3,347 research outputs found

    A model and experimental approach to the middle ear transfer function related to hearing in the humpback whale (Megaptera novaeangliae)

    Get PDF
    At present, there are no direct measures of hearing for any baleen whale (Mysticeti). The most viable alternative to in vivo approaches to simulate the audiogram is through modeling outer, middle, and inner ear functions based on the anatomy and material properties of each component. This paper describes a finite element model of the middle ear for the humpback whale (Megaptera novaeangliae) to calculate the middle ear transfer function (METF) to determine acoustic energy transmission to the cochlea. The model was developed based on high resolution computed tomography imaging and direct anatomical measurements of the middle ear components for this mysticete species. Mechanical properties for the middle ear tissues were determined from experimental measurements and published values. The METF for the humpback whale predicted a better frequency range between approximately 15 Hz and 3 kHz or between 200 Hz and 9 kHz based on two potential stimulation locations. Experimental measures of the ossicular chain, tympanic membrane, and tympanic bone velocities showed frequency response characteristics consistent with the model. The predicted best sensitivity hearing ranges match well with known vocalizations of this species

    Anatomy of the odontocete tympano-periotic complex in regard to sound conduction

    Get PDF
    This aim of this thesis was to examine the auditory anatomy of odontocetes, with a particular focus on Cuvier’s beaked whale (Ziphius cavirostris) to determine if there are any anatomical features unique to this species that may be of functional significance. Cuvier’s beaked whale was the prime species of interest in this study given the over representation of this species at atypical stranding events associated with the use of naval sonar. Features traditionally described in odontocete sound reception and anatomical features that are involved with cochlear stimulation via bone conducted vibrations in terrestrial mammals were examined with computed and micro-computed tomography. The morphology of the Z. cavirostris varied from other odontocetes examined, with a decrease in the size of the tympanic plate and medial sulcus of the mallear ridge. Given the role credited to these structures in odontocete sound conduction, this diminution may decrease the efficiency at which vibrations are transferred via these structures. There was also an increased degree of osseous contact between the tympanoperiotic complex and the skull and an increase in the diameter, and decreased impedance, of the cochlear aqueduct. These features may increase the sensitivity of the cochlea of Z. cavirostris to stimulation via bone conducted vibrations via the direct transfer of cranial vibrations to the periotic bone and the conduction of audio-frequency pressure waves from the cerebrospinal fluid to the cochlea via the cochlear aqueduct. The simultaneous presence and phase differences of these routes of BCV may provide a supra sensitivity to cochlear stimulation at low and mid frequencies and create an interaural intensity difference that may form the basis for an exciting novel hypothesis to explain directional hearing via bone conducted vibrations

    Anatomy of the odontocete tympano-periotic complex in regard to sound conduction

    Get PDF
    This aim of this thesis was to examine the auditory anatomy of odontocetes, with a particular focus on Cuvier’s beaked whale (Ziphius cavirostris) to determine if there are any anatomical features unique to this species that may be of functional significance. Cuvier’s beaked whale was the prime species of interest in this study given the over representation of this species at atypical stranding events associated with the use of naval sonar. Features traditionally described in odontocete sound reception and anatomical features that are involved with cochlear stimulation via bone conducted vibrations in terrestrial mammals were examined with computed and micro-computed tomography. The morphology of the Z. cavirostris varied from other odontocetes examined, with a decrease in the size of the tympanic plate and medial sulcus of the mallear ridge. Given the role credited to these structures in odontocete sound conduction, this diminution may decrease the efficiency at which vibrations are transferred via these structures. There was also an increased degree of osseous contact between the tympanoperiotic complex and the skull and an increase in the diameter, and decreased impedance, of the cochlear aqueduct. These features may increase the sensitivity of the cochlea of Z. cavirostris to stimulation via bone conducted vibrations via the direct transfer of cranial vibrations to the periotic bone and the conduction of audio-frequency pressure waves from the cerebrospinal fluid to the cochlea via the cochlear aqueduct. The simultaneous presence and phase differences of these routes of BCV may provide a supra sensitivity to cochlear stimulation at low and mid frequencies and create an interaural intensity difference that may form the basis for an exciting novel hypothesis to explain directional hearing via bone conducted vibrations

    Short-term plasticity of neuro-auditory processing induced by musical active listening training

