Weissberger Gali H, Gollan Tamar H, Bondi Mark W, Clark Lindsay R, Wierenga Christina E
San Diego State University/University of California, San Diego, Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Ct. #103, San Diego 92120-4913, United States.
Department of Psychiatry, University of California, San Diego, 9500 Gilman Dr., MC: 0603, La Jolla, CA 92093-0603, United States.
Neuropsychologia. 2015 Jan;66:193-203. doi: 10.1016/j.neuropsychologia.2014.10.037. Epub 2014 Nov 14.
Bilinguals' ability to control which language they speak and to switch between languages may rely on neurocognitive mechanisms shared with non-linguistic task switching. However, recent studies also reveal some limitations on the extent control mechanisms are shared across domains, introducing the possibility that some control mechanisms are unique to language. We investigated this hypothesis by directly comparing the neural correlates of task switching and language switching. Nineteen Spanish-English bilingual university students underwent a functional magnetic resonance imaging (fMRI) study employing a hybrid (event-related and blocked) design involving both color-shape switching and language switching paradigms. We compared the two switching tasks using within-subject voxel-wise t-tests for each of three trial types (single trials in single blocks, and stay and switch trials in mixed blocks). Comparing trial types to baseline in each task revealed widespread activation for single, stay, and switch trials in both color-shape and language switching. Direct comparisons of each task for each trial type revealed few differences between tasks on single and switch trials, but large task differences during stay trials, with more widespread activation for the non-linguistic than for the language task. Our results confirm previous suggestions of shared mechanisms of switching across domains, but also reveal bilinguals have greater efficiency for sustaining the inhibition of the non-target language than the non-target task when two responses are available. This efficiency of language control might arise from bilinguals' need to control interference from the non-target language specifically when not switching languages, when speaking in single- or mixed-language contexts.
双语者控制自己说哪种语言以及在不同语言之间切换的能力，可能依赖于与非语言任务切换共享的神经认知机制。然而，最近的研究也揭示了跨领域共享控制机制的程度存在一些局限性，这表明某些控制机制可能是语言所特有的。我们通过直接比较任务切换和语言切换的神经关联来研究这一假设。19名西班牙裔-英语双语大学生参与了一项功能磁共振成像（fMRI）研究，该研究采用了一种混合（事件相关和组块）设计，涉及颜色-形状切换和语言切换范式。我们使用受试者内体素水平的t检验，对三种试验类型（单个组块中的单个试验，以及混合组块中的维持和切换试验）分别比较了这两种切换任务。将每个任务中的试验类型与基线进行比较，结果显示在颜色-形状切换和语言切换中，单个试验、维持试验和切换试验均出现广泛激活。对每种试验类型的每个任务进行直接比较，结果显示在单个试验和切换试验中任务之间的差异很小，但在维持试验期间任务差异很大，非语言任务的激活比语言任务更广泛。我们的结果证实了之前关于跨领域切换存在共享机制的观点，但也表明当有两种反应可供选择时，双语者在维持对非目标语言的抑制方面比非目标任务具有更高的效率。这种语言控制效率可能源于双语者在不切换语言时，即在单语或混合语语境中说话时，需要特别控制来自非目标语言的干扰。
