Investigating the contribution of ventral-lexical and dorsal-sublexical pathways during reading in bilinguals

Abstract

Several studies suggest the existence of ventral-lexical and dorsal-sublexical systems for reading. The relative contribution of these pathways can be manipulated by stimulus type and task demands. However, little is known about how bilinguals use these systems to read in their second language. In this study diffusion tensor imaging (DTI) was used to investigate the relationship between white matter (WM) integrity and reaction time in a group of 12 Chinese–English bilingual and 11 age-matched English monolingual adults. Considering a dual-route model of reading, the following four tracts were isolated in both the left and right hemispheres using a tractography measurement approach. Ventral tracts included the uncinate fasciculus (UF) and the inferior longitudinal fasciculus (ILF). The dorsal tracts of interest were the arcuate fasciculus (AF) and the superior longitudinal fasciculus (SLF). A significant correlation between the reaction time in a reading task and the mean diffusivity (MD) value was observed in the right UF in both bilingual and monolingual groups. Moreover, in the bilingual group we observed significantly more positive relationships between reaction time and MD in the right AF, and bilaterally in the SLF. We concluded that the relative contribution of the dorsal system for reading is greater in bilinguals than monolinguals. Further, these findings implicate a role of the right hemisphere in reading.

The effect of bilingualism on brain development from early childhood to young adulthood

“…2 and 3). The involvement of the dorsal stream would be consistent with evidence suggesting increased contributions from this stream during at least reading in bilinguals as compared to monolinguals (Parker Jones et al 2012;Bakhtiari et al 2014), findings that have been attributed to increased articulatory competition in bilinguals (Parker Jones et al 2012). A similar argument could also be made for increased competition among the different grammars in bilinguals, particularly given the dependence of grammar on pars opercularis and nearby premotor cortex (Friederici 2011).…”

The effect of bilingualism on brain development from early childhood to young adulthood

“…Indeed, the supramarginal gyrus, pars opercularis, and superior frontal cortex showed particularly reliable differences between developmental trajectories for bilinguals and monolinguals (Figures 2 and 3). The involvement of the dorsal stream would be consistent with evidence suggesting increased contributions from this stream during at least reading in bilinguals as compared to monolinguals (Bakhtiari, Boliek, Cummine, Ben-shachar, & Ilan, 2014;Parker Jones et al, 2012), findings that have been attributed to increased articulatory competition in bilinguals (Parker Jones et al, 2012). A similar argument could also be made for increased competition among the different grammars in bilinguals, particularly given the dependence of grammar on pars opercularis and nearby premotor cortex (Friederici, 2011).…”

Neural correlates of cognitive processing in monolinguals and bilinguals

“…While most studies accept that mean diffusivity (MD) is a measure of cellulitis and edema, one study showed the surprising finding that increases in this measure were associated with performance gains. Bakhtiari et al . found that both monolinguals and bilinguals had faster reading times with greater MD in the uncinate fasciculus, but that only bilinguals showed faster RTs with greater MD in the arcuate fasciculus and superior longitudinal fasciculus.…”