Immersive bilingualism reshapes the core of the brain

Bilingualism has been shown to affect the structure of the brain, including cortical regions related to language. Less is known about subcortical structures, such as the basal ganglia, which underlie speech monitoring and language selection, processes that are crucial for bilinguals, as well as other linguistic functions, such as grammatical and phonological acquisition and processing. Simultaneous bilinguals have demonstrated significant reshaping of the basal ganglia and the thalamus compared to monolinguals. However, it is not clear whether these effects are due to learning of the second language (L2) at a very young age or simply due to continuous usage of two languages. Here, we show that bilingualism-induced subcortical effects are directly related to the amount of continuous L2 usage, or L2 immersion. We found significant subcortical reshaping in non-simultaneous (or sequential) bilinguals with extensive immersion in a bilingual environment, closely mirroring the recent findings in simultaneous bilinguals. Importantly, some of these effects were positively correlated to the amount of L2 immersion. Conversely, sequential bilinguals with comparable proficiency and age of acquisition (AoA) but limited immersion did not show similar effects. Our results provide structural evidence to suggestions that L2 acquisition continuously occurs in an immersive environment, and is expressed as dynamic reshaping of the core of the brain. These findings propose that second language learning in the brain is a dynamic procedure which depends on active and continuous L2 usage

Creating Appropriate Clinical Guidelines for The Bilingual Population with Acquired Brain Injuries

While there is a growing bilingual demographic in the United States, relatively little is known about treating this population should they experience a brain injury. This is a growing area of interest, as research has demonstrated that the acquisition of a second language promotes neuroplastic changes that then impact brain functioning pre- and post-brain-injury. Given bilingualism’s cognitive complexity, clinicians are left with challenges on how best to tailor treatment for brain-injured bilingual populations. Therefore, the focus of this review was to provide clinical recommendations to clinicians performing assessments with bilingual individuals with acquired brain injuries. The goal was for the guidelines provided to aid in the augmentation of appropriate strategies for neurorehabilitation to maximize linguistic, cognitive, and communicative improvement, leading to social readaptation and a better quality of life

The Effects of Multilingualism on Brain Structure, Language Control and Language Processing

This chapter reviews a small but growing body of research that examines neuroplasticity stemming from multilingualism, specifically discussing some similarities and differences in brain structure and function stemming from in processing three or more languages, as a departure from bilingualism. The evidence comes from studies using magnetic resonance imaging to examine patterns of grey matter structure across cortical and subcortical regions, and aspects of white matter microstructure. This chapter also highlights the functional activation and temporal information of various processes that occur during language processing in multilinguals, while accounting for the influence of language background factors. It then discusses conflicting and agreeing evidence in the literature and attempts to consolidate the findings with suggestions based on contemporary frameworks such as the Dynamic Restructuring Model (Pliatsikas, 2020). In closing, the chapter highlights gaps and pose questions for future research directions in the field of multilingualism and neuroplasticity

Understanding structural plasticity in the bilingual brain: The Dynamic Restructuring Model

Research on the effects of bi-/multilingualism on brain structure has so far yielded variable patterns. Although it cannot be disputed that learning and using additional languages restructures grey (cortical, subcortical and cerebellar) and white matter in the brain, both increases and reductions in regional volume and diffusivity have been reported. This paper revisits the available evidence from simultaneous and sequential bilinguals, multilinguals, interpreters, bimodal bilinguals, children, patients and healthy older adults from the perspective of experience-based neuroplasticity. The Dynamic Restructuring Model (DRM) is then presented, a three-stage model accounting for, and reinterpreting, all the available evidence by proposing a time-course for the reported structural adaptations, and by suggesting that these adaptations are dynamic and depend on the quantity and quality of the language learning and switching experience. This is followed by suggestions for future directions for the emerging field of bilingualism-induced neuroplasticit

The many shades of bilingualism: language experiences modulate adaptations in brain structure

Recent years have seen an expansion in the research related to structural brain adaptations related to the acquisition and processing of additional languages. However, the accumulating evidence remains to a great extent inconsistent, with a large variety of cortical, subcortical and cerebellar effects reported in various studies. Here we propose that the variability in the data can be explained by the differences in the language background and experiences of the tested samples. We also propose that the field should move away from monolithic bilingual vs. monolingual comparisons; instead, it should focus on the experiences of the bilingual groups as predictors of structural changes in the brain, and also employ longitudinal designs to test the dynamic effects of active bilingualism. The implications of the proposed approaches for the suggested benefits of bilingualism on ageing and patient populations are also discussed

Linguistic immersion and structural effects on the bilingual brain: a longitudinal study

Learning and using additional languages can result in structural changes in the brain. However, the time course of these changes, as well as the factors the predict them, are still not well understood. In this longitudinal study we test the effects of bilingual immersion on brain structure of adult sequential bilinguals not undergoing any language training, who were scanned twice, three years apart. We observed significant increases in grey matter volume in the lower left cerebellum, mean white matter diffusivity in the frontal cortex, and reshaping of the left caudate nucleus and amygdala and bilateral hippocampus. Moreover, both prior length of immersion and L2 age of acquisition were significant predictors of volumetric change in the cerebellum. Taken together, these results indicate that bilingualism-induced neurological changes continue to take place across the lifespan and are strongly related to the quantity and quality of bilingual immersion, even in highly-immersed adult bilingual populations

Redefining bilingualism as a spectrum of experiences that differentially affect brain structure and function

Learning and using an additional language is shown to have an impact on the structure and function of the brain, including in regions involved in cognitive control and the connections between them. However, the available evidence remains variable in terms of the localization, extent and trajectory of these effects. Variability likely stems from the fact that bilingualism has been routinely operationalized as a categorical variable (bilingual/monolingual), whereas it is a complex and dynamic experience with a number of potentially deterministic factors affecting neural plasticity. Here we present the first study investigating the combined effects of experience-based factors (EBFs) in bilingual language use on brain structure and functional connectivity. EBFs include an array of measures of everyday usage of a second language in different types of immersive settings (e.g., amount of use in social settings). Analyses reveal specific adaptations in the brain, both structural and functional, correlated to individual EBFs and their combined effects. Taken together the data show that the brain adapts to be maximally efficient in the processing and control of two languages, although modulated ultimately by individual language experience