perturbation by long-term overexpression of Wnt9a. Dev Neurobiol 2021; 81:817-832. [PMID: 34309221 DOI: 10.1002/dneu.22845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/20/2021] [Accepted: 07/15/2021] [Indexed: 11/07/2022]
Abstract
The avian basilar papilla is a valuable model system for exploring the developmental determination and differentiation of sensory hair cells and their innervation. In the mature basilar papilla, hair cells form a well-known continuum between two extreme types-tall and short hair cells-that differ strikingly in their innervation. Previous work identified Wnt9a as a crucial factor in this differentiation. Here, we quantified the number and volume of immunolabelled presynaptic ribbons in tall and short hair cells of chickens, from developmental stages shortly after ribbons first appear to the mature posthatching condition. Two longitudinal locations were sampled, responding to best frequencies of approximately 1 kHz and approximately 5.5 kHz when mature. We found significant reductions of ribbon number during normal development in the tall-hair-cell domains, but stable, low numbers in the short-hair-cell domains. Exposing developing hair cells to continuous, excessive Wnt9a levels (through virus-mediated overexpression) led to transiently abnormal high numbers of ribbons and a delayed reduction of ribbon numbers at all sampled locations. Thus, (normally) short-hair-cell domains also showed tall-hair-cell like behaviour, confirming previous findings (Munnamalai et al., 2017). However, at 3 weeks posthatching, ribbon numbers had decreased to the location-specific typical values of control hair cells at all sampled locations. Furthermore, as shown previously, mature hair cells at the basal, high-frequency location harboured larger ribbons than more apically located hair cells. This was true for both normal and Wnt9a-overexposed basilar papillae.
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Affiliation(s)
- M Queralt Caus Capdevila
- Cluster of Excellence "Hearing4all" and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Ulrike J Sienknecht
- Cluster of Excellence "Hearing4all" and Research Centre Neurosensory Science, Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - 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, Oldenburg, Germany
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Manley GA. Travelling waves and tonotopicity in the inner ear: a historical and comparative perspective. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2018; 204:773-781. [PMID: 30116889 DOI: 10.1007/s00359-018-1279-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 07/10/2018] [Accepted: 07/11/2018] [Indexed: 12/22/2022]
Abstract
In the 1940s, Georg von Békésy discovered that in the inner ear of cadavers of various vertebrates, structures responded to sound with a displacement wave that travels in a basal-to-apical direction. This historical review examines this concept and sketches its rôle and significance in the development of the research field of cochlear mechanics. It also illustrates that this concept and that of tonotopicity necessarily correlate, in that travelling waves are consequences of the existence of an ordered, longitudinal array of receptor cells tuned to systematically changing frequencies along the auditory organ.
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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.
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Corfield JR, Krilow JM, Vande Ligt MN, Iwaniuk AN. A quantitative morphological analysis of the inner ear of galliform birds. Hear Res 2013; 304:111-27. [DOI: 10.1016/j.heares.2013.07.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 06/12/2013] [Accepted: 07/06/2013] [Indexed: 11/30/2022]
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Origin and Development of Hair Cell Orientation in the Inner Ear. INSIGHTS FROM COMPARATIVE HEARING RESEARCH 2013. [DOI: 10.1007/2506_2013_28] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Corfield JR, Kubke MF, Parsons S, Köppl C. Inner-ear morphology of the New Zealand kiwi (Apteryx mantelli) suggests high-frequency specialization. J Assoc Res Otolaryngol 2012; 13:629-39. [PMID: 22772440 DOI: 10.1007/s10162-012-0341-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/20/2012] [Indexed: 11/29/2022] Open
Abstract
The sensory systems of the New Zealand kiwi appear to be uniquely adapted to occupy a nocturnal ground-dwelling niche. In addition to well-developed tactile and olfactory systems, the auditory system shows specializations of the ear, which are maintained along the central nervous system. Here, we provide a detailed description of the auditory nerve, hair cells, and stereovillar bundle orientation of the hair cells in the North Island brown kiwi. The auditory nerve of the kiwi contained about 8,000 fibers. Using the number of hair cells and innervating nerve fibers to calculate a ratio of average innervation density showed that the afferent innervation ratio in kiwi was denser than in most other birds examined. The average diameters of cochlear afferent axons in kiwi showed the typical gradient across the tonotopic axis. The kiwi basilar papilla showed a clear differentiation of tall and short hair cells. The proportion of short hair cells was higher than in the emu and likely reflects a bias towards higher frequencies represented on the kiwi basilar papilla. The orientation of the stereovillar bundles in the kiwi basilar papilla showed a pattern similar to that in most other birds but was most similar to that of the emu. Overall, many features of the auditory nerve, hair cells, and stereovilli bundle orientation in the kiwi are typical of most birds examined. Some features of the kiwi auditory system do, however, support a high-frequency specialization, specifically the innervation density and generally small size of hair-cell somata, whereas others showed the presumed ancestral condition similar to that found in the emu.
