Millman Rebecca E, Mattys Sven L, Gouws André D, Prendergast Garreth
Manchester Centre for Audiology and Deafness, Division of Human Communication, Deafness and Hearing, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, United Kingdom,
Department of Psychology, University of York, York YO10 5DD, United Kingdom, and.
J Neurosci. 2017 Aug 9;37(32):7727-7736. doi: 10.1523/JNEUROSCI.2722-16.2017. Epub 2017 Jul 10.
Verbal communication in noisy backgrounds is challenging. Understanding speech in background noise that fluctuates in intensity over time is particularly difficult for hearing-impaired listeners with a sensorineural hearing loss (SNHL). The reduction in fast-acting cochlear compression associated with SNHL exaggerates the perceived fluctuations in intensity in amplitude-modulated sounds. SNHL-induced changes in the coding of amplitude-modulated sounds may have a detrimental effect on the ability of SNHL listeners to understand speech in the presence of modulated background noise. To date, direct evidence for a link between magnified envelope coding and deficits in speech identification in modulated noise has been absent. Here, magnetoencephalography was used to quantify the effects of SNHL on phase locking to the temporal envelope of modulated noise (envelope coding) in human auditory cortex. Our results show that SNHL enhances the amplitude of envelope coding in posteromedial auditory cortex, whereas it enhances the fidelity of envelope coding in posteromedial and posterolateral auditory cortex. This dissociation was more evident in the right hemisphere, demonstrating functional lateralization in enhanced envelope coding in SNHL listeners. However, enhanced envelope coding was not perceptually beneficial. Our results also show that both hearing thresholds and, to a lesser extent, magnified cortical envelope coding in left posteromedial auditory cortex predict speech identification in modulated background noise. We propose a framework in which magnified envelope coding in posteromedial auditory cortex disrupts the segregation of speech from background noise, leading to deficits in speech perception in modulated background noise. People with hearing loss struggle to follow conversations in noisy environments. Background noise that fluctuates in intensity over time poses a particular challenge. Using magnetoencephalography, we demonstrate anatomically distinct cortical representations of modulated noise in normal-hearing and hearing-impaired listeners. This work provides the first link among hearing thresholds, the amplitude of cortical representations of modulated sounds, and the ability to understand speech in modulated background noise. In light of previous work, we propose that magnified cortical representations of modulated sounds disrupt the separation of speech from modulated background noise in auditory cortex.
在嘈杂背景下进行言语交流具有挑战性。对于患有感音神经性听力损失（SNHL）的听力受损听众而言，理解强度随时间波动的背景噪声中的言语尤为困难。与SNHL相关的快速作用的耳蜗压缩功能减退，会夸大调幅声音中强度的感知波动。SNHL引起的调幅声音编码变化，可能会对SNHL听众在存在调制背景噪声的情况下理解言语的能力产生不利影响。迄今为止，尚未有直接证据表明放大的包络编码与调制噪声中言语识别缺陷之间存在联系。在此，我们使用脑磁图来量化SNHL对人类听觉皮层中与调制噪声的时间包络锁相（包络编码）的影响。我们的结果表明，SNHL增强了后内侧听觉皮层中包络编码的幅度，而在增强后内侧和后外侧听觉皮层中包络编码的保真度。这种分离在右半球更为明显，表明SNHL听众在增强包络编码方面存在功能侧化。然而，增强的包络编码在感知上并无益处。我们的结果还表明，听力阈值以及在较小程度上，左后内侧听觉皮层中放大的皮层包络编码，均可预测调制背景噪声中的言语识别。我们提出了一个框架，其中后内侧听觉皮层中放大的包络编码会干扰言语与背景噪声的分离，导致在调制背景噪声中言语感知出现缺陷。听力损失患者在嘈杂环境中难以跟上对话。强度随时间波动的背景噪声带来了特别的挑战。我们使用脑磁图证明了正常听力和听力受损听众中调制噪声在解剖学上不同的皮层表征。这项工作首次将听力阈值、调制声音的皮层表征幅度以及在调制背景噪声中理解言语的能力联系起来。根据先前的研究，我们提出调制声音的放大皮层表征会破坏听觉皮层中言语与调制背景噪声的分离。
