Danylkiv Anastasiya, Krafnick Anthony J
Psychology Department, Dominican University, River Forest, IL, United States.
Front Hum Neurosci. 2020 Apr 23;14:146. doi: 10.3389/fnhum.2020.00146. eCollection 2020.
Bilingualism is of great interest to the neuroscience of language, and understanding the anatomical changes associated with second language learning help inform theories of bilingual advantage across the lifespan. While the literature on structural differences between bilinguals and monolinguals is robust, relatively few studies of gray matter (GM) have directly compared bilinguals with monolinguals in a whole-brain analysis. Overall, this and heterogeneity of study samples and methodology have led to a lack of clear anatomical support for major theories. Here, we engage in an activation likelihood estimate (ALE) meta-analysis of voxel-based morphometry (VBM) studies of GM for cases that directly compare bilingual and monolingual subjects in a whole-brain analysis. The analysis (sixteen foci, from ten contrasts across eight studies) resulted in one cluster located primarily within the anterior lobe of the right cerebellum. However, when the one pediatric study was removed, the analysis revealed no consistent results across the studies included in this meta-analysis. This suggests that for VBM studies of bilingual and monolingual adults there is considerable heterogeneity of results that complicate the understanding of the bilingual brain. Future studies will need to include larger, more well-defined samples and interrogate more fine-grained anatomical features such as cortical thickness and surface area in order to more fully examine the anatomical changes associated with bilingualism across the lifespan.
双语现象在语言神经科学领域备受关注，了解与第二语言学习相关的解剖学变化有助于完善关于双语在整个生命周期中的优势的理论。虽然关于双语者和单语者结构差异的文献很丰富，但在全脑分析中，直接比较双语者和单语者灰质（GM）的研究相对较少。总体而言，研究样本和方法的异质性导致主要理论缺乏明确的解剖学支持。在此，我们对基于体素的形态学测量（VBM）研究进行激活可能性估计（ALE）元分析，这些研究在全脑分析中直接比较了双语和单语受试者的GM。分析结果（来自八项研究的十个对比中的十六个焦点）产生了一个主要位于右小脑前叶的簇。然而，当剔除一项儿科研究时，分析显示本次元分析纳入的研究之间没有一致的结果。这表明，对于双语和单语成年人的VBM研究，结果存在相当大的异质性，这使得对双语大脑的理解变得复杂。未来的研究需要纳入更大、定义更明确的样本，并研究更精细的解剖学特征，如皮质厚度和表面积，以便更全面地研究与双语在整个生命周期中相关的解剖学变化。
