Programa general, fitxa d'activitat

Dimecres 7 de setembre de 2016 12:30 a 13:00 Presentació oral
Age of acquisition of the second language modulates structural and functional dynamics of bilingual reading
Exposa: Myriam Oliver, Basque Center on Cognition, Brain and Language

Autors: Myriam Oliver, Manuel Carreiras, Yasser Iturria-Medina & Pedro M.Paz-Alonso


Neuroimaging evidence has suggested the involvement of left-lateralized perisylvian regions in reading processes (Turkeltaub et al., 2002). In contrast, research on bilingualism has showed contradictory evidence in regard to the differential involvement of language-related brain regions and networks for reading in the native (L1) and second language (L2) (Hernandez et al., 2015). This highlights the relevance of investigating in a systematic manner the main factors modulating the differential involvement of reading regions and networks in bilinguals, while controlling other potential sources of variance. The age-of-acquisition(AoA) of the L2 and language proficiency have been pointed out as critical variables that can determine potential differences in brain function and structure among bilingual readers (Klein et al., 2014). Here, we sought to investigate the effects of the L2 AoA on the function and structure of language-related regions associated with L1 and L2 reading, while controlling language proficiency and exposition to L1 and L2. To this end, we followed a multimodal neuroimaging approach examining fMRI, cortical thickness and tractography measures in a sample of early and late bilinguals. Thirty-six bilinguals with Spanish as their L1, who learned Basque as their L2 before age 3 (early bilinguals) or after age 6 (late bilinguals), participated. All participants were high-proficient in both languages. In the scanner, they performed two separate tasks during which they were asked to press a button when they saw a colored letter within a given string (perceptual-task) or when they saw an animal word (semantic-task). Whole-brain fMRI analysis reveals no differences between groups. Region-of-interest analysis revealed a similar recruitment of left and right language-related regions in both early and late bilinguals except for the left and right pars triangularis. As compared to late bilinguals, early bilinguals exhibited a different pattern of left triangularis engagement in the interaction between task and language effects. Similarly, early bilinguals showed a more selective recruitment for word versus pseudoword reading in right triangularis. Moreover, functional connectivity analyses confirmed a tighter coactivation among left and right pars triangularis in early, but not in late, bilinguals for reading in L1 relative to reading in L2. Importantly, structural analysis revealed increased cortical thickness in right pars triangularis for early relative to late bilinguals. Additionally, enhanced functional activation for L2-L1 language effects in the left triangularis predicted cortical thinning in their right triangularis counterpart only in early bilinguals. Finally, diffusion MR tractography of the connecting left and right pars triangularis also revealed differences between early and late bilinguals. In sum, our results indicate that the early exposure to two languages led to a more distributed involvement of regions beyond the classical left perisylvian areas in reading. Our findings provide the strongest converging evidence so far of structural and functional changes involving left and right triangularis as a result of L2 AoA in bilingual readers.
Desenvolupament en contextos bilingües i plurilingües
Lloc: Aula A-15

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