Functional and structural neuroplasticity associated with second language proficiency: An MRI study of Chinese-English bilinguals

Second language (L2) learning modulates functional and anatomical neuroplasticity, as amply demonstrated by previous studies (see Li, Legault, & Litcofsky, 2014, for review). This study, combining resting-state functional magnetic resonance imaging (rs-fMRI), task-based fMRI, and structural MRI (sMRI), examined L2 learning-induced cross-modality neural changes in Chinese-English bilinguals with low- to high-intermediate L2 proficiency. Our rs-MRI data showed a positive correlation between the participants' amplitude of low-frequency fluctuation (ALFF) and their L2 proficiency in brain areas within the salience network, implying L2 learning experience-associated cognitive flexibility. Further, fMRI data of the L2 picture naming task, compared with that of the L1 processing, displayed more neural activation in cognitive control and language control areas, and the increase correlated positively with the L2 proficiency. Finally, gray-matter volume (GMV) analyses of sMRI data revealed enlarged GMV in an extensive brain network in higher-proficiency bilinguals, which coincided with their functional changes. Our multimodal imaging data converge to support an essential role of the right fusiform gyrus in Chinese native speakers learning L2 as late non-proficient bilinguals, which may pertain to the logographic nature of their L1 Chinese. Our findings shed light on the neural plasticity of L2 learning and suggest that both L1 and L2 experiences shape the bilingual brain.