Selective deficit of one language in a bilingual patient following surgery in the left perisylvian area

Intersecting distributed networks support convergent linguistic functioning across different languages in bilinguals

How bilingual brains accomplish the processing of more than one language has been widely investigated by neuroimaging studies. The assimilation-accommodation hypothesis holds that both the same brain neural networks supporting the native language and additional new neural networks are utilized to implement second language processing. However, whether and how this hypothesis applies at the finer-grained levels of both brain anatomical organization and linguistic functions remains unknown. To address this issue, we scanned Chinese-English bilinguals during an implicit reading task involving Chinese words, English words and Chinese pinyin. We observed broad brain cortical regions wherein interdigitated distributed neural populations supported the same cognitive components of different languages. Although spatially separate, regions including the opercular and triangular parts of the inferior frontal gyrus, temporal pole, superior and middle temporal gyrus, precentral gyrus and supplementary motor areas were found to perform the same linguistic functions across languages, indicating regional-level functional assimilation supported by voxel-wise anatomical accommodation. Taken together, the findings not only verify the functional independence of neural representations of different languages, but show co-representation organization of both languages in most language regions, revealing linguistic-feature specific accommodation and assimilation between first and second languages.

Presurgical language mapping in bilingual children using transcranial magnetic stimulation: illustrative case

BACKGROUND

Presurgical mapping of eloquent cortex in young patients undergoing neurosurgery is critical but presents challenges unique to the pediatric population, including motion artifact, noncompliance, and sedation requirements. Furthermore, as bilingualism in children increases, functional mapping of more than one language is becoming increasingly critical. Transcranial magnetic stimulation (TMS), a noninvasive brain stimulation technique, is well suited to evaluate language areas in children since it does not require the patient to remain still during mapping.

OBSERVATIONS

A 13-year-old bilingual male with glioblastoma multiforme involving the left parietal lobe and deep occipital white matter underwent preoperative language mapping using magnetic resonance imaging-guided TMS. Language-specific cortices were successfully identified in both hemispheres. TMS findings aided in discussing with the family the risks of postsurgical deficits of tumor resection; postoperatively, the patient had intact bilingual speech and was referred for chemotherapy and radiation.

LESSONS

The authors’ findings add to the evolving case for preoperative dual language mapping in bilingual neurosurgical candidates. The authors illustrate the feasibility and utility of TMS as a noninvasive functional mapping tool in this child. TMS is safe, effective, and can be used for preoperative mapping of language cortex in bilingual children to aid in surgical planning and discussion with families.

Factors Modifying the Amount of Neuroanatomical Overlap between Languages in Bilinguals-A Systematic Review of Neurosurgical Language Mapping Studies

Neurosurgery on individuals with lesions around language areas becomes even more complicated when the patient is bilingual. It is thus important to understand the principles that predict the likelihood of convergent versus separate neuroanatomical organization of the first (L1) and the second language (L2) in these individuals. We reviewed all English-language publications on neurosurgical language mapping in bilinguals before January 2020 in three databases (e.g., PubMed). Our search yielded 28 studies with 207 participants. The reviewed data suggest several principles of language organization in bilingual neurosurgical patients: (1) separate cortical areas uniquely dedicated to each language in both anterior and posterior language sites are the rule rather than occasional findings, (2) In cases where there was a convergent neuroanatomical representation for L1 and L2, two factors explained the overlap: an early age of L2 acquisition and a small linguistic distance between L1 and L2 and (3) When L1 and L2 diverged neuroanatomically, more L1-specific sites were identified for early age of L2 acquisition, high L2 proficiency and a larger linguistic distance. This work provides initial evidence-based principles predicting the likelihood of converging versus separate neural representations of L1 and L2 in neurosurgical patients.

Clinical Utility of Preoperative Bilingual Language fMRI Mapping in Patients with Brain Tumors

BACKGROUND AND PURPOSE

Previous literature has demonstrated disparity in the postoperative recovery of first and second language function of bilingual neurosurgical patients. However, it is unclear to whether preoperative brain mapping of both languages is needed. In this study, we aimed to evaluate the clinical utility of language task functional MRI (fMRI) implemented in both languages in bilingual patients.

