Whether the native language of bilingual individuals is active during second-language comprehension is the subject of lively debate. Studies of bilingualism have often used a mix of first-and second-language words, thereby creating an artificial ''dual-language'' context. Here, using event-related brain potentials, we demonstrate implicit access to the first language when bilinguals read words exclusively in their second language. Chinese-English bilinguals were required to decide whether English words presented in pairs were related in meaning or not; they were unaware of the fact that half of the words concealed a character repetition when translated into Chinese. Whereas the hidden factor failed to affect behavioral performance, it significantly modulated brain potentials in the expected direction, establishing that English words were automatically and unconsciously translated into Chinese. Critically, the same modulation was found in Chinese monolinguals reading the same words in Chinese, i.e., when Chinese character repetition was evident. Finally, we replicated this pattern of results in the auditory modality by using a listening comprehension task. These findings demonstrate that native-language activation is an unconscious correlate of second-language comprehension.bilingualism ͉ event-related potentials ͉ language access ͉ semantic priming ͉ unconscious priming S ome studies in cognitive neuroscience have suggested that fluent bilinguals can effectively inhibit their first language when accessing word meaning in their second language based on the word form (1). However, this finding conflicts with functional neuroimaging data showing overlapping cortical representation of the two languages (2, 3). A number of psycholinguistic experiments have also suggested that the two languages mastered by one individual are constantly coactivated and interactive (4-7), whereas others have provided evidence for language independence (8, 9). It therefore remains an open question whether or not bilingual individuals can effectively suppress all interference from their first language when processing their second language (10).Previous studies have made extensive use of cross-language priming (6, 9, 11) or overt translation tasks (12, 13) to compare native-and second-language activation in bilinguals. For example, reaction time is reduced in French-English bilinguals when the English word money is presented after the French word coin ''corner'' relative to when it is presented after feuille ''leaf.'' However, mixing stimuli from two languages creates an artificial context that necessarily biases the output of behavioral tests toward a bilingual or ''dual-language'' activation pattern (14). For that matter, translation tasks are even more biased because they require conscious access to both languages. In fact, any experiment mixing stimuli from two languages or using interlingual homographs is likely to activate both languages, even if native-language activation is not automatic during everyday second-language comprehensio...

Bilingual individuals have been shown to access their native language while reading in or listening to their other language. However, it is unknown what type of mental representation (e.g., sound or spelling) they retrieve. Here, using event-related brain potentials, we demonstrate unconscious access to the sound form of Chinese words when advanced Chinese-English bilinguals read or listen to English words. Participants were asked to decide whether or not English words presented in pairs were related in meaning; they were unaware of the fact that some of the unrelated word pairs concealed either a sound or a spelling repetition in their Chinese translations. Whereas spelling repetition in Chinese translations had no effect, concealed sound repetition significantly modulated event-related brain potentials. These results suggest that processing second language activates the sound, but not the spelling, of native language translations.

Mastering two languages has been associated with enhancement in human executive control, but previous studies of this phenomenon have exclusively relied on comparisons between bilingual and monolingual individuals. In the present study, we tested a single group of WelshEnglish bilinguals engaged in a nonverbal conflict resolution task and manipulated language context by intermittently presenting words in Welsh, English, or both languages. Surprisingly, participants showed enhanced executive capacity to resolve interference when exposed to a mixed compared with a single language context, even though they ignored the irrelevant contextual words. This result was supported by greater response accuracy and reduced amplitude of the P300, an electrophysiological correlate of cognitive interference. Our findings introduce a new level of plasticity in bilingual executive control dependent on fast changing language context rather than long-term language experience.

