Convergent cortical representation of semantic processing in bilinguals

Neural substrates of L2-L1 transfer effects on phonological awareness in young Chinese-English bilingual children

The growing trend of bilingual education between Chinese and English has contributed to a rise in the number of early bilingual children, who were exposed to L2 prior to formal language instruction of L1. The L2-L1 transfer effect in an L1-dominant environment has been well established. However, the threshold of L2 proficiency at which such transfer manifests remains unclear. This study investigated the behavioral and neural processes involved when manipulating phonemes in an auditory phonological task to uncover the transfer effect in young bilingual children. Sixty-two first graders from elementary schools in Taiwan were recruited in this study (29 Chinese monolinguals, 33 Chinese-English bilinguals). The brain activity was measured using fNIRS (functional near-infrared spectroscopy). Bilingual children showed right lateralization to process Chinese and left lateralization to process English, which supports more on the accommodation effect within the framework of the assimilation-accommodation hypothesis. Also, compared to monolinguals, bilingual children showed more bilateral frontal activation in Chinese, potentially reflecting a mixed influence from L2-L1 transfer effects and increased cognitive load of bilingual exposure. These results elucidate the developmental adjustments in the neural substrates associated with early bilingual exposure in phonological processing, offering valuable insights into the bilingual learning process.

Application of a Standardized Treatment Paradigm as a Strategy to Achieve Optimal Onco-Functional Balance in Glioma Surgery

BACKGROUND

Gliomas, characterized by their invasive persistence and tendency to affect critical brain regions, pose a challenge in surgical resection due to the risk of neurological deficits. This study focuses on a personalized approach to achieving an optimal onco-functional balance in glioma resections, emphasizing maximal tumor removal while preserving the quality of life.

METHODS

A retrospective analysis of 57 awake surgical resections of gliomas at the National University Hospital, Singapore, was conducted. The inclusion criteria were based on diagnosis, functional boundaries determined by direct electrical stimulation, preoperative Karnofsky Performance Status score, and absence of multifocal disease on MRI. The treatment approach included comprehensive neuropsychological evaluation, determination of suitability for awake surgery, and standard asleep-awake-asleep anesthesia protocol. Tumor resection techniques and postoperative care were systematically followed.

RESULTS

The study included 53 patients (55.5% male, average age 39 years), predominantly right-handed. Over half reported seizures as their chief complaint. Tumors were mostly low-grade gliomas. Positive mapping of the primary motor cortex was conducted in all cases, with awake surgery completed in 77.2% of cases. New neurological deficits were observed in 26.3% of patients at 1 month after operation; most showed significant improvement at 6 months.

CONCLUSION

The standardized treatment paradigm effectively achieved an optimal onco-functional balance in glioma patients. While some patients experienced neurological deficits postoperatively, the majority recovered to their preoperative baseline within 3 months. The approach prioritizes patient empowerment and customized utilization of functional mapping techniques, considering the challenge of preserving diverse languages in a multilingual patient population.

Functional characterization of the language network of polyglots and hyperpolyglots with precision fMRI

How do polyglots-individuals who speak five or more languages-process their languages, and what can this population tell us about the language system? Using fMRI, we identified the language network in each of 34 polyglots (including 16 hyperpolyglots with knowledge of 10+ languages) and examined its response to the native language, non-native languages of varying proficiency, and unfamiliar languages. All language conditions engaged all areas of the language network relative to a control condition. Languages that participants rated as higher proficiency elicited stronger responses, except for the native language, which elicited a similar or lower response than a non-native language of similar proficiency. Furthermore, unfamiliar languages that were typologically related to the participants' high-to-moderate-proficiency languages elicited a stronger response than unfamiliar unrelated languages. The results suggest that the language network's response magnitude scales with the degree of engagement of linguistic computations (e.g. related to lexical access and syntactic-structure building). We also replicated a prior finding of weaker responses to native language in polyglots than non-polyglot bilinguals. These results contribute to our understanding of how multiple languages coexist within a single brain and provide new evidence that the language network responds more strongly to stimuli that more fully engage linguistic computations.

Functional characterization of the language network of polyglots and hyperpolyglots with precision fMRI

How do polyglots-individuals who speak five or more languages-process their languages, and what can this population tell us about the language system? Using fMRI, we identified the language network in each of 34 polyglots (including 16 hyperpolyglots with knowledge of 10+ languages) and examined its response to the native language, non-native languages of varying proficiency, and unfamiliar languages. All language conditions engaged all areas of the language network relative to a control condition. Languages that participants rated as higher-proficiency elicited stronger responses, except for the native language, which elicited a similar or lower response than a non-native language of similar proficiency. Furthermore, unfamiliar languages that were typologically related to the participants' high-to-moderate-proficiency languages elicited a stronger response than unfamiliar unrelated languages. The results suggest that the language network's response magnitude scales with the degree of engagement of linguistic computations (e.g., related to lexical access and syntactic-structure building). We also replicated a prior finding of weaker responses to native language in polyglots than non-polyglot bilinguals. These results contribute to our understanding of how multiple languages co-exist within a single brain and provide new evidence that the language network responds more strongly to stimuli that more fully engage linguistic computations.

Artificial intelligence based multimodal language decoding from brain activity: A review

Decoding brain activity is conducive to the breakthrough of brain-computer interface (BCI) technology. The development of artificial intelligence (AI) continually promotes the progress of brain language decoding technology. Existent research has mainly focused on a single modality and paid insufficient attention to AI methods. Therefore, our objective is to provide an overview of relevant decoding research from the perspective of different modalities and methodologies. The modalities involve text, speech, image, and video, whereas the core method is using AI-built decoders to translate brain signals induced by multimodal stimuli into text or vocal language. The semantic information of brain activity can be successfully decoded into a language at various levels, ranging from words through sentences to discourses. However, the decoding effect is affected by various factors, such as the decoding model, vector representation model, and brain regions. Challenges and future directions are also discussed. The advances in brain language decoding and BCI technology will potentially assist patients with clinical aphasia in regaining the ability to communicate.

