Auditory Nerve Excitation via a Non-traveling Wave Mode of Basilar Membrane Motion

Huang, Stanley; Olson, Elizabeth S.

doi:10.1007/s10162-011-0272-5

Cited by 20 publications

(11 citation statements)

References 65 publications

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“…The space constant is~80 mm (11,23). In addition, at frequencies above the BF, the STP response becomes dominated by the fast, compression pressure mode, which is not involved in cochlear excitation, at least to first order (24)(25)(26). Frequency regions of interest-those in which STV responses are local and STP responses are dominated by the slow, traveling wave-are those in which the phase-versus-frequency of these responses shows traveling-wave accumulation.…”

Section: Resultsmentioning

confidence: 99%

Two-Tone Suppression of Simultaneous Electrical and Mechanical Responses in the Cochlea

Dong

Olson

2016

Biophysical Journal

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Cochlear frequency tuning is based on a mildly tuned traveling-wave response that is enhanced in amplitude and sharpness by outer hair cell (OHC)-based forces. The nonlinear and active character of this enhancement is the fundamental manifestation of cochlear amplification. Recently, mechanical (pressure) and electrical (extracellular OHC-generated voltage) responses were simultaneously measured close to the sensory tissue's basilar membrane. Both pressure and voltage were tuned and showed traveling-wave phase accumulation, evidence that they were locally generated responses. Approximately at the frequency where nonlinearity commenced, the phase of extracellular voltage shifted up, to lead pressure by >1/4 cycle. Based on established and fundamental relationships among voltage, force, pressure, displacement, and power, the observed phase shift was identified as the activation of cochlear amplification. In this study, the operation of the cochlear amplifier was further explored, via changes in pressure and voltage responses upon delivery of a second, suppressor tone. Two different suppression paradigms were used, one with a low-frequency suppressor and a swept-frequency probe, the other with two swept-frequency tones, either of which can be considered as probe or suppressor. In the presence of a high-level low-frequency suppressor, extracellular voltage responses at probe-tone frequencies were greatly reduced, and the pressure responses were reduced nearly to their linear, passive level. On the other hand, the amplifier-activating phase shift between pressure and voltage responses was still present in probe-tone responses. These findings are consistent with low-frequency suppression being caused by the saturation of OHC electrical responses and not by a change in the power-enabling phasing of the underlying mechanics. In the two-tone swept-frequency suppression paradigm, mild suppression was apparent in the pressure responses, while deep notches could develop in the voltage responses. A simple analysis, based on a two-wave differencing scheme, was used to explore the observations.

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Section: Resultsmentioning

confidence: 99%

Two-Tone Suppression of Simultaneous Electrical and Mechanical Responses in the Cochlea

Dong

Olson

2016

Biophysical Journal

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“…One possibility is that the viscous 0.5% HA fluid caused the cochlea’s mechanical response to by dominated by a fast-mode instead of the normal slow traveling-wave mode (Huang and Olson, 2011; Olson, 2013). Fast-mode operation would reduce the latency of the CAP response and account for the short latency of P0.…”

