Loud Sound-Induced Changes in Cochlear Mechanics

2002 ◽  
Vol 88 (5) ◽  
pp. 2341-2348 ◽  
Author(s):  
Anders Fridberger ◽  
Jiefu Zheng ◽  
Anand Parthasarathi ◽  
Tianying Ren ◽  
Alfred Nuttall
Keyword(s):  
Inner Ear ◽  
Time Course ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Compound Action Potential ◽  
Cochlear Microphonic ◽  
Cochlear Function ◽  
Loud Sound ◽  
Induced Changes ◽  
Membrane Vibrations

To investigate the inner ear response to intense sound and the mechanisms behind temporary threshold shifts, anesthetized guinea pigs were exposed to tones at 100–112 dB SPL. Basilar membrane vibration was measured using laser velocimetry, and the cochlear microphonic potential, compound action potential of the auditory nerve, and local electric AC potentials in the organ of Corti were used as additional indicators of cochlear function. After exposure to a 12-kHz intense tone, basilar membrane vibrations in response to probe tones at the characteristic frequency of the recording location (17 kHz) were transiently reduced. This reduction recovered over the course of 50 ms in most cases. Organ of Corti AC potentials were also reduced and recovered with a time course similar to the basilar membrane. When using a probe tone at either 1 or 4 kHz, organ of Corti AC potentials were unaffected by loud sound, indicating that transducer channels remained intact. In most experiments, both the basilar membrane and the cochlear microphonic response to the 12-kHz overstimulation was constant throughout the duration of the intense stimulus, despite a large loss of cochlear sensitivity. It is concluded that the reduction of basilar membrane velocity that followed loud sound was caused by changes in cochlear amplification and that the cochlear response to intense stimulation is determined by the passive mechanical properties of the inner ear structures.

scholarly journals Modelling the Generation of the Cochlear Microphonic

2021 ◽  
Author(s):  
◽  
Mohammad Ayat
Keyword(s):  
Otoacoustic Emissions ◽  
Basilar Membrane ◽  
Electrical Signal ◽  
Mechanical Activity ◽  
Cochlear Amplifier ◽  
Cochlear Microphonic ◽  
Cochlear Function ◽  
Phase Cancellation ◽  
Wide Range ◽  
Human Ear

<p>The human ear is a remarkable sensory organ. A normal healthy human ear is able to process sounds covering a wide range of frequencies and intensities, while distinguishing between different components of complex sounds such as a musical chord. In the last four decades, knowledge about the cochlea and the mechanisms involved in its operation has greatly increased, but many details about these mechanisms remain unresolved and disputed. The cochlea has a vulnerable structure. Consequently, measuring and monitoring its mechanical and electrical activities even with contemporary devices is very difficult. Modelling can be used to fill gaps between those measurements that are feasible and actual cochlear function. Modelling techniques can also help to simplify complex cochlear operation to a tractable and comprehensible level while still reproducing certain behaviours of interest. Modelling therefore can play an essential role in developing a better understanding of the cochlea. The Cochlear Microphonic (CM) is an electrical signal generated inside the cochlea in response to sound. This electrical signal reflects mechanical activity in the cochlea and the excitation processes involved in its generation. However, the difficulty of obtaining this signal and the simplicity of other methods such as otoacoustic emissions have discouraged the use of the cochlear microphonic as a tool for studying cochlear functions. In this thesis, amodel of the cochlea is presented which integrates bothmechanical and electrical aspects, enabling the interaction between them to be investigated. The resulting model is then used to observe the effect of the cochlear amplifier on the CM. The results indicate that while the cochlear amplifier significantly amplifies the basilar membrane displacement, the effect on the CM is less significant. Both of these indications agree with previous physiological findings. A novel modelling approach is used to investigate the tuning discrepancy between basilar membrane and CMtuning curves. The results suggest that this discrepancy is primarily due to transversal phase cancellation in the outer hair cell rather than longitudinal phase cancellation along the basilar membrane. In addition, the results of the model suggest that spontaneous cochlear microphonic should exist in the cochlea. The existence of this spontaneous electrical signal has not yet been reported.</p>

scholarly journals Modelling the Generation of the Cochlear Microphonic

2021 ◽  
Author(s):  
◽  
Mohammad Ayat
Keyword(s):  
Otoacoustic Emissions ◽  
Basilar Membrane ◽  
Electrical Signal ◽  
Mechanical Activity ◽  
Cochlear Amplifier ◽  
Cochlear Microphonic ◽  
Cochlear Function ◽  
Phase Cancellation ◽  
Wide Range ◽  
Human Ear

