Neural Substrates of Component Lexical Semantic Processes

描述(申请人提供)：从单词中提取意义(词汇语义)是正常语言功能的关键。词汇语义损伤可以由多种原因引起，包括发育异常、中风和退行性疾病，但也可能反映对一个或多个成分加工的损害。当前的语言模型已经识别了词汇语义系统的两个本质上不同的组件：1)自动组件使得能够在词汇输入的毫秒内快速访问语义；以及2)受控组件发展较慢，并且引导对未自动恢复的语义信息的策略性检索。此外，与这些成分相关的一些过程被认为取决于传入刺激的形式。该项目的目标是确定在视觉和听觉模式内和跨视觉和听觉模式的词汇语义系统的这些行为可分离的自动和控制组件之间的神经关联。在一项初步研究中，我们使用事件相关功能磁共振成像和启动词汇判断任务，在健康志愿者中确定了视觉线索自动和受控词汇语义加工的可分离神经关联。一系列类似的研究被提出，以更准确地表征几个额叶和颞叶大脑区域在词汇语义系统组成部分中的作用。该设计的新颖之处在于，将使用与行为研究中使用的相同的随机设计，直接比较自动和受控的语义启动条件。有三个目标。第一个目标是更准确地表征左额叶在词汇语义信息的视觉线索控制提取中的作用。第二个目标是更准确地刻画左颞区在视觉线索自动词汇语义加工中的作用。第三个目标是确定听觉提示词汇语义中涉及的神经区域，这些神经区域与视觉提示词汇语义中涉及的神经区域重叠，并与之分离。识别与从词中提取意义的成分过程相关的神经系统对于理解词汇语义系统的结构和组织至关重要，应该有助于语言障碍的诊断和康复。

DESCRIPTION (provided by applicant): Extracting meaning from words (lexical semantics) is critical to normal language functioning. Lexical semantic impairment can result from a variety of causes including developmental abnormalities, stroke and degenerative diseases but may reflect damage to one or more component processes. Current language models have identified two qualitatively different components of the lexical semantic system: 1) An automatic component enables rapid access to semantics within milliseconds of lexical input; and 2) a controlled component evolves more slowly and guides strategic retrieval of semantic information not recovered automatically. In addition, some processes associated with these components are thought to depend upon the modality of incoming stimuli. The objective of the project is to identify the neural correlates of these behaviorally separable automatic and controlled components of the lexical semantic system, within and across visual and auditory modalities. In a preliminary study, we identified dissociable neural correlates of visually cued automatic and controlled lexical semantic processing in healthy volunteers using event-related fMRI and a primed lexical decision task. A series of similar studies are proposed to characterize more precisely the roles of several frontal and temporal lobe brain regions in components of the lexical semantic system. The design is novel in that automatic and controlled semantic priming conditions will be compared directly, using randomized designs identical to those used in behavioral research. There are three goals. The first goal is to characterize more precisely the role of a left frontal region in visually cued controlled retrieval of lexical semantic information. The second goal is to characterize more precisely the role of a left temporal region in visually cued automatic lexical semantic processing. The third goal is to identify neural regions involved in auditorily cued lexical semantics that overlap, and are dissociable from, those involved in visually cued lexical semantics. Identifying neural systems associated with component processes involved in extracting meaning from words is of central importance to understanding the structure and organization of the lexical semantic system and should aid diagnosis and rehabilitation of language disorders.