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May 2012

Volume 131, Issue 5, pp. EL355-4232

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Modeling auditory evoked brainstem responses to transient stimuli

Filip Munch Rønne, Torsten Dau, James Harte, and Claus Elberling

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3903-3913 (2012); (11 pages) | Cited 1 time

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A quantitative model is presented that describes the formation of auditory brainstem responses (ABRs) to tone pulses, clicks, and rising chirps as a function of stimulation level. The model computes the convolution of the instantaneous discharge rates using the “humanized” nonlinear auditory-nerve model of Zilany and Bruce [J. Acoust. Soc. Am. 122, 402–417 (2007)] and an empirically derived unitary response function which is assumed to reflect contributions from different cell populations within the auditory brainstem, recorded at a given pair of electrodes on the scalp. It is shown that the model accounts for the decrease of tone-pulse evoked wave-V latency with frequency but underestimates the level dependency of the tone-pulse as well as click-evoked latency values. Furthermore, the model correctly predicts the nonlinear wave-V amplitude behavior in response to the chirp stimulation both as a function of chirp sweeping rate and level. Overall, the results support the hypothesis that the pattern of ABR generation is strongly affected by the nonlinear and dispersive processes in the cochlea.
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43.64.Bt Models and theories of the auditory system
43.64.Qh Electrophysiology of the auditory central nervous system
43.64.Ri Evoked responses to sounds

Transmission of cochlear distortion products as slow waves: A comparison of experimental and model data

Aleš Vetešník and Anthony W. Gummer

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3914-3934 (2012); (21 pages) | Cited 2 times

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There is a long-lasting question of how distortion products (DPs) arising from nonlinear amplification processes in the cochlea are transmitted from their generation sites to the stapes. Two hypotheses have been proposed: (1) the slow-wave hypothesis whereby transmission is via the transverse pressure difference across the cochlear partition and (2) the fast-wave hypothesis proposing transmission via longitudinal compression waves. Ren with co-workers have addressed this topic experimentally by measuring the spatial vibration pattern of the basilar membrane (BM) in response to two tones of frequency f1 and f2. They interpreted the observed negative phase slopes of the stationary BM vibrations at the cubic distortion frequency fDP = 2f1 − f2 as evidence for the fast-wave hypothesis. Here, using a physically based model, it is shown that their phase data is actually in accordance with the slow-wave hypothesis. The analysis is based on a frequency-domain formulation of the two-dimensional motion equation of a nonlinear hydrodynamic cochlea model. Application of the analysis to their experimental data suggests that the measurement sites of negative phase slope were located at or apical to the DP generation sites. Therefore, current experimental and theoretical evidence supports the slow-wave hypothesis. Nevertheless, the analysis does not allow rejection of the fast-wave hypothesis.
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43.64.Jb Otoacoustic emissions
43.64.Kc Cochlear mechanics
43.64.Bt Models and theories of the auditory system

Unification and extension of monolithic state space and iterative cochlear models

Michael J. Rapson, Jonathan C. Tapson, and David Karpul

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 3935-3952 (2012); (18 pages)

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Time domain cochlear models have primarily followed a method introduced by Allen and Sondhi [J. Acoust. Soc. Am. 66, 123–132 (1979)]. Recently the “state space formalism” proposed by Elliott et al. [J. Acoust. Soc. Am. 122, 2759–2771 (2007)] has been used to simulate a wide range of nonlinear cochlear models. It used a one-dimensional approach that is extended to two dimensions in this paper, using the finite element method. The recently developed “state space formalism” in fact shares a close relationship to the earlier approach. Working from Diependaal et al. [J. Acoust. Soc. Am. 82, 1655–1666 (1987)] the two approaches are compared and the relationship formalized. Understanding this relationship allows models to be converted from one to the other in order to utilize each of their strengths. A second method to derive the state space matrices required for the “state space formalism” is also presented. This method offers improved numerical properties because it uses the information available about the model more effectively. Numerical results support the claims regarding fluid dimension and the underlying similarity of the two approaches. Finally, the recent advances in the state space formalism [Bertaccini and Sisto, J. Comp. Phys. 230, 2575–2587 (2011)] are discussed in terms of this relationship.
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43.64.Kc Cochlear mechanics
43.64.Bt Models and theories of the auditory system
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