Lobarinas Edward, Spankovich Christopher, Le Prell Colleen G
The University of Texas at Dallas, School of Behavioral and Brain Sciences, USA.
University of Mississippi Medical Center, Department of Otolaryngology and Communicative Sciences, USA.
Hear Res. 2017 Jun;349:155-163. doi: 10.1016/j.heares.2016.12.009. Epub 2016 Dec 19.
In animals, noise exposures that produce robust temporary threshold shifts (TTS) can produce immediate damage to afferent synapses and long-term degeneration of low spontaneous rate auditory nerve fibers. This synaptopathic damage has been shown to correlate with reduced auditory brainstem response (ABR) wave-I amplitudes at suprathreshold levels. The perceptual consequences of this "synaptopathy" remain unknown but have been suggested to include compromised hearing performance in competing background noise. Here, we used a modified startle inhibition paradigm to evaluate whether noise exposures that produce robust TTS and ABR wave-I reduction but not permanent threshold shift (PTS) reduced hearing-in-noise performance. Animals exposed to 109 dB SPL octave band noise showed TTS >30 dB 24-h post noise and modest but persistent ABR wave-I reduction 2 weeks post noise despite full recovery of ABR thresholds. Hearing-in-noise performance was negatively affected by the noise exposure. However, the effect was observed only at the poorest signal to noise ratio and was frequency specific. Although TTS >30 dB 24-h post noise was a predictor of functional deficits, there was no relationship between the degree of ABR wave-I reduction and degree of functional impairment.
在动物中，能产生明显暂时性阈移（TTS）的噪声暴露可对传入突触造成即刻损伤，并导致低自发放电率听觉神经纤维的长期退变。这种突触性损伤已被证明与阈上水平时听觉脑干反应（ABR）I波振幅降低相关。这种“突触病”的感知后果尚不清楚，但有人认为可能包括在竞争性背景噪声中听力表现受损。在此，我们使用一种改良的惊吓抑制范式来评估能产生明显TTS和ABR I波降低但无永久性阈移（PTS）的噪声暴露是否会降低噪声中的听力表现。暴露于109 dB SPL倍频程带噪声的动物在噪声暴露后24小时显示TTS>30 dB，且在噪声暴露后2周ABR I波出现适度但持续的降低，尽管ABR阈值已完全恢复。噪声暴露对噪声中的听力表现产生了负面影响。然而，这种影响仅在最差信噪比时观察到，且具有频率特异性。尽管噪声暴露后24小时TTS>30 dB是功能缺陷的一个预测指标，但ABR I波降低程度与功能损害程度之间并无关联。
