Auditory Receptor Research Articles

The single-cell transcriptomic landscape of the topological differences in mammalian auditory receptors.

Mammalian hair cells (HCs) are arranged spirally along the cochlear axis and correspond to different frequency ranges. Serving as primary sound detectors, HCs spatially segregate component frequencies into a topographical map. HCs display significant diversity in anatomical and physiological characteristics, yet little is known about the organization of the cochleotopic map of HCs or the molecules involved in this process. Using single-cell RNA sequencing, we determined the distinct molecular profiles of inner hair cells and outer hair cells, and we identified numerous position-dependent genes that were expressed as gradients. Newly identified genes such as Ptn, Rxra, and Nfe2l2 were found to be associated with tonotopy. We employed the SCENIC algorithm to predict the transcription factors that potentially shape these tonotopic gradients. Furthermore, we confirmed that Nfe2l2, a tonotopy-related transcription factor, is critical in mice for sensing low-to-medium sound frequencies in vivo. the analysis of cell-cell communication revealed potential receptor-ligand networks linking inner hair cells to spiral ganglion neurons, including pathways such as BDNF-Ntrk and PTN-Scd4, which likely play essential roles in tonotopic maintenance. Overall, these findings suggest that molecular gradients serve as the organizing principle for maintaining the selection of sound frequencies by HCs.

Microanatomy of the human tunnel of Corti structures and cochlear partition-tonotopic variations and transcellular signaling.

Auditory sensitivity and frequency resolution depend on the optimal transfer of sound-induced vibrations from the basilar membrane (BM) to the inner hair cells (IHCs), the principal auditory receptors. There remains a paucity of information on how this is accomplished along the frequency range in the human cochlea. Most of the current knowledge is derived either from animal experiments or human tissue processed after death, offering limited structural preservation and optical resolution. In our study, we analyzed the cytoarchitecture of the human cochlear partition at different frequency locations using high-resolution microscopy of uniquely preserved normal human tissue. The results may have clinical implications and increase our understanding of how frequency-dependent acoustic vibrations are carried to human IHCs. A 1-micron-thick plastic-embedded section (mid-modiolar) from a normal human cochlea uniquely preserved at lateral skull base surgery was analyzed using light and transmission electron microscopy (LM, TEM). Frequency locations were estimated using synchrotron radiation phase-contrast imaging (SR-PCI). Archival human tissue prepared for scanning electron microscopy (SEM) and super-resolution structured illumination microscopy (SR-SIM) were also used and compared in this study. Microscopy demonstrated great variations in the dimension and architecture of the human cochlear partition along the frequency range. Pillar cell geometry was closely regulated and depended on the reticular lamina slope and tympanic lip angle. A type II collagen-expressing lamina extended medially from the tympanic lip under the inner sulcus, here named "accessory basilar membrane." It was linked to the tympanic lip and inner pillar foot, and it may contribute to the overall compliance of the cochlear partition. Based on the findings, we speculate on the remarkable microanatomic inflections and geometric relationships which relay different sound-induced vibrations to the IHCs, including their relevance for the evolution of human speech reception and electric stimulation with auditory implants. The inner pillar transcellular microtubule/actin system's role of directly converting vibration energy to the IHC cuticular plate and ciliary bundle is highlighted.

Frequency response analysis and in vitro verification of 3D-printed ossicular replacement materials

As a bridge that transmits airborne sound signals to the auditory receptors of the inner ear, the eardrum and ossicular chain of the middle ear convert sound through two types of conversions: gas–solid (airborne sound signal–eardrum and ossicular chain) and solid–liquid (eardrum and ossicular chain–internal and external lymphatic fluid in the cochlea). This process concentrates and amplifies the sound to the inner ear through the lever principle structure formed by the three ossicles. However, diseases, hereditary factors, or trauma can reduce the sound transmission function of the middle ear. The effectiveness of middle ear replacement prostheses depends on their vibration response to the human auditory perception frequency, from the eardrum to the stapes plate. This response is influenced by the materials, geometry, and design of the replacement prosthesis and eardrum. This study explores the effects of different materials on hearing after artificial ossicular replacement. Usually, human temporal bone models are used for testing and validating numerical results. However, obtaining specimens from living humans is not always feasible. Therefore, we used three-dimensional printing technology to build a model of the middle ear to test the ossicular bone. Titanium alloy TC4, stainless steel 316L, and composite HA/PCL are chosen as materials for ossicular replacement. Using f‍inite element analysis and an in vitro verification experiment, individual replacements of the ossicles and three bone material replacements were conducted for frequency response analysis. The combination of the malleus made of TC4, the incus made of TC4, and the stapes made of HA/PCL were found to bear higher resemblance to a real normal ear ossicular model.

