Hilger A W, Furness D N, Wilson J P
Department of Communication and Neuroscience, Keele University, UK.
Hear Res. 1995 Apr;84(1-2):1-11. doi: 10.1016/0378-5955(95)00007-q.
Otoacoustic emissions are believed to arise from an active process associated with the outer hair cells in the mammalian organ of Corti. They have been attributed to the presence of impedance discontinuities on the basilar membrane which might be caused by hair cell irregularities. To test this hypothesis we have investigated the possible relationship between transient evoked otoacoustic emissions (TEOAEs) and anatomical integrity in the organ of Corti. Click-evoked TEOAEs have been measured from the ear canals of normal, pigmented guinea pigs using an Otodynamics ILO88 analyser. Emissions were present in 18 out of 19 animals tested and the major frequencies observed were consistently present in different measurements over periods of up to ten weeks provided recording conditions were satisfactory. The frequency spectra of the TEOAEs resembled those measured in humans but the latencies of the responses were considerably shorter. In one acute experiment, the TEOAEs were shown to be dependent on metabolic energy as they were lost rapidly following termination with an overdose of anaesthetic. In another case, evoked emissions of long duration (sustained) at about 1 kHz were obtained from both ears. All cochleae examined showed irregularities, especially patches of mainly apical outer hair cell loss of differing extents. However, there was no evidence that substantial lesions coincided consistently with the frequency regions corresponding to the major emissions. Nevertheless, it was noted that the total energy level of emissions was proportional to the total outer hair cell loss, except in one case, where the outer hair cell loss was substantial and the energy level of TEOAEs was considerably lower. Although there is no clear relationship between TEOAEs of specific frequencies and abnormalities at the corresponding cochleotopic location in the organ of Corti which could represent impedance discontinuities, the degree of irregularity may determine the overall emission level. This finding is consistent with the idea that emissions arise as a result of irregularity producing variations in the reflection coefficient.
耳声发射被认为源于与哺乳动物柯蒂氏器外毛细胞相关的一个主动过程。它们被归因于基底膜上存在的阻抗不连续性，这可能是由毛细胞不规则性引起的。为了验证这一假设，我们研究了瞬态诱发耳声发射（TEOAEs）与柯蒂氏器解剖完整性之间的可能关系。使用Otodynamics ILO88分析仪从正常的有色豚鼠耳道测量了短声诱发的TEOAEs。在19只受试动物中，有18只存在耳声发射，并且只要记录条件令人满意，在长达十周的时间内，不同测量中观察到的主要频率始终存在。TEOAEs的频谱与在人类中测量的频谱相似，但反应的潜伏期要短得多。在一项急性实验中，TEOAEs被证明依赖于代谢能量，因为在过量麻醉剂终止后它们迅速消失。在另一个案例中，从双耳获得了约1kHz的长时间（持续）诱发耳声发射。所有检查的耳蜗均显示出不规则性，尤其是不同程度的主要位于顶部的外毛细胞丢失斑块。然而，没有证据表明实质性病变始终与对应主要耳声发射的频率区域一致。尽管如此，值得注意的是，耳声发射的总能量水平与外毛细胞总丢失量成正比，但有一个案例除外，该案例中外毛细胞丢失严重，但TEOAEs的能量水平却低得多。尽管特定频率的TEOAEs与柯蒂氏器中对应耳蜗位置处可能代表阻抗不连续性的异常之间没有明确的关系，但不规则程度可能决定总体发射水平。这一发现与耳声发射是由不规则性导致反射系数变化而产生的观点一致。
