Is bilingualism protective for adults with aphasia?

Language abilities, not cognitive control, predict language mixing behavior in bilingual speakers with aphasia

PURPOSE

Language Mixing (LM) occurs among neurotypical bilinguals as well as among bilingual persons with aphasia (BiPWAs). The current study aimed to investigate whether LM in BiPWAs stems from a linguistic impairment, an impairment in cognitive control, or both.

METHOD

Twenty Russian-Hebrew-speaking BiPWAs were split into two groups based on aphasia severity (Severe/Moderate vs. Mild). Frequencies and patterns of LM in narrative production by BiPWAs in L1-Russian and in L2-Hebrew were analyzed. To investigate the underlying mechanisms of LM, all participants completed linguistic background questionnaires, the Bilingual Aphasia Test (BAT) in both languages, and a battery of 10 cognitive tests.

RESULTS

The results indicated an effect of aphasia severity and an effect of language. Higher LM frequency was observed in BiPWAs with severe/moderate aphasia symptoms as compared to BiPWAs with mild symptoms. In both groups, higher LM frequency was observed in L2-Hebrew narratives, the weaker post-stroke language for most participants in the sample. The results also showed qualitative LM differences in L1-Russsian and L2-Hebrew contexts. In L1-Russian narratives, BiPWAs mainly switched to L2-Hebrew nouns, while in L2-Hebrew narratives, they mainly inserted L1-Russian discourse markers and function words.

CONCLUSIONS

Linguistic factors such as pre- and post-stroke self-rated language proficiency and level of language impairment due to aphasia were found to predict LM frequency in L1-Russian and in L2-Hebrew. Cognitive abilities did not predict LM frequency. Based on our findings, we suggest that LM behavior in BiPWAs might be primarily related to language skills in L1 and L2, rather than to cognitive control impairments.

French Phonological Component Analysis and aphasia recovery: A bilingual perspective on behavioral and structural data

Studies show bilingualism entails an advantage in cognitive control tasks. There is evidence of a bilingual advantage in the context of aphasia, resulting in better cognitive outcomes and recovery in bilingual persons with aphasia compared to monolingual peers. This bilingual advantage also results in structural changes in the right hemisphere gray matter. Very few studies have examined the so-called bilingual advantage by reference to specific anomia therapy efficacy. This study aims to compare the effect of French-Phonological Component Analysis (Fr-PCA) in monolinguals and bilingual persons with aphasia, both at the linguistic and cognitive control level, and to examine the structural impact of left hemisphere lesion location and right hemisphere structural data. Eight participants with chronic aphasia received Fr-PCA for a total of 15 h over 5 weeks. The results showed improved accuracy for treated words and generalization to untreated items and discourse in both groups, and improved Flanker task performance for some participants. Bilingual participants improved more than monolinguals for picture-naming tasks and narrative discourse. Damage to the left postcentral gyrus and the middle frontal gyrus was associated with less therapy-induced improvement. Additionally, left hemisphere damage to the inferior parietal gyrus and postcentral gyrus was associated with reduced cognitive control pre-therapy. Undamaged right hemisphere cortical thicknesses were significantly different between groups; the inferior frontal gyrus and the middle frontal gyrus were greater for the bilingual participants and correlated with cognitive control skills. These results suggest a bilingual advantage in anomia recovery following Fr-PCA, potentially resulting from enhanced cognitive control abilities that could be supported by right hemisphere neural reserve.

Understanding, facilitating and predicting aphasia recovery after rehabilitation

Purpose: This paper reviews several studies whose aim was to understand the nature of language recovery in chronic aphasia and identify predictors of how people may recover their language functions after a brain injury.Method: Several studies that mostly draw from data collected within the Centre for Neurobiology of Language Recovery were reviewed and categorised in four aspects of language impairment and recovery in aphasia: (a) neural markers for language impairment and recovery, (b) language and cognitive markers for language impairment and recovery, (c) effective treatments and (d) predictive modelling of treatment-induced rehabilitation.Result: Language impairment and recovery in stroke-induced aphasia is multi-factorial, including patient-specific and treatment-specific factors. A combination of these factors may help us predict treatment responsiveness even before treatment begins.Conclusion: Continued work on this topic will lead to a better understanding of the mechanisms that underly language impairment and treatment-induced recovery in aphasia, and, consequently, use this information to predict each person's recovery profile trajectory and provide optimal prescriptions regarding the type and dosage of treatment.

Aphasia in Multilingual Patients

PURPOSE OF REVIEW

We summarize recent published work concerning assessment and treatment of aphasia in bilingual and multilingual people and review current related models of treatment outcomes. As well, we discuss studies that address the recently debated topic of cognitive processes in bilingual individuals with aphasia, with a focus on the effects of bilingualism on aphasia recovery and its potential protective effects.