<p>The human ear is a remarkable sensory organ. A normal healthy human ear is able to process sounds covering a wide range of frequencies and intensities, while distinguishing between different components of complex sounds such as a musical chord. In the last four decades, knowledge about the cochlea and the mechanisms involved in its operation has greatly increased, but many details about these mechanisms remain unresolved and disputed. The cochlea has a vulnerable structure. Consequently, measuring and monitoring its mechanical and electrical activities even with contemporary devices is very difficult. Modelling can be used to fill gaps between those measurements that are feasible and actual cochlear function. Modelling techniques can also help to simplify complex cochlear operation to a tractable and comprehensible level while still reproducing certain behaviours of interest. Modelling therefore can play an essential role in developing a better understanding of the cochlea. The Cochlear Microphonic (CM) is an electrical signal generated inside the cochlea in response to sound. This electrical signal reflects mechanical activity in the cochlea and the excitation processes involved in its generation. However, the difficulty of obtaining this signal and the simplicity of other methods such as otoacoustic emissions have discouraged the use of the cochlear microphonic as a tool for studying cochlear functions. In this thesis, amodel of the cochlea is presented which integrates bothmechanical and electrical aspects, enabling the interaction between them to be investigated. The resulting model is then used to observe the effect of the cochlear amplifier on the CM. The results indicate that while the cochlear amplifier significantly amplifies the basilar membrane displacement, the effect on the CM is less significant. Both of these indications agree with previous physiological findings. A novel modelling approach is used to investigate the tuning discrepancy between basilar membrane and CMtuning curves. The results suggest that this discrepancy is primarily due to transversal phase cancellation in the outer hair cell rather than longitudinal phase cancellation along the basilar membrane. In addition, the results of the model suggest that spontaneous cochlear microphonic should exist in the cochlea. The existence of this spontaneous electrical signal has not yet been reported.</p>

Cochlear Potentials and Oxygen Associated with Hypoxia

1975 ◽  
Vol 84 (4) ◽  
pp. 499-512 ◽  
Author(s):  
Merle Lawrence ◽  
Alfred L. Nuttall ◽  
Paul A. Burgio
Keyword(s):  
Guinea Pig ◽  
Oxygen Concentration ◽  
Current Flow ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Cochlear Microphonic ◽  
Cochlear Potentials ◽  
Oxygen Sensitive ◽  
Endolymphatic Potential ◽  
A Current

In the guinea pig, during general hypoxia produced by shutoff of respiratory air, oxygen-sensitive microelectrodes detect a decrease in oxygen concentration in the fluids of the tunnel of Corti before detecting a decrease in scala media oxygen concentration. The present experiments were designed to measure the cochlear microphonic (CM) potential generated by the organ of Corti when vibrated by a microprobe on the basilar membrane along with the oxygen decline in both tunnel and scala media to see upon which source of oxygen CM is dependent. Because oxygen concentration in both areas can decrease considerably before CM is affected, the recovery following a brief period of hypoxia is a more accurate measure. Because CM starts a recovery before scala media oxygen, the positive endolymphatic potential (EP) was also measured to determine its role in the generation of CM. Our interpretation of the course of events is that CM is partially dependent upon oxygen supplied to the extracellular spaces of the organ of Corti by the spiral vessels and upon EP that, itself, is dependent upon several factors. The data indicate that EP plays a more complex role than that of providing a current flow for modulation by a resistance varying with vibration.

Influence of argon laser stapedotomy on inner ear function and temperature

1983 ◽  
Vol 91 (5) ◽  
pp. 521-526 ◽  
Author(s):  
Michael Vollrath ◽  
Christoph Schreiner
Keyword(s):  
Action Potential ◽  
Inner Ear ◽  
Guinea Pigs ◽  
Time Course ◽  
Argon Laser ◽  
Compound Action Potential ◽  
Clinical Use ◽  
Cochlear Microphonics ◽  
Temperature Changes ◽  
Compound Action

The influence of argon laser stapedotomy on inner ear function was investigated in guinea pigs. The cochlear microphonics (CM) and the compound action potential (CAP) served as parameters for the functional status of the cochlear. Transitory depression of both potentials was found during and after laser stapedotomy. The time course of CM and CAP depression and recovery is compared to endocochlear temperature changes. Possible implications for clinical use are discussed.

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.

Sensorineural Hearing Loss due to Cochlear Otospongiosis: Theoretical Considerations of Etiology

1975 ◽  
Vol 84 (4) ◽  
pp. 544-551 ◽  
Author(s):  
Fred H. Linthicum ◽  
Roberto Filipo ◽  
Sidney Brody
Keyword(s):  
Hearing Loss ◽  
Sensorineural Hearing Loss ◽  
Inner Ear ◽  
Basilar Membrane ◽  
Stria Vascularis ◽  
Organ Of Corti ◽  
Sensorineural Hearing ◽  
Toxic Substances ◽  
Theoretical Considerations

