A pre-registered scoping review of neuroimaging evidence concerning lexico-semantic processing in multilingual speakers

This scoping review examines neuroimaging and neurophysiology methodologies and findings related to lexico-semantic processing in multilingual individuals. To understand what functional neuroimaging and neurophysiology results have been associated with multilingual lexico-semantic processing and to what extent these findings converge, we analyzed 163 studies utilizing fMRI, fNIRS, EEG, and MEG, focusing on the paradigms employed, language assessment approaches, and reported neural correlates. Our review revealed that while lexico-semantic representations in the first language (L1) and second language (L2) become increasingly similar with greater L2 experience, this similarity is modulated by the specific lexico-semantic process under investigation. We highlight the differential role of language experience variables on lexico-semantic processes, including embodied processing. We incorporate studies of unimodal and bimodal signing bilinguals to move beyond the speech modality, combining research populations that have been typically reviewed separately, to summarize evidence on language experience and cross-modal transfer of lexico-semantic processes in multilinguals. Furthermore, we underscore a critical need for increased data and code transparency in the field to enhance reproducibility and facilitate a cumulative understanding of multilingual lexico-semantic processing. This review identifies key gaps in the literature and offers recommendations for future research to advance our understanding of how multilingualism shapes the neural organization of lexico-semantic knowledge.