Intranasal delivery of NGF rescues hearing impairment in aged SAMP8 mice

Hearing loss impacts the quality of life and affects communication resulting in social isolation and reduced well-being. Despite its impact on society and economy, no therapies for age-related hearing loss are available so far. Loss of mechanosensory hair cells of the cochlea is a common event of hearing loss in humans. Studies performed in birds demonstrating that they can be replaced following the proliferation and transdifferentiation of supporting cells, strongly pointed out on HCs regeneration as the main focus of research aimed at hearing regeneration. Neurotrophins are growth factors involved in neuronal survival, development, differentiation, and plasticity. NGF has been involved in the interplay between auditory receptors and efferent innervation in the cochlea during development. During embryo development, both NGF and its receptors are highly expressed in the inner ears. It has been reported that NGF is implicated in the differentiation of auditory gangliar and hair cells. Thus, it has been proposed that NGF administration can decrease neuronal damage and prevent hearing loss. The main obstacle to the development of hearing impairment therapy is that efficient means of delivery for selected drugs to the cochlea are missing. Herein, in this study NGF was administered by the intranasal route. The first part of the study was focused on a biodistribution study, which showed the effective delivery in the cochlea; while the second part was focused on analyzing the potential therapeutic effect of NGF in senescence-accelerated prone strain 8 mice. Interestingly, intranasal administration of NGF resulted protective in counteracting hearing impairment in SAMP8 mice, ameliorating hearing performances (analyzed by auditory brainstem responses and distortion product otoacoustic emission) and hair cells morphology (analyzed by microscopy analysis). The results obtained were encouraging indicating that the neurotrophin NGF was efficiently delivered to the inner ear and that it was effective in counteracting hearing loss.

Bimodality of auditory receptors in bush-crickets. Сontinued discussion. It's time to experiment.

Continuation of the discussion on the sensitivity of the chordotonal sensilla of the tympanal organ of bush-crickets to vibratory stimuli. We have previously shown that individual receptors registered directly in the tympanal organ perceive vibrations along with sound stimuli. In addition, scolopidia of the crista acustica possess mixed sensitivity, too, as well as receptors of the intermediate organ. The authors of the comment offered their opinion concerning our applied methods as well as our obtained results. In particular, they noted the dissimilarity of our data from the previously obtained data (the 1970s-1990s), mainly in the laboratory of Prof. K. Kalmring, who assumed that only low-frequency receptors, in particular receptors of the intermediate organ, possess mixed sensitivity. At the same time, receptor activity was recorded in the tympanal nerve without morphological identification of receptors (with the exception of one stained neuron in the prothoracic ganglion). We carried out a series of experiments using the method of K. Kalmring and found that it is possible to register several receptors in the tympanal nerve with different reactions during one experiment: to sound only, also both to vibration stimuli and sound. In the latter case, we dealt with low-threshold receptors, which responded to ultrasound, and this with high probability belonged to the crista acustica. Similar data were previously obtained on the bush-cricket Decticus verrucivorus. In this publication, we explain the methodological features of our work and suggest that the loss of sensitivity to vibrations at the level of the tympanal nerve by some auditory receptors may be due to the ephaptic and/or chemical interaction of the tympanal organ receptors with vibroreceptors of the subgenual or other organs. To verify this hypothesis, it is necessary to conduct additional studies, such as physiological, morphological, and immunohistochemical, along the entire vibroacoustic afferent tract, that is, from the peripheral part to the first switches to the corresponding interneurons.

