Active control of ultrasonic hearing in frogs
Active control of ultrasonic hearing in frogs
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青蛙超声波听力的主动控制
DOI：
10.1073/pnas.0802210105
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发表时间：
2008-08-05
影响因子：
11.1
通讯作者：
Narins, Peter M.
中科院分区：
文献类型：
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作者：
Gridi-Papp, Marcos;Feng, Albert S.;Narins, Peter M.
脊椎动物可以在面对强烈的外部声音时或在自己发声时调节进入内耳的声音水平。中耳肌肉收缩抑制中耳听小骨的运动，衰减低频声音的传输，从而保护内耳中的毛细胞。在这里，我们表明，中国凹耳激流蛙，臭蛙tormota，可以调整其耳朵动态关闭其正常开放的咽鼓管。与青蛙的中耳与嘴永久沟通的观点相反，O。tormota可以通过收缩颌下肌和岩舌骨肌来关闭这种连接，从而大大减少鼓膜后面的空气量。数学建模和激光多普勒振动测量显示，该空气体积的减少增加了中耳阻抗，导致在高频（10-32 kHz）下鼓膜振动的高达20 dB的增益和在低频（3-10 kHz）下的26 dB的衰减。咽鼓管关闭观察领域在呼叫和吞咽。除了在保护内耳免受强烈的低频声音和高口腔气压在呼叫过程中的潜在作用外，这种以前未被认识到的脊椎动物机制可能会从主导环境的低频流噪声中揭示该物种的高频呼叫。这种机制也保护薄鼓膜在吞咽活的节肢动物猎物时免受损伤。
Vertebrates can modulate the sound levels entering their inner ears in the face of intense external sound or during their own vocalizations. Middle ear muscle contractions restrain the motion of the middle ear ossicles, attenuating the transmission of low-frequency sound and thereby protecting the hair cells in the inner ear. Here we show that the Chinese concave-eared torrent frog, Odorrana tormota, can tune its ears dynamically by closing its normally open Eustachian tubes. Contrary to the belief that the middle ear in frogs permanently communicates with the mouth, O. tormota can close this connection by contraction of the submaxillary and petrohyoid muscles, drastically reducing the air volume behind the eardrums. Mathematical modeling and laser Doppler vibrometry revealed that the reduction of this air volume increases the middle ear impedance, resulting in an up to 20 dB gain in eardrum vibration at high frequencies (10–32 kHz) and 26 dB attenuation at low frequencies (3–10 kHz). Eustachian tube closure was observed in the field during calling and swallowing. Besides a potential role in protecting the inner ear from intense low-frequency sound and high buccal air pressure during calling, this previously unrecognized vertebrate mechanism may unmask the high-frequency calls of this species from the low-frequency stream noise which dominates the environment. This mechanism also protects the thin tympanic membranes from injury during swallowing of live arthropod prey.