BIL&GIN: A neuroimaging, cognitive, behavioral, and genetic database for the study of human brain lateralization.

We report on a database, named BIL&GIN, designed for investigating the cognitive, behavioral, genetic, and brain morphological/functional correlates of hemispheric specialization. The database contains records from a sample of 453 adult participants enriched in left-handers (45%, N=205) as compared to the general population. For each subject, socio-demographic data, hand and eye laterality, family handedness, and cognitive abilities in the language, motor, visuo-spatial, and numerical domains have been recorded. T1-MRI and DTI data were also acquired, as well as resting-state functional MRI. Task-evoked functional MRI was performed in a sub-sample of 303 subjects (157 left-handers) using a customized functional battery of 16 cognitive tasks exploring the same three cognitive domains. Performances at the tasks executed in the magnet as well as post-acquisition debriefing were recorded. A saliva sample was obtained from the subjects of this sub-sample from which DNA was extracted. The BIL&GIN contains results of imaging data processing for each subject, namely maps of tissue (GM, WM, CSF) probability, cortical thickness, cortical surface, and diffusion parameters as well as regional values of these phenotypes for regions of both AAL and FreeSurfer parcellations. For the subjects who underwent FMRI, individual SPM contrast maps for each of the 8 runs were also calculated and included in the database, as well as corresponding BOLD variations in ROIs of the AAL and AICHA atlases, and Wilke's hemispheric functional lateralization index. The BIL&GIN data sharing is based on a collaborative model.

What is right-hemisphere contribution to phonological, lexico-semantic, and sentence processing? Insights from a meta-analysis.

To evaluate the relative role of left and right hemispheres (RH) and describe the functional anatomy of RH during ortholinguistic tasks, we re-analyzed the 128 papers of a former left-hemisphere (LH) meta-analysis (Vigneau et al., 2006). Of these, 59 articles reported RH participation, providing 105 RH language contrasts including 218 peaks compared to 728 on the left, a proportion reflecting the LH language dominance. To describe inter-hemispheric interactions, in each of the language contrasts involving both hemispheres, we distinguished between unilateral and bilateral peaks, i.e. having homotopic activation in the LH in the same contrast. We also calculated the proportion of bilateral peaks in the LH. While the majority of LH peaks were unilateral (79%), a reversed pattern was observed in the RH; this demonstrates that, in contrast to the LH, the RH works in an inter-hemispheric manner. To analyze the regional pattern of RH participation, these unilateral and bilateral peaks were spatially clustered for each language component. Most RH phonological clusters corresponded to bilateral recruitment of auditory and motor cortices. Notably, the motor representation of the mouth and phonological working memory areas were exclusively left-lateralized, supporting the idea that the RH does not host phonological representations. Right frontal participation was not specific for the language component involved and appeared related to the recruitment of attentional and working memory areas. The fact that RH participation during lexico-semantic tasks was limited to these executive activations is compatible with the hypothesis that active inhibition is exerted from the LH during the processing of meaning. Only during sentence/text processing tasks a specific unilateral RH-temporal involvement was noted, likely related to context processing. These results are consistent with split-brain studies that found that the RH has a limited lexicon, with no phonological abilities but active involvement in the processing of context.

The neural correlates of highly iconic structures and topographic discourse in French Sign Language as observed in six hearing native signers.

"Highly iconic" structures in Sign Language enable a narrator to act, switch characters, describe objects, or report actions in four-dimensions. This group of linguistic structures has no real spoken-language equivalent. Topographical descriptions are also achieved in a sign-language specific manner via the use of signing-space and spatial-classifier signs. We used functional magnetic resonance imaging (fMRI) to compare the neural correlates of topographic discourse and highly iconic structures in French Sign Language (LSF) in six hearing native signers, children of deaf adults (CODAs), and six LSF-naïve monolinguals. LSF materials consisted of videos of a lecture excerpt signed without spatially organized discourse or highly iconic structures (Lect LSF), a tale signed using highly iconic structures (Tale LSF), and a topographical description using a diagrammatic format and spatial-classifier signs (Topo LSF). We also presented texts in spoken French (Lect French, Tale French, Topo French) to all participants. With both languages, the Topo texts activated several different regions that are involved in mental navigation and spatial working memory. No specific correlate of LSF spatial discourse was evidenced. The same regions were more activated during Tale LSF than Lect LSF in CODAs, but not in monolinguals, in line with the presence of signing-space structure in both conditions. Motion processing areas and parts of the fusiform gyrus and precuneus were more active during Tale LSF in CODAs; no such effect was observed with French or in LSF-naïve monolinguals. These effects may be associated with perspective-taking and acting during personal transfers.

Impact of modality and linguistic complexity during reading and listening tasks.

