Department of Mechanical Engineering, University of Rochester, Rochester, New York.
Department of Mechanical Engineering, University of Rochester, Rochester, New York; Department of Biomedical Engineering, University of Rochester, Rochester, New York.
Biophys J. 2019 Apr 2;116(7):1362-1375. doi: 10.1016/j.bpj.2019.02.022. Epub 2019 Mar 1.
The cochlear cavity is filled with viscous fluids, and it is partitioned by a viscoelastic structure called the organ of Corti complex. Acoustic energy propagates toward the apex of the cochlea through vibrations of the organ of Corti complex. The dimensions of the vibrating structures range from a few hundred (e.g., the basilar membrane) to a few micrometers (e.g., the stereocilia bundle). Vibrations of microstructures in viscous fluid are subjected to energy dissipation. Because the viscous dissipation is considered to be detrimental to the function of hearing-sound amplification and frequency tuning-the cochlea uses cellular actuators to overcome the dissipation. Compared to extensive investigations on the cellular actuators, the dissipating mechanisms have not been given appropriate attention, and there is little consensus on damping models. For example, many theoretical studies use an inviscid fluid approximation and lump the viscous effect to viscous damping components. Others neglect viscous dissipation in the organ of Corti but consider fluid viscosity. We have developed a computational model of the cochlea that incorporates viscous fluid dynamics, organ of Corti microstructural mechanics, and electrophysiology of the outer hair cells. The model is validated by comparing with existing measurements, such as the viscoelastic response of the tectorial membrane, and the cochlear input impedance. Using the model, we investigated how dissipation components in the cochlea affect its function. We found that the majority of acoustic energy dissipation of the cochlea occurs within the organ of Corti complex, not in the scalar fluids. Our model suggests that an appropriate dissipation can enhance the tuning quality by reducing the spread of energy provided by the outer hair cells' somatic motility.
耳蜗腔充满粘性流体，并由称为柯蒂氏器复合体的粘弹性结构分隔。声能通过柯蒂氏器复合体的振动向耳蜗的顶点传播。振动结构的尺寸范围从几百（例如，基底膜）到几微米（例如，纤毛束）。粘性流体中微观结构的振动会受到能量耗散的影响。由于粘性耗散被认为对听觉放大和频率调谐的功能有害，耳蜗使用细胞执行器来克服耗散。与对细胞执行器的广泛研究相比，耗散机制并未得到适当关注，阻尼模型也没有达成共识。例如，许多理论研究使用无粘流近似并将粘性效应归并为粘性阻尼分量。其他研究忽略了柯蒂氏器中的粘性耗散，但考虑了流体粘度。我们已经开发了一个耳蜗的计算模型，该模型结合了粘性流体动力学、柯蒂氏器微观结构力学和外毛细胞的电生理学。该模型通过与现有的测量结果（例如，盖膜的粘弹性响应和耳蜗输入阻抗）进行比较来验证。使用该模型，我们研究了耳蜗中的耗散成分如何影响其功能。我们发现，耳蜗的大部分声能耗散发生在柯蒂氏器复合体内部，而不是在标量流体中。我们的模型表明，适当的耗散可以通过减少外毛细胞体运动提供的能量扩散来提高调谐质量。
