Basilar membrane mechanics in the 6–9kHz region of sensitive chinchilla cochleae

2007 ◽  
Vol 121 (5) ◽  
pp. 2792-2804 ◽  
Author(s):  
William S. Rhode
Keyword(s):  
Basilar Membrane ◽  
Membrane Mechanics

Modeling DPOAE Input/Output Function Compression: Comparisons with Hearing Thresholds

2014 ◽  
Vol 25 (08) ◽  
pp. 746-759 ◽  
Author(s):  
Shaum P. Bhagat
Keyword(s):  
Research Design ◽  
Basilar Membrane ◽  
Otoacoustic Emission ◽  
Normal Hearing ◽  
Membrane Mechanics ◽  
Distortion Product Otoacoustic Emission ◽  
Input Output ◽  
Distortion Product ◽  
Hearing Thresholds ◽  
Cochlear Compression

Background: Basilar membrane input/output (I/O) functions in mammalian animal models are characterized by linear and compressed segments when measured near the location corresponding to the characteristic frequency. A method of studying basilar membrane compression indirectly in humans involves measuring distortion-product otoacoustic emission (DPOAE) I/O functions. Previous research has linked compression estimates from behavioral growth-of-masking functions to hearing thresholds. Purpose: The aim of this study was to compare compression estimates from DPOAE I/O functions and hearing thresholds at 1 and 2 kHz. Research Design: A prospective correlational research design was performed. The relationship between DPOAE I/O function compression estimates and hearing thresholds was evaluated with Pearson product-moment correlations. Study Sample: Normal-hearing adults (n = 16) aged 22–42 yr were recruited. Data Collection and Analysis: DPOAE I/O functions (L 2 = 45–70 dB SPL) and two-interval forced-choice hearing thresholds were measured in normal-hearing adults. A three-segment linear regression model applied to DPOAE I/O functions supplied estimates of compression thresholds, defined as breakpoints between linear and compressed segments and the slopes of the compressed segments. Pearson product-moment correlations between DPOAE compression estimates and hearing thresholds were evaluated. Results: A high correlation between DPOAE compression thresholds and hearing thresholds was observed at 2 kHz, but not at 1 kHz. Compression slopes also correlated highly with hearing thresholds only at 2 kHz. Conclusions: The derivation of cochlear compression estimates from DPOAE I/O functions provides a means to characterize basilar membrane mechanics in humans and elucidates the role of compression in tone detection in the 1–2 kHz frequency range.

scholarly journals A role for tectorial membrane mechanics in activating the cochlear amplifier

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Amir Nankali ◽  
Yi Wang ◽  
Clark Elliott Strimbu ◽  
Elizabeth S. Olson ◽  
Karl Grosh
Keyword(s):  
Phase Shift ◽  
Basilar Membrane ◽  
Outer Hair Cells ◽  
Cycle Phase ◽  
Tectorial Membrane ◽  
Cochlear Amplifier ◽  
Membrane Mechanics ◽  
Acoustic Stimuli ◽  
Membrane Resonance ◽  
Electrical Responses

Abstract The mechanical and electrical responses of the mammalian cochlea to acoustic stimuli are nonlinear and highly tuned in frequency. This is due to the electromechanical properties of cochlear outer hair cells (OHCs). At each location along the cochlear spiral, the OHCs mediate an active process in which the sensory tissue motion is enhanced at frequencies close to the most sensitive frequency (called the characteristic frequency, CF). Previous experimental results showed an approximate 0.3 cycle phase shift in the OHC-generated extracellular voltage relative the basilar membrane displacement, which was initiated at a frequency approximately one-half octave lower than the CF. Findings in the present paper reinforce that result. This shift is significant because it brings the phase of the OHC-derived electromotile force near to that of the basilar membrane velocity at frequencies above the shift, thereby enabling the transfer of electrical to mechanical power at the basilar membrane. In order to seek a candidate physical mechanism for this phenomenon, we used a comprehensive electromechanical mathematical model of the cochlear response to sound. The model predicts the phase shift in the extracellular voltage referenced to the basilar membrane at a frequency approximately one-half octave below CF, in accordance with the experimental data. In the model, this feature arises from a minimum in the radial impedance of the tectorial membrane and its limbal attachment. These experimental and theoretical results are consistent with the hypothesis that a tectorial membrane resonance introduces the correct phasing between mechanical and electrical responses for power generation, effectively turning on the cochlear amplifier.

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