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Affiliation(s)
- Jeremy R Corfield
- Department of Anatomy with Radiology, University of Auckland, Auckland, New Zealand.
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Corfield J, Kubke MF, Parsons S, Wild JM, Köppl C. Evidence for an auditory fovea in the New Zealand kiwi (Apteryx mantelli). PLoS One 2011; 6:e23771. [PMID: 21887317 PMCID: PMC3161079 DOI: 10.1371/journal.pone.0023771] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Accepted: 07/25/2011] [Indexed: 11/18/2022] Open
Abstract
Kiwi are rare and strictly protected birds of iconic status in New Zealand. Yet, perhaps due to their unusual, nocturnal lifestyle, surprisingly little is known about their behaviour or physiology. In the present study, we exploited known correlations between morphology and physiology in the avian inner ear and brainstem to predict the frequency range of best hearing in the North Island brown kiwi. The mechanosensitive hair bundles of the sensory hair cells in the basilar papilla showed the typical change from tall bundles with few stereovilli to short bundles with many stereovilli along the apical-to-basal tonotopic axis. In contrast to most birds, however, the change was considerably less in the basal half of the epithelium. Dendritic lengths in the brainstem nucleus laminaris also showed the typical change along the tonotopic axis. However, as in the basilar papilla, the change was much less pronounced in the presumed high-frequency regions. Together, these morphological data suggest a fovea-like overrepresentation of a narrow high-frequency band in kiwi. Based on known correlations of hair-cell microanatomy and physiological responses in other birds, a specific prediction for the frequency representation along the basilar papilla of the kiwi was derived. The predicted overrepresentation of approximately 4-6 kHz matches potentially salient frequency bands of kiwi vocalisations and may thus be an adaptation to a nocturnal lifestyle in which auditory communication plays a dominant role.
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Affiliation(s)
- Jeremy Corfield
- Department of Anatomy with Radiology, University of Auckland, Auckland, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - M. Fabiana Kubke
- Department of Anatomy with Radiology, University of Auckland, Auckland, New Zealand
| | - Stuart Parsons
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - J. Martin Wild
- Department of Anatomy with Radiology, University of Auckland, Auckland, New Zealand
| | - Christine Köppl
- Institute for Biology and Environmental Sciences, and Research Center Neurosensory Science, Carl von Ossietzky University, Oldenburg, Germany
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Vergne AL, Pritz MB, Mathevon N. Acoustic communication in crocodilians: from behaviour to brain. Biol Rev Camb Philos Soc 2009; 84:391-411. [PMID: 19659884 DOI: 10.1111/j.1469-185x.2009.00079.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Crocodilians and birds are the modern representatives of Phylum Archosauria. Although there have been recent advances in our understanding of the phylogeny and ecology of ancient archosaurs like dinosaurs, it still remains a challenge to obtain reliable information about their behaviour. The comparative study of birds and crocodiles represents one approach to this interesting problem. One of their shared behavioural features is the use of acoustic communication, especially in the context of parental care. Although considerable data are available for birds, information concerning crocodilians is limited. The aim of this review is to summarize current knowledge about acoustic communication in crocodilians, from sound production to hearing processes, and to stimulate research in this field. Juvenile crocodilians utter a variety of communication sounds that can be classified into various functional categories: (1) "hatching calls", solicit the parents at hatching and fine-tune hatching synchrony among siblings; (2) "contact calls", thought to maintain cohesion among juveniles; (3) "distress calls", induce parental protection; and (4) "threat and disturbance calls", which perhaps function in defence. Adult calls can likewise be classified as follows: (1) "bellows", emitted by both sexes and believed to function during courtship and territorial defence; (2) "maternal growls", might maintain cohesion among offspring; and (3) "hisses", may function in defence. However, further experiments are needed to identify the role of each call more accurately as well as systematic studies concerning the acoustic structure of vocalizations. The mechanism of sound production and its control are also poorly understood. No specialized vocal apparatus has been described in detail and the motor neural circuitry remains to be elucidated. The hearing capabilities of crocodilians appear to be adapted to sound detection in both air and water. The ear functional anatomy and the auditory sensitivity of these reptiles are similar in many respects to those of birds. The crocodilian nervous system likewise shares many features with that of birds, especially regarding the neuroanatomy of the auditory pathways. However, the functional anatomy of the telencephalic auditory areas is less well understood in crocodilians compared to birds.
