Windmill J F C, Bockenhauer S, Robert D
School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
J R Soc Interface. 2008 Dec 6;5(29):1435-43. doi: 10.1098/rsif.2008.0131.
A salient characteristic of most auditory systems is their capacity to analyse the frequency of sound. Little is known about how such analysis is performed across the diversity of auditory systems found in animals, and especially in insects. In locusts, frequency analysis is primarily mechanical, based on vibrational waves travelling across the tympanal membrane. Different acoustic frequencies generate travelling waves that direct vibrations to distinct tympanal locations, where distinct groups of correspondingly tuned mechanosensory neurons attach. Measuring the mechanical tympanal response, for the first time, to acoustic impulses in the time domain, nanometre-range vibrational waves are characterized with high spatial and temporal resolutions. Conventional Fourier analysis is also used to characterize the response in the frequency domain. Altogether these results show that travelling waves originate from a particular tympanal location and travel across the membrane to generate oscillations in the exact region where mechanosensory neurons attach. Notably, travelling waves are unidirectional; no strong back reflection or wave resonance could be observed across the membrane. These results constitute a key step in understanding tympanal mechanics in general, and in insects in particular, but also in our knowledge of the vibrational behaviour of anisotropic media.
大多数听觉系统的一个显著特征是它们分析声音频率的能力。对于动物尤其是昆虫中多种多样的听觉系统如何进行这种分析，我们了解甚少。在蝗虫中，频率分析主要是机械性的，基于穿过鼓膜的振动波。不同的声频会产生将振动导向鼓膜不同位置的行波，相应调谐的不同机械感觉神经元群附着在这些位置。首次在时域中测量鼓膜对声脉冲的机械响应，以高空间和时间分辨率对纳米级振动波进行了表征。还使用传统的傅里叶分析在频域中表征响应。这些结果共同表明，行波起源于鼓膜的特定位置，并穿过鼓膜在机械感觉神经元附着的确切区域产生振荡。值得注意的是，行波是单向的；在整个鼓膜上未观察到强烈的背向反射或波共振。这些结果是理解一般鼓膜力学的关键一步，特别是昆虫的鼓膜力学，也是我们了解各向异性介质振动行为的关键一步。
