Neural Basis of Lexical and Speech Processing

描述（由申请人提供）：本研究的目标是探索语音和词汇处理的两个关键方面的神经系统：听者如何在许多变化来源（对象恒常性/不变性问题）下感知稳定的语音感知，以及他们如何成功地从许多具有相同音形属性的单词中选择合适的候选单词（语音竞争的解决）。一系列实验将研究语音类别在不同元音环境和不同说话人之间的不变性，以及发声的语音特征在不同的发音地点和方式之间的不变性，以及发音方式在不同的声音和发音地点之间的不变性。fmri适应范式将用于识别语音处理流中在不同变异性来源下显示不变神经反应的大脑区域。颞区不变的神经反应表明，语音不变源于不变的声学模式。包括额下回（IFG）、前运动区和运动区的不变神经反应表明，语音不变源于共同的运动/发音手势。顶叶区域的不变神经反应表明语音恒常性来自于高阶抽象语音表征。在没有发音区激活的情况下，IFG中不变的神经反应表明语音的稳定性是由与决策相关的过程决定的。第二个系列的实验将研究在语音竞争条件下招募的大脑区域。据推测，IFG起着一个领域的一般作用，因此在语音竞争的条件下会被招募。然而，假设IFG对刺激的语音特性中固有的竞争没有反应，而只在竞争的解决中被招募，即当竞争表征被激活时，需要从这些竞争表征中选择一个词。相反，我们假设SMG在获取单词的词汇形式时被招募，而不受选择需求的影响，激活受语音竞争程度的调节。最后，提出语音竞争在听觉单词识别和口语单词产生中招募相同的神经系统。在听觉词识别中，将使用眼动追踪范式来研究开始竞争、词汇密度和语音介导的竞争。在口语单词产生中，单词阅读和图片命名范式将用于研究有和没有发音竞争对手的单词的产生，来自高密度和低密度邻居的单词的产生，以及在相同语音竞争对手集合中呈现的单词的产生和不在相同竞争对手集合中的单词的产生。拟议中的研究增加了我们对参与言语和文字处理的大脑区域的了解。该结果为理解脑损伤失语症患者的这种缺陷的基础，识别脑损伤后恢复过程中可能招募的大脑区域，以及为言语和语言缺陷患者制定潜在的康复策略提供了关键的基线数据。提出的理论方法和方法可以应用于其他认知系统，为探索其他认知过程背后的大脑功能提供了一种手段。

DESCRIPTION (provided by applicant): The goal of this research is to explore the neural systems underlying two critical aspects of speech and lexical processing: how listeners perceive a stable phonetic percept despite many sources of variability (the object constancy/invariance problem) and how they successfully select the appropriate word candidate from the many words that share sound shape properties (the resolution of phonological competition). One series of experiments will investigate invariance for phonetic categories across vowel environments and different speakers, and invariance for the phonetic feature of voicing across variations in place and manner of articulation and manner of articulation across variations in voice and place of articulation. An fMRI-adaptation paradigm will be used to identify brain regions in the phonetic processing stream that show invariant neural responses under different sources of variability. Invariant neural responses in temporal areas would suggest that phonetic invariance derives from invariant acoustic patterns. Invariant neural responses in frontal areas including the inferior frontal gyrus (IFG), premotor, and motor areas would suggest that phonetic invariance derives from shared motor/articulatory gestures. Invariant neural responses in parietal areas would suggest that phonetic constancy derives from higher order abstract phonological representations. And invariant neural responses in the IFG in the absence of activation of articulatory areas would suggest that phonetic constancy is determined by decision-related processes. A second series of experiments will investigate the brain regions recruited under conditions of phonological competition. It is hypothesized that the IFG serves a domain general role and hence will be recruited under conditions of phonological competition. However, it is hypothesized that the IFG is not responsive to competition inherent in the phonological properties of the stimulus but is recruited only in the resolution of competition, i.e. when competing representations are activated and a word needs to be selected from among these competing representations. In contrast, it is hypothesized that the SMG is recruited in accessing the lexical form of a word irrespective of selection demands with activation modulated by the degree of phonological competition. Finally, it is proposed that phonological competition recruits the same neural systems in both auditory word recognition and spoken word production. In auditory word recognition, an eyetracking paradigm will be used to investigate onset competition, lexical density, and phonologically mediated competition. In spoken word production, word reading and picture naming paradigms will be used to investigate the production of words with and without voiced competitors, the production of words from high versus low density neighborhoods, and the production of words presented in the same phonological competitor set versus those not in the same competitor set. PUBLIC HEALTH RELEVANCE The proposed research adds to our knowledge of the brain areas involved in the processing of speech and words. The results provide critical baseline data for understanding the bases of such deficits in brain-injured patients with aphasia, for identifying those areas of the brain that may be recruited in recovery processes subsequent to brain injury, and for potentially developing rehabilitative strategies for patients with speech and language deficits. The theoretical approach and methods proposed can be applied to other cognitive systems, providing a means of exploring brain function underlying other cognitive processes.