Transient selective aphasia in highly proficient bilinguals triggered by electrical stimulation of the left superior temporal gyrus

Are an individual’s first (L1) and second (L2) languages represented in shared or distinct brain territories? Using intraoperative electrical stimulation mapping (ESM) in two Basque-Spanish bilinguals with non-growing lesions—thus avoiding confounding effects of adaptive plasticity—this study identified distinct language representations within the left temporal lobe. Stimulation of posterior and anterior superior temporal gyri induced language-selective aphasias, whereas stimulation of the mid-temporal region and inferior fronto-occipital fasciculus produced naming errors without language specificity. These findings highlight both shared and distinct loci for L1 and L2, advancing our understanding of bilingual brain organization.