Littérature scientifique sur le sujet « Auditive fibers »

The pratuokng is an idiochord tube zither, which is a musical instrument. The Bidayuh Biatah pratuokng bamboo sound radiators of Annah Rais in Padawan, Sarawak, Malaysia are made up of seven strings and one drum. The sound reproduction capabilities are unique and innovative. This study intends to highlight the importance of sound studies in the studio setting. The frequency spectrum was evaluated using a Fast Fourier Transform (FFT) analysis via PicoScope oscilloscopes, and the time frequency analysis (TFA) using Adobe Audition that produced the spectrograms. The observations and perceptions offered by the actual meaning of this bamboo tube zither instruments showed that the notes of the pratuokng strings are E, D, F, Ab, B, A#, and B, respectively. The drum note is A. The 1st, 2nd, 3rd(A), 3rd(B), 4th(A), 4th(B), and 5th strings are 320 Hz (E4 = 329.63), 300 Hz (D4 = 293.67), 350 Hz (F4 = 349), 410 Hz (A4b = 415), 490 Hz (B4 = 493), 470 Hz (A4# = 466), and 500 Hz (B4 = 493), respectively, i.e., with note E, D, F, Ab, B, A#, and B, respectively. The drum is 210 Hz (A3 = 220). The signal in the frequency spectrum showed both distinct fundamental and higher partial frequencies. In particular, the first octave are present except for string 4B and 5. The inconsistent number of partials in each string is due to the inconsistent thickness of the raised fiber from the bamboo tube.

Nowadays, sound control has been regarded as one of the important requirements for human comfort. For an instance, control of room acoustic enables the room to achieve a good auditive environment for effective speech deliverance and presentations. Synthetic fibers such as glass wool fiber are commonly used for sound absorption. Over the years, it was discovered that synthetic fibers are expensive and possess potential hazard to environment and human health. Therefore, growing attention has been turned to natural fibers as an alternative to synthetic fibers. This paper demonstrates the feasibility of spent tea leaf (STL) fiber as an eco-friendly sound absorbing material. STL fiber is a by-product which was extracted from tea plant. It is unique with fresh aroma and rich in phenolic extractive content. Three different grades of STL fiber were studied and the acoustic property was analyzed in terms of sound absorption coefficient (SAC). Results showed that all the samples obtained maximum SAC above 0.70 at frequency range of 1993-3861 Hz. Furthermore, it was found that finest STL fiber grade exhibits better acoustic performance among others with a maximum SAC of 0.88 at 1993 Hz. Besides, the effect of latex binder on the acoustic property of STL fiber was also analyzed. Results suggest that the types of latex binder did not influence the acoustic performance of STL fiber. The overall results indicate that STL fiber can be a promising environment-friendly sound absorbing material.

ABSTRACT Purpose To identify the pathophysiological definitions adopted by studies investigating “cochlear synaptopathy” (CS) and “hidden hearing loss” (HHL). Research strategies The combination of keywords “Auditory Synaptopathy” or “Neuronal Synaptopathy” or “Hidden Hearing Loss” with “etiology” or “causality” or “diagnosis” was used in the databases EMBASE, Pubmed (MEDLINE), CINAHL (EBSCO), and Web of Science. Selection criteria Studies that investigated CS or HHL in humans using behavioral and/or electrophysiological procedures were included. Data analysis Data analysis and extraction were performed with regard to terminology, definitions, and population. Results 49 articles were included. Of these, 61.2% used the CS terminology, 34.7% used both terms, and 4.1% used HHL. The most-studied conditions were exposure to noise and tinnitus. Conclusion CS terminology was used in most studies, referring to the pathophysiological process of deafferentiation between the cochlear nerve fibers and inner hair cells.

