Effect of monolingualism and bilingualism in the anterior cingulate cortex: a proton magnetic resonance spectroscopy study in two centers

Abstract

Reports of an advantage of bilingualism on brain structure in young adult participants are inconsistent. Abutalebi et al. (2012) reported more efficient monitoring of conflict during the Flanker task in young bilinguals compared to young monolingual speakers. The present study compared young adult (mean age = 24) Cantonese-English bilinguals in Hong Kong and young adult monolingual speakers. We expected (a) differences in metabolites in neural tissue to result from bilingual experience, as measured by 1H-MRS at 3T, (b) correlations between metabolic levels and Flanker conflict and interference effects (c) different associations in bilingual and monolingual speakers. We found evidence of metabolic differences in the ACC due to bilingualism, specifically in metabolites Cho, Cr, Glx and NAA. However, we found no significant correlations between metabolic levels and conflict and interference effects and no significant evidence of differential relationships between bilingual and monolingual speakers. Furthermore, we found no evidence of significant differences in the mean size of conflict and interference effects between groups i.e. no bilingual advantage. Lower levels of Cho, Cr, Glx and NAA in bilingual adults compared to monolingual adults suggest that the brains of bilinguals develop greater adaptive control during conflict monitoring because of their extensive bilingual experience.***Efeito do monolinguismo e do bilinguismo no córtex anterior cingulado: um estudo de espectroscopia de ressonância magnética de prótons em dois centros***Relatos de uma vantagem do bilinguismo na estrutura cerebral em jovens participantes adultos são inconsistentes. Abutalebi et al. (2012) relataram uma monitorização mais eficiente do conflito durante a tarefa de Flanker em jovens bilíngues comparados com jovens monolíngues. O presente trabalho comparou jovem adultos (idade média = 24) bilíngues em Cantonês-Inglês de Hong Kong e jovens monolíngues adultos. Estávamos a contar com (a) diferenças em metabólitos no tecido neural como resultado de uma experiência bilíngue, medido pelo 3T 1H-MRS, (b) correlações entre os níveis metabólicos, conflito Flanker e efeitos de interferência (c) diferentes associações em falantes monolíngues e bilíngues. Encontramos evidências de diferenças metabólicas no ACC devido ao bilinguismo, especificamente nos metabólitos Cho, Cr, Gly e NAA. Porém, não constatamos correlações significativas entre os níveis metabólicos e efeitos de conflito e interferência e nenhuma evidência significativa de relações diferenciais entre falantes monolíngues e bilíngues. Além disso, não encontramos nenhuma evidência de diferenças significativas no tamanho médio dos efeitos do conflito e interferência entre os grupos, ou seja, nenhuma vantagem bilíngue. Níveis inferiores de Cho, Cr, Gly em adultos bilíngues em comparação com adultos monolíngues sugerem que o cérebro dos bilíngues desenvolve maior controle adaptativo durante a monitorização do conflito por causa da sua extensa experiência bilíngue.

Long-term cognitively challenging experiences modulate metabolite concentrations in the healthy brain: the case of bilingualism

“…The present study expands on Weekes et al 45 by looking at the effects of bilingualism on metabolite concentrations in the ventral striatum, a subcortical grey matter nucleus comprising the caudate nucleus and the putamen, key structures for language selection and cognitive control 28 , that have both been shown to be affected structurally by bilingualism 41,43 . In order to study such effects across the adult lifespan, the present study comprises a relatively large sample that spans an age range representative of the adult lifespan, additionally accounting for the known effects of age on metabolite concentrations 19 .…”

“…Resonance User Interface (jMRUI) software (version 5.2) 52 . Following literature in the field 20,45 we focused on the concentrations of NAA, CHO, CRE, INS and GLX. In the preprocessing phase, the water spectrum acquired closest to the measurement was used to perform phase correction.…”

“…Residual water peaks were removed with the Hankel-Lanczos Singular Value Decomposition (HLSVD) filter tool 54 . In the quantification phase, the same metabolite models as in 8 were employed for NAA, CRE, INS and GLX; exceptionally, and following from recent literature 20,45 , CHO was modelled as a single peak derived from the sum of choline, phosphocholine and glycerophosphocholine peaks.…”

“…To the best of our knowledge, only one study has looked at correlates in metabolic concentrations of the effects of bilingualism on cognition and the brain. Weekes and colleagues 45 compared young bilingual adults and age-and education-matched monolingual controls on metabolite concentrations (NAA, CHO, CRE, INS and GLX) in the anterior cingulate cortex (ACC), a region critical for domain general cognitive control 28 . Contrary to their predictions, Weekes and colleagues reported lower levels of NAA, CHO, CRE and GLX in bilinguals than monolinguals 1 , and interpreted this finding as an indication of more efficient control monitoring of the bilingual brain as a result of prolonged bilingual experience.…”

“…following the most traditional practice in the field 45 , we split our participant groups into Bilinguals and Monolinguals according to experiences in using more than one language (for details, see Methods). For this comparison, we predicted overall higher concentrations of INS and CHO in bilinguals, compared to monolinguals, an effect that would signify glial expansion, which could contribute to the observed restructuring of the ventral striatum in bilinguals 23,24 .…”