Amsterdam Center for Language and Communication, Department of Dutch Studies, University of Amsterdam, Amsterdam, The Netherlands.
Alzheimer Center Amsterdam, Neurology, Amsterdam Neuroscience, Amsterdam UMC location VUmc, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
Sci Rep. 2023 Feb 28;13(1):3428. doi: 10.1038/s41598-023-30326-3.
Bilingualism has been linked to structural adaptations of subcortical brain regions that are important for controlling multiple languages. However, research on the location and extent of these adaptations has yielded variable patterns, especially as far as the subcortical regions are concerned. Existing literature on bilingualism-induced brain restructuring has so far largely overseen evidence from other domains showing that experience-based structural neuroplasticity often triggers non-linear adaptations which follow expansion-renormalisation trajectories. Here we use generalised additive mixed models to investigate the non-linear effects of quantified bilingual experiences on the basal ganglia and the thalamus in a sample of bilinguals with a wide range of bilingual experiences. Our results revealed that volumes of the bilateral caudate nucleus and nucleus accumbens were significantly related to bilingual experiences. Importantly, these followed a non-linear pattern, with increases followed by plateauing in the most experienced bilinguals, suggesting that experience-based volumetric increases are only necessary up to a certain level of bilingual experience. Moreover, the volumes of putamen and thalamus were positively predicted by bilingual experiences. The results offer the first direct evidence that bilingualism, similarly to other cognitively demanding skills, leads to dynamic subcortical structural adaptations which can be nonlinear, in line with expansion-renormalisation models of experience-dependent neuroplasticity.
双语能力与控制多种语言的皮质下脑区结构适应有关。然而，关于这些适应的位置和程度的研究产生了不同的模式，特别是就皮质下区域而言。目前关于双语导致大脑结构重组的文献在很大程度上忽略了来自其他领域的证据，这些证据表明，基于经验的结构神经可塑性经常引发遵循扩展-再归一化轨迹的非线性适应。在这里，我们使用广义加性混合模型，在一个双语经验范围广泛的双语者样本中，研究了量化双语经验对基底神经节和丘脑的非线性影响。我们的结果表明，双侧尾状核和伏隔核的体积与双语经验显著相关。重要的是，这些结果遵循非线性模式，在经验最丰富的双语者中，增加后达到稳定，这表明基于经验的体积增加只需要达到一定的双语经验水平。此外，壳核和丘脑的体积也被双语经验所正向预测。研究结果首次直接证明，双语能力与其他认知要求较高的技能一样，导致皮质下结构的动态适应，这种适应可能是非线性的，符合经验依赖型神经可塑性的扩展-再归一化模型。
