Early life stress and socioeconomic variation as determinants of language-related neurodevelopment

早期的语言经验塑造了支持日益复杂的语言能力发展的神经系统，使儿童能够适应他们独特的环境（例如，Werker & Hensch，2015）。然而，如何早期变化（例如，在输入的时间、质量和数量上）影响这些神经系统的发展，并且对长期语言结果的影响还没有很好地理解（Pierce等人，2017 a，B）。在早期语言环境中具有已知差异的群体之间进行系统比较（例如，双语，单语，国际收养;皮尔斯等人，2014; 2015）已被用于测试早期环境变化与通过神经发育变化的语言结果之间的途径（Pierce等人，2017 a，B）。然而，对于许多儿童来说，早期经历不同的系统方式尚未确定。例如，虽然社会经济地位（SES）预测儿童的语言能力（例如，霍夫，2003年），在社会经济多样化的背景下，变异的来源，神经发育途径导致不同的语言结果，没有得到很好的理解。来自母婴二人组的证据表明，在低SES背景下，母亲压力与婴儿期的语言行为和母婴互动有关（Pierce等人，2020年）。行为还与脑电图（EEG）模式相关联，所述模式a）作为压力的函数而变化（Pierce等人，2019），和B）预测语言结果（Benasich等人，2008年）。研究结果表明，如何在社会经济多样性的背景下，早期的变化可以用来测试早期输入和神经发育之间的相互作用，但仍有相当多的工作。我提出了一种新的多学科方法，使用发育神经科学工具和家庭语言记录，以：1）表征早期变异的来源（例如，压力）在社会经济上不同的背景下，2）映射早期变异到语言发展背后的特定神经过程，和3）测试这些神经过程是否介导早期变异和语言结果之间的关联。我还将探讨个体差异（例如，性别;压力的生理指标）作为神经发育变化的调节剂，以及5）探索语言发育如何与其他发育系统相互作用。在这里，我用我们对语言发展的深刻理解，沿着定义逆境的维度框架，作为阐明神经可塑性机制的工具（例如，早期变异如何产生持久的经验依赖性神经变化）。我明确预测了为什么特定的语言特征可能会受到早期输入变化的影响，以及随着时间的推移，这些特征如何影响语言结果。这将广泛地为我们理解早期变异性和语言结果之间的机械联系提供信息-特别是在严重缺乏社会经济变异性的领域-并将揭示大脑发育的基本特性。

Early language experience shapes neural systems that support the development of increasingly complex language abilities, allowing children to adapt to their unique environments (e.g., Werker & Hensch, 2015). Yet, how early variation (e.g., in timing, quality, and quantity of input) influences the development of these neural systems, and implications for long-term language outcomes, are not well understood (Pierce et al., 2017a,b). Systematic comparisons between groups with known differences in the early language environment (e.g., bilingual, monolingual, international adoptees; Pierce et al., 2014; 2015) have been used to test pathways between early environmental variation and language outcomes via neurodevelopmental change (Pierce et al., 2017a,b). However for many children, systematic ways that early experiences differ have not been identified. For example, while socioeconomic status (SES) predicts children's language abilities (e.g., Hoff, 2003), sources of variability within a socioeconomically diverse context, and neurodevelopmental pathways leading to disparate language outcomes, are not well understood. Evidence from mother-infant dyads suggests that maternal stress, within a low-SES context, is associated with language behaviours and caregiver-child interactions during infancy (Pierce et al., 2020). Behaviours have also been associated with electroencephalography (EEG) patterns that a) vary as a function of stress (Pierce et al., 2019), and b) predict language outcomes (Benasich et al., 2008). Results suggest how early variation in a socioeconomically diverse context could be used to test interactions between early input and neurodevelopment, yet considerable work remains. I propose a novel multidisciplinary approach, using developmental neuroscience tools and home language recordings, to: 1) characterize sources of early variation (e.g., stress) in socioeconomically diverse contexts, 2) map early variation to specific neural processes underlying language development, and 3) test whether these neural processes mediate associations between early variation and language outcomes. I will also 4) probe individual differences (e.g., sex; physiological metrics of stress) as moderators of neurodevelopmental change, and 5) explore how language development interacts with other developing systems. Here I use our strong understanding of language development, along with dimensional frameworks for defining adversity, as tools to illuminate mechanisms of neuroplasticity (e.g., how early variation exerts long-lasting experience-dependent neural change). I make clear predictions for why specific language features might be affected by early input variation, and how these impact language outcomes over time. This will broadly inform our understanding of mechanistic links between early variability and language outcomes - particularly in the critically lacking area of socioeconomic variability - and will reveal fundamental properties of brain development.