Seeing is knowing? Visual word recognition in non-dyslexic and dyslexic readers: an ERP study

The aim of the current study was to investigate whether phonological/semantic processing of the word takes place simultaneously with, or following, the early processing of its visual features. Event related potentials (ERPs) were recorded in 13 dyslexic (four female) and 14 non-dyslexic (six female) native English speaking young adults in two lexical decision tasks. In Task 1 participants had to make an orthographic lexical decision to distinguish frequently used words (W) from pseudohomophones (PH1)focusing on visual properties of stimuli. In Task 2 they had to make a phonological lexical decision—to pseudohomophones (PH2) and pseudowords (PW) and decide whether stimuli sounded like real words—focusing on non-visual higher order, i.e., phonological and semantic, processing of the stimuli. The behavioural performance was less good and the ERP peaks’ latency longer in dyslexics compared to controls. The reaction times (RTs) and the number of errors (reversed for the controls in Task 2) increased across four conditions for both groups in the following order: W< PH1< PH2< PW. The ERPs were larger in Task 2 compared to Task 1 starting at 100 ms (P1) for the controls and from about 220 ms (P2) for the dyslexics. The latency of N2 peak in left occipito-temporal sites was larger (as was the number of errors) in PH2 compared to PW condition in controls only, which indicates phonological/semantic specific processing at a time latency of 250–260 ms. Thus, the visual task required less effort than the phonological task, dyslexics’ behavioural performance was less good and the brain activation delayed compared to controls. Combined behavioural and ERP results of this study indicated that phonological/semantic processing of the word took place 150 ms after processing of its visual features in controls and possibly later in dyslexics

On the Schoenberg Transformations in Data Analysis: Theory and Illustrations

The class of Schoenberg transformations, embedding Euclidean distances into higher dimensional Euclidean spaces, is presented, and derived from theorems on positive definite and conditionally negative definite matrices. Original results on the arc lengths, angles and curvature of the transformations are proposed, and visualized on artificial data sets by classical multidimensional scaling. A simple distance-based discriminant algorithm illustrates the theory, intimately connected to the Gaussian kernels of Machine Learning

Children with Reading Disability Show Brain Differences in Effective Connectivity for Visual, but Not Auditory Word Comprehension

Background: Previous literature suggests that those with reading disability (RD) have more pronounced deficits during semantic processing in reading as compared to listening comprehension. This discrepancy has been supported by recent neuroimaging studies showing abnormal activity in RD during semantic processing in the visual but not in the auditory modality. Whether effective connectivity between brain regions in RD could also show this pattern of discrepancy has not been investigated. Methodology/Principal Findings: Children (8- to 14-year-olds) were given a semantic task in the visual and auditory modality that required an association judgment as to whether two sequentially presented words were associated. Effective connectivity was investigated using Dynamic Causal Modeling (DCM) on functional magnetic resonance imaging (fMRI) data. Bayesian Model Selection (BMS) was used separately for each modality to find a winning family of DCM models separately for typically developing (TD) and RD children. BMS yielded the same winning family with modulatory effects on bottom-up connections from the input regions to middle temporal gyrus (MTG) and inferior frontal gyrus(IFG) with inconclusive evidence regarding top-down modulations. Bayesian Model Averaging (BMA) was thus conducted across models in this winning family and compared across groups. The bottom-up effect from the fusiform gyrus (FG) to MTG rather than the top-down effect from IFG to MTG was stronger in TD compared to RD for the visual modality. The stronge

Executive functions in adults with developmental dyslexia

Background: Executive functioning (EF) deficits are well recognized in developmental dyslexia, yet the majority of studies have concerned children rather than adults, ignored the subjective experience of the individual with dyslexia (with regard to their own EFs), and have not followed current theoretical perspectives on EFs. Aims and Methods: The current study addressed these shortfalls by administering a self-report measure of EF (BRIEF-A; Roth, Isquith & Gioia, 2005) and experimental tasks to IQ-matched groups of adults with and without dyslexia. The laboratory-based tasks tested the three factors constituting the framework of EF proposed by Miyake et al. (2000). Results: In comparison to the group without dyslexia, the participants with dyslexia self-reported more frequent EF problems in day-to-day life, with these difficulties centering on metacognitive processes (working memory, planning, task monitoring, and organization) rather than on the regulation of emotion and behaviour. The participants with dyslexia showed significant deficits in EF (inhibition, set shifting, and working memory). Conclusions and Implications: The findings indicated that dyslexia-related problems have an impact on the daily experience of adults with the condition. Further, EF difficulties are present in adulthood across a range of laboratory-based measures, and, given the nature of the experimental tasks presented, extend beyond difficulties related solely to phonological processing