Linguistic and Nonlinguistic Functions of Frontal Cortex

描述（申请人提供）：在过去的几十年里，认知神经科学在研究人类前额叶皮层（PFC）的功能方面经历了爆炸式的发展。我们支持的一个假设是，PFC的一个功能，可能是特定于左侧后部分，额下回（LIFG），是从竞争选项中选择信息。在当前的提案中，我们的目标是探索这种假设的选择机制与语言缺陷之间的关系，语言缺陷通常与该区域的脑损伤有关。一个多世纪以来，人们已经知道，左额叶的损伤会导致语言缺陷，这种缺陷的特征被描述为“不流利”，从没有语言输出到截断的语法短语。然而，近年来，在很大程度上基于结构和功能神经成像技术的出现，已经有可能超越广泛的解剖学相关性与失语综合征的临床描述。本实验旨在利用这两种技术，以便更好地描述PFC的结构-功能关系，并了解这些功能与与前额叶区域损伤相关的非流利性失语的临床表现之间的联系。本研究的主要目的是：(1)进一步建立PFC功能的统一理论；(2)将这一理论与该区域皮层损伤相关的临床综合征联系起来；(3)用我们的理论方法澄清关于非流利性失语的症状学和病变定位的不一致。该提案分为四个部分。在第一部分（语言流畅性）中，我们将研究竞争和集合大小对语义和音位流畅性的影响。在第二节（图片命名）中，我们将研究竞争和语境对词汇检索的影响。在第三节（词汇歧义）中，我们将研究歧义词解析过程中多重意义的抑制作用。在第四节（句法加工）中，我们将研究句法复杂性和歧义对句子理解的影响。

DESCRIPTION (provided by applicant): In the past few decades, cognitive neuroscience has experienced an explosion in research investigating the functions of human prefrontal cortex (PFC). One hypothesis that we have championed is that a function of PFC, perhaps specific to the posterior part of the left, inferior frontal gyrus (LIFG), is the selection of information from competing alternatives. In the current proposal, we aim to explore the relation between this putative selection mechanism and the language deficits that have often been associated with brain damage to this region. For more than a century, it has been known that lesions to the left frontal lobe produce linguistic deficits that are characteristically described as "nonfluent," ranging from no language output to truncated, agrammatical phrases. In recent years, however, it has been possible to move beyond broad anatomical correlations with a clinical description of aphasia syndromes, based in large part on the advent of structural and functional neuroimaging techniques. The experiments in this proposal are designed to take advantage of both of these techniques, in order to better describe structure-function relations in PFC, and to understand the link between these functions and the clinical picture of nonfluent aphasia that is associated with damage to prefrontal regions. The major aims of this line of research are as follows: (1) to further develop a unified theory of the functions of PFC; (2) to relate this theory to the clinical syndromes associated with damage to this region of cortex; (3) to clarify inconsistencies regarding symptomatology and lesion localization of nonfluent aphasias with our theoretical approach. The proposal is divided into four sections. In Section I (Verbal Fluency) we will examine the effects of competition and set size on semantic and phonemic fluency. In Section II (Picture Naming) we will examine competition and context effects on lexical retrieval. In Section III (Lexical Ambiguity) we will examine the inhibition of multiple meanings during the resolution of ambiguous words. In Section IV (Syntactic Processing) we will examine the effects of syntactic complexity and ambiguity on sentence comprehension.