It is controversial as to how age of acquisition (AoA) and proficiency level of the second language influence the similarities and differences between the first (L1) and the second (L2) language brain networks. In this functional MRI study, we used representational similarity analysis to quantify the degree of neural similarity between L1 and L2 during sentence comprehension tasks in 26 adult Chinese-English bilinguals, who learned English as L2 at different ages and had different proficiency levels. We found that although L1 and L2 processing activated similar brain regions, greater neural pattern dissimilarity between L1 and L2 was associated with earlier AoA in the left inferior and middle frontal gyri after the effect of proficiency level was controlled. On the other hand, the association between proficiency level and the neural pattern dissimilarity between L1 and L2 was not significant when the effect of AoA was partialled out. The results suggest that the activity pattern of L2 is more distinct from that of L1 in bilingual individuals who acquired L2 earlier and that the contribution of AoA to the neural pattern dissimilarity is greater than that of proficiency level.

中文翻译：

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较早的第二语言习得与第一语言和第二语言之间更大的神经模式差异相关

关于习得年龄 (AoA) 和第二语言的熟练程度如何影响第一 (L1) 和第二 (L2) 语言大脑网络之间的异同，存在争议。在这项功能性 MRI 研究中，我们使用表征相似性分析来量化 26 名成人汉英双语者在句子理解任务中 L1 和 L2 之间的神经相似程度，他们在不同年龄学习英语为 L2，具有不同的熟练程度。我们发现，虽然 L1 和 L2 处理激活了相似的大脑区域，但在控制熟练程度的影响后，L1 和 L2 之间更大的神经模式差异与左侧额下回和额中回的早期 AoA 相关。另一方面，当部分排除 AoA 的影响时，熟练程度与 L1 和 L2 之间的神经模式差异之间的关联不显着。结果表明，在较早获得 L2 的双语个体中，L2 的活动模式与 L1 的活动模式更不同，并且 AoA 对神经模式差异的贡献大于熟练程度。