In search of the language switch: An fMRI study of picture naming in Spanish-English bilinguals

For many years, researchers investigating the brain bases of bilingualism have concentrated on two basic questions. The first concerns the nature of language representation. That is, are a bilinguals' two languages represented in distinct or overlapping areas of the brain. The second basic question in the neuropsychology of bilingualism concerns the neural correlates of language switching, that is, the areas that are active when bilinguals switch from one language to the other. Performance between single-language and dual-language picture naming was compared in a group of six Spanish-English bilinguals using behavioral measures and functional magnetic resonance imaging. Participants showed slower reaction times and increased activation in the dorsolateral prefrontal cortex in the mixed language condition relative to single language condition. There was no evidence that each language was represented in different areas of the brain. Results are consistent with the view that language switching is a part of a general executive attentional system and that languages are represented in overlapping areas of the brain in early bilinguals.     

The bimodal bilingual brain: effects of sign language experience

Bimodal bilinguals are hearing individuals who know both a signed and a spoken language. Effects of bimodal bilingualism on behavior and brain organization are reviewed, and an fMRI investigation of the recognition of facial expressions by ASL-English bilinguals is reported. The fMRI results reveal separate effects of sign language and spoken language experience on activation patterns within the superior temporal sulcus. In addition, the strong left-lateralized activation for facial expression recognition previously observed for deaf signers was not observed for hearing signers. We conclude that both sign language experience and deafness can affect the neural organization for recognizing facial expressions, and we argue that bimodal bilinguals provide a unique window into the neurocognitive changes that occur with the acquisition of two languages.     

Bilingual toddlers’ comprehension of mixed sentences is asymmetrical across their two languages

In bilingual language environments, infants and toddlers listen to two separate languages during the same key years that monolingual children listen to just one and bilinguals rarely learn each of their two languages at the same rate. Learning to understand language requires them to cope with challenges not found in monolingual input, notably the use of two languages within the same utterance (e.g., Do you like the perro? or ¿Te gusta el doggy?). For bilinguals of all ages, switching between two languages can reduce the efficiency in real‐time language processing. But language switching is a dynamic phenomenon in bilingual environments, presenting the young learner with many junctures where comprehension can be derailed or even supported. In this study, we tested 20 Spanish–English bilingual toddlers (18‐ to 30‐months) who varied substantially in language dominance. Toddlers’ eye movements were monitored as they looked at familiar objects and listened to single‐language and mixed‐language sentences in both of their languages. We found asymmetrical switch costs when toddlers were tested in their dominant versus non‐dominant language, and critically, they benefited from hearing nouns produced in their dominant language, independent of switching. While bilingualism does present unique challenges, our results suggest a united picture of early monolingual and bilingual learning. Just like monolinguals, experience shapes bilingual toddlers’ word knowledge, and with more robust representations, toddlers are better able to recognize words in diverse sentences.     

Language switching in the bilingual brain: What’s next?

Recent work using functional neuroimaging with early bilinguals has found little evidence for separate neural systems for each language during picture naming (Hernandez, A. E., Dapretto, M., Mazziotta, J., & Bookheimer, S. (2001). Language switching and language representation in Spanish–English bilinguals: An fMRI study. Neuroimage, 14, 510–520). However, switching between languages in early bilinguals during picture naming shows increased activity in the Dorsolateral Prefrontal Cortex (DLPFC) suggesting the importance of maintaining goal related information in order to bias subsequent response selection (Braver, T. S., Barch, D. M., Kelley, W. M., Buckner, R. L., Cohen, N. J., Miezin, F. M., et al. (2001). Direct comparison of prefrontal cortex regions engaged by working and long-term memory tasks. Neuroimage, 14, 48–59; Cohen, J. D., Braver, T. S., & O’Reilly, R. C. (1996). A computational approach to prefrontal cortex, cognitive control and schizophrenia: Recent developments and current challenges. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences, 351, 1515–1527; O’Reilly, R. C., Braver, T. S., & Cohen, J. D. (1999). A biologically based computational model of working memory. In E. Akira Miyake, E. Priti Shah & et al. (Eds.), Models of working memory: Mechanisms of active maintenance and executive control. (pp. 375–411): New York, NY, USA). The current study set out to test early bilinguals using a picture naming paradigm. Results revealed increased activity in the DLPFC and the superior parietal lobule during language switching compared to naming of pictures in a single language. Increased activity was also observed between early learned first and second languages. The results from single language conditions revealed differences in areas devoted to language processing such as the Superior Temporal Gyrus. However, increased activity in brain areas devoted to memory, somatosensory processing and emotion were also observed. Taken together these results replicate previous studies on language switching. They also extend studies on the neural bases of bilingualism by suggesting that early bilinguals’ representation of the two languages may be mediated by neural systems not typically associated with language. The article ends by considering future directions in understanding the brain bases of language switching and single language processing in bilinguals.     