Age of Bilingual Onset Shapes the Dynamics of Functional Connectivity and Laterality in the Resting-State

Bilingualism is known to enhance cognitive function and flexibility of the brain. However, it is not clear how bilingual experience affects the time-varying functional network and whether these changes depend on the age of bilingual onset. This study intended to investigate the bilingual-related dynamic functional connectivity (dFC) based on the resting-state functional magnetic resonance images, including 23 early bilinguals (EBs), 30 late bilinguals (LBs), and 31 English monolinguals. The analysis identified two dFC states, and LBs showed more transitions between these states than monolinguals. Moreover, more frequent left-right switches were found in functional laterality in prefrontal, lateral temporal, lateral occipital, and inferior parietal cortices in EBs compared with LB and monolingual cohorts, and the laterality changes in the anterior superior temporal cortex were negatively correlated with L2 proficiency. These findings highlight how the age of L2 acquisition affects cortico-cortical dFC pattern and provide insight into the neural mechanisms of bilingualism.

Cortical Location of Language Function May Differ between Languages While White Matter Pathways Are Similar in Brain Lesion Patients

The neural representation of language can be identified cortically using navigated repetitive transcranial magnetic stimulation and subcortically using the fiber tracking of diffusion tensor imaging. We investigated how cortical locations of language and language-eloquent white matter pathways differ in 40 brain lesion patients speaking various languages. Error rates related to stimulations at single sites in the frontal and parietal lobe differed significantly between Balto-Slavic and Indo-European languages. Error rates related to stimulations at single sites in the temporal lobe differed significantly between bilingual individuals. No differences were found in the white matter language pathway volumes between Balto-Slavic and Indo-European languages nor between bilingual patients. These original and exploratory data indicate that the underlying subcortical structure might be similar across languages, with initially observed differences in the cortical location of language depending on the semantic processing, but these could not be confirmed using detailed statistical analyses pointing at a similar cortical and subcortical network.

Constructed languages are processed by the same brain mechanisms as natural languages

What constitutes a language? Natural languages share some features with other domains: from math, to music, to gesture. However, the brain mechanisms that process linguistic input are highly specialized, showing little or no response to diverse non-linguistic tasks. Here, we examine constructed languages (conlangs) to ask whether they draw on the same neural mechanisms as natural languages, or whether they instead pattern with domains like math and logic. Using individual-subject fMRI analyses, we show that understanding conlangs recruits the same brain areas as natural language comprehension. This result holds for Esperanto (n=19 speakers)- created to resemble natural languages-and fictional conlangs (Klingon (n=10), Na'vi (n=9), High Valyrian (n=3), and Dothraki (n=3)), created to differ from natural languages, and suggests that conlangs and natural languages share critical features and that the notable differences between conlangs and natural language are not consequential for the cognitive and neural mechanisms that they engage.

Neural signatures of second language proficiency in narrative processing

Making sense of speech in a second language relies on multiple abilities. Differences in brain activity related to proficiency in language tasks have often been attributed to processing demands. However, during naturalistic narrative comprehension, listeners at different proficiency levels may form different representations of the same speech. We hypothesized that the intersubject synchronization of these representations could be used to measure second-language proficiency. Using a searchlight-shared response model, we found highly proficient participants showed synchronization in regions similar to those of native speakers, including in the default mode network and the lateral prefrontal cortex. In contrast, participants with low proficiency showed more synchronization in auditory cortex and word-level semantic processing areas in the temporal lobe. Moderate proficiency showed the greatest neural diversity, suggesting lower consistency in the source of this partial proficiency. Based on these synchronization differences, we were able to classify the proficiency level or predict behavioral performance on an independent English test in held-out participants, suggesting the identified neural systems represented proficiency-sensitive information that was generalizable to other individuals. These findings suggest higher second-language proficiency leads to more native-like neural processing of naturalistic language, including in systems beyond the cognitive control network or the core language network.

The depth of semantic processing modulates cross-language pattern similarity in Chinese-English bilinguals

Previous studies have investigated factors related to the degree of cross-language overlap in brain activations in bilinguals/multilinguals. However, it is still unclear whether and how the depth of semantic processing (a critical task-related factor) affects the neural pattern similarity between native and second languages. To address this question, 26 Chinese-English bilinguals were scanned with fMRI while performing a word naming task (i.e., a task with shallow semantic processing) and a semantic judgment task (i.e., a task with deep semantic processing) in both native and second languages. Based on three sets of representational similarity analysis (whole brain, ROI-based, and within-language vs. cross-language semantic representation), we found that select regions in the reading brain network showed higher cross-language pattern similarity and higher cross-language semantic representations during deep semantic processing than during shallow semantic processing. These results suggest that compared to shallow semantic processing, deep semantic processing may lead to greater language-independent processing (i.e., cross-language semantic representation) and cross-language pattern similarity, and provide direct quantitative neuroimaging evidence for cognitive models of bilingual lexical memory.

Simulating the situated-self drives hippocampo-cortical engagement during inner narration of events

We often use inner narration when thinking about past and future events. The present paradigm explicitly addresses the influence of the language used in inner narration on the hippocampus-dependent event construction process. We assessed the language context effect during the inner narration of different event types: past, future, daydream, and self-unrelated fictitious events. The language context was assessed via a fluent bilingual population who used inner narration, either in their first language (L1) or second language (L2). Not all inner narration of events elicited hippocampo-cortical activity. In fact, only the angular gyrus and precuneus-retrosplenial cortex were activated by inner narration across all event types. More precisely, only inner narration of events which entailed the simulation of bodily self-location in space (whether or not they were time-marked: past, future, daydream) depended on the hippocampo-cortical system, while inner narration of events that did not entail bodily self-location (self-unrelated fictitious) did not. The language context of the narration influenced the bilinguals' hippocampo-cortical system by enhancing the co-activation of semantic areas with the hippocampus for inner narration of events in the L2. Overall, this study highlights 2 important characteristics of hippocampo-cortical-dependent inner narration of events: The core episodic hippocampal system is activated for inner narration of events simulating self-location in space (regardless of time-marking), and the inner language used for narration (L1 or L2) mediates hippocampal functional connectivity.

