Two-tone distortion on the basilar membrane of the chinchilla cochlea
Two-tone distortion on the basilar membrane of the chinchilla cochlea
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DOI：
10.1152/jn.1997.77.5.2385
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发表时间：
1997-05-01
影响因子：
2.5
通讯作者：
Rich, NC
中科院分区：
文献类型：
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作者：
Robles, L;Ruggero, MA;Rich, NC
用激光测速仪测量了麻醉龙猫耳蜗底转部的基底膜对声调的反应。基底膜对频率(f(1)，f(2))接近特征频率(Cf)的基频反应的频谱中，在高于和低于Cf的频率(如2f(1)-f(2)，3f(1)-2f(2)，2f(2)-f(1)和3f(2)-2f(1))上都存在显著的奇数阶双音失真产物(DPS)。对于频率为2f(1)-f(2)等于Cf的等水平初级刺激，2f(1)-f(2)DP的幅度在低刺激水平下以线性或更快的速率随初级水平增长，但在较高水平时饱和或略有下降。对于一个基音的固定电平，2f(1)-f(2)DP的大小是另一个基音的电平的非单调函数。对于低强度的可变音调，2f(1)-f(2)dp的增长率与f(1)电平下的2db/db和f(2)电平下的1db/db相似。在低刺激水平下，DP幅度随主频比(f(2)/f(1))的增加而迅速减小。对于更强烈的刺激，DP幅度在很大的频率比范围内保持不变或缓慢下降，直到达到临界值，此时DP幅度下降的斜率高达-300分贝/八度。随着刺激水平的增加，在较大的f(2)/(1)比率时，DP时相逐渐滞后，但在较小的f(2)/f(1)比率时表现出领先。耳蜗处暴露于对主要频率产生较大灵敏度损失(但对于频率等于2f(1)-f(2)的音调只有很小的损失)的强烈音调，会导致2f(1)-f(2)DP的幅度显著降低。这一结果表明，2f(1)-f(2)DP起源于基底膜区域，CFs对应于主频，并传播到Cf等于Dp频率的位置。基底膜上的2f(1)-f(2)dps在大多数方面与人类心理物理学中测得的dps相似。然而，在DP耳声发射中，基底膜DPS的大小并不表现出对f(2)/f(1)比值的非单调依赖性。
Basilar membrane responses to pairs of tones were measured, with the use of a laser velocimeter, in the basal turn of the cochlea in anesthetized chinchillas. Frequency spectra of basilar membrane responses to primary tones with frequencies (f(1), f(2)) close to the characteristic frequency (CF) contain prominent odd-order two-tone distortion products (DPs) at frequencies both higher and lower than CF (such as 2f(1) - f(2), 3f(1) - 2f(2), 2f(2) - f(1) and 3f(2) - 2f(1)). For equal-level primaries with frequencies such that 2f(1) - f(2) equals CF, the magnitude of the 2f(1) - f(2) DP grows with primary level at linear or faster rates at low stimulus levels, but it saturates or decreases slightly at higher levels. For a fixed level of one of the primary tones, the magnitude of the 2f(1) - f(2) DP is a nonmonotonic function of the level of the other primary tone. For low intensities of the variable tone, the 2f(1) - f(2) DP grows at a rate of similar to 2 dB/dB with f(1) level and 1 dB/dB with f(2) level. DP magnitudes decrease rapidly with increasing primary frequency ratio (f(2)/f(1)) at low stimulus levels. For more intense stimuli, DP magnitudes remain constant or decrease slowly over a wide range of frequency ratios until a critical value is reached, at which DP magnitudes fall with slopes as steep as -300 dB/octave. As stimulus level grows, DP phases increasingly lag for large f(2)/(1) ratios, but exhibit leads for small f(2)/f(1) ratios. Cochlear exposure to an intense tone that produces large sensitivity losses for the primary frequencies (but only small losses for tones with frequency equal to 2f(1) - f(2)) causes a substantial decrease in magnitude of the 2f(1) - f(2) DP. This result demonstrates that the 2f(1) - f(2) DP originates at the basilar membrane region with CFs corresponding to the primary frequencies and propagates to the location with CF equal to the DP frequency. 2f(1) - f(2) DPs on the basilar membrane resemble those measured in human psychophysics in most respects. However, the magnitude of basilar membrane DPs does not show the nonmonotonic dependence on f(2)/f(1) ratio evident in DP otoacoustic emissions.