L’approche génétique des formes héréditaires de surdité a été efficace pour révéler la physiologie moléculaire de la cochlée. En revanche, elle a fourni jusqu’à présent peu d'informations sur le système auditif central. L’hypothèse de mon laboratoire est qu’une partie des atteintes auditives centrales dans les formes génétiques de surdité seraient passées inaperçues en raison de l’atteinte cochléaire, qui prive le cerveau auditif de tout ou partie des informations acoustiques qu’il reçoit normalement. Mon objectif est de caractériser ces déficits centraux et périphériques masqués dans plusieurs formes génétiques de surdité par la caractérisation du rôle cérébral d’un gène pour lequel des mutations entraînent une surdité périphérique et une susceptibilité aux crises audiogènes chez la souris. Dans la cochlée, Otogéline-like (Otogl) est impliquée dans la cohésion de la touffe ciliaire et dans la membrane tectoriale. Mes résultats ont montré une expression d’Otogl dans les fibres auditives du noyau cochléaire et dans d’autres structures de la cochlée, révélant de nouveaux rôles joués par Otogl dans la cochlée et les voies rétro-cochléaires. Des défauts fonctionnels dans le traitement du son ont été également observés chez les souris hétérozygotes qui n’ont pas de défauts d’audition. Otogl a donc un rôle dans les voies rétrocochléaires en plus de son rôle cochléaire. Mes résultats montrent qu’Otogl est essentiel au fonctionnement de fibres auditives particulières, dites à haut seuil. Les souris mutantes Otogl sont un nouveau modèle d’étude de ces fibres et de leur rôle dans la survenue des crises audiogènes chez la souris
The genetic approach of inherited forms of deafness has been particularly effective for deciphering the molecular physiology of the cochlea. In contrast, this genetic dissection has so far provided little information about the central auditory system. The hypothesis of my laboratory is that part of the central hearing defects in genetic forms of deafness would be concealed due to cochlear damages, which deprive the auditory brain of all or part of the acoustic information it receives. The objective of my thesis was to characterize these masked central and peripheric deficits in a new mutant mouse model for Otogl, a genetic form of deafness. Mutations in Otogl cause peripheral deafness but are also associated to a susceptibility to audiogenic seizures, reflex seizures induced by a loud sound. In the cochlea, otogl is involved in the cohesion of the hair bundle, the mechanical antenna to the sound of sensory cells and in the tectorial membrane. My results showed that Otogl is expressed in the fibers of the primary auditory nerve and in additional structures of the cochlea, unveiling new roles for Otogl in the cochlea and the central auditory pathways. I also uncovered functional deficits in sound processing in heterozygous Otogl+/- mice that did not have peripheral hearing loss. Otogl therefore has a retrocochlear role in addition to its role in the cochlea. These results involve a particular category of auditory nerve fibers, the high-threshold fibers. Otogl mutant mice are a new model for studying high-threshold fibers and their role in the occurrence of audiogenic seizures in mice

Contexte : La compréhension de la parole dans le silence est dépendante des mécanismes de codage de l’enveloppe temporelle du signal sonore. Une anomalie du codage (d’origine infectieuse, immunitaire, génétique, tumorale, ou environnementale) entraine irrémédiablement une diminution des performances audiométriques vocales. Les méthodes d’exploration fonctionnelle de la cochlée (potentiels d’action composite du nerf auditif, potentiel évoqués auditifs précoces) utilisent des stimuli sonores simples (clics, bouffées tonales) pour détecter une anomalie de codage des indices temporels. Le but de cette étude