Intraoperative Brain Mapping in Multilingual Patients: What Do We Know and Where Are We Going?

In this review, we evaluate the knowledge gained so far about the neural bases of multilingual language processing obtained mainly through imaging and electrical stimulation mapping (ESM). We attempt to answer some key questions about multilingualism in the light of recent literature evidence, such as the degree of anatomical–functional integration of two or more languages in a multilingual brain, how the age of L2-acquisition affects language organization in the human brain, or how the brain controls more than one language. Finally, we highlight the future trends in multilingual language mapping.

Bilingual Brains Learn to Use L2 Alliterations Covertly like Poets: Brain ERP Evidence

Bilinguals were documented to access their native or first language (L1) during comprehension of their second languages (L2). However, it is uncertain whether they can access L2 when reading their first language. This study used the event-related potential (ERP) technique to demonstrate the implicit and unconscious access to English words when Chinese–English bilinguals read words in Chinese, their native language. The participants were asked to judge whether the Chinese words presented in pairs were semantically related or not, meanwhile unconscious of the occasional alliteration (repetition of the first phoneme) if the Chinese words were translated into English. While the concealed prime in English translations failed to affect the reaction time, the alliteration significantly modulated N400 among advanced English learners, especially for semantically unrelated word pairs. Critically, this modulation effect was discrepant between bilinguals with high-level and normal-level English proficiency. These results indicate that L2 activation is an unconscious correlate of native-language processing depending on L2 proficiency.

The cortical distribution of first and second language in the right hemisphere of bilinguals - an exploratory study by repetitive navigated transcranial magnetic stimulation

First language (L1) and second language (L2) processing in bilinguals is not yet fully understood, especially not when considering the non-dominant hemisphere. Ten healthy, right-handed volunteers underwent language mapping of the right hemisphere by repetitive navigated transcranial magnetic stimulation and an object-naming task in their L1 and L2. All elicited naming errors together, no responses, and all errors without hesitation were analyzed separately for cortical distributions of error rates (ERs: number of errors divided by the number of applied stimulations). No significant differences (p > 0.05) were found in ERs between the L1 and L2 for all errors (L1 20.6 ± 14.8%, L2 15.4 ± 11.2%), no responses (L1 13.5 ± 10.9%, L2 9.2 ± 10.8%), and all errors without hesitation (L1 14.4 ± 11.2%, L2 10.8 ± 10.0%). The areas that showed high ERs for the L1 included the dorsal precentral and middle precentral gyrus, whereas the triangular inferior frontal gyrus showed high ERs for the L2. When focusing on error distributions per single stimulation points, differences in ERs between the L1 and L2 were initially observed for stimulation within the angular and middle middle frontal gyrus, but did not withstand correction for the false discovery rate (FDR-corrected p > 0.05). In conclusion, this exploratory study shows the feasibility of rTMS to the right hemisphere for language mapping and reveals cortical areas involved in L1 and L2 processing, but has to be followed up by larger studies enrolling more homogeneous cohorts.

Epilepsy and Bilingualism. A Systematic Review

Background: In patients with epilepsy, language abilities and neural language organization have been primarily investigated for the patient's mother tongue. However, in clinical practice, many patients use more than one language or use their second language more than their mother tongue. Yet, information about the linguistic profiles and brain organization of both languages in bilingual epilepsy patients is scarce. The purpose of this study was thus to systematically review the literature on language localization and language abilities in bilingual patients with epilepsy. Methods: An extensive literature search was performed using various electronic databases, including Embase and Medline. Key aspects of inclusion criteria were the assessment of language abilities and/or the investigation of neural language mapping in bilingual patients with epilepsy. Results: Our search strategy yielded 155 articles on language in bilingual epilepsy patients. Of these, 12 met final eligibility criteria. The majority of included articles focused on brain mapping of language using fMRI, Wada-test, or electrocortical stimulation in bilingual epilepsy patients, five studies investigated interictal language abilities in this patient group. Study results showed a pronounced heterogeneity of language abilities in bilingual patients, varying from intact language profiles to impairment in several language functions in both languages. However, the mother tongue was most often better perserved than the second language. Furthermore, studies on brain mapping of both languages again revealed heterogeneous findings ranging from identical brain regions for both languages to overlapping, but more distributed cortical areas for the non-native language. Conclusions: This review underlines the need to evaluate linguistic abilities in both languages, as well as the necessity to preoperatively map both languages in bilingual epilepsy patients. In contrast to the large scientific interest in language abilities and language localization in monolingual epilepsy patients, this review shows that in bilingual patients, the examination of language functions and the identification of brain regions associated with both languages so far played a minor role in epilepsy research. Our review thus emphasizes the need of future research activities in this field.

