Nonlinear time-domain cochlear model for transient stimulation and human otoacoustic emission.
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ABSTRACT:
SUBMITTER: Verhulst S
PROVIDER: S-EPMC3528681 | biostudies-other | 2012 Dec
REPOSITORIES: biostudies-other
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Project description:Distortion-product otoacoustic emissions (DPOAEs) were measured in rabbits as time waveforms by employing a phase-rotation technique to cancel all components in the final average, except the 2f1-f2 DPOAE. Subsequent filtering allowed the DPOAE waveform to be clearly visualized in the time domain. In most conditions, f2 was turned off for 6 ms, which produced a gap so that the DPOAE was no longer generated. These procedures allowed the DPOAE onset as well as the decay during the gap to be observed in the time domain. DPOAEs were collected with L1 = L2 = 65-dB sound pressure level primary-tone levels for f2/f1 ratios from 1.25 to 1.01 in 0.02 steps. Findings included the appearance of complex onsets and decays for the DPOAE time waveforms as the f2/f1 ratio was decreased and the DPOAE level was reduced. These complexities were unaffected by interference tones (ITs) near the DPOAE frequency place (fdp), but could be removed by ITs presented above f2, which also increased DPOAE levels. Similar outcomes were observed when DPOAEs were measured at a sharp notch in the DPOAE level as a function of the f2 primary tone frequency, i.e., DP-gram. Both findings were consistent with the hypothesis that the DPOAE-ratio function, and some notches in the DP-gram, are caused by interactions of distributed DPOAE components with unique phases.
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Project description:Transient-evoked otoacoustic emissions (TEOAEs) at high frequencies are a non-invasive physiological test of basilar membrane mechanics at the basal end, and have clinical potential to detect risk of hearing loss related to outer-hair-cell dysfunction. Using stimuli with constant incident pressure across frequency, TEOAEs were measured in experiment 1 at low frequencies (0.7-8 kHz) and high frequencies (7.1-14.7 kHz) in adults with normal hearing up to 8 kHz and varying hearing levels from 9 to 16 kHz. In combination with click stimuli, chirp stimuli were used with slow, medium and fast sweep rates for which the local frequency increased or decreased with time. Chirp TEOAEs were transformed into equivalent click TEOAEs by inverse filtering out chirp stimulus phase, and analyzed similarly to click TEOAEs. To improve detection above 8 kHz, TEOAEs were measured in experiment 2 with higher-level stimuli and longer averaging times. These changes increased the TEOAE signal-to-noise ratio (SNR) by 10 dB. Slower sweep rates were investigated but the elicited TEOAEs were detected in fewer ears compared to faster rates. Data were acquired in adults and children (age 11-17 y), including children with cystic fibrosis (CF) treated with ototoxic antibiotics. Test-retest measurements revealed satisfactory repeatability of high-frequency TEOAE SNR (median of 1.3 dB) and coherence synchrony measure, despite small test-retest differences related to changes in forward and reverse transmission in the ear canal. The results suggest the potential use of such tests to screen for sensorineural hearing loss, including ototoxic loss. Experiment 2 was a feasibility study to explore TEOAE test parameters that might be used in a full-scale study to screen CF patients for risk of ototoxic hearing loss.
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Project description:Sounds originating from within the inner ear, known as otoacoustic emissions (OAEs), are widely exploited in clinical practice but the mechanisms underlying their generation are not entirely clear. Here we present simulation results and theoretical considerations based on a hydrodynamic model of the human inner ear. Simulations show that, if the cochlear amplifier (CA) gain is a smooth function of position within the active cochlea, filtering performed by a middle ear with an irregular, i.e., nonsmooth, forward transfer function suffices to produce irregular and long-lasting residual oscillations of cochlear basilar membrane (BM) at selected frequencies. Feeding back to the middle ear through hydrodynamic coupling afforded by the cochlear fluid, these oscillations are detected as transient evoked OAEs in the ear canal. If, in addition, the CA gain profile is affected by irregularities, residual BM oscillations are even more irregular and tend to evolve towards self-sustaining oscillations at the loci of gain irregularities. Correspondingly, the spectrum of transient evoked OAEs exhibits sharp peaks. If both the CA gain and the middle-ear forward transfer function are smooth, residual BM oscillations have regular waveforms and extinguish rapidly. In this case no emissions are produced. Finally, and paradoxically albeit consistent with observations, simulating localized damage to the CA results in self-sustaining BM oscillations at the characteristic frequencies (CFs) of the sites adjacent to the damage region, accompanied by generation of spontaneous OAEs. Under these conditions, stimulus-frequency OAEs, with typical modulation patterns, are also observed for inputs near hearing threshold. This approach can be exploited to provide novel diagnostic tools and a better understanding of key phenomena relevant for hearing science.