METHODS

We retrospectively examined fMRI data of 13 bilingual brain tumor patients (age: 23 to 59 years) who performed antonym generation task-based fMRIs in English and non-English language. The usefulness of bilingual language mapping was evaluated using a structured survey administered to 5 neurosurgeons. Additionally, quantitative comparison between the brain activation maps of both languages was performed.

RESULTS

Survey responses revealed differences in raters' surgical approach, including asleep versus awake surgery and extent of resection, after viewing the language fMRI maps. Additional non-English fMRI led to changes in surgical decision-making and bettered localization of language areas. Quantitative analysis revealed an increase in laterality index (LI) in non-English fMRI compared to English fMRI. The Dice coefficient demonstrated fair overlap (.458 ± .160) between the activation maps.

CONCLUSION

Bilingual fMRI mapping of bilingual patients allows to better appreciate functionally active language areas that may be neglected in single language mapping. Utility of bilingual mapping was supported by changes in both surgical approach and LI measurements, suggesting its benefit on preoperative language mapping.

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.

Language system organization in a quadrilingual with a brain tumor: Implications for understanding of the language network

In pre-neurosurgery language mapping it is critical to identify language-specific regions in multilingual speakers. We conducted pre-operative functional magnetic resonance imaging, and intraoperative language mapping in the unique case of a highly proficient quadrilingual with a left frontal brain tumor who acquired her second language at age 5, and her third and fourth languages at 15. We found a predominantly different organization in each language with only a few areas shared by all 4 languages. Contrary to existing evidence, impairment across languages was not related to age of acquisition, amount of exposure, or language similarity. This case suggests that the functional structure of the language system may be highly idiosyncratic in multilingual individuals and supports detailed study in this group to inform neurocognitive models of language.

Language processing in bilingual aphasia: a new insight into the problem

There is increasing evidence that a bilingual person should not be considered as two monolinguals in a single body, a view that has gradually been adopted in the diagnosis and treatment of bilingual aphasia. However, its investigation is complicated due to the large variety in possible language combinations, pre- and postmorbid language proficiencies, and age of second language acquisition. Furthermore, the tests and tasks used to assess linguistic capabilities differ in almost every study, hindering a direct comparison of their outcomes. Behavioral, electrophysiological, and neuroimaging data from healthy population show that the processing of second language domains (semantics, syntax, morphology) depends on factors such as age and method of acquisition, proficiency level and environment in which the second language was acquired. A number of single and multiple case reports that rely on behavioral testing of bilingual aphasics replicate these results. Additionally, they show that the patient's performance depends on the size and location of the lesion, as well as language typology and morphological characteristics. Furthermore, the impairment and recovery patterns and recovery generalization from treated to untreated language depend on the lexical and orthographic distances between the two languages. For healthy bilinguals, language processing is usually studied in comparison to monolinguals. We advocate that a good starting point for identifying patterns specific for bilingual aphasia is to compare patient studies of bilinguals and monolinguals.

Diagnostic work up for language testing in patients undergoing awake craniotomy for brain lesions in language areas

Awake craniotomy is the technique of choice in patients with brain tumours adjacent to primary and accessory language areas (Broca's and Wernicke's areas). Language testing should be aimed to detect preoperative deficits, to promptly identify the occurrence of new intraoperative impairments and to establish the course of postoperative language status. Aim of this case series is to describe our experience with a dedicated language testing work up to evaluate patients with or at risk for language disturbances undergoing awake craniotomy for brain tumour resection. Pre- and intra operative testing was accomplished with 8 tests. Intraoperative evaluation was accomplished when patients were fully cooperative (Ramsey < 3). Postoperative evaluation was scheduled at early (within 21 days) and long-term follow-up (3-6 months). Twenty consecutive patients were prospectively recruited. Preoperative language testings were normal in 9 patients (45%), showed mild to moderate language deficit in 8 (40%) and severe language deficit or aphasic disorders in 3 (15%). Broca's area was identified in 15 patients, in all cases by counting arrest during stimulation and in 12 cases by naming arrest. In this article we describe our experience using a language testing work up to evaluate - pre, intra and postoperatively - patients undergoing awake craniotomy for brain tumour resection with preoperative language disturbances or at risk for postoperative language deficits. This approach allows a systematic evaluation and recording of language function status and can be accomplished even when a neuropsychologist or speech therapist are not involved in the operation crew.

