Nonlinear auditory models yield new insights into representations of vowels
Nonlinear auditory models yield new insights into representations of vowels
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DOI：
10.3758/s13414-018-01644-w
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发表时间：
2019-05-01
影响因子：
1.7
通讯作者：
McDonough, Joyce M.
中科院分区：
文献类型：
--
作者：
Carney, Laurel H.;McDonough, Joyce M.
元音系统的研究经常呼吁需要了解听觉系统如何编码和处理声学信号中的信息。本研究的目的是提出计算模型来解决这一需求，并使用该模型来说明在两个层次的听觉通路的元音反应。许多以前用于研究语音听觉表征的模型都是基于模拟内耳调谐的线性滤波器组。这些模型不包含内耳的关键非线性响应特性，这些特性影响对话语音声级下的响应。这些非线性特性以对于理解中枢神经系统中的反应很重要的方式塑造神经表征。这里使用的神经纤维模型结合了与基底膜，内毛细胞（IHC）和IHC-AN突触相关的现实非线性特性。这些非线性建立了f 0相关波动的轮廓，这些波动在整个频率调谐AN纤维群体中的振幅变化。AN响应的振幅波动在共振峰附近最小，在共振峰之间的频率处最大。这些与f0相关的波动强烈地刺激或抑制听觉中脑中的神经元，听觉中脑是听觉通路的第一级，声音中的低频波动发生调谐。共振峰相关的振幅波动提供了在中脑神经元放电率的元音频谱的表示。中脑中的这些表征在广泛的声级范围内是鲁棒的，包括整个对话语音电平范围，并且存在现实的背景噪声电平。
Studies of vowel systems regularly appeal to the need to understand how the auditory system encodes and processes the information in the acoustic signal. The goal of this study is to present computational models to address this need, and to use the models to illustrate responses to vowels at two levels of the auditory pathway. Many of the models previously used to study auditory representations of speech are based on linear filter banks simulating the tuning of the inner ear. These models do not incorporate key nonlinear response properties of the inner ear that influence responses at conversational-speech sound levels. These nonlinear properties shape neural representations in ways that are important for understanding responses in the central nervous system. The model for auditory-nerve (AN) fibers used here incorporates realistic nonlinear properties associated with the basilar membrane, inner hair cells (IHCs), and the IHC-AN synapse. These nonlinearities set up profiles of f0-related fluctuations that vary in amplitude across the population of frequency-tuned AN fibers. Amplitude fluctuations in AN responses are smallest near formant peaks and largest at frequencies between formants. These f0-related fluctuations strongly excite or suppress neurons in the auditory midbrain, the first level of the auditory pathway where tuning for low-frequency fluctuations in sounds occurs. Formant-related amplitude fluctuations provide representations of the vowel spectrum in discharge rates of midbrain neurons. These representations in the midbrain are robust across a wide range of sound levels, including the entire range of conversational-speech levels, and in the presence of realistic background noise levels.