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

Underlying Skills of Oral and Silent Reading Fluency in Chinese: Perspective of Visual Rapid Processing

Reading fluency is a critical skill to improve the quality of our daily life and working efficiency. The majority of previous studies focused on oral reading fluency rather than silent reading fluency, which is a much more dominant reading mode that is used in middle and high school and for leisure reading. It is still unclear whether the oral and silent reading fluency involved the same underlying skills. To address this issue, the present study examined the relationship between the visual rapid processing and Chinese reading fluency in different modes. Fifty-eight undergraduate students took part in the experiment. The phantom contour paradigm and the visual 1-back task were adopted to measure the visual rapid temporal and simultaneous processing respectively. These two tasks reflected the temporal and spatial dimensions of visual rapid processing separately. We recorded the temporal threshold in the phantom contour task, as well as reaction time and accuracy in the visual 1-back task. Reading fluency was measured in both single-character and sentence levels. Fluent reading of single characters was assessed with a paper-and-pencil lexical decision task, and a sentence verification task was developed to examine reading fluency on a sentence level. The reading fluency test in each level was conducted twice (i.e., oral reading and silent reading). Reading speed and accuracy were recorded. The correlation analysis showed that the temporal threshold in the phantom contour task did not correlate with the scores of the reading fluency tests. Although, the reaction time in visual 1-back task correlated with the reading speed of both oral and silent reading fluency, the comparison of the correlation coefficients revealed a closer relationship between the visual rapid simultaneous processing and silent reading. Furthermore, the visual rapid simultaneous processing exhibited a significant contribution to reading fluency in silent mode but not in oral reading mode. These findings suggest that the underlying mechanism between oral and silent reading fluency is different at the beginning of the basic visual coding. The current results also might reveal a potential modulation of the language characteristics of Chinese on the relationship between visual rapid processing and reading fluency

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

Adults with dyslexia can use cues to orient and constrain attention but have a smaller and weaker attention spotlight

We report results from two experiments assessing distribution of attention and cue use in adults with dyslexia (AwD) and in a group of typically reading controls. Experiment 1 showed normal effects of cueing in AwD, with faster responses when probes were presented within a cued area and normal effects of eccentricity and stimulus onset asynchrony (SOA). In addition, AwD showed stronger benefits of a longer SOA when they had to move attention farther, and stronger effects of inclusion on the left, suggesting that cueing is particularly important in more difficult conditions. Experiment 2 tested the use of cues in a texture detection task involving a wider range of eccentricities and a shorter SOA. In this paradigm, focused attention at the central location is actually detrimental and cueing further reduces performance. Thus, if AwD have a more distributed attention, they should show a reduced performance drop at central locations and, if they do not use cues, they should show less negative effects of cueing. In contrast, AwD showed a larger drop and a positive effect of cueing. These results are better accounted for by a smaller and weaker spotlight of attention. Performance does not decrease at central locations because the attentional spotlight is already deployed with maximum intensity, which cannot be further enhanced at central locations. Instead, use of cueing helps to focus limited resources. Cues orient attention to the right area without enhancing it to the point where this is detrimental for texture detection. Implications for reading are discussed

Functional integration across oscillation frequencies by cross-frequency phase synchronization

Neuronal oscillations and their inter-areal synchronization may be instrumental in regulating neuronal communication in distributed networks. Several lines of research have, however, shown that cognitive tasks engage neuronal oscillations simultaneously in multiple frequency bands that have distinct functional roles in cognitive processing. Gamma oscillations (30-120Hz) are associated with bottom-up processing, while slower oscillations in delta (1-4Hz), theta (4-7Hz), alpha (8-14Hz) and beta (14-30Hz) frequency bands may have roles in executive or top-down controlling functions, although also other distinctions have been made. Identification of the mechanisms that integrate such spectrally distributed processing and govern neuronal communication among these networks is crucial for understanding how cognitive functions are achieved in neuronal circuits. Cross-frequency interactions among oscillations have been recognized as a likely candidate mechanism for such integration. We advance here the hypothesis that phase-phase synchronization of neuronal oscillations in two different frequency bands, cross-frequency phase synchrony (CFS), could serve to integrate, coordinate and regulate neuronal processing distributed into neuronal assemblies concurrently in multiple frequency bands. A trail of studies over the past decade has revealed the presence of CFS among cortical oscillations and linked CFS with roles in cognitive integration. We propose that CFS could connect fast and slow oscillatory networks and thereby integrate distributed cognitive functions such as representation of sensory information with attentional and executive functions.Peer reviewe

Print-Tuning Lateralization and Handedness:An Event-Related Potential Study in Dyslexic Higher Education Students

Despite their ample reading experience, higher education students with dyslexia still show deficits in reading and reading-related skills. Lateralized print tuning, the early sensitivity to print of the left parietal cortex signalled by the N1 event-related potential (ERP) component, differs between beginning dyslexic readers and controls. For adults, the findings are mixed. The present study aims to investigate whether print tuning, as indexed by the N1 component, differs between 24 students with dyslexia and 15 non-dyslexic controls. Because handedness has been linked to lateralization, first, a separate analysis was conducted including only right-handed participants (n=12 in both groups), like in most previous studies. ERPs were measured during a judgement task, requiring visual, phonological, or semantic judgments. In both groups, the N1 was earlier and stronger in the left than in the right hemisphere. However, when only strongly right-handed participants were evaluated, the N1 was less left-lateralized for participants with dyslexia as compared with controls. Participants with dyslexia had longer reaction times during the ERP experiment and performed worse on many reading (-related) tasks. These findings suggest that abnormal print tuning can still be found among higher education students with dyslexia and that handedness should be regarded in the study of print tuning. Copyright (c) 2015 John Wiley & Sons, Ltd