Geoffrey Manley

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• M.A., Ph.D.
• Guest Scientist at Carl von Ossietzky University of Oldenburg

Comparative auditory studies make it possible both to understand the origins of modern ears and the factors underlying the similarities and differences in their performance. After all lineages of land vertebrates had independently evolved tympanic middle ears in the early Mesozoic era, the subsequent tens of millions of years led to the hearing org...

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 s...

Significance Healthy ears not only detect sound but can emit it as well. These sounds can occur either spontaneously and continuously or in response to acoustic stimulation. Evoked emissions are increasingly used as clinical diagnostic tools. The mechanisms underlying their generation, however, are incompletely understood. In particular, otoacousti...

Evolution of the cochlea and high-frequency hearing (>20 kHz; ultrasonic to humans) in mammals has been a subject of research for many years. Recent advances in paleontological techniques, especially the use of micro-CT scans, now provide important new insights that are here reviewed. True mammals arose more than 200 million years (Ma) ago. Of thes...

The hearing organ of the inner ear was the last of the paired sense organs of amniotes to undergo formative evolution. As a mechanical sensory organ, the inner-ear hearing organ's function depends highly on its physical structure. Comparative studies suggest that the hearing organ of the earliest amniote vertebrates was small and simple, but posses...

Synopsis of “Ears wide open” Hearing is one of our most vital senses. Our sensitive ears provide us with crucial information that keeps us safe, enables us to communicate, and allows us to enjoy beautiful music. Modern civilization, however, generates so much noise that, without deliberate care, we gradually lose our ability to hear clearly and und...

This is a commentary on a previous article (Bidelmann et al 2016) that claimed that musical experience improved the frequency resolution of the human cochlea.

We used a variety of species exhibiting disparate inner ear morphologies: human, barn owl, and (Anolis) lizards. To varying degrees across all three groups, spontaneous emission peaks exhibit intra- (IrP) and interpeak (IPP) correlations indicative of interaction between generative elements. Activity from anole lizards, whose auditory sensoryorgan...

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 w...

African mole-rats display highly derived hearing that is characterized by low sensitivity and a narrow auditory range restricted to low frequencies < 10 kHz. Recently, it has been suggested that two species of these rodents do not exhibit distortion product otoacoustic emissions (DPOAE), which was interpreted as evidence for a lack of cochlear ampl...

Although many early anatomical papers touched on lizard ears, the absence of accurate tools severely limited progress. After 1950, new techniques permitted detailed anatomical descriptions and revealed the remarkable variations between the auditory papillae of different lizard families and a recognition of their usefulness of the variations for sys...

The independent origins of middle ears in testudinates, lepidosaurs, and archosaurs in the Triassic led to lineage-specific developments in their auditory epithelia. In comparison to the inferred ancestral state, little changed in testudinates, but archosaurs and most lepidosaurs evolved longer, differentiated auditory papillae. In archosaurs, sens...

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 i...

A general overview of the function of the mammalian inner ear

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.

Synopsis The evolutionary origins of the modern mammalian ear structures can be traced back into their phylogenetic predecessors in the Mesozoic Era. This evolutionary history shows a step-wise acquisition of middle- and inner-ear structures along separate Mesozoic mammal lineages that led to convergence of several derived characters correlated wit...

Synopsis The huge structural variety in lepidosaurs ears is unique and results in substantial functional differences. The simple epithelia of snakes are restricted to low frequencies. Each lizard family has a characteristic hearing organ structure, with the largest variety in the number of hair cells and the type of tectorial membrane. Whereas the...

Preamble: Some new attempts to understand the evolution of the ear of mammals are based on assuming the dominance of physics, even going so far as to assume that "nonlinear physics led to the unique design of the cochlea observed in mammals" (e.g., Lorimer et al. 2015). In our comments on this paper, my colleagues and I (Manley et al. 2016) show th...

As they are generally small and only hear low frequencies, lizards have few cues for localizing sound. However, their ears show extreme directionality (up to 30 dB direction-dependent difference in eardrum vibrations) created by strong acoustical coupling of the eardrums, with almost perfect internal transmission from the contralateral ear over a b...

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...

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 osci...

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...

This review summarizes paleontological data aswell as studies on the morphology, function, and molecular evolution of the cochlea of living mammals (monotremes, marsupials, and placentals). The most parsimonious scenario is an early evolution of the characteristic organ of Corti, with inner and outer hair cells and nascent electromotility. Most rem...

This review summarizes paleontological data as well as studies on the morphology, function, and molecular evolution of the cochlea of living mammals (monotremes, marsupials, and placentals). The most parsimonious scenario is an early evolution of the characteristic organ of Corti, with inner and outer hair cells and nascent electromotility. Most re...

