Bayesian modeling of human performance in a visual processing training software

International audienceDyslexia is a deficit of the identification of words, which is thought to be a consequence of different possible cognitive impairments. Recent data suggest that one of these might be a specific deficit of the visual attention span (VAS). We are developing a remediation software for dyslexic children that focuses on the VAS and its training. A central component of this software is the estimation of the performance of a given participant for all possible exercises. We describe a preliminary probabilistic model of participant performance, based on Bayesian modeling and inference. We mathematically define the model, making explicit underlying generalization hypotheses. The model yields a computation of the most probable predicted performance space, and, as a direct extension, an exercise selection strategy

Neuronal correlates of full and partial visual conscious perception

Stimuli may induce only partial consciousness—an intermediate between null and full consciousness—where the presence but not identity of an object can be reported. The differences in the neuronal basis of full and partial consciousness are poorly understood. We investigated if evoked and oscillatory activity could dissociate full from partial conscious perception. We recorded human cortical activity with magnetoencephalography (MEG) during a visual perception task in which stimulus could be either partially or fully perceived. Partial consciousness was associated with an early increase in evoked activity and theta/low-alpha-band oscillations while full consciousness was also associated with late evoked activity and beta-band oscillations. Full from partial consciousness was dissociated by stronger evoked activity and late increase in theta oscillations that were localized to higher-order visual regions and posterior parietal and prefrontal cortices. Our results reveal both evoked activity and theta oscillations dissociate partial and full consciousness.Peer reviewe

Hyperedge bundling : A practical solution to spurious interactions in MEG/EEG source connectivity analyses

Inter-areal functional connectivity (FC), neuronal synchronization in particular, is thought to constitute a key systems-level mechanism for coordination of neuronal processing and communication between brain regions. Evidence to support this hypothesis has been gained largely using invasive electrophysiological approaches. In humans, neuronal activity can be non-invasively recorded only with magneto-and electroencephalography (MEG/EEG), which have been used to assess FC networks with high temporal resolution and whole-scalp coverage. However, even in source-reconstructed MEG/EEG data, signal mixing, or "source leakage", is a significant confounder for FC analyses and network localization. Signal mixing leads to two distinct kinds of false-positive observations: artificial interactions (AI) caused directly by mixing and spurious interactions (SI) arising indirectly from the spread of signals from true interacting sources to nearby false loci. To date, several interaction metrics have been developed to solve the AI problem, but the SI problem has remained largely intractable in MEG/EEG all-to-all source connectivity studies. Here, we advance a novel approach for correcting SIs in FC analyses using source-reconstructed MEG/EEG data. Our approach is to bundle observed FC connections into hyperedges by their adjacency in signal mixing. Using realistic simulations, we show here that bundling yields hyperedges with good separability of true positives and little loss in the true positive rate. Hyperedge bundling thus significantly decreases graph noise by minimizing the false-positive to true-positive ratio. Finally, we demonstrate the advantage of edge bundling in the visualization of large-scale cortical networks with real MEG data. We propose that hypergraphs yielded by bundling represent well the set of true cortical interactions that are detectable and dissociable in MEG/EEG connectivity analysis.Peer reviewe

Visual processing of multiple elements in the dyslexic brain : evidence for a superior parietal dysfunction

Peer reviewe

Increased MHC matching by C4 gene compatibility in URD HSCT

HLA matching is a prerequisite for successful allogeneic hematopoietic stem cell transplantation (HSCT) because it lowers the occurrence and severity of graft-versus-host disease (GVHD). However, matching a few alleles of the classic HLA genes only may not ensure matching of the entire MHC region. HLA haplotype matching has been reported to be beneficial in HSCT because of the variation relevant to GVHD risk in the non-HLA region. Because polymorphism in the MHC is highly population specific, we hypothesized that donors from the Finnish registry are more likely to be matched at a higher level for the Finnish patients than donors from other registries. In the present study we determined 25 single nucleotide polymorphisms (SNPs) of the complement component 4 (C4) gene in the γ-block segment of MHC from 115 Finnish HSCT patients and their Finnish (n = 201) and non-Finnish (n = 280) donor candidates. Full matching of HLA alleles and C4 SNPs, independently or additively, occurred more likely in the Finnish–Finnish group as compared with the Finnish–non-Finnish group (P C4 matched donor, regardless of donor origin, as compared with patients without AH (P C4 matching and clinical outcome. The results suggest that screening C4 SNPs can be advantageous when an extended MHC matching or HLA haplotype matching in HSCT is required. This study also supports the need for small population-specific stem cell registries.</p

Paying visual attention to pre-orthographic processing in reading and developmental dyslexia.