RECENT FINDINGS

Providing assessment and treatment tools that best serve multilingual individuals with aphasia and unpacking the variables and mechanisms that underlie response to treatment have emerged as goals of several recent studies. Additionally, while findings are still contradictory, some empirical studies reported that aphasia may manifest less severely in multilingual individuals and may improve faster compared to in monolingual counterparts. The findings of recent studies with the focus of aphasia in multilingual individuals are crucial to understanding theoretical and clinical aspects of brain-related language impairment in multilingual people and to the study of language representation and processing in the brain.

Bilingual Abstract Semantic Associative Network Training (BAbSANT): A Polish-English case study

INTRODUCTION

This article presents a novel approach to anomia therapy (i.e., BAbSANT: Bilingual Abstract Semantic Associative Network Training) for bilingual persons with aphasia (B-PWA) that capitalizes both on lexico-semantic theories in bilingualism and general theories of semantic organization and learning. Based on previous work, we hypothesized that training abstract words in either language would promote within-language generalization, while training in the nondominant language would promote both within- and cross-language generalization.

METHODS

This case study used a single-subject A₁BA₂CA₃ design. The participant was living with aphasia secondary to stroke and spoke both Polish and English, with Polish being his native and dominant language. Phase B consisted of abstract word training in Polish and phase C consisted of abstract word training in English. Prior to initiating therapy, in addition to a comprehensive language battery, we administered a cognitive control task to explore the relationship between cognitive control and treatment outcome.

RESULTS

We found within-language generalization regardless of the trained language, replicating previous work in monolingual persons with aphasia, further supporting the utility of training abstract words. However, contrary to our second hypothesis, cross-language generalization only occurred when the stronger language was trained.

CONCLUSIONS

The discussion of the results of this case study is framed within previous work and theories of bilingualism. The lack of cross-language generalization when the weaker language was trained is discussed, taking into account nonverbal cognitive control deficits. In addition to showing the efficacy of BAbSANT, these results highlight the importance of considering cognitive control as a factor influencing therapeutic outcomes in anomia treatment in bilingual PWA.

Bilingualism as a protective factor in aphasia

BACKGROUND

Bilingualism may affect the profile of cognitive disturbances associated with stroke. Its impact on aphasia severity, however, is in need of substantiation.

AIMS

To determine the relationship between bilingualism and vascular aphasia severity.

METHODS

This is an observational cross-sectional study conducted on people with post-stroke aphasia. Our sample included 155 monolingual and 53 bilingual vascular aphasia patients. They were selected in a neurological hospital in Kolkata (West Bengal, India).

RESULTS

The Bengali version of Western Aphasia Battery (BWAB) was used in this study. Aphasia severity was compared between monolingual and bilingual participants. The overall difference in the mean aphasia quotient (AQ) between bilingual and monolingual participants was statistically significant (p = 0.009). It was also found that in bilingual participants, aphasia was less severe in certain subgroups, namely: higher lesion volume, male gender, and sub-cortical stroke, while in none of the subgroups a monolingual advantage was documented.

CONCLUSION

Current results suggest that bilingualism represents a protective factor in vascular aphasia; this effect is observed particularly in some aphasia subgroups.

Brain-Derived Neurotrophic Factor Polymorphism and Aphasia after Stroke

Stroke is one of the most deliberating causes of mortality and disability worldwide. Studies have implicated Val66Met polymorphism of the brain-derived neurotrophic factor (BDNF) gene as a genetic factor influencing stroke recovery. Still, the role of BDNF polymorphism in poststroke aphasia is relatively unclear. This review assesses the recent evidence on the association between the BDNF polymorphism and aphasia recovery in poststroke patients. The article highlights BNDF polymorphism characteristics, speech and language interventions delivered, and the influence of BNDF polymorphism on poststroke aphasia recovery. We conducted a literature search through PubMed and Google Scholar with the following terms: “brain derived-neurotrophic factor” and “aphasia” for original articles from January 2000 until June 2020. Out of 69 search results, a detailed selection process produced a total of 3 articles that met the eligibility criteria. All three studies included Val66Met polymorphism as the studied human BDNF gene. One of the studies demonstrated insufficient evidence to conclude that BDNF polymorphism plays a role in poststroke aphasia recovery. The remaining two studies have shown that Met allele genotype (either single or double nucleotides) was associated with poor aphasia recovery, in either acute or chronic stroke. Carriers of the Val66Met polymorphism of BDNF gave a poorer response to aphasia intervention and presented with more severe aphasia.

Bilingualism: Pathway to Cognitive Reserve

Cognitive reserve is characterized by a dissociation between cognitive level and brain structure, thereby reducing the impact of deteriorating brain structure on cognitive function. Cognitive reserve is therefore a promising approach to maintaining cognitive function and protecting against symptoms of dementia. The present paper evaluates evidence supporting the claim that bilingualism contributes to cognitive reserve. Four types of evidence are presented: (i) brain and cognitive function in healthy aging, (ii) age of onset of symptoms of dementia, (iii) relation between clinical level and neuropathology for patients, and (iv) rate of cognitive decline in later stages of dementia. In all cases, bilinguals revealed patterns that were consistent with the interpretation of protection from cognitive reserve when compared with monolinguals.

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.