Department of Bioengineering and Centre for Neurotechnology, Imperial College London, South Kensington Campus, SW7 2AZ, London, UK.
John A. Paulson School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Cambridge, MA, 02138, USA.
Sci Rep. 2019 Oct 1;9(1):14131. doi: 10.1038/s41598-019-50773-1.
People with normal hearing thresholds can nonetheless have difficulty with understanding speech in noisy backgrounds. The origins of such supra-threshold hearing deficits remain largely unclear. Previously we showed that the auditory brainstem response to running speech is modulated by selective attention, evidencing a subcortical mechanism that contributes to speech-in-noise comprehension. We observed, however, significant variation in the magnitude of the brainstem's attentional modulation between the different volunteers. Here we show that this variability relates to the ability of the subjects to understand speech in background noise. In particular, we assessed 43 young human volunteers with normal hearing thresholds for their speech-in-noise comprehension. We also recorded their auditory brainstem responses to running speech when selectively attending to one of two competing voices. To control for potential peripheral hearing deficits, and in particular for cochlear synaptopathy, we further assessed noise exposure, the temporal sensitivity threshold, the middle-ear muscle reflex, and the auditory-brainstem response to clicks in various levels of background noise. These tests did not show evidence for cochlear synaptopathy amongst the volunteers. Furthermore, we found that only the attentional modulation of the brainstem response to speech was significantly related to speech-in-noise comprehension. Our results therefore evidence an impact of top-down modulation of brainstem activity on the variability in speech-in-noise comprehension amongst the subjects.
听力正常的人在嘈杂环境中理解言语仍可能存在困难。这种阈上听力缺陷的起源在很大程度上仍不清楚。此前我们表明，对连续言语的听觉脑干反应受到选择性注意的调制，证明了一种有助于噪声下言语理解的皮质下机制。然而，我们观察到不同志愿者之间脑干注意力调制的幅度存在显著差异。在这里，我们表明这种可变性与受试者在背景噪声中理解言语的能力有关。具体来说，我们评估了 43 名听力正常的年轻志愿者在背景噪声下的言语理解能力。我们还记录了他们在选择性关注两个竞争声音之一时对连续言语的听觉脑干反应。为了控制潜在的外围听力缺陷，特别是耳蜗突触病，我们进一步评估了噪声暴露、时间敏感性阈值、中耳肌肉反射以及在不同水平背景噪声下对点击的听觉脑干反应。这些测试没有在志愿者中发现耳蜗突触病的证据。此外，我们发现只有对言语的脑干反应的注意力调制与噪声下言语理解显著相关。因此，我们的研究结果证明了对脑干活动的自上而下调制对受试者在噪声下言语理解的可变性的影响。
