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.

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.

Innervation of the Cochlea of the Guinea Pig by Use of the Golgi Stain

1975 ◽  
Vol 84 (4) ◽  
pp. 443-458 ◽  
Author(s):  
Catherine A. Smith
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Guinea Pigs ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Single Row ◽  
Golgi Stain ◽  
Branching Patterns

Nerve fibers with distinctive branching patterns have been demonstrated in guinea pigs by use of the Golgi stain. The cochlear nerve fibers in the basal turn tend to supply a limited segment of the basilar membrane and have most endings on a single row of hair cells. The efferent olivocochlear nerve fibers ramify in a manner which varies from base to apex. Some efferents which terminate on outer hair cells also give branches which course in the inner spiral bundle. Other nerve fibers were studied in the spiral lamina which did not penetrate into the organ of Corti.

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.

Study of MFM Application in Semiconductor Failure Analysis

2004 ◽  
Author(s):  
Way-Jam Chen ◽  
Lily Shiau ◽  
Ming-Ching Huang ◽  
Chia-Hsing Chao
Keyword(s):  
Magnetic Field ◽  
Failure Analysis ◽  
Magnetic Force Microscopy ◽  
Magnetic Force ◽  
Current Flow ◽  
Force Microscopy ◽  
The Magnetic Field ◽  
A Current

Abstract In this study we have investigated the magnetic field associated with a current flowing in a circuit using Magnetic Force Microscopy (MFM). The technique is able to identify the magnetic field associated with a current flow and has potential for failure analysis.

Low frequency electromagnetic radiation and hearing

2009 ◽  
Vol 123 (11) ◽  
pp. 1204-1211 ◽  
Author(s):  
J Morales ◽  
M Garcia ◽  
C Perez ◽  
J V Valverde ◽  
C Lopez-Sanchez ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Electromagnetic Fields ◽  
Control Animal ◽  
Guinea Pigs ◽  
Low Frequency ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Morphological Alteration ◽  
Electric Response ◽  
Hearing Level

AbstractObjective:To analyse the possible impact of low and extremely low frequency electromagnetic fields on the outer hairs cells of the organ of Corti, in a guinea pig model.Materials and methods:Electromagnetic fields of 50, 500, 1000, 2000, 4000 and 5000 Hz frequencies and 1.5 µT intensity were generated using a transverse electromagnetic wave guide. Guinea pigs of both sexes, weighing 100–150 g, were used, with no abnormalities on general and otic examination. Total exposure times were: 360 hours for 50, 500 and 1000 Hz; 3300 hours for 2000 Hz; 4820 hours for 4000 Hz; and 6420 hours for 5000 Hz. One control animal was used in each frequency group. The parameters measured by electric response audiometer included: hearing level; waves I–IV latencies; wave I–III interpeak latency; and percentage appearance of waves I–III at 90 and 50 dB sound pressure level intensity.Results:Values for the above parameters did not differ significantly, comparing the control animal and the rest of each group. In addition, no significant differences were found between our findings and those of previous studies of normal guinea pigs.Conclusion:Prolonged exposure to electromagnetic fields of 50 Hz to 5 KHz frequencies and 1.5 µT intensity, produced no functional or morphological alteration in the outer hair cells of the guinea pig organ of Corti.

Stiffness of the Gerbil Basilar Membrane: Radial and Longitudinal Variations

2004 ◽  
Vol 91 (1) ◽  
pp. 474-488 ◽  
Author(s):  
Gulam Emadi ◽  
Claus-Peter Richter ◽  
Peter Dallos
Keyword(s):  
Cross Section ◽  
Basilar Membrane ◽  
Organ Of Corti ◽  
Sound Waves ◽  
Motion Patterns ◽  
Longitudinal Stiffness ◽  
Longitudinal Variations ◽  
Space Constant ◽  
Qualitative Changes

Experimental data on the mechanical properties of the tissues of the mammalian cochlea are essential for understanding the frequency- and location-dependent motion patterns that result in response to incoming sound waves. Within the cochlea, sound-induced vibrations are transduced into neural activity by the organ of Corti, the gross motion of which is dependent on the motion of the underlying basilar membrane. In this study we present data on stiffness of the gerbil basilar membrane measured at multiple positions within a cochlear cross section and at multiple locations along the length of the cochlea. A basic analysis of these data using relatively simple models of cochlear mechanics reveals our most important result: the experimentally measured longitudinal stiffness gradient at the middle of the pectinate zone of the basilar membrane (4.43 dB/mm) can account for changes of best frequency along the length of the cochlea. Furthermore, our results indicate qualitative changes of stiffness-deflection curves as a function of radial position; in particular, there are differences in the rate of stiffness growth with increasing tissue deflection. Longitudinal coupling within the basilar membrane/organ of Corti complex is determined to have a space constant of 21 μm in the middle turn of the cochlea. The bulk of our data was obtained in the hemicochlea preparation, and we include a comparison of this set of data to data obtained in vivo.

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