Atypical characteristic changes of surface morphology and structural covariance network in developmental dyslexia

BACKGROUND

Developmental dyslexia (DD) is a neurodevelopmental disorder that is characterized by difficulties with all aspects of information acquisition in the written word, including slow and inaccurate word recognition. The neural basis behind DD has not been fully elucidated.

METHOD

The study included 22 typically developing (TD) children, 16 children with isolated spelling disorder (SpD), and 20 children with DD. The cortical thickness, folding index, and mean curvature of Broca's area, including the triangular part of the left inferior frontal gyrus (IFGtriang) and the opercular part of the left inferior frontal gyrus, were assessed to explore the differences of surface morphology among the TD, SpD, and DD groups. Furthermore, the structural covariance network (SCN) of the triangular part of the left inferior frontal gyrus was analyzed to explore the changes of structural connectivity in the SpD and DD groups.

RESULTS

The DD group showed higher curvature and cortical folding of the left IFGtriang than the TD group and SpD group. In addition, compared with the TD group and the SpD group, the structural connectivity between the left IFGtriang and the left middle-frontal gyrus and the right mid-orbital frontal gyrus was increased in the DD group, and the structural connectivity between the left IFGtriang and the right precuneus and anterior cingulate was decreased in the DD group.

CONCLUSION

DD had atypical structural connectivity in brain regions related to visual attention, memory and which might impact the information input and integration needed for reading and spelling.

Atypical beta-band effects in children with dyslexia in response to rhythmic audio-visual speech

OBJECTIVE

Previous studies have reported atypical delta phase in children with dyslexia, and that delta phase modulates the amplitude of the beta-band response via delta-beta phase-amplitude coupling (PAC). Accordingly, the atypical delta-band effects in children with dyslexia may imply related atypical beta-band effects, particularly regarding delta-beta PAC. Our primary objective was to explore beta-band oscillations in children with and without dyslexia, to explore potentially atypical effects in the beta band in dyslexic children.

METHODS

We collected EEG data during a rhythmic speech paradigm from 51 children (21 control; 30 dyslexia). We then assessed beta-band phase entrainment, beta-band angular velocity, beta-band power responses and delta-beta PAC.

RESULTS

We found significant beta-band phase entrainment for control children but not for dyslexic children. Furthermore, children with dyslexia exhibited significantly faster beta-band angular velocity and significantly greater beta-band power. Delta-beta PAC was comparable in both groups.

CONCLUSION

Atypical beta-band effects were observed in children with dyslexia. However, delta-beta PAC was comparable in both dyslexic and control children.

SIGNIFICANCE

These findings offer further insights into the neurophysiological basis of atypical rhythmic speech processing by children with dyslexia, suggesting the involvement of a wide range of frequency bands.

Unraveling individual differences in learning potential: A dynamic framework for the case of reading development

Children show an enormous capacity to learn during development, but with large individual differences in the time course and trajectory of learning and the achieved skill level. Recent progress in developmental sciences has shown the contribution of a multitude of factors including genetic variation, brain plasticity, socio-cultural context and learning experiences to individual development. These factors interact in a complex manner, producing children's idiosyncratic and heterogeneous learning paths. Despite an increasing recognition of these intricate dynamics, current research on the development of culturally acquired skills such as reading still has a typical focus on snapshots of children's performance at discrete points in time. Here we argue that this 'static' approach is often insufficient and limits advancements in the prediction and mechanistic understanding of individual differences in learning capacity. We present a dynamic framework which highlights the importance of capturing short-term trajectories during learning across multiple stages and processes as a proxy for long-term development on the example of reading. This framework will help explain relevant variability in children's learning paths and outcomes and fosters new perspectives and approaches to study how children develop and learn.

The reading-attention relationship: Variations in working memory network activity during single word decoding in children with and without dyslexia

This study utilized a neuroimaging task to assess working memory (WM) network recruitment during single word reading. Associations between WM and reading comprehension skills are well documented. Several converging models suggest WM may also contribute to foundational reading skills, but few studies have assessed this contribution directly. Two groups of children (77 developmental dyslexia (DD), 22 controls) completed a functional magnetic resonance imaging (fMRI) task to identify activation of a priori defined regions of the WM network. fMRI trials consisted of familiar word, pseudoword, and false font stimuli within a 1-back oddball task to assess how activation in the WM network differs in response to stimuli that can respectively be processed using word recognition, phonological decoding, or non-word strategies. Results showed children with DD recruited WM regions bilaterally in response to all stimulus types, whereas control children recruited left-lateralized WM regions during the pseudoword condition only. Group-level comparisons revealed activation differences in the defined WM network regions for false font and familiar word, but not pseudoword conditions. This effect was driven by increased activity in participants with DD in right hemisphere frontal, parietal, and motor regions despite poorer task performance. Findings suggest the WM network may contribute to inefficient decoding and word recognition strategies in children with DD.

