Biological Substrates for Language

描述（由申请人提供）：本研究的长期目标是了解语言脑侧化个体差异的生物学机制。为了有效治疗单侧脑损伤患者，了解决定正常脑组织固有变异性的因素至关重要。我们认为，个体在左半球优势的程度和一致性上存在差异，这些差异对语言加工具有行为意义。一大批正常人将在一系列语言任务中接受测试，在这些任务中，左脑和右脑都受到刺激。这些任务既测量基本的单词识别过程，也测量语义检索过程。结构磁共振成像（MRI）将评估脑后部（颞平面、顶平面、Heschl’s回）和前部（三角部、扣带和扣带旁沟）脑区域的不对称性。假设：(1)个体在关键皮质区域不对称的程度上存在差异，这种结构差异与语言功能的半球间组织有关；(2)个体不对称的一致性存在差异，有些人在任务和大脑区域之间具有一致的中度不对称模式，而另一些人则表现出随机偏离总体均值的行为和解剖不对称；(3)具有一致性、典型不对称的个体在各种非侧化词汇任务中表现出更高的速度和准确性。虽然对发育和获得性脑功能障碍的治疗是单独进行的，但对正常功能的理解主要是基于群体平均水平。因此，对未受伤人群个体差异的研究可以为大脑偏侧的基础科学及其临床应用提供重要的桥梁。

DESCRIPTION (provided by applicant): The long-term objective of the proposed research is to understand the biological mechanisms underlying individual differences in cerebral lateralization for language. Understanding the factors that determine the variability inherent in normal brain organization is essential in order to effectively treat individuals with unilateral brain injuries. It is proposed that individuals vary both in the degree and consistency of left hemisphere predominance and that these variations have behavioral significance for language processing. A large sample of normal persons will be tested in a series of linguistic tasks in which stimuli are presented to the left and right hemispheres. The tasks measure both basic word recognition, and semantic retrieval, processes. Structural magnetic resonance imaging (MRI) will be performed to assess asymmetries in posterior (planum temporale, planum parietale, Heschl's gyrus) and anterior (pars triangulars, cingulate and paracingulate sulcus) brain regions. It is hypothesized that (1) individuals differ in the extent to which critical cortical regions are asymmetrical and that this structural variability is linked to the inter-hemispheric organization of language function; (2) individuals differ in the consistency of their asymmetries such that some have a consistent pattern of moderate asymmetries across tasks and brain regions, while others show behavioral and anatomical asymmetries that depart from the population mean randomly; and (3) individuals with consistent, typical asymmetries will demonstrate greater speed and accuracy across a variety of nonlateralized lexical tasks. Although treatment for developmental and acquired brain dysfunction is administered individually, the understanding of normal function is based primarily on group averages. Hence, the study of individual differences in uninjured populations can provide a critical bridge between the basic science of cerebral lateralization and its clinical application.