RESEARCH
Computational modeling of the human auditory periphery and its application to efficient diagnosis and treatment of ear diseases
People with untreated hearing loss have more risk of dementia and depression than people with normal hearing. Pathogenic mechanism of many of refractory ear diseases have not been fully clarified yet, because non-invasive in-vivo observations of those pathologies are difficult. A comprehension of those pathogenic mechanisms is necessary for not only effective treatments but also prophylaxis. For that, it is necessary to clarify the mechanism of each disease theoretically after clarifying the hearing mechanism. The mechanisms should be clarified based on the basis of theoretical study with a model that also considers the activity in the auditory periphery.
Computational modeling of the human auditory periphery
The human auditory periphery has been modeled and the hearing mechanism has been investigated by numerical analysis. The mechanically vibrating parts of the auditory periphery, i.e., the middle ear and the cochlea, were modeled by the finite-element (FE) method (Fig. 1).
Fig. 1 Computational models of the human auditory periphery
Distortion-product otoacoustic emissions (DPOAEs, Fig. 2) are considered to be generated by nonlinear activity of the outer hair cells (OHC) in the cochlea, and those frequencies and levels depend on the shape of the curve of the force. The nonlinear activity of OHC was formulated based on the distortion components detected in measurements of DPOAEs. The FE-model of the human cochlea includes non-linear activities (Fig. 3). The input/output (I/O) functions of DPOAEs obtained from numerical analysis using the finite-element model of the human cochlea which includes the force were compared with the measurements in normal-hearing human ears and validity of the force was evaluated.
Fig. 2 DPOAEs and measurement system
Fig. 3 Formulation of the activity of the cochlea (Left)
and simulation of active model and passive model (Right)
Fig. 4 Simulation of DPOAEs
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The conditions of some ear diseases, i.e., ossicular fixation, change of the tympanic membrane, endolymphatic hydrops and partial functional loss of the OHCs, were represented by modifying the models. In addition to the pathogenic mechanism, effective diagnosis of each disease was also investigated by numerical analysis using the affected models.
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