Paradoxical recovery in a bilingual patient with aphasia after right capsuloputaminal infarction

Systematic Review and Meta-Analyses of Word Production Abilities in Dysfunction of the Basal Ganglia: Stroke, Small Vessel Disease, Parkinson's Disease, and Huntington's Disease

Clinical populations with basal ganglia pathologies may present with language production impairments, which are often described in combination with comprehension measures or attributed to motor, memory, or processing-speed problems. In this systematic review and meta-analysis, we studied word production in four (vascular and non-vascular) pathologies of the basal ganglia: stroke affecting the basal ganglia, small vessel disease, Parkinson's disease, and Huntington's disease. We compared scores of these clinical populations with those of matched cognitively unimpaired adults on four well-established production tasks, namely picture naming, category fluency, letter fluency, and past-tense verb inflection. We conducted a systematic search in PubMed and PsycINFO with terms for basal ganglia structures, basal ganglia disorders and language production tasks. A total of 114 studies were included, containing results for one or more of the tasks of interest. For each pathology and task combination, effect sizes (Hedges' g) were extracted comparing patient versus control groups. For all four populations, performance was consistently worse than that of cognitively unimpaired adults across the four language production tasks (p-values < 0.010). Given that performance in picture naming and verb inflection across all pathologies was quantified in terms of accuracy, our results suggest that production impairments cannot be fully explained by motor or processing-speed deficits. Our review shows that while language production difficulties in these clinical populations are not negligible, more evidence is necessary to determine the exact mechanism that leads to these deficits and whether this mechanism is the same across different pathologies.

The Relationship between Language Control, Semantic Control and Nonverbal Control

The purpose of this study was to examine the relationship between language control, semantic control, and nonverbal control in bilingual aphasia. Twelve bilingual adults with aphasia (BPWA) and 20 age-matched bilingual adults (AMBA) completed a language control task, semantic control task, and nonverbal control task, each designed to examine resistance to distractor interference. AMBA and BPWA exhibited significant effects of control on all tasks. To examine efficiency of control, conflict magnitudes for each task and group were analyzed. Findings revealed that AMBA exhibited larger conflict magnitudes on the semantic control task and nonverbal control task compared to the language control task, whereas BPWA exhibited no difference in conflict magnitudes between the language control task and semantic control task. Further analysis revealed that BPWA semantic control conflict magnitude was smaller than AMBA semantic control conflict magnitude. Taken together, these findings suggest that BPWA present with diminished effects of semantic control. In the final analysis, conflict magnitudes across tasks were correlated. For AMBA, semantic control and nonverbal control conflict magnitudes were significantly correlated, suggesting that these two types of control are related. For BPWA, language control and nonverbal control conflict magnitudes were significantly correlated; however, this finding may capture effects of domain general cognitive control as a function of increased cognitive load, rather than domain general cognitive control as a function of language control.

Voluntary Language Switching in the Context of Bilingual Aphasia

As studies of bilingual language control (BLC) seek to explore the underpinnings of bilinguals’ abilities to juggle two languages, different types of language switching tasks have been used to uncover switching and mixing effects and thereby reveal what proactive and reactive control mechanisms are involved in language switching. Voluntary language switching tasks, where a bilingual participant can switch freely between their languages while naming, are being utilized more often due to their greater ecological validity compared to cued switching paradigms. Because this type of task had not yet been applied to language switching in bilingual patients, our study sought to explore voluntary switching in bilinguals with aphasia (BWAs) as well as in healthy bilinguals. In Experiment 1, we replicated previously reported results of switch costs and mixing benefits within our own bilingual population of Catalan-Spanish bilinguals. With Experiment 2, we compared both the performances of BWAs as a group and as individuals against control group performance. Results illustrated a complex picture of language control abilities, indicating varying degrees of association and dissociation between factors of BLC. Given the diversity of impairments in BWAs’ language control mechanisms, we highlight the need to examine BLC at the individual level and through the lens of theoretical cognitive control frameworks in order to further parse out how bilinguals regulate their language switching.

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.