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Affiliation(s)
- A L Vergne
- Université de Saint-Etienne, Ecologie & Neuro-Ethologie Sensorielles EA3988, Saint-Etienne, France.
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Ramcharitar JU, Higgs DM, Popper AN. Audition in sciaenid fishes with different swim bladder-inner ear configurations. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2006; 119:439-43. [PMID: 16454298 DOI: 10.1121/1.2139068] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We investigated how morphological differences in the auditory periphery of teleost fishes may relate to hearing capabilities. Two species of western Atlantic sciaenids were examined: weakfish (Cynoscion regalis, Block and Schneider) and spot (Leiostomus xanthurus, Lacepede). These species differ in the anatomical relationship between the swim bladder and the inner ear. In weakfish, the swim bladder has a pair of anterior horns that terminate close to the ear, while there are no extensions of the swim bladder in spot. Thus, the swim bladder in spot terminates at a greater distance from the ear when compared to weakfish. With the use of the auditory brainstem response technique, Cynoscion regalis were found to detect frequencies up to 2000 Hz, while Leiostomus xanthurus detected up to 700 Hz. There were, however, no significant interspecific differences in auditory sensitivity for stimuli between 200 and 700 Hz. These data support the hypothesis that the swim bladder can potentially expand the frequency range of detection.
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Affiliation(s)
- John U Ramcharitar
- Department of Biology & Neuroscience and Cognitive Science Program, University of Maryland, College Park, Maryland 20742, USA.
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Gleich O, Fischer FP, Köppl C, Manley GA. Hearing Organ Evolution and Specialization: Archosaurs. EVOLUTION OF THE VERTEBRATE AUDITORY SYSTEM 2004. [DOI: 10.1007/978-1-4419-8957-4_8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Hossler FE, Olson KR, Musil G, McKamey MI. Ultrastructure and blood supply of the tegmentum vasculosum in the cochlea of the duckling. Hear Res 2002; 164:155-65. [PMID: 11950535 DOI: 10.1016/s0378-5955(01)00427-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The tegmentum vasculosum of the duckling consists of a highly folded epithelium which extends over the dorsal and lateral walls of the cochlear duct, separating the scala media from the scala vestibuli. This epithelium consists of two distinct cell types, dark cells and light cells, and is well vascularized. The surface of the epithelium is formed by a mosaic of alternating dark and light cells. The goblet-shaped dark cells have an electron-dense, organelle-rich cytoplasm, and are expanded basally by extensive basolateral plasma membrane infoldings, within which are numerous mitochondria. Dark cells are isolated from each other and from the capillaries within the epithelium by intervening light cells. In contrast, columnar light cells exhibit an electron-lucent, organelle-poor cytoplasm and may extend from the underlying capillaries to the endolymphatic surface. Light cells contain abundant, coated endocytic vesicles on their apical surfaces and are bound, apically, to other light cells or to dark cells by tight junctions and desmosomes. Laterally, light cells are linked to each other either by complex, fluid-filled membrane interdigitations or by extensive gap junctions. Plasma membrane interdigitations and obvious, fluid-filled intercellular spaces characterize the lateral borders between light and dark cells. Vascular corrosion casting reveals the three-dimensional anatomy of the cochlear vasculature. A continuous arteriolar loop fed by anterior and posterior cochlear arterioles encircles the cochlear duct. The rich capillary beds of the tegmentum vasculosum are supplied by arching arterioles arising from this loop. These capillaries are the continuous type and are situated primarily within the core of the epithelium or along its border with the scala vestibuli. The structure and blood supply of the tegmentum vasculosum are characteristic of an epithelium involved in active transport.
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Affiliation(s)
- Fred E Hossler
- Department of Anatomy and Cell Biology, J.H. Quillen College of Medicine, Box 70582, East Tennessee State University, Johnson City 37614, USA.
