Brain Plasticity and Language Learning

大量的研究表明，在生命的第一年接触语言的声音对语言的发展至关重要。我的实验室在探索早期语言经验对大脑组织和神经可塑性的影响方面发挥了重要作用，从而深入了解语言的普遍性以及它们在大脑中的表现方式。我们利用国际被收养者（IA）的独特情况来探索语言的神经关联，表明第一语言的模板在婴儿时期突然失去这种语言几十年后仍然存在于大脑中。目前尚不清楚的是，这些模板的目的是什么。在生命早期学习的声音模式是否会影响后来的语言学习（例如，在重新学习语言时）？神经模式是固定的还是灵活的，它们与学习中的个体差异有什么关系？在这个发现基金中，我们通过新的实验解决了这些知识差距，使用受控的前后训练方法，以及更自然的纵向训练，将大脑的变化与学习结果联系起来。最先进的行为和神经成像方法（MEG，功能磁共振成像任务，静息状态功能磁共振成像，结构脑成像）将用于评估从脑干到皮层的反应，从声学编码到高阶语言处理，在同一个体中，允许跨语言水平的语言处理及其相互依赖性的全面理解。我们将把出生在中国但现在只说法语的IA与具有不同语言配对（英语-法语，普通话-法语）的紧密匹配组以及同时与顺序语言学习者进行比较，以理清学习语言的数量，语言配对类型和学习年龄对大脑的影响。第一个实验关注的是不同群体在学习语音和韵律方面的语言体验差异，询问出生语言（普通话）的模板是否有助于在以后的生活中重新学习这门语言，以及大脑中哪些地方编码了这些信息，以及这些信息是否会随着训练而改变。实验的第二条线索关注的是早期感知语言经验对更全面的语言处理的普遍性，以及与语言学习结果相关的倾向。我们的分析不仅关注语言经验如何影响大脑，而且还关注识别语言学习成功的预训练预测因子或生物标志物。我们希望这些研究的结果能够揭示大脑如何对训练做出反应，从而推动加拿大语言教育政策和实践的进步。未来的工作还将把我们的重点扩展到语言消耗和重新学习的其他情况（例如，加拿大的传统语言）。总的来说，拟议的实验推进了我的研究计划，旨在阐明语音和语言习得的基本神经生物学机制。

A substantial body of work has shown that exposure to the sounds of language in the first year of life are critical for language development. My lab has been instrumental in exploring the effect of early linguistic experience on brain organization and neuroplasticity, to develop insights into universals of languages and how they are represented in the brain. We have capitalized on the unique situation of international adoptees (IA) to probe neural correlates of language, showing that the templates of the first language remain in the brain decades later, after abrupt loss of that language in infancy. What is not yet known, is what purpose these templates serve. Do sound patterns learnt early in life influence later language learning (e.g., when relearning that language)? Are neural patterns fixed or flexible, and how do they relate to individual differences in learning? In this Discovery Grant, we address these knowledge gaps with new experiments using controlled pre-post training approaches, and more naturalistic longitudinal training to link changes in the brain to learning outcomes. State-of-the-art behavioural and neuroimaging methods (MEG, fMRI tasks, resting-state fMRI, structural brain imaging) will be used to assess responses from brainstem to cortex, from acoustic encoding to higher-order language processing, in the same individuals, allowing for comprehensive understanding of language processing across linguistic levels and their interdependencies. We will compare IA, born in China but now speak exclusively French, to tightly matched groups with different language pairings (English-French, Mandarin-French) and simultaneous versus sequential language learners, to disentangle the impact of number of languages learned, types of language pairings, and age of learning on the brain. The first experiments focus on language experiential differences between groups in relation to learning phonetics and prosody, asking whether templates of a birth language, Mandarin, aid relearning of the language later in life, as well as where in the brain this information is encoded and if this changes with training. The second thread of experiments focus on how generalisable early perceptual language experience is to more global language processing, and predispositions related to language learning outcomes. Our analyses focus not only on how language experience impacts the brain, but also on identifying pre-training predictors or biomarkers of language learning success. We expect the results from these studies to shed light on how the brain changes in response to training, leading to advances in language-education policies and practices in Canada. Future work will also extend our focus to other situations of language attrition and re-learning (e.g., heritage languages of Canada). Overall, the proposed experiments advance my research program that aims to elucidate fundamental neurobiological mechanisms underlying speech and language acquisition.