It has become common in the paleontological literature to assume that the presence of secondary bony laminae in the cochleae of early mammals indicates that these species were able to perceive high sound frequencies (>20 kHz). This review examines the validity of this idea in the context of comparative physiological data from extant amniotes and su...

Spontaneous otoacoustic emissions (SOAE) can be suppressed by presenting an acoustical stimulus. For stimuli with frequencies close to the SOAE frequency, the SOAE either show a beating pattern or are heavily suppressed while the spectral energy of the stimulus increases. This effect indicates that the self-sustained oscillations in the cochlea und...

Hearing organs, being sound detectors, must obey the general laws of physics. In this sense, physics imposes limits for evolution but does not direct it as such or necessarily leads to the selection of one “optimum design.” Vertebrate hearing organs arose from preexisting vestibular sensory epithelia that, over hundreds of millions of years, were s...

SOAE from the last major lizard family not yet investigated, the teiids, were collected from the genera Callopistes, Tupinambis and Cnemidophorus. Although their papillae show characteristics of the family Teiidae, the papillae differ both in their size and in the arrangement of uni- and bi-directional hair-cell areas. Among these three genera, Cal...

This SHAR volume serves to expand, supplement, and update the original "Cochlea" volume in the series. The book aims to highlight the power of diverse modern approaches in cochlear research by focusing on advances in those fields over the last two decades. It also provides insights into where cochlear research is going, including new hearing prosth...

The exquisite spectral and temporal properties of the cochlea are achieved by functional integration of specialized subsystems. Being highly integrated, in vivo these components had remained technically inaccessible for fundamental research and clinical diagnosis without damaging the whole system. In the last three decades, however, great steps for...

The snail-shell shaped hearing organ of therian mammals is a unique development among vertebrate animals, and even egg-laying mammals (monotremes) do not have this specialization. Although there have been several ideas concerning ways in which the peculiar shape of the modern cochlea might positively affect certain aspects of its function, as yet n...

The last several decades of research have seen a burgeoning of data on the morphology, physiology, and evolutionary history of vertebrate auditory organs. This chapter briefly describes the status of our understanding of ear structure and function and their origins in fish, which hear using their vestibular epithelia, and land vertebrates that earl...

Free access until Sept. 19th 2017 under: https://authors.elsevier.com/a/1VTfL1M5IZGqzx The hearing organs of amniote vertebrates show large differences in their size and structure between the species’ groups. In spite of this, their performance in terms of hearing sensitivity and the frequency selectivity of auditory-nerve units shows unexpectedly...

In humans, a similar spectral periodicity is found in all otoacoustic emission types and in threshold fine structure. This may reflect travelling wave phase and reflectance from “structural roughness” in the organ of Corti, or entrainment and suppressive interactions between emissions. To further understand these phenomena, we have examined spontan...

Abstract. In humans, a similar spectral periodicity is found in all otoacoustic emission types and in threshold fine structure. This may reflect travelling wave phase and reflectance from “structural roughness” in the organ of Corti, or entrainment and suppressive interactions between emissions. To further understand these phenomena, we have examin...

The form and function of the ears of modern land vertebrates cannot be understood without knowing how they evolved.

Experienced homing pigeons with extirpated cochleae and lagenae were released from six sites in upstate New York and western Pennsylvania on 17 days between 1973 and 1975 by William T. Keeton and his co-workers at Cornell University. The previously unpublished data indicate that departure directions of the operated birds were significantly differen...

Significant debate still exists about the biophysical mechanisms at work in otoacoustic emission (OAE) generation and how such may differ between mammals and non-mammals given gross morphological differences (e.g., existence of basilar membrane traveling waves, degree of tectorial membrane coupling). To further elucidate general principles at work,...

1. Evolutionary processes acted in parallel on the various lineages of amniotes and produced sensitive, frequency selective auditory papillae in all groups. Over the eons, selective pressures induced convergent and parallel effects, such as the evolution of specialized hair cell populations in concert with the utilization of active processes (Manle...

Research over the last decade has added hugely to our understanding of gecko ears. Their papillae are unique both in their general anatomy (patterns of hair -cell orientations) as well as their detailed anatomy (specific coupling of single hair -cell rows via sallets). The correlations of their anatomy to specific aspects of their auditory physiolo...

For almost a century, scientists have been aware of the great variety of structures subserving the function of hearing in animals. Only rather recently, however, has good evidence become available that the basic units of hearing, the hair cells, are not only common to all vertebrates, but share a common ancestry in apparently unrelated organisms su...