Reading words in a second language spontaneously activates native language translations in the human bilingual mind. Here, we show that the emotional valence of a word presented in English constrains unconscious access to its Chinese translation. We asked native speakers of Chinese fluent with English to indicate whether or not pairs of English words were related in meaning while monitoring their brain electrical activity. Unbeknownst to the participants, some of the word pairs hid a sound repetition if translated into Chinese. Remarkably, English words with a negative valence such as "violence" did not automatically activate their Chinese translation, even though we observed the expected sound repetition priming effect for positive and neutral words, such as "holiday" and "theory." These findings show that emotion conveyed by words determines language activation in bilinguals, where potentially disturbing stimuli trigger inhibitory mechanisms that block access to the native language.

The putamen is a subcortical structure that forms part of the dorsal striatum of basal ganglia, and has traditionally been associated with reinforcement learning and motor control, including speech articulation. However, recent studies have shown involvement of the left putamen in other language functions such as bilingual language processing (Abutalebi et al. 2012) and production, with some authors arguing for functional segregation of anterior and posterior putamen (Oberhuber et al. 2013). A further step in exploring the role of putamen in language would involve identifying the network of coactivations of not only the left, but also the right putamen, given the involvement of right hemisphere in high order language functions (Vigneau et al. 2011). Here, a meta-analytic connectivity modeling technique was used to determine the patterns of coactivation of anterior and bilateral putamen in the language domain. Based on previous evidence, we hypothesized that left putamen coactivations would include brain regions directly associated with language processing, whereas right putamen coactivations would encompass regions involved in broader semantic processes, such as memory and visual imagery. The results showed that left anterior putamen coactivated with clusters predominantly in left hemisphere, encompassing regions directly associated with language processing, a left posterior putamen network spanning both hemispheres, and cerebellum. In right hemisphere, coactivations were in both hemispheres, in regions associated with visual and orthographic processing. These results confirm the differential involvement of right and left putamen in different language components, thus highlighting the need for further research into the role of putamen in language.

Previous studies have demonstrated that language switching in bilinguals can be affected by a number of variables, including the processing context. Here, we used a modified language-switching task combined with a Stroop paradigm, which manipulated the context of the task, to examine the impact of processing context on switch costs. The results of both Experiment 1 and Experiment 2 showed that the switch costs and the level of asymmetry in the switch costs are larger in the conflicting context than in the non-conflicting context, suggesting that the processing context affects the switch costs. In addition, the results of Experiment 2 revealed that individual variances in cognitive control capacity also play a role in the overall magnitude of the switch costs. Critically, processing context effects can be modulated by individual variance in cognitive control capacities. The results of this study are discussed within the framework of classic models of bilingual language control (e.g., the inhibitory control model).

The present study examined how a short period of language switching training affects nonverbal cognitive control, as measured by the AX version of the Continuous Performance Test. A group of Chinese-English bilinguals were trained over 10 days on a picture naming task that required switching between languages. We recorded their behavioral performance and event-related potentials before and after the training to examine its effects on cognitive performance. The behavioral measurement of proactive control, that is, goal maintenance before the occurrence of the target, is significantly larger in the post-training phase as compared with the pretraining phase, indicating a proactive control shift. The event-related potential results show that the training led to an increase in the mean amplitude of the N2 component, elicited by both the cue and the probe stimuli. A group of control participants who did not undergo training showed an enlarged N2 only for the probe but not for the cue stimuli in the second as compared with the first phase of testing. No variations in behavioral performance were found in the control group between the two phases of testing. These findings suggest that language switching training enhances proactive control in bilinguals.

How do the two languages of bilingual individuals interact in everyday communication? Numerous behavioral- and event-related brain potential studies have suggested that information from the non-target language is spontaneously accessed when bilinguals read, listen, or speak in a given language. While this finding is consistent with predictions of current models of bilingual processing, most paradigms used so far have mixed the two languages by using language ambiguous stimuli (e.g., cognates or interlingual homographs) or explicitly engaging the two languages because of experimental task requirements (e.g., word translation or language selection). These paradigms will have yielded different language processing contexts, the effect of which has seldom been taken into consideration. We propose that future studies should test the effect of language context on cross-language interactions in a systematic way, by controlling and manipulating the extent to which the experiment implicitly or explicitly prompts activation of the two languages.