Notwithstanding rising interest, a coherent picture of the brain's representation of two languages has not yet been achieved. In the present meta-analysis we analysed a large number of functional neuroimaging studies focusing on language processing in bilinguals. We used activation likelihood estimation (ALE) to enucleate activation areas involved in bilingual processing and control of different types of linguistic knowledge - lexico-semantics, grammar, phonology - in L1 and L2. Results show that surprisingly, compared to L2, lexico-semantic processing in L1 involves a widespread system of cortico-subcortical regions, especially when L2 is acquired later in life. By contrast, L2 processing recruits regions exceeding the L1 semantic network and relating to executive control processes. Only few regions displayed selective activation for grammar and phonology. Analyses of language switching highlight a functional overlap between domain-general and bilingual language control networks. Collectively, our findings point to a shared neural network for L1 and L2 with few differences depending on the linguistic level. The emerging picture identifies under-investigated issues, offering clear directions for future research.

中文翻译：

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双语语言处理：功能神经影像学研究的荟萃分析。

尽管人们的兴趣日益浓厚，但仍无法获得大脑对两种语言的表示形式的连贯描述。在本次荟萃分析中，我们分析了许多功能性神经影像学研究，重点是双语者的语言处理。我们使用激活可能性估计（ALE）来阐明L1和L2中涉及双语处理和控制不同类型语言知识（词汇语义，语法，语音学）的双语激活区域。结果表明，令人惊讶的是，与L2相比，L1中的词汇语义处理涉及到皮层-皮层下区域的广泛系统，尤其是当L2是在晚年获得的时。相反，L2处理募集了超出L1语义网络并与执行控制过程有关的区域。只有极少数地区显示出对语法和语音的选择性激活。语言切换分析突出显示了领域通用语言和双语语言控制网络之间的功能重叠。总的来说，我们的发现指向L1和L2的共享神经网络，根据语言水平的不同几乎没有差异。新出现的图片指出了研究不足的问题，为未来的研究提供了明确的方向。