The relationship between bilingual experience and gyrification in adulthood: A cross-sectional surface-based morphometry study

Language Learning for People Living with Dementia and Their Caregivers: Feasibility and the Quality of Experience

BACKGROUND

A body of research from around the world has reported positive effects of bilingualism on cognitive ageing and dementia. However, little is known about whether foreign language learning could be applied as an intervention for people already living with dementia. Yet, before it is possible to determine the efficacy of language courses as an intervention for people living with dementia (PLWD), it is necessary to establish whether such an intervention is feasible. Our study explored this possibility.

METHODS

We conducted an exploratory study to examine the feasibility and tolerability of 2-week Italian beginner courses for PLWD in early stages and their family carers in two Scottish Dementia Resource Centres (DRCs). The courses were delivered by trained tutors from Lingo Flamingo, a social enterprise specialising in language teaching for older learners and learners with dementia. Twelve PLWD and seven carers participated in the study. Focus groups preceded and followed the courses. Additional post-course open interviews with the DRC managers were conducted, with a follow-up via telephone approximately one year later.

RESULTS

Qualitative content analysis resulted in 12 themes, 5 reflected in the interview schedule and 7 arising from the focus groups and interviews. Overall, the courses were perceived positively by PLWD, carers, and DRC managers, although a few logistically and linguistically challenging aspects were also mentioned. The courses were found to positively impact both the individual by increasing self-esteem and producing a sense of accomplishment as well as the group by creating a sense of community. Notably, no adverse effects (in particular no confusion or frustration) were reported.

CONCLUSION

The positive outcomes of our study open a novel avenue for future research to explore foreign language training in dementia as an intervention and its implications.

Does Diglossia Impact Brain Structure? Data from Swiss German Early Diglossic Speakers

(1) Background: Bilingualism has been reported to shape the brain by inducing cortical changes in cortical and subcortical language and executive networks. Similar yet different to bilingualism, diglossia is common in Switzerland, where the German-speaking population switches between an everyday spoken Swiss German (CH-GER) dialect and the standard German (stGER) used for reading and writing. However, no data are available for diglossia, defined as the use of different varieties or dialects of the same language, regarding brain structure. The aim of our study is to investigate if the presence of this type of diglossia has an impact on the brain structure, similar to the effects seen in bilingualism. (2) Methods: T1-weighted anatomical MRI scans of participants were used to compare the grey matter density and grey matter volume of 22 early diglossic CH-GER-speaking and 20 non-diglossic French-speaking right-handed university students, matched for age, linguistics and academic background. The images were processed with Statistical Parametric Mapping SPM12 and analyzed via voxel- and surface-based morphometry. (3) Results: A Bayesian ANCOVA on the whole brain revealed no differences between the groups. Also, for the five regions of interest (i.e., planum temporale, caudate nucleus, ACC, DLPFC and left interior parietal lobule), no differences in the cortical volume or thickness were found using the same statistical approach. (4) Conclusion: The results of this study may suggest that early diglossia does not shape the brain structure in the same manner as bilingualism.

Graph Theoretical Analysis of Structural Covariance Reveals the Relevance of Visuospatial and Attentional Areas in Essential Tremor Recovery After Stereotactic Radiosurgical Thalamotomy

Essential tremor (ET) is the most common movement disorder. Its pathophysiology is only partially understood. Here, we leveraged graph theoretical analysis on structural covariance patterns quantified from morphometric estimates for cortical thickness, surface area, and mean curvature in patients with ET before and one year after (to account for delayed clinical effect) ventro-intermediate nucleus (Vim) stereotactic radiosurgical thalamotomy. We further contrasted the observed patterns with those from matched healthy controls (HCs). Significant group differences at the level of individual morphometric properties were specific to mean curvature and the post-/pre-thalamotomy contrast, evidencing brain plasticity at the level of the targeted left thalamus, and of low-level visual, high-level visuospatial and attentional areas implicated in the dorsal visual stream. The introduction of cross-correlational analysis across pairs of morphometric properties strengthened the presence of dorsal visual stream readjustments following thalamotomy, as cortical thickness in the right lingual gyrus, bilateral rostral middle frontal gyrus, and left pre-central gyrus was interrelated with mean curvature in the rest of the brain. Overall, our results position mean curvature as the most relevant morphometric feature to understand brain plasticity in drug-resistant ET patients following Vim thalamotomy. They also highlight the importance of examining not only individual features, but also their interactions, to gain insight into the routes of recovery following intervention.

