scholarly journals Imaging forward and Reverse Traveling Waves in the Cochlea

2018 ◽  
Author(s):  
A. Zosuls ◽  
L. C. Rupprecht ◽  
D. C. Mountain
Keyword(s):  
Hair Cell ◽  
Traveling Waves ◽  
Traveling Wave ◽  
Otoacoustic Emissions ◽  
Basilar Membrane ◽  
Full Potential ◽  
Inner Hair Cell ◽  
Probe Location ◽  
Cochlear Partition ◽  
Wave Modes

AbstractThe presence of forward and reverse traveling wave modes on the basilar membrane has important implications to how the cochlea functions as a filter, transducer, and amplifier of sound. The presence and parameters of traveling waves are of particular importance to interpreting otoacoustic emissions (OAE). OAE are vibrations that propagate out of the cochlea and are measureable as sounds emitted from the tympanic membrane. The interpretation of OAE is a powerful research and clinical diagnostic tool, but OAE use has not reached full potential because the mechanisms of their generation and propagation are not fully understood. Of particular interest and deliberation is whether the emissions propagate as a fluid compression wave or a structural traveling wave. In this study a mechanical probe was used to simulate an OAE generation site and optical imaging was used to measure displacement of the inner hair cell stereocilia of the gerbil cochlea. Inner hair cell stereocilia displacement measurements were made in the radial dimension as a function of their longitudinal location along the length of the basilar membrane in response to a transverse stimulation from the probe. The analysis of the spatial frequency response of the inner hair cell stereocilia at frequencies near the characteristic frequency (CF) of the measurement location suggests that a traveling wave propagates in the cochlear partition simultaneously basal and apical (forward and reverse) from the probe location. The traveling wave velocity was estimated to be 5.9m/s - 8m/s in the base (near CF of 29kHz - 40kHz) and 1.9m/s - 2.4m/s in the second turn (near CF of 2kHz - 3kHz). These results suggest that the cochlear partition is capable of supporting both forward and reverse traveling wave modes generated by a source driving the basilar membrane. This suggests that traveling waves in the cochlear partition contribute to OAE propagation.

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.

Reverse Cochlear Propagation in the Intact Cochlea of the Gerbil: Evidence for Slow Traveling Waves

2010 ◽  
Vol 103 (3) ◽  
pp. 1448-1455 ◽  
Author(s):  
Sebastiaan W. F. Meenderink ◽  
Marcel van der Heijden
Keyword(s):  
Traveling Waves ◽  
Otoacoustic Emissions ◽  
Group Delay ◽  
Basilar Membrane ◽  
Pressure Waves ◽  
Travel Times ◽  
Acoustic Measurements ◽  
Ear Canal ◽  
Direct Pressure ◽  
Cochlear Microphonic Potential

The inner ear can produce sounds, but how these otoacoustic emissions back-propagate through the cochlea is currently debated. Two opposing views exist: fast pressure waves in the cochlear fluids and slow traveling waves involving the basilar membrane. Resolving this issue requires measuring the travel times of emissions from their cochlear origin to the ear canal. This is problematic because the exact intracochlear location of emission generation is unknown and because the cochlea is vulnerable to invasive measurements. We employed a multi-tone stimulus optimized to measure reverse travel times. By exploiting the dispersive nature of the cochlea and by combining acoustic measurements in the ear canal with recordings of the cochlear-microphonic potential, we were able to determine the group delay between intracochlear emission-generation and their recording in the ear canal. These delays remained significant after compensating for middle-ear delay. The results contradict the hypothesis that the reverse propagation of emissions is exclusively by direct pressure waves.

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.

Traveling Waves Demonstrated by a Revolving Helix

1979 ◽  
Vol 88 (6) ◽  
pp. 768-770
Author(s):  
Luis D. Benítez
Keyword(s):  
Experimental Data ◽  
Traveling Waves ◽  
Traveling Wave ◽  
Basilar Membrane ◽  
Simple Procedure ◽  
Peak Amplitude ◽  
Phase Lag ◽  
Teaching Laboratory ◽  
Membrane Oscillations ◽  
Frequency Of Stimulation

A simple procedure for the demonstration of traveling waves in actual morion in the classroom is described. Using a matched set of experimental data on a) peak amplitude of basilar membrane oscillations, and b) phase-lag along the membrane, both for a given frequency of stimulation, it is possible to construct a solid spiral, or helix, of constantly changing diameter and pitch. When projected on a screen, the helix will look like a longitudinal amplitude gradient along the basilar membrane; as the helix is rotated, the projection will appear as a traveling wave. It is suggested that the device, because of its inherent simplicity, is a useful aid in a teaching laboratory for future otolaryngologists, audiologists and other professionals related to the field of hearing.

Sign in / Sign up

Export Citation Format

Share Document