Department of Biomedical Engineering, Hearing Research Center, Boston University, 44 Cummington Street, Boston, MA 02215.
Department of Mechanical Engineering, Boston University, 110 Cummington Street, Boston, MA 02215.
J Biomech Eng. 2020 Aug 1;142(8). doi: 10.1115/1.4046637.
We study the vibration modes of a short section in the middle turn of the gerbil cochlea including both longitudinal and radial interstitial fluid spaces between the pillar cells (PC) and the sensory hair cells to determine the role of the interstitial fluid flow within the organ of corti (OoC). Three detailed finite element (FE) models of the cochlear short section (CSS) are studied. In model 1, the CSS is without fluids; model 2 includes the OoC fluid, but not the exterior scalae fluids; and model 3 is the CSS with both scalae and OoC fluids. We find that: (1) the fundamental mode shape of models 1 or 3 is similar to the classical basilar membrane (BM) bending mode that includes pivoting of the arch of corti, and hence determines the low frequency vibrational mode shape of the cochlea in the presence of the cochlear wave. (2) The fundamental mode shape of model 2 is characterized by a cross-sectional shape change similar to the passive response of the cochlea. This mode shape includes a tilting motion of the inner hair cell (IHC) region, a fluid motion within the tunnel of corti (ToC) in the radial direction and along the OoC, and a bulging motion of the reticular lamina (RL) above the outer hair cell (OHC). Each of these motions provides a plausible mode of excitation of the sensory hair cells. (3) The higher vibrational modes of model 1 are similar to the electrically evoked response within the OoC and suggests that the higher vibrational modes are responsible for the active response of the cochlea. We also observed that the fluid flow through the OoC interstitial space is significant, and the model comparison suggests that the OoC fluid contributes to the biphasic BM motion seen in electrical stimulation experiments. The effect of fluid viscosity on cilium deflection was assessed by performing a transient analysis to calculate the cilium shearing gain. The gain values are found to be within the range of experimentally measured values reported by Dallos et al. (1996, The Cochlea, Springer-Verlag, New York).
我们研究了沙鼠耳蜗中段短节中的振动模式，包括柱细胞（PC）和感觉毛细胞之间的纵向和径向细胞间隙中的间质流体，以确定耳蜗器官内间质流体流动的作用（OoC）。研究了三个详细的耳蜗短节（CSS）有限元（FE）模型。在模型 1 中，CSS 没有流体；模型 2 包括 OoC 流体，但不包括外部 scala 流体；模型 3 是带有 scala 和 OoC 流体的 CSS。我们发现：（1）模型 1 或 3 的基本模态形状类似于经典的基底膜（BM）弯曲模态，包括耳蜗嵴的枢轴转动，因此在存在耳蜗波的情况下决定了耳蜗的低频振动模态形状。（2）模型 2 的基本模态形状的特点是类似于耳蜗的被动响应的横截面形状变化。这种模态形状包括内毛细胞（IHC）区域的倾斜运动、在 Corti 隧道（ToC）中的径向和沿 OoC 的流体运动以及网状层（RL）在外毛细胞（OHC）上方的凸起运动。这些运动中的每一个都为感觉毛细胞的激发提供了一种合理的模式。（3）模型 1 的较高振动模式类似于 OoC 内的电诱发响应，表明较高振动模式负责耳蜗的主动响应。我们还观察到，OoC 间质空间中的流体流动是显著的，模型比较表明，OoC 流体有助于在电刺激实验中观察到的双相 BM 运动。通过进行瞬态分析来计算纤毛剪切增益，评估了流体粘度对纤毛偏斜的影响。增益值被发现处于 Dallos 等人（1996，The Cochlea，Springer-Verlag，New York）报道的实验测量值范围内。
