Biological Substrates for Language

描述(由申请人提供)：拟议研究的长期目标是了解大脑语言偏侧化的个体差异背后的生物学机制。了解决定正常脑组织固有变异性的因素对于有效治疗单侧脑损伤患者至关重要。研究认为，个体在左脑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学意义。一大批正常人将在一系列语言任务中进行测试，在这些任务中，刺激被呈现在左右半球。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)将被用来评估大脑后部(颞面、顶面、Heschl回)和前部(三角部、扣带状回和旁扣带沟)的不对称性。研究假设：(1)关键皮层区域的不对称程度不同，并且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不同，一些人在任务和大脑区域之间表现出一致的中等不对称模式，而另一些人则表现出行为和解剖上的不对称，这些不对称是随机偏离总体平均水平的；(3)具有一致的典型不对称的个体在各种非偏侧化词汇任务中将表现出更快的速度和准确性。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，研究未受损伤人群的个体差异可以为大脑偏侧化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.