What Influences Language Impairment in Bilingual Aphasia? A Meta-Analytic Review

Patterns of language impairment in multilingual speakers with post-stroke aphasia are diverse: in some cases the language deficits are parallel, that is, all languages are impaired relatively equally, whereas in other cases deficits are differential, that is, one language is more impaired than the other(s). This diversity stems from the intricate structure of the multilingual language system, which is shaped by a complex interplay of influencing factors, such as age of language acquisition, frequency of language use, premorbid proficiency, and linguistic similarity between one's languages. Previous theoretical reviews and empirical studies shed some light on these factors, however no clear answers have been provided. The goals of this review were to provide a timely update on the increasing number of reported cases in the last decade and to offer a systematic analysis of the potentially influencing variables. One hundred and thirty cases from 65 studies were included in the present systematic review and effect sizes from 119 cases were used in the meta-analysis. Our analysis revealed better performance in L1 compared to L2 in the whole sample of bilingual speakers with post-stroke aphasia. However, the magnitude of this difference was influenced by whether L2 was learned early in childhood or later: those who learned L2 before 7 years of age showed comparable performance in both of their languages contrary to the bilinguals who learned L2 after 7 years of age and showed better performance in L1 compared to L2. These robust findings were moderated mildly by premorbid proficiency and frequency of use. Finally, linguistic similarity did not appear to influence the magnitude of the difference in performance between L1 and L2. Our findings from the early bilingual subgroup were in line with the previous reviews which included mostly balanced early bilinguals performing comparably in both languages. Our findings from the late bilingual subgroup stressed the primacy of L1 and the importance of age of L2 learning. In addition, the evidence from the present review provides support for theories emphasizing the role of premorbid proficiency and language use in language impairment patterns in bilingual aphasia.

Neural basis of bilingual language control

Acquiring and speaking a second language increases demand on the processes of language control for bilingual as compared to monolingual speakers. Language control for bilingual speakers involves the ability to keep the two languages separated to avoid interference and to select one language or the other in a given conversational context. This ability is what we refer with the term "bilingual language control" (BLC). It is now well established that the architecture of this complex system of language control encompasses brain networks involving cortical and subcortical structures, each responsible for different cognitive processes such as goal maintenance, conflict monitoring, interference suppression, and selective response inhibition. Furthermore, advances have been made in determining the overlap between the BLC and the nonlinguistic executive control networks, under the hypothesis that the BLC processes are just an instantiation of a more domain-general control system. Here, we review the current knowledge about the neural basis of these control systems. Results from brain imaging studies of healthy adults and on the performance of bilingual individuals with brain damage are discussed.

Aphasia in vascular lesions of the basal ganglia: A comprehensive review

Between 1970 and 1990, the study of aphasia secondary to subcortical lesions (including the basal ganglia - BG) was largely driven by the advent of modern neuroimaging techniques such as MRI and PET. However, attempts to characterize a pattern of language abnormalities in patients with basal ganglia lesions proved unfruitful. We conducted a comprehensive review of language disturbances after vascular lesions in the BG. Literature search in Medline and LILACS (1966-2016) and PsychINFO (last 25years) was conducted, and returned 145 articles, with 57 eligible for the review yielding data on 303 patients. We report the clinical and neuroimaging features of these cases. Results showed that aphasias caused by BG lesions are heterogeneous with weak clinicoanatomical correlations. Data derived from follow-up and flow/metabolism studies suggest that subcortical aphasia caused by BG lesions involves hypoperfusion in the cortical territories of the middle cerebral/internal carotid arteries (MCA/ICA) and their branches.

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.

Recovery of language function in Korean-Japanese crossed bilingual aphasia following right basal ganglia hemorrhage

Few studies have investigated language recovery patterns and the mechanisms of crossed bilingual aphasia following a subcortical stroke. In particular, Korean-Japanese crossed bilingual aphasia has not been reported. A 47-year-old, right-handed man was diagnosed with an extensive right basal ganglia hemorrhage. He was bilingual, fluent in both Korean and Japanese. After his stroke, the patient presented with crossed aphasia. We investigated changes in the Korean (L1) and Japanese (L2) language recovery patterns. Both Korean and Japanese versions of the Western Aphasia Battery (WAB) were completed one month after the stroke, and functional magnetic resonance imaging (fMRI) was performed using picture-naming tasks. The WAB showed a paradoxical pattern of bilingual aphasia, with an aphasia quotient (AQ) of 32 for Korean and 50.6 for Japanese, with Broca's aphasia. The patient scored better in the Japanese version of all domains of the tests. The fMRI study showed left lateralized activation in both language tasks, especially in the inferior frontal gyrus. After six months of language therapy targeting L1, the Korean-WAB score improved significantly, while the Japanese-WAB score showed slight improvement. In this case, the subcortical lesion contributed to crossed bilingual aphasia more highly affecting L1 due to loss of the cortico-subcortical control mechanism in the dominant hemisphere. The paradoxical pattern of bilingual aphasia disappeared after lengthy language therapy targeting L1, and the therapy effect did not transfer to L2. Language recovery in L1 might have been accomplished by reintegrating language networks, including the contralesional language homologue area in the left hemisphere.

