Neural mechanisms underlying the sensitive period for phonetic learning in infants at-risk for Developmental Language Disorder

项目总结/摘要 6~12月龄为语音学习的敏感期， 这是语言习得最早的里程碑之一， 在这段时间内可以可靠地预测以后的语言技能。最近，我的工作表明， 这是第一次，在这一时期，神经处理语音不仅可以预测个人语法， 6岁时的技能，而且在典型的发展中发展言语和语言障碍的风险 婴儿。这一结果表明敏感期的重要临床相关性，并证明 迫切需要进一步了解敏感期的潜在神经机制， 特别是它是否已经在发展语言障碍的高风险婴儿中改变， 例如发育性语言障碍（DLD）。阐明神经机制不会 只允许扩展的理论，以涵盖非典型语言的发展，但更多的 重要的是，帮助识别语言障碍的早期标记，并帮助开发有针对性的 早期干预。具体来说，敏感期的特点是言语上的分歧 处理，从而婴儿对母语对比的敏感性提高，而对 非母语言语对比下降。理论上说，这是一个专业化的过程， 语言，其中母语专业化程度较低与语言增长较慢有关。 然而，行为和功能神经影像学研究仅调查了典型的发展中国家， 婴儿（低风险），但不是有沟通障碍家族史的婴儿（高风险）。是 在此期间，可能已经出现了将高风险婴儿和这些婴儿分开的差异， 差异可能是高危人群后期语言困难的基础。当前的Katz ESI 该提案旨在转移重点，专门检查有家族病史的高危婴儿， DLD，并将其与低风险婴儿在~6（开始），~12（结束）和~14（延迟结束）进行比较。 敏感期）月龄，中心的理论假设是，高风险婴儿将 表现出较长的敏感期，或母语专业化落后于低风险 婴儿。特别是，我们研究了更高和更低水平的神经过程的讲话，以及 神经过程之间的联系与言语相关的高级过程 辨别是由失配反应（MMR）索引的，而较低水平的感觉编码 语音通过复杂听觉脑干反应（cABR）来索引。这两项措施将 脑磁图（Magnetoencephalography，MEG）拟议的研究将 有助于揭示非典型语言发展背后的神经机制， NIDCD的使命是研究言语和语言的无序过程。

Project Summary/Abstract The sensitive period for phonetic learning, which occurs between 6~12 months of age, is demonstrably one of the earliest milestones for language acquisition, as infants’ speech processing during this period can reliably predict later language skills. Most recently, my work has shown for the first time that neural processing of speech during this period can predict not only individual grammar skills at 6 years, but also the risk of developing speech and language disorders in typically developing infants. This result suggests an important clinical relevance of the sensitive period and demonstrates a crucial need to further understand the underlying neural mechanisms of the sensitive period, particularly whether it may already be altered in infants at high-risk of developing language disorders, such as the developmental language disorder (DLD). Elucidating the neural mechanism would not only allow for the expansion of theories to encompass atypical language development, but more importantly, help identify early markers for language disorders and aid in the development of targeted early interventions. Specifically, the sensitive period is characterized by a divergence in speech processing, whereby infants’ sensitivity for native speech contrasts improves while sensitivity for nonnative speech contrasts declines. It is theorized to be a specialization process for the native language, where less native language specialization is associated with slower language growth. However, behavioral and functional neuroimaging studies have only investigated typically developing infants (Low-Risk), but not infants with a family history of communication disorders (High-Risk). It is possible that differences already emerge during this period that separate High-Risk infants and these differences may underlie later language difficulties in the High-Risk population. The current Katz ESI proposal aims to shift the focus and specifically examine High-Risk infants with a family history of DLD and compare them with Low-Risk infants at ~6 (start), ~12 (end) and ~14 (delayed end of sensitive period) months of ages, with the central theoretical hypothesis that High-Risk infants would demonstrate a protracted sensitive period, or a lagged native language specialization than Low-Risk infants. Particularly, we examine both higher and lower levels of neural processes for speech, as well as in the link between the neural processes. The higher-level processes related to speech discrimination is indexed by the mismatch response (MMR) while lower-level sensory encoding of speech is indexed by the complex auditory brainstem response (cABR). Both measures will be obtained simultaneously with Magnetoencephalography (MEG). Together, the proposed study will help uncover neural mechanisms underlying atypical language development and perfectly aligns with the mission of NIDCD to conduct research in disordered processes of speech and language.