était de développer une méthode électrophysiologique capable de mesurer les réponses du nerf auditif à des stimuli modulés en amplitude.Matériel et méthodes : La réponse électrophysiologique du nerf auditif a été mesurée à l’aide d’une électrode placée sur la niche de la fenêtre ronde de la cochlée de gerbilles et de rats vieillissants. Les stimuli acoustiques consistaient en des bandes de bruit de 20 secondes modulées sinusoïdalement en amplitude et centrées sur 4, 8 et 16 kHz. Nous avons étudié le niveau, la profondeur de modulation, la fréquence de modulation et la fréquence porteuse.Résultats : Notre étude sur le modèle de perte sélective neuronale (ouabain) montre que l’analyse des potentiels globaux cochléaires permet de détecter une perte de fibres à basse activité spontanée dans le nerf auditif, résultat important car indétectable (« surdités cachées ») actuellement avec les tests utilisés en routine en clinique (EcoG et PEA) (Batrel, Huet, Hasselmann et al, Plos One 2017). Ensuite, en combinant le stimulus de cette étude avec une fonction sinusoïdale, nous avons développé et validé une méthode pour évaluer la qualité de codage de l’enveloppe par le nerf auditif. Nous avons appliqué cette méthode sur un modèle de vieillissement (rat Sprague-Dawley). Nos résultats suggèrent que le viellissement entraine une modifcation du phénotype des fibres du nerf auditif sans pertes de fibres associées (article Occelli, Hasselmann et al, soumis à eNeuro). Conclusion : Notre travail démontre qu’il est indispensable d’élargir le nombre de techniques d’exploration fonctionnelle de la cochlée car les tests utilisés en routine en clinique ne permettent pas de déceler des déficits subtils d’encodage dans le nerf auditif. La mesure de l’activité soutenue des fibres permet de détecter la perte sélective des neurones à basse activité spontanée, indétectable avec les méthodes classiques. Le changement de phénotype des fibres observé au cours du vieillissement du rat Sprague-Dawley est détectable avec notre méthode alors qu’il ne l’est pas avec le potentiel d’action composite du nerf auditif
Background: Speech intelligibility in quiet is critically dependent on the temporal envelope of a sound signal. An abnormal coding of this temporal cue (due to infectious, immune, genetic, tumoral or environmental of origin) implies a decrease of speech recognition scores. The current proxy to probe deafness in clinical framework (Compound Action Potential of the auditory nerve, auditory brainstem responses) uses simplistic stimuli (clicks, tone bursts) to detect a such abnormal coding of the temporal cues. The aim of this study was to develop a new electrophysiology method in murins able to measure the auditory nerve responses to amplitude-modulation stimuli.Material and methods: The electrophysiology response of the auditory nerve was recorded using an electrode implanted onto the round window niche on normal-hearing gerbil cochlea and aging rat cochlea. The acoustical stimuli consisted of 20 seconds sinusoidally amplitude-modulated noise-band centered on 4, 8 and 16 kHz. We have studied varying sound level, the modulation depth, the modulation frequency and the carrier frequency.Results: Our study on the selective fiber loss ouabain model show the mass potentials recorded at the round window enable the detection of low spontaneous rate fibers in gerbil auditory nerve. This result is important because the current clinical used tests aren’t enough sensitive to detect a such coding impairment (CAP, ABR) (Batrel, Huet, Hasselmann et al., 2017). Then we combined the stimulus of this previous study with a sinusoidal function to develop a new method to assess the envelope coding by the auditory nerve. We validated this new method. Last, we used our method on an aging model (Sprague-Dawley rat). Our results suggest aging leads