The dissimilar time course of temporary threshold shifts and reduction of inhibition in the inferior colliculus following intense sound exposure
The dissimilar time course of temporary threshold shifts and reduction of inhibition in the inferior colliculus following intense sound exposure
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DOI：
10.1016/j.heares.2014.03.004
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发表时间：
2014-06-01
期刊：
影响因子：
2.8
通讯作者：
van Dijk, P.
中科院分区：
文献类型：
--
作者：
Heeringa, A. N.;van Dijk, P.
众所周知，过度的噪音暴露会产生听觉阈值变化，这种变化可能是永久性的，也可能是暂时性的。最近的研究表明，噪声引起的暂时性阈值变化与内毛细胞突触连接的丧失以及耳蜗神经变性有关，这反映在听性脑干反应（ABR）的 I 波幅度降低上。这表明，尽管听觉阈值正常，但中枢听觉处理可能异常。我们记录了声音引起的暂时阈值偏移后中枢听觉处理的变化。将麻醉的豚鼠暴露在 11 kHz 的纯音（124 dB 声压级）下 1 小时。在暴露后立即、一周、两周和四周评估听力阈值、ABR 波 I 和 IV 的幅度以及下丘 (IC) 的自发放电率和音调诱发放电率。听力阈值在过度暴露后立即升高，但在一周内恢复。在所有测试期间，所有暴露于声音的动物的 ABR 波 I 的振幅均降低。相比之下，ABR 波 IV 幅度仅在过度暴露后立即下降，并在一周内恢复。在过度暴露后两周内，对纯音表现出抑制反应的 IC 单元比例大幅下降，尤其是在高频刺激下。对低频的兴奋反应比例增加。自发活动不受过度暴露的影响。尽管听觉阈值迅速正常化，但我们的结果表明，声音暴露后中枢增益增加，并且在过度暴露后两周内中脑兴奋性和抑制性反应之间的异常平衡。这些发现可能与声音引起的暂时阈值偏移后的听觉过敏有关。 (C) 2014 年作者。由 Elsevier B.V. 出版
Excessive noise exposure is known to produce an auditory threshold shift, which can be permanent or transient in nature. Recent studies showed that noise-induced temporary threshold shifts are associated with loss of synaptic connections to the inner hair cells and with cochlear nerve degeneration, which is reflected in a decreased amplitude of wave I of the auditory brainstem response (ABR). This suggests that, despite normal auditory thresholds, central auditory processing may be abnormal.We recorded changes in central auditory processing following a sound-induced temporary threshold shift. Anesthetized guinea pigs were exposed for 1 h to a pure tone of 11 kHz (124 dB sound pressure level). Hearing thresholds, amplitudes of ABR waves I and IV, and spontaneous and tone-evoked firing rates in the inferior colliculus (IC) were assessed immediately, one week, two weeks, and four weeks post exposure.Hearing thresholds were elevated immediately following overexposure, but recovered within one week. The amplitude of the ABR wave I was decreased in all sound-exposed animals for all test periods. In contrast, the ABR wave IV amplitude was only decreased immediately after overexposure and recovered within a week. The proportion of IC units that show inhibitory responses to pure tones decreased substantially up to two weeks after overexposure, especially when stimulated with high frequencies. The proportion of excitatory responses to low frequencies was increased. Spontaneous activity was unaffected by the overexposure.Despite rapid normalization of auditory thresholds, our results suggest an increased central gain following sound exposure and an abnormal balance between excitatory and inhibitory responses in the midbrain up to two weeks after overexposure. These findings may be associated with hyperacusis after a sound-induced temporary threshold shift. (C) 2014 The Authors. Published by Elsevier B.V.