Brain, language, and handedness: a family affair

The left planum temporale is a marker of left hemisphere language specialization. We investigated the effect of individual handedness and familial sinistrality on left planum temporale surface area and found the size is reduced in proportion with the number of left-handed immediate family members and is lowest when one's mother is left-handed. This reduction is independent of an individual's handedness or sex and has no counterpart in the right hemisphere

Heteromodal brain areas common to production, listening and reading tasks at the word Level: an fMRI study of 144 right-handers from the BIL&GIN

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The Skin-Conductance Component of Error Correction in a Logical Reasoning Task

La Réponse ÉlectroDermale (RED) a été mesurée à deux reprises chez les mêmes sujets qui réalisaient une tâche de logique déductive, d’abord en commettant une erreur de raisonnement et ensuite, après un apprentissage, soit en répondant correctement, soit en persévérant dans l’erreur selon les sujets. La RED s’est accrue entre les deux sessions et était significativement plus importante chez les sujets qui corrigeaient leur erreur initiale de raisonnement que chez les autres, révélant la forte interconnexion entre le raisonnement logique et les indices d’états somatiques impliqués dans l’émotion. Cela corrobore les résultats d’études antérieures d’imagerie cérébrale réalisées dans notre groupe et indiquant que l’accès à la logique déductive dépend du cortex préfrontal ventromédian droit dont on connaît l’implication dans la représentation afférente de la RED et dans l’intégration émotion-cognition.Skin Conductance Responses (SCRs) were measured in a deductive logic task performed twice by the same subjects, first making reasoning errors and then, after training, providing logical responses or making errors again, depending on the subject. SCRs increased between the two sessions and were significantly higher in the subjects who corrected their reasoning errors than in those that did not, showing the strong interplay between logical reasoning and indices of somatic states involved in emotion. This fits well with the results of previous brain imaging studies from our group showing that access to deductive logic depends on a right ventromedial prefrontal area involved in SCRs afferent representation and emotion-cognition integration

Effects of blood pressure lowering on cerebral white matter hyperintensities in patients with stroke: the PROGRESS (Perindopril Protection Against Recurrent Stroke Study) Magnetic Resonance Imaging Substudy.: The PROGRESS MRI Substudy.

International audienceBACKGROUND: The prevalence of white matter hyperintensities (WMHs) detected on cerebral MRI is associated with hypertension, but it is not known whether blood pressure lowering can arrest their progression. We report here the results of an MRI substudy of PROGRESS (Perindopril Protection Against Recurrent Stroke Study), a randomized trial of blood pressure lowering in subjects with cerebrovascular disease. METHODS AND RESULTS: The substudy comprised 192 participants who had a cerebral MRI both at baseline and after a mean follow-up time of 36 months (SD=6.0 months). At the first MRI, WMHs were graded with a visual rating scale from A (no WMH) to D (severe WMH). Participants were assigned to a combination of perindopril plus indapamide (or their placebos; 58%) or to single therapy with perindopril (or placebo). At the time of the second MRI, the blood pressure reduction in the active arm compared with the placebo arm was 11.2 mm Hg for systolic blood pressure and 4.3 mm Hg for diastolic blood pressure. Twenty-four subjects (12.5%) developed new WMHs at follow-up. The risk of new WMH was reduced by 43% (95% CI -7% to 89%) in the active treatment group compared with the placebo group (P=0.17). The mean total volume of new WMHs was significantly reduced in the active treatment group (0.4 mm3 [SE=0.8]) compared with the placebo group (2.0 mm3 [SE=0.7]; P=0.012). This difference was greatest for patients with severe WMH at entry, 0.0 mm3 (SE=0) in the active treatment group versus 7.6 mm3 (SE=1.0) in the placebo group (P<0.0001). CONCLUSIONS: These results indicate that an active blood pressure-lowering regimen stopped or delayed the progression of WMHs in patients with cerebrovascular disease