Semantic Processing in Bilingual Aphasia: Evidence of Language Dependency

Individuals with aphasia frequently show lexical retrieval deficits due to increased interference of semantically related competitors, a phenomenon that can be observed in tasks such as naming pictures grouped by semantic category. These deficits are explained in terms of impaired semantic control, a set of abilities that are to some extent dependent upon executive control (EC). However, the extent to which semantic control abilities can be affected in a second and non-dominant language has not been extensively explored. Additionally, findings in healthy individuals are inconclusive regarding the degree to which semantic processing is shared between languages. In this study, we explored the effect of brain damage on semantic processing by comparing the performance of bilingual individuals with aphasia on tasks involving semantic control during word production and comprehension. Furthermore, we explored whether semantic deficits are related to domain-general EC deficits. First, we investigated the naming performance of Catalan-Spanish bilinguals with fluent aphasia and age-matched healthy controls on a semantically blocked cyclic naming task in each of their two languages (Catalan and Spanish). This task measured semantic interference in terms of the difference in naming latencies between pictures grouped by the same semantic category or different categories. Second, we explored whether lexical deficits extend to comprehension by testing participants in a word-picture matching task during a mixed language condition. Third, we used a conflict monitoring task to explore the presence of EC deficits in patients with aphasia. We found two main results. First, in both language tasks, bilingual patients' performances were more affected than those of healthy controls when they performed the task in their non-dominant language. Second, there was a significant correlation between the speed of processing on the EC task and the magnitude of the semantic interference effect exclusively in the non-dominant language. Taken together, these results suggest that lexical retrieval may be selectively impaired in bilinguals within those conditions where semantic competition is higher, i.e.,- in their non-dominant language; this could possibly be explained by an excessive amount of inhibition placed upon this language. Moreover, lexico-semantic impairments seem to be at least somewhat related to conflict monitoring deficits, suggesting a certain degree of overlap between EC and semantic control.

Lexical learning in a new language leads to neural pattern similarity with word reading in native language

Previous neuroimaging studies have suggested similar neural activations for word reading in native and second languages. However, such similarities were qualitatively determined (i.e., overlapping activation based on traditional univariate activation analysis). In this study, using representational similarity analysis and an artificial language training paradigm, we quantitatively computed cross-language neural pattern similarity to examine the modulatory effect of proficiency in the new language. Twenty-four native Chinese speakers were trained to learn 30 words in a logographic artificial language for 12 days and scanned while performing a semantic decision task after 4-day training and after 12-day training. Results showed that higher proficiency in the new language was associated with higher cross-language pattern similarity in select regions of the reading network.

"Neural overlap of L1 and L2 semantic representations across visual and auditory modalities: a decoding approach"

This study investigated whether brain activity in Dutch-French bilinguals during semantic access to concepts from one language could be used to predict neural activation during access to the same concepts from another language, in different language modalities/tasks. This was tested using multi-voxel pattern analysis (MVPA), within and across language comprehension (word listening and word reading) and production (picture naming). It was possible to identify the picture or word named, read or heard in one language (e.g. maan, meaning moon) based on the brain activity in a distributed bilateral brain network while, respectively, naming, reading or listening to the picture or word in the other language (e.g. lune). The brain regions identified differed across tasks. During picture naming, brain activation in the occipital and temporal regions allowed concepts to be predicted across languages. During word listening and word reading, across-language predictions were observed in the rolandic operculum and several motor-related areas (pre- and postcentral, the cerebellum). In addition, across-language predictions during reading were identified in regions typically associated with semantic processing (left inferior frontal, middle temporal cortex, right cerebellum and precuneus) and visual processing (inferior and middle occipital regions and calcarine sulcus). Furthermore, across modalities and languages, the left lingual gyrus showed semantic overlap across production and word reading. These findings support the idea of at least partially language- and modality-independent semantic neural representations.

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Evidence for at least partially language- and modality-independent semantic neural representations.

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With a decoding approach, we tested whether brain activity during the semantic access of individual nouns in one language and modality (e.g. production) allowed predicting the semantic access of the same concepts in the other language and modalities (e.g. word listening, word reading).

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Across modalities and languages, the left lingual gyrus showed semantic overlap across production and word reading.

Distinct distributed patterns of neural activity are associated with two languages in the bilingual brain

A large body of previous neuroimaging studies suggests that multiple languages are processed and organized in a single neuroanatomical system in the bilingual brain, although differential activation may be seen in some studies because of different proficiency levels and/or age of acquisition of the two languages. However, one important possibility is that the two languages may involve interleaved but functionally independent neural populations within a given cortical region, and thus, distinct patterns of neural computations may be pivotal for the processing of the two languages. Using functional magnetic resonance imaging (fMRI) and multivariate pattern analyses, we tested this possibility in Chinese-English bilinguals when they performed an implicit reading task. We found a broad network of regions wherein the two languages evoked different patterns of activity, with only partially overlapping patterns of voxels in a given region. These regions, including the middle occipital cortices, fusiform gyri, and lateral temporal, temporoparietal, and prefrontal cortices, are associated with multiple aspects of language processing. The results suggest the functional independence of neural computations underlying the representations of different languages in bilinguals.

Identifying cortical first and second language sites via navigated transcranial magnetic stimulation of the left hemisphere in bilinguals

The cortical areas that code for the first (L1) and second language (L2) in bilinguals have still not been sufficiently explored. Thus, this study investigated the left-hemispheric distribution of the L1 and L2 using repetitive navigated transcranial magnetic stimulation (rTMS), in combination with an object-naming task, in 10 healthy, right-handed volunteers. In particular, higher error rates (ERs) were observed in the L1, and there was a statistically significant difference between the ERs of L1 and L2 for no-response errors (L1 mean 11.9±9.0%, L2 mean 6.5±5.2%; p=0.03). Furthermore, language-specific and shared cortical distribution patterns for the L1 and L2 were observed within the frontal, parietal, and temporal lobes with a trend towards higher occurrence of language-specific spots within posterior regions. Overall, the L1 presented a more stable pattern of language distribution compared to the L2.

Language control in bilingual adults with and without history of mild traumatic brain injury

Adults with a history of traumatic brain injury often show deficits in executive functioning (EF), including the ability to inhibit, switch, and attend to tasks. These abilities are critical for language processing in bilinguals. This study examined the effect of mild traumatic brain injury (mTBI) on EF and language processing in bilinguals using behavioral and eye-tracking measures. Twenty-two bilinguals with a history of mTBI and twenty healthy control bilinguals were administered executive function and language processing tasks. Bilinguals with a history of mTBI showed deficits in specific EFs and had higher rates of language processing errors than healthy control bilinguals. Additionally, individuals with a history of mTBI have different patterns of eye movements during reading than healthy control bilinguals. These data suggest that language processing deficits are related to underlying EF abilities. The findings provide important information regarding specific EF and language control deficits in bilinguals with a history mTBI.