The odd one out - Orthographic oddball processing in children with poor versus typical reading skills in a fast periodic visual stimulation EEG paradigm

The specialization of left ventral occipitotemporal brain regions to automatically process word forms develops with reading acquisition and is diminished in children with poor reading skills (PR). Using a fast periodic visual oddball stimulation (FPVS) design during electroencephalography (EEG), we examined the level of sensitivity and familiarity to word form processing in ninety-two children in 2nd and 3rd grade with varying reading skills (n = 35 for PR, n = 40 for typical reading skills; TR). To test children's level of "sensitivity", false font (FF) and consonant string (CS) oddballs were embedded in base presentations of word (W) stimuli. "Familiarity" was examined by presenting letter string oddballs with increasing familiarity (CS, pseudoword - PW, W) in FF base stimuli. Overall, our results revealed stronger left-hemispheric coarse sensitivity effects ("FF in W" > "CS in W") in TR than in PR in both topographic and oddball frequency analyses. Further, children distinguished between orthographically legal and illegal ("W/PW in FF" > "CS in FF") but not yet between lexical and non-lexical ("W in FF" vs "PW in FF") word forms. Although both TR and PR exhibit visual sensitivity and can distinguish between orthographically legal and illegal letter strings, they still struggle with nuanced lexical distinctions. Moreover, the strength of sensitivity is linked to reading proficiency. Our work adds to established knowledge in the field to characterize the relationship between print tuning and reading skills and suggests differences in the developmental progress to automatically process word forms.

Atypical reliance on monocular visual pathway for face and word recognition in developmental dyslexia

Studies with individuals with developmental dyslexia (DD) have documented impaired perception of words and faces, both of which are domains of visual expertise for human adults. In this study, we examined a possible mechanism that might be associated with the impaired acquisition of visual expertise for words and faces in DD, namely, the atypical engagement of the monocular visual pathway. Participants with DD and typical readers (TR) judged whether a pair of sequentially presented unfamiliar faces or nonwords were the same or different, and the pair of stimuli were displayed in an eye-specific fashion using a stereoscope. Based on evidence of greater reliance on subcortical structures early in development, we predicted differences between the groups in the engagement of lower (monocular) versus higher (binocular) regions of the visual pathways. Whereas the TR group showed a monocular advantage for both stimulus types, the DD participants evinced a monocular advantage for faces and words that was much greater than that measured in the TRs. These findings indicate that the DD individuals have enhanced subcortical engagement and that this might arise from the failure to fine-tune cortical correlates mediating the discrimination of homogeneous exemplars in domains of expertise.

Phonological deficits in dyslexia impede lexical processing of spoken words: Linking behavioural and MEG data

Phonological difficulties have been identified as a core deficit in developmental dyslexia, yet everyday speech comprehension, which relies on phonological processing, is seemingly unaffected. This raises the question as to how dyslexic readers process spoken words to achieve normal word comprehension. Here we establish a link between neural correlates of lexical and sublexical processing in auditory words and behaviourally measured phonological deficits using magnetoencephalography (MEG). Spatiotemporally resolved cortical responses to phonological and lexico-semantic information were computed with the event-related regression technique (Hauk et al., 2009) and correlated with dyslexic and non-dyslexic subjects' phonological skills. We found that phonological deficits reduced cortical responses to both phonological and lexico-semantic information (phonological neighbours and word frequency). Individuals with lower phonological skills - independent of dyslexia diagnosis - showed weaker neural responses to phonological neighbourhood information in both hemispheres 200-500 ms after word onset and reduced sensitivity to written and spoken word frequency between 200 and 650 ms. Dyslexic readers showed weaker responses to written word frequency in particular compared to the control group, pointing towards an additional effect of print exposure on auditory word processing. Source space analysis localised phonological and lexico-semantic effect peaks to the left superior temporal gyrus, a key area that has been related to core deficits in dyslexia across a range of neuroimaging studies. The results provide comprehensive evidence that phonological deficits impact both sublexical and lexical stages of spoken word processing and that these deficits cannot be fully compensated through neural re-organization of lexical-distributional information at the single word level. Theoretical and practical implications for typical readers, dyslexic readers, and readers with developmental language disorder are discussed.

