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Moleti A, Minniti T, Sharma Y, Russo A, Civiero A, Orlando MP, MacGregor R, Lucertini M, D'Amico A, Pennazza G, Santonico M, Zompanti A, Crisafi A, Deffacis M, Sapone R, Mascetti G, Vadrucci M, Valentini G, Castagnolo D, Botti T, Cerini L, Sanjust F, Sisto R. Otoacoustic Estimate of Astronauts' Intracranial Pressure Changes During Spaceflight. J Assoc Res Otolaryngol 2024:10.1007/s10162-024-00962-1. [PMID: 39271581 DOI: 10.1007/s10162-024-00962-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Accepted: 08/10/2024] [Indexed: 09/15/2024] Open
Abstract
PURPOSE To investigate the potential correlation between prolonged exposure to microgravity on the International Space Station and increased intracranial fluid pressure, which is considered a risk factor for the astronauts' vision, and to explore the feasibility of using distortion product otoacoustic emissions as a non-invasive in-flight monitor for intracranial pressure changes. METHODS Distortion product otoacoustic emission phase measurements were taken from both ears of five astronauts pre-flight, in-flight, and post-flight. These measurements served as indirect indicators of intracranial pressure changes, given their high sensitivity to middle ear transmission alterations. The baseline pre-flight ground measurements were taken in the seated upright position. RESULTS In-flight measurements revealed a significant systematic increase in otoacoustic phase, indicating elevated intracranial pressure during spaceflight compared to seated upright pre-flight ground baseline. Noteworthy, in two astronauts, strong agreement was also observed between the time course of the phase changes measured in the two ears during and after the mission. Reproducibility and stability of the probe placement in the ear canal were recognized as a critical issue. CONCLUSIONS The study suggests that distortion product otoacoustic emissions hold promise as a non-invasive tool for monitoring intracranial pressure changes in astronauts during space missions. Pre-flight measurements in different body postures and probe fitting strategies based on the individual ear morphology are needed to validate and refine this approach.
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Affiliation(s)
- Arturo Moleti
- Department of Physics, University of Rome Tor Vergata, Rome, Italy
| | | | - Yoshita Sharma
- Department of Physics, University of Rome Tor Vergata, Rome, Italy.
| | - Altea Russo
- Department of Physics, University of Rome Tor Vergata, Rome, Italy
| | | | | | - Robert MacGregor
- Airbus US Space and Defense, Inc. and, NASA Johnson Space Center , Houston, TX, USA
| | - Marco Lucertini
- Italian Air Force-Aerospace Medicine Dept., Experimental Aerospace Division, Rome, Italy
| | - Arnaldo D'Amico
- Department of Electronic Engineering, University of Rome Tor Vergata, Rome, Italy
| | | | | | | | | | | | | | | | | | | | | | - Teresa Botti
- INAIL Research, DIMEILA, Monte Porzio Catone (Rome), Italy
| | - Luigi Cerini
- INAIL Research, DIMEILA, Monte Porzio Catone (Rome), Italy
| | | | - Renata Sisto
- INAIL Research, DIMEILA, Monte Porzio Catone (Rome), Italy
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Moleti A. Optimal Scale-Invariant Wavelet Representation and Filtering of Human Otoacoustic Emissions. J Assoc Res Otolaryngol 2024; 25:329-340. [PMID: 38789824 PMCID: PMC11349967 DOI: 10.1007/s10162-024-00943-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Accepted: 03/04/2024] [Indexed: 05/26/2024] Open
Abstract
Otoacoustic emissions (OAEs) are generated in the cochlea and recorded in the ear canal either as a time domain waveform or as a collection of complex responses to tones in the frequency domain (Probst et al. J Account Soc Am 89:2027-2067, 1991). They are typically represented either in their original acquisition domain or in its Fourier-conjugated domain. Round-trip excursions to the conjugated domain are often used to perform filtering operations in the computationally simplest way, exploiting the convolution theorem. OAE signals consist of the superposition of backward waves generated in different cochlear regions by different generation mechanisms, over a wide frequency range. The cochlear scaling symmetry (cochlear physics is the same at all frequency scales), which approximately holds in the human cochlea, leaves its fingerprints in the mathematical properties of OAE signals. According to a generally accepted taxonomy (Sher and Guinan Jr, J Acoust Soc Am 105:782-798, 1999), OAEs are generated either by wave-fixed sources, moving with frequency according with the cochlear scaling (as in nonlinear distortion) or by place-fixed sources (as in coherent reflection by roughness). If scaling symmetry holds, the two generation mechanisms yield OAEs with different phase gradient delay: almost null for wave-fixed sources, and long (and scaling as 1/f) for place-fixed sources. Thus, the most effective representation of OAE signals is often that respecting the cochlear scale-invariance, such as the time-frequency domain representation provided by the wavelet transform. In the time-frequency domain, the elaborate spectra or waveforms yielded by the superposition of OAE components from different generation mechanisms assume a much clearer 2-D pattern, with each component localized in a specific and predictable region. The wavelet representation of OAE signals is optimal both for visualization purposes and for designing filters that effectively separate different OAE components, improving both the specificity and the sensitivity of OAE-based applications. Indeed, different OAE components have different physiological meanings, and filtering dramatically improves the signal-to-noise ratio.