    Get PDF
    Although there is strong evidence for the positive effects of musical training on auditory perception, processing, and training-induced neuroplasticity, there is still little knowledge on the auditory and neurophysiological short-term plasticity through listening training. In a sample of 37 adolescents (20 musicians and 17 nonmusicians) that was compared to a control group matched for age, gender, and musical experience, we conducted a 2-week active listening training (AULOS: Active IndividUalized Listening OptimizationS). Using magnetoencephalography and psychoacoustic tests, the short-term plasticity of auditory evoked fields and auditory skills were examined in a pre-post design, adapted to the individual neuro-auditory profiles. We found bilateral, but more pronounced plastic changes in the right auditory cortex. Moreover, we observed synchronization of the auditory evoked P1, N1, and P2 responses and threefold larger amplitudes of the late P2 response, similar to the reported effects of musical long-term training. Auditory skills and thresholds benefited largely from the AULOS training. Remarkably, after training, the mean thresholds improved by 12 dB for bone conduction and by 3–4 dB for air conduction. Thus, our findings indicate a strong positive influence of active listening training on neural auditory processing and perception in adolescence, when the auditory system is still developing

    Suuntakuulo vedessä : välikorvan rakenne ja toiminta lyhyteväpallopäädelfiinillä (Globicephala macrorhynchus)

    Get PDF
    The evolution of whales into fully aquatic, deep-diving animals, which began over 50 million years ago, entailed a dramatic change in their sensory environment and a corresponding reorganization of their sensory systems. For hearing, this had two major consequences. (1) The physics of sound transmission from water into the inner ear required a complete redesign of the sound-transmitting structures (outer and middle ears) of their terrestrial ancestors, which were exquisitely tuned for hearing in air. (2) In the dark deep-sea environment, hearing overtook vision as the primary sense for object detection and localization at a distance. Toothed whales (Odontoceti) are crucially dependent on hearing as they use active high-frequency sounding (echolocation) to localize prey and predators and to communicate with conspecifics. The present thesis addresses aspects of both sound transmission (1) and sound localization (2) in odontocetes. The first aim was to elucidate the mechanical functioning of the middle ear as part of the transmission chain from sound-receiving head structures to the inner ear. The odontocete tympano-periotic complex (TPC) differs significantly from temporal bone complexes of terrestrial mammals. We studied 32 pairs of formaldehyde-glutaraldehyde-fixed TPCs of the short-finned pilot whale Globicephala macrorhynchus. The distribution of vibration amplitudes on the TPC was measured by Laser Doppler Vibrometry while vibrations at different frequencies were applied at a point near the exit of the acoustic nerve. The results suggest that the tympanic plate acts as a lever amplifying the force driving high-frequency vibrations (> 12 kHz) into the inner ear through the ossicular chain. The second aim was to assess whether there exists asymmetry between the left and right middle ears with respect to critical ossicular parameters, and whether this may help in localizing targets in the vertical direction. The malleus, incus and stapes on both sides were weighed with μg accuracy and their lengths as well as the stapedial footplate area measured with 10 μm accuracy. Further, the