Language mapping in multilingual patients: electrocorticography and cortical stimulation during naming

Multilingual patients pose a unique challenge when planning epilepsy surgery near language cortex because the cortical representations of each language may be distinct. These distinctions may not be evident with routine electrocortical stimulation mapping (ESM). Electrocorticography (ECoG) has recently been used to detect task-related spectral perturbations associated with functional brain activation. We hypothesized that using broadband high gamma augmentation (HGA, 60–150 Hz) as an index of cortical activation, ECoG would complement ESM in discriminating the cortical representations of first (L1) and second (L2) languages. We studied four adult patients for whom English was a second language, in whom subdural electrodes (a total of 358) were implanted to guide epilepsy surgery. Patients underwent ECoG recordings and ESM while performing the same visual object naming task in L1 and L2. In three of four patients, ECoG found sites activated during naming in one language but not the other. These language-specific sites were not identified using ESM. In addition, ECoG HGA was observed at more sites during L2 versus L1 naming in two patients, suggesting that L2 processing required additional cortical resources compared to L1 processing in these individuals. Post-operative language deficits were identified in three patients (one in L2 only). These deficits were predicted by ECoG spectral mapping but not by ESM. These results suggest that pre-surgical mapping should include evaluation of all utilized languages to avoid post-operative functional deficits. Finally, this study suggests that ECoG spectral mapping may potentially complement the results of ESM of language.

Language testing during awake "anesthesia" in a bilingual patient with brain lesion adjacent to Wernicke's area

Awake "anesthesia" is the preferable anesthetic approach for neurosurgical procedures that require intraoperative localization of eloquent brain areas. We describe intraoperative inducible selective English aphasia in a bilingual (English and Italian) patient undergoing awake anesthesia for excision of a brain lesion adjacent to Wernicke's area with no postoperative neurological sequelae. We discuss the importance of intraoperative brain mapping and intraoperative language testing in bilingual patients to prevent iatrogenic-related morbidity.

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.

Performance in L1 and L2 observed in Arabic-Hebrew bilingual aphasic following brain tumor: A case constitutes double dissociation

This study aimed to verify the existence of a double first language (L1)/second language (L2) dissociation. In recent work, I described a case study of a Arabic-Hebrew aphasic patient (MH) with disturbances in the two languages, with Hebrew (L2) being more impaired. In this case, an Arabic-Hebrew bilingual patient (MM) with a similar cultural background who suffered brain damage following a left hemisphere tumor (oligodendroglioma) and craniotomy is reported. The same materials were used, which overcame methodological constraints in our previous work. The results revealed a complementary pattern of severe impairment of L1 (Arabic), while MM had mild language disorder in L2 (Hebrew) with intact semantic knowledge in both languages. These two cases demonstrate a double L1/L2 dissociation in unique languages, and support the notion that bilingual persons could have distinct cortical language areas.

