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Poster A67, Wednesday, November 8, 10:30 – 11:45 am, Harborview and Loch Raven Ballrooms

Spontaeous fluctuations of dorsal and ventral reading networks in bilinguals

Jaione Arnaez-Telleria1, Myriam Oliver1, Manuel Carreiras1,2, Pedro M. Paz-Alonso1;1BCBL. Basque Center on Cognition, Brain and Language, Donostia-San Sebastian, Spain., 2IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.

Over half of the world's population is bilingual. Despite this fact, most neuroimaging research on reading has studied monolingual readers. Although we know that learning to read in the native language (L1) entails a substantial reorganization of the brain, there are many questions still unanswered about bilingualism and the neural dynamics supporting reading in L1 and in a second language (L2). The dual-stream hypothesis proposes a differential involvement of left-lateralized ventral and dorsal networks in reading processes: Whereas the ventral pathway, including the ventral occipito-temporal cortex (vOT) and anterior inferior frontal gyrus (IFG) regions, supports mapping of orthographic-lexical stimuli onto semantic representations; the dorsal pathway, encompassing parietal lobe, superior temporal gyrus (STG) and IFG pars opercularis, is thought to subserve phonological processing. Although this model has received extensive support from neuroimaging research, it has not been systematically examined in bilinguals and in relation to the main critical factors associated with changes in in the neural correlates of bilingual reading, such as the L2 age-of-acquisition (AoA). Here, we sought to investigate differences in resting-state functional connectivity MRI (rs-fcMRI) within ventral and dorsal reading networks used for L1 and L2 reading as a function of the L2 AoA, while matching participants' age, language proficiency and daily exposure to their L1 and L2. Sixty-five right-handed Spanish monolinguals (n = 22) and Spanish-Basque bilinguals, who acquired their L2 before age 3 (early bilinguals; n = 21) or after age 6 (late bilinguals; n = 22), participated. All of them had minimal exposure to other languages. Based on a L1 and L2 fMRI reading task we identified the highest local maximas for each of the main left and right-lateralized nodes within the ventral (vOT, pars triangularis, pars orbitalis) and dorsal (inferior parietal cortex, STG, pars opercularis) reading networks separately per group (monolinguals, early bilinguals, late bilinguals) and language (L1, L2). Coordinates from these local maximas were used as the centers of mass to build 5-mm radius spheres that were submitted to rs-fcMRI analyses. For all analysis involving L2, monolinguals were excluded and were used as a control group to compare their results with those of the bilinguals in their L1. Results showed that all three groups (i.e., monolinguals, early bilinguals, late bilinguals) exhibited a similar rs-fcMRI pattern for L1 reading nodes across both ventral and dorsal networks. However, changes in the coactivation profiles at rest were observed among early and late bilinguals. Whereas early bilinguals showed a stronger coupling for L2 than for L1 nodes across both reading networks, late bilinguals exhibited a Language by Network interaction due to a significant decrease in the coactivation of the ventral network for L2 relative to L1 reading nodes and a subsequent stronger coupling of the dorsal compared to the ventral network for L2 reading nodes. Our findings suggest a shift in the reliance of the spontaneous fluctuations carried out by the ventral route from L1 to L2 reading, constituting the strongest evidence of changes in large-scale reading networks in bilinguals as a function of the L2 AoA.

Topic Area: Multilingualism

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