Ce travail de thèse a pour objectif d'explorer le rôle de l'attention visuelle dans les traitements visuels précoces en lecture. Il repose sur le cadre théorique du modèle mémoire multitrace de lecture (MTM) et de l'hypothèse du trouble de l'empan visuo-attentionel (VA) dans la dyslexie développementale. La capacité d'attention visuelle est opérationnalisée par l'empan VA, défini comme le nombre maximal d'éléments visuels qui peuvent être traités en parallèle. L'empan VA contribue significativement aux performances en lecture et est réduit chez une partie de la population dyslexique. Une série de trois études a exploré les relations entre l'attention visuelle, l'empan VA et la lecture chez le normo-lecteur. Dans une première étude, nous avons testé si le traitement des lettres dans les tâches de report de l'empan VA était parallèle ou sériel. Dans une deuxième étude, nous avons cherché à spécifier le rôle de l'attention visuelle dans l'empan VA et la lecture. Enfin, dans une troisième étude, nous voulions mettre en évidence à l'aide de l'IRMf l'implication des réseaux neuronaux de l'attention visuelle dans les traitements pré-orthographiques. Ces trois études suggèrent que l'attention visuelle est une composante importante des traitements pré-orthographiques de séquences de lettres. L'objectif de la deuxième série d'études était de montrer qu'un déficit de l'attention visuelle est l'explication la plus plausible du déficit de l'empan VA. Dans une quatrième étude, nous avons confronté les prédictions d'une explication phonologique ou visuelle du déficit de l'empan VA pour une tâche de catégorisation de séquences de caractères. Enfin, une dernière étude a évalué les corrélats neuronaux associés au traitement visuel de séquences de caractères chez des adultes dyslexiques avec trouble de l'empan VA. Ces deux dernières études suggèrent que le trouble sous-jacent au déficit de l'empan VA est bien une réduction de la capacité d'attention visuelle et non pas un déficit des capacités de recodage verbal.This doctoral thesis aims to investigate the role of visual attention in the visual front-end of reading. It is grounded in the theoretical framework of the multi trace memory model (MTM) of reading and of the visual attention (VA) span deficit hypothesis of developmental dyslexia. Visual attention capacity in the MTM model is operationalized by the VA span, defined as the maximum number of individual visual elements that can be processed in parallel. VA span contributes significantly to reading performance in normal reading children and is selectively impaired in a subset of the dyslexic population. Three studies investigated the role of visual attention in VA span and visual word recognition in normal reading. A first study tested whether letter processing in the VA span whole report task was parallel or serial. A second study specified the role of visual attention in VA span and reading speed. Finally, a third study used fMRI to investigate whether pre-orthographic processing involves neural networks of visual attention. These three studies argue for visual attention as an important component of pre-orthographic processing. A second series of studies aimed to show that an impairment of visual attention best accounts for the VA span deficit. In a fourth study, predictions of phonological and visual accounts of the VA span deficit were tested using a multiple character categorization task. Finally, a fifth study explored the neural correlates of multiple character processing in VA span impaired adults. These last two studies argue for reduced visual attention capacity and not poor verbal recoding abilities as the underlying cause for the VA span deficit

Visual attention deficits in developmental dyslexia cannot be ascribed solely to poor reading experience

International audienc

Attention visuelle et traitements pré-orthographiques dans la lecture et la dyslexie

Ce travail de thèse a pour objectif d'explorer le rôle de l'attention visuelle dans les traitements visuels précoces en lecture. Il repose sur le cadre théorique du modèle mémoire multitrace de lecture (MTM) et de l'hypothèse du trouble de l'empan visuo-attentionel (VA) dans la dyslexie développementale. La capacité d'attention visuelle est opérationnalisée par l'empan VA, défini comme le nombre maximal d'éléments visuels qui peuvent être traités en parallèle. L'empan VA contribue significativement aux performances en lecture et est réduit chez une partie de la population dyslexique. Une série de trois études a exploré les relations entre l'attention visuelle, l'empan VA et la lecture chez le normo-lecteur. Dans une première étude, nous avons testé si le traitement des lettres dans les tâches de report de l'empan VA était parallèle ou sériel. Dans une deuxième étude, nous avons cherché à spécifier le rôle de l'attention visuelle dans l'empan VA et la lecture. Enfin, dans une troisième étude, nous voulions mettre en évidence à l'aide de l'IRMf l'implication des réseaux neuronaux de l'attention visuelle dans les traitements pré-orthographiques. Ces trois études suggèrent que l'attention visuelle est une composante importante des traitements pré-orthographiques de séquences de lettres. L'objectif de la deuxième série d'études était de montrer qu'un déficit de l'attention visuelle est l'explication la plus plausible du déficit de l'empan VA. Dans une quatrième étude, nous avons confronté les prédictions d'une explication phonologique ou visuelle du déficit de l'empan VA pour une tâche de catégorisation de séquences de caractères. Enfin, une dernière étude a évalué les corrélats neuronaux associés au traitement visuel de séquences de caractères chez des adultes dyslexiques avec trouble de l'empan VA. Ces deux dernières études suggèrent que le trouble sous-jacent au déficit de l'empan VA est bien une réduction de la capacité d'attention visuelle et non pas un déficit des capacités de recodage verbal.This doctoral thesis aims to investigate the role of visual attention in the visual front-end of reading. It is grounded in the theoretical framework of the multi trace memory model (MTM) of reading and of the visual attention (VA) span deficit hypothesis of developmental dyslexia. Visual attention capacity in the MTM model is operationalized by the VA span, defined as the maximum number of individual visual elements that can be processed in parallel. VA span contributes significantly to reading performance in normal reading children and is selectively impaired in a subset of the dyslexic population. Three studies investigated the role of visual attention in VA span and visual word recognition in normal reading. A first study tested whether letter processing in the VA span whole report task was parallel or serial. A second study specified the role of visual attention in VA span and reading speed. Finally, a third study used fMRI to investigate whether pre-orthographic processing involves neural networks of visual attention. These three studies argue for visual attention as an important component of pre-orthographic processing. A second series of studies aimed to show that an impairment of visual attention best accounts for the VA span deficit. In a fourth study, predictions of phonological and visual accounts of the VA span deficit were tested using a multiple character categorization task. Finally, a fifth study explored the neural correlates of multiple character processing in VA span impaired adults. These last two studies argue for reduced visual attention capacity and not poor verbal recoding abilities as the underlying cause for the VA span deficit.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF