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Effects of Specific Cochlear Pathologies on the Auditory Functions: Modelling, Simulations and Clinical Implications
Linköping University, Department of Clinical and Experimental Medicine, Division of Neuroscience. Linköping University, Faculty of Health Sciences.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A hearing impairment is primarily diagnosed by measuring the hearing thresholds at a range of auditory frequencies (air-conduction audiometry). Although this clinical procedure is simple, affordable, reliable and fast, it does not offer differential information about origins of the hearing impairment. The main goal of this thesis is to quantitatively link specific cochlear pathologies to certain changes in the spectral and temporal characteristics of the auditory system. This can help better understand the underlying mechanisms associated with sensorineural hearing impairments, beyond what is shown in the audiogram. Here, an electromechanical signal-transmission model is devised in MATLAB where the parameters of the model convey biological interpretations of mammalian cochlear structures. The model is exploited to simulate the cell-level cochlear pathologies associated with two common types of sensorineural hearing impairments, 1: presbyacusis (age-related hearing impairment) and, 2: noise-induced hearing impairment. Furthermore, a clinical study, consisting of different psychoacoustic and physiological tests, was performed to trace and validate the model predictions in human. The results of the clinical tests were collated and compared with the model predictions, showing a reasonable agreement. In summary, the present model provides a biophysical foundation for simulating the effect of specific cellular lesions, due to different inner-ear diseases and external insults, on the entire cochlear mechanism and thereby on the whole auditory system. This is a multidisciplinary work in the sense that it connects the ‘biological processes’ with ‘acoustic modelling’ and ‘clinical audiology’ in a translational context.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 57 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1400Studies from the Swedish Institute for Disability Research, ISSN 1650-1128 ; 60
Keyword [en]
Auditory modeling, cochlear mechanics, sensorineural hearing impairment, age-related hearing loss, noise-induced hearing loss, inner ear pathologies
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-105810DOI: 10.3384/diss.diva-105810ISBN: 978-91-7519-365-6 (print)OAI: oai:DiVA.org:liu-105810DiVA: diva2:710714
Public defence
2014-04-28, Nils Holger salen, entrance 71, Campus US, Linköpings universitet, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2014-04-08 Created: 2014-04-08 Last updated: 2014-10-08Bibliographically approved
List of papers
1. A physiological Signal Transmission Model to be used for Specific Diagnosis of Cochlear Impairments
Open this publication in new window or tab >>A physiological Signal Transmission Model to be used for Specific Diagnosis of Cochlear Impairments
2011 (English)In: WHAT FIRE IS IN MINE EARS: PROGRESS IN AUDITORY BIOMECHANICS: PROCEEDINGS OF THE 11TH INTERNATIONAL MECHANICS OF HEARING WORKSHOP / [ed] Shera, CA; Olson, ES, American Institute of Physics (AIP), 2011, Vol. 1403, 369-373 p.Conference paper, Published paper (Refereed)
Abstract [en]

Many of the sophisticated characteristics of human auditory system are attributed to cochlea. Also, most of patients with a hearing loss suffer from impairments that originate from cochlea (sensorineural). Despite this, today's clinical diagnostic methods do not probe the specific origins of such cochlear lesions. The aim of this research is to introduce a physiological signal transmission model to be clinically used as a tool for diagnosis of cochlear losses. This model enables simulation of different bio‐mechano‐electrical processes which occur in the auditory organ of Corti inside the cochlea. What makes this model different from many available computational models is its loyalty to physiology since the ultimate goal is to model each single physiological phenomenon. This includes passive BM vibration, outer hair cells' performances such as nonlinear mechanoelectrical transduction (MET), active amplifications by somatic motor, as well as vibration to neural conversion at the inner hair cells.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2011
Keyword
cochlear mechanics, auditory model, cochlear hearing loss, sensorineural, presbyacusis, stria vascularis
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-76599 (URN)10.1063/1.3658113 (DOI)000301945200062 ()
Conference
11th International Workshop on the Mechanics of Hearing, Williams Coll, Williamstown, MA, USA, JUL 16-22, 2011
Projects
HEAD hearing and deafness, IHV
Available from: 2012-04-12 Created: 2012-04-12 Last updated: 2014-10-08
2. The effect of aging on cochlear amplifier: A simulation approach using a physiologically-based electro-mechanical model of the cochlea
Open this publication in new window or tab >>The effect of aging on cochlear amplifier: A simulation approach using a physiologically-based electro-mechanical model of the cochlea
2012 (English)In: Canadian Acoustics, ISSN 0711-6659, E-ISSN 2291-1391, Vol. 40, no 3, 128-129 p.Article in journal (Refereed) Published
Abstract [en]

The electrical, acoustical, and mechanical elements of the cochlea are explicitly integrated into a transmission-line model to develop a physiological interpretation of the human cochlea insofar. The model enables fundamental simulation of specific cochlear lesions such as metabolic presbyacusis. A sound pressure field in the air is transmitted via the outer and middle ear to the inner ear. It causes the stapes to vibrate resulting in a traveling wave along the organ of Corti propagating from base towards apex. As the endocochlear potential (EP) decreases, the MET produces less receptor current which, eventually leading to a decline in the force/displacement generated by the somatic motor. The CFs of the curves tend to move backwards in a presbyacusis cochlea, this result is consistent with Robles and Ruggem where in a passive cochlea, the CFs are shifted backwards.

Place, publisher, year, edition, pages
Canadian Acoustical Association, 2012
Keyword
Acoustics; Audio frequency amplifiers; Computer simulation; Physiology; Cochlear amplifiers; Electromechanical models; Endocochlear potentials; Human cochleas; Inner ear; Mechanical elements; Middle ears; Organ of corti; Simulation approach; Sound pressure field; Transmission line models; Traveling wave
National Category
Neurosciences
Identifiers
urn:nbn:se:liu:diva-94738 (URN)
Available from: 2013-07-01 Created: 2013-07-01 Last updated: 2017-12-06Bibliographically approved
3. Effect of metabolic presbyacusis on cochlear responses: A simulation approach using a physiologically-based model
Open this publication in new window or tab >>Effect of metabolic presbyacusis on cochlear responses: A simulation approach using a physiologically-based model
2013 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 134, no 4, 2833-2851 p.Article in journal (Refereed) Published
Abstract [en]

In the presented model, electrical, acoustical, and mechanical elements of the cochlea are explicitly integrated into a signal transmission line where these elements convey physiological interpretations of the human cochlear structures. As a result, this physiologically-motivated model enables simulation of specific cochlear lesions such as presbyacusis. The hypothesis is that high-frequency hearing loss in older adults may be due to metabolic presbyacusis whereby age-related cellular/chemical degenerations in the lateral wall of the cochlea cause a reduction in the endocochlear potential. The simulations quantitatively confirm this hypothesis and emphasize that even if the outer and inner hair cells are totally active and intact, metabolic presbyacusis alone can significantly deteriorate the cochlear functionality. Specifically, in the model, as the endocochlear potential decreases, the transduction mechanism produces less receptor current such that there is a reduction in the battery of the somatic motor. This leads to a drastic decrease in cochlear amplification and frequency sensitivity, as well as changes in position-frequency map (tuning pattern) of the cochlea. In addition, the simulations show that the age-related reduction of the endocochlear potential significantly inhibits the firing rate of the auditory nerve which might contribute to the decline of temporal resolution in the aging auditory system.

Place, publisher, year, edition, pages
Acoustical Society of America (ASA), 2013
National Category
Otorhinolaryngology Medical Engineering
Identifiers
urn:nbn:se:liu:diva-98271 (URN)10.1121/1.4820788 (DOI)000330119700039 ()
Funder
Swedish Research Council
Available from: 2013-10-07 Created: 2013-10-07 Last updated: 2017-12-06Bibliographically approved
4. Effects of Acoustic Overstimulation and the Associated Cellular Lesions on the Cochlear Amplifier: Simulation Results
Open this publication in new window or tab >>Effects of Acoustic Overstimulation and the Associated Cellular Lesions on the Cochlear Amplifier: Simulation Results
2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

A physiologically-based electromechanical model of the human cochlea is used in this study to explicitly simulate the effects of acoustical overstimulation, and the associated cellular deficiencies, on the gain of the cochlear amplifier. The simulations demonstrate that as the micromechanics of the stereocillia transduction channels is altered due to the traumatic acoustical overstimulation, the compressive/nonlinear behavior of the cochlear amplifier is significantly modified. When the loudness growth is estimated by the integral of the cochlear amplification with respect to the sound intensity, these modifications lead to an impaired loudness function reminiscent of the recruitment phenomenon. Furthermore, when a severe noise-induced loss of outer hair cells is assumed at basal regions of the cochlea, the model predicts a mild loss at lower frequencies followed by a steeply sloping notch-like amplification loss of approximately 80 dB around 4.5 kHz. This prediction is reasonably in line with the threshold elevations observed clinically from the noise-damaged human ears. Moreover, the results quantitatively demonstrate that the center frequency, the width and the depth of the amplification loss are directly determined by the severity and the location of the outer hair cell loss along the cochlear duct.

National Category
Otorhinolaryngology Medical Engineering
Identifiers
urn:nbn:se:liu:diva-105808 (URN)
Available from: 2014-04-08 Created: 2014-04-08 Last updated: 2015-04-01Bibliographically approved
5. Changes in Temporal and Spectral Functions of the Auditory Periphery Due to Aging and Noise-induced Cochlear Pathologies: A Comparative Clinical Study
Open this publication in new window or tab >>Changes in Temporal and Spectral Functions of the Auditory Periphery Due to Aging and Noise-induced Cochlear Pathologies: A Comparative Clinical Study
2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Objective: This study includes a battery of psychoacoustical and electrophysiological tests to quantitatively investigate the changes in the frequency and the temporal features of the human auditory periphery caused by aging (presbyacusis) and noise-induced lesions, two common types of sensorineural hearing impairments. The scores are comparatively analyzed.

Design: These clinical experiments have been implemented in MATLAB software.

Study sample: 20 normal hearing adults (aged 30-54), 20 older hearing-impaired subjects (aged 65-70) with no history of Ototoxic medication or noise exposure and 7 adult men with a traceable noise-induced hearing impairment.

Results: The observed temporal and spectral declines are generally consistent with the high-frequency audiometric loss depicted by the audiogram, for each group. Moreover, the test battery provides valuable information on the frequency sensitivity, temporal resolution, loudness growth, compression and otoacoustic emissions.

Conclusion: These scores are compared with the predictions of a physiologicallybased cochlear model to provide evidence about specific inner-ear pathologies, beyond what the audiogram can indicate. Among these 7 clinical experiments, the results from the forward temporal masking test, the categorical loudness discrimination test and the distortion product otoacoustic emission test provide the most differential information about the underlying cellular lesions. The results indicate that the reduction in the temporal resolution is substantially age-relate since the presbyacusis listeners, unlike the other groups, obtained almost no benefit from the temporal cues provided by the gap duration at any of the experiments. Moreover, the results suggest that the DPOAEs reflect the cellular lesions associated with the acoustic overstimulation rather than the age-related strial degenerations.

Keyword
Inner ear pathologies, Cochlear lesion, Sensorineural hearing impairment, Auditory models
National Category
Otorhinolaryngology Medical Engineering
Identifiers
urn:nbn:se:liu:diva-105809 (URN)
Available from: 2014-04-08 Created: 2014-04-08 Last updated: 2015-04-01Bibliographically approved

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