An important element in the ear of recent tetrapods, the land-living vertebrates, is the middle ear. The evolution of the middle ear – tympanic membrane and middle ear bone(s) - often described as an essential player in audition, enabled the tetrapods to respond to airborne sound by matching the acoustic impedance of the ear to the impedance of air...

The middle ear of tetrapods (limbed vertebrates) originated from nonauditory structures, and has been modified by adaptations arising from the lifestyle of the tetrapods. These accessory structures for the inner ear increased the sensitivity to airborne sound, the frequency range of hearing, and the directionality of the ear. The tympanic middle ea...

The classical mammalian auditory periphery, i.e., the type of middle ear and coiled cochlea seen in modern therian mammals, did not arise as one unit and did not arise in all mammals. It is also not the only kind of auditory periphery seen in modern mammals. This short review discusses the fact that the constituents of modern mammalian auditory per...

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...

All amniote vertebrates of the Mesozoic era inherited a small, low-frequency (upper limit estimated at ~1 kHz) hearing organ from their Paleozoic ancestors. Mammals and non-mammals evolved tympanic middle ears independently of each other during late Triassic times. In mammals, this event occurred at least three times. Following these events, all gr...

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 fro...

In their letter to the editor (Freeman and Hare 2011), Freeman and Hare suggest that the technical procedures used in our study of infrasound responses in the Capercaillie (Tetrao urogallus) were improper—and at least inadequate—to answer the questions posed. We reject their

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...

Using the studies of fossils and modern animals, the evolution of the sensory system involved in hearing have been elucidated in great detail. The results trace the evolution of hearing back to our fish ancestors, through the establishment of a dedicated auditory epithelium and of independently-evolved, impedance-matching middle ears in amniotes. T...

A discussion moderated by the authors on the topics “Comparative Auditory Mechanics” and “Mechanics in the Apex of the Cochlea” was held on 20 July 2011 at the 11th International Mechanics of Hearing Workshop in Williamstown, Massachusetts. The paper provides an edited transcript of the session. ISBN 978-0-7354-0975-0

In their recent review, Mann and Kelley (2011) summarized evidence regarding the development of a tonotopic organization in the hearing organs of amniotes (mammals, archosaurs and lepidosaurs) with the aim of providing a systematic basis for molecularbiological studies. It is hoped that such molecular studies could help understand not only how such...

The variety of lizard auditory organs provides an optimal substrate for examining structure-function relationships. What does an auditory organ need to perform the basic tasks in the coding of acoustic stimuli? The single-ossicle tympanic middle ears of lizards are connected through the head, providing for sensitive directional hearing with little...

This special edition of Hearing Research is concerned with providing an update on aspects of comparative hearing. Narrowly defined, comparative hearing only covers hearing processes in non-mammalian organisms. 1. Studies in non-vertebrates: what is a hair cell? 2. Studies of fishes, amphibians, lizards and birds 3. Studies of mammals: specialized s...

This is a letter to the editor in response to a previous letter to the editor regarding one of my papers: (Manley, G.A. (2010) An evolutionary perspective on middle ears. Hearing Research 263, 3–8).

This paper is a critical comment on "Fusion as an evolutionary principle of the vertebrate labyrinth" by Richard R. Gacek.

We describe exceptional high-frequency hearing and vocalizations in a genus of pygopod lizards (Delma) that is endemic to Australia. Pygopods are a legless subfamily of geckos and share their highly specialized hearing organ. Hearing and vocalizations of amniote vertebrates were previously thought to differ clearly in their frequency ranges accordi...

The evolutionary processes that modified the structure and function of lizard auditory papillae during the separation of the familial lineages during the Jurassic have resulted in a remarkable variety of family-typical papillae. These papillae vary structurally in their size, in the patterns of the distribution of hair-cell types, in the presence o...

Molecular, morphological, and some physiological evidence suggest that vertebrate hair cells arose as one lineage that descended from mechanoreceptive cells that originated in the earliest animals with true tissues, the cnidarians. The ancestry of these cells can be traced into the different evolutionary lineages, for example, not only to the moder...

The traditional view that a tympanic middle ear developed only once, when vertebrates made the transition from fish in water to land-living animals, has been shown to be incorrect. Middle ears with a tympanum connected by one or more ossicles to the cochlea developed very much later in evolutionary history and independently in many amniote vertebra...

Lizard families can be grouped into larger units comprising those families that are closely related and whose auditory papillae are morphologically very similar. Based on the few species studied at that time [Manley, G.A., 1997. Diversity in hearing-organ structure and the characteristics of spontaneous otoacoustic emissions in lizards. In: Lewis,...