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Affiliation(s)
- Arturo Moleti
- Department of Physics and NAST Centre - University of Rome 'Tor Vergata', Rome, Italy.
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Distortion Product Otoacoustic Emission Component Behavior as a Function of Primary Frequency Ratio and Primary Level. Ear Hear 2022; 43:1824-1835. [PMID: 35853351 PMCID: PMC9588520 DOI: 10.1097/aud.0000000000001251] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVES Distortion product otoacoustic emissions (DPOAEs) are composed of distortion and reflection components. Much is known about the influence of the stimulus frequency ratio (f 2 /f 1 ) on the overall/composite DPOAE level. However, the influence of f 2 /f 1 on individual DPOAE components is not as well examined. The goals of this pilot study were to systematically evaluate the effects of f 2 /f 1 on DPOAE components in clinically normal-hearing young adult ears. To extend the limited reports in the literature, this examination was carried out over an extended frequency range using two stimulus-level combinations. DESIGN DPOAEs were recorded from seven normal-hearing, young adult ears for f 2 frequencies between 0.75 and 16 kHz over a range of f 2 /f 1 using two stimulus-level combinations. The distortion (DPOAE D ) and reflection (DPOAE R ) components were separated using an inverse fast Fourier transform algorithm. Optimal ratios for the composite DPOAE and DPOAE components were determined from smoothed versions of level versus ratio functions in each case. RESULTS The optimal ratio for the composite DPOAE level increased with stimulus level and decreased as a function of frequency above 1 kHz. The optimal ratios for the DPOAE components followed a similar trend, decreasing with increasing frequency. The optimal ratio for DPOAE D was generally higher than that for DPOAE R . The overall level for DPOAE D was greater than that of DPOAE R , both decreasing with increasing frequency. DPOAE R , but not DPOAE D , became unrecordable above the noise floor at the higher frequencies. CONCLUSIONS DPOAE components behave similarly but not identically as a function of f 2 /f 1 . The ear canal DPOAE is generally dominated by DPOAE D . The behavior of DPOAE D as a function of f 2 /f 1 is entirely consistent with known properties of cochlear mechanics. The behavior of DPOAE R is more variable across ears, perhaps reflective of the increased number of parameters that influence its final form. Attempting to use an f 2 /f 1 that would allow a greater bias of the ear canal DPOAE toward one component or the other does not appear to be practical.
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Sisto R, Moleti A. Low-passed outer hair cell response and apical-basal transition in a nonlinear transmission-line cochlear model. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 149:1296. [PMID: 33639784 DOI: 10.1121/10.0003569] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Accepted: 02/01/2021] [Indexed: 06/12/2023]
Abstract
The low-pass characteristic of the outer hair cell (OHC) voltage response to mechanical stimulation could be considered a serious problem for cochlear models aiming at explaining high-frequency active amplification by introducing instantaneous nonlinear terms because active gain would dramatically decrease at high frequency. Evidence from experimental studies by Nam and Fettiplace [(2012). PloS One 7, e50572] suggests that the local cutoff frequency significantly increases approaching the cochlear base, somehow mitigating this problem. In this study, low-pass filtering of an internal force term, derived from a physiologically plausible OHC schematization by Lu, Zhak, Dallos, and Sarpeshkar [(2006). Hear. Res. 214, 45-67] is included in a simple one-dimensional (1-D) two-degrees-of-freedom transmission-line model by Sisto, Shera, Altoè, and Moleti [(2019). J. Acoust. Soc. Am. 146, 1685-1695] The frequency dependence of the low-pass filter phase-shift naturally yields a transition from sharp tuning and wide dynamical gain range in the basal cochlea to low tuning and poor dynamical range in the apical region. On the other hand, the frequency-dependent attenuation of low-pass filtering makes it more difficult to obtain the high gain (40-50 dB) of the basal basilar membrane response that is experimentally measured in mammals at low stimulus levels. Pressure focusing in the short-wave resonant region, which is not accounted for in this 1-D model, may help in acquiring the additional gain necessary to match the experimental data.
