scholarly journals Amplification lags nonlinearity in the recovery from reduced endocochlear potential

2020 ◽  
Author(s):  
C. Elliott Strimbu ◽  
Yi Wang ◽  
Elizabeth S. Olson
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Basilar Membrane ◽  
Frequency Tuning ◽  
Organ Of Corti ◽  
Endocochlear Potential ◽  
Outer Hair Cells ◽  
Frequency Resolution ◽  
Operating Condition ◽  
Distortion Product

ABSTRACTThe mammalian hearing organ, the cochlea, contains an active amplifier to boost the vibrational response to low level sounds. Hallmarks of this active process are sharp location-dependent frequency tuning and compressive nonlinearity over a wide stimulus range. The amplifier relies on outer hair cell (OHC) generated forces driven in part by the endocochlear potential (EP), the ~ +80 mV potential maintained in scala media, generated by the stria vascularis. We transiently eliminated the EP in vivo by an intravenous injection of furosemide and measured the vibrations of different layers in the cochlea’s organ of Corti using optical coherence tomography. Distortion product otoacoustic emissions (DPOAE) were monitored at the same times. Following the injection, the vibrations of the basilar membrane lost the best frequency (BF) peak and showed broad tuning similar to a passive cochlea. The intra-organ of Corti vibrations measured in the region of the OHCs lost their BF peak and showed low-pass responses, but retained nonlinearity, indicating that OHC electromotility was still operational. Thus, while electromotility is presumably necessary for amplification, its presence is not sufficient for amplification. The BF peak recovered nearly fully within 2 hours, along with a non-monotonic DPOAE recovery that suggests that physical shifts in operating condition are a final step in the recovery process.SIGNIFICANCEThe endocochlear potential, the +80 mV potential difference across the fluid filled compartments of the cochlea, is essential for normal mechanoelectrical transduction, which leads to receptor potentials in the sensory hair cells when they vibrate in response to sound. Intracochlear vibrations are boosted tremendously by an active nonlinear feedback process that endows the cochlea with its healthy sensitivity and frequency resolution. When the endocochlear potential was reduced by an injection of furosemide, the basilar membrane vibrations resembled those of a passive cochlea, with broad tuning and linear scaling. The vibrations in the region of the outer hair cells also lost the tuned peak, but retained nonlinearity at frequencies below the peak, and these sub-BF responses recovered fairly rapidly. Vibration responses at the peak recovered nearly fully over 2 hours. The staged vibration recovery and a similarly staged DPOAE recovery suggests that physical shifts in operating condition are a final step in the process of cochlear recovery.

scholarly journals Vanilloid Receptors in Hearing: Altered Cochlear Sensitivity by Vanilloids and Expression of TRPV1 in the Organ of Corti

2003 ◽  
Vol 90 (1) ◽  
pp. 444-455 ◽  
Author(s):  
Jiefu Zheng ◽  
Chunfu Dai ◽  
Peter S. Steyger ◽  
Youngki Kim ◽  
Zoltan Vass ◽  
...  
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Transient Receptor Potential ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Receptor Potential ◽  
Compound Action Potential ◽  
Outer Hair Cells ◽  
Vanilloid Receptors ◽  
Cochlear Blood Flow

Capsaicin, the vanilloid that selectively activates vanilloid receptors (VRs) on sensory neurons for noxious perception, has been reported to increase cochlear blood flow (CBF). VR-related receptors have also been found in the inner ear. This study aims to address the question as to whether VRs exist in the organ of Corti and play a role in cochlear physiology. Capsaicin or the more potent VR agonist, resiniferatoxin (RTX), was infused into the scala tympani of guinea pig cochlea, and their effects on cochlear sensitivity were investigated. Capsaicin (20 μM) elevated the threshold of auditory nerve compound action potential and reduced the magnitude of cochlear microphonic and electrically evoked otoacoustic emissions. These effects were reversible and could be blocked by a competitive antagonist, capsazepine. Application of 2 μM RTX resulted in cochlear sensitivity alterations similar to that by capsaicin, which could also be blocked by capsazepine. A desensitization phenomenon was observed in the case of prolonged perfusion with either capsaicin or RTX. Brief increase of CBF by capsaicin was confirmed, and the endocochlear potential was not decreased. Basilar membrane velocity (BM) growth functions near the best frequency and BM tuning were altered by capsaicin. Immunohistochemistry study revealed the presence of vanilloid receptor type 1 of the transient receptor potential channel family in the hair cells and supporting cells of the organ of Corti and the spiral ganglion cells of the cochlea. The results indicate that the main action of capsaicin is on outer hair cells and suggest that VRs in the cochlea play a role in cochlear homeostasis.