Foreign Language Learning in Older Adults: Anatomical and Cognitive Markers of Vocabulary Learning Success

In recent years, foreign language learning (FLL) has been proposed as a possible cognitive intervention for older adults. However, the brain network and cognitive functions underlying FLL has remained largely unconfirmed in older adults. In particular, older and younger adults have markedly different cognitive profile—while older adults tend to exhibit decline in most cognitive domains, their semantic memory usually remains intact. As such, older adults may engage the semantic functions to a larger extent than the other cognitive functions traditionally considered the most important (e.g., working memory capacity and phonological awareness). Using anatomical measurements and a cognitive test battery, the present study examined this hypothesis in twenty cognitively normal older adults (58–69 years old), who participated in a two-month Italian learning programme. Results showed that the immediate learning success and long-term retention of Italian vocabularies were most consistently predicted by the anatomical measures of the left pars orbitalis and left caudal middle frontal cortex, which are implicated in semantic and episodic memory functions. Convergent evidence was also found based on the pattern of cognitive associations. Our results are consistent with a prominent role of semantic and episodic memory functions in vocabulary learning in older learners.

Sex differences of language abilities of preschool children with autism spectrum disorder and their anatomical correlation with Broca and Wernicke areas

OBJECTIVE

People with autism spectrum disorder (ASD) often have language difficulties. This study focuses on whether there are sex differences in language ability in children with ASD and aims to analyze whether such differences may arise from developmental imbalances in the anatomical structures of Broca and Wernicke areas.

METHODS

The language development quotient (DQ) scores of Gesell Developmental Scale (GDS) and the scores of language communication of Childhood Autism Rating Scale (CARS) were used to judge the language ability, and the FREESURFER software extracted the anatomical structures of Broca and Wernicke areas on 3DT1 sequences. We analyzed the correlation between the anatomical structure of Broca/Wernicke areas and language abilities assessments.

RESULTS

The study initially included 44 cases of ASD, with 36 males (81.8 %) and 8 females (18.2%), and the age range was 24-72 months. Males have better language abilities than females. Specifically, the GDS verbal DQ of males was significantly higher than that of females (56.50 ± 18.02 vs. 29.23 ± 6.67, p < 0.001). Broca thickness-L was positively correlated with verbal DQ scores in GDS (r = 0.382, p = 0.011) and lower than grade 2 and 3 on the CARS verbal communication grade 4 (5.76 ± 0.17 vs. 6.21 ± 0.30 and 6.11 ± 0.35), with statistically significant differences between groups (p < 0.05).

CONCLUSION

There were sex differences in the language abilities of preschoolers with ASD, which may be due to an imbalance development of certain structures in Broca and Wernicke areas, especially Broca area.

Structural brain changes with second language learning: A longitudinal voxel-based morphometry study

The underlying mechanisms that adapt with L2 learning are still poorly understood. The present longitudinal study examined the effects of L2 learning on grey matter structure of Chinese college freshmen majoring in English. Participants were scanned twice, one year apart. Our voxel-based morphometry analyses revealed that gray matter volume (GMV) decreased in the left anterior cingulate cortex (ACC) and right inferior frontal gyrus (IFG) after L2 learning for one year. Critically, these structural adaptations correlated with changes in participants' language control ability across L2 learning. Moreover, age of acquisition of L2 was a significant predictor of volumetric change in the left ACC and L2 proficiency was a significant predictor of volumetric change in the right IFG. Overall, these findings enrich our understanding of the dynamic nature of structural brain adaptations, and the mechanisms these adaptations index, as a function of classroom L2 learning.

