Gummer A W, Hemmert W, Zenner H P
Department of Otolaryngology, University of Tübingen, Germany.
Proc Natl Acad Sci U S A. 1996 Aug 6;93(16):8727-32. doi: 10.1073/pnas.93.16.8727.
The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of the cochlea. In particular, it has been proposed that the tectorial membrane provides a second resonant system, in addition to that of the basilar membrane, which contributes to the amplification of the motion of the cochlear partition. Until now, technical difficulties had prevented vibration measurements of the tectorial membrane and, therefore, precluded direct evidence of a mechanical resonance. In the study reported here, the vibration of the tectorial membrane was measured in two orthogonal directions by using a novel method of combining laser interferometry with a photodiode technique. It is shown experimentally that the motion of the tectorial membrane is resonant at a frequency of 0.5 octave (oct) below the resonant frequency of the basilar membrane and polarized parallel to the reticular lamina. It is concluded that the resonant motion of the tectorial membrane is due to a parallel resonance between the mass of the tectorial membrane and the compliance of the stereocilia of the outer hair cells. Moreover, in combination with the contractile force of outer hair cells, it is proposed that inertial motion of the tectorial membrane provides the necessary conditions to allow positive feedback of mechanical energy into the cochlear partition, thereby amplifying and tuning the cochlear response.
长期以来，人们一直假定覆膜在耳蜗的高灵敏度中发挥作用。具体而言，有人提出，除了基底膜的共振系统外，覆膜还提供了第二个共振系统，这有助于放大耳蜗隔板的运动。到目前为止，技术难题阻碍了对覆膜振动的测量，因此无法获得机械共振的直接证据。在本文报道的研究中，通过一种将激光干涉测量法与光电二极管技术相结合的新方法，在两个正交方向上测量了覆膜的振动。实验表明，覆膜的运动在比基底膜共振频率低0.5倍频程（倍频）的频率处发生共振，且偏振方向与网状板平行。得出的结论是，覆膜的共振运动是由于覆膜质量与外毛细胞静纤毛顺应性之间的平行共振所致。此外，结合外毛细胞的收缩力，有人提出覆膜的惯性运动为机械能向耳蜗隔板的正反馈提供了必要条件，从而放大并调节耳蜗反应。