Otoacoustic Emissions as a Promising Diagnostic Tool for the Early Detection of Mild Hearing Impairment - Technical Advances in Acquisition, Analysis and Modeling

2016 ◽  
Vol 879 ◽  
pp. 2355-2360
Author(s):  
Arturo Moleti ◽  
Renata Sisto ◽  
Filippo Sanjust ◽  
Teresa Botti ◽  
Sandro Gentili
Keyword(s):  
Diagnostic Tool ◽  
Otoacoustic Emissions ◽  
Basilar Membrane ◽  
Hearing Threshold ◽  
High Sensitivity ◽  
Outer Hair Cells ◽  
Frequency Resolution ◽  
Phase Gradient ◽  
Time Frequency ◽  
Generation Mechanisms

Otoacoustic emissions are a by-product of the active nonlinear amplification mechanism located in the cochlear outer hair cells, which provides high sensitivity and frequency resolution to human hearing. Being intrinsically sensitive to hearing loss at a cochlear level, they represent a promising non-invasive, fast, and objective diagnostic tool. On the other hand, the complexity of their linear and nonlinear generation mechanisms and other confounding physical phenomena (e.g., interference between different otoacoustic components, acoustical resonances in the ear canal, transmission of the middle ear) introduce a large inter-subject variability in their measured levels, which makes it difficult using them as a direct measure of the hearing threshold using commercially available devices. Nonlinear cochlear modeling has been successfully used to understand the complexity of the otoacoustic generation mechanisms, and to design new acquisition and analysis techniques that help disentangling the different components of the otoacoustic response, therefore improving the correlation between measured otoacoustic levels and audiometric thresholds. In particular, nonlinear cochlear modeling was able to effectively describe the complex (amplitude and phase) response of the basilar membrane, and the generation of otoacoustic emissions by two mechanisms, nonlinear distortion and linear reflection by cochlear roughness. Different phase-frequency relations are predicted for the otoacoustic components generated by the two mechanisms, so they can be effectively separated according to their different phase-gradient delay, using an innovative time-frequency domain filtering technique based on the wavelet transform. A brief introduction to these topics and some new theoretical and experimental results are presented and discussed in this study.

scholarly journals The Role of Prestin in the Generation of Electrically Evoked Otoacoustic Emissions in Mice

2008 ◽  
Vol 99 (4) ◽  
pp. 1607-1615 ◽  
Author(s):  
Markus Drexl ◽  
Marcia M. Mellado Lagarde ◽  
Jian Zuo ◽  
Andrei N. Lukashkin ◽  
Ian J. Russell
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Temporal Structure ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Wild Type ◽  
Short Delay ◽  
Delay Component

Electrically evoked otoacoustic emissions are sounds emitted from the inner ear when alternating current is injected into the cochlea. Their temporal structure consists of short- and long-delay components and they have been attributed to the motile responses of the sensory-motor outer hair cells of the cochlea. The nature of these motile responses is unresolved and may depend on either somatic motility, hair bundle motility, or both. The short-delay component persists after almost complete elimination of outer hair cells. Outer hair cells are thus not the sole generators of electrically evoked otoacoustic emissions. We used prestin knockout mice, in which the motor protein prestin is absent from the lateral walls of outer hair cells, and Tecta ΔENT/ΔENT mice, in which the tectorial membrane, a structure with which the hair bundles of outer hair cells normally interact, is vestigial and completely detached from the organ of Corti. The amplitudes and delay spectra of electrically evoked otoacoustic emissions from Tecta ΔENT/ΔENT and Tecta +/+ mice are very similar. In comparison with prestin +/+ mice, however, the short-delay component of the emission in prestin −/− mice is dramatically reduced and the long-delay component is completely absent. Emissions are completely suppressed in wild-type and Tecta ΔENT/ΔENT mice at low stimulus levels, when prestin-based motility is blocked by salicylate. We conclude that near threshold, the emissions are generated by prestin-based somatic motility.

scholarly journals Morphometry of the chinchilla organ of Corti and stria vascularis.

