scholarly journals Hydromechanical Structure of the Cochlea Supports the Backward Traveling Wave in the Cochlea In Vivo

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Fangyi Chen ◽  
Dingjun Zha ◽  
Xiaojie Yang ◽  
Allyn Hubbard ◽  
Alfred Nuttall
Keyword(s):  
Traveling Wave ◽  
Basilar Membrane ◽  
Wave Theory ◽  
Otoacoustic Emission ◽  
Traditional Theory ◽  
Vibration Source ◽  
Ear Canal ◽  
Local Vibration ◽  
Membrane Vibration

The discovery that an apparent forward-propagating otoacoustic emission (OAE) induced basilar membrane vibration has created a serious debate in the field of cochlear mechanics. The traditional theory predicts that OAE will propagate to the ear canal via a backward traveling wave on the basilar membrane, while the opponent theory proposed that the OAE will reach the ear canal via a compression wave. Although accepted by most people, the basic phenomenon of the backward traveling wave theory has not been experimentally demonstrated. In this study, for the first time, we showed the backward traveling wave by measuring the phase spectra of the basilar membrane vibration at multiple longitudinal locations of the basal turn of the cochlea. A local vibration source with a unique and precise location on the cochlear partition was created to avoid the ambiguity of the vibration source in most previous studies. We also measured the vibration pattern at different places of a mechanical cochlear model. A slow backward traveling wave pattern was demonstrated by the time-domain sequence of the measured data. In addition to the wave propagation study, a transmission line mathematical model was used to interpret why no tonotopicity was observed in the backward traveling wave.

Group Delay of Acoustic Emissions in the Ear

2006 ◽  
Vol 96 (5) ◽  
pp. 2785-2791 ◽  
Author(s):  
Tianying Ren ◽  
Wenxuan He ◽  
Matthews Scott ◽  
Alfred L. Nuttall
Keyword(s):  
Traveling Wave ◽  
Measurement Errors ◽  
Group Delay ◽  
Basilar Membrane ◽  
Acoustic Emissions ◽  
Otoacoustic Emission ◽  
Ear Canal ◽  
Round Trip ◽  
Compression Waves ◽  
Cochlear Partition

It is commonly accepted that the cochlea emits sound by a backward traveling wave along the cochlear partition. This belief is mainly based on an observation that the group delay of the otoacoustic emission measured in the ear canal is twice as long as the forward delay. In this study, the otoacoustic emission was measured in the gerbil under anesthesia not only in the ear canal but also at the stapes, eliminating measurement errors arising from unknown external- and middle-ear delays. The emission group delay measured at the stapes was compared with the group delay of basilar membrane vibration at the putative emission-generation site, the forward delay. The results show that the total intracochlear delay of the emission is equal to or smaller than the forward delay. For emissions with an f2/f1 ratio <1.2, the data indicate that the reverse propagation of the emission from its generation site to the stapes is much faster than a forward traveling wave to the f2 location. In addition, that the round-trip delays are smaller than the forward delay implies a basal shift of the emission generation site, likely explained by the basal shift of primary-tone response peaks with increasing intensity. However, for emissions with an f1 ≪ f2, the data cannot distinguish backward traveling waves from compression waves because of a very small f1 delay at the f2 site.

scholarly journals Noninvasive in vivo imaging reveals differences between tectorial membrane and basilar membrane traveling waves in the mouse cochlea

2015 ◽  
Vol 112 (10) ◽  
pp. 3128-3133 ◽  
Author(s):  
Hee Yoon Lee ◽  
Patrick D. Raphael ◽  
Jesung Park ◽  
Audrey K. Ellerbee ◽  
Brian E. Applegate ◽  
...  
Keyword(s):  
Traveling Waves ◽  
Traveling Wave ◽  
Basilar Membrane ◽  
Frequency Tuning ◽  
Tectorial Membrane ◽  
Inner Hair Cell ◽  
Auditory Response ◽  
3D Volume ◽  
Membrane Vibration

Sound is encoded within the auditory portion of the inner ear, the cochlea, after propagating down its length as a traveling wave. For over half a century, vibratory measurements to study cochlear traveling waves have been made using invasive approaches such as laser Doppler vibrometry. Although these studies have provided critical information regarding the nonlinear processes within the living cochlea that increase the amplitude of vibration and sharpen frequency tuning, the data have typically been limited to point measurements of basilar membrane vibration. In addition, opening the cochlea may alter its function and affect the findings. Here we describe volumetric optical coherence tomography vibrometry, a technique that overcomes these limitations by providing depth-resolved displacement measurements at 200 kHz inside a 3D volume of tissue with picometer sensitivity. We studied the mouse cochlea by imaging noninvasively through the surrounding bone to measure sound-induced vibrations of the sensory structures in vivo, and report, to our knowledge, the first measures of tectorial membrane vibration within the unopened cochlea. We found that the tectorial membrane sustains traveling wave propagation. Compared with basilar membrane traveling waves, tectorial membrane traveling waves have larger dynamic ranges, sharper frequency tuning, and apically shifted positions of peak vibration. These findings explain discrepancies between previously published basilar membrane vibration and auditory nerve single unit data. Because the tectorial membrane directly overlies the inner hair cell stereociliary bundles, these data provide the most accurate characterization of the stimulus shaping the afferent auditory response available to date.

