Diffusion tensor imaging of dorsal stream language areas in patients with post-stroke aphasia

Background Aphasia complicating stroke occurs due to language deficits that decrease communication abilities and functional independence. Our study aims to assess fractional anisotropy (FA) and mean diffusivity (MD) parameters of diffusion tensor imaging (DTI) of the dorsal stream language areas in patients with post-stroke aphasia. It was conducted on 27 patients with post-stroke aphasia and 27 age- and sex-matched controls who underwent DTI of the brain. FA and MD values of Broca's area (BA), Wernick's area (WA), superior longitudinal fasciculus (SLF), and arcuate fasciculus (AF), and number of tract fibers (TF) of AF and SLF were calculated. Results were correlated with National Institutes of Health Stroke Scale (NIHSS), Arabic version of Comprehensive Aphasia Test (Arabic CAT), and Mansoura Arabic Screening Aphasia Test (MASAT). Results FA of AF and SLF in patients was significantly lower (P = 0.001) than controls. MD of AF and SLF in patients was significantly higher (P = 0.001) than controls. The mean volume TF of AF and SLF in patients was significantly (P = 0.001) lower than the mean volume in controls for AF and SLF. FA cutoff for AF was 0.34 and for SLF, it was 0.35 with sensitivity, specificity, and accuracy (85.2%, 62.1%, 73.2%) for AF, (74.1%, 69%, 71.4%) for SLF, respectively. MD cutoff value for AF was 0.87, and 0.84 for SLF with sensitivity, specificity, and accuracy (63%, 72.4%, 67.8%) for AF, (81.5%, 79.3%, 80.4%) for SLF, respectively. Cutoff TF of AF was 1728 and for SLF it was 601 with sensitivity, specificity, and accuracy (88.9%, 72.4%, 80.4%) for AF and (85.2%, 85.2%, 78.6%) for SLF, respectively. Conclusions DTI is a non-invasive promising method that can be used to assess language areas in patients with post-stroke aphasia.

Information flow across the cortical timescales hierarchy during narrative comprehension

When listening to spoken narratives, we must integrate information over multiple, concurrent timescales, building up from words to phrases to sentences to a coherent narrative. Recent evidence suggests that the brain relies on a chain of hierarchically organized areas with increasing temporal receptive windows to process naturalistic narratives. In this study, we use inter-subject functional connectivity to reveal a stimulus-driven information flow along the cortical hierarchy. Using cross-correlation analysis to estimate the time lags between six functional networks, we found a fixed temporal sequence of information flow, starting in early auditory areas, followed language areas, the attention network, and lastly the default mode network. This gradient is consistent across eight distinct stories but absent in resting-state and scrambled story data, indicating that the lag gradient reflects the construction of narrative features. Finally, we simulate a variety of narrative integration models and demonstrate that nested narrative structure along with the gradual accumulation of information within the boundaries of linguistic events at each level of the processing hierarchy is sufficient to reproduce the lag gradient. Taken together, this study provides a computational framework for how information flows along the cortical hierarchy during narrative comprehension.

Impairment and Plasticity of Language-Related White Matter in Patients With Brain Arteriovenous Malformations

Background and Purpose: Language dysfunction is rarely seen in patients with unruptured brain arteriovenous malformation (AVM) albeit the AVM nidus involving language areas, which provides a unique disease model to study language reorganization. The objective of this study was to investigate the impairment and reorganization patterns and characteristics of language-related white matter in AVMs located at different brain areas. Methods: Thirty-three patients with AVMs involving language areas were prospectively enrolled. Patients were categorized into 3 groups according to the lesion locations: the frontal (14 patients), temporal (15 patients), and parietal groups (4 patients). Thirty age- and sex-matched healthy controls were enrolled as comparison. All participants underwent diffusion tensor imaging scans, and automated fiber quantification method was applied to quantitatively study the difference of segmented language-related white matter connectivity between 3 AVM groups and control group. Results: Language functions were normal in all subjects according to Western Aphasia Battery test. In the frontal group, fractional anisotropy (FA) value decreased in the left arcuate fascicle and increased in left superior longitudinal fasciculus and uncinate fascicle; in the temporal group, FA values decreased in left inferior fronto-occipital fascicle and inferior longitudinal fascicle and increased in right anterior thalamic radiation and uncinate fascicle; in the parietal group, FA values decreased in left arcuate fascicle and inferior longitudinal fascicle and increased in bilateral anterior thalamic radiations and uncinate fascicles and right inferior fronto-occipital fascicle. In fascicles with decreased FA values, the increase of radial diffusivity was common, and fascicles with increased FA values usually presented along with increased axial diffusivity values. Conclusions: Remodeling of language-related white matter occurs when traditional language areas are involved by AVM nidus, and its reorganization patterns vary with locations of AVM nidus. Fascicle impairment is mainly caused by the myelin deficits, and its plasticity may be dominated by the axon remodeling procedure.