1979 ◽  
Vol 27 (11) ◽  
pp. 1539-1542 ◽  
Author(s):  
P A Santi ◽  
D C Muchow
Keyword(s):  
Morphometric Analysis ◽  
Hair Cells ◽  
Basilar Membrane ◽  
Stria Vascularis ◽  
Organ Of Corti ◽  
Outer Hair Cells

This research describes a procedure for a morphometric analysis of the organ of Corti and stria vascularis in the chinchilla. In nine normal cochleae the length of the basilar membrane and the stria vascularis measured 18.47 and 25.22 mm, respectively. An average of 1910 inner and 7501 outer hair cells were present while an average of 15 inner and 90 outer hair cells were absent. In all cochleae examined there were always some missing hair cells in varying numbers even though the animals had no known ototoxic exposure. Stria area, width and thickness increased from the cochlear apex toward the base. Consistency of changes in stria dimensions among animals was enhanced by expressing position in terms of percentage stria length rather than distance as such. Total stria volume was estimated at 0.15 microliter.

scholarly journals All Three Rows of Outer Hair Cells Are Required for Cochlear Amplification

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Michio Murakoshi ◽  
Sho Suzuki ◽  
Hiroshi Wada
Keyword(s):  
Hair Cells ◽  
Noise Exposure ◽  
Dynamic Range ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
High Sensitivity ◽  
Element Model ◽  
Outer Hair Cells ◽  
Displacement Amplitude ◽  
Cochlear Amplification

In the mammalian auditory system, the three rows of outer hair cells (OHCs) located in the cochlea are thought to increase the displacement amplitude of the organ of Corti. This cochlear amplification is thought to contribute to the high sensitivity, wide dynamic range, and sharp frequency selectivity of the hearing system. Recent studies have shown that traumatic stimuli, such as noise exposure and ototoxic acid, cause functional loss of OHCs in one, two, or all three rows. However, the degree of decrease in cochlear amplification caused by such functional losses remains unclear. In the present study, a finite element model of a cross section of the gerbil cochlea was constructed. Then, to determine effects of the functional losses of OHCs on the cochlear amplification, changes in the displacement amplitude of the basilar membrane (BM) due to the functional losses of OHCs were calculated. Results showed that the displacement amplitude of the BM decreases significantly when a single row of OHCs lost its function, suggesting that all three rows of OHCs are required for cochlear amplification.

scholarly journals Estimation of outer hair cells function in chronic bilateral tinnitus patients with normal hearing using distortion product otoacoustic emissions

2021 ◽  
Author(s):  
Aras Karimiani ◽  
Nematollah Rouhbakhsh ◽  
Farzaneh Zamiri Abdollahi ◽  
Shohreh Jalaie
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Normal Hearing ◽  
Outer Hair Cells ◽  
Distortion Product Otoacoustic Emissions ◽  
Control Group ◽  
Distortion Product Otoacoustic Emission ◽  
Frequency Range ◽  
Cochlear Function ◽  
Distortion Product

Background and Aim: It is not clear if the measurement of distortion product otoacoustic emissions (DPOAE) at frequencies above 8 kHz adds any value in determining the differences in the cochlear function between patients with and without tinnitus. This study aimed to compare DPOAE in the frequency range of 0.5−10 kHz in patients with normal hearing with and without tinnitus. Methods: This comparative cross-sectional study was conducted on 20 individuals with tinnitus and normal hearing as a study group (SG) and a control group (CG) of 20 normal-hearing individuals without tinnitus. The DPOAE was measured with F1/F2 = 1.22 and intensities of F1 = 65 dB SPL and F2 =55 dB SPL in the frequency range of 0.5−10 kHz, moreover in the frequency of tinnitus in SG and corresponding frequency in CG. Results: DPOAE level at 10 kHz did not differ significantly between SG and CG (p = 0.491). However, the mean of overall DPOAE level, DPOAE level at the frequency of tinnitus, and F2 values of 2.5, 5, and 6.298 kHz were significantly lower in SG than CG (p < 0.05). Conclusion: Measurement of DPOAE at 10 kHz did not seem to add any value in determining the differences in the cochlear function between patients with and without tinnitus. However, decreased DPOAE levels at 2.5, 5, and 6.298 kHz which were observed among patients who have tinnitus and normal hearing, indicates some outer hair cells damage that was not detectable by conventional audiometry. Keywords: Tinnitus; normal hearing; outer hair cell; distortion product otoacoustic emission

scholarly journals THE STUDY OF MATURATION OF THE AUDITORY ANALYZER RABBIT ACCORDING DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS

2013 ◽  
Vol 68 (11) ◽  
pp. 94-97
Author(s):  
I. N. D'yakonova ◽  
Yu. S. Ishanova ◽  
I. V. Rakhmanova
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Normative Data ◽  
Outer Hair Cell ◽  
Rabbit Model ◽  
Outer Hair Cells ◽  
Distortion Product Otoacoustic Emissions ◽  
Acoustic Response ◽  
Auditory Analyzer ◽  
Distortion Product