Functions of the auditory system of biting female mosquitoes (Diptera, Culicidae)

Female mosquitoes possess a complex auditory system, the biological function of which has not yet been fully understood. Male and female mosquitoes are known to mutually adjust the frequencies of their wingbeats when approaching each other. To make such interaction possible, they need to hear each other and to be able to discriminate frequencies. Some recent data indicate that biting female mosquitoes can also use acoustic channel to detect their hosts. One can expect that the parameters of mosquito’s hearing re ect the acoustic properties of noises or other sounds emitted by the host animals. In this regard, it is worth asking whether mosquitoes are able to detect humans by their voices. We studied female mosquitoes of Aedes ( Ochlerotatus ) excrucians Walker. They are abundant in the biotopes where people are likely to be found, for example, along the river banks and in the village parks. In electrophysiological experiments, we measured the frequency-threshold characteristics of auditory receptors. The highest sensitivity of most receptors was found in the frequency range from 40 to 140 Hz, with minimum threshold values of 32-40 dB SPVL (Sound Particle Velocity Level). A comparison of the frequency-threshold characteristics of female mosquitoes with the averaged spectra of human speech indicates that, in most cases, mosquitoes can hear human voices and can use them as a cue for nding and attacking humans.

РАЗВИТИЕ СЛУХОВОГО ВОСПРИЯТИЯ МУЗЫКАНТОВ-ИНСТРУМЕНТАЛИСТОВ С НАРУШЕНИЯМИ ЗРЕНИЯ

The article focuses on the auditory perception of students with profound visual impairments. The category of "perception" is considered in psychology as a process of reflection in the consciousness of an integral sensual image of an object or phenomenon. In the musical-aural perception of musicians with visual impairments, the subjective image of an object, phenomenon or process directly affects the auditory analyzer, and in a latent form the system of motor and tactile analyzers. Musical sound is understood as a pitch or noise sound, carrying the function of a means of a specific semantic expression. The auditory sensations appear due to the effects of periodic oscillations of sound waves on the auditory receptor. The shape of a sound wave's oscillations is reflected in a specific quality — the timbre of sound. When playing a musical instrument, the performer extracts a sound with a certain pitch, dynamics, timbre and duration. The article emphasizes that the development of musical ear of visually impaired musicians, as the ability to perceive and represent musical images, are inextricably linked to the images of memory. It is important that perceptual skills at the level of sensations and auditory perception are formed and developed under the influence of living conditions, training and the requirements of musical and practical activity.

Artificial Tongue Embedded with Conceptual Receptor for Rubber Gustatory Sensor by Electrolytic Polymerization Technique with Utilizing Hybrid Fluid (HF)

The development of gustatory sensors is essential for the development of smart materials for use in robotics, and in the food, beverage, and pharmaceutical industries. We therefore designed a prototype of a rubber tongue embedded with a gustatory receptor mimicking a human tongue using our previously proposed hybrid fluid rubber (HF rubber) and an electrolytic polymerization technique. The fabricated gustatory receptor was composed of Pacinian corpuscles, which are well known and have already been elucidated as effective haptic and auditory receptors in previous studies. Moreover, the receptor has self-powered voltage generated as built-in electricity as a result of the ionized particles and molecules in the HF rubber. The utilization of a layered structure for the Pacinian corpuscles induced a typical response not only to normal and shear forces but to thermal variations. Typical gustatory characteristics, including the initial response voltage and the cyclic voltammogram form, were clearly varied by five tastes: saltiness, sourness, sweetness, bitterness, and umami. These results were due to ORP, pH, and conductivity.

Physiological changes throughout an insect ear due to age and noise - A longitudinal study

SummaryHearing loss is not unique to humans and is experienced by all animals in the face of wild and eclectic differences in ear morphology. Here, we exploited the high throughput and accessible tympanal ear of the desert locust, Schistocerca gregaria to rigorously quantify changes in the auditory system due to noise exposure and age. In this exploratory study, we analyzed tympanal displacements, morphology of the auditory Müller’s organ and measured activity of the auditory nerve, the transduction current, and electrophysiological properties of individual auditory receptors. This work shows that hearing loss manifests as a complex disorder due to differential effects of age and noise on several processes and cell types within the ear. The “middle-aged deafness” pattern of hearing loss found in locusts mirrors that found for humans exposed to noise early in their life suggesting a fundamental interaction of the use of an auditory system (noise) and its aging.

