The effects of bilingualism on the white matter structure of the brain

Abstract

Recent studies suggest that learning and using a second language (L2) can affect brain structure, including the structure of white matter (WM) tracts. 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. 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. Our Tract-Based Spatial Statistics analysis revealed higher fractional anisotropy values for bilinguals vs. 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. 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.bilingualism | immersion | white matter | second language acquisition | TBSS

The neuroanatomy of bilingualism: how to turn a hazy view into the full picture

“…The higher mean FA value for the IFOF in these bilingual children (Mohades et al, 2012) is the opposite pattern found for young adult bilinguals in Cummine & Boliek (2013), but the same pattern as Pliatsikas et al (2015) and also for older adult bilinguals (Luk et al, 2011). At the same time, the lower mean FA value in the CC obtained for these bilingual children is opposite to the pattern obtained for older adult bilinguals in the Luk et al (2011) and Pliatsikas et al (2015) studies but in line with the pattern obtained for older bilinguals in the Gold et al (2013) study. Olsen et al (2015) also extracted the volume of the WM for the frontal, temporal, parietal and occipital lobes in both hemispheres of their sample (described above, see section 2.1.1.2).…”

“…Furthermore, others studies support these results showing that this region is also sensitive to L2 AoA and proficiency (Grogan et al, 2012;Hosoda et al, 2013;Klein et al, 2014). Additionally, several WM structural studies also confirmed differences between bilinguals and monolinguals in the tracts connecting IFG with many other regions in the frontal lobe (including the contralateral side) and the temporal, parietal and occipital regions in the back of the brain, specifically the CC (Luk et al, 2011;Pliatsikas et al, 2015;Gold et al, 2013;Mohades et al, 2012) and the IFOF (Luk et al, 2011;Pliatsikas et al, 2015;Mohades et al, 2012;Gold et al, 2013;Cummine & Boliek, 2013). Nevertheless, although these results identified the same regions, they are contradictory because some show increases while others show decreases in the WM.…”

“…The most consistent WM changes were observed in CC and IFOF. However, while two studies found increased FA values in CC for bilinguals (Luk et al, 2011;Pliatsikas et al, 2015), another found decreased FA values (Gold et al, 2013). And some studies found increased FA values in IFOF for bilinguals (Luk et al, 2011;Pliatsikas et al, 2015), others found decreased FA values (Cummine & Boliek, 2013;Gold et al, 2013).…”

“…However, while some studies found increased FA values in the CC for older and younger adult bilinguals (Luk et al, 2011;Pliatsikas et al, 2015) others found decreased FA values for older adult bilinguals (Gold et al, 2013) and children (Mohades et al, 2012). And while some studies found increased FA in the IFOF for older adult bilinguals (Luk et al, 2011), younger adults (Pliatsikas et al, 2015) and children (Mohades et al, 2012), others found decreased FA values for older (Gold et al, 2013) and younger (Cummine & Boliek, 2013) adult bilinguals. Since almost all of the WM studies use the same methodological approach (i.e.…”

Sequential language learning versus language immersion in bilingualism: Diffusion MRI connectometry reveals microstructural evidence

“…Increased FA in the inferior fronto 58 occipital fasciculus (IFOF), and decreased FA in genu and anterior corpus callosum (CC), are 59 amongst reported changes in early L2 learners among school aged children (5). Pliatsikasa and his 60 colleagues provided insights into white matter structural differences in young bilingual adults, who 61 were are sequential learners of English as second language and were highly immersed, meaning 62 that they had been using L2 on a daily basis for a long period (6 (1). Grey matter volume in these areas positively correlated with lexial efficiency and negatively 71 correlated with the age at which bilinguals had started learning a new language (7).…”