to a phenotype change of auditory nerve fibers without associated fiber loss (article Occelli, Hasselmann et al, submitted to eNeuro).Conclusion: Our study shows it’s indispensable to expand the number of tools to probe the cochlea because the current clinical used tests aren’t enough sensitive to detect subtle deficits of encoding in the auditory nerve. The recording of the fiber sustained activity enable to detect the selective loss of low-spontaneous rate neurons. A such loss is undetectable with classical clinical tools. The phenotype change of fibers we observed in aging Sprague-Dawley rats is detectable with our method whereas it’s not using the compound action potential of the auditory nerve

O nervo vestíbulo-coclear da cobaia possui peculiaridades não encontradas em outros nervos periféricos. Não foram encontradas informações detalhadas sobre os aspectos morfométricos do VIII nervo craniano em cobaias adultas na literatura. A avaliação descritiva e quantitativa no presente estudo, evidencia informações que precedem o estudo das alterações que ocorrem em modelos experimentais de neuropatias do VIII nervo craniano e as doenças ou lesões que possam afetar o homem. Foram utilizadas 8 cobaias adultas, perfundidas com glutaraldeído a 2,5% em tampão cacodilato de sódio (0,025 M). Seus nervos direito e esquerdo (n=6, 4 nervos direito e 2 esquerdos) foram dissecados na região mediana do nervo e pós fixado com tetróxido de ósmio (OsO4) a 1% e incluídos em resina epóxi Poly/Bed 812®. Os fragmentos foram cortados em secções transversais semifinas seriadas (6 nervos) com uma espessura de 0,5 μm e corados com azul de toluidina para a microscopia de luz. Foram analisados os aspectos histológicos descritivos e topográficos do nervo vestíbulo-coclear em cobaias adultas, bem como os aspectos histométricos na parte mediana do nervo, no referente a densidade de fibras mielínicas, a distribuição dos diâmetros de tal tipo de fibras mielínicas, ao cálculo da razão G e o número de vasos sangüíneos encontrados dentro da área de cada nervo. O nervo coclear é envolvido pelo vestibular na porção inicial da junção de ambos. O conjunto, nervos coclear e vestibular e nervo vestíbulo-coclear têm a aparência bifurcada da letra Y, na horizontal com os ramos lateralizados, possuindo em média 5 mm de comprimento. É ricamente vascularizado e documenta uma completa interposição das fibras dos nervos coclear e vestibular, quando o fascículo do VIII nervo está completamente constituído. As suas fibras mielínicas dispõem-se paralelamente em seu sentido longitudinal e são circundadas por escasso tecido endoneural. Não foram evidencias fibras amielínicas no VIII nervo. A distribuição das fibras mielínicas no segmento mediano do VIII nervo craniano foi unimodal, havendo predomínio de fibras com 3,5 m de diâmetro. O número de fibras foi de 5.390 ± 1.504 fibras. O diâmetro das fibras variou de 1,5 a 6 m de diâmetro. Os axônios com 2,5 m de diâmetro foram predominantes quantitativamente: 6.757 ± 1.922 axônios. O diâmetro axonal variou entre 1 a 4,5 m. A densidade média das fibras do VIII nervo em seu segmento mediano foi de 41.474 ± 4384 fibras/mm2. O diâmetro fascicular foi de 0,77 ± 0,04 mm. A razão G varia de 0,2 a 0,9. O maior número de fibras tem razão G de 0,7 e 0,6, respectivamente, predominando as fibras com 0,7. Os resultados descritos neste trabalho científico são originais, contendo alguns resultados inéditos e pouco estudados na literatura científica sobre a anatomia e morfometria do VIII nervo craniano em cobaia. O nervo vestíbulo-coclear da cobaia é um nervo sensitivo aferente especial, e bem diferente em sua anátomo-fisiologia de todos os outros nervos sensitivos e motores encontrados nos mamíferos. A cobaia adulta é um excelente modelo experimental para o estudo do nervo vestíbulo-coclear, semelhantes aos de humanos.
