Functional lateralization of tool-sound and action-word processing in a bilingual brain

Abstract

BackgroundThe impact of bilingualism on lateralized brain functions such as praxis – the control of skilled actions – and language representations themselves, particularly in the auditory domain, is still largely unknown. Recent stud-ies suggest that bilingualism affects both basic (fundamental frequency) sound and action-related speech pro-cessing. Whether it can impact non-verbal action sound processing is a question of debate.Participants and procedureHere we examined twenty bilinguals using a dichotic listening paradigm, in which in addition to repeating the just heard action words, participants named – in Polish or English – one of two simultaneously presented tool sounds from attended ears. The results were compared with data from these same participants tested with reading the same words in a visual-half field paradigm.ResultsIn contrast to typical outcomes from monolinguals, the laterality indices of action-related sound processing (verbal and non-verbal) were not left lateralized but hemispherically balanced. Notably, despite similar organi-zation of tool- and action-word sound processing, their auditory (balanced) and visual-language (left-lateralized) representations might be independent because there were no significant correlations between any of their laterality indices.ConclusionsThis indicates that bilingualism might involve reshuffling/reorganization of typically lateralized brain functions and such plasticity will have consequences for second language learning strategies, as well as for neuroreha-bilitation.