Regeneration in the Auditory Organ in Cuban and African Dwarf Crocodiles (Crocodylus rhombifer and Osteolaemus tetraspis) Can We Learn From the Crocodile How to Restore Our Hearing?

Background: In several non-mammalian species, auditory receptors undergo cell renewal after damage. This has raised hope of finding new options to treat human sensorineural deafness. Uncertainty remains as to the triggering mechanisms and whether hair cells are regenerated even under normal conditions. In the present investigation, we explored the auditory organ in the crocodile to validate possible ongoing natural hair cell regeneration. Materials and Methods: Two male Cuban crocodiles (Crocodylus rhombifer) and an adult male African Dwarf crocodile (Osteolaemus tetraspis) were analyzed using transmission electron microscopy and immunohistochemistry using confocal microscopy. The crocodile ears were fixed in formaldehyde and glutaraldehyde and underwent micro-computed tomography (micro-CT) and 3D reconstruction. The temporal bones were drilled out and decalcified. Results: The crocodile papilla basilaris contained tall (inner) and short (outer) hair cells surrounded by a mosaic of tightly connected supporting cells coupled with gap junctions. Afferent neurons with and without ribbon synapses innervated both hair cell types. Supporting cells occasionally showed signs of trans-differentiation into hair cells. They expressed the MAFA and SOX2 transcription factors. Supporting cells contained organelles that may transfer genetic information between cells, including the efferent nerve fibers during the regeneration process. The tectorial membrane showed signs of being replenished and its architecture being sculpted by extracellular exosome-like proteolysis. Discussion: Crocodilians seem to produce new hair cells during their life span from a range of supporting cells. Imposing efferent nerve fibers may play a role in regeneration and re-innervation of the auditory receptors, possibly triggered by apoptotic signals from wasted hair cells. Intercellular signaling may be accomplished by elaborate gap junction and organelle systems, including neural emperipolesis. Crocodilians seem to restore and sculpt their tectorial membranes throughout their lives.

Auditory mechanics in the grig ( Cyphoderris monstrosa ): tympanal travelling waves and frequency discrimination as a precursor to inner ear tonotopy

Ensiferan orthopterans offer a key study system for acoustic communication and the process of insect hearing. Cyphoderris monstrosa (Hagloidea) belongs to a relict ensiferan family and is often used for evolutionary comparisons between bushcrickets (Tettigoniidae) and their ancestors. Understanding how this species processes sound is therefore vital to reconstructing the evolutionary history of ensiferan hearing. Previous investigations have found a mismatch in the ear of this species, whereby neurophysiological and tympanal tuning does not match the conspecific communication frequency. However, the role of the whole tympanum in signal reception remains unknown. Using laser Doppler vibrometry, we show that the tympana are tonotopic, with higher frequencies being received more distally. The tympana use two key modalities to mechanically separate sounds into two auditory receptor populations. Frequencies below approximately 8 kHz generate a basic resonant mode in the proximal end of the tympanum, whereas frequencies above approximately 8 kHz generate travelling waves in the distal region. Micro-CT imaging of the ear and the presented data suggest that this tonotopy of the tympana drive the tonotopic mechanotransduction of the crista acustica (CA). This mechanism represents a functional intermediate between simple tuned tympana and the complex tonotopy of the bushcricket CA.

Clinical Evaluation of Balance in Children With Hemophilic Arthropathy.

