Neural correlates of nouns and verbs in early bilinguals.

Previous neuroimaging research indicates that English verbs and nouns are represented in frontal and posterior brain regions, respectively. For Chinese monolinguals, however, nouns and verbs are found to be associated with a wide range of overlapping areas without significant differences in neural signatures. This different pattern of findings led us to ask the question of where nouns and verbs of two different languages are represented in various areas in the brain in Chinese-English bilinguals. In this study, we utilized functional magnetic resonance imaging (fMRI) and a lexical decision paradigm involving Chinese and English verbs and nouns to address this question. We found that while Chinese nouns and verbs involved activation of common brain areas, the processing of English verbs engaged many more regions than did the processing of English nouns. Specifically, compared to English nouns, English verb presentation was associated with stronger activation of the left putamen and cerebellum, which are responsible for motor function, suggesting the involvement of the motor system in the processing of English verbs. Our findings are consistent with the theory that neural circuits for linguistic dimensions are weighted and modulated by the characteristics of a language.