PNAS：听觉新机制有望治疗听力丧失
美国科学家近日发现了一种全新的听觉机制，从根本上改变了目前对内耳功能的了解。这一发现有助于解释耳非凡的感觉和区分声音的能力，并有可能为治疗听力丧失作出贡献。相关论文10月9日在线发表于《美国国家科学院院刊》（PNAS）上。
很久以来，科学家就知道，在耳蜗内，声波是以上下起伏的波形式沿着基膜进行传输的。在最新的研究中，美国麻省理工学院研究人员Dennis M. Freeman、Roozbeh Ghaffari和Alexander J. Aranyosi设计了精巧的实验，对耳蜗覆膜进行了研究，发现耳蜗覆膜比之前预想得要重要的多。它能选择性地接收和传输声波能量到耳蜗的不同部位，传输方式是一种不同于普通上下起伏波的纵向传输。
这种新的传输方式对于将听觉信号输送给耳蜗覆膜正下方的感觉纤毛细胞至关重要，感觉纤毛细胞之后会将信号传给大脑。简要来说，耳能够即时将声音转化成两种不同的波动，而这两种波动能够相互作用，刺激感觉纤毛细胞并加强它们的灵敏性。研究人员认为，这两种波动的相互作用可能就是我们拥有高保真听觉的关键所在。
Ghaffari表示，此次发现对于我们理解耳蜗的机制大有帮助。从长远来看，新的研究对于助听器和耳蜗移植技术的发展也将产生影响。Aranyosi认为，这一发现也将有助于我们更深入地研究某些种类的遗传性听觉丧失，因为之前有实验表明，这些听觉丧失的内在表现之一就是第二种波动的损坏。（科学网 梅进/编译）
原始出处:
Published online before print October 9, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0703665104
Longitudinally propagating traveling waves of the mammalian tectorial membrane
Roozbeh Ghaffari*,
, Alexander J. Aranyosi, and Dennis M. Freeman*,,
,
,¶
*Speech and Hearing Bioscience and Technology Program, Harvard–MIT Division of Health Sciences and Technology, Cambridge, MA 02139; Research Laboratory of Electronics and Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139; and Eaton–Peabody Laboratory of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114
Edited by David P. Corey, Harvard Medical School, Boston, MA, and accepted by the Editorial Board August 27, 2007 (received for review April 23, 2007)
Abstract
Sound-evoked vibrations transmitted into the mammalian cochlea produce traveling waves that provide the mechanical tuning necessary for spectral decomposition of sound. These traveling waves of motion that have been observed to propagate longitudinally along the basilar membrane (BM) ultimately stimulate the mechano-sensory receptors. The tectorial membrane (TM) plays a key role in this process, but its mechanical function remains unclear. Here we show that the TM supports traveling waves that are an intrinsic feature of its visco-elastic structure. Radial forces applied at audio frequencies (2–20 kHz) to isolated TM segments generate longitudinally propagating waves on the TM with velocities similar to those of the BM traveling wave near its best frequency place. We compute the dynamic shear storage modulus and shear viscosity of the TM from the propagation velocity of the waves and show that segments of the TM from the basal turn are stiffer than apical segments are. Analysis of loading effects of hair bundle stiffness, the limbal attachment of the TM, and viscous damping in the subtectorial space suggests that TM traveling waves can occur in vivo. Our results show the presence of a traveling wave mechanism through the TM that can functionally couple a significant longitudinal extent of the cochlea and may interact with the BM wave to greatly enhance cochlear sensitivity and tuning.
cochlear mechanics | dynamic mechanical properties | longitudinal mechanical coupling
相关报道:
- 众说风云 (已有0条评论)