incudo-stapedial angle was measured from computer tomography images. Significant differences (left values > right values) were found in the weights of the ossicles and in the incudo-stapedial angle. Modelling the amplitude responses of the two ears shows that these asymmetries result in an elevation-dependent difference signal that may support localization of a sound source in the vertical direction. When relating the asymmetry found in Globicephala to earlier reports of ear asymmetries in mammals and birds (one bat species and several owls hunting in the dark), I hypothesized that asymmetry evolves to support sound localization in species that hunt in darkness in three-dimensional space (whether in air or water). As a pilot test of this working hypothesis, we carefully dissected the middle ears and measured ossicular parameters with high accuracy in two mammals, where left-right asymmetry, if present, would necessarily implicate other factors. (1) The sheep, as a close relative of the immediate terrestrial ancestors of whales, might reveal if whale asymmetry depends on phylogenetic heritage. (2) The cat, as a dark hunter active mainly in two dimensions, might reveal if asymmetry is a more general property of nocturnal predators. We found no signs of asymmetry between the middle ears in either of these species.Valaiden evoluutio maanisäkkäistä täysin vesielämään sopeutuneiksi alkoi yli 50 miljoonaa vuotta sitten tuoden suuria muutoksia niiden aistimaailmaan ja aistinelimiin. Vedessä kuuleminen edellytti muutoksia ulko- ja välikorvan rakenteisiin, ja syvällä vedessä kuuloaistia voitiin hyödyntää näköaistia paremmin eri kohteiden havaitsemiseen ja paikantamiseen. Hammasvalaat, kuten delfiinit, ovat täysin riippuvaisia kuulostaan sekä kaikuluodatessaan että lajitovereidensa kanssa kommunikoidessaan. Ensin selvitin välikorvan mekaniikkaa ja äänen kulkua ympäröivästä vedestä sisäkorvaan. Valailla täryluun ja kallioluun muodostama kokonaisuus eroaa rakenteeltaan selvästi maanisäkkäiden vastaavista luista. Eri taajuisten äänten aikaansaaman värähtelyn jakautumista ja laajuutta mitattiin Laser Doppler-vibrometrian avulla pallopäädelfiineihin kuuluvan lyhyteväpallopään korvissa. Tulokset ennustavat täryluuhun kuuluvan tärylevyn toimivan vahvistavana vipuna korkeiden taajuuksien (> 12 kilohertsiä) kulkeutumisessa välikorvan kuuloluuketjun kautta sisäkorvaan. Seuraavaksi selvitin mahdollista epäsymmetriaa oikean ja vasemman korvan välillä. Mittasin lyhyteväpallopään useiden korvaparien kuuloluiden (vasara, alasin ja jalustin) massat ja pituudet, jalustimen päätelevyn pinta-alan, sekä alasimen ja jalustimen välisen kulman. Massojen ja kulman suhteen havaittiin vasemmanpuoleisten rakenteiden olevan suurempia kuin oikeanpuoleisten. Äänen aikaansaamaa värähtelyä mallinnettaessa tällainen epäsymmetria tuottaa eroja signaaleihin korvien välillä, mikä saattaa auttaa eläintä paikantamaan äänilähteen sijainti vertikaalisesti. Vertasin lyhyteväpallopään epäsymmetriaa aiemmissa tutkimuksissa löydettyyn epäsymmetriaan kaikuluotaavalla lepakolla ja pimeässä saalistavilla pöllöillä. Esitän hypoteesina, että tällainen epäsymmetria on kehittynyt evoluution kuluessa parantamaan suuntakuuloa pimeässä saalistavilla eläimillä (vedessä tai ilmassa), joiden on arvioitava suuntaa myös vertikaalisesti, ei pelkästään horisontaalisesti. Testasin teoriaa mittaamalla yllämainittuja korvan rakenteita kahdelta maanisäkkäältä; lampaalta, joka sorkkaeläimenä on valaiden läheinen sukulainen, sekä kissalta, joka saalistaa yöllä, mutta on vähemmän riippuvainen suuntakuulosta kuin lepakko. Mitään epäsymmetriaa ei näiden lajien korvien väliltä löytynyt