Cross-cultural consistency and diversity in intrinsic functional organization of Broca's Region

As a core language area, Broca's region was consistently activated in a variety of language studies even across different language systems. Moreover, a high degree of structural and functional heterogeneity in Broca's region has been reported in many studies. This raised the issue of how the intrinsic organization of Broca's region effects by different language experiences in light of its subdivisions. To address this question, we used multi-center resting-state fMRI data to explore the cross-cultural consistency and diversity of Broca's region in terms of its subdivisions, connectivity patterns and modularity organization in Chinese and German speakers. A consistent topological organization of the 13 subdivisions within the extended Broca's region was revealed on the basis of a new in-vivo parcellation map, which corresponded well to the previously reported receptorarchitectonic map. Based on this parcellation map, consistent functional connectivity patterns and modularity organization of these subdivisions were found. Some cultural difference in the functional connectivity patterns was also found, for instance stronger connectivity in Chinese subjects between area 6v2 and the motor hand area, as well as higher correlations between area 45p and middle frontal gyrus. Our study suggests that a generally invariant organization of Broca's region, together with certain regulations of different language experiences on functional connectivity, might exists to support language processing in human brain.

L1 and L2 processing in the bilingual brain: A meta-analysis of neuroimaging studies

Neuroimaging studies investigating bilingual processes have produced controversial results in determining similarities versus differences between L1 and L2 neural networks. The current meta-analytic study was conducted to examine what factors play a role in the similarities and differences between L1 and L2 networks with a focus on age of acquisition (AOA) and whether the orthographic transparency of L2 is more or less transparent than that of L1. Using activation likelihood estimation (ALE), we found L2 processing involved more additional regions than L1 for late bilinguals in comparison to early bilinguals, suggesting L2 processing is more demanding in late bilinguals. We also provide direct evidence that AOA of L2 influences L1 processing through the findings that early bilinguals had greater activation in the left fusiform gyrus than late bilinguals during L1 processing even when L1 languages were the same in the two groups, presumably due to greater co-activation of orthography in L1 and L2 in early bilinguals. In addition, we found that the same L2 languages evoked different brain activation patterns depending on whether it was more or less transparent than L1 in orthographic transparency. The bilateral auditory cortex and right precentral gyrus were more involved in shallower-than-L1 L2s, suggesting a "sound-out" strategy for a more regular language by involving the phonological regions and sensorimotor regions to a greater degree. In contrast, the left frontal cortex was more involved in the processing of deeper-than-L1 L2s, presumably due to the increased arbitrariness of mapping between orthography and phonology in L2.

Distinct activated cortical areas and volumes in Uygur-Chinese bilinguals

Objective

The aim of this study is to evaluate variations in cortical activation in early and late Uygur-Chinese bilinguals from the Xinjiang Uygur Autonomous Region of China. Methodology: During a semantic judgment task with visual stimulation by a single Chinese or Uygur word, functional magnetic resonance imaging (fMRI) was performed. The fMRI data regarding activated cortical areas and volumes by both languages were analyzed.

Results

The first language (L1) and second language (L2) activated language-related hemispheric regions, including the left inferior frontal and parietal cortices, and L1 specifically activated the left middle temporal gyrus. For both L1 and L2, cortical activation was greater in the left hemisphere, and there was no significant difference in the lateralization index (LI) between the two languages (p > 0.05). Although the total activated cortical areas were larger in early than late bilinguals, the activation volumes were not significantly different.

Conclusion

Activated brains areas in early and late fluent bilinguals largely overlapped. However, these areas were more scattered upon presentation of L2 than L1, and L1 had a more specific pattern of activation than L2. For both languages, the left hemisphere was dominant. We found that L2 proficiency level rather than age of acquisition had a greater influence on which brain areas were activated with semantic processing.

Simultaneous perception of a spoken and a signed language: The brain basis of ASL-English code-blends

Code-blends (simultaneous words and signs) are a unique characteristic of bimodal bilingual communication. Using fMRI, we investigated code-blend comprehension in hearing native ASL-English bilinguals who made a semantic decision (edible?) about signs, audiovisual words, and semantically equivalent code-blends. English and ASL recruited a similar fronto-temporal network with expected modality differences: stronger activation for English in auditory regions of bilateral superior temporal cortex, and stronger activation for ASL in bilateral occipitotemporal visual regions and left parietal cortex. Code-blend comprehension elicited activity in a combination of these regions, and no cognitive control regions were additionally recruited. Furthermore, code-blends elicited reduced activation relative to ASL presented alone in bilateral prefrontal and visual extrastriate cortices, and relative to English alone in auditory association cortex. Consistent with behavioral facilitation observed during semantic decisions, the findings suggest that redundant semantic content induces more efficient neural processing in language and sensory regions during bimodal language integration.

Learning to read words in a new language shapes the neural organization of the prior languages

Learning a new language entails interactions with one׳s prior language(s). Much research has shown how native language affects the cognitive and neural mechanisms of a new language, but little is known about whether and how learning a new language shapes the neural mechanisms of prior language(s). In two experiments in the current study, we used an artificial language training paradigm in combination with an fMRI to examine (1) the effects of different linguistic components (phonology and semantics) of a new language on the neural process of prior languages (i.e., native and second languages), and (2) whether such effects were modulated by the proficiency level in the new language. Results of Experiment 1 showed that when the training in a new language involved semantics (as opposed to only visual forms and phonology), neural activity during word reading in the native language (Chinese) was reduced in several reading-related regions, including the left pars opercularis, pars triangularis, bilateral inferior temporal gyrus, fusiform gyrus, and inferior occipital gyrus. Results of Experiment 2 replicated the results of Experiment 1 and further found that semantic training also affected neural activity during word reading in the subjects׳ second language (English). Furthermore, we found that the effects of the new language were modulated by the subjects׳ proficiency level in the new language. These results provide critical imaging evidence for the influence of learning to read words in a new language on word reading in native and second languages.