Auditory attention influences trajectories of symbol-speech sound learning in children with and without dyslexia

The acquisition of letter-speech sound correspondences is a fundamental process underlying reading development, one that could be influenced by several linguistic and domain-general cognitive factors. In the current study, we mimicked the first steps of this process by examining behavioral trajectories of audiovisual associative learning in 110 7- to 12-year-old children with and without dyslexia. Children were asked to learn the associations between eight novel symbols and native speech sounds in a brief training and subsequently read words and pseudowords written in the artificial orthography. We then investigated the influence of auditory attention as one of the putative domain-general factors influencing associative learning. To this aim, we assessed children with experimental measures of auditory sustained selective attention and interference control. Our results showed shallower learning trajectories in children with dyslexia, especially during the later phases of the training blocks. Despite this, children with dyslexia performed similarly to typical readers on the post-training reading tests using the artificial orthography. Better auditory sustained selective attention and interference control skills predicted greater response accuracy during training. Sustained selective attention was also associated with the ability to apply these novel correspondences in the reading tests. Although this result has the limitations of a correlational design, it denotes that poor attentional skills may constitute a risk during the early stages of reading acquisition, when children start to learn letter-speech sound associations. Importantly, our findings underscore the importance of examining dynamics of learning in reading acquisition as well as individual differences in more domain-general attentional factors.

Combined multi-session transcranial alternating current stimulation (tACS) and language skills training improves individual gamma band activity and literacy skills in developmental dyslexia

Developmental dyslexia is characterized by the pathologically diminished ability to acquire reading and spelling skills. Accurate processing of acoustic information at the phonemic scale is crucial for successful sound-to-letter-mapping which, in turn, is elemental in reading and spelling. Altered activation patterns in the auditory cortex are thought to provide the neurophysiological basis for the inaccurate phonemic perception. Recently, transcranial electrical stimulation has been shown to be an effective method to ameliorate cortical activation patterns in the auditory cortex. In a sample of children and adolescents with dyslexia, we investigated the effect of multi-session transcranial alternating current stimulation delivered concurrently with a phonological training and in combination with a behavioral literacy skills training. Over a 5-week period the participants received 10 training sessions while gamma-tACS was administered over bilateral auditory cortex. We found that gamma-tACS shifted the peak frequency of auditory gamma oscillations reflecting a more fine-grained processing of time-critical acoustic information. This amelioration was accompanied by increased phonemic processing skills. Moreover, individuals who received gamma-tACS showed significant improvements in their spelling skills four months after the intervention. Our results demonstrate that multi-session gamma-tACS enhances the effects of a behavioral intervention and induces long-term improvement on literacy skills in dyslexia.

Responding to parental concern about children's reading

Objectives

This study explored if parents are accurate in their reading concerns, with implications for paediatric practice.

Methods

Parents of school-aged children in 34 schools in Ontario, Canada responded to a questionnaire about their children's academic development (27% response), and their children participated in standardized, norm-referenced tests of word reading and an oral sentence recall task. Parental concern status was retrospectively cross-referenced with reading difficulty status (<25th percentile on the word reading tests) for grade 2 children with complete data (n = 294); diagnostic accuracy was evaluated. Demographic and reading-related characteristics of children whose parents' concern did not match their reading difficulty status were explored.

Results

Approximately 22% of parents endorsed concern, while 18.5% of children had word reading difficulty. Parental concern status accurately corresponded with reading difficulty status in 81% of cases (95% CI: 76% to 85%). Specificity was 85% (95% CI: 80% to 90%), while sensitivity was 59% (95% CI: 44% to 73%). Children of unconcerned parents rarely had word reading problems (NPV 91%; 95% CI: 88% to 94%), while children with concerned parents had word reading difficulty in 45% of cases (PPV; 95% CI: 36% to 54%). Apparent inaccuracy (i.e., mismatch between parental concern and reading difficulty status) was related to children's word reading, oral sentence recall skills, and English language learner (ELL) status, but not child age, sex, or parent education.

Conclusions

Many parents of grade 2 children endorse reading concerns. Parental concern is an overall accurate screener for word reading difficulty, although some children will be missed. Evidence-informed recommendations for responding to parental concern are provided.