Hemophilia is a hereditary coagulation disorder characterized by acute hemorrhages into the musculoskeletal system, leading eventually to arthropathy and disability. Chronic inflammation of the synovial membrane arises as a result of frequent joint hemorrhage. Proteolytic enzymes in the blood and cartilage cause deterioration after that, and joint space narrows. Chronic hemophilic arthropathy develops as a result of these unfavorable developments, which occur more quickly, especially in the target joints. Balance is a process that allows us to maintain our orientation in three-dimensional space while also regulating our body posture to avoid falling. After the central nervous system evaluates deep stimuli from sensory, visual, and auditory receptors, movement of the corresponding muscle groups is delivered. The goal of this study was to investigate how impairment to deep sensory receptors (proprioception) in the arthropathic joint structure affected hemophiliacs' balance. The study comprised 34 patients with hemophilic arthropathy, and 34 age and weight matched healthy volunteers. When balance tests of patients with hemophilic arthropathy were compared to healthy controls, hemophiliacs had a greater risk of falling. As the degree of arthropathy increased, so did the risk of falling and balance test values in individuals with hemophilic arthropathy. Treatment and coagulation factor prophylaxis to prevent the onset of arthropathy will improve patients' quality of life and reduce morbidity associated with frequent falls and bleeding. The online version contains supplementary material available at 10.1007/s12288-022-01526-0.

RESULTS OF AUDIOLOGICAL EXAMINATION IN ACUTE SENSORINEURAL HEARING LOSS OF VARIOUS GENESIS

This article provides an audiological description of acute sensorineural hearing loss of various genesis. One of the main problems of modern clinical audiology is hearing loss, which is a process of conversion of mechanical vibrations into energy of nerve impulses for one reason or another and subsequent damage to the auditory apparatus when the transmission from auditory receptors to the appropriate centers of the cerebral cortex is disrupted. Numerous publications in the world and local literature indicate that sensorineural hearing loss is common and very common among ENT organ diseases. According to the World Health Organization, by 2016, the number of people with socially significant hearing impairments will range from 0.6% to 20%, particularly in Russia, where the number of such patients is approaching 13 million, of whom 750,000 are children, and in Europe, sensorineural hearing loss. accounts for 37.2% of auditory pathology.

A Review on Puerulus (Panulirus spp.) Resource Utilization in Indonesia Based on the Sense of Hearing: Auditory Receptor Organs

Highlight ResearchThe mortality of lobster seeds by predators in the first year is 96.0-99.4%It takes technology to catch seeds before being eaten by predatorsApplication of sound wave-based attractor technology to lobstersDo lobsters have the ability to hear sound waves?The lobster's sense of hearing begins to function from the puerulus stage AbstractIndonesia is a country that produces abundant lobster seeds (puerulus), however, there is a paradox, where natural mortality in the first year since entering the settlement phase can reach 96.0-99.4%. The use of lobster resources, especially in the puerulus stage, for cultivation, is very strategic. Therefore, it is necessary to improve puerulus fishing technology. In the capture fisheries sector, the use of the sense of hearing in fish resources has been carried out to increase catch productivity, by utilizing sound wave-based attractors’ technology. For lobster resources, to what extent is this technology applicable? Underwater sound waves are a phenomenon of compression and expansion of a medium as sound energy passes through it. This aspect of the study is still new and very prospective. The purpose of this review article is to answer some basic questions: Can lobsters be able to hear sounds that come from their surroundings, since when do lobsters sense of hearing begin to function, and anatomically what kind of auditory organs are in lobsters. The results of the review conclude as follows: lobsters have senses that are able to perceive or listen to sound waves (sound) from their surrounding environment, this ability has been possessed by lobsters since they were in the postlarva or puerulus stage. Anatomically, the organs that act as the sense of hearing in lobsters are: receptors on the body surface, chordotonal organs and statocyst organs.

Functions of Chordotonal Sensilla in Bushcrickets (Orthoptera, Tettigoniidae)