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Affiliation(s)
- Renata Sisto
- Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Istituto Nazionale per l'Assicurazione contro gli Infortuni sul Lavoro, Via di Fontana Candida, 1, 00078 Monte Porzio Catone, Rome, Italy
| | - Arturo Moleti
- Physics Department, University of Roma Tor Vergata, Via della Ricerca Scientifica, 1, 00133 Rome, Italy
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Christensen AT, Shera CA, Abdala C. Extended low-frequency phase of the distortion-product otoacoustic emission in human newborns. JASA EXPRESS LETTERS 2021; 1:014404. [PMID: 33589887 PMCID: PMC7850017 DOI: 10.1121/10.0003192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 10/22/2020] [Indexed: 06/12/2023]
Abstract
At constant f 2 / f 1 ratios, the phase of the nonlinear distortion component of the 2 f 1 - f 2 distortion-product otoacoustic emission (DPOAE) has a steep low-frequency segment and a flat high-frequency segment in adults and newborns. In adults, recent work found that a third segment characterizes the phase at even lower frequencies. The present study tests whether the same is true of the newborn DPOAE phase. Newborn and adult phase curves are generally similar. However, as previously reported, phase-gradient delays at mid frequencies (the region of steepest phase slope) are 50% longer in newborns.
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Affiliation(s)
- Anders T Christensen
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
| | - Christopher A Shera
- Caruso Department of Otolaryngology and Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90033, USA , ,
| | - Carolina Abdala
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
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Guinan JJ. The interplay of organ-of-Corti vibrational modes, not tectorial- membrane resonance, sets outer-hair-cell stereocilia phase to produce cochlear amplification. Hear Res 2020; 395:108040. [PMID: 32784038 PMCID: PMC7502208 DOI: 10.1016/j.heares.2020.108040] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 01/27/2023]
Abstract
The mechanical motions that deflect outer-hair-cell (OHC) stereocilia and the resulting effects of OHC motility are reviewed, concentrating on high-frequency cochlear regions. It has been proposed that a tectorial-membrane (TM) resonance makes the phase of OHC stereocilia motion be appropriate to produce cochlear amplification, i.e. so that the OHC force that pushes the basilar membrane (BM) is in the same direction as BM velocity. Evidence for and against the TM-resonance hypothesis are considered, including new cochlear-motion measurements using optical coherence tomography, and it is concluded that there is no such TM resonance. The evidence points to there being an advance in the phase of reticular lamina (RL) radial motion at a frequency approximately ½ octave below the BM characteristic frequency, and that this is the main source of the phase difference between the TM and RL radial motions that produces cochlear amplification. It appears that the change in phase of RL radial motion comes about because of a transition between different organ-of-Corti (OoC) vibrational modes that changes RL motion relative to BM and TM motion. The origins and consequences of the large phase change of RL radial motion relative to BM motion are considered; differences in the reported patterns of these changes may be due to different viewing angles. Detailed motion data and new models are needed to better specify the vibrational patterns of the OoC modes and the role of the various OoC structures in producing the modes and the mode transition.
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Affiliation(s)
- John J Guinan
- Eaton-Peabody Lab, Mass. Eye and Ear, 243 Charles St, Boston, MA, 02114, USA; Harvard Medical School, Dept. of Otolaryngology, Boston, MA, USA.
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Christensen AT, Abdala C, Shera CA. A cochlea with three parts? Evidence from otoacoustic emission phase in humans. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 148:1585. [PMID: 33003861 PMCID: PMC7789857 DOI: 10.1121/10.0001920] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/14/2020] [Accepted: 08/19/2020] [Indexed: 06/11/2023]
Abstract
The apical and basal regions of the cochlea appear functionally distinct. In humans, compelling evidence for an apical-basal transition derives from the phase of otoacoustic emissions (OAEs), whose frequency dependence differs at low and high frequencies. Although OAEs arising from the two major source mechanisms (distortion and reflection) both support the existence of an apical-basal transition-as identified via a prominent bend (or "break") in OAE phase slope-the two OAE types disagree about its precise location along the cochlea. Whereas distortion OAEs at frequency 2f1-f2 suggest that the apical-basal transition occurs near the 2.5 kHz place, reflection OAEs locate the transition closer to 1 kHz. To address this discrepancy, distortion and reflection OAEs were measured and analyzed in 20 young human adults from 0.25-8 kHz and at eight primary-frequency ratios f2/f1 in the range 1-1.5. Break frequencies and OAE phase-gradient delays were estimated by fitting segmented linear models to the unwrapped phase. When distortion- and reflection-OAE phase are considered as functions of ln f2-that is, as linear functions of the location of their putative site of generation within the cochlea-the analysis identifies not just two but three main cochlear segments, meeting at transition frequencies of approximately 0.9 and 2.6 kHz, whose locations are largely independent both of primary-frequency ratio and emission type. A simple model incorporating an abrupt transition from wave- to place-fixed behavior near the middle of the cochlea accounts for key features of distortion-OAE phase.
