Determinants of phonetic category structure in language impairment

项目摘要 特殊语言障碍（LI）是一种常见的儿童学习障碍，可以持续到成年， 影响了美国约7%的儿童。LI的特点是在获得 语言的各个方面，包括语言的声音结构、语法形态和句法结构。 控制词序的规则。在儿童时期被诊断患有LI的个体通常表现出增加的风险， 发展其他残疾，包括学习残疾和阅读残疾，除了增加 行为问题的风险和未能在学术环境中茁壮成长。拟议的长期目标 研究的目的是优化LI的神经和行为病因学的理论理解。虽然 已经进行了大量高质量的行为和基于大脑的研究，并为LI提供了信息 治疗，这项研究往往作出假设的完整性较低水平的语音技能在LI。 实现长期目标的第一步是检验LI反映神经系统缺陷的假设。 语音范畴结构的表征和功能可塑性。目的1使用功能磁共振成像神经成像， 研究大脑如何表征语音范畴结构。我们假设（1）儿童和成人 LI将显示颞顶脑处理语音类别的区域的刚性证据 结构和（2）语音类别结构变得更加明确的发展，如神经 与儿童相比，成人对类别善良性的编码更加分级。目标2使用行为任务， 考察语音范畴结构在信号驱动和词汇驱动下的功能可塑性 学习机制我们假设患有LI的儿童和成人将表现出能力下降， 作为暴露于不同分布的结果动态地修改到语音类别的映射 语音变异性。我们还假设，语言能力介导的词汇信息是如何使用， 动态调整知觉表征，并预测LI的儿童和成人将表现出 减弱了使用词汇信息修改到语音声音类别的映射的能力。相对于 以前的研究集中在静态感知空间中表征LI，这方面的创新 建议是研究支持可塑性的动态过程的神经和行为基础， 语音范畴结构这项研究提出了重要的理论和临床问题， 语言科学，神经生物学，语言障碍和临床实践领域，包括需要 从理论上理解语音范畴结构是如何形成和维持的， 发展轨迹实现这些目标将为改进 LI的病因学，可用于制定更有针对性的康复方案，以及未来 神经影像学研究，将能够进一步阐明LI和功能可塑性的神经基础。

PROJECT SUMMARY Specific language impairment (LI) is a common child learning disorder that can persist into adulthood and that affects approximately 7% of children in the United States. LI is characterized by marked deficits in acquiring aspects of language including the sound structure of language, grammatical morphology, and the syntactic rules that govern word order. Individuals who are diagnosed with LI in childhood often show increased risk of developing other disabilities including learning disability and reading disability, in addition to being at increased risk of behavioral problems and failure to thrive in academic environments. The long-term goal of the proposed research is to optimize a theoretical understanding of the neural and behavioral etiology of LI. Although a substantial amount of high quality behavioral and brain-based research has been conducted and informed LI treatment, this research has often made assumptions about the intact nature of lower-level phonetic skills in LI. The first step towards the long-term goal is to test the hypothesis that LI reflects deficits in the neural representation and functional plasticity of phonetic category structure. Aim 1 uses fMRI neuroimaging to examine how the brain represents phonetic category structure. We hypothesize that (1) children and adults with LI will show evidence of rigidity in the temporoparietal brain regions that process phonetic category structure and (2) phonetic category structure becomes more defined across development such the neural coding of category goodness is more graded in adults compared to children. Aim 2 uses behavioral tasks to examine functional plasticity of phonetic category structure with respect to signal-driven and lexically-driven learning mechanisms. We hypothesize that children and adults with LI will show a decreased ability to dynamically modify the mapping to phonetic categories as a consequence of exposure to different distributions of phonetic variability. We also hypothesize that language ability mediates how lexical information is used to dynamically adjust perceptual representations and predict that children and adults with LI will show an attenuated ability to modify the mapping to speech sound categories using lexical information. With respect to previous research that has focused on characterizing LI in a static perceptual space, the innovation in this proposal is examining the neural and behavioral basis of the dynamic processes that support plasticity of phonetic category structure. The proposed research addresses important theoretical and clinical problems in the fields of language science, neurobiology, language impairment, and clinical practice including the need for a theoretical understanding of how phonetic category structure is formed and maintained across the developmental trajectory. Achieving these aims will lay important groundwork for improved specification of etiology of LI, which can be used to develop more targeted rehabilitation protocols, as well as for future neuroimaging studies that will be able to further explicate the neural basis of LI and functional plasticity.