Psychophysiological analyses demonstrate the importance of neural envelope coding for speech perception in noise.
Psychophysiological analyses demonstrate the importance of neural envelope coding for speech perception in noise.
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DOI：
10.1523/jneurosci.4493-11.2012
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发表时间：
2012-02-01
期刊：
影响因子：
--
通讯作者：
Heinz MG
中科院分区：
文献类型：
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作者：
Swaminathan J;Heinz MG
在嘈杂的环境中理解语音通常被认为是理所当然的。然而，这项任务对于耳蜗听力损失的人来说尤其具有挑战性，即使使用助听器或人工耳蜗。改进听觉假肢的一个重要限制是我们对噪声中稳健语音感知的神经基础缺乏了解。感知研究表明，声波波形（包络，ENV）缓慢变化的成分足以理解安静的语音，但快速变化的时间精细结构（TFS）在噪声中很重要。这些感知发现对人工耳蜗具有重要意义，目前人工耳蜗仅提供 ENV；然而，由于声学 TFS 和恢复的神经 ENV 之间的耳蜗转换，神经相关性很难评估。在这里，我们通过定量地将计算听觉神经模型预测的神经编码与正常听力人类听众测量的噪声中声码语音的感知联系起来，展示了神经 ENV 和 TFS 的相对贡献。以 ENV 和 TFS 编码作为自变量的回归模型预测了正信噪比和负信噪比下的语音识别和语音特征接收。我们发现 1) 神经 ENV 编码是语音感知的主要贡献者，即使在噪声中也是如此；2) 神经 TFS 主要在神经 ENV 存在的情况下对噪声产生贡献，但很少作为主要线索本身。这些结果表明，由于 TFS 和 ENV 之间的耳蜗信号处理转换，神经 TFS 的感知显着性比之前想象的要低。由于正常耳朵和受损耳朵之间的这些转变不同，因此这些发现对听觉假体具有重要的转化意义。
Understanding speech in noisy environments is often taken for granted; however, this task is particularly challenging for people with cochlear hearing loss, even with hearing aids or cochlear implants. A significant limitation to improving auditory prostheses is our lack of understanding of the neural basis for robust speech perception in noise. Perceptual studies suggest the slowly varying component of the acoustic waveform (envelope, ENV) is sufficient for understanding speech in quiet, but the rapidly varying temporal fine structure (TFS) is important in noise. These perceptual findings have important implications for cochlear implants, which currently only provide ENV; however, neural correlates have been difficult to evaluate due to cochlear transformations between acoustic TFS and recovered neural ENV. Here, we demonstrate the relative contributions of neural ENV and TFS by quantitatively linking neural coding, predicted from a computational auditory-nerve model, with perception of vocoded speech in noise measured from normal-hearing human listeners. Regression models with ENV and TFS coding as independent variables predicted speech identification and phonetic-feature reception at both positive and negative signal-to-noise ratios. We found that 1) neural ENV coding was a primary contributor to speech perception, even in noise, and 2) neural TFS contributed in noise mainly in the presence of neural ENV, but rarely as the primary cue itself. These results suggest neural TFS has less perceptual salience than previously thought due to cochlear signal-processing transformations between TFS and ENV. Because these transformations differ between normal and impaired ears, these findings have important translational implications for auditory prostheses.