General principles governing the amount of neuroanatomical overlap between languages in bilinguals

Połczyńska, Monika; Bookheimer, Susan Y.

doi:10.1016/j.neubiorev.2021.08.005

Cited by 15 publications

(9 citation statements)

References 125 publications

(224 reference statements)

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“…It is increasingly recognized that neuroanatomic differences are shaped by factors such as proficiency, age of L2 acquisition (i.e., learned early and simultaneously with L1 vs much later than L1), amount of language exposure, frequency of language switching, and typological similarity between languages. 48 Two recent graph theory studies with healthy adults found that several of these bilingual language factors modulated whole-brain and regional network organization. 13,14 In addition, bilingualism's effects on the brain likely follow a dynamic nonlinear pattern.…”

Section: Discussionmentioning

confidence: 99%

Bilingualism and Structural Network Organization in Temporal Lobe Epilepsy

et al. 2023

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Background and Objectives:There is growing evidence that bilingualism can induce neuroplasticity and modulate neural efficiency, resulting in greater resistance to neurological disease. However, whether bilingualism is beneficial to neural health in the presence of epilepsy is unknown. We tested whether bilingual individuals with temporal lobe epilepsy (TLE) have improved whole-brain structural white matter network organization.Methods:Healthy controls and individuals with TLE recruited from two specialized epilepsy centers completed diffusion-weighted MRI and neuropsychological testing as part of an observational cohort study. Whole-brain connectomes were generated via diffusion tractography and analyzed using graph theory. Global analyses compared network integration (path length) and specialization (transitivity) in TLE versus controls and in a 2 (left vs right TLE) x 2 (bilingual vs monolingual) model. Local analyses compared mean local efficiency of predefined frontal-executive and language (i.e., perisylvian) subnetworks. Exploratory correlations examined associations between network organization and neuropsychological performance.Results:A total of 29 bilingual and 88 monolingual individuals with TLE matched on several demographic and clinical variables, as well as 81 age-matched healthy controls were included. Globally, a significant interaction between language status and side of seizure onset revealed higher network organization in bilinguals compared to monolinguals, but only in left TLE (LTLE). Locally, bilinguals with LTLE showed higher efficiency in frontal-executive, but not in perisylvian networks compared to LTLE monolinguals. Improved whole-brain network organization was associated with better executive function performance in bilingual but not monolingual LTLE.Discussion:Higher structural network organization in bilingual individuals with LTLE suggests a neuromodulatory effect of bilingualism on whole-brain connectivity in epilepsy, providing evidence for neural reserve. This may reflect attenuation of or compensation for epilepsy-related dysfunction of the left hemisphere, potentially driven by increased efficiency of frontal-executive networks that mediate dual-language control. This highlights a potential role of bilingualism as a protective factor in epilepsy, motivating further research across neurological disorders to define mechanisms and develop interventions.

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Section: Discussionmentioning

confidence: 99%

Bilingualism and Structural Network Organization in Temporal Lobe Epilepsy

et al. 2023

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“…Given this, what is the explanation for why early bilingual children have less GMV in the left supramarginal (extending into superior temporal) and angular gyri? fMRI studies have shown that early bilinguals tend to show activity in the same perisylvian cortical regions for their two languages, whereas late bilinguals show less of this kind of overlap between their two languages (Połczyńska & Bookheimer, 2021). It is likely that the language cortex that houses two languages, as in bilinguals, is different in volume than that which houses only one language, as in monolinguals, but the prediction would be for GMV to be greater if subserving two languages, which does not fit with our results.…”

Section: Discussionmentioning

confidence: 99%

Gray matter volume differences between early bilinguals and monolinguals: A study of children and adults