The vestibulocochlear (VIIIth cranial nerve) nerve of guinea pigs have special features not common for peripheral nerves in general. There are no detailed reports on the morphometric characteristics of the VIII nerve in adult guinea pigs. This is a descriptive and qualitative study that shows normal parameters that are useful in experimental models of the VIIIth nerve neuropathy. Eight adult guinea pigs were perfused with 2.5% glutaraldehyde in isotonic cacodilate buffer (0.025M). The right (N=4) and left (N=2) nerves were dissected in the median region, post-fixed in 1% osmuin tetroxide and embedded in epoxy resin. Semithin (0.5 µm) serial transverse sections were stained with 1% toluidine blue for light microscopy study. The descriptive histology and the topographical and histometric aspects of the median region of the nerve were analyzed, including myelinated fiber density, myelinated fiber diameter distribution, g ratio and number of endoneural capillary vessels. The cochlear nerve is enveloped by the vestibular nerve when they join together. Both, the cochlear and the vestibular nerves join to form the vestibulocochlear nerve with a Y shape, with approximately 5 mm in length. The nerve is widely vascularized and presents a complete mixture of the vestibular and cochlear myelinated fibers when the VIII nerve fascicle is constituted. The myelinated fibers are longitudinally oriented and present few endoneural connective tissue in between. No unmyelinated fibers were evidenced in the VIII nerve. The myelinated fiber diameter distribution was unimodal, with a peak at 3.5, and intervals between 1,5 and 6 m. The average number of fibers was 5.390 ± 1.504. The myelinated axon diameter distribution was also unimodal, with a peak at 2.5 µm of diameter were predominant quantitatively: 6.757 ± 1.922, and intervals between 1 and 4.5 µm. The average myelinated fiber density was 41.474 ± 4384 mm2, spread in a fascicular diameter of 0.77 ± 0.04 mm. The g ratio values varied from 0.2 to 0.9 and most of the myelinated fibers showed g ratio values of 0.7. Our results are original and only few parameters studied here were described in the literature. The vestibulocochlear nerve of the guinea pigs is a special afferent nerve, differing from other peripheral nerves (sensitive and motor) in its main anatomic and physiological characteristics, compared to other nerves from mammals. The adult guinea pig is an excellent model for the vestibulocochlear nerve neuropathy studies once it is similar to the human nerve.

Contexte: La réponse synchrone des fibres auditives, évaluée à partir de l'onde I des potentiels d'action évoqués auditifs (PEA), ou à partir du potentiel d'action composite (PAC) du nerf auditif, est l'élément clé du dépistage des neuropathies auditives. De récentes études ont toutefois montré que le seuil et l'amplitude de cette réponse pouvaient être absolument normaux malgré une perte importante de fibres du nerf auditif. Dans ce travail de thèse, nous proposons une nouvelle méthode d'exploration fonctionnelle, potentiellement applicable à l'homme, rendant mieux compte du nombre et de l'intégrité des fibres du nerf auditif. Cette méthode a été évaluée à l'aide d'un modèle pharmacologique de neuropathie physiologiquement pertinent.Matériel et méthodes: Chez des gerbilles, une perte sélective de fibres auditives a été induite par application d'une faible concentration d'ouabaïne dans la niche de la fenêtre ronde de la cochlée. Cette neuropathie a ensuite été caractérisée par des comptages de synapses (immunohistochimie/imagerie confocale 3D) et l'enregistrement de l'activité unitaire de fibres du nerf auditif. Les PAC et l'activité soutenue du nerf ont été enregistrés 6 jours après l'application d'ouabaïne, à l'aide d'une électrode de recueil disposée dans la niche de la fenêtre ronde. Résultats: L'application d'ouabaïne induit une perte spécifique des fibres à basse activité spontanée (AS<0,5 potentiel d'action/sec) comme observé au cours du vieillissement et après une surexposition sonore. La disparition de cette population de fibres est indétectable à l'aide du PAC car leur réponse unitaire est à la fois retardée et désynchronisée. Par contre, l'amplitude de la réponse soutenue du nerf se révèle être un bien meilleur indicateur de la perte des fibres à basse activité spontanée. Pour aller plus loin, nous avons mis au point une méthode qui permet d'observer l'activité synchrone et soutenue du nerf auditif dans une même réponse. Cette approche rend compte des trois mécanismes de fusion vésiculaire (libération rapide, lente et soutenue) de la première synapse auditive.Conclusion: L'analyse de la réponse soutenue du nerf auditif est une approche fiable pour déterminer le nombre et le phénotype fonctionnel des fibres qui composent le nerf auditif. Cette méthode, applicable à l'homme, devrait améliorer le dépistage des neuropathies, avec une meilleure différenciation des atteintes d'origine synaptique et/ou neuronale.Mots clés: Cochlée, nerf auditif, potentiel d'action composite, activité soutenue du nerf auditif, enregistrement unitaires, ouabaïne, neuropathie