Comparing language outcomes in monolingual and bilingual stroke patients

Hope et al. compare language outcomes in monolingual and bilingual stroke patients, and find that prognostic models based on monolingual data alone overestimate language skills in bilingual patients. Both groups seem sensitive to damage in the same brain regions, but bilinguals appear more sensitive to that damage than monolinguals.

Post-stroke prognoses are usually inductive, generalizing trends learned from one group of patients, whose outcomes are known, to make predictions for new patients. Research into the recovery of language function is almost exclusively focused on monolingual stroke patients, but bilingualism is the norm in many parts of the world. If bilingual language recruits qualitatively different networks in the brain, prognostic models developed for monolinguals might not generalize well to bilingual stroke patients. Here, we sought to establish how applicable post-stroke prognostic models, trained with monolingual patient data, are to bilingual stroke patients who had been ordinarily resident in the UK for many years. We used an algorithm to extract binary lesion images for each stroke patient, and assessed their language with a standard tool. We used feature selection and cross-validation to find ‘good’ prognostic models for each of 22 different language skills, using monolingual data only (174 patients; 112 males and 62 females; age at stroke: mean = 53.0 years, standard deviation = 12.2 years, range = 17.2–80.1 years; time post-stroke: mean = 55.6 months, standard deviation = 62.6 months, range = 3.1–431.9 months), then made predictions for both monolinguals and bilinguals (33 patients; 18 males and 15 females; age at stroke: mean = 49.0 years, standard deviation = 13.2 years, range = 23.1–77.0 years; time post-stroke: mean = 49.2 months, standard deviation = 55.8 months, range = 3.9–219.9 months) separately, after training with monolingual data only. We measured group differences by comparing prediction error distributions, and used a Bayesian test to search for group differences in terms of lesion-deficit associations in the brain. Our models distinguish better outcomes from worse outcomes equally well within each group, but tended to be over-optimistic when predicting bilingual language outcomes: our bilingual patients tended to have poorer language skills than expected, based on trends learned from monolingual data alone, and this was significant (P < 0.05, corrected for multiple comparisons) in 13/22 language tasks. Both patient groups appeared to be sensitive to damage in the same sets of regions, though the bilinguals were more sensitive than the monolinguals.

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.

Impaired L1 and executive control after left basal ganglia damage in a bilingual Basque-Spanish person with aphasia

Bilinguals must focus their attention to control competing languages. In bilingual aphasia, damage to the fronto-subcortical loop may lead to pathological language switching and mixing and the attrition of the more automatic language (usually L1). We present the case of JZ, a bilingual Basque-Spanish 53-year-old man who, after haematoma in the left basal ganglia, presented with executive deficits and aphasia, characterised by more impaired language processing in Basque, his L1. Assessment with the Bilingual Aphasia Test revealed impaired spontaneous and automatic speech production and speech rate in L1, as well as impaired L2-to-L1 sentence translation. Later observation led to the assessment of verbal and non-verbal executive control, which allowed JZ's impaired performance on language tasks to be related to executive dysfunction. In line with previous research, we report the significant attrition of L1 following damage to the left basal ganglia, reported for the first time in a Basque-Spanish bilingual. Implications for models of declarative and procedural memory are discussed.

Principles underlying the Bilingual Aphasia Test (BAT) and its uses

The Bilingual Aphasia Test (BAT) is designed to be objective (so it can be administered by a lay native speaker of the language) and equivalent across languages (to allow for a comparison between the languages of a given patient as well as across patients from different institutions). It has been used not only with aphasia but also with any condition that results in language impairment (Alzheimer's, autism, cerebellar lesions, developmental language disorders, mild cognitive impairment, motor neuron disease, multiple sclerosis, Parkinson's, vascular dementia, etc.). It has also been used for research purposes on non-brain-damaged unilingual and bilingual populations. By means of its 32 tasks, it assesses comprehension and production of implicit linguistic competence and metalinguistic knowledge (which provide indications for apposite rehabilitation strategies). Versions of the BAT are available for free download at www.mcgill.ca/linguistics/research/bat/.

