An MEG study of the spatiotemporal dynamics of bilingual verb generation

Studies of first (L1) and second (L2) language representation in the brain have not identified the timing and locations of neural regions involved in L1 and L2 processing. Magnetoencephalography offers high spatial and temporal resolution and can be employed to disentangle subtle timing and neural control differences between L1 and L2 use. We tested bilingual adults in the MEG as they completed a picture verb generation task in L1 and L2. We found the expected progression of activation from occipital to temporal to inferior frontal areas. We also observed the following differences. A sustained insula and early cingulate event-related desynchrony was observed only with L2; the fMRI literature suggests that the former reflects an activation, and the latter an inhibition, sub-process for language selection. L2 processes exhibited a lag and were bilateral compared to L1 processes. Finally, L1 and L2 activated adjacent language control in dorsolateral pre-frontal cortex.

► Bilingual adults generated verbs in their first (L1) and second (L2) languages.
► Magnetoencephalography (MEG) captured left inferior frontal (BA 47) involvement with both L1 and L2 use.
► L2 language processing was more bilateral and lagged behind L1 processing.
► Insula and cingulate were seen only for L2 suggesting activation/inhibition processing.
► Dorsolateral prefrontal areas were adjacent but non-overlapping for L1 and L2.