School of Psychological Sciences, The University of Manchester, Manchester, M13 9PL, UK.
Adv Exp Med Biol. 2013;787:31-8. doi: 10.1007/978-1-4614-1590-9_4.
Although physiological measures have provided a great deal of -information about the basilar membrane (BM) response of non-human mammals, it is only relatively recently that behavioural techniques have allowed researchers to measure accurately the non-linear characteristics of the human BM. These techniques are based on forward masking, in which the threshold for detecting a signal is measured in the presence of a prior masking sound. Two popular techniques, the growth of forward masking technique and the temporal masking curve technique, rely on the fact that compression in the base of the cochlea is largely restricted to frequencies close to the characteristic frequency (CF) of each place. By comparing the response to a masker with a frequency equal to that of the signal with the response to a lower-frequency masker, it is possible to infer the CF response. These measures have shown that BM compression in humans matches that of other mammals and that compression is absent in listeners with moderate-to-severe cochlear hearing loss, probably reflecting outer hair cell dysfunction. Another technique, the additivity of forward masking (AFM) technique, does not rely on a comparison between on- and off-frequency maskers, but instead measures the effect on threshold of combining two nonoverlapping maskers, an effect which is magnified by compression. The difference between thresholds in the single- and combined-masker conditions can be used to estimate compression. The AFM technique has provided evidence that strong compression extends down to low CFs in humans, a finding inconsistent with direct measures of the BM response in other mammals. Furthermore, recent AFM results suggest that there may be an additional source of compression central to the BM. This more central compression also appears to be affected by hearing loss and may reflect non-linear processes in the transduction mechanism of the inner hair cells.
虽然生理测量为基底膜 (BM) 的非人类哺乳动物反应提供了大量信息，但直到最近，行为技术才使研究人员能够准确测量人类 BM 的非线性特征。这些技术基于前向掩蔽，其中在存在先前掩蔽声音的情况下测量检测信号的阈值。两种流行的技术，前向掩蔽增长技术和时间掩蔽曲线技术，依赖于耳蜗基底的压缩在很大程度上仅限于接近每个位置特征频率 (CF) 的频率的事实。通过比较与信号频率相等的掩蔽器的响应与较低频率掩蔽器的响应，可以推断出 CF 响应。这些措施表明，人类 BM 的压缩与其他哺乳动物的压缩相匹配，并且在中度至重度耳蜗听力损失的听众中不存在压缩，这可能反映了外毛细胞功能障碍。另一种技术，前向掩蔽的可加性 (AFM) 技术，不依赖于同频和异频掩蔽器之间的比较，而是测量两个不重叠掩蔽器组合对阈值的影响，这种影响通过压缩放大。在单掩蔽器和组合掩蔽器条件下的阈值差异可用于估计压缩。AFM 技术提供的证据表明，在人类中，强压缩延伸到低 CF，这一发现与其他哺乳动物的 BM 反应的直接测量不一致。此外，最近的 AFM 结果表明，BM 中心可能存在额外的压缩源。这种更中心的压缩似乎也受到听力损失的影响，可能反映了内毛细胞转导机制中的非线性过程。