Aim: In our chronic experiment to  register changes of acoustic response of Distortion-Product Otoacoustic Emissions (DPOAE) of intact rabbits in postnatal ontogenesis for the purpose of getting normative data which can be used for studying impact of pathological factors on auditory function and maturation of activity of outer hair cell in ontogenesis. Materials and methods: Study of otoacoustic emissions used mature chinchilla rabbits with a 19 day life of up to 3 months. Results: in the course of ripening were obtained functional activity of outer hair cells of the cochlea. Conclusion: normative data obtained allow us to study using a rabbit model, the pathological effects of agents on the maturation of the outer hair cells of the cochlea in the experiment.

scholarly journals Distinct roles of stereociliary links in the nonlinear sound processing and noise resistance of cochlear outer hair cells

2020 ◽  
Vol 117 (20) ◽  
pp. 11109-11117
Author(s):  
Woongsu Han ◽  
Jeong-Oh Shin ◽  
Ji-Hyun Ma ◽  
Hyehyun Min ◽  
Jinsei Jung ◽  
...  
Keyword(s):  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Essential Role ◽  
High Sensitivity ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Sound Processing ◽  
Mechanoelectrical Transduction ◽  
Distortion Product ◽  
Membrane Attachment

Outer hair cells (OHCs) play an essential role in hearing by acting as a nonlinear amplifier which helps the cochlea detect sounds with high sensitivity and accuracy. This nonlinear sound processing generates distortion products, which can be measured as distortion-product otoacoustic emissions (DPOAEs). The OHC stereocilia that respond to sound vibrations are connected by three kinds of extracellular links: tip links that connect the taller stereocilia to shorter ones and convey force to the mechanoelectrical transduction channels, tectorial membrane-attachment crowns (TM-ACs) that connect the tallest stereocilia to one another and to the overlying TM, and horizontal top connectors (HTCs) that link adjacent stereocilia. While the tip links have been extensively studied, the roles that the other two types of links play in hearing are much less clear, largely because of a lack of suitable animal models. Here, while analyzing genetic combinations of tubby mice, we encountered models missing both HTCs and TM-ACs or HTCs alone. We found that the tubby mutation causes loss of both HTCs and TM-ACs due to a mislocalization of stereocilin, which results in OHC dysfunction leading to severe hearing loss. Intriguingly, the addition of the modifier allele modifier of tubby hearing 1 in tubby mice selectively rescues the TM-ACs but not the HTCs. Hearing is significantly rescued in these mice with robust DPOAE production, indicating an essential role of the TM-ACs but not the HTCs in normal OHC function. In contrast, the HTCs are required for the resistance of hearing to damage caused by noise stress.

Micromechanical Responses to Tones in the Auditory Fovea of the Greater Mustached Bat’s Cochlea

1999 ◽  
Vol 82 (2) ◽  
pp. 676-686 ◽  
Author(s):  
I. J. Russell ◽  
M. Kössl
Keyword(s):  
Otoacoustic Emissions ◽  
Basilar Membrane ◽  
Outer Hair Cells ◽  
Tectorial Membrane ◽  
Phase Lag ◽  
Insect Wing ◽  
Distortion Product ◽  
High Stimulus ◽  
Membrane Resonance ◽  
Echolocation Signal

An extended region of the greater mustached bat’s cochlea, the sparsely innervated (SI) zone, is located just basally to the frequency place of the dominant 61-kHz component of the echolocation signal (CF2). Anatomic adaptations in the SI zone are thought to provide the basis for cochlear resonance to the CF2 echoes and for the extremely sharp tuning throughout the auditory system that allows these bats to detect Doppler shifts in the echoes caused by insect wing beat. We measured basilar membrane (BM) displacements in the SI zone with a laser interferometer and recorded acoustic distortion products at the ear drum at frequencies represented in the SI zone. The basilar membrane in the SI region was tuned both to its characteristic frequency (62–72 kHz) and to the resonance frequency (61–62 kHz). With increasing stimulus levels, the displacement growth functions are compressive curves with initial slopes close to unity, and their properties are consistent with the mammalian cochlear amplifier working at high sound frequencies. The sharp basilar membrane resonance is associated with a phase lag of 180° and with a shift of the peak resonance to lower frequencies for high stimulus levels. Within the range of the resonance, the distortion product otoacoustic emissions, which have been attributed to the resonance of the tectorial membrane in the SI region, are associated with an abrupt phase change of 360°. It is proposed that a standing wave resonance of the tectorial membrane drives the BM in the SI region and that the outer hair cells enhance, fine tune, and control the resonance. In the SI region, cochlear micromechanics appear to be able to work in two different modes: a conventional traveling wave leads to shear displacement between basilar and tectorial membrane and to neuronal excitation for 62–70 kHz. In addition, the SI region responds to 61–62 kHz with a resonance based on standing waves and thus preprocesses signals which are represented more apically in the CF2 region of the cochlea.

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