Neurophysiological basis of speech perception

描述(申请人提供)：我们建议继续研究言语知觉的神经生理学基础，特别强调在听觉和语音知觉中的作用，在左侧上颞沟(STS)及其附近的中后野，使用一个全面的神经成像方法在健康成人和儿童。左侧STS的中间部分(MSTS)正好位于Heschl回(HG)的前部和腹侧，它对包括词汇前片段(如孤立音节和音素)在内的言语以及非语言熟悉的声音(如非言语的人声和动物声)做出反应。我们的主要假设是，从HG到MSTS的腹侧通路介导了将语音波形中顺序的、时序的声学信息映射到MSTS中存储的语言相关的、高度抽象的和范畴的表征的高效过程。我们建议研究这一通路的时空组织及其对音素知觉的特异性。HG后左侧STS(PSTS)与非母语语音和其他新声音的学习、语音(语音加工)和其他听觉序列的提取和复述以及发音规划有关。双侧的PSTS也对生物运动的感知做出反应。我们的主要假设是，左侧psts的一个区域充当工作记忆缓冲区，暂时存储具有低抽象水平的真实表征，保留语音处理和发音规划所需的声音的顺序、时间属性。同样，pSTS的区域对生物运动有反应，因为它的感知中心是时间维度。我们建议研究这一区域在语音和生物运动知觉中的共同作用，以及在形成新声音的瞬时真实表征方面的作用。与成人相比，仍在发展音素知觉的儿童在音素类别之间的界限较浅。儿童对语音的激活模式也更加分散，包括左额叶和运动前皮质，以及更多后部的颞叶受累。然而，与成人相比，儿童在非母语音素类别的习得上表现出更大的可塑性。我们建议比较儿童和成人学习非母语语音对比的能力，假设最初是通过在PSTS中形成具有低水平抽象的瞬时真实表征，最终通过在MSTS中形成长期的高度抽象的、范畴的神经表征。我们将从音素范畴表征的发展速度和局限性以及音素知觉习得的神经机制方面考察发育和成熟的大脑。公共卫生相关性：在拟议的实验中，我们提供了一个理论框架，用于定义言语和听觉的中间和后部颞区的功能分化。了解这些区域各自的作用可能会提出一些方法，以改进与音素感知缺陷相关的障碍的治疗，特别是阅读障碍。描述涉及语音处理不同方面的皮质区域是努力开发皮质功能图和优化术前语言映射程序的重要组成部分。这项拟议的研究还将为语音习得的发展模式提供信息。

DESCRIPTION (provided by applicant): We propose to continue to study the neurophysiological basis of speech perception with particular emphasis on the role in auditory and phonemic perception of middle and posterior fields in and near the left superior temporal sulcus (STS), using a comprehensive neuroimaging approach in healthy adults and children. The middle portion of the left STS (mSTS), just anterior and ventral to Heschl's gyrus (HG), is responsive to speech utterances including prelexical segments such as isolated syllables and phonemes, as well as non linguistic familiar sounds such as nonspeech human vocalizations and animal vocalizations. Our principal hypothesis is that the ventral pathway from HG to mSTS mediates the highly-efficient process of mapping the sequential, chronological acoustic information in speech waveforms onto linguistically relevant, highly-abstract and categorical representations stored in mSTS. We propose to examine the spatiotemporal organization of this pathway and its specificity for phonemic perception. The left STS posterior to HG (pSTS) has been implicated in the learning of non-native speech and other novel sounds, in the retrieval and rehearsal of speech (phonological processing) and other auditory sequences and in articulatory planning. The pSTS, bilaterally, also responds to the perception of biological motion. Our principal hypothesis is that a region of the left pSTS acts as a working-memory buffer, transiently storing veridical representations with low-levels of abstraction, that retain the sequential, chronological properties of sounds necessary for phonological processing and articulatory planning. Similarly, regions of the pSTS are responsive to biological motion because of the temporal dimension central to its perception. We propose to examine the common role of this region in speech and biological motion perception and in forming transient veridical representations for novel sounds. Children still developing phonemic perception compared to adults display shallower boundaries between phonemic categories. Children also display a pattern of activation for speech sounds that is more distributed, including left frontal and premotor cortex and a more posterior involvement of the temporal lobes. However, children demonstrate greater plasticity in the acquisition of non-native phoneme categories compared to adults. We propose to compare the ability of children and adults to learn a non-native phonetic contrast, presumably initially through formation of transient veridical representations with low-levels of abstraction in pSTS and eventually through formation of long-term highly-abstract, categorical neural representations in mSTS. We will examine the developing and mature brain with regard to the rate and limitations in the development of phonemic category representations and the neural mechanisms underlying acquisition of phonemic perception. PUBLIC HEALTH RELEVANCE: In the proposed experiments, we provide a theoretical framework for defining the functional differentiation of middle and posterior temporal regions for speech and auditory perception. Understanding the respective role of these regions may suggest means of improving the treatment of disorders associated with deficits in phonemic perception and in particular dyslexia. Delineating the cortical areas involved in different aspects of speech processing is an important building block in the effort to develop a functional map of the cortex and for optimizing presurgical language mapping procedures. The proposed studies will also inform developmental models of speech acquisition.