Table 2.
Overview of studies investigating white matter changes related to global second language proficiency.
| Author | Sample | Learning environment | Analyses | Method | Main results |
|---|---|---|---|---|---|
| Coggins et al. (2004) | 12 Bilinguals (seven early bilinguals; five late bilinguals); seven monolinguals | Classroom setting | Compare CC morphology (regional to total area ratio) between groups | Analyses of size (regional to total area ratio) of five CC subregions as defined on the midsagittal plane of an MRI image | AMB ratio to total CC: larger in bilinguals than in monolinguals |
| Mohades et al. (2012) | Children (8–11 years): 15 simultaneous bilinguals; 15 sequential bilinguals; 15 monolinguals | Simultaneous bilinguals: naturalistic Sequential bilinguals: classroom-setting | Group comparison of four preselected white matter tracts (AF/SLF, IFOF, AC-OL, AMB) | DTI | Left IFOF: FA in simultaneous bilinguals > sequential bilinguals > monolinguals AC-OL: FA in simultaneous bilinguals < sequential bilinguals < monolinguals |
| Schlegel et al. (2012) | 11 English speaking students learning Chinese; 16 monolingual controls | Classroom setting | Longitudinal study comparing DTI changes in second language learners to those of mono-linguals | DTI (FA and RD) | Progressive FA increase in second language learners > controls FA increase in tracts connecting bilateral IFG, FMG, FPG, CN, left STG, PP, right PT FA increase related to second language proficiency |
| García-Pentón et al. (2014) | 13 Spanish monolinguals; 13 Spanish-Basque bilinguals | Naturalistic | Group comparison of connectivity differences (whole brain approach) | DTI-based connectivity analysis, network based statistics, graph analysis | Two networks show higher connectivity and more graph-efficient information flow: (a) left-sided network comprising SMG, STG, IFG, MSFG, INS. (b) network comprising right SFG, left SPG, ANG, STP, SOG |
CC, corpus callosum; IFOF, inferior occipitofrontal fasciculus; AF, arcuate fasciculus; SLF, superior longitudinal fasciculus; AC-OL, connection anterior corpus callosum and orbital lobes; AMB, anterior-midbody of corpus callosum; UNF, uncinated fasciculus; FMG, frontomarginal gyrus; FPG, frontopolar gyrus; CN, caudate nucleus; PP, planum polare; PT, planum temporale; SMG, supramarginal gyrus; STG, superior temporal gyrus; IFG, inferior frontal gyrus; (M)SFG, (medial) superior frontal gyrus; INS, insula; SPG, superior parietal gyrus; ANG, angular gyrus; STP, superior temporal gyrus; SOG, superior occipital gyrus; DTI, diffusion tensor imaging; FA, fractional anisotropy; RD, radial diffusivity.