The bilingual structural connectome: Dual-language experiential factors modulate distinct cerebral networks

Bilingualism is a natural laboratory for studying whether the brain's structural connectome is influenced by different aspects of language experience. However, evidence on how distinct components of bilingual experience may contribute to structural brain adaptations is mixed. The lack of consistency, however, may depend, at least in part, on methodological choices in data acquisition and processing. Herein, we adopted the Network Neuroscience framework to investigate how individual differences in second language (L2) exposure, proficiency, and age of acquisition (AoA) - measured as continuous between-subject variables - relate to whole-brain structural organization. We observed that L2 exposure modulated the connectivity of two networks of regions subserving language comprehension and production. L2 proficiency was associated with enhanced connectivity within a rostro-caudal network, which supports language selection and word learning. Moreover, L2 AoA and exposure affected inter-hemispheric communication between control-related regions. These findings expand mechanistic knowledge about particular environmental factors associated with specific variation in brain structure.

Bilingual experience and intrinsic functional connectivity in adults, aging, and Alzheimer's disease

The past decade marked the beginning of the use of resting-state functional connectivity (RSFC) imaging in bilingualism studies. This paper intends to review the latest evidence of changes in RSFC in language and cognitive control networks in bilinguals during adulthood, aging, and early Alzheimer's disease, which can add to our understanding of brain functional reshaping in the context of second language (L2) acquisition. Because of high variability in bilingual experience, recent studies mostly focus on the role of the main aspects of bilingual experience (age of acquisition (AoA), language proficiency, and language usage) on intrinsic functional connectivity (FC). Existing evidence accounts for stronger FC in simultaneous rather than sequential bilinguals in language and control networks, and the modulation of the AoA impact by language proficiency and usage. Studies on older bilingual adults show stronger FC in language and frontoparietal networks and preserved FC in posterior brain regions, which can protect the brain against cognitive decline and neurodegenerative processes. Altered RSFC in language and control networks subsequent to L2 training programs also is associated with improved global cognition in older adults. This review ends with a brief discussion of potential confounding factors in bilingualism research and conclusions and suggestions for future research.

Bilingualism and domain-general cognitive functions from a neural perspective: A systematic review

A large body of research has indicated that bilingualism - through continual practice in language control - may impact cognitive functions, as well as relevant aspects of brain function and structure. The present review aimed to bring together findings on the relationship between bilingualism and domain-general cognitive functions from a neural perspective. The final sample included 210 studies, covering findings regarding neural responses to bilingual language control and/or domain-general cognitive tasks, as well as findings regarding effects of bilingualism on non-task-related brain function and brain structure. The evidence indicates that a) bilingual language control likely entails neural mechanisms responsible for domain-general cognitive functions; b) bilingual experiences impact neural responses to domain-general cognitive functions; and c) bilingual experiences impact non-task-related brain function (both resting-state and metabolic function) as well as aspects of brain structure (both macrostructure and microstructure), each of which may in turn impact mental processes, including domain-general cognitive functions. Such functional and structural neuroplasticity associated with bilingualism may contribute to both cognitive and neural reserves, producing benefits across the lifespan.

Are language skills related to structural features in Broca's and Wernicke's area?

This study used structural magnetic resonance imaging to examine whether specific anatomical features of Broca's and Wernicke's areas are related to language functions in typically developing older subjects with no specific language expertize. Data from 231 subjects from the Zurich LHAB-study are used for this study. For these subjects, we obtained several psychometric measures from which we calculated performance measures reflecting specific psychological functions (language comprehension, verbal fluency, perceptual speed, visual memory, recognition of regularities, and logical thinking). From the MRI measurements, we calculated the cortical thickness and cortical surface of Broca's and Wernicke's areas. Applying multiple regression analyses, we identified a moderately strong relationship between language comprehension and the brain metrics from Broca's and Wernicke's areas and showed that approximately 10% of the variance in language comprehension performance is explained by the linear combination of all perisylvian brain metrics. The other psychological functions (verbal fluency, perceptual speed, visual memory, recognition of regularities, and logical thinking) are not related to these brain metrics. Subsequent detailed analyses revealed that the cortical thickness of Wernicke's area, in particular, contributed most to this structure-function relationship. The better performance in the language comprehension tests was related to a thicker cortex in Wernicke's area. Thus, this study demonstrates a structure-function relationship between the anatomical features of the perisylvian language areas and language comprehension, suggesting that particular anatomical features are associated with better language performance.