Variation in language networks in monolingual and bilingual English speakers: consequences for language mapping for surgical preplanning.

Proficient, nonnative English-speaking neurosurgery candidates are assessed for language function in English. In order to understand whether it is necessary to also assess native-language function, we examined the influence of native language on the bilingual language network of early, proficient bilinguals using functional magnetic resonance imaging (fMRI). We compared the blood-oxygen-level-dependent (BOLD) response to a language task in well-matched groups of monolingual native English speakers (MLEs), bilingual native English speakers (BLE1s), and bilingual nonnative English speakers (BLE2s). Random effects analysis revealed a significant main effect of group in temporal-parietal regions highly germane to the planning of temporal lobe surgical procedures. To explore how the three groups differed, we examined the average time course in each area of main effect for each group. We found significant differences between the monolinguals and the two bilingual groups. We interpret our results as evidence for a difference between the language network of early bilinguals and that of monolinguals.