Bilingual language processing relies on shared semantic representations that are modulated by each language

Abstract Billions of people throughout the world are bilingual, and they can extract meaning from multiple languages. While some evidence suggests that there is a shared system in the human brain for processing semantic information from native and non-native languages, other evidence suggests that semantic processing is language-specific. We conducted a study to determine how semantic information for different languages is represented in the brains of bilinguals. Functional magnetic resonance imaging (fMRI) was used to record brain responses while participants read several hours of natural narratives in their native (Chinese) and non-native (English) languages. These data were then used to compare semantic representations between the two languages. We find that semantic representations are largely shared between languages, but that there are fine-grained differences in the representation of some semantic categories across languages. These results reconcile current competing theories of bilingual language processing. Significance Statement Bilinguals understand the meaning of words in multiple languages. Whether this capacity reflects a shared brain system for processing both native and non-native languages, or whether processing is language-specific is still unclear. Here, we examine whether and how semantic representations in the brain support shared and/or language-specific processing. We recorded brain activity from participants reading narratives in their native (Chinese) and non-native (English) languages, and modeled how their brains represent word meaning in each language. We show that semantic representations are similar between the two language conditions, and that these representations are systematically modulated between native and non-native language comprehension.