Section: Discussionmentioning

confidence: 99%

Cochlear perfusion with a viscous fluid

Wang

Olson

2016

Hearing Research

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The flow of viscous fluid in the cochlea induces shear forces, which could provide benefit in clinical practice, for example to guide cochlear implant insertion or produce static pressure to the cochlear partition or wall. From a research standpoint, studying the effects of a viscous fluid in the cochlea provides data for better understanding cochlear fluid mechanics. However, cochlear perfusion with a viscous fluid may damage the cochlea. In this work we studied the physiological and anatomical effects of perfusing the cochlea with a viscous fluid. Gerbil cochleae were perfused at a rate of 2.4 μL/min with artificial perilymph (AP) and sodium hyaluronate (Healon, HA) in four different concentrations (0.0625%, 0.125%, 0.25%, 0.5%). The different HA concentrations were applied either sequentially in the same cochlea or individually in different cochleae. The perfusion fluid entered from the round window and was withdrawnfrom basal scala vestibuli, in order to perfuse the entire perilymphatic space. Compound action potentials (CAP) were measured after each perfusion. After perfusion with increasing concentrations of HA in the order of increasing viscosity, the CAP thresholds generally increased. The threshold elevation after AP and 0.0625% HA perfusion was small or almost zero, and the 0.125% HA was a borderline case, while the higher concentrations significantly elevated CAP thresholds. Histology of the cochleae perfused with the 0.0625% HA showed an intact Reissner’s membrane, while in cochleae perfused with 0.125% and 0.25% HA Reissner’s membrane (RM) was torn. Thus, the CAP threshold elevation was likely due to the broken of RM, which likely caused by the shear stress produced by the flow of the viscous fluid. Our results and analysis indicate that the cochlea can sustain, without a significant CAP threshold shift, up to a 1.5 Pa shear stress. Beside these finding, in the 0.125% and 0.25% HA perfusion cases, a temporary CAP threshold shift was observed, perhaps due to the presence and then clearance of viscous fluid within the cochlea, or to a temporary position shift of the Organ of Corti. After 0.5% HA perfusion, a short latency positive peak (P0) appeared in the CAP wavefrom. This P0 might be due to a change in the cochlea’s traveling-wave pattern, or distortion in the cochlear microphonic.

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“…Conversely, when measured at a location far away from the BM, or apical to the TW's BF, the ST pressure is dominated by the CW, moving in-phase with the motion of the stapes and longitudinally between the oval and round windows. The CW is considered as a background pressure in forward sound propagation, increasing linearly with the motion of the stapes , and is relatively unimportant to cochlear mechanics, because it causes little vibration of the BM (Robles and Ruggero 2001) and neural excitation only at very high stimulus levels (Huang and Olson 2011).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Intracochlear Pressure Measurements from Two Cochlear Locations: Propagation of Distortion Products in Gerbil

Dong

2016

JARO

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Sound energy propagates in the cochlea through a forward-traveling or slow wave supported by the cochlear partition and fluid inertia. Additionally, cochlear models support traveling wave propagation in the reverse direction as the expected mechanism for conveying otoacoustic emissions out of the cochlea. Recently, however, this hypothesis has been questioned, casting doubt on the process by which otoacoustic emissions travel back out through the cochlea. The proposed alternative reverse travel path for emissions is directly through the fluids of the cochlea as a compression pressure in the form of a fast wave. In the present study, a custom-made micropressure sensor was used in vivo in the gerbil cochlea to map two-tone-evoked pressure responses at distinct longitudinal and vertical locations in both the scala tympani and scala vestibuli. Analyses of the magnitude and phase of intracochlear pressure responses at the primary tone and distortion product frequencies were used to distinguish between fast and slow waves in both the forward-and reverse-propagation directions. Results demonstrated that distortion products may travel in both forward and reverse directions postgeneration and the existence of both traveling and compression waves. The forward-traveling component appeared to duplicate the process of any external tone, tuned to the local characteristic-frequency place, as it increased compressively and nonlinearly with primary-tone levels. A compression wave was evidenced at frequencies above the cutoff of the recording site. In the opposite direction, a reversetraveling wave played the major role in driving the stapes reversely and contributed to the distortion product otoacoustic emission. The compression wave may also play a role in reverse propagation when distortion products are generated at a region close to the stapes.

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Auditory Nerve Excitation via a Non-traveling Wave Mode of Basilar Membrane Motion

Cited by 20 publications

References 65 publications

Two-Tone Suppression of Simultaneous Electrical and Mechanical Responses in the Cochlea

Two-Tone Suppression of Simultaneous Electrical and Mechanical Responses in the Cochlea

Cochlear perfusion with a viscous fluid

Simultaneous Intracochlear Pressure Measurements from Two Cochlear Locations: Propagation of Distortion Products in Gerbil

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