Executive Control in the Bilingual Brain

个人描述（申请人提供）：双语能力强，语言控制能力强。他们似乎能够在交谈中毫不费力地在不同语言之间切换，但很少会说无意的语言。执行控制是语言控制的基础，这一假设在涉及执行控制的非语言任务中发现了双语优势。此外，功能磁共振成像研究表明，在任务转换和语言转换过程中，类似的大脑区域处于活跃状态。尽管这一证据令人信服，但任务控制和语言控制之间的细微差别可能被忽视了。我们提出了一种强有力的方法来检验双语者依靠一般执行控制来实现语言控制的假设，通过比较同一群体中直接的语言转换和任务转换。本研究的目的1将探讨任务和语言转换对年龄的影响。老年人似乎在执行功能和语言控制方面表现出明显的与年龄相关的变化。如果任务转换和语言转换是类似的过程，那么这两个任务的表现将是相关的，因此保留执行功能能力的老年人将保留语言控制能力。该研究的目标2增加了一个神经成像组件来研究同一组个体中的语言转换和任务转换。这样的比较允许对每个任务中涉及的区域进行良好控制的调查。双语者任务转换和语言转换之间相似的激活模式表明语言控制和执行控制的机制相似。另外，双语者语言转换和任务转换的可解离模式表明，语言控制背后存在着执行控制无法完全解释的其他机制。在这两个实验中，一组匹配的单语对照将为识别双语者独特的处理机制提供进一步的杠杆作用。该研究将详细阐述双语语言控制、执行控制及其在语言加工中的作用、老龄化语言系统的模型，并将为申请人提供在双语和老龄化领域取得成功的必要技能。

DESCRIPTION (provided by applicant): Bilinguals have powerful language control. They seem able to effortlessly switch between languages during conversation, but seldom produce words in an unintended language. A growing consensus in research on bilingualism is that executive control is the basis for language control, a hypothesis which led to the discovery of bilingual advantages in non-linguistic tasks involving executive control. Additionally, fMRI studies report similar brain regions active during task and language switching. Although this evidence is compelling, subtle differences between task and language control may be overlooked. We propose a powerful way to test the hypothesis that bilinguals rely on general executive control to achieve language control, by comparing language switching and task switching directly in the same group of individuals. Aim 1 of the proposed study will investigate age effects associated with task and language switching. Older adults appear to exhibit marked age-related shifts in executive function and language control. If task-switching and language-switching are analogous processes, performance on each of the two tasks will be related such that older adults who have preserved executive functioning abilities will have preserved language control abilities. Aim 2 of the proposed study adds a neuroimaging component that investigates language switching and task switching in the same group of individuals. Such a comparison allows for a well-controlled investigation of the regions involved in each task. Similar patterns of activation between task switching and language switching in bilinguals will suggest similar mechanisms underlying language control and executive control. Alternatively, dissociable patterns in language switching and task switching in bilinguals suggest additional mechanisms underlying language control not fully explained by executive control. In both experiments a group of matched monolingual controls will provide further leverage for identifying processing mechanisms unique to bilinguals. The proposed study will elaborate models of bilingual language control, executive control and its role in language processing, the aging language system, and will provide the applicant with skills necessary for leading a successful career in the field of bilingualism and aging. PUBLIC HEALTH RELEVANCE: Between1990 and 2000, the number of people who spoke a language other than English increased by 15 million. In addition, approximately 20 percent of people living in the United States are bilingual. Given the growth of bilinguals in the population, understanding mechanisms behind bilingualism is becoming increasingly important. Additionally, bilinguals offer a unique opportunity to investigate possible relationships between executive control and language processing. The proposed study intends to reveal cognitive and neural mechanisms supporting bilingual language control, and the consequences of aging and bilingualism for executive control. The results will also inform the development of valid cognitive assessments of bilinguals.