Brain circuit for cognitive control is shared by task and language switching

Controlling multiple languages during speech production is believed to rely on functional mechanisms that are (at least partly) shared with domain-general cognitive control in early, highly proficient bilinguals. Recent neuroimaging results have indeed suggested a certain degree of neural overlap between language control and nonverbal cognitive control in bilinguals. However, this evidence is only indirect. Direct evidence for neural overlap between language control and nonverbal cognitive control can only be provided if two prerequisites are met: Language control and nonverbal cognitive control should be compared within the same participants, and the task requirements of both conditions should be closely matched. To provide such direct evidence for the first time, we used fMRI to examine the overlap in brain activation between switch-specific activity in a linguistic switching task and a closely matched nonlinguistic switching task, within participants, in early, highly proficient Spanish-Basque bilinguals. The current findings provide direct evidence that, in these bilinguals, highly similar brain circuits are involved in language control and domaingeneral cognitive control

Neural basis of language switching in the brain: fMRI evidence from Korean–Chinese early bilinguals

AbstractUsing fMRI, we conducted two types of property generation task that involved language switching, with early bilingual speakers of Korean and Chinese. The first is a more conventional task in which a single language (L1 or L2) was used within each trial, but switched randomly from trial to trial. The other consists of a novel experimental design where language switching happens within each trial, alternating in the direction of the L1/L2 translation required. Our findings support a recently introduced cognitive model, the ‘hodological’ view of language switching proposed by Moritz-Gasser and Duffau. The nodes of a distributed neural network that this model proposes are consistent with the informative regions that we extracted in this study, using both GLM methods and Multivariate Pattern Analyses: the supplementary motor area, caudate, supramarginal gyrus and fusiform gyrus and other cortical areas

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

Emerging methods for conceptual modelling in neuroimaging

Some open theoretical questions are addressed on how the mind and brain represent and process concepts, particularly as they are instantiated in particular human languages. Recordings of neuroimaging data should provide a suitable empirical basis for investigating this topic, but the complexity and variety of language demands appropriate data-driven approaches. In this review we argue for a particular suite of methodologies, based on multivariate classification techniques which have proven to be powerful tools for distinguishing neural and cognitive states in fMRI. A combination of larger scale neuroimaging studies are introduced with different monolingual and bilingual populations, and hybrid computational analyses that use encoded implementations of existing theories of conceptual organisation to probe those data. We develop a suite of methodologies that holds the promise of being able to holistically elicit, record and model neural processing during language comprehension and production

White matter and task-switching in young adults: A Diffusion Tensor Imaging study

The capacity to flexibly switch between different task rules has been previously associated with distributed fronto-parietal networks, predominantly in the left hemisphere for phasic switching sub-processes, and in the right hemisphere for more tonic aspects of task-switching, such as rule maintenance and management. It is thus likely that the white matter (WM) connectivity between these regions is critical in sustaining the flexibility required by task-switching. This study examined the relationship between WM microstructure in young adults and task-switching performance in different paradigms: classical shape-color, spatial and grammatical tasks. The main results showed an association between WM integrity in anterior portions of the corpus callosum (genu and body) and a sustained measure of task-switching performance. In particular, a higher fractional anisotropy and a lower radial diffusivity in these WM regions were associated with smaller mixing costs both in the spatial task-switching paradigm and in the shape-color one, as confirmed by a conjunction analysis. No association was found with behavioral measures obtained in the grammatical task-switching paradigm. The switch costs, a measure of phasic switching processes, were not correlated with WM microstructure in any task. This study shows that a more efficient inter-hemispheric connectivity within the frontal lobes favors sustained task-switching processes, especially with task contexts embedding non-verbal components

The representation of language in bilinguals : neural overlap as a function of modality, representational level, language proficiency and context

status: accepte

Inference of Language Functional Network in Healthy, Cancerous and Bilingual Brains by fMRI and Network Modeling