Neural bases of language switching in high and early proficient bilinguals

The left inferior frontal cortex, the caudate and the anterior cingulate have been proposed as the neural origin of language switching, but most of the studies were conducted in low proficient bilinguals. In the present study, we investigated brain areas involved in language switching in a sample of 19 early, high-proficient Spanish–Catalan bilinguals using a picture naming task that allowed contrasting switch and non-switch trials. Compared to the non-switching condition, language switching elicited greater activation in the head of the left caudate and the pre-SMA/ACC. When the direction of the switching was considered, the left caudate was more associated with forward switching and the pre-SMA/ACC with backward switching. The discussion is focused on the relevance of these brain structures in language control in early, high-proficient bilinguals, and the comparison with previous results in late bilinguals.     

Are bilingual advantages dependent upon specific tasks or specific bilingual experiences?

Paap and Greenberg concluded that there is no coherent evidence for bilingual advantages in executive processing. More optimistic researchers believe that the advantages may be restricted to certain types of bilinguals. Recent large-scale and lifespan investigations that tested highly fluent bilinguals from communities where the same two languages are spoken by most residents reported no bilingual advantages in any age group or in any of the tasks used to measure executive functioning. The present study takes a complementary approach by examining a sample that is quite homogeneous in terms of current life experiences, but heterogeneous in terms of its exposure to second languages. The composite database of 168 bilinguals and 216 monolinguals is used to explore for differences based on: (1) the age of acquiring a second language (L2), (2) the relative proficiency of an L2 and (3) the number of languages used. Across 12 different measures of executive function, derived from 4 different nonverbal tasks, there was no consistent evidence supporting the hypotheses that either early bilingualism, highly fluent balanced bilingualism, or trilingualism enhances inhibitory control, monitoring or switching. In fact, when statistically significant effects did occur, they more often disconfirmed than confirmed these hypotheses.     

Language learning and control in monolinguals and bilinguals

Parallel language activation in bilinguals leads to competition between languages. Experience managing this interference may aid novel language learning by improving the ability to suppress competition from known languages. To investigate the effect of bilingualism on the ability to control native-language interference, monolinguals and bilinguals were taught an artificial language designed to elicit between-language competition. Partial activation of interlingual competitors was assessed with eye-tracking and mouse-tracking during a word recognition task in the novel language. Eye-tracking results showed that monolinguals looked at competitors more than bilinguals, and for a longer duration of time. Mouse-tracking results showed that monolinguals' mouse movements were attracted to native-language competitors, whereas bilinguals overcame competitor interference by increasing the activation of target items. Results suggest that bilinguals manage cross-linguistic interference more effectively than monolinguals. We conclude that language interference can affect lexical retrieval, but bilingualism may reduce this interference by facilitating access to a newly learned language.     