Language exposure induced neuroplasticity in the bilingual brain: a follow-up fMRI study

Although several studies have shown that language exposure crucially influence the cerebral representation of bilinguals, the effects of short-term change of language exposure in daily life upon language control areas in bilinguals are less known. To explore this issue, we employed follow-up fMRI to investigate whether differential exposure induces neuroplastic changes in the language control network in high-proficient Cantonese (L1)-Mandarin (L2) early bilinguals. The same 10 subjects underwent twice BOLD-fMRI scans while performing a silent narration task which corresponded to two different language exposure conditions, CON-1 (L1/L2 usage percentage, 50%:50%) and CON-2 (L1/L2 usage percentage, 90%:10%). We report a strong effect of language exposure in areas related to language control for the less exposed language. Interestingly, these significant effects were present after only a 30-day period of differential language exposure. In detail, we reached the following results: (1) the interaction effect of language and language exposure condition was found significantly in the left pars opercularis (BA 44) and marginally in the left MFG (BA 9); (2) in CON-2, increases of activation values in L2 were found significantly in bilateral BA 46 and BA 9, in the left BA44, and marginally in the left caudate; and (3) in CON-2, we found a significant negative correlation between language exposure to L2 and the BOLD activation value specifically in the left ACC. These findings strongly support the hypothesis that even short periods of differential exposure to a given language may induce significant neuroplastic changes in areas responsible for language control. The language which a bilingual is less exposed to and is also less used will be in need of increased mental control as shown by the increased activity of language control areas.

Speech motor brain regions are differentially recruited during perception of native and foreign-accented phonemes for first and second language listeners

Brain imaging studies indicate that speech motor areas are recruited for auditory speech perception, especially when intelligibility is low due to environmental noise or when speech is accented. The purpose of the present study was to determine the relative contribution of brain regions to the processing of speech containing phonetic categories from one's own language, speech with accented samples of one's native phonetic categories, and speech with unfamiliar phonetic categories. To that end, native English and Japanese speakers identified the speech sounds /r/ and /l/ that were produced by native English speakers (unaccented) and Japanese speakers (foreign-accented) while functional magnetic resonance imaging measured their brain activity. For native English speakers, the Japanese accented speech was more difficult to categorize than the unaccented English speech. In contrast, Japanese speakers have difficulty distinguishing between /r/ and /l/, so both the Japanese accented and English unaccented speech were difficult to categorize. Brain regions involved with listening to foreign-accented productions of a first language included primarily the right cerebellum, left ventral inferior premotor cortex PMvi, and Broca's area. Brain regions most involved with listening to a second-language phonetic contrast (foreign-accented and unaccented productions) also included the left PMvi and the right cerebellum. Additionally, increased activity was observed in the right PMvi, the left and right ventral superior premotor cortex PMvs, and the left cerebellum. These results support a role for speech motor regions during the perception of foreign-accented native speech and for perception of difficult second-language phonetic contrasts.

Awake surgery between art and science. Part II: language and cognitive mapping

Direct cortical and subcortical stimulation has been claimed to be the gold standard for exploring brain function. In this field, efforts are now being made to move from intraoperative naming-assisted surgical resection towards the use of other language and cognitive tasks. However, before relying on new protocols and new techniques, we need a multi-staged system of evidence (low and high) relating to each step of functional mapping and its clinical validity. In this article we examine the possibilities and limits of brain mapping with the aid of a visual object naming task and various other tasks used to date. The methodological aspects of intraoperative brain mapping, as well as the clinical and operative settings, were discussed in Part I of this review.

The role of domain-general cognitive control in language comprehension

What role does domain-general cognitive control play in understanding linguistic input? Although much evidence has suggested that domain-general cognitive control and working memory resources are sometimes recruited during language comprehension, many aspects of this relationship remain elusive. For example, how frequently do cognitive control mechanisms get engaged when we understand language? And is this engagement necessary for successful comprehension? I here (a) review recent brain imaging evidence for the neural separability of the brain regions that support high-level linguistic processing vs. those that support domain-general cognitive control abilities; (b) define the space of possibilities for the relationship between these sets of brain regions; and (c) review the available evidence that constrains these possibilities to some extent. I argue that we should stop asking whether domain-general cognitive control mechanisms play a role in language comprehension, and instead focus on characterizing the division of labor between the cognitive control brain regions and the more functionally specialized language regions.

Neurocognitive determinants of performance variability among world-language users

Although the notion of world language has been variously defined, most accounts acknowledge inter-user performance variability as a key aspect of the construct. The sociocultural aspects of such a phenomenon have been extensively treated in the literature. However, comparatively little attention has been paid to its neurocognitive underpinnings. This paper addresses the biopsychological bases of performance variability among word-language users, focusing on bilingual speakers of English. Available evidence reveals four neurocognitive determinants of variability, namely manner of appropriation, age of acquisition, level of proficiency, and degree of formal similarity between the native and the non-native language. In its concluding section, the paper highlights the benefits of incorporating neurocognitive evidence into the study and conceptualization of world languages.