    Auditory spatial deficits in brainstem disorders

    Get PDF
    Purpose Brainstem disorders seem to negatively influence the central auditory system, causing spatial hearing deficits. Material and methods We tested 11 patients with brainstem lesions due to ischemic stroke (IS), multiple sclerosis (MS), or cerebellopontine angle tumor (CPAT) together with 50 age- and sex-matched healthy volunteers. We used pure tone audiometry (PTAud), brainstem auditory evoked potentials (BAEPs) and the horizontal minimum audible angle test (HMAAT) for 8 azimuths with binaural stimulation. Results The chosen patients and the controls had normal or near normal hearing in PTAud. BAEPs interaural wave I–V latency difference was over 7 times longer in the patients group compared to the controls. Additionally, 9 of the 11 patients (81.1%) had abnormal HMAAT results. The biggest quantitative disturbances in HMAAT were present in the CPAT and the MS patients. The sound localization ability in HMAAT was significantly worse in the patients in 0° azimuth in comparison with the controls, and in 45° and 90° azimuth in patients with auditory pathway involvement compared with the ones without the involvement. Conclusions Our study confirms the strong relationship between various brainstem pathologies and sound localization disability and sheds some light on the complexity of the relationship

    Role of middle-ear inertial component of bone conduction in chinchilla

    Get PDF
    Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 53-55).Bone conduction describes the mechanisms that produce a hearing sensation when the skull bones are subjected to vibration. Multiple components and pathways have been suggested to contribute to total bone-conducted sound. They include outer-ear cartilaginous wall compression, middle-ear inertia, fluid inertia, cochlear capsule compression and soft-tissue conduction. Due to the complexity of the possible interactions within these components and pathways, the true stimulus to the inner ear is not fully understood nor has it been adequately quantified. In this thesis work, we examined the relationship between inner-ear sound pressures and its sensory response in addition to determining the relative significance between the outer, middle and inner ear mechanisms that are prominent in bone conduction hearing in chinchilla. Using both mechanical and physiological recording techniques, we measured cochlear responses in chinchilla before and after interruption of the middle-ear ossicular system in both air conduction (AC) and bone conduction (BC) stimulation. Our data suggest that differential intracochlear sound pressure is the driving source to the sensory response of the inner ear in AC and BC. Compared to those in AC, inner-ear sound pressure measurements in BC provide evidence of multiple mechanisms in BC process. After middle ear interruption, pressures in scala vestibuli Psv and scala tympani PST drop by as much as 40 dB in AC, but only decrease in Psv by 10 dB, with almost no change in PST in BC. The difference in the change of both Psv and PST in BC compared to AC suggest the main mechanisms that drive the inner ear response in BC are not derived from the outer ear or middle ear but the inner ear.by David Chhan.S.M

    Hearing in cetaceans : from natural history to experimental biology

    Get PDF
    Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Advances in Marine Biology 63, edited by Michael Lesser, :197-246. Academic Press (Elsevier), 2013. ISBN: 9780123942821. doi:10.1016/B978-0-12-394282-1.00004-1Sound is the primary sensory cue for most marine mammals, and this is especially true for cetaceans. To passively and actively acquire information about their environment, cetaceans have perhaps the most derived ears of all mammals, capable of sophisticated, sensitive hearing and auditory processing. These capabilities have developed for survival in an underwater world where sound travels five times faster than in air, and where light is quickly attenuated and often limited at depth, at night, and in murky waters. Cetacean auditory evolution has capitalized on the ubiquity of sound cues and the efficiency of underwater acoustic communication. The sense of hearing is central to cetacean sensory ecology, enabling vital behaviors such as locating prey, detecting predators, identifying conspecifics, and navigating. Increasing levels of anthropogenic ocean noise appears to influence many of these activities. Here we describe the historical progress of investigations on cetacean hearing, with a particular focus on odontocetes and recent advancements. While this broad topic has been studied for several centuries, new technologies in the last two decades have been leveraged to improve our understanding of a wide range of taxa, including some of the most elusive species. This paper addresses topics including how sounds are received, what sounds are detected, hearing mechanisms for complex acoustic scenes, recent anatomy and physiology studies, the potential impacts of noise, and mysticete hearing. We conclude by identifying emerging research topics and areas which require greater focus.In compiling this review, TAM was supported by the John E. and Anne W. Sawyer Endowed Fund and the Penzance Endowed Fund

    The effect of long-term unilateral deafness on the activation pattern in the auditory cortices of French-native speakers: influence of deafness side

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>In normal-hearing subjects, monaural stimulation produces a normal pattern of asynchrony and asymmetry over the auditory cortices in favour of the contralateral temporal lobe. While late onset unilateral deafness has been reported to change this pattern, the exact influence of the side of deafness on central auditory plasticity still remains unclear. The present study aimed at assessing whether left-sided and right-sided deafness had differential effects on the characteristics of neurophysiological responses over auditory areas. Eighteen unilaterally deaf and 16 normal hearing right-handed subjects participated. All unilaterally deaf subjects had post-lingual deafness. Long latency auditory evoked potentials (late-AEPs) were elicited by two types of stimuli, non-speech (1 kHz tone-burst) and speech-sounds (voiceless syllable/pa/) delivered to the intact ear at 50 dB SL. The latencies and amplitudes of the early exogenous components (N100 and P150) were measured using temporal scalp electrodes.</p> <p>Results</p> <p>Subjects with left-sided deafness showed major neurophysiological changes, in the form of a more symmetrical activation pattern over auditory areas in response to non-speech sound and even a significant reversal of the activation pattern in favour of the cortex ipsilateral to the stimulation in response to speech sound. This was observed not only for AEP amplitudes but also for AEP time course. In contrast, no significant changes were reported for late-AEP responses in subjects with right-sided deafness.</p> <p>Conclusion</p> <p>The results show that cortical reorganization induced by unilateral deafness mainly occurs in subjects with left-sided deafness. This suggests that anatomical and functional plastic changes are more likely to occur in the right than in the left auditory cortex. The possible perceptual correlates of such neurophysiological changes are discussed.</p
    • …
    corecore