Dual language use in sign-speech bimodal bilinguals: fNIRS brain-imaging evidence

The brain basis of bilinguals’ ability to use two languages at the same time has been a hotly debated topic. On the one hand, behavioral research has suggested that bilingual dual language use involves complex and highly principled linguistic processes. On the other hand, brain-imaging research has revealed that bilingual language switching involves neural activations in brain areas dedicated to general executive functions not specific to language processing, such as general task maintenance. Here we address the involvement of language-specific versus cognitive-general brain mechanisms for bilingual language processing. We study a unique population, bimodal bilinguals proficient in signed and spoken languages, and we use an innovative brain-imaging technology, functional Near-Infrared Spectroscopy (fNIRS; Hitachi ETG-4000). Like fMRI, the fNIRS technology measures hemodynamic change, but it is also advanced in permitting movement for unconstrained speech and sign production. Participant groups included (i) hearing ASL–English bilinguals, (ii) ASL monolinguals, and (iii) English monolinguals. Imaging tasks included picture naming in “Monolingual mode” (using one language at a time) and in “Bilingual mode” (using both languages either simultaneously or in rapid alternation). Behavioral results revealed that accuracy was similar among groups and conditions. By contrast, neuroimaging results revealed that bilinguals in Bilingual mode showed greater signal intensity within posterior temporal regions (“Wernicke’s area”) than in Monolingual mode. Significance: Bilinguals’ ability to use two languages effortlessly and without confusion involves the use of language-specific posterior temporal brain regions. This research with both fNIRS and bimodal bilinguals sheds new light on the extent and variability of brain tissue that underlies language processing, and addresses the tantalizing questions of how language modality, sign and speech, impact language representation in the 7brain.     

Effects of Bilingual Language Use and Language Proficiency on 24-month-olds’ Cognitive Control

ABSTRACT

Although a bilingual advantage has been reported for various measures of cognitive control, most previous studies have looked at a limited range of cognitive control measures. Furthermore, they typically leave unaddressed whether positive effects of bilingualism hold for all bilinguals or whether these are modulated by differences in bilingual language use and proficiency of children and their parents. This study reports on tasks of selective attention and inhibitory control from 24-month-old bilinguals (n = 37) and monolinguals (n = 58). Their parents completed a Dutch vocabulary checklist assessing receptive and productive vocabulary as well as questionnaires on children’s attentional focusing, attention shifting and inhibitory control, and language background. Linear mixed-effect regressions showed no differences on cognitive control between the monolinguals and bilingual groups. However, analyses taking into account differences in children’s bilingual language use and proficiency and of their parents revealed a more nuanced picture. Specifically, children’s degree of balanced language usage predicted parent-rated cognitive control. Furthermore, bilingual toddlers who had parents were low proficient in one of the home languages showed significantly better performance on a selective attention task than toddlers whose parents were both proficient in both home languages. These findings suggest that both children’s active usage of two languages and their experience with switching depending on their interlocutor are related to cognitive control performance in young bilingual children. As such, they add to a growing body of evidence that the bilingual advantage in cognitive control is tied to specific conditions of bilingualism, already at a young age.     

双语和双言对图片命名和分类的不对称影响

采用普通话-英语双语者、粤语-普通话双言者和普通话单言者为被试, 比较他们图片命名与图片分类的成绩。结果表明, 普通话-英语双语者用优势语言命名图片的反应时比普通话单语者显著长, 错误率显著高。在第4次和第5次重复呈现图片时, 普通话-英语双语者与普通话单语者的命名反应差异不显著。普通话-英语双语者与普通话单语者对图片分类的反应差异不显著。这表明, 双语影响图片命名却不影响图片分类。粤语-普通话双言者对图片命名和图片分类的反应模式和普通话-英语双语者一致, 表明粤语-普通话双言和普通话-英语双语有类似的认知机制。普通话和粤语是作为两种语言储存在粤语-普通话双言者的头脑中的。     

汉-英和藏-汉-英双语者中、英文语码切换及代价研究

以汉—英和藏—汉—英双语者为被试,采用真假词判断范式,探讨中文和英文语码切换及代价。结果表明:(1)汉—英和藏—汉—英双语者中文语码切换代价不显著,英文语码切换代价显著;(2)汉—英和藏—汉—英双语者中、英文词加工差异显著,但语码切换趋势相同。这表明,加工方式和策略影响语言加工,不影响语码切换;语言熟练程度影响语码切换,两种语言的相对熟练程度决定切换代价的不对称性。     