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Affiliation(s)
- Anders T Christensen
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
| | - Carolina Abdala
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
| | - Christopher A Shera
- Caruso Department of Otolaryngology, University of Southern California, Los Angeles, California 90033, USA
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Moleti A, Sisto R, Shera CA. Introducing Causality Violation for Improved DPOAE Component Unmixing. AIP CONFERENCE PROCEEDINGS 2018; 1965. [PMID: 30089934 DOI: 10.1063/1.5038497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The DPOAE response consists of the linear superposition of two components, a nonlinear distortion component generated in the overlap region, and a reflection component generated by roughness in the DP resonant region. Due to approximate scaling symmetry, the DPOAE distortion component has approximately constant phase. As the reflection component may be considered as a SFOAE generated by the forward DP traveling wave, it has rapidly rotating phase, relative to that of its source, which is also equal to the phase of the DPOAE distortion component. This different phase behavior permits effective separation of the DPOAE components (unmixing), using time-domain or time-frequency domain filtering. Departures from scaling symmetry imply fluctuations around zero delay of the distortion component, which may seriously jeopardize the accuracy of these filtering techniques. The differential phase-gradient delay of the reflection component obeys causality requirements, i.e., the delay is positive only, and the fine-structure oscillations of amplitude and phase are correlated to each other, as happens for TEOAEs and SFOAEs relative to their stimulus phase. Performing the inverse Fourier (or wavelet) transform of a modified DPOAE complex spectrum, in which a constant phase function is substituted for the measured one, the time (or time-frequency) distribution shows a peak at (exactly) zero delay and long-latency specular symmetric components, with a modified (positive and negative) delay, which is that relative to that of the distortion component in the original response. Component separation, applied to this symmetrized distribution, becomes insensitive to systematic errors associated with violation of the scaling symmetry in specific frequency ranges.
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Affiliation(s)
- Arturo Moleti
- Physics Department, University of Roma Tor Vergata, Roma, Italy
| | - Renata Sisto
- INAIL Research, Department of Monte Porzio Catone (RM), Italy
| | - Christopher A Shera
- Caruso Department of Otolaryngology, Keck School of Medicine, University of Southern California, Los Angeles (CA), USA
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Lichtenhan JT, Lee C, Dubaybo F, Wenrich KA, Wilson US. The Auditory Nerve Overlapped Waveform (ANOW) Detects Small Endolymphatic Manipulations That May Go Undetected by Conventional Measurements. Front Neurosci 2017; 11:405. [PMID: 28769744 PMCID: PMC5513905 DOI: 10.3389/fnins.2017.00405] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 06/29/2017] [Indexed: 11/13/2022] Open
Abstract
Electrocochleography (ECochG) has been used to assess Ménière's disease, a pathology associated with endolymphatic hydrops and low-frequency sensorineural hearing loss. However, the current ECochG techniques are limited for use at high-frequencies only (≥1 kHz) and cannot be used to assess and understand the low-frequency sensorineural hearing loss in ears with Ménière's disease. In the current study, we use a relatively new ECochG technique to make measurements that originate from afferent auditory nerve fibers in the apical half of the cochlear spiral to assess effects of endolymphatic hydrops in guinea pig ears. These measurements are made from the Auditory Nerve Overlapped Waveform (ANOW). Hydrops was induced with artificial endolymph injections, iontophoretically applied Ca2+ to endolymph, and exposure to 200 Hz tones. The manipulations used in this study were far smaller than those used in previous investigations on hydrops. In response to all hydropic manipulations, ANOW amplitude to moderate level stimuli was markedly reduced but conventional ECochG measurements of compound action potential thresholds were unaffected (i.e., a less than 2 dB threshold shift). Given the origin of the ANOW, changes in ANOW amplitude likely reflect acute volume disturbances accumulate in the distensible cochlear apex. These results suggest that the ANOW could be used to advance our ability to identify initial stages of dysfunction in ears with Ménière's disease before the pathology progresses to an extent that can be detected with conventional measures.
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Affiliation(s)
- Jeffery T Lichtenhan
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Choongheon Lee
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Farah Dubaybo
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Kaitlyn A Wenrich
- Department of Otolaryngology Washington University School of MedicineSaint Louis, MO, United States
| | - Uzma S Wilson
- Department of Communication Sciences and Disorders, Northwestern UniversityEvanston, IL, United States
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