PDF(Pubmed)
Abstract：
Normal hearing is associated with cochlear nonlinearity. When two tones (f1 and f2) are presented, the intracochlear response contains additional components that can be recorded from the ear canal as distortion product otoacoustic emissions (DPOAEs). Although the most prominent intermodulation distortion component is at 2f1-f2, other cubic distortion products are also generated. Because these measurements are noninvasive, they are used in humans and in animal models to detect hearing loss. This study evaluated how loss of sensitivity affects DPOAEs with frequencies above and below the stimulating primaries, i.e., for upper sideband (USB) components like 2f2-f1 and for lower sideband (LSB) components like 2f1-f2. DPOAEs were recorded in several mouse mutants with varying degrees of hearing loss associated with structural changes to the tectorial membrane (TM), or with loss of outer hair cell (OHC) somatic electromotility due to lack of prestin or to the expression of a non-functional prestin. In mice with changes in sensitivity, magnitude reductions were observed for 2f1-f2 relative to controls with mice lacking prestin showing the greatest changes. In contrast, 2f2-f1 was minimally affected by reductions in cochlear gain due to changes in the TM or by the loss of OHC somatic electromotility. In addition, TM mutants with spontaneous otoacoustic emissions (SOAEs) generated larger responses than controls at 2f2-f1 when its frequency was similar to that for the SOAEs. Although cochlear pathologies appear to affect USB and LSB DPOAEs in different ways, both 2f1-f2 and 2f2-f1 reflect nonlinearities associated with the transducer channels. However, in mice, the component at 2f2-f1 does not appear to receive enhancement due to prestin\'s motor action.
摘要：
正常听力与耳蜗非线性有关。当出现两个音调（f1和f2）时，耳蜗内响应包含可以从耳道记录为失真产物耳声发射(DPOAEs)的额外成分。尽管最突出的互调失真分量在2f1-f2处,但也产生其它立方失真产物。因为这些测量是非侵入性的，它们用于人类和动物模型以检测听力损失。本研究评估了敏感性损失如何影响频率高于和低于刺激原色的DPOAE，即，用于上边带（USB）组件（如2f2-f1）和下边带（LSB）组件（如2f1-f2）。在几种小鼠突变体中记录了DPOAE，这些突变体的听力损失程度与膜（TM）的结构变化有关，或由于缺乏prestin或非功能性prestin的表达而导致外毛细胞（OHC）体细胞运动性丧失。在敏感性发生变化的小鼠中，相对于缺乏prestin的小鼠的对照，2f1-f2观察到幅度降低，显示出最大的变化。相比之下,由于TM的变化或OHC体细胞电动性的丧失，2f2-f1受到耳蜗增益降低的影响最小。此外,具有自发耳声发射（SOAEs）的TM突变体在2f2-f1时产生的响应比对照更大。尽管耳蜗病变似乎以不同的方式影响USB和LSBDPOAE，2f1-f2和2f2-f1都反映了与换能器通道相关的非线性。然而,在老鼠身上，由于Prestin的运动动作，2f2-f1处的组件似乎没有得到增强。