A short-form version of the Boston Naming Test for language screening in dementia in a bilingual rural community in Galicia (Spain)

BACKGROUND

Aphasia, one of the core symptoms of cortical dementia, is routinely evaluated using graded naming tests like the Boston Naming Test (BNT). However, the application of this 60-item test is time-consuming and shortened versions have been devised for screening. The hypothesis of this research is that a specifically designed shortened version of the BNT could replace the original 60-item BNT as part of a mini-battery for screening for dementia. The objective of this study was to design a short version of the BNT for a rural population in Galicia (Spain).

METHODS

A clinic group of 102 patients including 43 with dementia was recruited along with 78 healthy volunteers. The clinic and control groups were scored on the Spanish version of the Mini-mental State Examination (MMSE) and BNT. In addition, the clinic group was tested with standard neuropsychological instruments and underwent brain investigations and routine neurological examination. BNT items with specificity and sensitivity above 0.5 were selected to compose a short battery of 11 pictures named BNTOu11. ANOVA and mean comparisons were made for MMSE and BNT versions. Receiver operating characteristics (ROC) curves and internal consistency were calculated.

RESULTS

Areas under ROC curves (AUC) did not show statistically significant differences; therefore BNTOu11's AUC (0.814) was similar to the 60-item BNT versions (0.785 and 0.779), to the short versions from Argentina (0.772) and Andalusia (0.799) and to the Spanish MMSE (0.866). BNTOu11 had higher internal consistency than the other short versions.

CONCLUSIONS

BNTOu11 is a useful and time-saving method as part of a battery for screening for dementia in a psychogeriatric outpatient unit.

Sentence translation in proficient bilinguals: a direct electrostimulation brain mapping

Direct cortical electrostimulation was used to study cortical areas hypothetically involved in translation in bilinguals during brain tumour resections, with a view to sparing these functional areas. A series of seven proficient bilingual patients was studied: two left-handed and five right-handed individuals with no pre-existing language deficit. Hemispheric cortex (on the side contralateral to the patient's hand-dominance) was directly stimulated whilst the patient performed naming and reading tasks in both languages and a translation task (of a written text from their second 'learned' language to their first or 'native' language). Of the 147 different cortical sites studied, 26 'language functional sites' were detected, where electrostimulation affected reading and/or naming in the patient's native and/or second learned language. Of these, 8 sites (in 4 patients) were "task-specific" and "language-specific" i.e., affecting only naming or reading in only one of the patient's languages. Of the 26 "language sites", only 3 produced any interferences in translation. All of these were located in frontal regions. Electrostimulation at these sites caused the patient to stop translating abruptly, but no language switching or other translation-related phenomenon was observed. No site was found that was involved only in translation and not other language tasks. Overall, in contrast to other language tasks, cortical structures of the convexity were rarely involved in translation. We suggest that translation interference could be more readily detected by subcortical stimulations. This spatial dissociation within the brain of translation function versus other language functions could explain the cases of dissociated language impairments observed in some bilingual patients with brain lesions. On a practical level, because the cortical sites found by translation tasks are few and related with other cortical language sites, we think that translation tasks provide little additional helpful information for cortical brain mapping in bilingual neurosurgical patients.

Language control and parallel recovery of language in individuals with aphasia

Background: The causal basis of the different patterns of language recovery following stroke in bilingual speakers is not well understood. Our approach distinguishes the representation of language from the mechanisms involved in its control. Previous studies have suggested that difficulties in language control can explain selective aphasia in one language as well as pathological switching between languages. Here we test the hypothesis that difficulties in managing and resolving competition will also be observed in those who are equally impaired in both their languages even in the absence of pathological switching.Aims: To examine difficulties in language control in bilingual individuals with parallel recovery in aphasia and to compare their performance on different types of conflict task.Methods & Procedures: Two right-handed, non-native English-speaking participants who showed parallel recovery of two languages after stroke and a group of non-native English-speaking, bilingual controls described a scene in English and in their first language and completed three explicit conflict tasks. Two of these were verbal conflict tasks: a lexical decision task in English, in which individuals distinguished English words from non-words, and a Stroop task, in English and in their first language. The third conflict task was a non-verbal flanker task.Outcomes & Results: Both participants with aphasia were impaired in the picture description task in English and in their first language but showed different patterns of impairment on the conflict tasks. For the participant with left subcortical damage, conflict was abnormally high during the verbal tasks (lexical decision and Stroop) but not during the non-verbal flanker task. In contrast, for the participant with extensive left parietal damage, conflict was less abnormal during the Stroop task than the flanker or lexical decision task.Conclusions: Our data reveal two distinct control impairments associated with parallel recovery. We stress the need to explore the precise nature of control problems and how control is implemented in order to develop fuller causal accounts of language recovery patterns in bilingual aphasia.