Acoustic and vibrational sensitivity of single identified auditory receptors in bushcrickets was studied by electrophysiological methods. In the intermediate organ, some neurons were identified whose response to acceleration did not depend on the stimulus frequency over a significant frequency range; along with them, there were cells showing increased sensitivity to frequencies of 0.4–0.8 kHz for displacement, and/or 0.1–0.3, 1–1.2, and 1.4–3 kHz for all the vibration parameters. In addition, most of the studied receptors had a zone of increased sensitivity to highfrequency vibrations at 1.5–2.5 kHz. In the sensilla of the crista acustica, increased sensitivity was recorded at frequencies of 0.1–0.3, 0.4–0.8, 1–1.2, and 1.4–2.5 kHz. The best frequencies of a single sensillum may lie in different frequency ranges for different vibration parameters. Such differences in sensitivity to vibration acceleration, vibration velocity, and displacement, and also the different best frequencies in the receptors of the intermediate organ and the crista acustica were probably determined by differences in size, position, and morphological details of the sensilla, their own resonances, and reactions to resonance vibrations of the trachea section bearing the vibroreceptors. Thus, the chordotonal sensillum is a bifunctional mechanoreceptor which, along with auditory sensitivity, can combine the functions of both a displacement receiver and an accelerometer due to the different mechanical properties of its cells and the surrounding structures.

An in vitro model to assess the peripheral vestibulotoxicity of aromatic solvents

Epidemiological and experimental studies indicate that a number of aromatic solvents widely used in the industry can affect hearing and balance following chronic exposure. Animal studies demonstrated that long-term exposure to aromatic solvents directly damages the auditory receptor within the inner ear: the cochlea. However, no information is available on their effect on the vestibular receptor, which shares many structural features with the cochlea and is also localized in inner ear. The aim of this study was to use an in vitro approach to assess and compare the vestibular toxicity of different aromatic solvents (toluene, ethylbenzene, styrene and ortho-, meta-, para-xylene), all of which have well known cochleotoxic properties. We used a three-dimensional culture model of rat utricles (“cysts”) with preserved functional sensory and secretory epithelia, and containing a potassium-rich (K+) endolymph-like fluid for this study. Variations in K+ concentrations in this model were considered as biomarkers of toxicity of the substances tested. After 72 h exposure, o-xylene, ethylbenzene and styrene decreased the K+ concentration by 78 %, 37 % and 28 %, respectively. O- xylene and styrene both caused histopathological alterations in secretory and sensory epithelial areas after 72 h exposure, whereas no anomalies were observed in ethylbenzene-exposed samples.These in vitro results suggest that some widely used aromatic solvents might have vestibulotoxic properties (o-xylene, styrene and ethylbenzene), whereas others may not (p-xylene, m-xylene, toluene). Our results also indicate that variations in endolymphatic K+ concentration may be a more sensitive marker of vestibular toxicity than histopathological events. Finally, this study suggests that cochleotoxic solvents might not be necessarily vestibulotoxic, and vice versa.

The Pathology of the Vestibular System in CANVAS.

To describe the site of lesion responsible for the severe, bilateral, symmetrical, selective loss of vestibular function in Cerebellar Ataxia with Neuronopathy and Vestibular Areflexia Syndrome (CANVAS), an adult-onset recessively-inherited ataxia, characterized by progressive imbalance due to a combination of cerebellar, somatosensory, and selective vestibular impairment with normal hearing. Histologic examination of five temporal bones and the brainstems from four CANVAS patients and the brainstem only from one more, each diagnosed and followed from diagnosis to death by one of the clinician authors. All five temporal bones showed severe loss of vestibular ganglion cells (cell counts 3-16% of normal), and atrophy of the vestibular nerves, whereas vestibular receptor hair cells and the vestibular nuclei were preserved. In contrast, auditory receptor hair cells, the auditory ganglia (cell counts 51-100% of normal), and the auditory nerves were relatively preserved. In addition, the cranial sensory ganglia (geniculate and trigeminal), present in two temporal bones, also showed severe degeneration. In CANVAS there is a severe cranial sensory ganglionopathy neuronopathy (ganglionopathy) involving the vestibular, facial, and trigeminal ganglia but sparing the auditory ganglia. These observations, when coupled with the known spinal dorsal root ganglionopathy in CANVAS, indicate a shared pathogenesis of its somatosensory and cranial nerve manifestations. This is the first published account of both the otopathology and neuropathology of CANVAS, a disease that involves the central as well as the peripheral nervous system.