We study the underlying mechanism by which language processing occurs in the human brain using inference methods on functional magnetic resonance imaging data. The data analyzed stems from several cohorts of subjects; a monolingual group, a bilingual group, a healthy control group and one diseased case. We applied a complex statistical inference pipeline to determine the network structure of brain components involved with language. This healthy network reveals a fully connected triangular relationship between the pre-Supplementary Motor Area (pre-SMA), the Broca\u27s Area (BA), and the ventral Pre-Motor Area (PreMA) in the left hemisphere. This triangle\u27\u27 shows consistently in all the healthy subjects (100%) we analyzed regardless of their mono- or multi-lingual status. In addition, we found that Wernicke\u27s Area (WA) on the left hemisphere connects with BA and PreMA to form a V\u27\u27 shape connectivity across 75% of the monolinguals, 50% of the bilinguals speaking a second language and 100% of the bilinguals speaking their native language. By comparing the quantified link weights, we found that the strongest link is between BA and PreMA, followed by pre-SMA and PreMA, and then pre-SMA and BA. This is consistent for all healthy subjects (p \u3c 0.05). Furthermore, we conducted a k-core analysis testing the resiliency of subnetworks in the three groups. Our results show that nodes in the three triangle areas belong mostly to the maximum shell, whereas WA populates mostly in the lower shell, consistently across the data. In a separate study, we describe frontal language reorganization in a 57-year-old right-handed patient with a low-grade left frontotemporal insular glioma. Pre-operative fMRI revealed robust activation in left WA and in the right BA. Intra-operative cortical stimulation of the left inferior frontal gyrus and adjacent cortices elicited no speech deficits, and gross total resection including the expected location of BA resulted in no speech impairment. Our network model found that the right homologue of the BA in this patient functionally connected to the same areas as the left BA in a typical healthy control. As opposed to the functional connection of the left BA in a healthy brain, the right BA did not connect directly with the left WA, but connected indirectly, mediated by the pre-SMA and preMA. In addition, the trans-located BA and WA moves from the lower k shell to the maximum shell during the recovery of the surgery. This case illustrates that pre-surgical fMRI can be used to identify atypical hemispheric language reorganization in the presence of a brain tumor and that network theory can help understand the underlying structure behind functional reorganization

Parametric inference for functional information mapping

An increasing trend in functional MRI experiments involves discriminating between experimental conditions on the basis of fine-grained spatial patterns extending across many voxels. Typically, these approaches have used randomized resampling to derive inferences. Here, we introduce an analytical method for drawing inferences from multivoxel patterns. This approach extends the general linear model to the multivoxel case resulting in a variant of the Mahalanobis distance statistic which can be evaluated on the x2 distribution. We apply this parametric inference to a single-subject fMRI dataset and consider how the approach is both computationally more efficient and more sensitive than resampling inference

Bilingualism across the lifespan: Neuroanatomical correlates

187 p.Recently, an increasing number of studies addressing the neuroanatomical bases of bilingualism have appeared (Garcia-Penton et al., 2016). However, the results are variable and in sorne cases conflicting,and consequen y it is still a matter of debate how brain changes due to bilingual experience.The present study will try to shed sorne light on the field by adding fresh new evidence testing children and elderly high proficient early Spanish-Basque bilinguals, two very typologically different languages . The proposed work will use large-scale brain-mapping techniques to explore the relationship between structure and function, as a more holistic and realistic approach to understanding comprehensively the neural bases of bilingualism. This integrational perspectiva will also promote convergent evidence about the specialization and integration of the neural networks in bilingualism. As such, this work will study the organisation of brain networks,either due to slow changes in brain areas and their wiring (namely, the structural plasticity), or due to fast modulation of their interactions (namely, functional plasticity).This thesis will employ Functional Magnetic Resonance lmaging (fMRI) during resting-state in combination with Diffusion-Weighted Magnetic Resonance lmaging (DW-MRI) to determine functional and structural connectivity, respectively. Both techniques will make it possible to model the large-scale structural/functional connectivity maps by means of a high­ dimensional parcellation of the grey matter (GM) in the brain instead of limiting analysis to specific regions of interest, as done in previous studies. A 30 high resolution whole-head anatomical sean (T1-MRI) will be used in order to generate GM parcellations employed in the connectivity analysis, but also to identify regional differential structural patterns associated with bilingualism, using voxel-based and surface-based analyses of the GM. Network­ based statistics (Zalesky et al., 2010) and graph theoretical approaches (Latora & Marchiori, 2001; Rubinov and Spoms, 201O) will be employed to investigate differences between groups in connectiv ity pattems, by isolating sets of regions interconnected differently between groups, and in topological properties of the networks, by measuring global/local efficiency. The main findings of this research on bilingualism across different groups of age (childhood and elderly) suggested that structural brain plasticity related to bilingualism was so small, unstable, subtle and transient that it was very difficult to detect even in lifelong bilinguals. A fact that is consisten! with the curren! ambiguous picture in bilingualism studies (Garcia-Pentón et al.,2016; see also others, Baum & Titone,2014; Costa,& Sebastián-Gallés , 2014; Li, Legault, & Litcofsky, 2014; Paap et al., 2015; de Bruin et al., 2015a). However, this study suggested that even when the brain did not display focal brain differences (i.e. did not show any specialization) it could still show differences at the global level. Specifically,the evidence draws attention that lifelong bilingualism could pinpoint a gain toward a better neural reserve in aging due to the whole-network graph-efficiency observed in elderly lifelono bilinouals