Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.
J Assoc Res Otolaryngol. 2012 Apr;13(2):185-97. doi: 10.1007/s10162-011-0308-x.
We use analysis of a realistic three-dimensional finite-element model of the tunnel of Corti (ToC) in the middle turn of the gerbil cochlea tuned to the characteristic frequency (CF) of 4 kHz to show that the anatomical structure of the organ of Corti (OC) is consistent with the hypothesis that the cochlear amplifier functions as a fluid pump. The experimental evidence for the fluid pump is that outer hair cell (OHC) contraction and expansion induce oscillatory flow in the ToC. We show that this oscillatory flow can produce a fluid wave traveling in the ToC and that the outer pillar cells (OPC) do not present a significant barrier to fluid flow into the ToC. The wavelength of the resulting fluid wave launched into the tunnel at the CF is 1.5 mm, which is somewhat longer than the wavelength estimated for the classical traveling wave. This fluid wave propagates at least one wavelength before being significantly attenuated. We also investigated the effect of OPC spacing on fluid flow into the ToC and found that, for physiologically relevant spacing between the OPCs, the impedance estimate is similar to that of the underlying basilar membrane. We conclude that the row of OPCs does not significantly impede fluid exchange between ToC and the space between the row of OPC and the first row of OHC-Dieter's cells complex, and hence does not lead to excessive power loss. The BM displacement resulting from the fluid pumped into the ToC is significant for motion amplification. Our results support the hypothesis that there is an additional source of longitudinal coupling, provided by the ToC, as required in many non-classical models of the cochlear amplifier.
我们使用对中间切迹的真实三维有限元模型分析来调谐到 4 kHz 的特征频率（CF）的沙鼠耳蜗，以显示 Corti 器（OC）的解剖结构与耳蜗放大器作为流体泵的假设一致。流体泵的实验证据是外毛细胞（OHC）的收缩和扩张在外柱细胞（OPC）之间引起振荡流动。我们表明，这种振荡流动可以在外柱细胞之间产生一个在 ToC 中传播的流体波，并且外柱细胞（OPC）不会对流体流入 ToC 形成明显的阻碍。在 CF 处发射到隧道中的流体波的波长为 1.5 毫米，这比经典行波估计的波长稍长。这种流体波传播至少一个波长才会被显著衰减。我们还研究了 OPC 间距对流体流入 ToC 的影响，发现对于 OPC 之间生理相关的间距，阻抗估计与基底膜相似。我们得出结论，OPC 排不会显著阻碍 OPC 排与 OHC-Dieter 细胞复合物的第一排之间的 ToC 和空间之间的流体交换，因此不会导致过度的功率损耗。流体泵入 ToC 引起的 BM 位移对于运动放大非常重要。我们的结果支持了存在额外的纵向耦合源的假设，该源由 ToC 提供，这是许多非经典耳蜗放大器模型所需要的。
