美國科學(xué)家近日發(fā)現(xiàn)了一種全新的聽覺機(jī)制,，從根本上改變了目前對(duì)內(nèi)耳功能的了解,。這一發(fā)現(xiàn)有助于解釋耳非凡的感覺和區(qū)分聲音的能力，并有可能為治療聽力喪失作出貢獻(xiàn),。相關(guān)論文10月9日在線發(fā)表于《美國國家科學(xué)院院刊》（PNAS）上,。
很久以來，科學(xué)家就知道,，在耳蝸內(nèi),，聲波是以上下起伏的波形式沿著基膜進(jìn)行傳輸?shù)摹Ｔ谧钚碌难芯恐?，美國麻省理工學(xué)院研究人員Dennis M. Freeman,、Roozbeh Ghaffari和Alexander J. Aranyosi設(shè)計(jì)了精巧的實(shí)驗(yàn)，對(duì)耳蝸覆膜進(jìn)行了研究,，發(fā)現(xiàn)耳蝸覆膜比之前預(yù)想得要重要的多,。它能選擇性地接收和傳輸聲波能量到耳蝸的不同部位，傳輸方式是一種不同于普通上下起伏波的縱向傳輸,。
這種新的傳輸方式對(duì)于將聽覺信號(hào)輸送給耳蝸覆膜正下方的感覺纖毛細(xì)胞至關(guān)重要,，感覺纖毛細(xì)胞之后會(huì)將信號(hào)傳給大腦。簡要來說,，耳能夠即時(shí)將聲音轉(zhuǎn)化成兩種不同的波動(dòng),，而這兩種波動(dòng)能夠相互作用，刺激感覺纖毛細(xì)胞并加強(qiáng)它們的靈敏性,。研究人員認(rèn)為,，這兩種波動(dòng)的相互作用可能就是我們擁有高保真聽覺的關(guān)鍵所在。
Ghaffari表示,，此次發(fā)現(xiàn)對(duì)于我們理解耳蝸的機(jī)制大有幫助,。從長遠(yuǎn)來看，新的研究對(duì)于助聽器和耳蝸移植技術(shù)的發(fā)展也將產(chǎn)生影響,。Aranyosi認(rèn)為,，這一發(fā)現(xiàn)也將有助于我們更深入地研究某些種類的遺傳性聽覺喪失，因?yàn)橹坝袑?shí)驗(yàn)表明,，這些聽覺喪失的內(nèi)在表現(xiàn)之一就是第二種波動(dòng)的損壞,。（科學(xué)網(wǎng) 梅進(jìn)/編譯）
原始出處:
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
