Electrophysiological correlates of memory processing in early Finnish-Swedish bilinguals.

Event-related desynchronization (ERD) and event-related synchronization (ERS) of the 1-30 EEG frequencies were studied in eight early Finnish-Swedish bilinguals during an auditory bilingual Sternberg memory task using Finnish-Swedish cognates as stimuli. Only subtle differences between languages were expected, since cognates have been assumed to have shared conceptual representations in the bilingual memory. Encoding elicited theta and alpha frequency ERS and beta frequency ERD responses in both languages. Retrieval elicited theta ERS and alpha and beta ERD responses. Some statistically significant differences between encoding and retrieval in Finnish versus Swedish emerged: greater theta and alpha ERS responses were observed during encoding in Swedish than during encoding in Finnish. During between-language retrieval, later-appearing theta ERS and alpha ERD responses were elicited as compared to within-language retrieval. These delayed oscillatory responses might reflect the involvement of central executive attentional functions in relation to language switching.