Nuttall A L, Guo M, Ren T, Dolan D F
Oregon Hearing Research Center (NRC04), Department of Otolaryngology Head and Neck Surgery, Oregon Health Sciences University, Portland 97201-3098, USA.
Hear Res. 1997 Dec;114(1-2):35-42. doi: 10.1016/s0378-5955(97)00147-0.
Basilar membrane (BM) noise, measured as a velocity signal under the quiet acoustic condition, was investigated in the guinea pig. The cochleas of anesthetized young healthy guinea pigs were surgically exposed and a hole was made on the lateral wall of the scala tympani of the first cochlear turn for visualization of the BM and measurement of the BM velocity with a laser interferometer. The amplitude and frequency of the BM velocity noise were analyzed by a spectrum analyzer under different conditions. The spectrum of the BM velocity noise was a band limited function with a peak velocity at the topographic best frequency of the measured location on the BM. The peak velocity ranged to about 8 microm/s and depended on the physiological condition of the cochlea. Saline blockage of the external auditory canal or the middle ear did not change the BM noise. BM noise was much smaller, or was not evident, when the cochlear sensitivity decreased. The suppression tuning curve of the BM velocity noise indicates that the maximum suppression caused by an acoustic pure tone occurred at the best frequency location. A low sound level wide band acoustic noise given to the external ear canal produced a spectrum function having the same frequency and amplitude response as the BM noise. Electrical stimulation of the crossed olivocochlear bundle significantly depresses the BM velocity noise. These data demonstrate that the BM noise is a representation of internal rather than external noise. The amplitude and frequency of the BM noise reflect the usual cochlear sensitivity and frequency selectivity. Since the organ of Corti in the sensitive cochlea is a highly sensitive and tuned mechanical system, the internal (to the animal) noise responsible for the BM noise may originate from mechanical vibrations remote from the cochlea and propagated to the ear, or may be caused by Brownian motion of cellular structures in the cochlea.
在豚鼠中研究了在安静声学条件下作为速度信号测量的基底膜（BM）噪声。手术暴露麻醉的年轻健康豚鼠的耳蜗，并在第一耳蜗转鼓阶的外侧壁上开一个孔，以便可视化基底膜并用激光干涉仪测量基底膜速度。在不同条件下，通过频谱分析仪分析基底膜速度噪声的幅度和频率。基底膜速度噪声的频谱是一个带限函数，在基底膜上测量位置的地形最佳频率处具有峰值速度。峰值速度范围约为8微米/秒，并取决于耳蜗的生理状况。外耳道或中耳的盐水阻塞不会改变基底膜噪声。当耳蜗敏感性降低时，基底膜噪声要小得多，或者不明显。基底膜速度噪声的抑制调谐曲线表明，纯音引起的最大抑制发生在最佳频率位置。给予外耳道低声级宽带声噪声会产生具有与基底膜噪声相同频率和幅度响应的频谱函数。交叉橄榄耳蜗束的电刺激会显著降低基底膜速度噪声。这些数据表明，基底膜噪声是内部噪声而非外部噪声的一种表现。基底膜噪声的幅度和频率反映了通常的耳蜗敏感性和频率选择性。由于敏感耳蜗中的柯蒂氏器是一个高度敏感且调谐的机械系统，导致基底膜噪声的内部（对动物而言）噪声可能源自远离耳蜗并传播到耳朵的机械振动，或者可能由耳蜗中细胞结构的布朗运动引起。
