Power Dissipation in the Subtectorial Space of the Mammalian Cochlea Is Modulated by Inner Hair Cell Stereocilia

Prodanovic, Srdjan; Gracewski, Sheryl M.; Nam, Jong-Hoon

doi:10.1016/j.bpj.2014.12.027

Cited by 22 publications

(20 citation statements)

References 83 publications

(114 reference statements)

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“…The energy loss in that system is due to the shear between the two places and the internal drag of the hair bundle is negligible. This analysis is indeed consistent with earlier reports [20,35,36].…”

Section: Amplifier Gain -Dissipative Energysupporting

confidence: 94%

Energy Output from a Single Outer Hair Cell

Iwasa

2016

Biophysical Journal

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Electromotility of outer hair cells (OHCs) has been extensively studied with in vitro experiments because of its physiological significance to the cochlear amplifier, which provides the exquisite sensitivity and frequency selectivity of the mammalian ear. However, these studies have been performed largely under load-free conditions or with static load, while these cells function in vivo in a dynamic environment, receiving electrical energy to enhance mechanical oscillation in the inner ear. This gap leaves uncertainties in addressing a key issue, how much mechanical energy an OHC provides. This study is an attempt of bridging the gap by introducing a simple one-dimensional model for electromotility of OHC in a dynamic environment. This model incorporates a feedback loop involving the receptor potential and the mechanical load on OHC, and leads to an analytical expression for the membrane capacitance, which explicitly describes the dependence on the elastic load, viscous drag, and the mass. The derived equation of motion was examined in a mass-less model system with realistic parameter values for OHC. It was found that viscous drag is more effective than elastic load in enhancing the receptor potential that drives the cell. For this reason, it is expected that OHCs are more effective in counteracting viscous drag than providing elastic energy to the system.

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Section: Amplifier Gain -Dissipative Energysupporting

confidence: 94%

Energy Output from a Single Outer Hair Cell

Iwasa

2016

Biophysical Journal

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“…The value may range between 0.1 and 1 μ N · s/m for a length of L = 10 μ m (the longitudinal spacing between outer hair cells). In our recent study ( 16 ), it was shown that this dissipation in the subtectorial space can further increase at low frequencies because of the additional viscous friction of the inner-hair-cell stereocilia bundle. In this work, we incorporated only the simplistic parallel plate estimations ( c STS ).…”

Section: Discussionmentioning

confidence: 95%

“…In theory, the outer hair cells can generate more power than the acoustic input power at 60 dB sound pressure level ( 9 , 10 ). On the other hand, how power is dissipated in the cochlea has been investigated at the cellular level ( 11 , 12 , 13 , 14 ), tissue level ( 15 , 16 ), and systems level ( 10 ).…”

Section: Introductionmentioning

confidence: 99%

Power Dissipation in the Cochlea Can Enhance Frequency Selectivity

Prodanovic

Gracewski

Nam

2019

Biophysical Journal

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The cochlear cavity is filled with viscous fluids, and it is partitioned by a viscoelastic structure called the organ of Corti complex. Acoustic energy propagates toward the apex of the cochlea through vibrations of the organ of Corti complex. The dimensions of the vibrating structures range from a few hundred (e.g., the basilar membrane) to a few micrometers (e.g., the stereocilia bundle). Vibrations of microstructures in viscous fluid are subjected to energy dissipation. Because the viscous dissipation is considered to be detrimental to the function of hearing-sound amplification and frequency tuning-the cochlea uses cellular actuators to overcome the dissipation. Compared to extensive investigations on the cellular actuators, the dissipating mechanisms have not been given appropriate attention, and there is little consensus on damping models. For example, many theoretical studies use an inviscid fluid approximation and lump the viscous effect to viscous damping components. Others neglect viscous dissipation in the organ of Corti but consider fluid viscosity. We have developed a computational model of the cochlea that incorporates viscous fluid dynamics, organ of Corti microstructural mechanics, and electrophysiology of the outer hair cells. The model is validated by comparing with existing measurements, such as the viscoelastic response of the tectorial membrane, and the cochlear input impedance. Using the model, we investigated how dissipation components in the cochlea affect its function. We found that the majority of acoustic energy dissipation of the cochlea occurs within the organ of Corti complex, not in the scalar fluids. Our model suggests that an appropriate dissipation can enhance the tuning quality by reducing the spread of energy provided by the outer hair cells' somatic motility.

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“…A recent modeling study (Prodanovic et al 2015) suggests that viscous damping in the sub-tectorial space influences the oscillatory behavior of the cochlear partition and the dissipation of energy. Loss of limbal attachment and the absence of Hensen's stripe are both likely to influence sub-tectorial fluid flow and could therefore lead to a change in the production of SOAEs, albeit in different regions of the cochlea.…”

Section: Discussionmentioning

confidence: 99%

Increased Spontaneous Otoacoustic Emissions in Mice with a Detached Tectorial Membrane

Cheatham¹,

Ahmad²,

Zhou³

et al. 2015

JARO

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Mutations in genes encoding tectorial membrane (TM) proteins are a significant cause of human hereditary hearing loss , and several mouse models have been developed to study the functional significance of this accessory structure in the mammalian cochlea. In this study, we use otoacoustic emissions (OAE), signals obtained from the ear canal that provide a measure of cochlear function, to characterize a mouse in which the TM is detached from the spiral limbus due to an absence of otoancorin (Otoa, Lukashkin et al. 2012). Our results demonstrate that spontaneous emissions (SOAE), sounds produced in the cochlea without stimulation, increase dramatically in mice with detached TMs even though their hearing sensitivity is reduced. This behavior is unusual because wild-type (WT) controls are rarely spontaneous emitters. SOAEs in mice lacking Otoa predominate around 7 kHz, which is much lower than in either WT animals when they generate SOAEs or in mutant mice in which the TM protein Ceacam16 is absent (Cheatham et al. 2014). Although both mutants lack Hensen's stripe, loss of this TM feature is only observed in regions coding frequencies greater than~15 kHz in WT mice so its loss cannot explain the low-frequency, de novo SOAEs observed in mice lacking Otoa. The fact that~80 % of mice lacking Otoa produce SOAEs even when they generate smaller distortion product OAEs suggests that the active process is still functioning in these mutants but the system(s) involved have become less stable due to alterations in TM structure.

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Power Dissipation in the Subtectorial Space of the Mammalian Cochlea Is Modulated by Inner Hair Cell Stereocilia

Cited by 22 publications

References 83 publications

Energy Output from a Single Outer Hair Cell

Energy Output from a Single Outer Hair Cell

Power Dissipation in the Cochlea Can Enhance Frequency Selectivity

Increased Spontaneous Otoacoustic Emissions in Mice with a Detached Tectorial Membrane

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