A Data-Based Approach for Selecting Pre- and Intra-Operative Language Mapping Tasks

Background: Pre- and intra-operative language mapping in neurosurgery patients frequently involves an object naming task. The choice of the optimal object naming paradigm remains challenging due to lack of normative data and standardization in mapping practices. The aim of this study was to identify object naming paradigms that robustly and consistently activate classical language regions and could therefore be used to improve the sensitivity of language mapping in brain tumor and epilepsy patients.Methods: Functional magnetic resonance imaging (fMRI) data from two independent groups of healthy controls (total = 79) were used to generate threshold-weighted voxel-based consistency maps. This novel approach allowed us to compare inter-subject consistency of activation for naming single objects in the visual and auditory modality and naming two objects in a phrase or a sentence.Results: We found that the consistency of activation in language regions was greater for naming two objects per picture than one object per picture, even when controlling for the number of names produced in 5 s.Conclusion: More consistent activation in language areas for naming two objects compared to one object suggests that two-object naming tasks may be more suitable for delimiting language eloquent regions with pre- and intra-operative language testing. More broadly, we propose that the functional specificity of brain mapping paradigms for a whole range of different linguistic and non-linguistic functions could be enhanced by referring to databased models of inter-subject consistency and variability in typical and atypical brain responses.

Personality and territoriality in theory and in Belgium

Language policy debates regularly refer to the principles of personality and territoriality. Yet the precise meaning of these principles remains unclear. In this contribution, I conceptualize these principles as poles of a continuum between official bilingualism (instantiating the personality principle) and official unilingualism (exemplifying the territoriality principle), with a mixed regime in between (which grants a certain territorial primacy to a language, but allows exceptions based on linguistic affiliation). The question of the determination of particular points on the continuum cannot be separated from the metaterritorial question of the boundaries of the units within which those principles apply. Application of this ‘continuum model’ to Belgium draws attention to three language-political regimes. The first invokes a strict personality principle (Brussels). The second follows the strict territoriality principle (almost all municipalities in Flanders and Wallonia). The third is a mixed regime (a total of 27 ‘municipalities with facilities’ where one language enjoys primacy but speakers of another language enjoy certain linguistic ‘facilities’). The article also analyses the manner in which these regimes were historically established in Belgium in combination with a delineation of the language border and the division of the country into four language areas.

P.066 Hemispheric Reorganization of Functional Language Networks Following Neonatal Stroke Supports Language Outcome

Background: Neonatal Arterial Ischemic Stroke (NAIS) is a common form of paediatric stroke often affecting classical language areas. The post-stroke reorganization of functional language networks may provide insight into later-emerging language deficits and may help to identify at-risk children with NAIS. Methods: A cross-sectional study of fourteen children with left (n=8; 2M; 11.1±2.2 years) or right (n=6; 3M; 12.4±4 years) middle cerebral artery (MCA) NAIS, as well as seven neurotypical children (5M; 13.4±2.7 years), was conducted. Children listened to correct/incorrect syntactic sentences while MEG was recorded, and task-related functional connectivity in the time window and frequency band of interest was determined. Language outcomes were assessed using a battery of neuropsychological tests. Results: A network-based analysis of syntactic language processing (4-7 Hz, 1.2-1.4s) revealed a dysfunctional bilateral frontal-temporal network involving language areas in patients (p=0.01). Patients with right-MCA stroke exhibited a positive correlation between left hemispheric connectivity and measures of language skill (p<0.01), resembling the neurotypical children. In left-MCA stroke patients, greater bilateral connectivity or right laterality in the language network is correlated with good outcome (p<0.05). Conclusions: Depending on the hemispheric location of stroke, certain patterns of language network reorganization may account for impairments in a bilateral frontal-temporal language subnetwork and support language outcome.