The center frequency, height and width of peaks in SOAE spectra depend on ear canal pressure. The width is interpreted as a measure of the inner ear source-signal-to-(e.g. thermal)-noise ratio. In humans, width increases with decreasing height. Apparently, ear canal pressure modifies the amplitude of the inner ear emission source signal. In lizards...

Inferences of hearing capabilities and audition-related behaviours in extinct reptiles and birds have previously been based on comparing cochlear duct dimensions with those of living species. However, the relationship between inner-ear bony anatomy and hearing ability or vocalization has never been tested rigorously in extant or fossil taxa. Here,...

Lizard ears are clear examples of two-input pressure-difference receivers, with up to 40-dB differences in eardrum vibration amplitude in response to ipsi- and contralateral stimulus directions. The directionality is created by acoustical coupling of the eardrums and interaction of the direct and indirect sound components on the eardrum. The ensuin...

The structure of the basilar papilla of the inner ear of lizards is the most diverse among all vertebrates. Research on a variety of lizard ears, animals that are remarkably robust under laboratory conditions, has provided the field of auditory research with valuable information, particularly on the minimum structural requirements for sensitive, se...

Sounds that are actually produced by healthy ears allow researchers and clinicians to study hearing and cochlear function noninvasively in both animals and humans. Active Processes and Otoacoustic Emissions in Hearing presents the first serious review of the biological basis of these otoacoustic emissions. Active processes, such as those in hair ce...

1. The Dust of History 2. Why Are Active Processes Necessary? 3. How Common are Active Processes in Mechanoreceptors? 4. How Do the Different Active Processes Interact in the Mammalian Cochlea? 5. What Is the Role of Hair-Cell Adaptation Motors? 6. What Is the Role of Rapid Channel Reclosure? 7. What Determines the Patterns of Spontaneous Otoacoust...

1. General Introduction Some of the earliest work on otoacoustic emissions (OAEs) was carried out on amphibians (Palmer and Wilson 1982), establishing right at the beginning of studies of this phenomenon that it is not exclusively the province of mammals. During the 1980s and 1990s, a good deal of work on frogs, lizards, and birds established the a...

Descartes, in the Treatise of Man (1662), suggested how nerve stimulation could evoke reflex responses. Descartes was aware of the principle of place coding for touch and for vision, and suggested how the stimulation of different nerves in the sensory input could lead to stimulation of different nerves in the motor output and so to different reflex...

The inner ear in the group of archosaurs (birds, crocodilians, and extinct dinosaurs) shows a high degree of structural similarity, enabling predictions of their function in extinct species based on relationships among similar variables in living birds. Behavioral audiograms and morphological data on the length of the auditory sensory epithelium (t...

This is a report on 15 years of auditory research within the Cooperative Research Center "Hearing" in Munich. The main text headings in this chapter are: "Anatomy of the cochlea in birds", "A special case of congenital hearing deficits: The Waterslager canary", "Micromechanical properties of chicken hair-cell bundles ", "Potassium concentration and...

auditory worlds;introduction

Shera [1] proposed that pressure effects on the middle ear provide a model for distinguishing between a point-source and a global standing-wave model of SOAE generation. A point source is supposed to be insensitive to changes in the boundary conditions for oscillation, whereas a standing wave would be influenced. Changing middle-ear pressure in hum...

We have tested our assumption that infrasound from flutter jumps of displaying cocks is significant for capercaillie (Tetrao urogallus) orientation. Seven captive females were used for playback experiments during a period when they were extremely disposed to mating and thus expected to respond intensively to signals from males. However, no behaviou...

Spontaneous otoacoustic emissions (SOAE) were measured in 10 lizard species from the families Iguanidae, Agamidae and Anguidae. The typical feature of these papillae is that the hair cells in the higher-frequency papillar regions that produce SOAE are not covered by a tectorial structure. The number of hair cells in the species used here was betwee...

We have tested our assumption that infrasound from flutter jumps of displaying cocks is significant for capercaillie (Tetrao urogallus) orientation. Seven captive females were used for playback experiments during a period when they were extremely disposed to mating and thus expected to respond intensively to signals from males. However, no behaviou...

The inner ear in the group of archosaurs (birds, crocodilians, and extinct dinosaurs) shows a high degree of structural similarity, enabling predictions of their function in extinct species based on relationships among similar variables in living birds. Behavioral audiograms and morphological data on the length of the auditory sensory epithelium (t...