Cortical Terminations of the Inferior Fronto-Occipital and Uncinate Fasciculi: Anatomical Stem-Based Virtual Dissection

International audienceWe combined the neuroanatomists' approach of defining a fascicle as all fibers passing through its compact stem with diffusion-weighted tractography to investigate the cortical terminations of two association tracts, the inferior fronto-occipital fasciculus (IFOF) and the uncinate fasciculus (UF), which have recently been implicated in the ventral language circuitry. The aim was to provide a detailed and quantitative description of their terminations in 60 healthy subjects and to do so to apply an anatomical stem-based virtual dissection, mimicking classical post-mortem dissection, to extract with minimal a priori the IFOF and UF from tractography datasets. In both tracts, we consistently observed more extensive termination territories than their conventional definitions, within the middle and superior frontal, superior parietal and angular gyri for the IFOF and the middle frontal gyrus and superior, middle and inferior temporal gyri beyond the temporal pole for the UF. We revealed new insights regarding the internal organization of these tracts by investigating for the first time the frequency, distribution and hemispheric asymmetry of their terminations. Interestingly, we observed a dissociation between the lateral right-lateralized and medial left-lateralized fronto-occipital branches of the IFOF. In the UF, we observed a rightward lateralization of the orbito-frontal and temporal branches. We revealed a more detailed map of the terminations of these fiber pathways that will enable greater specificity for correlating with diseased populations and other behavioral measures. The limitations of the diffusion tensor model in this study are also discussed. We conclude that anatomical stem-based virtual dissection with diffusion tractography is a fruitful method for studying the structural anatomy of the human white matter pathways

Cerebral activations during number multiplication and comparison: a PET study

Positron emission tomography was used to examine the cerebral networks underlying number comparison and multiplication in eight normal volunteers. Cerebral blood flow was measured within anatomical regions of interest defined in each subject using magnetic resonance imaging. Three conditions were used: rest with eyes closed, mental multiplication of pairs of arabic digits and larger-smaller comparison of the same pairs. Both multiplication and comparison activated the left and right lateral occipital cortices, the left precentral gyrus, and the supplementary motor area. Beyond these common activations, multiplication activated also the left and right inferior parietal gyri, the left fusiform and lingual gyri, and the right cuneus. Relative to comparison, multiplication also yielded superior activity in the left lenticular nucleus and in Brodmann's area 8, and induced a hemispheric asymmetry in the activation of the precentral and inferior frontal gyri. Conversely, relative to multiplication, comparison yielded superior activity in the right superior temporal gyrus, the left and right middle temporal gyri, the right superior frontal gyrus, and the right inferior frontal gyrus. These results underline the role of bilateral inferior parietal regions in number processing and suggest that multiplication and comparison may rest on partially distinct networks

Human subcortical brain asymmetries in 15,847 people worldwide reveal effects of age and sex

The two hemispheres of the human brain differ functionally and structurally. Despite over a century of research, the extent to which brain asymmetry is influenced by sex, handedness, age, and genetic factors is still controversial. Here we present the largest ever analysis of subcortical brain asymmetries, in a harmonized multi-site study using meta-analysis methods. Volumetric asymmetry of seven subcortical structures was assessed in 15,847 MRI scans from 52 datasets worldwide. There were sex differences in the asymmetry of the globus pallidus and putamen. Heritability estimates, derived from 1170 subjects belonging to 71 extended pedigrees, revealed that additive genetic factors influenced the asymmetry of these two structures and that of the hippocampus and thalamus. Handedness had no detectable effect on subcortical asymmetries, even in this unprecedented sample size, but the asymmetry of the putamen varied with age. Genetic drivers of asymmetry in the hippocampus, thalamus and basal ganglia may affect variability in human cognition, including susceptibility to psychiatric disorders

Variations of planum temporale asymmetries with Heschl’s Gyri duplications and association with cognitive abilities: MRI investigation of 428 healthy volunteers