Clinical Speech fMRI in Children and Adolescents

Purpose In patients with drug-resistant focal epilepsy, surgical resection is often the only treatment option to achieve long-term seizure control. Prior to brain surgery involving potential language areas, identification of hemispheric language dominance is crucial. Our group developed and validated a functional magnetic resonance imaging (fMRI) battery of four pediatric language tasks. The present study aimed at optimizing fMRI data acquisition and analysis using these tasks. Methods We retrospectively analyzed speech fMRI examinations of 114 neuropediatric patients (age range 5.8–17.8 years) who were examined prior to possible epilepsy surgery. In order to evaluate hemispheric language dominance, 1–4 language tasks (vowel identification task VIT, word-chain task WCT, beep-story task BST, synonym task SYT) were measured. Results Language dominance was classified using fMRI activation in the 13 validly lateralizing ROIs (VLR) in frontal, temporal and parietal lobes and cerebellum of the recent validation study from our group: 47/114 patients were classified as left-dominant, 34/114 as bilateral and 6/114 as right-dominant. In an attempt to enlarge the set of VLR, we then compared for each task agreement of these ROI activations with the classified language dominance. We found four additional task-specific ROIs showing concordant activation and activation in ≥ 10 sessions, which we termed validly lateralizing (VLRnew). The new VLRs were: for VIT the temporal language area and for SYT the middle frontal gyrus, the intraparietal sulcus and cerebellum. Finally, in order to find the optimal sequence of measuring the different tasks, we analyzed the success rates of single tasks and all possible task combinations. The sequence 1) VIT 2) WCT 3) BST 4) SYT was identified as the optimal sequence, yielding the highest chance to obtain reliable results even when the fMRI examination has to be stopped, e.g., due to lack of cooperation. Conclusion Our suggested task order together with the enlarged set of VLRnew may contribute to optimize pediatric speech fMRI in a clinical setting.

Training institutes and training in official statistics in Africa: An overview

The training offer of official statistics in statistical training institutes has been constantly evolving as it adapts to the statistical environment and technological developments. Based on a literature review and the mobilisation of curricula and programmes offered by statistical training centres in Africa, this paper presents the current situation of training in official statistics as well as the challenges to be faced. Despite harmonisation efforts, there are still differences between language areas and training types. Engineer and vocational statistical training are better suited to the needs of National Statistical Institutes than university training. It is essential that the training of statisticians is strategically thought out so that they can be reactive and dynamic in the face of changes and upheavals they will be confronted with in the context of data revolution and big data. Their training should reinforce the statistical literacy dimension with a view to reducing the gap between producers and users.

Large-scale differences in functional organization of left- and right-handed individuals using whole-brain, data-driven analysis of connectivity

Handedness influences differences in lateralization of language areas as well as dominance of motor and somatosensory cortices. However, differences in whole brain functional organization due to handedness have been relatively understudied beyond pre-specified networks of interest. Functional connectivity offers the ability to unravel differences in the functional organization of the whole brain. Here, we compared connectivity profiles of left- and right-handed individuals using data-driven parcellations of the whole brain. We explored differences in connectivity profiles of previously established regions of interest, and showed functional organization differences between primarily left- and primarily right-handed individuals in the motor, somatosensory, and language areas using functional connectivity. We then proceeded to investigate these differences in the whole brain and found that the functional organization of left- and right-handed individuals are not specific to regions of interest. In particular, we found that connections between and within-hemispheres and the cerebellum show distinct patterns of connectivity. Together these results shed light on regions of the brain beyond those traditionally explored that contribute to differences in the functional organization of left- and right-handed individuals.

Complementary hemispheric lateralization of language and social processing in the human brain

Humans have a unique ability to use language for social communication. The neural architecture for language comprehension and production may have emerged in the brain areas that were originally involved in social cognition. Here we directly tested the fundamental link between language and social processing using functional MRI data from over 1000 human subjects. Cortical activations in language and social tasks showed a striking similarity with a complementary hemispheric lateralization; within core language areas, the activations were left-lateralized in the language task and right-lateralized in the social task. Outside these areas, the activations were left-lateralized in both tasks, perhaps indicating multimodal integration of social and communicative information. Our findings could have important implications in understanding neurocognitive mechanisms of social disorders such as autism.