Cortical activation during word processing in late bilinguals: Similarities and differences as revealed by functional magnetic resonance imaging

Functional magnetic resonance imaging was used to compare cortical organization of the first (L1, Russian) and second (L2, English) languages. Six fluent Russian-English bilinguals who acquired their second language postpuberty were tested with words and nonwords presented either auditorily or visually. Results showed that both languages activated similar cortical networks, including the inferior frontal, middle frontal, superior temporal, middle temporal, angular, and supramarginal gyri. Within the inferior frontal gyrus (IFG), L2 activated a larger cortical volume than L1 during lexical and phonological processing. For both languages, the left IFG was more active than the right IFG during lexical processing. Within the left IFG, the distance between centers of activation associated with lexical processing of translation equivalents across languages was larger than the distance between centers of activation associated with lexical processing of different words in the same language. Results of phonological processing analyses revealed different centers of activation associated with the first versus the second language in the IFG, but not in the superior temporal gyrus (STG). These findings are discussed within the context of the current literature on cortical organization in bilinguals and suggest variation in bilingual cortical activation associated with lexical, phonological, and orthographic processing.

Orthographic transparency and grapheme–phoneme conversion: An ERP study in Arabic and French readers

Numerous behavioral studies have suggested that orthographic transparency of a language is liable to influence the use of grapheme-phoneme conversion during reading. In order to test this hypothesis, the effect of orthographic transparency on event-related potentials was assessed by comparing French to Arab readers. Indeed, French language, contrary to Arabic one, was expected to favor the use of grapheme-phoneme rules during reading. Our results demonstrated that the N320, a component implicated in phonologic transcription, was modulated by orthographic transparency. Indeed, during reading in their mother tongue, only French subjects clearly elicited a N320. Moreover, the comparisons between activations elicited by Arabic words in Arab subjects and French monolingual people also confirm that the N170 component represents an important orthographic stage. The implications of these results on bilinguism and visual word recognition models are discussed.

Intraoperative Language Localizationin Multilingual Patients With Gliomas

OBJECTIVE

Intraoperative localization of speech is problematic in patients that are fluent with different languages. Previous studies have generated various results depending on the series of patients studied, the type of language and the sensitivity of the tasks applied. It is not clear if languages are mediated by multiple and separate cortical areas, or shared by common areas. Globally considered, previous studies recommended performing a multiple intra-operative mapping for all the languages the patient is fluent for. Aim of this work was to study the feasibility of performing an intra-operative multiple language mapping in a group of multilingual patients with a glioma undergoing awake craniotomy for tumor removal, to describe the intraoperative cortical and subcortical findings in the area of craniotomy, with the final goal to maximally preserve their functional language.

METHODS

Seven late highly proficient multilingual patients with a left frontal glioma were submitted pre-operatively to a battery of tests to evaluate oral language production, comprehension, and repetition. Each language was tested serially starting from the first acquired language. Items which were correctly named during these tests were used to build personalized blocks to be used intraoperatively. Language mapping was undertaken during awake craniotomies, by the use of a Ojemann cortical stimulator during counting and oral naming tasks. Subcortical stimulation by using the same current threshold was applied during tumor resection, in a back and forth fashion, and the same tests.

RESULTS

Cortical sites essential for oral naming were found in 87.5% of patients, those for the first acquired language in 1 to 4 sites, those for the other languages in 1 to 3 sites. Sites for each language were distinct and separate. Number and location of sites were not predictable, being randomly and widely distributed in the cortex around or less frequently over the tumor area. Subcortical stimulations found tracts for the first acquired language in 4 patients, and for the other languages in 3 patients. Three of these patients decreased their fluency immediately after surgery, affecting the first acquired language, which fully recovered in two patients and partially in one. The procedure was agile and well tolerated by the patients.

CONCLUSION

These findings show that multiple cortical and subcortical language mapping during awake craniotomy for tumor removal is a feasible procedure. They support the concept that intraoperative mapping should be performed for all the languages the patient is fluent for to preserve functional integrity.

Functional separation of languages in the bilingual brain: a comparison of electrical stimulation language mapping in 25 bilingual patients and 117 monolingual control patients

Object. The aim of this investigation was to address three questions in bilingualism research: 1) are multiple languages functionally separated within the bilingual brain; 2) are these languages similarly organized; and 3) does language organization in bilinguals mirror that in monolinguals?

