National Acoustic Laboratories, Australian Hearing Hub, Macquarie University, Sydney, NSW 2109, Australia; Macquarie University Hearing & Department of Linguistics, Australian Hearing Hub, Macquarie University, Sydney, NSW 2109, Australia.
Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK.
Curr Biol. 2020 Dec 7;30(23):4710-4721.e4. doi: 10.1016/j.cub.2020.09.046. Epub 2020 Oct 8.
Many individuals with seemingly normal hearing abilities struggle to understand speech in noisy backgrounds. To understand why this might be the case, we investigated the neural representation of speech in the auditory midbrain of gerbils with "hidden hearing loss" through noise exposure that increased hearing thresholds only temporarily. In noise-exposed animals, we observed significantly increased neural responses to speech stimuli, with a more pronounced increase at moderate than at high sound intensities. Noise exposure reduced discriminability of neural responses to speech in background noise at high sound intensities, with impairment most severe for tokens with relatively greater spectral energy in the noise-exposure frequency range (2-4 kHz). At moderate sound intensities, discriminability was surprisingly improved, which was unrelated to spectral content. A model combining damage to high-threshold auditory nerve fibers with increased response gain of central auditory neurons reproduced these effects, demonstrating that a specific combination of peripheral damage and central compensation could explain listening difficulties despite normal hearing thresholds.
许多听力看似正常的人在嘈杂的环境中难以理解言语。为了弄清楚其中的原因，我们通过噪声暴露来研究了具有“隐匿性听力损失”的沙鼠听觉中脑对言语的神经表示，这种噪声暴露只会暂时增加听力阈值。在暴露于噪声的动物中，我们观察到对言语刺激的神经反应明显增加，在中等强度而不是高强度的声音下增加更为明显。噪声暴露降低了在高强度背景噪声中对言语反应的可辨别性，对于在噪声暴露频率范围内（2-4 kHz）具有相对较大频谱能量的语音令牌，损害最为严重。在中等强度的声音下，可辨别性出人意料地得到了改善，这与频谱内容无关。结合高阈值听神经纤维损伤和中枢听觉神经元反应增益增加的模型再现了这些效果，表明外周损伤和中枢补偿的特定组合可以解释尽管听力阈值正常但仍存在听力困难的现象。