Home reading environment, sociometric and demographic factors associated with dyslexia in primary school students in China: A case-control study

Background

Developmental dyslexia (DD) has been generally recognized as a multifactorial psychological disorder in recent decades. However, studies on reading and learning environment, social and demographic factors affecting Chinese developmental dyslexia (DD) are still scarce in China. This study aims to explore multidimensional home influencing factors associated with DD before and after birth.

Methods

A total of 60 dyslexic and 252 normal elementary school students graded 2-5 were recruited in Shantou, China. The Least Absolute Shrinkage and Selection Operator (LASSO) regression model was used for the social and demographic variables screening. Odds ratios (ORs) with 95 % confidence intervals (CIs) for associations between DD and related factors were estimated by multivariate logistic regression models.

Results

Through LASSO regression, we ultimately identified 13 key variables, including maternal education level and family monthly income, among others. The logistic regression analyses showed that the risk of DD was higher in children with lower maternal education levels. Divergent parenting styles may be a risk factor for developing DD as opposed to consistent parenting styles (OR = 4.93, 95%CI: 1.11-21.91). Children whose mothers suffered from malnutrition during pregnancy were more likely to develop DD (OR = 10.31, 95%CI: 1.84-37.86), as well as exposure to second-hand smoking at home every day (OR = 5.33, 95%CI: 1.52-18.66). Interestingly, children's active reading (OR = 0.26, 95%CI: 0.08-0.84; OR = 0.17, 95%CI: 0.04-0.76 for "sometimes" and "often" compared to none, respectively), children having extracurricular reading fairy tale books (OR = 0.37, 95%CI: 0.15-0.90), and children having extracurricular reading composition books (OR = 0.25, 95%CI: 0.09-0.69) were significant protective factors for DD.

Conclusions

Home reading environment, several educational, sociometric and demographic factors may influence the development of dyslexia. We should pay attention to these factors on the development of dyslexia, so as to provide the well social and familial environment to ensure the healthy development of children.

Do developmental dyslexia and congenital amusia share underlying impairments?

Developmental dyslexia and congenital amusia have common characteristics. Yet, their possible association in some individuals has been addressed only scarcely. Recently, two converging studies reported a sizable comorbidity rate between these two neurodevelopmental disorders (Couvignou et al., Cognitive Neuropsychology 2019; Couvignou & Kolinsky, Neuropsychologia 2021). However, the reason for their association remains unclear. Here, we investigate the hypothesis of shared underlying impairments between dyslexia and amusia. Fifteen dyslexic children with amusia (DYS+A), 15 dyslexic children without amusia (DYS-A), and two groups of 25 typically developing children matched on either chronological age (CA) or reading level (RL) were assessed with a behavioral battery aiming to investigate phonological and pitch processing capacities at auditory memory, perceptual awareness, and attentional levels. Overall, our results suggest that poor auditory serial-order memory increases susceptibility to comorbidity between dyslexia and amusia and may play a role in the development of the comorbid phenotype. In contrast, the impairments observed in the DYS+A children for auditory item memory, perceptual awareness, and attention might be a consequence of their reduced reading experience combined with weaker musical skills. Comparing DYS+A and DYS-A children suggests that the latter are more resourceful and/or have more effective compensatory strategies, or that their phenotype results from a different developmental trajectory. We will discuss the relevance of these findings for delving into the etiology of these two developmental disorders and address their implications for future research and practice.

Intervention targeting different visual attention span components in Chinese children with developmental dyslexia: a study based on Bundesen's theory of visual attention

Within the framework of the theory of visual attention (TVA), the visual attention span (VAS) deficit among individuals with developmental dyslexia has been ascribed to the problems entailed by bottom-up (BotU) and top-down (TopD) attentional processes. The former involves two VAS subcomponents: the visual short-term memory storage and perceptual processing speed; the latter consists of the spatial bias of attentional weight and the inhibitory control. Then, what about the influences of the BotU and TopD components on reading? Are there differences in the roles of the two types of attentional processes in reading? This study addresses these issues by using two types of training tasks separately, corresponding to the BotU and TopD attentional components. Three groups of Chinese children with dyslexia-15 children each in the BotU training, TopD training, and non-trained active control groups were recruited here. Participants completed reading measures and a CombiTVA task which was used to estimate VAS subcomponents, before and after the training procedure. Results showed that BotU training improved both the within-category and between-category VAS subcomponents and sentence reading performance; meanwhile, TopD training enhanced character reading fluency through improving spatial attention capacity. Moreover, benefits on attentional capacities and reading skills in the two training groups were generally maintained three months after the intervention. The present findings revealed diverse patterns in the influences of VAS on reading within the TVA framework, which contributes to enriching the understanding of VAS-reading relation.