Middle Ear Forward and Reverse Transmission in Gerbil

2006 ◽  
Vol 95 (5) ◽  
pp. 2951-2961 ◽  
Author(s):  
Wei Dong ◽  
Elizabeth S. Olson
Keyword(s):  
Inner Ear ◽  
Middle Ear ◽  
Otoacoustic Emissions ◽  
Otoacoustic Emission ◽  
Wide Frequency Range ◽  
Acoustic Energy ◽  
Ear Canal ◽  
Environmental Sound ◽  
Frequency Relationship

The middle ear transmits environmental sound to the inner ear. It also transmits acoustic energy sourced within the inner ear out to the ear canal, where it can be detected with a sensitive microphone as an otoacoustic emission. Otoacoustic emissions are an important noninvasive measure of the condition of sensory hair cells and to use them most effectively one must know how they are shaped by the middle ear. In this contribution, forward and reverse transmissions through the middle ear were studied by simultaneously measuring intracochlear pressure in scala vestibuli near the stapes and ear canal pressure. Measurements were made in gerbil, in vivo, with acoustic two-tone stimuli. The forward transmission pressure gain was about 20–25 dB, with a phase–frequency relationship that could be fit by a straight line, and was thus characteristic of a delay, over a wide frequency range. The forward delay was about 32 μs. The reverse transmission pressure loss was on average about 35 dB, and the phase–frequency relationship was again delaylike with a delay of about 38 μs. Therefore to a first approximation the middle ear operates similarly in the forward and reverse directions. The observation that the amount of pressure reduction in reverse transmission was greater than the amount of pressure gain in forward transmission suggests that complex motions of the tympanic membrane and ossicles affect reverse more than forward transmission.

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.

scholarly journals Hearing at threshold intensities: by slow mechanical traveling waves or by fast cochlear fluid pressure waves

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Haim Sohmer
Keyword(s):  
Soft Tissue ◽  
Hair Cells ◽  
Traveling Wave ◽  
Basilar Membrane ◽  
Fluid Pressure ◽  
Low Frequency ◽  
Frequency Discrimination ◽  
Outer Hair Cells ◽  
Common Mechanism ◽  
Frequency Stimulation

The three modes of auditory stimulation (air, bone and soft tissue conduction) at threshold intensities are thought to share a common excitation mechanism: the stimuli induce passive displacements of the basilar membrane propagating from the base to the apex (slow mechanical traveling wave), which activate the outer hair cells, producing active displacements, which sum with the passive displacements. However, theoretical analyses and modeling of cochlear mechanics provide indications that the slow mechanical basilar membrane traveling wave may not be able to excite the cochlea at threshold intensities with the frequency discrimination observed. These analyses are complemented by several independent lines of research results supporting the notion that cochlear excitation at threshold may not involve a passive traveling wave, and the fast cochlear fluid pressures may directly activate the outer hair cells: opening of the sealed inner ear in patients undergoing cochlear implantation is not accompanied by threshold elevations to low frequency stimulation which would be expected to result from opening the cochlea, reducing cochlear impedance, altering hydrodynamics. The magnitude of the passive displacements at threshold is negligible. Isolated outer hair cells in fluid display tuned mechanical motility to fluid pressures which likely act on stretch sensitive ion channels in the walls of the cells. Vibrations delivered to soft tissue body sites elicit hearing. Thus, based on theoretical and experimental evidence, the common mechanism eliciting hearing during threshold stimulation by air, bone and soft tissue conduction may involve the fast-cochlear fluid pressures which directly activate the outer hair cells.

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.

Distance Protection Application Based on Wavelet Transform and Traveling Wave Ranging

2012 ◽  
Vol 150 ◽  
pp. 40-44
Author(s):  
Peng Peng Kang ◽  
Xi Fang Zhu
Keyword(s):  
Wavelet Transform ◽  
Power System ◽  
Transmission Line ◽  
Software Design ◽  
Traveling Wave ◽  
Wave Theory ◽  
Distance Measurement ◽  
Distance Protection

This paper describes the wavelet transform theory, and traveling wave theory. When the power system transmission line fault occurs, the fault signal generated by sampling and analysis, and use a method of one-end fault distance measurement in transmission line. Finally the article gives the ranging devices’ hardware and software design.

Wave Theory of a Traveling-Wave Tube Operated Near the Cutoff

2004 ◽  
Vol 47 (5/6) ◽  
pp. 356-373 ◽  
Author(s):  
A. P. Kuznetsov ◽  
S. P. Kuznetsov ◽  
A. G. Rozhnev ◽  
E. V. Blokhina ◽  
L. V. Bulgakova
Keyword(s):  
Traveling Wave ◽  
Wave Theory ◽  
Traveling Wave Tube ◽  
Wave Tube
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