Background: The synchronous activation of the auditory nerve fibers (ANFs), is commonly studied through the compound action potential (CAP), or the auditory brainstem responses (ABR), to probe deafness in experimental and clinical settings. Recent studies have shown that substantial ANF loss can coexist with normal hearing threshold, and even unchanged CAP amplitude, making the detection of auditory neuropathies difficult. In this study, we took advantage of the round window neural noise (RWNN) to probe ANF loss in a physiologically-relevant model of neuropathy.Material and methods: ANF loss was induced by the application of ouabain onto the round window niche. CAP and RWNN of the gerbil's cochlea were recorded through an electrode placed onto the round window niche, 6 days after the ouabain application. Afferent synapse counts and single-unit recordings were carried-out to determine the degree and the nature of ANF loss, respectively. Results: Application of a low ouabain-dose into the gerbil RW niche elicits a specific degeneration of low spontaneous rate (SR) fibers, as shown by single-unit recordings. Simultaneous recordings (CAP/single-unit) demonstrate that low-SR fibers have a weak contribution to the CAP amplitude because of their delayed and broad first spike latency distribution. However, the RWNN amplitude decreases with the degree of synaptic loss. The RWNN method is therefore more sensitive than CAP to detect low-SR fiber loss, most probably because it reflects the sustained discharge rate of ANFs. Based on these data, we proposed a far-field method (Peri-stimulus time response-PSTR) to assess the fast, slow, and sustain vesicular release at the first auditory synapse.Conclusion: The round window neural noise is a faithful proxy to probe the degree and the SR-based nature of fiber loss. This method could be translated into the clinic to probe hidden hearing loss and orient the practitioner toward synaptopathy and/or neuropathy.Key words: Cochlea, auditory nerve, compound action potential, round window neural noise, single fiber recording, ouabain-induced neuropathy

•Objetivos: Estudiar la predisposición que produce el uso de cannabis a padecer un trastorno psicótico. •Material y métodos: Descripción de un caso clínico de trastorno esquizofreniforme comórbido con trastorno por uso de cannabis y revisión bibliográfica de la relación entre ambos. •Resultados: Varón de 20 años, procedente de Senegal, en situación administrativa irregular, que reside en un piso de acogida. Consumidor habitual de cannabis y alcohol esporádico. Acude al servicio de urgencias acompañado por la Trabajadora Social de su centro, que refiere cambios de conducta en los últimos días. La entrevista se realiza mediante un traductor, por importante barrera idiomática, que refiere insomnio de días de evolución, alucinaciones auditivas de contenido místico y autorreferencial, Alá, el profeta, le ordena llevar a cabo distintas acciones para evitar el mal. Presenta una conducta muy desorganizada, como escribir en un papel una secuencia numérica y recoger fibras de tejidos y anudarlas. También comenta que en casa venía realizando limpieza de forma compulsiva. Reconoce haber llegado a autoinfligirse lesiones en los muslos para evitar hacer “lo malo”. Ingresa en nuestra unidad para estabilización clínica e inicio de tratamiento antipsicótico, presentando mejoría tras dos semanas del mismo y el cese de consumo de tóxicos. Se decide alta con diagnóstico de Trastorno Esquizofreniforme. •Conclusiones: Según la literatura científica revisada, existe una clara relación entre el consumo de cannabis y la aparición de clínica psicótica en sujetos con vulnerabilidad previa, que en algunos casos deriva en trastornos crónicos como la esquizofrenia. Aunque solo una minoría de consumidores presenten alteraciones psicóticas, se debe incidir en medidas preventivas sobre su consumo, especialmente en población vulnerable, como adolescentes o consumidores de altas dosis.