Dolan D F, Guo M H, Nuttall A L
Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor 48109-0506, USA.
J Acoust Soc Am. 1997 Dec;102(6):3587-96. doi: 10.1121/1.421008.
Basilar membrane (BM) velocity responses were measured in the presence of olivocochlear bundle (OCB) stimulation. Frequency threshold tuning curves (FTCs) were derived from tone-evoked input-output (I/O) functions. Efferent nerve activation produced decreases in velocity amplitude for frequencies around best frequency (BF) at low stimulus levels with little or no effect for stimuli well below the BF. A level-dependent efferent reduction/enhancement of BM velocity was found for certain stimulus frequencies above the BF. Efferent activation either had no effect or caused small reductions in the velocity response produced by low level sound, whereas, at higher stimulus levels, efferent activation increased the velocity response. The derived FTCs, therefore, showed criterion-dependent changes with efferent activation. For low BM criterion velocities, FTCs showed the classic desensitization of the tip region without a shift of BF. Some BM velocity criterion values showed FTCs with an expanded high-frequency response area, also without a shift of BF. The results suggest that the effect of OCB activation changes the gain of the voltage-dependent outer hair cell motility such that BM velocity response near BF is decreased while increasing the response for tones well above BF.
在橄榄耳蜗束（OCB）刺激的情况下测量基底膜（BM）速度响应。频率阈值调谐曲线（FTC）由音调诱发的输入-输出（I/O）函数得出。在低刺激水平下，传出神经激活会使最佳频率（BF）附近频率的速度幅度降低，而对于远低于BF的刺激几乎没有影响。对于BF以上的某些刺激频率，发现了与水平相关的传出神经对BM速度的降低/增强作用。传出神经激活对低强度声音产生的速度响应要么没有影响，要么导致小幅降低，而在较高刺激水平下，传出神经激活会增加速度响应。因此，得出的FTC显示出随着传出神经激活而依赖于标准的变化。对于低BM标准速度，FTC显示出尖端区域的经典脱敏，而BF没有偏移。一些BM速度标准值显示FTC具有扩展的高频响应区域，BF也没有偏移。结果表明，OCB激活的作用改变了电压依赖性外毛细胞运动的增益，使得BF附近的BM速度响应降低，同时增加了远高于BF的音调的响应。