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Project description:Distortion product otoacoustic emissions (DPOAEs) have long been heralded as a means to objectively monitor cochlear function and increasingly are becoming a key component in hearing surveillance programs for individuals at risk for ototoxic- and occupational noise-related hearing loss. Yet clinicians are unsure how to define clinically meaningful shifts in DPOAE level. In this study, a meta-analysis approach is used to synthesize the DPOAE level test-retest literature to construct a set of DPOAE level shift reference limits that can be used clinically to define a statistically significant emission change.The authors reviewed all published articles identified through a Medline search using the terms "Otoacoustic Emission Variability," "Otoacoustic Emission Reliability," "Otoacoustic Emission Repeatability," and "Otoacoustic Emission Test Retest" restricted to DPOAEs, adults, and English language. Articles with DPOAE level data elicited by moderate stimulus levels for f2 frequencies of 1000, 2000, 4000, or 6000 Hz were selected because these stimulus parameters were relatively well represented in the literature. The authors only included articles that reported the standard error of the measurement (SEM) or from which the SEM could be calculated. Meta-analysis was used to estimate the population mean SEM over the included studies. Models were fit separately for each f2 primary and included days since baseline and study-specific random effects.Ten DPOAE test-retest studies met inclusion criteria for this meta-analysis. The SEM values varied widely across published studies (0.57 to 3.9 dB) and were provided for relatively short time intervals (less than 15 days on average). Time, or days since baseline, was statistically significant at higher f2 frequencies (4000 and 6000 Hz). From the model results, 90% reference limits specific to the f2 and elapsed time between baseline and follow-up measurements were established. Reference limits provided correspond to negative (emission decrement) and positive (emission enhancement) shifts indicative of the amount of measurement variability that, using this approach, must be tolerated as "normal" fluctuations over time. Changes larger than the reference limits are considered significant and warrant follow-up testing.The meta-analysis presented provides reference limits that are appropriate for a set of specific f2 frequencies and time intervals. The meta-analysis concerns the SEM statistic directly, so that any preferred reference limit can be computed from the results and should be predicated upon the screening application. The presumed advantage of this meta-analytic approach is increased precision relative to limits suggested by any of the individual studies included in the analysis.
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Project description:A procedure for extracting the nonlinear component of the stimulus-frequency otoacoustic emission (SFOAE) is described. This nSFOAE measures the amount by which the cochlear response deviates from linear additivity when the input stimulus is doubled in amplitude. When a 4.0-kHz tone was presented alone, the magnitude of the nSFOAE response remained essentially constant throughout the 400-ms duration of the tone; response magnitude did increase monotonically with increasing tone level. When a wideband noise was presented alone, nSFOAE magnitude increased over the initial 100- to 200-ms portion of the 400-ms duration of the noise. When the tone and the wideband noise were presented simultaneously, nSFOAE magnitude decreased momentarily, then increased substantially for about the first 100 ms and then remained strong for the remainder of the presentation. Manipulations of the noise bandwidth revealed that the low-frequency components were primarily responsible for this rising, dynamic response; no rising segment was seen with bandpass or highpass noise. The rising, dynamic nSFOAE response is likely attributable to activation of the medial olivocochlear efferent system. This perstimulatory emission appears to have the potential to provide information about the earliest stages of auditory processing for stimuli commonly used in psychoacoustical tasks.
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Project description:In response to an external stimulus, the cochlea emits sounds, called stimulus frequency otoacoustic emissions (SFOAEs), at the stimulus frequency. In this article, a three-dimensional computational model of the gerbil cochlea is used to simulate SFOAEs and clarify their generation mechanisms and characteristics. This model includes electromechanical feedback from outer hair cells (OHCs) and cochlear roughness due to spatially random inhomogeneities in the OHC properties. As in the experiments, SFOAE simulations are characterized by a quasiperiodic fine structure and a fast varying phase. Increasing the sound pressure level broadens the peaks and decreases the phase-gradient delay of SFOAEs. A state-space formulation of the model provides a theoretical framework to analyze the link between the fine structure and global modes of the cochlea, which arise as a result of standing wave resonances. The SFOAE fine structure peaks correspond to weakly damped resonant modes because they are observed at the frequencies of nearly unstable modes of the model. Variations of the model parameters that affect the reflection mechanism show that the magnitude and sharpness of the tuning of these peaks are correlated with the modal damping ratio of the nearly unstable modes. The analysis of the model predictions demonstrates that SFOAEs originate from the peak of the traveling wave.
