Neural Basis of Lexical and Speech Processing

描述（由申请人提供）：本研究的目标是利用事件相关功能磁共振成像（fMRI）了解语音词汇处理系统的功能架构如何映射到其底层的神经系统。两个假设将被调查，两者探索神经系统背后的听觉语音和词汇处理的计算特性。第一个假设探讨两个脑半球的计算机制是否优先处理语音信号的不同特性。一系列使用语音辨别和语音分类任务的实验将检查辅音和元音感知的一些声学-语音参数，包括辅音感知中的语音起始时间和形成峰频率持续时间，以及元音感知中的持续时间和形成峰频率（F - f2）空间。我们假设，由于语音结构在语言加工中的功能作用，与语音类别相对应的声学特性将优先由左半球处理，而不考虑其声学结构。相反，我们假设右半球的激活将被语音信号固有的声学特性调制。第二个假设探讨语音词汇处理系统的计算特性如何映射到其神经基质上。据推测，在语音、词汇和/或语义竞争的条件下，左额叶的激活会增加。语音竞争将通过探索声音结构和范例与对比的接近程度来研究，因此，竞争的语音类别影响额叶激活。词汇竞争将通过探讨语音因素对词汇竞争的影响和语音因素对词汇邻域密度的影响来研究。语义竞争将通过探索语义歧义词与无歧义词对神经激活模式的影响来研究。

DESCRIPTION (provided by applicant): The goal of this research is to understand how the functional architecture of the speech-lexical processing system maps on to the neural systems underlying it using event-related functional magnetic resonance imaging (fMRI). Two hypotheses will be investigated, both exploring the neural systems underlying the computational properties of auditory speech and lexical processing. The first hypothesis explores whether the computational mechanisms of the two hemispheres preferentially process different properties of the speech signal. A series of experiments using both speech discrimination and phonetic categorization tasks will examine a number of acoustic-phonetic parameters underlying both consonant and vowel perception including voice-onset time and formant frequency duration in the perception of consonants, and duration and formant frequency (F l-F2) space in the perception of vowels. It is hypothesized that the acoustic properties corresponding to the phonetic categories of speech will be preferentially processed by the left hemisphere irrespective of their acoustic structure owing to the functional role that sound structure plays in language processing. In contrast, it is hypothesized that activation of the right hemisphere will be modulated by the inherent acoustic properties of the speech signal. The second hypothesis explores how the computational properties of the speech lexical processing system map on to its neural substrate. It is hypothesized that there will be increased left frontal activation under conditions of phonetic-phonological, lexical, and/or semantic competition. Phonetic competition will be investigated by exploring the extent to which acoustic-phonetic structure and the proximity of an exemplar to a contrasting, and hence, competing phonetic category influences frontal activation. Lexical competition will be investigated by exploring the influence of phonetic factors on lexical competition and phonological factors on lexical neighborhood density. Semantic competition will be investigated by exploring the effects of semantically ambiguous words compared to unambiguous words on neural activation patterns.