Neural encoding of speech envelopes during development: A frequency-specific investigation

项目摘要 在安静和存在噪声的情况下理解语音的一个重要的基于时间的线索是语音的周期性。 在基频（f0）处发声。儿童使用f0速率信息进行言语理解的能力- 这取决于他们的听觉系统在每个频率区域提取信息的能力。的能力 提取这些信息的能力可能受到耳蜗部位特异性神经通路发育的影响 以及听觉处理在支配耳蜗基底的通路中更早发展的趋势。f0编码， 可以使用包络跟随反应（EFR）进行评估-一种基于脑电图的方法， 反映相位锁定到周期性f0包络的神经活动。然而，人们对频率知之甚少- f0编码的特殊发展，因为主要使用宽带元音来引出EFR。本 最后，我们的目标是系统地评估f0编码的频率特异性发展时间过程。 这项研究将使用新的限带语音刺激来研究 f0编码在对应于低、中和高频率的不同耳蜗区域中启动。除了 使用频率特定的方法，f0编码将被评估为（i）f0速率的函数-一个参数， 由谈话者年龄和性别的变化，（ii）降低信噪比-一个参数，模拟具有挑战性的 听力条件，特别是儿童，和（iii）行为相关的刺激-一个参数，可以 消除日常听力体验的影响。两个儿童年龄组的利益与不成熟的 f0速率包络周期的感知为0.3-1年和5-8年，因为它们与成熟耳蜗一致，以及 耳蜗和脑干功能。对于f0编码的严格成人-儿童比较， 年龄相关的耳朵和头部的大小，该方法将需要：（i）刺激校准在每个测试耳朵，以均衡 在所有测试耳朵上刺激水平，（ii）使用相位相干性-独立于 绝对反应强度和潜伏期-作为成熟度指标，以及（iii）刺激的组间比较- 诱导的变化，而不是原始的EFR措施。研究结果将揭示低频f0编码是否是最后一个 以实现类似成人的处理，如果这样的发展轨迹是特定的言语。 这项研究对耳蜗性听力损失的儿童有重要的意义， 频率特异性异常f0编码作为听力损失程度的函数。年龄、频率、速率、信号- 从拟议的工作中开发f0编码的信噪比和刺激特异性将提高我们的能力。 为了检测和评估由于耳蜗听力损失和/或信号引起的异常f0编码的性质和程度 在助听器等设备中进行处理。使用EFR也将能够评估儿童的f0编码 年轻人参加行为听力测试，反过来，提供机会，告知干预的变化 比行为听力测试更早

Project Summary An important time-based cue for understanding speech in quiet and in the presence of noise is the periodicity in voicing at the fundamental frequency (f0). The ability of children to use f0-rate information for speech understand- ing depends on how well their auditory system extracts this information in each frequency region. The ability to extract such information could be influenced by the cochlear-place-specific development of neural pathways and the tendency for auditory processing to develop earlier in pathways innervating the cochlear base. f0 encod- ing can be evaluated using envelope following response (EFRs)—an electroencephalogram-based method that reflects neural activity phase-locked to the periodic f0 envelope. However, little is known about the frequency- specific development of f0 encoding because of the predominant use of broadband vowels to elicit EFRs. To this end, our goal is to systematically evaluate the frequency-specific developmental time course of f0 encoding. The proposed studies will use novel band-limited speech stimuli to investigate the developmental time course of f0 encoding initiated in different cochlear regions corresponding to low, mid and high frequencies. In addition to using a frequency-specific approach, f0 encoding will be assessed as a function of (i) f0 rate—a parameter that changes by talker age and gender, (ii) decreasing signal-to-noise ratio—a parameter that simulates challenging listening conditions especially for children, and (iii) behavioral relevance of the stimulus—a parameter that can disambiguate the impact of everyday listening experience. The two pediatric age groups of interest with immature perception of f0-rate envelope periodicity are, 0.3-1 years and 5-8 years, as they align with mature cochlear, and cochlear and brainstem function, respectively. For rigorous adult-child comparisons of f0 encoding in the presence of age-dependent ear and head sizes, the approach will entail: (i) stimulus calibration in each test ear to equalize stimulus level across all test ears, (ii) use of phase coherence—a normalized response measure independent of absolute response strength and latency—as the maturity metric, and (iii) between-group comparisons of stimulus- induced changes rather than raw EFR measures. Findings will reveal if f0 encoding at low frequencies is the last to achieve adult-like processing and if such a developmental trajectory is specific to speech. The proposed research has important implications for children with cochlear hearing loss who may experience frequency-specific abnormal f0 encoding as a function of hearing loss degree. The age-, frequency-, rate-, signal- to-noise ratio-, and stimulus-specific development of f0 encoding from the proposed work will advance our ability to detect and assess the nature and extent of abnormal f0 encoding due to cochlear hearing loss and/or signal processing in devices like hearing aids. The use of EFRs will enable assessment of f0 encoding in children too young to participate in behavioral hearing tests and in turn, offer the opportunity to inform changes in intervention earlier than behavioral hearing tests can.