![]() ![]() Mohades and colleagues attributed this difference to left hemispheric dominance in their monolingual and sequential bilingual groups compared with the bilateral language patterns that have been reported for early bilinguals ( 14).įurther evidence of the effect of simultaneous language learning on the WM of early bilinguals was recently provided by García-Pentón and colleagues ( 15), who compared a group of 13 Spanish-Basque bilinguals and a group of 13 age-matched Spanish monolinguals. In addition, the simultaneous group demonstrated decreased FA values compared with monolinguals only, in the anterior third of the CC, an area implicated in the lateralization of brain function ( 13). In this bundle, simultaneous bilinguals demonstrated higher FA values than the other two groups, signifying, according to the authors, more effective semantic processing for this group. Mohades and colleagues examined four specific bundles of fibers that have been associated with language processing and reported significant effects in two of them, including in the left IFOF, which has been suggested to play a role in semantic processing ( 12). The effects of early and simultaneous language learning on WM structure were demonstrated by Mohades and colleagues ( 11), who compared FA values in three groups of children: 15 simultaneous bilinguals, 15 sequential bilinguals (L2 learned at the age of 3 y), and 10 monolinguals. ![]() Gold and colleagues noted that this difference may be a result of the higher prevalence of Alzheimer’s disease among their bilinguals, however, and despite the observed reduction in WM integrity, the authors point out that their bilinguals were comparable or even more efficient than the monolinguals in a series of executive tasks, as reported in a separate study ( 8), which is in accordance with previous findings on bilinguals with Alzheimer’s disease ( 2). The structural findings by Luk and colleagues were challenged by Gold and colleagues ( 7), who tested 20 older lifelong bilinguals and 63 age-matched monolinguals and who reported lower FA values for bilinguals in several tracts, including the left IFOF, the fornix, and the CC. However, the groups in Luk and colleagues had comparable cognitive performance in a series of standardized neuropsychological tasks, so no evidence for a cognitive advantage for bilinguals was provided. Because high FA values have been related to greater WM integrity ( 6), Luk and colleagues suggested that lifelong bilingual experience preserves the WM integrity in older adults. The researchers analyzed their data by using Tract-Based Spatial Statistics (TBSS) ( 6) and reported higher fractional anisotropy (FA) values for bilinguals in the corpus callosum (CC), extending both posteriorly in the bilateral superior longitudinal fasciculi and anteriorly in the right inferior frontooccipital fasciculus (IFOF) and uncinate fasciculus. Luk and colleagues performed a diffusion tensor imaging (DTI) scan on 14 healthy older lifelong bilinguals and compared them with scans from 14 healthy age-matched monolingual participants. This would explain the cognitive benefits of bilingualism as a result of better connectivity between brain areas. ![]() The observed advantages for executive functioning performance in older bilinguals led Luk and colleagues ( 5) to investigate whether these advantages are related to significant effects in the WM structure of older bilinguals. We propose that learning and actively using an L2 after childhood can have rapid dynamic effects on WM structure, which in turn may assist in preserving WM integrity in older age. monolinguals in several WM tracts that have been linked to language processing and in a pattern closely resembling the results reported for older and early bilinguals. Our Tract-Based Spatial Statistics analysis revealed higher fractional anisotropy values for bilinguals vs. This study investigated whether young, highly immersed late bilinguals would also show structural effects in the WM that can be attributed to everyday L2 use, irrespective of critical periods or the length of L2 learning. This observation comes from research looking at early and older bilingual individuals who have been using both their first and second languages on an everyday basis for many years. Recent studies suggest that learning and using a second language (L2) can affect brain structure, including the structure of white matter (WM) tracts. ![]()
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