Intraoperative electrical stimulation of language switching in two bilingual patients.

BACKGROUND: Language switching (LS) is an important phenomena usually observed in some bilingual communities. The ability to switch languages is a very fast, efficient and flexible process, being a fundamental aspect of bilingual efficient language communication. The aim of the present study was to characterize the specific role of non-language specific prefrontal regions in the neural network involved in LS in bilingual patients, during awake brain surgery and using electrical stimulation mapping (ESM). METHODS: In order to identify the neural regions involved in LS we used, a new specific ESM protocol in two patients undergoing awake brain surgery. Besides, functional magnetic resonance imaging (fMRI), neuropsychological testing and the assessment of daily conversational LS patterns post-surgery were used as complementary imaging and behavioral assessments. RESULTS: The outcome of the multimodal ESM-fMRI neuroimaging comparison in both patients pointed out to the crucial involvement of the inferior and middle frontal cortices in LS. CONCLUSIONS: The present results add to previous findings highlighting the important role of non-language specific frontal structures in regulating LS. The new protocol developed here might allow neurosurgeons to plan ahead for surgical intervention in multilingual patients to ensure the preservation of regions involved in LS and therefore the prevention of pathological language mixing after intervention.