Intrinsic Functional Connectivity in the Adult Brain and Success in Second-Language Learning

Abstract

There is considerable variability in an individual's ability to acquire a second language (L2) during adulthood. Using resting-state fMRI data acquired before training in English speakers who underwent a 12 week intensive French immersion training course, we investigated whether individual differences in intrinsic resting-state functional connectivity relate to a person's ability to acquire an L2. We focused on two key aspects of language processing--lexical retrieval in spontaneous speech and reading speed--and computed whole-brain functional connectivity from two regions of interest in the language network, namely the left anterior insula/frontal operculum (AI/FO) and the visual word form area (VWFA). Connectivity between the left AI/FO and left posterior superior temporal gyrus (STG) and between the left AI/FO and dorsal anterior cingulate cortex correlated positively with improvement in L2 lexical retrieval in spontaneous speech. Connectivity between the VWFA and left mid-STG correlated positively with improvement in L2 reading speed. These findings are consistent with the different language functions subserved by subcomponents of the language network and suggest that the human capacity to learn an L2 can be predicted by an individual's intrinsic functional connectivity within the language network. Significance statement: There is considerable variability in second-language learning abilities during adulthood. We investigated whether individual differences in intrinsic functional connectivity in the adult brain relate to success in second-language learning, using resting-state functional magnetic resonance imaging in English speakers who underwent a 12 week intensive French immersion training course. We found that pretraining functional connectivity within two different language subnetworks correlated strongly with learning outcome in two different language skills: lexical retrieval in spontaneous speech and reading speed. Our results suggest that the human capacity to learn a second language can be predicted by an individual's intrinsic functional connectivity within the language network.

Keywords: VWFA; individual differences; insula; language; learning; resting-state fMRI.

Copyright © 2016 the authors 0270-6474/16/360755-07$15.00/0.

Figures

Figure 1.

Resting-state connectivity between the left AI/FO and left pSTG correlated with improvement in lexical retrieval during spontaneous speech. A, Location of the left AI/FO seed. B, The left pSTG cluster showed a significant relationship between connectivity strength and improvement in lexical retrieval during spontaneous speech. C, Left AI/FO–pSTG functional connectivity (Fisher's z) plotted against improvement in lexical retrieval during spontaneous speech.

Figure 2.

Resting-state connectivity between the VWFA and left mid-STG correlated with improvement in reading speed. A, Location of the VWFA seed. B, The left mid-STG cluster showed a significant relationship between connectivity strength and improvement in reading speed. C, VWFA–mid STG functional connectivity (Fisher's z) plotted against improvement in reading speed.