Neuroanatomical profiles of bilingual children

The goal of the present study was to examine differences in cortical thickness, cortical surface area, and subcortical volume between bilingual children who are highly proficient in two languages (i.e., English and Spanish) and bilingual children who are mainly proficient in one of the languages (i.e., Spanish). All children (N = 49) learned Spanish as a native language (L1) at home and English as a second language (L2) at school. Proficiency of both languages was assessed using the standardized Woodcock Language Proficiency Battery. Five‐minute high‐resolution anatomical scans were acquired with a 3‐Tesla scanner. The degree of discrepancy between L1 and L2 proficiency was used to classify the children into two groups: children with balanced proficiency and children with unbalanced proficiency. The groups were comparable on language history, parental education, and other variables except English proficiency. Values of cortical thickness and surface area of the transverse STG, IFG‐pars opercularis, and MFG, as well as subcortical volume of the caudate and putamen, were extracted from FreeSurfer. Results showed that children with balanced bilingualism had thinner cortices of the left STG, left IFG, left MFG and a larger bilateral putamen, whereas unbalanced bilinguals showed thicker cortices of the same regions and a smaller putamen. Additionally, unbalanced bilinguals with stronger foreign accents in the L2 showed reduced surface areas of the MFG and STS bilaterally. The results suggest that balanced/unbalanced bilingualism is reflected in different neuroanatomical characteristics that arise from biological and/or environmental factors.     

Neurolinguists, beware! The bilingual is not two monolinguals in one person

Two views of bilingualism are presented--the monolingual or fractional view which holds that the bilingual is (or should be) two monolinguals in one person, and the bilingual or wholistic view which states that the coexistence of two languages in the bilingual has produced a unique and specific speaker-hearer. These views affect how we compare monolinguals and bilinguals, study language learning and language forgetting, and examine the speech modes--monolingual and bilingual--that characterize the bilingual's everyday interactions. The implications of the wholistic view on the neurolinguistics of bilingualism, and in particular bilingual aphasia, are discussed.     

Convergent cortical representation of semantic processing in bilinguals

This study examined whether semantic processes in two languages (English and Spanish) are mediated by a common neural system in fluent bilinguals who acquired their second language years after acquiring their first language. Functional magnetic resonance imaging was performed while bilingual participants made semantic and nonsemantic decisions about words in Spanish and English. There was greater activation for semantic relative to nonsemantic decisions in left and right frontal regions, with greater left frontal activation. The locations of activations were similar for both languages, and no differences were found when semantic decisions for English and Spanish words were compared directly. These results demonstrate a shared frontal lobe system for semantic analysis of the languages and are consistent with cognitive research on bilingualism indicating that the two languages of a bilingual person access a common semantic system.     

认知灵活性对非熟练双语者语言转换的影响--一项ERPs研究*

采用 WCST 筛选出高低认知灵活性的非熟练汉英双语者,分别使用图片命名和语义范畴判断任务考察认知灵活性对双语者语言转换的影响。结果发现：(1)高认知灵活性被试的双语转换代价是对称的,其N2成分的平均波幅和峰值显著大于低认知灵活性被试,低认知灵活性被试的转换代价是非对称的;(2)高认知灵活性被试在语言产生任务中, L2重复条件下N2的峰值显著大于L1重复条件,出现L2重复优势效应;(3)在语言理解任务中,高低认知灵活性被试在L1重复条件下的N2峰值显著大于L2重复条件,两组均出现了L1重复优势效应。研究表明,抑制控制能力在语言产生与理解的双语转换中起着重要的作用,语言转换代价源于心理词典的字词识别系统之外。     

How do highly proficient bilinguals control their lexicalization process? Inhibitory and language-specific selection mechanisms are both functional

The authors report 4 experiments exploring the language-switching performance of highly proficient bilinguals in a picture-naming task. In Experiment 1, they tested the impact of language similarity and age of 2nd language acquisition on the language-switching performance of highly proficient bilinguals. Experiments 2, 3, and 4 assessed the performance of highly proficient bilinguals in language-switching contexts involving (a) the 2nd language (L2) and the L3 of the bilinguals, (b) the L3 and the L4, and (c) the L1 and a recently learned new language. Highly proficient bilinguals showed symmetrical switching costs regardless of the age at which the L2 was learned and of the similarities of the 2 languages and asymmetrical switching costs when 1 of the languages involved in the switching task was very weak (an L4 or a recently learned language). The theoretical implications of these results for the attentional mechanisms used by highly proficient bilinguals to control their lexicalization process are discussed.     