Adaptive compensation of arcuate fasciculus lateralization in developmental dyslexia

Previous studies have reported anomalies in the arcuate fasciculus (AF) lateralization in developmental dyslexia (DD). Still, the relationship between AF lateralization and literacy skills in DD remains largely unknown. The purpose of our study is to investigate the relationship between lateralization of three segments of AF (AF anterior segment (AFAS), AF long segment (AFLS), and AF posterior segment (AFPS)) and literacy skills in DD. A total of 26 children with dyslexia and 31 age-matched control children were included in this study. High angular diffusion imaging, combined with spherical deconvolution tractography, was used to reconstruct the AF. Connectivity measures of hindrance-modulated orientational anisotropy (HMOA) were computed for each of the three segments of the AF. The lateralization index (LI) of each AF segment was calculated by (right HMOA - left HMOA)/(right HMOA + left HMOA). Results showed that the LIs of AFAS and AFLS were positively correlated with reading accuracy in children with dyslexia. Specifically, the LI of AFAS was positively correlated with nonword and meaningless text reading accuracy, while the LI of AFLS accounted for word reading accuracy. The results suggest adaptive compensation of arcuate fasciculus lateralization in developmental dyslexia and functional dissociation of the anterior segment and long segment in the compensation.

The ReadFree tool for the identification of poor readers: a validation study based on a machine learning approach in monolingual and minority-language children

In this study, we validated the "ReadFree tool", a computerised battery of 12 visual and auditory tasks developed to identify poor readers also in minority-language children (MLC). We tested the task-specific discriminant power on 142 Italian-monolingual participants (8-13 years old) divided into monolingual poor readers (N = 37) and good readers (N = 105) according to standardised Italian reading tests. The performances at the discriminant tasks of the "ReadFree tool" were entered into a classification and regression tree (CART) model to identify monolingual poor and good readers. The set of classification rules extracted from the CART model were applied to the MLC's performance and the ensuing classification was compared to the one based on standardised Italian reading tests. According to the CART model, auditory go-no/go (regular), RAN and Entrainment100bpm were the most discriminant tasks. When compared with the clinical classification, the CART model accuracy was 86% for the monolinguals and 76% for the MLC. Executive functions and timing skills turned out to have a relevant role in reading. Results of the CART model on MLC support the idea that ad hoc standardised tasks that go beyond reading are needed.

Reduced Implicit but not Explicit Knowledge of Cross-Situational Statistical Learning in Developmental Dyslexia

Although statistical learning (SL) has been studied extensively in developmental dyslexia (DD), less attention has been paid to other fundamental challenges in language acquisition, such as cross-situational word learning. Such investigation is important for determining whether and how SL processes are affected in DD at the word level. In this study, typically developed (TD) adults and young adults with DD were exposed to a set of trials that contained multiple spoken words and multiple pictures of individual objects, with no information about word-referent correspondences provided within a trial. Nonetheless, cross-trial statistical relations could be exploited to learn word-referent mappings. The degree of within-trial reference uncertainty and the novelty of to-be-learned objects (novel or familiar) were varied under different learning conditions. The results show that across all conditions, young adults with DD were significantly impaired in their ability to exploit cross-trial regularities in co-occurring visual-auditory streams to discover word-referent mappings. Observed impairments were most pronounced when within-trial reference uncertainty was the highest. Subjective measures of knowledge awareness revealed greater development of implicit but not explicit knowledge in the TD group than in the DD group. Together, these findings suggest that the SL deficit in DD affects fundamental language learning challenges at the word level and points to greater reliance on explicit processes due to impaired implicit associative learning among individuals with DD. Such a deficit is likely to influence spoken language acquisition, and in turn affect literacy skills, in people with DD.

Tracking reading skills and reading-related skills in dyslexia before (age 5) and after (ages 10-17) diagnosis

