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Language switching involves multiple processing stages. Previous studies have not dissociated the cognitive process underlying language form switches and concept switches. Here, we examined the two factors using a novel language-switching paradigm. Chinese-English bilinguals named individually presented pictures in either Chinese or English according to a language cue. Pictures in two consecutive trials represented either identical, semantically related, or unrelated concepts. Results showed both language (form) switch costs and concept switch costs. The interaction between these two factors suggested that the effects were additive, with the longest naming response times observed when two pictures were semantically unrelated and involved a switch between languages. These findings suggest that the functional loci of the language control mechanism occur at multiple processing stages. Implications of the findings are discussed within current models of language processing in bilinguals.

The present functional magnetic resonance imaging (fMRI) study investigated influences of language contexts on inhibitory control and the underlying neural processes. Thirty Cantonese-Mandarin-English trilingual speakers, who were highly proficient in Cantonese (L1) and Mandarin (L2), and moderately proficient in English (L3), performed a picture-naming task in three dual-language contexts (L1-L2, L2-L3, and L1-L3). After each of the three naming tasks, participants performed a flanker task, measuring contextual effects on the inhibitory control system. Behavioral results showed a typical flanker effect in the L2-L3 and L1-L3 condition, but not in the L1-L2 condition, which indicates contextual facilitation on inhibitory control performance by the L1-L2 context. Whole brain analysis of the fMRI data acquired during the flanker tasks showed more neural activations in the right prefrontal cortex and subcortical areas in the L2-L3 and L1-L3 condition on one hand as compared to the L1-L2 condition on the other hand, suggesting greater involvement of the cognitive control areas when participants were performing the flanker task in L2-L3 and L1-L3 contexts. Effective connectivity analyses displayed a cortical-subcortical-cerebellar circuitry for inhibitory control in the trilinguals. However, contrary to the right-lateralized network in the L1-L2 condition, functional networks for inhibitory control in the L2-L3 and L1-L3 condition are less integrated and more left-lateralized. These findings provide a novel perspective for investigating the interaction between bilingualism (multilingualism) and inhibitory control by demonstrating instant behavioral effects and neural plasticity as a function of changes in global language contexts.

Emotionally valenced words have thus far not been empirically examined in a bilingual population with the emotional face-word Stroop paradigm. Chinese-English bilinguals were asked to identify the facial expressions of emotion with their first (L1) or second (L2) language task-irrelevant emotion words superimposed on the face pictures. We attempted to examine how the emotional content of words modulated behavioral performance and cerebral functioning in the bilinguals' two languages. The results indicated that there were significant congruency effects for both L1 and L2 emotion words, and that identifiable differences in the magnitude of the Stroop effect between the two languages were also observed, suggesting L1 is more capable of activating the emotional response to word stimuli. For event-related potentials data, an N350-550 effect was observed only in the L1 task with greater negativity for incongruent than congruent trials. The size of the N350-550 effect differed across languages, whereas no identifiable language distinction was observed in the effect of conflict slow potential (conflict SP). Finally, more pronounced negative amplitude at 230-330 ms was observed in L1 than in L2, but only for incongruent trials. This negativity, likened to an orthographic decoding N250, may reflect the extent of attention to emotion word processing at word-form level, while the N350-550 reflects a complicated set of processes in the conflict processing. Overall, the face-word congruency effect has reflected identifiable language distinction at 230-330 and 350-550 ms, which provides supporting evidence for the theoretical proposals assuming attenuated emotionality of L2 processing.