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Project description:A hearing sensation arises when the elastic basilar membrane inside the cochlea vibrates. The basilar membrane is typically set into motion through airborne sound that displaces the middle ear and induces a pressure difference across the membrane. A second, alternative pathway exists, however: stimulation of the cochlear bone vibrates the basilar membrane as well. This pathway, referred to as bone conduction, is increasingly used in headphones that bypass the ear canal and the middle ear. Furthermore, otoacoustic emissions, sounds generated inside the cochlea and emitted therefrom, may not involve the usual wave on the basilar membrane, suggesting that additional cochlear structures are involved in their propagation. Here we describe a novel propagation mode within the cochlea that emerges through deformation of the cochlear bone. Through a mathematical and computational approach we demonstrate that this propagation mode can explain bone conduction as well as numerous properties of otoacoustic emissions.
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Project description:Otoacoustic emissions, sounds generated in the inner ear, have become a convenient non-invasive tool to examine the efferent modulation of cochlear mechanics. Activation of the medial olivocochlear (MOC) efferents has been shown to alter the magnitude of these emissions. When the effects of efferent activation on the detailed spectral structures of these emissions have been examined, a shift of the spectral patterns toward higher frequencies has been reported for distortion product and spontaneous otoacoustic emissions. Stimulus frequency otoacoustic emissions (SFOAEs) have been proposed as the preferred emission type in the study of efferent modulation due to the simplicity of their production leading to the possibility of clearer interpretation of results. The effects of efferent activation on the complex spectral patterns of SFOAEs have not been examined to the best of our knowledge. We have examined the effects of activating the MOC efferents using broadband noise in normal-hearing humans. The detailed spectral structure of SFOAEs, known as fine structure, was recorded with and without contralateral acoustic stimulation. Results indicate that SFOAEs are reduced in magnitude and their fine structure pushed to higher frequencies by contralateral acoustic stimulation. These changes are similar to those observed in distortion product or spontaneous otoacoustic emissions and behavioral hearing thresholds. Taken together with observations made about magnitude and phase changes in otoacoustic emissions and hearing thresholds upon contralateral acoustic stimulation, all changes in otoacoustic emission and hearing threshold fine structure appear to be driven by a common set of mechanisms. Specifically, frequency shifts in fine structure patterns appear to be linked to changes in SFOAE phase due to contralateral acoustic stimulation.
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Project description:To explore the audiological characteristics of infant auditory neuropathy (AN) patients with cochlear microphonic (CM) recorded but absent otoacoustic emission (OAE), clinically reducing the rate of missed diagnosis of AN. We retrospectively analyzed the audiological characteristics of infant AN patients in our medical center between 2003 and 2020. A total of 18 infant AN patients were OAE absent group, with CM present and distortion product otoacoustic emission (DPOAE) absent in both ears. A total of 44 infant AN patients were OAE present group, with CM and DPOAE present in both ears. (1) The found age in OAE absent group was 0.9 (0.02) years old, which was younger than 1.11 (1.63) years old in OAE present group (p = .041). (2) The CM threshold of OAE absent group was 80 (10) dB nHL, which was significantly higher (p < .001) than OAE present group. CM amplitude were smaller (p < .05), and CM duration were shorter (p < .05) in OAE absent group. (3) The thresholds of auditory steady-state response (ASSR) at 0.5, 1, 2, and 4 kHz were 94 (10), 94 (10), 87 (20), and 81 (10) dB HL cg, respectively in OAE absent group, which were higher than those in OAE present group (p < .01). Infant AN patients with CM present and OAE absent showed earlier detection and different audiological performance, which was manifested in ASSR thresholds, audiometric configurations and CM performance. CM thresholds were increased, amplitude and duration were decreased, non-linearity of I/O function was reduced. 4.
| S-EPMC9764789 | biostudies-literature
Project description:Objective The virus called SARS-CoV-2, which is known as the first epidemic of the twenty-first century, is known to affect the central and peripheral nervous system. In the literature, complaints of sudden hearing loss, tinnitus, and vertigo have been reported in the patients. The aim of this study is to objectively reveal the effect of the coronavirus disease 2019 on the efferent auditory system. Methods Twenty-three participants, who had the coronavirus disease 2019, were included in the study group, while 20 healthy participants were included in the control group. The test of transient otoacoustic emissions with contralateral suppression was applied to individuals who had normal audiological and immitansmetric evaluations findings. Results In audiological evaluation, a significant difference was observed between the groups in the 125–500 Hz low frequency range and 4 kHz–12.5 kHz high frequency range. In the test of TEOAE and TEOAE with contralateral suppression, a significant difference was observed between the groups at 4 kHz. Conclusion The effect of the coronavirus disease 2019 on the peripheral hearing system has been shown. Its effect on the efferent hearing system in the high frequency region has been revealed. Supplementary Information The online version contains supplementary material available at 10.1186/s43163-022-00231-z.
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