Celiker Emine, Woodrow Charlie, Mhatre Natasha, Montealegre-Z Fernando
University of Lincoln, School of Life and Environmental Sciences, Joseph Banks Laboratories, Lincoln, United Kingdom.
Department of Biology, Western University, London, ON, Canada.
Front Insect Sci. 2022 Aug 15;2:957385. doi: 10.3389/finsc.2022.957385. eCollection 2022.
Bush-crickets (or katydids) have sophisticated and ultrasonic ears located in the tibia of their forelegs, with a working mechanism analogous to the mammalian auditory system. Their inner-ears are endowed with an easily accessible hearing organ, the (CA), possessing a spatial organisation that allows for different frequencies to be processed at specific graded locations within the structure. Similar to the basilar membrane in the mammalian ear, the CA contains mechanosensory receptors which are activated through the frequency dependent displacement of the CA. While this tonotopical arrangement is generally attributed to the gradual stiffness and mass changes along the hearing organ, the mechanisms behind it have not been analysed in detail. In this study, we take a numerical approach to investigate this mechanism in the ear. In addition, we propose and test the effect of the different vibration transmission mechanisms on the displacement of the CA. The investigation was carried out by conducting finite-element analysis on a three-dimensional, idealised geometry of the inner-ear, which was based on precise measurements. The numerical results suggested that even the mildest assumptions about stiffness and mass gradients allow for tonotopy to emerge, and the loading area and location for the transmission of the acoustic vibrations play a major role in the formation of tonotopy.
螽斯（或纺织娘）在前腿胫骨处有复杂的超声波耳朵，其工作机制类似于哺乳动物的听觉系统。它们的内耳有一个易于触及的听觉器官，即听觉感受器（CA），其空间组织允许在结构内特定的分级位置处理不同频率。与哺乳动物耳朵中的基底膜类似，CA包含机械感觉受体，这些受体通过CA的频率依赖性位移而被激活。虽然这种音频拓扑排列通常归因于沿着听觉器官的逐渐刚度和质量变化，但其背后的机制尚未详细分析。在这项研究中，我们采用数值方法来研究CA耳朵中的这种机制。此外，我们提出并测试了不同振动传播机制对CA位移的影响。该研究通过对基于精确测量的三维理想化内耳几何结构进行有限元分析来进行。数值结果表明，即使对刚度和质量梯度做出最温和的假设也能产生音频拓扑，并且声振动传播的加载区域和位置在音频拓扑的形成中起主要作用。