The bilingual brain: cerebral representation of languages.

The present article deals with theoretical and experimental aspects of language representation in the multilingual brain. Two general approaches were adopted in the study of the bilingual brain. The study of bilingual aphasics allows us to describe dissociations and double dissociations between the different subcomponents of the various languages. Furthermore, symptoms peculiar to bilingual aphasia were reported (pathological mixing and switching and translations disorders) which allowed the correlation of some abilities specific to bilinguals with particular neurofunctional systems. Another approach to the study of the bilingual brain is of the experimental type, such as electrophysiological investigations (electrocorticostimulation during brain surgery and event-related potentials) and functional neuroanatomy studies (positron emission tomography and functional magnetic resonance imaging). Functional neuroanatomy studies investigated the brain representation of languages when processing lexical and syntactic stimuli and short stories. Neurophysiologic and neuroimaging studies evidenced a similar cerebral representation of L1 and L2 lexicons both in early and late bilinguals. The representation of grammatical aspects of languages seems to be different between the two languages if L2 is acquired after the age of 7, with automatic processes and correctness being lower than those of the native language. These results are in line with a greater representation of the two lexicons in the declarative memory systems, whereas morphosyntactic aspects may be organized in different systems according to the acquisition vs learning modality.     

A disadvantage in bilingual sentence production modulated by syntactic frequency and similarity across languages

Bilingual speakers access individual words less fluently, quickly, and accurately than monolinguals, particularly when accessing low-frequency words. Here we examined whether the bilingual speech production disadvantage would (a) extend to full sentences above and beyond single word retrieval and whether it would be modulated by (b) structural frequency and (c) syntactic properties of the bilingual speakers’ other language. English monolinguals, Spanish–English bilinguals and Mandarin–English bilinguals were tested in a sentence production task conducted exclusively in English. Response times were modulated by bilingualism, structural frequency, and structural similarity across the bilingual speakers’ two languages. These results refine our knowledge regarding the scope of the bilingual disadvantage, demonstrate that frequency effects apply to syntactic structures, and also suggest that syntax is partially shared across bilinguals’ two languages.     

双语经验对认知能力的影响

综合近年关于双语经验对认知影响的研究, 探讨双语经验对认知的积极和消极两方面的影响, 且着重介绍了双语经验对认知的积极影响。双语经验对认知的积极影响主要体现在语言认知能力、非语言认知能力和中央执行功能几个方面。此外, 进一步对双语促进认知发展的原因进行了两方面的分析：一个是双语思维经验促进抑制控制的发展, 另一个双语学习经验强化双语者的左右脑交流, 从而导致脑功能活动方式的变化。最后, 对今后双语与认知关系的研究中需要注意的问题提出了一些思考。     

语言产生过程中非目标语言的激活与抑制

运用长时重复启动范式, 探讨熟练和非熟练中－英双语者语言产生过程中非目标语言的激活与抑制。实验1探讨双语被试在学习阶段使用中文进行图片命名任务时, 非目标语言英文概念层面的激活与抑制情况, 结果发现, 两种熟练水平的被试均没有出现重复启动效应; 实验2探讨双语被试在学习阶段使用英文进行图片命名任务时, 非目标语言中文概念层面的激活与抑制情况, 结果发现, 熟练双语被试没有出现重复启动效应, 而非熟练双语被试出现了重复启动效应; 实验3探讨非熟练双语被试在学习阶段使用英文进行图片命名任务时, 非目标语言中文词汇层面的激活与抑制情况, 结果没有出现重复启动效应。综合三个实验的结果可以表明, 熟练中－英双语者语言产生过程中在概念层面上就对非目标语言(不管是一语还是二语)进行了抑制, 而非熟练中－英双语者使用一语时可以在概念层面上抑制非目标语言(二语), 但使用二语时不能在概念层面上抑制非目标语言(一语), 要在词汇层面上才能抑制非目标语言(一语)。