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Abstract
The sensory hair cells of the inner ear receive both afferent and efferent innervation. The efferent supply to the auditory organ has evolved in birds and mammals into a separate complex system, with several types of neurons of largely unknown function. In this study, the efferent axons in four different species of birds (chicken, starling, barn owl and emu) were examined anatomically. Total numbers of efferents supplying the cochlear duct (auditory basilar papilla and the vestibular lagenar macula) were determined; separate estimates of the efferents to the lagenar macula only were also derived and subtracted. The numbers for auditory efferents thus varied between 120 (chicken) and 1068 (barn owl). Considering the much larger numbers of hair cells in the basilar papilla, each efferent is predicted to branch extensively. However, pronounced species-specific differences as well as regional differences along the tonotopic gradient of the basilar papilla were documented. Myelinated and unmyelinated axons were found, with mean diameters of about 1 microm and about 0.5 microm, respectively. This suggests two basic populations of efferents, however, they did not appear to be distinguished sharply. Evidence is presented that some efferents lose their myelination at the transition from central oligodendrocyte to peripheral Schwann cell myelin. Finally, a comparison of the four bird species evaluated suggests that the efferent population with smaller, unmyelinated axons is the phylogenetically more primitive one. A new population probably arose in parallel with the evolution and differentiation of the specialized hair-cell type it innervates, the short hair cell.
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Affiliation(s)
- C Köppl
- Zoologie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
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Abstract
Over the past year, much progress has been achieved in the study of both the peripheral and the central auditory systems of birds. Significant advances have been made in the study of hair cells, including elucidation of the mechanisms of selectivity for sound frequency, functional differentiation, efferent innervation, and regeneration. Most of the studies of central auditory neurones have concerned the developmental and physiological correlates of vocal learning in songbirds and sound localisation in owls.
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Affiliation(s)
- C Köppl
- Institut für Zoologie, Technische Universität München, Garching, Germany.
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Yates GK, Manley GA, Köppl C. Rate-intensity functions in the emu auditory nerve. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2000; 107:2143-2154. [PMID: 10790040 DOI: 10.1121/1.428496] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Rate-versus-intensity functions recorded from mammalian auditory-nerve fibers have been shown to form a continuum of shapes, ranging from saturating to straight and correlating well with spontaneous rate and sensitivity. These variations are believed to be a consequence of the interaction between the sensitivity of the hair-cell afferent synapse and the nonlinear, compressive growth of the cochlear amplifier that enhances mechanical vibrations on the basilar membrane. Little is known, however, about the cochlear amplifier in other vertebrate species. Rate-intensity functions were recorded from auditory-nerve fibers in chicks of the emu, a member of the Ratites, a primitive group of flightless birds that have poorly differentiated short and tall hair cells. Recorded data were found to be well fitted by analytical functions which have previously been shown to represent well the shapes of rate-intensity functions in guinea pigs. At the fibers' most sensitive frequencies, rate-intensity functions were almost exclusively of the sloping (80.9%) or straight (18.6%) type. Flat-saturating functions, the most common type in the mammal, represented only about 0.5% of the total in the emu. Below the best frequency of each fiber, the rate-intensity functions tended more towards the flat-saturating type, as is the case in mammals; a similar but weaker trend was seen above best frequency in most fibers, with only a small proportion (18%) showing the reverse trend. The emu rate-intensity functions were accepted as supporting previous evidence for the existence of a cochlear amplifier in birds, the conclusion was drawn further that the nonlinearity observed is probably due to saturation of the hair-cell transduction mechanism.
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Affiliation(s)
- G K Yates
- Department of Physiology, The University of Western Australia, Nedlands. Australia.
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Abstract
This paper is a comparative study of auditory-nerve morphology in birds. The chicken (Gallus gallus), the emu (Dromaius novaehollandiae) and the starling (Sturnus vulgaris) were chosen as unspecialised birds that have already been used in auditory research. The data are discussed in comparison to a similar earlier study on the barn owl, a bird with highly specialised hearing, in an attempt to separate general avian patterns from species specialisations. Average numbers of afferent fibres from 8775 (starling) to 12¿ omitted¿406 (chicken) were counted, excluding fibres to the lagenar macula. The number of fibres representing different frequency ranges showed broad maxima in the chicken and emu, corresponding to hearing ranges of best sensitivity and/or particular behavioural relevance. Mean axon diameters were around 2 microm in the chicken and starling, and around 3 microm in the emu. Virtually all auditory afferents were myelinated. The mean thickness of the myelin sheaths was between 0.33 microm (starling) and 0.4 microm (emu). There was a consistent pattern in the diameters of axons deriving from different regions. Axons from very basal, i.e. highest-frequency, parts of the basilar papilla were always the smallest. In the emu and the chicken, axons from the middle papillar regions were, in addition, larger than axons innervating apical regions.
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Affiliation(s)
- C Köppl
- Institut für Zoologie, Technische Universität München, Lichtenbergstrasse 4, 85747, Garching, Germany.
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