Hu Ning, Nuttall Alfred L, Ren Tianying
Department of Otolaryngology - Head and Neck Surgery, Oregon Hearing Research Center, Oregon Health and Science University, Portland, 97239-3098, USA.
Hear Res. 2005 Apr;202(1-2):35-46. doi: 10.1016/j.heares.2004.11.002.
We reported that the electrically evoked basilar membrane (BM) vibration at frequencies above the best frequency (BF) showed a lowest BM velocity magnitude, called a "dip", in the velocity-frequency spectra, indicating a cancellation. In the present study, we measured the high frequency BM motion as functions of the longitudinal and radial locations. Measurements were taken at three longitudinal locations in the first turn and the hook region: 14.9, 15.8 and 16.8 mm from the apex, corresponding to the BFs of 17, 21.3 and 28.0 kHz calculated from Greenwood [J. Acoust. Soc. Am. 87, 2592], and at different radial locations across the width of the BM. It was found that the dip frequency (DF) varied with the longitudinal and radial locations. In the longitudinal direction, the average value of the DF was 49.6, 55.6 and 72.8 kHz, respectively. Thus, the longitudinal distribution of the high frequency BM vibration was correlated with the BF. In the radial direction, there was consistent variation of the response spectrum such that the dip was mainly evident in the pectinate zone of the BM. These results imply that the high frequency BM motion is related to mechanical properties of the cochlear partition, including the outer hair cells (OHCs) themselves. Data also indicate different vibration modes across the width of the organ of Corti.
我们曾报道，在最佳频率（BF）以上频率的电诱发基底膜（BM）振动在速度-频率谱中显示出最低的BM速度幅值，称为“凹陷”，这表明存在抵消现象。在本研究中，我们测量了高频BM运动随纵向和径向位置的变化情况。测量在第一圈和钩区的三个纵向位置进行：距顶点14.9、15.8和16.8毫米处，分别对应根据格林伍德公式[《美国声学学会杂志》87, 2592]计算得出的17、21.3和28.0千赫兹的BF，并且在BM宽度上的不同径向位置进行测量。结果发现，凹陷频率（DF）随纵向和径向位置而变化。在纵向方向上，DF的平均值分别为49.6、55.6和72.8千赫兹。因此，高频BM振动的纵向分布与BF相关。在径向方向上，响应谱存在一致的变化，使得凹陷主要在BM的栉状区明显。这些结果表明，高频BM运动与耳蜗隔的机械特性有关，包括外毛细胞（OHC）本身。数据还表明在柯蒂氏器宽度上存在不同的振动模式。
