Language-specific regions in the supplementary motor area: Evidence from verb generation during electrical stimulation mapping

Language representation has been attributed to the perisylvian areas of the left hemisphere, with a more widely distributed network in multilingual populations. However, multilingual evidence has long obviated the involvement of regions outside classical perisylvian areas, such as the supplementary motor area (SMA). We aimed to provide novel evidence on the SMA's role in language localization using electrical stimulation mapping (ESM) during awake brain surgery. We conducted a case-series study of 4 bilingual or multilingual patients with an expansive brain lesion near the SMA who underwent an ESM. Our results evidenced that the stimulation of the left-SMA induced language difficulties during a verb generation task, with a higher proportion of language-specific sites in the pre-SMA region. Moreover, we reported specific language sites for multiple acquired languages. Overall, our study highlighted the SMA as a language-eloquent area, likely linked to lexical decisions, while also being sensitive to different-but not necessarily all-languages of a patient.