Reading and understanding speech are usually considered as different manifestations of a single cognitive ability, that of language. In this study, we were interested in characterizing the specific contributions of input modality and linguistic complexity on the neural networks involved when subjects understand language. We conducted an fMRI study during which 10 right-handed male subjects had to read and listen to words, sentences and texts in different runs. By comparing reading to listening tasks, we were able to show that the cerebral regions specifically recruited by a given modality were circumscribed to unimodal and associative unimodal cortices associated with the task, indicating that higher cognitive processes required by the task may be common to both modalities. Such cognitive processes involved a common phonological network as well as lexico-semantic activations as revealed by the conjunction between all reading and listening tasks. The restriction of modality-specific regions to their corresponding unimodal cortices was replicated when looking at brain areas showing a greater increase during the comprehension of more complex linguistic units than words (such as sentences and texts) for each modality. Finally, we discuss the possible roles of regions showing pure effect of linguistic complexity, such as the anterior part of the superior temporal gyrus and the ventro-posterior part of the middle temporal gyrus that were activated for sentences and texts but not for isolated words, as well as a text-specific region found in the left posterior STS.

Meta-analyzing left hemisphere language areas: phonology, semantics, and sentence processing.

The advent of functional neuroimaging has allowed tremendous advances in our understanding of brain-language relationships, in addition to generating substantial empirical data on this subject in the form of thousands of activation peak coordinates reported in a decade of language studies. We performed a large-scale meta-analysis of this literature, aimed at defining the composition of the phonological, semantic, and sentence processing networks in the frontal, temporal, and inferior parietal regions of the left cerebral hemisphere. For each of these language components, activation peaks issued from relevant component-specific contrasts were submitted to a spatial clustering algorithm, which gathered activation peaks on the basis of their relative distance in the MNI space. From a sample of 730 activation peaks extracted from 129 scientific reports selected among 260, we isolated 30 activation clusters, defining the functional fields constituting three distributed networks of frontal and temporal areas and revealing the functional organization of the left hemisphere for language. The functional role of each activation cluster is discussed based on the nature of the tasks in which it was involved. This meta-analysis sheds light on several contemporary issues, notably on the fine-scale functional architecture of the inferior frontal gyrus for phonological and semantic processing, the evidence for an elementary audio-motor loop involved in both comprehension and production of syllables including the primary auditory areas and the motor mouth area, evidence of areas of overlap between phonological and semantic processing, in particular at the location of the selective human voice area that was the seat of partial overlap of the three language components, the evidence of a cortical area in the pars opercularis of the inferior frontal gyrus dedicated to syntactic processing and in the posterior part of the superior temporal gyrus a region selectively activated by sentence and text processing, and the hypothesis that different working memory perception-actions loops are identifiable for the different language components. These results argue for large-scale architecture networks rather than modular organization of language in the left hemisphere.

Word and non-word reading: what role for the Visual Word Form Area?

The putative role of the so-called Visual Word Form Area (VWFA) during reading remains under debate. For some authors, this region is specifically involved in a pre-lexical processing of words and pseudowords, whereas such specificity is challenged by others given the VWFA involvement during both non-word reading and word listening. Here, we further investigated this issue, measuring BOLD variations and their lateralization with fMRI during word and non-word reading, in order to evaluate the lexicality effect, and during reading and listening of words, in order to evaluate the impact of stimulus delivery modality on word processing networks. Region of interest (ROI) analysis was first performed in three target areas: 1-VWFA as defined by a meta-analysis of the word reading literature, 2-a middle temporal area (T2) found co-activated by both word reading and listening, 3-an inferior occipital area (OI) belonging to the unimodal visual cortex of the inferior occipital gyrus. VWFA activity was found not different between word and non-word reading but was more leftward lateralized during word reading due to a reduction of activity in the VWFA right counterpart. A similar larger leftward lateralization during word reading was also uncovered in the T2 ROI but was related to a larger left side activity. Such a lexicality effect was not observed in the OI ROI. By contrast, BOLD increases during listening were restricted to the left VWFA and T2 ROIs. Voxel-based analysis (SPM99) showed that semantic areas were more active during word than non-word reading and co-activated by both reading and listening, exhibiting a left lateralized activity in all tasks. These results indicate that the left VWFA would be the place where visual and verbal representations bind under the control of left semantic areas.

[A case of unilateral elastosis with cysts and comedones. Favre-Racouchot syndrome]. / Un cas unilatéral d'élastose avec kystes et comédons de Favre et Racouchot.

INTRODUCTION: Cutaneous elastosis with cysts and comedones (Favre-Racouchot) is one of the oldest known manifestations of helioderma. Both sides of the face are usually involved symmetrically. CASE REPORT: We observed a 65-year-old woman with extremely severe Favre-Racouchot disease localized exclusively on the left side of the face. The diagnosis of elastosis with cysts and comedones was confirmed histologically. This elastosis with cysts and comedones was associated with spasms of the hemiface treated with injections of botulinic toxin. This association was fortuitous and we retained actinic irradiation as the causal agent in this woman who had worked for 15 years in the same room. The elastosis occurred on the side of the face which had been continuously exposed at the same orientation to the window. COMMENTS: This original observation is similar to cases where facial exposure to artificial light or sunlight is asymmetrical, leading to a higher incidence of lesions on one side of the face: colloid milium, actinic keratosis, Dubreuilh melanoma (malignant lentigo) or simple helioderma. The asymmetrical nature of the actinic lesions is often related to automobile driving. This case was particular since it demonstrated that Favre-Racouchot elastosis with cysts and comedones is due to actinic irradiation and not to skin aging.