Neural Basis of Lexical and Speech Processing

描述(申请人提供)：这项研究的目标是探索语音和词汇处理两个关键方面的神经系统：听者如何在许多可变性来源(物体恒定/不变问题)的情况下感知稳定的语音感知，以及他们如何从许多具有相同音形特征的单词中成功地选择合适的候选单词(语音竞争的解决方案)。一系列实验将调查语音类别在元音环境和不同说话者之间的不变性，以及发音的语音特征在发音地点和发音方式以及发音方式的不同之间的不变性。FMRI适应范式将被用来识别语音处理流中显示不同变异性来源下不变神经反应的大脑区域。颞区的不变神经反应表明，语音不变性来自不变的声学模式。额叶区域(包括额下回、运动前区和运动区)的不变神经反应表明，语音不变性来自共同的运动/发音手势。顶叶区域的不变神经反应表明，语音的恒定性来自于更高阶的抽象语音表征。在发音区域没有激活的情况下，IFG中不变的神经反应表明，语音的恒定性是由决策相关的过程决定的。第二个系列的实验将调查在语音竞争条件下招募的大脑区域。假设IFG是一种领域通用角色，因此将在语音竞争的条件下被招募。然而，假设IFG不对刺激的语音特性中固有的竞争做出反应，而是仅在竞争的解决中被招募，即当竞争表征被激活并且需要从这些竞争表征中选择一个单词时。相反，假设SMG被招募来获取单词的词汇形式，而不考虑选择需求，激活受语音竞争程度的调节。最后提出，语音竞赛在听觉单词识别和口语单词产生中都招募了相同的神经系统。在听觉单词识别中，将使用眼球追踪范式来研究词头竞争、词汇密度和语音中介竞争。在口语生产中，将使用单词阅读和图片命名范式来研究有声和无声竞争者的词汇产生，来自高密度和低密度邻域的词汇的产生，以及出现在同一语音竞争者集中的单词的产生与不在相同竞争者集中的单词的产生。

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.