This study had three goals: to examine the stability of deficits in the phonological and lexical routes in dyslexia (group study), to determine the prevalence of dyslexia profiles (multiple-case study), and to identify the prediction of phonemic segmentation and discrimination skills before reading acquisition on future reading level. Among a group of 373 non-readers seen at age 5, 38 students were subsequently diagnosed as either consistent dyslexic readers (18 DYS) or consistent typical readers (20 TR). Their phonological and lexical reading skills were assessed at ages 10 and 17 and their phonemic segmentation and discrimination skills at age 5. In comparison with TR of the same chronological age (CA-TR), individuals with dyslexia demonstrated an impairment of the two reading routes, especially of the phonological reading route. In the comparison with younger TR (age 10) of the same reading level (RL-TR), only a deficit of the phonological route is observed. In the multiple-case study, the comparisons with CA-TR showed a prevalence of mixed profiles and very few dissociated profiles, whereas the comparison with RL-TR resulted mostly in two profiles depending on the measure: a phonological profile when accuracy was used and a delayed profile when speed was used. In addition, the correlations between early phonemic segmentation and discrimination skills (age 5) and later reading skills (age 17) were significant, and in the group of individuals with dyslexia, early phonemic segmentation skills significantly predicted these later reading skills. Phonological reading deficits are persistent and mainly caused by early phonemic impairments.

Neural correlates of statistical learning in developmental dyslexia: An electroencephalography study

The human brain extracts statistical regularities from the surrounding environment in a process called statistical learning. Behavioural evidence suggests that developmental dyslexia affects statistical learning. However, surprisingly few studies have assessed how developmental dyslexia affects the neural processing underlying this type of learning. We used electroencephalography to explore the neural correlates of an important aspect of statistical learning - sensitivity to transitional probabilities - in individuals with developmental dyslexia. Adults diagnosed with developmental dyslexia (n = 17) and controls (n = 19) were exposed to a continuous stream of sound triplets. Every so often, a triplet ending had a low transitional probability given the triplet's first two sounds ("statistical deviants"). Furthermore, every so often a triplet ending was presented from a deviant location ("acoustic deviants"). We examined mismatch negativity elicited by statistical deviants (sMMN), and MMN elicited by location deviants (i.e., acoustic changes). Acoustic deviants elicited a MMN which was larger in the control group than in the developmental dyslexia group. Statistical deviants elicited a small, yet significant, sMMN in the control group, but not in the developmental dyslexia group. However, the difference between the groups was not significant. Our findings indicate that the neural mechanisms underlying pre-attentive acoustic change detection and implicit statistical auditory learning are both affected in developmental dyslexia.

Phonological Awareness and Rapid Automatized Naming: The Mediating Effect of Word Reading and Spelling in Children with Developmental Dyslexia, Attention Deficit Hyperactivity Disorder, and Mild Intellectual Disability

INTRODUCTION

In learning to read, children learn to integrate orthographic, phonological, and semantic codes into highly specified and redundant lexical representations. The aim is to test a proposed model for the relationship between phonological awareness (PA) and rapid automatized naming (RAN) as mediated by word reading (WR) and spelling (SP) in children with developmental dyslexia (DD), attention deficit hyperactivity disorder (ADHD), and mild intellectual disability (ID).

METHODS

The relation between PA and RAN was found to be mediated by WR and SP in children with DD, ADHD, and mild ID. Three groups of children were included: DD children (N = 70), ADHD children (N = 68), and ID children (N = 69). This is a quantitative correlational, cross-sectional study investigating the strength and direction of relationships among proposed variables.

RESULTS

The relation between PA and RAN was found to be mediated by WR and SP. Based on their correlation analysis, the researcher concluded that there are significant correlations between PA, RAN, WR, and SP. PA correlates positively with RAN and SP. RAN correlates positively with WR and SP.

CONCLUSION

The study extended our knowledge of the relationship between PA and RAN as mediated by WR and SP in children with DD, ADHD, and mild ID. In practice, this is conducive to promote the utilization of "PA" and "RAN" so as to improve the early literacy skills (WR and SP) among children with DD, ADHD, and mild ID.

Audiovisual multisensory integration in individuals with reading and language impairments: A systematic review and meta-analysis

Differences in sensory function have been documented for a number of neurodevelopmental conditions, including reading and language impairments. Prior studies have measured audiovisual multisensory integration (i.e., the ability to combine inputs from the auditory and visual modalities) in these populations. The present study sought to systematically review and quantitatively synthesize the extant literature on audiovisual multisensory integration in individuals with reading and language impairments. A comprehensive search strategy yielded 56 reports, of which 38 were used to extract 109 group difference and 68 correlational effect sizes. There was an overall difference between individuals with reading and language impairments and comparisons on audiovisual integration. There was a nonsignificant trend towards moderation according to sample type (i.e., reading versus language) and publication/small study bias for this model. Overall, there was a small but non-significant correlation between metrics of audiovisual integration and reading or language ability; this model was not moderated by sample or study characteristics, nor was there evidence of publication/small study bias. Limitations and future directions for primary and meta-analytic research are discussed.