Speech intelligibility enhancement in elderly with high-frequency hearing loss through visual speech perception

Background: Pathological and physiological disabilities of human auditory receptors reduce speech intelligibility under hearing loss (HL) at high frequencies. Objectives: The objective of the study is to investigate the speech-intelligibility-enhancement (SIE) in elderly with high-frequency HL (HFHL) through visual-speech-perception (VSP). The hypothesis is that the VSP of spondee words (two-syllable words with equal stress on both syllables) is properly recognized and reproduced with HFHL. Also; to decide the statistical relevance of the precise significant difference in speech discrimination (SD) with VSP on the subjected ear. Methods: Observational and descriptive studies of SIE with VSP on 12 elderly listeners (24 clear ears; without wax impaction) with progressive and bilateral HFHL were examined. The entire experimental records were checked for distribution with normal (Gaussian) using the Shapiro–Wilk's and paired Student's t-test (parametric test) had the 5% (0.05) significance level (α). Results: We analyzed, improved, and better performance in SIE with HFHL through VSP. The statistical P (probability) measure was calculated nothing, i.e., 0 (P

A Possible Way to Improve the Quality of Speech Perception by Increasing the Number of Electrodes in a Cochlear Implant from 8 to 22

A cochlear implant (CI) helps a person with auditory receptor pathology restore the ability to hear and understand speech. The partial loss of the information about the frequency and loudness of the audio signal is the main difference from the natural sound perception. CIs of various types differ in the number of stimulated electrodes: 12, 16, 20, or 22. The quality of speech perception is significantly improved by increasing the number of stimulated electrodes from 4 to 7 and almost does not change with a further increase in the number of electrodes from 8 to 22. When speech is perceived in all types of CI, 3 to 6 adjacent electrodes are usually stimulated simultaneously. When a single electrode is stimulated, the CI user hears a sound with a single pitch. When two adjacent electrodes E(n) and E(n+1) are simultaneously stimulated, a virtual frequency channel (VFC) is formed, and the CI user hears a sound with an intermediate pitch {Z(n)+Z(n+1)}/2, provided that the adjacent electrodes on the right and left are not stimulated. When three or more adjacent electrodes are simultaneously stimulated, the CI user hears a sound with the same pitch, which depends on the distance from the electrode with the largest amplitude of stimulating pulses to the apex of the cochlea. There was no suggestion as to why the quality of speech perception does not improve when the number of electrodes increases from 8 to 22 in the scientific literature for the period from 1997 to 2019. This article proposes a method for adjusting the mode electrodes stimulation, which creates conditions for the formation of virtual frequency channels. The CI user will be able to hear a greater number of sounds of various pitch. A method for correcting the algorithm for controlling the stimulation of electrodes, which can be used in any type of CI, is proposed.

Oral Antioxidant Vitamins and Magnesium Limit Noise-Induced Hearing Loss by Promoting Sensory Hair Cell Survival: Role of Antioxidant Enzymes and Apoptosis Genes.

Noise induces oxidative stress in the cochlea followed by sensory cell death and hearing loss. The proof of principle that injections of antioxidant vitamins and Mg2+ prevent noise-induced hearing loss (NIHL) has been established. However, effectiveness of oral administration remains controversial and otoprotection mechanisms are unclear. Using auditory evoked potentials, quantitative PCR, and immunocytochemistry, we explored effects of oral administration of vitamins A, C, E, and Mg2+ (ACEMg) on auditory function and sensory cell survival following NIHL in rats. Oral ACEMg reduced auditory thresholds shifts after NIHL. Improved auditory function correlated with increased survival of sensory outer hair cells. In parallel, oral ACEMg modulated the expression timeline of antioxidant enzymes in the cochlea after NIHL. There was increased expression of glutathione peroxidase-1 and catalase at 1 and 10 days, respectively. Also, pro-apoptotic caspase-3 and Bax levels were diminished in ACEMg-treated rats, at 10 and 30 days, respectively, following noise overstimulation, whereas, at day 10 after noise exposure, the levels of anti-apoptotic Bcl-2, were significantly increased. Therefore, oral ACEMg improves auditory function by limiting sensory hair cell death in the auditory receptor following NIHL. Regulation of the expression of antioxidant enzymes and apoptosis-related proteins in cochlear structures is involved in such an otoprotective mechanism.