Cognitive control for language switching in bilinguals: A quantitative meta-analysis of functional neuroimaging studies

In a quantitative meta-analysis, using the activation likelihood estimation method, we examined the neural regions involved in bilingual cognitive control, particularly when engaging in switching between languages. The purpose of this study was to evaluate the bilingual cognitive control model based on a qualitative analysis [Abutalebi, J., & Green, D. W. (2008). Control mechanisms in bilingual language production: Neural evidence from language switching studies. Language and Cognitive Processes, 23, 557-582.]. After reviewing 128 peer-reviewed articles, ten neuroimaging studies met our inclusion criteria and in each study, bilinguals switched between languages in response to cues. We isolated regions involved in voluntary language switching, by including reported contrasts between the switching conditions and high level baseline conditions involving similar tasks but requiring the use of only one language. Eight brain regions showed significant and reliable activation: left inferior frontal gyrus, left middle temporal gyrus, left middle frontal gyrus, right precentral gyrus, right superior temporal gyrus, midline pre-SMA and bilateral caudate nuclei. This quantitative result is consistent with bilingual aphasia studies that report switching deficits associated with lesions to the caudate nuclei or prefrontal cortex. It also extends the previously reported qualitative model. We discuss the implications of the findings for accounts of bilingual cognitive control.

The neural processing of second language comprehension modulated by the degree of proficiency: a listening connected speech FMRI study

While the neural network encompassing the processing of the mother tongue (L1) is well defined and has revealed the existence of a bilateral ventral pathway and a left dorsal pathway in which 3 loops have been defined, the question of the processing of a second language (L2) is still a matter of debate. Among variables accounting for the discrepancies in results, the degree of L2 proficiency appears to be one of the main factors. The present study aimed at assessing both pathways in L2, making it possible to determine the degree of mastery of the different speech components (prosody, phonology, semantics and syntax) that are intrinsically embedded within connected speech and that vary according to the degree of proficiency using high degrees of prosodic information. Two groups of high and moderate proficiency in L2 performed an fMRI comprehension task in L1 and L2. The modifications in brain activity observed within the dorsal and the ventral pathways according to L2 proficiency suggest that different processes of L2 are supported by differences in the integrated activity within distributed networks that included the left STSp, the left Spt and the left pars triangularis.

Once is Enough: N400 Indexes Semantic Integration of Novel Word Meanings from a Single Exposure in Context

We investigated the impact of contextual constraint on the integration of novel word meanings into semantic memory. Adults read strongly or weakly constraining sentences ending in known or unknown (novel) words as scalp-recorded electrical brain activity was recorded. Word knowledge was assessed via a lexical decision task in which recently seen known and unknown word sentence endings served as primes for semantically related, unrelated, and synonym/identical target words. As expected, N400 amplitudes to target words preceded by known word primes were reduced by prime-target relatedness. Critically, N400 amplitudes to targets preceded by novel primes also varied with prime-target relatedness, but only when they had initially appeared in highly constraining sentences. This demonstrates for the first time that fast-mapped word representations can develop strong associations with semantically related word meanings and reveals a rapid neural process that can integrate information about word meanings into the mental lexicon of young adults.

Spatiotemporal distribution of cortical processing of first and second languages in bilinguals. I. Effects of proficiency and linguistic setting

The study determined how spatiotemporal distribution of cortical activity to words in first and second language is affected by language, proficiency, and linguistic setting. Ten early bilinguals and 14 late adult bilinguals listened to pairs of words presented in Arabic (L1), Hebrew (L2), or in mixed pairs and indicated whether both words had the same meaning or not. Source current densities of event-related potentials were estimated. Activity to first words in the pair lateralized to right hemisphere, higher to L1 than L2 during early processing (<300 ms) among both groups but only among late bilinguals during late processing (>300 ms). During early and late processing, activities were larger in mixed than monolinguistic settings among early bilinguals but lower in mixed than in monolinguistic settings among late bilinguals. Late processing in auditory regions was of larger magnitude in left than right hemispheres among both groups. Activity to second words in the pair was larger in mixed than in monolinguistic settings during both early and late processing among both groups. Early processing of second words in auditory regions lateralized to the right among early bilinguals and to the left among late bilinguals, whereas late processing did not differ between groups. Wernicke's area activity during late processing of L2 was larger on the right, while on the left no significant differences between languages were found. The results show that cortical language processing in bilinguals differs between early and late processing and these differences are modulated by linguistic proficiency and setting.

Second language experience modulates functional brain network for the native language production in bimodal bilinguals

The functional brain network of a bilingual's first language (L1) plays a crucial role in shaping that of his or her second language (L2). However, it is less clear how L2 acquisition changes the functional network of L1 processing in bilinguals. In this study, we demonstrate that in bimodal (Chinese spoken-sign) bilinguals, the functional network supporting L1 production (spoken language) has been reorganized to accommodate the network underlying L2 production (sign language). Using functional magnetic resonance imaging (fMRI) and a picture naming task, we find greater recruitment of the right supramarginal gyrus (RSMG), the right temporal gyrus (RSTG), and the right superior occipital gyrus (RSOG) for bilingual speakers versus monolingual speakers during L1 production. In addition, our second experiment reveals that these regions reflect either automatic activation of L2 (RSOG) or extra cognitive coordination (RSMG and RSTG) between both languages during L1 production. The functional connectivity between these regions, as well as between other regions that are L1- or L2-specific, is enhanced during L1 production in bimodal bilinguals as compared to their monolingual peers. These findings suggest that L1 production in bimodal bilinguals involves an interaction between L1 and L2, supporting the claim that learning a second language does, in fact, change the functional brain network of the first language.

Identifying bilingual semantic neural representations across languages

The goal of the study was to identify the neural representation of a noun's meaning in one language based on the neural representation of that same noun in another language. Machine learning methods were used to train classifiers to identify which individual noun bilingual participants were thinking about in one language based solely on their brain activation in the other language. The study shows reliable (p<.05) pattern-based classification accuracies for the classification of brain activity for nouns across languages. It also shows that the stable voxels used to classify the brain activation were located in areas associated with encoding information about semantic dimensions of the words in the study. The identification of the semantic trace of individual nouns from the pattern of cortical activity demonstrates the existence of a multi-voxel pattern of activation across the cortex for a single noun common to both languages in bilinguals.