International audienceIn a large sample of 428 healthy adults balanced for gender and manual preference (MP), we investigated planum temporale (PT) surface area variability in relation with Heschl’s gyrus (HG) duplication pattern, MP, and familial sinistrality (FS), considering different PT definitions. In a sub-sample of 362 participants, we also investigated whether variability of PT asymmetry was associated with differences in verbal abilities. On each participant brain hemisphere MRI, we delineated a posterior PT area (PTpost), excluding the second Heschl gyrus in case of either complete posterior duplication (CPD) or common stem partial duplication (CSD). We then defined a total PT area (PTtot) as the union of PTpost and of the second HG when present, and a HGPT area as the union of PTtot and of the first HG. The HG duplication pattern of one hemisphere was found to significantly affect the PTpost surface area of the same hemisphere, a larger reduction being present in case of CPD than in case of CSD, leading to a strong impact of both left and right HG duplication patterns on PTpost asymmetry. The HG duplication pattern had no effect on PTtot surface areas, while a significant effect of the left HG duplication was present on PTtot asymmetry that was larger in case of a CSD as compared to a single HG. By contrast, the type of HG duplication did not affect HGPT and neither left nor right HG duplication pattern had an effect on HGPT asymmetry. Meanwhile, MP had no effect on PTpost, PTtot, HGPT, or their asymmetries. The absence of a left PTpost was associated with existence of FS (FS+) (7FS+ among nine without PTpost). Removing the nine individuals lacking PTpost, a lower left PTpost surface area was observed in FS+ participants with left CPD. In the sub-sample of 362 participants, we observed a significant interaction between PTpost asymmetry and cognitive abilities due to poorer lexical performances in individuals having a symmetric PTpost as compared to individuals having either a leftward or a rightward asymmetric PTpost. By contrast, there was no significant effect of PTtot or HGPT asymmetry on cognitive abilities. This study shows that HG duplication pattern mainly affects the surface area of the most posterior part of PT and its asymmetry, this PTpost area being specifically associated with variability in verbal performances. This study also shows, for the first time, an association between decreased performances and lack of PTpost anatomical asymmetry, being rightward asymmetrical having no deleterious effect on verbal abilities, thereby supporting the idea that anatomical lateralization is necessary for optimal verbal performances

Bases neurales de la langue des signes française

Ce texte est un rapport de fin de recherche issu de l'ACI cognitique.Ce projet a pour objet l'étude, chez des sujets signeurs sourds et entendants, des réseaux neuraux impliqués dans le traitement de la Langue des Signes Française (LSF). Les travaux récents sur les bases neurales des langues signées se sont focalisés sur la comparaison de ces langues avec les langues orales lors de tâches de dénomination et de génération et aucune étude n'a porté à ce jour sur la LSF. Bien qu'elles aient mis en évidence le partage d'un large réseau d'aires du langage, aucune d'entre elles n'a pris en compte un aspect linguistique inhérent à la langue des signes à savoir l'iconicité. Pourtant l'iconicité est un élément essentiel des langues signées qui a des répercussions sur le développement cognitif. Par exemple Cyril Courtin a montré que l'iconicité facilite les capacités de catégorisation des enfants sourds signeurs. Nous avons donc choisi d'entamer ce projet d'étude des bases neurales de la LSF par l'étude des corrélats neuraux de cette spécificité linguistique. Nous avons dans un premier temps évalué l'existence d'un effet de l'iconicité sur la dénomination chez l'adulte, en comparant des sujets traitant la langue orale et la langue des signes (Mémoire de DEA de Psychologie de Mélanie Dubois, Université Caen-Rouen). Les résultats montrent un effet significatif de l'iconicité de forme qui induit une facilitation de dénomination uniquement en langue des signes française. Aucun effet n'a été observé pour les items à iconicité fonctionnelle. À partir de ces résultats nous avons mis au point un paradigme de dénomination en Imagerie par Résonance magnétique fonctionnelle (IRMf ), les acquisitions en IRMf chez les sujets entendants signeurs natifs et monolingues débutant en décembre