Methods. During awake dominant-hemisphere craniotomy in each of 25 bilingual patients, the authors mapped both languages by using identical object-naming stimuli. Essential sites for primary (L1) and secondary (L2) languages were compared. Sites were photographically recorded and plotted onto an anatomically referenced grid system. Language organization in bilinguals was then compared with that in 117 monolinguals and 11 monolingual children.

Conclusions. The authors found distinct language-specific sites as well as shared sites that support both languages. The L1 and L2 representations were similar in total cortical extent but significantly different in anatomical distribution. The L2-specific sites were located exclusively in the posterior temporal and parietal regions, whereas the L1 and shared sites could be found throughout the mapped regions. Bilinguals possessed seven perisylvian language zones, in which L2 sites were significantly underrepresented when compared with the distribution of language sites in monolinguals. These L2-restricted zones overlapped the primary language areas found in monolingual children, indicating that these zones become dedicated to L1 processing. These findings support three conclusions. First, it is necessary to map both languages in bilinguals because L1 and L2 sites are functionally distinct. Second, differences exist in the organization of L1 and L2 sites, with L2-specific sites located exclusively in the posterior temporal and parietal lobes. Third, language organization comparisons in bilingual and monolingual brains demonstrate the presence of L2-restricted zones, which are dedicated to L1.

Bilingual corpus callosum variability

Magnetic resonance imaging was used to produce midsagittal images of the corpus callosum of 19 right-handed adult male and female subjects. The preliminary findings of this study indicate that significant adaptation in the anterior midbody of the corpus callosum has occurred to accommodate multiple language capacity in bilingual individuals compared to monolingual individuals. The main interpretation of this finding is that the precentral gyrus is involved in bilingual faculty adaptation assuming a role consistent with the somatotopical input to areas dedicated to the mouth, and input to association tracts connecting the premotor and supplementary motor cortices. This paper discusses possible implications to neuroscientists, second language educators, and their students.

Functional MRI study of semantic and phonological language processing in bilingual subjects: preliminary findings

The objective of the study was to explore differences in regional fMRI activation topography and lateralization between semantic and phonological tasks performed in English and Spanish in bilingual individuals. Eight bilingual (primary Spanish and secondary English-speaking) individuals performed fMRI noun-verb association and rhyming tasks in both Spanish and English. Functional dataset analysis within Statistical Parametric Mapping (SPM99) with overlay on T1-weighted anatomic images was performed. Significantly higher laterality indices were noted in the semantic tasks as compared with the phonological tasks in the anterior regions of interest comprising the frontal and superior temporal lobes. A task subtraction analysis demonstrated right hemispheric (inferior frontal gyrus and supramarginal gyrus) foci of significantly increased activation in the combined language phonological tasks compared to the combined language semantic tasks; similarly prominent right hemispheric activation was seen in the English phonological-English semantic subtraction, but the analogous Spanish task subtraction revealed no task-related differences. This divergence in activation topography between semantic and phonological tasks performed in the nonnative language, but not in the primary language, suggests that neural networks utilized for phonological and semantic language processing in the nonnative language may not be as similar as those in the primary language.

Organization of language areas in bilingual patients: a cortical stimulation study

OBJECT

In an attempt to gain a better understanding of how multiple languages are represented in the human brain, the authors studied bilingual patients who underwent surgery for brain tumors, during which the authors mapped cortical language sites by using electrostimulation.

METHODS

Reading, counting, and word retrieval tasks were studied in 12 right-handed bilingual patients with no language deficit. All bilingual patients were native to France. One patient spoke four languages. The patients constituted a nonhomogeneous group in terms of language proficiency or age of acquisition. Languages were evaluated and classified into three major groups, depending on proficiency and date of acquisition. Strict conditions of language site validation were applied, separating typical anomia sites from speech arrest or other language sites (such as hesitation sites). A total of 30 speech arrest sites, 16 anomia sites, and three sites of language difficulties (not typically classified as speech arrest) were found throughout the 26 language studies performed. Strict overlapping of language areas (for all language tasks) was found in five patients, whereas the remaining seven had at least one area that was language-specific and sometimes task-specific. Specific areas for a particular language were found for word retrieval tasks (anomia) in eight sites (50%) but also in six (20%) of the reading or counting sites (speech arrest), either in frontal (three patients) or in temporoparietal (four patients) regions. Among the four early bilingual patients tested (languages acquired before the age of 7 years), three had language-specific cortical areas. Interestingly, six patients in this series who had a discrepancy between two languages did not have more cortical areas devoted to the less proficient language (with acknowledgment of the limit in cortical exposure available for testing by the craniotomy).

