Bilingualism as a Source of Experience-Dependent Plasticity: Mechanisms and Limits

这项研究将双语能力作为一种手段来研究与经验相关的神经可塑性在一生中影响认知表现的可能性。在执行功能(EF)任务上，双语者通常比单语者表现得更好，这些任务需要避免分心，目标之间的转换，以及参与工作记忆，并在大脑结构和功能上表现出差异。此外，在其他条件相同的情况下，双语者比单一语言者在疾病后期表现出痴呆症的症状。然而，并不是所有的研究都发现，这些影响有这么多是未知的。拟议的研究将使用行为和神经成像方法来检查儿童、年轻人和老年人，以解决这篇文献中的两个关键空白。第一个差距是确定造成所报告影响的机制。早期的解释是基于EF的成分观点，并挑出最相关的抑制。该理论认为，双语使用需要抑制，以避免来自共同激活的非目的语的干扰，但新的证据与这一观点不一致。我的假设是，双语经历会导致注意网络在复杂的语言环境中导航后的适应。注意力涉及EF的所有方面，但不局限于单个组件。关键的是，成分观点和注意力观点对双语表现的不同预测将会不同。从EF的成分来看，双语者在依赖抑制的任务上的表现优于单语者；从注意力的角度来看，双语者在复杂条件下需要有效的注意策略的任务上表现优于单语者，而与EF的成分无关。这些研究将处理不同范式的任务难度，以比较成分加工要求和注意要求对单语和双语受试者的影响。第二个差距是确定这些适应发生所需的条件。个体差异和背景显然与这些进程相互作用，以决定结果。零碎的证据表明，注意系统需要保持完整，双语才能带来积极的结果；患有ADHD的双语成年人没有显示出对非ADHD双语者的好处，有EF缺陷的双语老年人没有表现出任何痴呆症状的延迟。假设是，对于注意力系统受损的人来说，双语将加剧而不是有利于已经在苦苦挣扎的系统。了解双语如何导致认知中的神经可塑性变化，为设计干预措施广泛改善认知创造了可能性，刺激儿童的基本发展，并缓解老年人处于正常衰老和痴呆症之间的认知衰退。将注意力确定为经验和认知之间的相关桥梁，将对干预的新方向产生明确的影响。

This research examines bilingualism as a means of investigating the potential for experience-related neuroplasticity to affect cognitive performance across the lifespan. Bilinguals generally outperform monolinguals on executive function (EF) tasks that require avoiding distraction, shifting between goals, and engaging working memory and show differences in brain structure and function. Moreover, bilinguals display symptoms of dementia at a later stage of disease than monolinguals, all else being equal. However, not all studies find these effects so much remains unknown. The proposed studies will use behavioral and neuroimaging methods to examine children, young adults and older adults to address two crucial gaps in this literature. The first gap is identification of the mechanism responsible for the reported effects. The early explanation was based on a componential view of EF and singled out inhibition as most relevant. The idea was that bilingual language use required inhibition to avoid interference from the jointly activated non-target language but new evidence is inconsistent with this view. My hypothesis is that bilingual experience leads to an adaptation in attention networks that follow from navigating a complex linguistic environment. Attention is involved in all aspects of EF but not tied to a single component. Critically, the component and attention views make different predictions about bilingual performance will diverge. From a componential view of EF, bilinguals will outperform monolinguals on tasks that rely on inhibition; from an attention view, bilinguals will outperform monolinguals on tasks that require efficient attention strategies on complex conditions, regardless of the EF component. These studies will manipulate task difficulty across paradigms to compare the effect of component process demands and attention demands for monolingual and bilingual participants. The second gap is identification of the conditions necessary for these adaptations to occur. Individual differences and context clearly interact with these processes to determine outcomes. Fragmentary evidence points to the need for attention systems to be intact for bilingualism to lead to positive outcomes; bilingual adults with ADHD do not show the benefits found for non-ADHD bilinguals, and bilingual older adults with EF deficits do not show any delay of dementia symptoms. The hypothesis is that for individuals with compromised attention systems, bilingualism will exacerbate rather than benefit an already struggling system. Understanding how bilingualism leads to neuroplastic changes in cognition creates the possibility for devising interventions to improve cognition broadly, stimulating essential development in children and mitigating cognitive decline as older adults sit on the threshold between normal aging and dementia. Identifying attention as a relevant bridge between experience and cognition will have clear implications for new directions in intervention.