Language lateralisation in late proficient bilinguals: a lexical decision fMRI study

Approximately half the world's population can now speak more than one language. Understanding the neural basis of language organisation in bilinguals, and whether the cortical networks involved during language processing differ from that of monolinguals, is therefore an important area of research. A main issue concerns whether L2 (second language) is processed using the same neural mechanisms that mediate L1 (first language) processing. Moderating factors include the age of L2 acquisition and the level of proficiency. Here we used a lexical decision task with five conditions during functional magnetic resonance imaging (fMRI) to investigate language processing in eight late proficient bilinguals when using Macedonian (L1) and English (L2). Bilinguals had greater bilateral activation during both L1 and L2 processing, and therefore weaker language lateralisation, compared to matched control English monolinguals. A greater amount of overall activation was also seen in bilinguals, especially during L2 conditions. Late proficient bilinguals living in their L2 environment employ a more extensive neural network than monolinguals when processing their second language.

Brain activity in bilingual developmental dyslexia: an fMRI study

The aim of this study was to identify the neural substrates of an adult English-German bilingual with dyslexia (in both languages) during lexical decision-making using functional magnetic resonance imaging (fMRI). A lexical decision task with five conditions in a block design was employed (nonverbal shape judgment, lettercase judgment, regular word judgment, irregular word judgment, and nonword judgment), and the activation was compared to a non-dyslexic control bilingual and a control monolingual participant. Both of the control participants matched the dyslexic bilingual BK on age, sex, IQ, handedness, and education level. Results indicated that the bilingual adult with dyslexia was strongly right lateralized for stimuli that required phonological processing, a profile that differed particularly from the activation observed from the monolingual participant. These results are consistent with the idea of increased activation (mostly in the right hemisphere) during linguistic tasks in adults with dyslexia and in late proficient bilinguals relative to monolinguals. Findings also suggest that the additional activation observed in both of the bilinguals are similar, suggesting that these effects are not additive in the dyslexic bilingual.

A comparison of sensory-motor activity during speech in first and second languages

A foreign language (L2) learned after childhood results in an accent. This functional neuroimaging study investigated speech in L2 as a sensory-motor skill. The hypothesis was that there would be an altered response in auditory and somatosensory association cortex, specifically the planum temporale and parietal operculum, respectively, when speaking in L2 relative to L1, independent of rate of speaking. These regions were selected for three reasons. First, an influential computational model proposes that these cortices integrate predictive feedforward and postarticulatory sensory feedback signals during articulation. Second, these adjacent regions (known as Spt) have been identified as a "sensory-motor interface" for speech production. Third, probabilistic anatomical atlases exist for these regions, to ensure the analyses are confined to sensory-motor differences between L2 and L1. The study used functional magnetic resonance imaging (fMRI), and participants produced connected overt speech. The first hypothesis was that there would be greater activity in the planum temporale and the parietal operculum when subjects spoke in L2 compared with L1, one interpretation being that there is less efficient postarticulatory sensory monitoring when speaking in the less familiar L2. The second hypothesis was that this effect would be observed in both cerebral hemispheres. Although Spt is considered to be left-lateralized, this is based on studies of covert speech, whereas overt speech is accompanied by sensory feedback to bilateral auditory and somatosensory cortices. Both hypotheses were confirmed by the results. These findings provide the basis for future investigations of sensory-motor aspects of language learning using serial fMRI studies.

Neural basis of single-word reading in Spanish-English bilinguals

Brain imaging studies have identified a left-lateralized network of regions that are engaged when monolinguals read. However, for individuals who are native speakers of two languages, it is unclear whether this pattern of activity is maintained across both languages or if it deviates according to language-specific properties. We used functional magnetic resonance imaging to investigate single-word processing in Spanish and in English in 12 proficient early Spanish-English bilinguals matched in skill level in both languages. Word processing in Spanish engaged the left inferior frontal and left middle temporal gyri. Word processing in English activated the left inferior frontal, middle frontal, and fusiform gyri extending to inferior temporal gyrus and the right middle temporal gyrus extending into superior temporal sulcus. The comparison of reading in Spanish greater than reading in English revealed involvement of the left middle temporal gyrus extending into the superior temporal sulcus. English greater than Spanish, however, demonstrated greater engagement of the left middle frontal gyrus extending into the superior frontal gyrus. We conclude that although word processing in either language activates classical areas associated with reading, there are language-specific differences, which can be attributed to the disparity in orthographic transparency. English, an orthographically deep language, may require greater engagement of the frontal regions for phonological coding, whereas Spanish allows increased access to semantic processing via the left middle temporal areas. Together, these results suggest that bilinguals will show adjustments to the typical neural representation of reading as necessitated by the demands of the orthography.

Activity levels in the left hemisphere caudate-fusiform circuit predict how well a second language will be learned

How second language (L2) learning is achieved in the human brain remains one of the fundamental questions of neuroscience and linguistics. Previous neuroimaging studies with bilinguals have consistently shown overlapping cortical organization of the native language (L1) and L2, leading to a prediction that a common neurobiological marker may be responsible for the development of the two languages. Here, by using functional MRI, we show that later skills to read in L2 are predicted by the activity level of the fusiform-caudate circuit in the left hemisphere, which nonetheless is not predictive of the ability to read in the native language. We scanned 10-y-old children while they performed a lexical decision task on L2 (and L1) stimuli. The subjects' written language (reading) skills were behaviorally assessed twice, the first time just before we performed the fMRI scan (time 1 reading) and the second time 1 y later (time 2 reading). A whole-brain based analysis revealed that activity levels in left caudate and left fusiform gyrus correlated with L2 literacy skills at time 1. After controlling for the effects of time 1 reading and nonverbal IQ, or the effect of in-scanner lexical performance, the development in L2 literacy skills (time 2 reading) was also predicted by activity in left caudate and fusiform regions that are thought to mediate language control functions and resolve competition arising from L1 during L2 learning. Our findings suggest that the activity level of left caudate and fusiform regions serves as an important neurobiological marker for predicting accomplishment in reading skills in a new language.