Manoussaki Daphne, Chadwick Richard S, Ketten Darlene R, Arruda Julie, Dimitriadis Emilios K, O'Malley Jen T
Department of Mathematics, Vanderbilt University, Nashville, TN 37240, USA.
Proc Natl Acad Sci U S A. 2008 Apr 22;105(16):6162-6. doi: 10.1073/pnas.0710037105. Epub 2008 Apr 14.
The conventional theory about the snail shell shape of the mammalian cochlea is that it evolved essentially and perhaps solely to conserve space inside the skull. Recently, a theory proposed that the spiral's graded curvature enhances the cochlea's mechanical response to low frequencies. This article provides a multispecies analysis of cochlear shape to test this theory and demonstrates that the ratio of the radii of curvature from the outermost and innermost turns of the cochlear spiral is a significant cochlear feature that correlates strongly with low-frequency hearing limits. The ratio, which is a measure of curvature gradient, is a reflection of the ability of cochlear curvature to focus acoustic energy at the outer wall of the cochlear canal as the wave propagates toward the apex of the cochlea.
关于哺乳动物耳蜗蜗牛壳形状的传统理论认为，它的进化基本上（也许仅仅）是为了节省颅骨内部的空间。最近，一种理论提出，螺旋的渐变曲率增强了耳蜗对低频的机械反应。本文对耳蜗形状进行了多物种分析以验证该理论，并证明耳蜗螺旋最外层和最内层曲率半径的比值是一个重要的耳蜗特征，与低频听力极限密切相关。该比值作为曲率梯度的一种度量，反映了在声波向耳蜗顶端传播时，耳蜗曲率将声能聚焦在耳蜗管外壁的能力。
