A role for tectorial membrane mechanics in activating the cochlear amplifier.
A role for tectorial membrane mechanics in activating the cochlear amplifier.
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DOI：
10.1038/s41598-020-73873-9
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发表时间：
2020-10-19
影响因子：
4.6
通讯作者：
Grosh K
中科院分区：
文献类型：
--
作者：
Nankali A;Wang Y;Strimbu CE;Olson ES;Grosh K
哺乳动物耳蜗对声刺激的机械和电响应是非线性的，并且在频率上高度调谐。这是由于耳蜗外毛细胞（OHC）的机电特性。在沿耳蜗螺旋沿着的每个位置处，OHC介导主动过程，其中感觉组织运动在接近最敏感频率（称为特征频率，CF）的频率处增强。先前的实验结果表明，OHC产生的细胞外电压相对于基底膜位移的约0.3个周期的相移，其在比CF低约半个倍频程的频率下开始。本文件的调查结果加强了这一结果。这种偏移是显著的，因为它使OHC衍生的电动力的相位接近于在偏移以上的频率处的基底膜速度的相位，从而使得能够在基底膜处将电功率转移到机械功率。为了寻求这种现象的候选物理机制，我们使用了一个全面的机电数学模型的耳蜗对声音的反应。该模型预测的相移参考基底膜的细胞外电压在一个频率约半倍频程低于CF，根据实验数据。在该模型中，该特征源于覆膜及其角膜缘附着的径向阻抗的最小值。这些实验和理论结果与以下假设一致：覆膜共振在用于发电的机械响应和电响应之间引入正确的定相，从而有效地打开耳蜗放大器。
The mechanical and electrical responses of the mammalian cochlea to acoustic stimuli are nonlinear and highly tuned in frequency. This is due to the electromechanical properties of cochlear outer hair cells (OHCs). At each location along the cochlear spiral, the OHCs mediate an active process in which the sensory tissue motion is enhanced at frequencies close to the most sensitive frequency (called the characteristic frequency, CF). Previous experimental results showed an approximate 0.3 cycle phase shift in the OHC-generated extracellular voltage relative the basilar membrane displacement, which was initiated at a frequency approximately one-half octave lower than the CF. Findings in the present paper reinforce that result. This shift is significant because it brings the phase of the OHC-derived electromotile force near to that of the basilar membrane velocity at frequencies above the shift, thereby enabling the transfer of electrical to mechanical power at the basilar membrane. In order to seek a candidate physical mechanism for this phenomenon, we used a comprehensive electromechanical mathematical model of the cochlear response to sound. The model predicts the phase shift in the extracellular voltage referenced to the basilar membrane at a frequency approximately one-half octave below CF, in accordance with the experimental data. In the model, this feature arises from a minimum in the radial impedance of the tectorial membrane and its limbal attachment. These experimental and theoretical results are consistent with the hypothesis that a tectorial membrane resonance introduces the correct phasing between mechanical and electrical responses for power generation, effectively turning on the cochlear amplifier.
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