Several theories have been advanced to explain the sensorineural hearing loss that occurs in patients with otospongiosis: toxic substances produced by the otospongiotic focus; vascular shunts between the inner ear vessels and the otospongiotic focus; and atrophy of the organ of Corti and stria vascularis due to unknown causes. Presented here is yet another theory: impingement upon the cochlear walls by the otospongiotic focus, causing a narrowing of the lumen of the cochlea and distortion of the basilar membrane.

scholarly journals Mathematical modeling of the radial profile of basilar membrane vibrations in the inner ear

2004 ◽  
Vol 116 (2) ◽  
pp. 1025-1034 ◽  
Author(s):  
Martin Homer ◽  
Alan Champneys ◽  
Giles Hunt ◽  
Nigel Cooper
Keyword(s):  
Mathematical Modeling ◽  
Inner Ear ◽  
Basilar Membrane ◽  
Radial Profile ◽  
Membrane Vibrations

A technique for protecting delicate specimens during processing

1989 ◽  
Vol 47 ◽  
pp. 982-983
Author(s):  
R.J. Mount ◽  
R.V. Harrison
Keyword(s):  
Basilar Membrane ◽  
Low Cost ◽  
Organ Of Corti ◽  
Region Of Interest ◽  
Sensory Epithelium ◽  
Physical Damage ◽  
Air Drying ◽  
Specimen Handling ◽  
Two Component

The sensory end organ of the ear, the organ of Corti, rests on a thin basilar membrane which lies between the bone of the central modiolus and the bony wall of the cochlea. In vivo, the organ of Corti is protected by the bony wall which totally surrounds it. In order to examine the sensory epithelium by scanning electron microscopy it is necessary to dissect away the protective bone and expose the region of interest (Fig. 1). This leaves the fragile organ of Corti susceptible to physical damage during subsequent handling. In our laboratory cochlear specimens, after dissection, are routinely prepared by the O-T- O-T-O technique, critical point dried and then lightly sputter coated with gold. This processing involves considerable specimen handling including several hours on a rotator during which the organ of Corti is at risk of being physically damaged. The following procedure uses low cost, readily available materials to hold the specimen during processing ,preventing physical damage while allowing an unhindered exchange of fluids.Following fixation, the cochlea is dehydrated to 70% ethanol then dissected under ethanol to prevent air drying. The holder is prepared by punching a hole in the flexible snap cap of a Wheaton vial with a paper hole punch. A small amount of two component epoxy putty is well mixed then pushed through the hole in the cap. The putty on the inner cap is formed into a “cup” to hold the specimen (Fig. 2), the putty on the outside is smoothed into a “button” to give good attachment even when the cap is flexed during handling (Fig. 3). The cap is submerged in the 70% ethanol, the bone at the base of the cochlea is seated into the cup and the sides of the cup squeezed with forceps to grip it (Fig.4). Several types of epoxy putty have been tried, most are either soluble in ethanol to some degree or do not set in ethanol. The only putty we find successful is “DUROtm MASTERMENDtm Epoxy Extra Strength Ribbon” (Loctite Corp., Cleveland, Ohio), this is a blue and yellow ribbon which is kneaded to form a green putty, it is available at many hardware stores.

Amplitude Distributions of Cochlear Microphonic Response to an Acoustic Sinusoid in Noise

1968 ◽  
Vol 11 (1) ◽  
pp. 63-76
Author(s):  
Donald C. Teas ◽  
Gretchen B. Henry
Keyword(s):  
Small Amplitude ◽  
Basilar Membrane ◽  
Spectral Composition ◽  
Pass Band ◽  
Cochlear Microphonic ◽  
Filter Output ◽  
Electronic Filter ◽  
Low Pass ◽  
Band Pass ◽  
Instantaneous Voltage

The distributions of instantaneous voltage amplitudes in the cochlear microphonic response recorded from a small segment along the basilar membrane are described by computing amplitude histograms. Comparisons are made between the distributions for noise and for those after the addition to the noise of successively stronger sinusoids. The amplitudes of the cochlear microphonic response to 5000 Hz low-pass noise are normally distributed in both Turn I and Turn III of the guinea pig’s cochlea. The spectral composition of the microphonic from Turn I and from Turn III resembles the output of band-pass filters set at about 4000 Hz, and about 500 Hz, respectively. The normal distribution of cochlear microphonic amplitudes for noise is systematically altered by increasing the strength of the added sinusoid. A decrease of three percent in the number of small amplitude events (±1 standard deviation) in the cochlear microphonic from Turn III is seen when the rms voltage of a 500 Hz sinusoid is at −18 dB re the rms voltage of the noise (at the earphone). When the rms of the sinusoid and noise are equal, the decrease in small voltages is about 25%, but there is also an increase in the number of large voltage amplitudes. Histograms were also computed for the output of an electronic filter with a pass-band similar to Turn III of the cochlea. Strong 500 Hz sinusoids showed a greater proportion of large amplitudes in the filter output than in CM III . The data are interpreted in terms of an anatomical substrate.

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