PubMed · 6142257
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1984-03-10. Tinnitus.. https://pubmed.ncbi.nlm.nih.gov/6142257/
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In the literature on locally active models of the cochlea several forms of the model have been worked out in which elements of the organ of Corti are assumed to produce acoustical energy. In these models use is made of a secondary resonance or a place-dependent delay to achieve activity over a limited part of the length of the basilar membrane, and outer hair cells are postulated as sources of energy production. In the present paper it will be shown that several of these models are formally equivalent. That means that they can be reduced to a standard form, and that the only difference resides in the choice and meaning of the parameters. The results of the analysis serve to facilitate the analysis of function and structure in cochlear models containing sources of local activity. In particular, questions of positive versus negative feedback, and the parts played by resonance and impedance-level differences can be resolved unambiguously. The treatment can be extended to models with higher dimensionality, and can also serve to obtain insight in nonlinear phenomena occurring in cochlear models.
An active nonlinear model of the cochlea in the form of a transmission line was presented, in which the active feedback system by outer hair cells (OHCs) was expressed as a series of low-pass filters on the basilar membrane (BM) which were transducing basilar membrane displacement to feedback force. The model could produce distortion product oto-acoustic emissions (DPOAEs) explicitly as well as sharp tuning curves of BM, and it was possible to discuss the cause of DPOAEs in terms of the active feedback. It was inferred that the nonlinearity of the cochlea which causes DPOAEs may be related to a saturating property of the feedback system by OHCs.
In clinical diagnosis bone conduction thresholds can be used to assess impaired hearing caused by pathological function of the inner ear. The effects of changed mechanical properties of the middle ear on bone conduction are usually not considered in patients who simultaneously suffer from middle ear and inner ear diseases. This procedure is only partially correct. An exact determination of the effects of altered middle ear mechanics on bone conduction in patients with otosclerosis or after middle ear operations is rather difficult, but such determinations can improve diagnostic validity. Therefore, a special electrical model was constructed to simulate the oscillation pattern of the basilar membrane for bone conduction and variable middle ear impedance. Results from the model and possible conclusions on bone conducted hearing in vivo are discussed. Further steps to ensure measurements of inner ear function in cases with modified middle ear mechanics are proposed.