Bidelman Gavin M, Bush Lauren C, Boudreaux Alex M
Institute for Intelligent Systems, University of Memphis, Memphis, TN, United States.
School of Communication Sciences and Disorders, University of Memphis, Memphis, TN, United States.
Front Neurosci. 2020 Feb 27;14:153. doi: 10.3389/fnins.2020.00153. eCollection 2020.
We investigated whether the categorical perception (CP) of speech might also provide a mechanism that aids its perception in noise. We varied signal-to-noise ratio (SNR) [clear, 0 dB, -5 dB] while listeners classified an acoustic-phonetic continuum (/u/ to /a/). Noise-related changes in behavioral categorization were only observed at the lowest SNR. Event-related brain potentials (ERPs) differentiated category vs. category-ambiguous speech by the P2 wave (~180-320 ms). Paralleling behavior, neural responses to speech with clear phonetic status (i.e., continuum endpoints) were robust to noise down to -5 dB SNR, whereas responses to ambiguous tokens declined with decreasing SNR. Results demonstrate that phonetic speech representations are more resistant to degradation than corresponding acoustic representations. Findings suggest the mere process of binning speech sounds into categories provides a robust mechanism to aid figure-ground speech perception by fortifying abstract categories from the acoustic signal and making the speech code more resistant to external interferences.
我们研究了言语的范畴知觉（CP）是否也可能提供一种有助于在噪声中感知言语的机制。我们改变了信噪比（SNR）[清晰、0 dB、-5 dB]，同时让听众对一个声学语音连续体（/u/到/a/）进行分类。仅在最低信噪比时才观察到与噪声相关的行为分类变化。事件相关脑电位（ERP）通过P2波（约180 - 320毫秒）区分范畴性言语与范畴模糊性言语。与行为情况相似，对具有清晰语音状态（即连续体端点）的言语的神经反应在信噪比降至 -5 dB时对噪声仍具有稳健性，而对模糊性语音标记的反应则随着信噪比降低而下降。结果表明，语音表征比相应的声学表征更能抵抗降解。研究结果表明，仅仅将语音声音分类的过程就提供了一种稳健的机制，通过从声学信号中强化抽象范畴并使语音编码更能抵抗外部干扰，来辅助语音的前景 - 背景感知。
