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首页> 外文期刊>Journal of Neurophysiology >Long-term sound conditioning enhances cochlear sensitivity.
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Long-term sound conditioning enhances cochlear sensitivity.

机译：长期的声音调节可增强耳蜗的灵敏度。

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Sound conditioning, by chronic exposure to moderate-level sound, can protect the inner ear (reduce threshold shifts and hair cell damage) from subsequent high-level sound exposure. To investigate the mechanisms underlying this protective effect, the present study focuses on the physiological changes brought on by the conditioning exposure itself. In our guinea-pig model, 6-h daily conditioning exposure to an octave-band noise at 85 dB SPL reduces the permanent threshold shifts (PTSs) from a subsequent 4-h traumatic exposure to the same noise band at 109 dB SPL, as assessed by both compound action potentials (CAPs) and distortion product otoacoustic emissions (DPOAEs). The frequency region of maximum threshold protection is approximately one-half octave above the upper frequency cutoff of the exposure band. Protection is also evident in the magnitude of suprathreshold CAPs and DPOAEs, where effects are more robust and extend to higher frequencies than those evident at or near threshold. The conditioning exposure also enhanced cochlear sensitivity, when evaluated at the same postconditioning time at which the traumatic exposure would be delivered in a protection study. Response enhancements were seen in both threshold and suprathreshold CAPs and DPOAEs. The frequency dependence of the enhancement effects differed, however, by these two metrics. For CAPs, effects were maximum in the same frequency region as those most protected by the conditioning. For DPOAEs, enhancements were shifted to lower frequencies. The conditioning exposure also enhanced both ipsilaterally and contralaterally evoked olivocochlear (OC) reflex strength, as assessed using DPOAEs. The frequency and level dependence of the reflex enhancements were consistent with changes seen in sound-evoked discharge rates in OC fibers after conditioning. However, comparison with the frequency range and magnitude of conditioning-related protection suggests that the protection cannot be completely explained by amplification of the OC reflex and the known protective effects of OC feedback. Rather, the present results suggest that sound conditioning leads to changes in the physiology of the outer hair cells themselves, the peripheral targets of the OC reflex.
机译：通过长期暴露于中等水平的声音来进行声音调节，可以保护内耳（减少阈值漂移和毛细胞损伤）免受随后的高水平声音暴露。为了研究这种保护作用的潜在机制，本研究着重于条件暴露本身带来的生理变化。在我们的豚鼠模型中，每天进行6小时的条件下暴露于85 dB SPL的八度频带噪声会降低永久阈值偏移（PTS），从随后的4小时的外伤暴露至109 dB SPL的相同噪声带，如通过复合动作电位（CAP）和失真产物耳声发射（DPOAE）进行评估。最大阈值保护的频率区域大约比曝光频带的最高频率截止高一半八度。在超阈值CAP和DPOAE的数量级中，保护作用也很明显，与阈值或接近阈值时相比，这些效应更强健并扩展到更高的频率。当在保护研究中在与创伤性暴露相同的后适应时间进行评估时，条件暴露还增强了耳蜗敏感性。在阈值和超阈值CAPs和DPOAEs中均观察到反应增强。然而，这两个指标使增强效果的频率依赖性有所不同。对于CAP，在与最受调节保护的频率范围相同的频率范围内，效果最大。对于DPOAE，增强功能已转移到较低的频率。使用DPOAEs评估，条件暴露还增强了同侧和对侧诱发的乳突（OC）反射强度。反射增强的频率和水平依赖性与调理后OC纤维的声诱发放电速率的变化一致。但是，与调节相关保护的频率范围和幅度的比较表明，不能通过放大OC反射和OC反馈的已知保护作用来完全解释保护。相反，目前的结果表明，声音调节会导致外部毛细胞本身（OC反射的外围目标）的生理变化。

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