Comparative electrophysiological study of word reading in French: does the P1-N1 temporal window reveal a neurodevelopmental anomaly?

International audienceBackground: Event-Related Potentials (ERPs) permit to study neuronal specialization during reading acquisition. The N170 wave was previously shown to be a surrogate of the fine tuning of reading in adults and adolescents as well. Aim: We analyzed and described the variations of the N170 wave as a function of French words with visual or phonetical similarities in 12 to 14 yearold dyslexic patients. We tested the validity and modulation of this effect by comparing different populations of normal and dyslexic patients of various severity. Methods: ERPs were recorded in seventeen dyslexic children with the same method as in normative populations in lexical decision. Stimuli consisted of frequent words chosen on the basis of near or far visemes and morphemes. Dyslexic children were compared to two control (i.e. normal readers) groups, one group of the same age (N=15) and one group of adults (N=17). N170 and P100 waves were analyzed, as well as interactions between both (i.e. P1N1) searched. Psychometric and language tests were also performed. Results were analyzed by ANOVA. Results: The results of sixteen patients are presented. All sixteen showed significant differences on all psycholinguistic items when compared to the two control groups. All groups (patients and controls) significantly differed from each other for all tests (F'(4;42)=119, 2; p<0.001). However, the heterogeneity of the ERP patterns in the dyslexic group rendered group averaging irrelevant. The N170 wave sometimes overlapped with the P100 wavelength, but was also found to be negative or absent in some patients. In the course of development, N170 variations seem dependent on characteristics of the P100. No correlation was found between the variations of the N170 and clinical measures. Analysis of the P1-N1 temporal course showed a tendency to correlate with reading speed for the entire study population, yet not reaching statistical significance. Interpretation: N170 variations during development and dyslexic pathologies are associated with P100 variations. The P1-N1 time course could reflect silent reading speed. The P1-N1 temporal course was linked with clinical measures in all three groups, which could reflect neurodevelopmentalyrelated variations of the heterogeneity of the N170 as well as a developmental pathology. Verbal stimuli permit us to test the N170 physiological heterogeneity during development but variations in response to easy tasks show low sensitivity of N170 as a marker of dyslexia

Former contre les discriminations (ethno)culturelles

En France comme ailleurs, l’École est rappelée à sa mission d’éducation au vivre ensemble et à la démocratie. Dans ce contexte, la lutte contre la discrimination – ici ethnoculturelle – s’est peu à peu constituée comme objet de formation. Pourtant, si une palette d’outils et de nouveaux contenus voient le jour, ceux-ci restent éparpillés et peu lisibles. Inégalement appropriée par les acteurs, cette dimension de la formation est aussi trop peu arrimée à la recherche. Ce dossier entend contribuer à structurer la réflexion dans ce domaine à partir d’une double entrée. D’une part, il tire parti de la recherche sur les phénomènes de discrimination et sur les processus associés (ségrégation, biais d’évaluation ou d’orientation, etc.) afin d’identifier des objets et des leviers de formation. D’autre part, il analyse de manière réflexive des dispositifs de formation dédiés afin d’en dégager les écueils et les potentialités. Les recherches présentées recouvrent quatre contextes : suisse francophone, belge francophone, québécois, français. La comparaison révèle la forte indexicalité de ces questions, tant dans la manière de désigner les groupes discriminés et de construire les problèmes que dans la place occupée par cet objet à l’agenda des politiques éducatives et de formation. In fine, le dossier invite à prendre à bras le corps le débat sur les discriminations ethnoculturelles et à en faire un objet de réflexivité collective, en tenant spécifiquement compte des contextes locaux. In France as elsewhere, schools are reminded of their mission to educate people for coexistence and democracy. In this context, the fight against ethnocultural discrimination has gradually become an object of teacher training. However, while new training content and a range of tools are emerging, they remain scattered and opaque. Unevenly adopted by stakeholders, this dimension of teacher training is also insufficiently linked to research. This issue aims to contribute to structuring the reflection in this area from two complementary perspectives. On the one hand, it takes advantage of research on discrimination and its accompanying school processes (segregation, evaluation or orientation bias, etc.) to identify training objects and levers. On the other hand, it reflexively scrutinises dedicated training methods in order to identify their pitfalls and potentialities. The research presented covers four contexts: French-speaking Switzerland, French-speaking Belgium, Quebec, and France. The comparison reveals the strong indexicality of these questions, both in the way in which discriminated groups are identified and problems are constructed, and in the place this subject occupies on the agenda of education and training policies. To sum up, the dossier invites to tackle the debate on ethnocultural discrimination head-on and make it an object of collective reflexivity, taking specific account of local contexts

Female-to-Male Breeding Ratio in Modern Humans—an Analysis Based on Historical Recombinations

Was the past genetic contribution of women and men to the current human population equal? Was polygyny (excess of breeding women) present among hominid lineages? We addressed these questions by measuring the ratio of population recombination rates between the X chromosome and the autosomes, ρX/ρA. The X chromosome recombines only in female meiosis, whereas autosomes undergo crossovers in both sexes; thus, ρX/ρA reflects the female-to-male breeding ratio, β. We estimated β from ρX/ρA inferred from genomic diversity data and calibrated with recombination rates derived from pedigree data. For the HapMap populations, we obtained β of 1.4 in the Yoruba from West Africa, 1.3 in Europeans, and 1.1 in East Asian samples. These values are consistent with a high prevalence of monogamy and limited polygyny in human populations. More mutations occur during male meiosis as compared to female meiosis at the rate ratio referred to as α. We show that at α ≠ 1, the divergence rates and genetic diversities of the X chromosome relative to the autosomes are complex functions of both α and β, making their independent estimation difficult. Because our estimator of β does not require any knowledge of the mutation rates, our approach should allow us to dissociate the effects of α and β on the genetic diversity and divergence rate ratios of the sex chromosomes to the autosomes