Fast cochlear amplification with slow outer hair cells

Lu, Timothy K.; Zhak, S.M.; Dallos, Peter; Sarpeshkar, Rahul

doi:10.1016/j.heares.2006.01.018

Cited by 57 publications

(44 citation statements)

References 83 publications

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“…4 are presented in Table 1. Values of the parameters used in the numerical calculations are in accordance with the experimental data obtained for mammalian cochleas (Weitzel et al, 2003;Ospeck et al, 2003;Liu et al, 2006; Reinchenbach, Hudspeth, 2010).…”

Section: Analytical Formula For Power Amplificationsupporting

confidence: 73%

Power Amplification and Selectivity in the Cochlear Amplifier

Kiełczyński¹

2013

Archives of Acoustics

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This paper presents a new model that describes the physical phenomena occurring in an individual Outer Hair Cell (OHC) in the human hearing organ (Cochlea). The new model employs the concept of parametric amplification and piezoelectricity. As a consequence, the proposed model may explain in a natural way many as yet unresolved problems about the mechanisms of: 1) power amplification, 2) nonlinearity, 3) fine tuning, or 4) high sensitivity that take place in the human hearing organ. Mathematical analysis of the model is performed. The equivalent electrical circuits of an individual OHC are established. The high selectivity of the OHC parametric amplifier is analyzed by solving the resulting Mathieu and Ince differential equations. An analytical formula for the power gain in the OHC's parametric amplifier has been developed. The proposed model has direct physical interpretation and all its elements have their physical counterparts in the actual structure of the cochlea. The numerical values of the individual elements of the electrical equivalent circuits are consistent with the experimental physiological data. It is anticipated that the proposed new model may contribute in future improvements of human cochlear implants as well as in development of new digital audio standards.

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Section: Analytical Formula For Power Amplificationsupporting

confidence: 73%

Power Amplification and Selectivity in the Cochlear Amplifier

Kiełczyński¹

2013

Archives of Acoustics

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“…1A. This is similar to the model of Neely and Kim, [3,5,7]. This have been the basis of many other published models, and so we do not present all the details here, but refer the reader to [4] in particular, to which this model is most similar.…”

Section: Mechanicalsupporting

confidence: 71%

An Electromechanical Model for the Cochlear Microphonic

Teal¹,

Lineton²,

Elliott³

et al. 2011

AIP Conference Proceedings

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Abstract. The first of the many electrical signals generated in the ear, nerves and brain as a response to a sound incident on the ear is the cochlear microphonic (CM). The CM is generated by the hair cells of the cochlea, primarily the outer hairs cells. The potentials of this signal are a nonlinear filtered version of the acoustic pressure at the tympanic membrane. The CM signal has been used very little in recent years for clinical audiology and audiological research. This is because of uncertainty in interpreting the CM signal as a diagnostic measure, and also because of the difficulty of obtaining the signal, which has usually required the use of a transtympanic electrode. There are however, several potential clinical and research applications for acquisition of the CM. To promote understanding of the CM, and potential clinical application, a model is presented which can account for the generation of the cochlear microphonic signal. The model incorporates micromechanical and macro-mechanical aspects of previously published models of the basilar membrane and reticular lamina, as well as cochlear fluid mechanics, piezoelectric activity and capacitance of the outer hair cells. It also models the electrical coupling of signals along the scalae.

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“…It has been proposed that the RC time constant is overcome by driving somatic motility with the unattenuated extracellular potential (44), negative feedback to increase the cutoff frequency of the receptor potential (45), activation of basolateral ion channels (14), tuning and high-pass filtering of the receptor potential through resonant electromechanical filtering of the input to a passive hair bundle (43), tuning of OHC extension by inertial loading of the soma despite low-pass filtering of the receptor potential (46), a reciprocal effect of somatic motility on the receptor potential (47,48), or resonant tectorial-membrane filtering of the input to a passive hair bundle that leads to a tuned receptor potential (10,37,49). Although the last three mechanisms make contributions in the present model, and the other processes may also have effects, the mechanism described here is simple and requires few assumptions.…”

Section: Discussionmentioning

confidence: 99%

Effects of cochlear loading on the motility of active outer hair cells

Maoiléidigh

Hudspeth

2013

Proc. Natl. Acad. Sci. U.S.A.

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Outer hair cells (OHCs) power the amplification of sound-induced vibrations in the mammalian inner ear through an active process that involves hair-bundle motility and somatic motility. It is unclear, though, how either mechanism can be effective at high frequencies, especially when OHCs are mechanically loaded by other structures in the cochlea. We address this issue by developing a model of an active OHC on the basis of observations from isolated cells, then we use the model to predict the response of an active OHC in the intact cochlea. We find that active hair-bundle motility amplifies the receptor potential that drives somatic motility. Inertial loading of a hair bundle by the tectorial membrane reduces the bundle's reactive load, allowing the OHC's active motility to influence the motion of the cochlear partition. The system exhibits enhanced sensitivity and tuning only when it operates near a dynamical instability, a Hopf bifurcation. This analysis clarifies the roles of cochlear structures and shows how the two mechanisms of motility function synergistically to create the cochlear amplifier. The results suggest that somatic motility evolved to enhance a preexisting amplifier based on active hair-bundle motility, thus allowing mammals to hear high-frequency sounds.adaptation | electromotility | hearing | nonlinear dynamics O ur ears are amazing signal detectors that reconcile great sensitivity with an enormous dynamic range. The faintest sounds that we can hear vibrate our eardrums by less than 1 pm and are a trillion times less intense than the loudest sounds that we can tolerate (1, 2). We can distinguish pure tones that differ in frequency by less than 0.2%, yet the frequency range of our ears exceeds a thousandfold (2). These features are all the more remarkable given that the mechanoreceptive organ of Corti operates in liquid and is therefore highly damped (3).An active process enhances the performance of the mammalian ear by augmenting sound-induced vibrations in the cochlea (2-6). This process results from the action of specialized outer hair cells (OHCs) whose motility boosts the motion of the cochlea in response to sounds, thus amplifying the signal transmitted to the brain. These cells counteract the damping that would otherwise limit the cochlea's sensitivity and frequency discrimination (3, 7). OHCs exhibit two forms of mechanical activity, hair-bundle motility and somatic motility, which may both contribute to the cochlear amplifier.Named for the mechanosensitive hair bundles protruding from their apices, hair cells transduce vibrations of their bundles into an electrical response. Cochlear hair cells are housed in the cochlear partition, which includes the organ of Corti sandwiched between the tectorial and basilar membranes (Fig. 1A). The hair bundle of each OHC is connected at its tip to the acellular tectorial membrane, and the soma of each OHC is linked to the basilar membrane through a rigid Deiters' cell (8). These membranes mechanically load each OHC with mass, damping, and stiffness....

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Fast cochlear amplification with slow outer hair cells

Cited by 57 publications

References 83 publications

Power Amplification and Selectivity in the Cochlear Amplifier

Power Amplification and Selectivity in the Cochlear Amplifier

An Electromechanical Model for the Cochlear Microphonic

Effects of cochlear loading on the motility of active outer hair cells

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