Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-Ku, Tokyo, 153-8902, Japan.
Department of Linguistics and Philosophy, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 32-D808, Cambridge, MA, 02139, USA.
Sci Rep. 2024 Jan 2;14(1):54. doi: 10.1038/s41598-023-50896-6.
It has been argued that the principles constraining first language acquisition also constrain second language acquisition; however, neuroscientific evidence for this is scant, and even less for third and subsequent languages. We conducted fMRI experiments to evaluate this claim by focusing on the building of complex sentence structures in Kazakh, a new language for participants having acquired at least two languages. The participants performed grammaticality judgment and subject-verb matching tasks with spoken sentences. We divided the participants into two groups based on the performance levels attained in one of the experimental tasks: High in Group I and Low in Group II. A direct comparison of the two groups, which examined those participants who parsed the structures, indicated significantly stronger activations for Group I in the dorsal left inferior frontal gyrus (L. IFG). Focusing on Group I, we tested the contrast between the initial and final phases in our testing, which examined when the structures were parsed, as well as the contrast which examined what structures were parsed. These analyses further demonstrated focal activations in the dorsal L. IFG alone. Among the individual participants, stronger activation in the dorsal L. IFG, measured during the sentence presentations, predicted higher accuracy rates and shorter response times for executing the tasks that followed. These results cannot be explained by task difficulty or memory loads, and they, instead, indicate a critical and consistent role of the dorsal L. IFG during the initial to intermediate stages of grammar acquisition in a new target language. Such functional specificity of the dorsal L. IFG provides neuroscientific evidence consistent with the claims made by the Cumulative-Enhancement model in investigating language acquisition beyond target second and third languages.
有人认为，约束第一语言习得的原则也约束第二语言习得；然而，这方面的神经科学证据很少，第三语言及后续语言的证据就更少了。我们通过关注哈萨克语复杂句子结构的构建来评估这一说法，哈萨克语是参与者习得的至少两种语言之外的一种新语言。参与者通过口语句子完成语法判断和主谓匹配任务。我们根据参与者在其中一项实验任务中的表现水平将他们分为两组：I 组高分组和 II 组低分组。对那些能够分析结构的参与者进行两组间的直接比较，结果表明，I 组在左背外侧额下回（L.IFG）的激活更强。针对 I 组，我们测试了初始和最终阶段的对比，以检查结构何时被分析，以及检查分析的结构。这些分析进一步证明了背外侧 L.IFG 的焦点激活。在个体参与者中，在句子呈现期间测量到的背外侧 L.IFG 的更强激活，预测了后续任务执行的更高准确率和更短的反应时间。这些结果不能用任务难度或记忆负荷来解释，相反，它们表明在新目标语言的语法习得的初始到中间阶段，背外侧 L.IFG 发挥了关键而一致的作用。背外侧 L.IFG 的这种功能特异性为累积增强模型在研究目标第二语言和第三语言之外的语言习得提供了一致的神经科学证据。