Effects of the Visual Praxis-Based Occupational Therapy Education Program on different kinds of reading skills: Single-blind randomized follow-up study

This study aims to examine the long-term effects of Visual Praxis Based Occupational Therapy Program (VP-OTP) on the reading skills of children with Developmental Dyslexia. A total of 126 children with Developmental Dyslexia participated in the study. The participants were then divided into two groups (Intervention and Control groups) of equal sizes (n = 63) using a random number generator without replacement. The intervention group received VP-OTP in two weekly sessions for 8 weeks. All participants were assessed with the Oral Reading Skills and Comprehension Test-II (Sobat®-II) at three time points; pretest, post-test, and follow-up. The intervention group showed promising results as the Sobat®-II's Reading Accuracy, Reading Speed, Fluent Reading, Reading Comprehension Total Score significantly increased after the intervention (p ≤ 0.05) and the scores were maintained at the follow-up (p > 0.05). The VP-OTP intervention provided a maintained improvement in reading skills of children with Developmental Dyslexia.

Distinct reinforcement learning profiles distinguish between language and attentional neurodevelopmental disorders

BACKGROUND

Theoretical models posit abnormalities in cortico-striatal pathways in two of the most common neurodevelopmental disorders (Developmental dyslexia, DD, and Attention deficit hyperactive disorder, ADHD), but it is still unclear what distinct cortico-striatal dysfunction might distinguish language disorders from others that exhibit very different symptomatology. Although impairments in tasks that depend on the cortico-striatal network, including reinforcement learning (RL), have been implicated in both disorders, there has been little attempt to dissociate between different types of RL or to compare learning processes in these two types of disorders. The present study builds upon prior research indicating the existence of two learning manifestations of RL and evaluates whether these processes can be differentiated in language and attention deficit disorders. We used a two-step RL task shown to dissociate model-based from model-free learning in human learners.

RESULTS

Our results show that, relative to neurotypicals, DD individuals showed an impairment in model-free but not in model-based learning, whereas in ADHD the ability to use both model-free and model-based learning strategies was significantly compromised.

CONCLUSIONS

Thus, learning impairments in DD may be linked to a selective deficit in the ability to form action-outcome associations based on previous history, whereas in ADHD some learning deficits may be related to an incapacity to pursue rewards based on the tasks' structure. Our results indicate how different patterns of learning deficits may underlie different disorders, and how computation-minded experimental approaches can differentiate between them.

Developmental dyslexia, developmental coordination disorder and comorbidity discrimination using multimodal structural and functional neuroimaging

Developmental dyslexia (DD) and developmental coordination disorder (DCD) are two common neurodevelopmental disorders with a high co-occurrence rate. This led several authors to postulate that the two disorders share, at least partially, similar neural underpinning. However, even though several studies examined brain differences between typically developing (TD) children and children with either DD or DCD, no previous study directly compared DD, DCD and children with both disorders (COM) using neuroimaging. We acquired structural and resting-state functional MRI images of 136 children (TD = 42, DD = 45, DCD = 20, COM = 29). Difference between TD children and the other groups was assessed using univariate analysis of structural indexes including grey and white matter volumes and functional indexes quantifying activity (fraction of the amplitude of the low frequency fluctuations), local and global connectivity. Regional differences in structural and functional brain indexes were then used to train machine learning models to discriminate among DD, DCD and COM and to find the most discriminant regions. While no imaging index alone discriminated between the three groups, grouping grey and white matter volumes (structural model) or activity, local and global connectivity (functional model) made possible to discriminate among the DD, DCD and COM groups. The most important discrimination was obtained using the functional model, with regions in the cerebellum and the temporal lobe being the most discriminant for DCD and DD children, respectively. Results further showed that children with both DD and DCD have subtle but identifiable brain differences that can only be captured using several imaging indexes pertaining to both brain structure and function.