Schug

Brignoni-Pérez

Jamal

et al. 2022

Human Brain Mapping

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Gray matter has been shown to be greater in early bilingual adults relative to monolingual adults in regions associated with language (Mechelli et al., 2004), and executive control (EC; Olulade et al., 2016). It is not known, however, if language experience‐dependent differences in gray matter volume (GMV) exist in children. Further, any such differences are likely not to be the same as those observed in early bilingual adults, as children have had relatively shorter duration of dual‐language exposure and/or less development of brain regions serving EC. We tested these predictions by comparing GMV in Spanish–English early bilingual and English monolingual children, and Spanish–English early bilingual and English monolingual adults (n = 122). Comparing only children revealed relatively more GMV in the bilinguals in bilateral frontal, right inferior frontal, and right superior parietal cortices (regions associated with EC). Bilinguals, however, had less GMV in left inferior parietal cortex (region associated with language). An ANOVA including these children with bilingual and monolingual adults revealed interactions of Language Background by Age Group. There were no regions of more GMV in bilinguals relative to monolinguals that were less pronounced in children than adults, despite the children's shorter dual‐language experience. There were relative differences between bilingual and monolingual children that were more pronounced than those in adults in left precentral gyrus and right superior parietal lobule (close to, but not directly in areas associated with EC). Together, early bilingual children manifest relative differences in GMV, and, surprisingly, these do not diverge much from those observed in studies of bilingual adults.

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“…These studies will benefit from large samples of participants matched on reading ability and the use of stringent statistical thresholds. Lastly, studies could be done with the inclusion of both early and late bilinguals as a way to assess the more profound impact of experience‐dependent plasticity typically reported in late bilinguals (Połczyńska & Bookheimer, 2021 ).…”

Section: Discussionmentioning

confidence: 99%

“…There has been some suggestion that phonological processing, a foundational skill required for learning to read (Wagner & Torgesen, 1987 ), is better in bilinguals (Eviatar & Ibrahim, 2000 ; Kovelman et al, 2008b ; Kuo & Anderson, 2012 ), although not all studies support this observation (Martin, 2011 ). Brain imaging studies comparing both early and late bilinguals have shown that both languages are mapped to the same brain regions in bilinguals with early age of acquisition and high proficiency, but to divergent brain regions in those with late second language acquisition and lower proficiency (for review, see Połczyńska & Bookheimer, 2021 ). One might expect that the processing of two languages in the same brain region in early bilinguals would represent differently from that in monolinguals, where that same brain region is dedicated to only a single language.…”

Section: Introductionmentioning

confidence: 99%

“…Neuroimaging investigations have shown that brain structure, activity, and functional connectivity in brain areas associated with executive function differ between bilinguals and monolinguals (Hayakawa & Marian, 2019;Kroll & Bialystok, 2013;Mechelli et al, 2004;Olulade et al, 2016;Wong et al, 2016). However, findings on heightened language and nonlanguage skills in bilinguals (Kroll et al, 2012(Kroll et al, , 2014Kroll & Bialystok, 2013) have been challenged (see Dick, 2018;Lehtonen et al, 2018;Nichols et al, 2020;Paap et al, 2015) and the complexities of these studies have been discussed (DeLuca et al, 2020;Połczy nska & Bookheimer, 2021). This evidence from studies on language and on executive function in bilinguals raises the question whether an early bilingual experience influences the brain bases of reading.…”

Section: Introductionmentioning

confidence: 99%

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Functional neuroanatomy of English word reading in early bilingual and monolingual adults

Brignoni-Pérez

Jamal

Eden

2022

Human Brain Mapping

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Skilled reading is important in daily life. While the understanding of the neurofunctional organization of this uniquely human skill has advanced significantly, it does not take into consideration the common bilingual experiences around the world. To examine the role of early bilingualism on the neural substrates supporting English word processing, we compared brain activity, as well as functional connectivity, in Spanish‐English early bilingual adults ( N = 25) and English monolingual adults ( N = 33) during single‐word processing. Activation analysis revealed no significant differences between the two groups. A seed‐to‐voxel analysis using eight a priori selected seed‐regions (placed in regions known to be involved in reading) revealed relatively stronger functional connectivity in bilinguals between two sets of regions: left superior temporal gyrus seed positively with left lingual gyrus and left middle frontal gyrus seed negatively with left anterior cingulate cortex. Together these results suggest that an early Spanish‐English bilingual experience does not modulate local brain activity for English word reading. It does, however, have some influence on the functional intercommunication between brain regions during reading, specifically in two regions associated with reading, which are functionally connected to those inside and outside of the reading network. We conclude that brain regions involved in processing English words are not that different in Spanish‐English early bilingual adults relative to monolingual adult users of English.

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General principles governing the amount of neuroanatomical overlap between languages in bilinguals

Cited by 15 publications

References 125 publications

Bilingualism and Structural Network Organization in Temporal Lobe Epilepsy

Bilingualism and Structural Network Organization in Temporal Lobe Epilepsy

Gray matter volume differences between early bilinguals and monolinguals: A study of children and adults

Functional neuroanatomy of English word reading in early bilingual and monolingual adults

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