We examined the sounds made by displaying male capercaillies on a lek in the Black Forest for infrasonic components. Vocalizations did not contain infrasound, whereas flutter jumps produced substantial low-frequency sound energy, with regularly spaced frequency peaks and maximum energy below 20Hz. This pattern was found in recordings from different...

Spontaneous otoacoustic emissions (SOAEs) are indicators of active processes in the inner ear and are found in all classes of land vertebrates. In the Australian bobtail lizard, earlier work showed that otoacoustic emissions are generated by an active motility process in the hair-cell bundle. This is likely to be driven by calcium-sensitive mechani...

Lizards have highly sensitive ears, but most lizard heads are small (1-2 cm in diameter) compared to the wavelengths of sound of frequencies to which they are most sensitive (1-4 kHz, wavelengths 34-8.5 cm). Therefore, the main cues to sound direction that mammals use - binaural time and intensity cues due to arrival-time differences and sound shad...

Spontaneous otoacoustic emissions (SOAEs) are indicators of active processes in the inner ear and are found in all classes of land vertebrates. In the Australian bobtail lizard, earlier work showed that otoacoustic emissions are generated by an active motility process in the haircell bundle. This is likely to be driven by calcium-sensitive mechanis...

Hair cells are the mechanoreceptive cells of the vertebrate lateral line and inner ear. In addition to their sensory function, hair cells display motility and thus themselves generate mechanical energy, which is thought to enhance sensitivity. Two principal cellular mechanism are known that can mediate hair-cell motility in vitro. One of these is b...

Active processes in the inner ear of lizards can be monitored using spontaneous otoacoustic emissions (SOAE) measured outside the eardrum. In the Australian bobtail lizard, SOAE are generated by an active motility process in the hair-cell bundle. This mechanism has been shown to be sensitive to the calcium-chelating agent 1,2-bis(o-aminophenoxy)eth...

Monitors (all of which belong to the genus Varanus) make up a very uniform family of often large lizards. They have a large auditory papilla that is not highly specialized, but is divided into two unequal sub-papillae. All hair cells are covered by a tectorial membrane. Spontaneous otoacoustic emissions (SOAE) were examined in Cape monitor lizards...

The ears of all vertebrate species use sensory hair cells (Fig. 3.1) to convert mechanical energy to electrical signals compatible with the nervous system. However, although the basic structure of hair cells is ubiquitous among the vertebrates and hair cells are also found in the lateral line of fishes and aquatic amphibians, a growing body of lite...

1. The Importance of Evolutionary Studies 2. The Establishment of Receptors for Sensing Mechanical Disturbances 3. Strategies for Increasing Sensitivity 4. The Independent Development and Specialization of the Ears of Major Groups of Land Vertebrates 5. The Need for More Work on Neglected Groups 6. Brain Pathway Evolution and Neural Processing Patt...

Lizards are as structurally diverse as other groups of amniotes, such as mammals and birds. When we look at their hearing organs, however, the structural variety that we see in lizards exceeds that seen in any other amniote group. Its length alone can vary up to a factor of more than 40 times. In fact, this may well be the most variable sense organ...

The aim of this introductory chapter is twofold. First, we provide a phylogenetic framework to enable the reader to place each animal group being discussed in the correct historical context. Second, some major background themes concerning the evolution of the structure and the function of vertebrate hearing organs are briefly introduced. With this...

The study of the evolution of the ear is only possible using two approaches. The first approach, looking at evolutionary changes in the structure of the ear in fossil organisms, is the obvious and most direct. In fact, this turns out to be remarkably difficult, since the ear region is not always well preserved in fossils, and soft tissue components...

Among amniotes a group named archosaurs includes the crocodilians, extinct dinosaurs, and birds (see Phylogeny, below). Because of these evolutionary relationships, the archosaurs are considered together in this chapter. The available data on inner-ear structure and function from different archosaur species (various birds and Caiman crocodilus) is...

The function of vertebrate hearing is served by a surprising variety of sensory structures in the different groups of fish, amphibians, reptiles, birds, and mammals. This book discusses the origin, specialization, and functional properties of sensory hair cells, beginning with environmental constraints on acoustic systems and addressing in detail t...

It is not known whether active processes in mammals and non-mammals are due to the same underlying mechanism. To address this, we studied the size and density of particles in hair-cell membranes in mammals, in a lizard, the Tokay gecko, and in a bird, the barn owl. We surmised that if the prominent particles described in mammalian outer-hair-cell m...

The tectorial membrane is an enigmatic, non-cellular structure that covers auditory hair cells in the inner ear. Due to its gel-like constitution, its properties and precise function have been difficult to study. In some lizard families, there are whole groups of hair cells that are not covered by a tectorial membrane, and these offer the opportuni...