CONCLUSIONS

In this series, the authors found that bilingual patients could have common but also different cortical areas for both languages in temporoparietal areas and in frontal areas. In some cases, the authors found that language tasks such as counting, reading, or word retrieval in different languages can be sustained by language- and task-specific cortical areas. In bilingual patients, cortical mapping should ideally be performed using different language tasks in all languages in which the patient is fluent.

Bilingualism, brain injury, and recovery

Psychologists and other therapists are seeing an increasingly large number of bilingual individuals. Such clients are a special challenge when there has been some type of brain injury or disease because of the seemingly unpredictable effect such disorders may have on language skills, impacting either or both of the client's languages and interfering with internal speech that plays a role in higher cognitive functions such as insight and awareness. While there are many clinical assumptions about which language will show the least impairment or recover the best, such suppositions based on clinical lore are often contradictory. A review of the literature finds that the outcome of brain injury may be influenced by factors such as cerebral representation of a secondary language, method of language acquisition, age of acquisition, premorbid language proficiency, and style of learning in an individual. Neuropsychological concepts that can explain these findings are examined, along with their implications for therapy, and rehabilitation.

Electrophysiological evidence for priming in response to words and pseudowords in first and second language

The study purpose was to indicate when language-specific processing first occurs and how first and second language priming processes interact. Event-related potentials were recorded from 14 normal native Hebrew speakers, in a variation of lexical decision task, to pairs of stimuli (S1, S2) in Hebrew, English, Hebrew pseudowords, and English pseudowords. Although no behavioral priming was observed, priming by pseudowords in either language affected both N400 and the late positive component of event related potential. N1 and P2 latencies were longer to S2 in semantically related pairs, indicating that language-specific processing may take place as early as auditory cortex. Different processing of first and second language was evident only in response to pseudowords.

Language switching and language representation in Spanish-English bilinguals: an fMRI study

The current experiment was designed to investigate the nature of cognitive control in within- and between-language switching in bilingual participants. To examine the neural substrate of language switching we used functional magnetic resonance imaging (fMRI) as subjects named pictures in one language only or switched between languages. Participants were also asked to name (only in English) a separate set of pictures as either the actions or the objects depicted or to switch between these two types of responses on each subsequent picture. Picture naming compared to rest revealed activation in the dorsolateral prefrontal cortex, which extended down into Broca's area in the left hemisphere. There were no differences in the activation pattern for each language. English and Spanish both activated overlapping areas of the brain. Similarly, there was no difference in activation for naming actions or objects in English. However, there was increased intensity of activation in the dorsolateral prefrontal cortex for switching between languages relative to no-switching, an effect which was not observed for naming of actions or objects in English. We suggest that the dorsolateral prefrontal cortex serves to attenuate interference that results from having to actively enhance and suppress two languages in alternation. These results are consistent with the view that switching between languages involves increased general executive processing. Finally, our results are consistent with the view that different languages are represented in overlapping areas of the brain in early bilinguals.

