Ren T, Nuttall A L
Oregon Hearing Research Center (NRC04), Department of Otolaryngology and Head and Neck Surgery, Oregon Health Sciences University, Portland 97201-3098, USA.
Hear Res. 2001 Jan;151(1-2):48-60. doi: 10.1016/s0378-5955(00)00211-2.
The basal membrane (BM) velocity responses to pure tones were measured using a newly developed laser interferometer microscope that does not require placing a reflecting object on the BM. It was demonstrated that the instrument is able to measure sub-nanometer vibration from the cochlear partition in the basal turn of the gerbil. The overall shape of the amplitude spectra shows typical tuning features. The 'best' frequencies (BFs) for the BM locations studied were between 14 kHz and 27 kHz, depending on the longitudinal position. For a given BM location, tuning sharpness was input level dependent, indicated by the Q(10dB), which varied from approximately 3 at low stimulus levels to near 1.5 at high input levels. At frequencies below BF, parallel amplitude/frequency curves across stimulus levels indicate a linear growth function. However, at frequencies near BF, the velocity increased linearly at low levels (<40 dB SPL) and became compressed between 40 and 50 dB SPL. Although the velocity gain for the frequency range below BF was a function of frequency, for a given frequency the gains were approximately constant across different levels. At frequencies near BF, the velocity gain at low sound pressure level was greater than that at a high sound pressure level, indicating a nonlinear negative relationship to stimulus level. The data also showed that the BF shifts toward the low frequencies with stimulus intensity increase. The phase spectra showed two important features: (1) at frequencies about half octave below the BF, phase slope is very small, indicating an extremely short delay; (2) the greatest phase lag occurs at frequencies near the BF, indicating a significant delay near this frequency range.
使用一种新开发的激光干涉显微镜测量了基底膜（BM）对纯音的速度响应，该显微镜无需在基底膜上放置反射物体。结果表明，该仪器能够测量沙鼠耳蜗基底转中基底膜的亚纳米级振动。振幅谱的整体形状显示出典型的调谐特征。所研究的基底膜位置的“最佳”频率（BFs）在14 kHz至27 kHz之间，具体取决于纵向位置。对于给定的基底膜位置，调谐锐度取决于输入电平，由Q(10dB)表示，其在低刺激电平下约为3，在高输入电平下接近1.5。在低于最佳频率的频率下，不同刺激电平下的平行振幅/频率曲线表明存在线性增长函数。然而，在接近最佳频率的频率下，速度在低电平（<40 dB SPL）时线性增加，并在40至50 dB SPL之间被压缩。尽管低于最佳频率范围内的速度增益是频率的函数，但对于给定频率，增益在不同电平下大致恒定。在接近最佳频率的频率下，低声压级下的速度增益大于高声压级下的速度增益，表明与刺激电平呈非线性负相关。数据还表明，随着刺激强度增加，最佳频率向低频方向移动。相位谱显示出两个重要特征：（1）在比最佳频率低约半个倍频程的频率处，相位斜率非常小，表明延迟极短；（2）最大相位滞后出现在接近最佳频率的频率处，表明在该频率范围内存在显著延迟。
