Department of Cell Biology and Neuroscience, AK Neurobiology and Biosensors, Max-von-Laue-Strasse 13, Goethe University Frankfurt am Main, 60438, 60323 Frankfurt am Main, Germany.
J Exp Biol. 2011 Nov 1;214(Pt 21):3596-604. doi: 10.1242/jeb.054445.
In the auditory system of bushcrickets, sound can reach the receptors via two different paths: (i) by acting on the outside of the tympana situated on both sides of each foreleg or (ii) through the acoustic trachea that opens at a spiracle on the thorax. While the spiracle is considered to be the main point of sound entry for higher audio and ultrasonic frequencies, the role of the tympana is still unclear. The tympana border the air-filled acoustic trachea as well as the fluid-filled haemolymph channel containing the receptor organs. To understand their role during sound transduction, the sound-induced neuronal response of the hearing organ was recorded in combination with measurement of tympanal membrane motion using laser-Doppler vibrometry. For far-field stimulation, the frequency of the most sensitive hearing (∼16 kHz) matched the frequency of a pronounced maximum of tympanal membrane vibration. A second maximum of tympanum motion at lower frequencies (∼7 kHz) was correlated with an increased nerve activity at higher intensities (>70 dB sound pressure level, SPL). These correlations support the hypothesis of functional coupling between tympanum motion and nerve activity. When sound stimuli were applied locally, through either the tympanum or the spiracle, significant differences between tympanum motion and nerve activity were found. These discrepancies show that tympanum motion and neuronal response are not coupled directly and that there is no linear relationship with the applied SPL. Taken together, these data verify a functional, albeit indirect, coupling of tympanum motion and sensory cell activity for one of the pronounced vibration maxima, which appears to represent a resonance frequency of the tympanum.
在蟋蟀的听觉系统中，声音可以通过两种不同的路径到达受体：(i) 通过作用于位于每条前腿两侧的鼓膜的外部，或 (ii) 通过在胸部的气门打开的声学气管。虽然气门被认为是较高音频和超声波频率的主要声音进入点，但鼓膜的作用仍不清楚。鼓膜与充满空气的声学气管以及包含受体器官的充满血液的血腔通道相邻。为了了解它们在声音转导过程中的作用，使用激光多普勒测振仪记录了听觉器官的声音诱导神经元反应，同时测量鼓膜的运动。对于远场刺激，最敏感的听力频率（约 16 kHz）与鼓膜振动的显著最大值的频率相匹配。鼓膜运动的第二个较低频率（约 7 kHz）的最大值与较高强度（>70 分贝声压级，SPL）的神经活动增加相关。这些相关性支持鼓膜运动和神经活动之间存在功能耦合的假设。当声音刺激通过鼓膜或气门局部施加时，发现鼓膜运动和神经活动之间存在显著差异。这些差异表明，鼓膜运动和神经元反应没有直接耦合，并且与施加的 SPL 没有线性关系。总之，这些数据验证了鼓膜运动和感觉细胞活动之间的功能（尽管是间接的）耦合，这似乎代表了鼓膜的一个明显振动最大值的共振频率。