Cerebral hemodynamic response in Chinese (first) and English (second) language processing revealed by event-related functional MRI

Comparative functional neuroimaging studies using the block design paradigm have previously demonstrated that there are no significant differences in the location of areas of cerebral activation when native Chinese speakers independently process single words or sentences in both the Chinese (first) and English (second) languages. While it has also been documented that significant domains of brain response include the inferior to middle left frontal lobe, the latency, amplitude and duration of the associated hemodynamic changes during isolated neural processing of Chinese and English languages still remain unknown. The aim of this study, therefore, was to examine the characteristics of the hemodynamic alterations in the above-mentioned regions with event-related functional MRI (ER-fMRI) when native Chinese speakers performed verb generation tasks in both the Chinese (first) and English (second) languages. Our results demonstrate the presence of a similar neural activity-induced hemodynamic response in the inferior to middle left frontal lobe during both tasks. Further, there were also no statistically significant differences among the variables that described the hemodynamic response curves. These findings strongly imply that the underlying neural mechanism for Chinese (first) and English (second) language processing may be similar in native Chinese speakers.

Optical imaging of bilingual cortical representations. Case report

The organization of language in the brains of multilingual persons remains controversial. The authors investigated language representations in a proficient bilingual patient by using a novel neuroimaging technique, intraoperative optical imaging of intrinsic signals (iOIS), and a visual object naming task. The results indicate that there are cortical areas that are activated by the use of both English and Spanish languages (superior temporal sulcus, superior and middle temporal gyri, and parts of the supramarginal gyrus). In addition, language-specific areas were identified in the supramarginal (Spanish) and precentral (English) gyri. These results suggest that cortical language representations in bilingual persons may consist of both overlapping and distinct components. Furthermore, this study demonstrates the utility of iOIS in detecting topographical segregation of cognitively distinct cortices.

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.

Bilingual performance on the boston naming test: preliminary norms in Spanish and English

A total of 100 young educated bilingual adults were administered the Boston Naming Test (BNT) (Kaplan, Goodglass, & Weintraub, 1983) in both Spanish and English. Three group performance scores were obtained: English only, Spanish only, and a composite score indicating the total number of items correctly named independent of language. The scores for the entire group were significantly greater in English than in Spanish. An additional set of analyses explored individual differences in picture naming performance across the two languages as measured by the BNT. For a subset of the larger group (n = 25) there were significant differences in composite over single language scoring, but no significant differences between Spanish and English. Item analyses of correct responses were conducted in both languages to explore the construct validity of the standardized administration of the BNT with this population. There was much greater variability in responses over the Spanish items for this bilingual group. The results of a correlation analysis of information obtained from the initial questionnaire with the BNT scores in each language is also reported. The practical implications of this preliminary bilingual BNT normative data are discussed.

Distinct cortical areas associated with native and second languages

The ability to acquire and use several languages selectively is a unique and essential human capacity. Here we investigate the fundamental question of how multiple languages are represented in a human brain. We applied functional magnetic resonance imaging (fMRI) to determine the spatial relationship between native and second languages in the human cortex, and show that within the frontal-lobe language-sensitive regions (Broca's area), second languages acquired in adulthood ('late' bilingual subjects) are spatially separated from native languages. However, when acquired during the early language acquisition stage of development ('early' bilingual subjects), native and second languages tend to be represented in common frontal cortical areas. In both late and early bilingual subjects, the temporal-lobe language-sensitive regions (Wernicke's area) also show effectively little or no separation of activity based on the age of language acquisition. This discovery of language-specific regions in Broca's area advances our understanding of the cortical representation that underlies multiple language functions.

Shifting cerebral dominance in a woman with schizoaffective psychosis: a case study

We describe a case of an intelligent, artistic 50-year-old woman with schizoaffective disorder with a long history of delusional preoccupation with laterality and episodes of reported shifts in handedness. Investigations including dichotic listening and lateralised visual imagery tasks indicated unusual patterns of asymmetry. Executive functions were found to be intact, and EEG and CT scan were normal. Interview schedules revealed high scores for schizotypy, and no evidence of a dissociative disorder, whereas psychotic symptoms with mood lability were evident on mental status examination. The subject's preoccupations are illustrated with a selection of her artistic productions. The case is discussed in the context of reports of a relationship between schizophrenia and ambiguous handedness. A cognitive neuropsychiatric formulation briefly explores the possibility of alternative cerebral hemispheres affecting cognitive-perceptual operations.