An intrinsic frequency limit to the cochlear amplifier

@article{Gale1997AnIF,
  title={An intrinsic frequency limit to the cochlear amplifier},
  author={Jonathan E. Gale and Jonathan F Ashmore},
  journal={Nature},
  year={1997},
  volume={389},
  pages={63-66}
}
Hearing in mammals depends on a feedback process within the inner ear termed the 'cochlear amplifier'. The essential components of this amplifier are sensorimotor cells, the outer hair cells, which transduce motion of the basilar membrane induced by sound and generate forces to cancel the viscous damping of the cochlear partition. Outer hair cells alter the passive mechanics of the cochlea, enhancing both the sensitivity and the frequency selectivity of the auditory system. The molecular basis… 

The membrane-based mechanism of cell motility in cochlear outer hair cells.

Direct support to the feedback hypothesis comes from the fact that OHCs posses a unique ability to change significantly their shape in response to electrical stimulation, a phenomenon called electromotility.

Outer hair cell active force generation in the cochlear environment.

A model that takes into account the mechanical, electrical, and mechanoelectrical properties of the cell wall (membrane) and cochlear environment is proposed and it is shown that, despite the mechanical and electrical filtering, the outer hair cell is capable of generating a frequency-tuned force with a maximal value of about 40 pN.

A Mixed Mode Cochlear Amplifier Including Neural Feedback

The mixed mode cochlear amplifier (MMCA) model is derived from the physiology of the cochlea. It is comprised of three main elements of the peripheral hearing system: the cochlear mechanics, hair

In vivo evidence for a cochlear amplifier in the hair-cell bundle of lizards

In vivo evidence of hair-cell bundle involvement in active processes is provided and supports the notion that, in nonmammals, the cochlear amplifier in the hair cells is driven by a bundle motor system.

Three-dimensional current flow in a large-scale model of the cochlea and the mechanism of amplification of sound

A multi-element, large-scale computational model of cochlear sound transduction is constructed to study the underlying potassium (K+) recirculation and suggests that OHC electromotility could serve as a single amplification mechanism over the entire hearing range.

Molecular mechanisms of sound amplification in the mammalian cochlea.

It is shown here that outer hair cells selectively take up fructose, at rates high enough to suggest that a sugar transporter may be part of the motor complex.

Limiting dynamics of high-frequency electromechanical transduction of outer hair cells.

It is concluded that the electromechanical transduction process of OHCs possesses the necessary high-frequency properties to enable amplification of the travelling wave over the entire hearing range.
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References

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An active process in cochlear mechanics

High-frequency motility of outer hair cells and the cochlear amplifier.

It is proposed that electromotility at high frequencies is driven instead by extracellular potential gradients across the hair cell, and it is shown that this driving voltage is not subject to low-pass filtering and is sufficiently large.

A fast motile response in guinea‐pig outer hair cells: the cellular basis of the cochlear amplifier.

Outer hair cells from the cochlea of the guinea‐pig were isolated and their motile properties studied in short‐term culture by the whole‐cell variant of the patch recording technique, concluding that interaction between actin and myosin, although present in the cell, is unlikely to account for the cell motility.

Biophysics of the cochlea: linear approximation.

Several deficiencies affecting previous "box" models of the cochlea are overcome in this paper. Both mechanical and hydrodynamical aspects are treated at a level adequate to the complexity of

On the frequency limit and phase of outer hair cell motility: effects of the membrane filter

  • J. Santos-Sacchi
  • Biology, Physics
    The Journal of neuroscience : the official journal of the Society for Neuroscience
  • 1992
Findings question the ability of the OHC mechanical response to influence organ of Corti micromechanics at high acoustic frequencies where a tuned amplification of basilar membrane motion is hypothesized.

A membrane-based force generation mechanism in auditory sensory cells.

Auditory outer hair cells can elongate and shorten at acoustic frequencies in response to changes of plasma membrane potential and it is suggested that the force generation mechanism is driven by voltage-dependent conformational changes within a dense array of large transmembrane proteins associated with the site of electromechanical transduction.

Temperature-dependence of a fast motile response in isolated outer hair cells of the guinea-pig cochlea.

OHC are shown to be motile at 37 degrees C, and the temperature-dependence is quite weak, which is difficult to reconcile with mechanisms involving an intermediate biochemical messenger, including those based on actomyosin.

Reversible inhibition of voltage-dependent outer hair cell motility and capacitance

  • J. Santos-Sacchi
  • Biology
    The Journal of neuroscience : the official journal of the Society for Neuroscience
  • 1991
It is interesting to note that the nonlinear capacitance will dynamically influence the time constant of the OHC during acoustically evoked receptor potential generation.

The outer hair cell motor in membrane patches

Under conditions of isotropic membrane stress there was no change in the peak measured capacitance in contrast to that measured in previous whole-cell recordings.

A membrane motor model for the fast motility of the outer hair cell.

  • K. Iwasa
  • Biology, Engineering
    The Journal of the Acoustical Society of America
  • 1994
The model predicts the force produced under isometric condition is about 0.1 nN/mV, in agreement with values estimated from in vivo conditions, and the effect of an elastic load attached to the cell is also discussed.