Neural and Perceptual Mechanisms for Coding Frequency Modulation

频率和幅度的调制是自然声音的基本属性。调频 (FM)对于声音分离、说话者识别以及语音和音乐中的韵律跟踪是必不可少的。 调频敏感度随着正常老化和听力损失而下降，从而限制了人的沟通能力 年龄较大和听力受损的人。重要的是，助听设备，如助听器和 人工耳蜗术在恢复FM敏感度方面并不成功。这种限制在一定程度上是由于 对FM编码背后的神经和知觉机制的理解不完全。人类调频 在低速率(FM&lt；~5-10 Hz)和载波频率(fc&lt；4-5 kHz)也是最大的情况下，感知效果最好 与语音和音乐相关，敏感度在更快的速率和/或更高的载波上恶化。这些费率和 人们普遍认为，载波相关的趋势反映了FM编码的双重机制：一种基于 关于时间精细结构(TFS；时间码)的精确锁相，以及基于时间码保真度的锁相 声调轴上的耳蜗滤波和幅度调制(AM)处理(包络/位置编码)。 至关重要的是，低速率、低载波调频已被视为单声道的金标准行为测量 TFS编码。这项拟议的研究将结合心理声学、计算模型和 脑电(EEG)，以测试假设，神经和知觉调频敏感性在正常- 听觉听者可以用一个单一的神经位置编码来解释。目标1将提供对以下方面的新见解 时间编码在年轻听力正常听者调频检测中的必要性 当使用新的幅度调制刺激时，也发现了时间编码的行为证据 没有TFS提示。目标2使用一种严格的大规模方法来测试知觉和神经退化 在缓慢的FM处理中，随着年龄的增长，可以通过TFS编码来解释，就像目前认为的那样，或者无论这些 变化也可以在基于位置编码的统一框架内解释。这一目标具有重要的意义 临床意义，因为它提供了第一次大规模复制和推广新的脑电测量， FM跟随响应(FMFR)，声称它反映了TFS编码对慢FM的个体保真度。 本研究结果将为今后有关听障人士的研究提供初步数据和基础 确定这些关键声学提示如何受到不同类型和程度的听力损失的影响，以及如何 知觉反应和神经反应都可以在统一的理论框架内解释，以便 为未来的感官干预提供了新的基础。

Modulations in frequency and amplitude are fundamental attributes of natural sounds. Frequency modulation (FM) is essential for sound segregation, talker recognition, and the tracking of prosody in speech and music. FM sensitivity degrades with normal aging and hearing loss, thereby restricting the communication abilities of older and hearing-impaired individuals. Importantly, assistive listening devices, such as hearing aids and cochlear implants, have not been successful in restoring FM sensitivity. This limitation is in part due to an incomplete understanding of the neural and perceptual mechanisms underlying FM coding. Human FM perception is best at the low rates (fm < ~5-10 Hz) and carrier frequencies (fc < 4-5 kHz) that are also most relevant for speech and music, with sensitivity worsening at faster rates and/or higher carriers. These rate and carrier-dependent trends are widely believed to reflect dual mechanisms for FM coding: one mechanism based on precise phase-locking to temporal fine structure (TFS; time code), and another based on the fidelity of cochlear filtering across the tonotopic axis and amplitude modulation (AM) processing (envelope/place code). Crucially, slow-rate, low-carrier FM has been treated as the gold standard behavioral measure for monaural TFS coding. The proposed research will use a combination of psychoacoustics, computational modeling, and electroencephalography (EEG) to test the hypothesis that neural and perceptual FM sensitivity in normal- hearing listeners can instead be explained by a unitary neural place code. Aim 1 will provide new insights into the necessity of time coding in FM detection in young, normal-hearing listeners by testing whether classic behavioral evidence for time coding is also found when using novel amplitude-modulated stimuli that provide no TFS cues. Aim 2 uses a rigorous, large-scale approach to test whether perceptual and neural degradations in slow FM processing with age can be accounted for by TFS coding, as currently believed, or whether these changes too can be explained within the unified framework based on place coding. This aim has important clinical implications, as it provides the first large-scale replication and extension of a new EEG measure, the FM following response (FMFR), which has been claimed to reflect individual fidelity of TFS coding to slow FM. The results will provide the preliminary data and foundation for future studies with hearing-impaired listeners to determine how these critical acoustic cues are affected by different types and degrees of hearing loss and how both perceptual and neural responses can be explained within a unifying theoretical framework in order to provide a novel basis for future sensory interventions.