The determinants of saccade targeting strategy in neurodevelopmental disorders: The influence of suboptimal reading experience

Whether eye-movements deficits are causal in reading disorders (RD) or rather a consequence of linguistic processing difficulty experienced by disabled readers has been extensively debated.Since RD are frequently comorbid with the Neurofibromatosis type1 (NF1), children with NF1 were used as a comparison group for children with dyslexia in this study.Eye movements were recorded while 21 dyslexic, 20 NF1, and 20 typically developing children performed an oculomotor lateralized bisection task. In this experiment, we manipulated the type of stimulus - discrete (words and strings of hashes) versus continuous (solid lines) - and the visual field where the stimulus was displayed (left vs right). The results showed that (1) only proficient readers (TD and NF1 without RD) showed fully developed oculomotor mechanisms for efficient reading, with a clear preferred viewing location located to the left of the word's centre in both visual fields, and fine-tuned saccade targeting guided by the between-character space information and (2) NF1 poor readers mirrored the dyslexic eye movement behaviour, with less accuracy and more variability in saccadic programming, no sensitivity to the discreteness of the stimuli, particularly in the left visual field. We concluded that disruption to oculomotor behaviour reflectsthe fact that many of the processes involved in reading are not yet automatized for children with RD, independently of NF1. This suggests that the differences in saccade targeting strategy between children with and without RD would be secondary consequences of their reduced reading experience.

Disentangling influences of dyslexia, development, and reading experience on effective brain connectivity in children

Altered brain connectivity between regions of the reading network has been associated with reading difficulties. However, it remains unclear whether connectivity differences between children with dyslexia (DYS) and those with typical reading skills (TR) are specific to reading impairments or to reading experience. In this functional MRI study, 132 children (M = 10.06 y, SD = 1.46) performed a phonological lexical decision task. We aimed to disentangle (1) disorder-specific from (2) experience-related differences in effective connectivity and to (3) characterize the development of DYS and TR. We applied dynamic causal modeling to age-matched (n_dys = 25, n_TR = 35) and reading-level-matched (n_dys = 25, n_TR = 22) groups. Developmental effects were assessed in beginning and advanced readers (TR: n_beg = 48, n_adv = 35, DYS: n_beg = 24, n_adv = 25). We show that altered feedback connectivity between the inferior parietal lobule and the visual word form area (VWFA) during print processing can be specifically attributed to reading impairments, because these alterations were found in DYS compared to both the age-matched and reading-level-matched TR. In contrast, feedforward connectivity from the VWFA to parietal and frontal regions characterized experience in TR and increased with age and reading skill. These directed connectivity findings pinpoint disorder-specific and experience-dependent alterations in the brain's reading network.

Effectiveness of digital game-based trainings in children with neurodevelopmental disorders: A meta-analysis

Digital game-based training programs have recently been used to train the cognitive abilities of children with neurodevelopmental disorders (NDDs). However, the effects of training remain controversial. The present meta-analysis explored the effectiveness of digital game-based training in children with NDDs and examined the possible moderators of its effects. Twenty-nine studies with cognitive outcomes in 1535 children were included in the present meta-analysis. The results showed that digital game-based training could significantly enhance the core cognitive abilities of children with each type of NDDs and that training could be used remotely. Meanwhile, task content and game features of digital game-based interventions separately make unique and significant contributions to the training effects, suggesting that the combination of training content and game features could efficiently improve children's cognition. Although the present study revealed that the training benefits could be maintained over a period of time, more studies are needed to explore the retention effects of digital game-based training. The present study provides a comprehensive understanding of the training effects of digital game-based interventions and new insights for future cognitive training design and application.

Failure to consolidate statistical learning in developmental dyslexia

Statistical learning (SL), the ability to pick up patterns in sensory input, serves as one of the building blocks of language acquisition. Although SL has been studied extensively in developmental dyslexia (DD), much less is known about the way SL evolves over time. The handful of studies examining this question were all limited to the acquisition of motor sequential knowledge or highly learned segmented linguistic units. Here we examined memory consolidation of statistical regularities in adults with DD and typically developed (TD) readers by using auditory SL requiring the segmentation of units from continuous input, which represents one of the earliest learning challenges in language acquisition. DD and TD groups were exposed to tones in a probabilistically determined sequential structure varying in difficulty and subsequently tested for recognition of novel short sequences that adhered to this statistical pattern in immediate and delayed-recall sessions separated by a night of sleep. SL performance of the DD group at the easy and hard difficulty levels was poorer than that of the TD group in the immediate-recall session. Importantly, DD participants showed a significant overnight deterioration in SL performance at the medium difficulty level compared to TD, who instead showed overnight stabilization of the learned information. These findings imply that SL difficulties in DD may arise not only from impaired initial learning but also due to a failure to consolidate statistically structured information into long-term memory. We hypothesize that these deficits disrupt the typical course of language acquisition in those with DD.

Shared grey matter correlates of reading and attention

Disorders of reading (developmental dyslexia) and attention (ADHD) have a high rate of comorbidity (25-40%), yet little is known about the neural underpinnings of this phenomenon. The current study investigated the shared and unique neural correlates of reading and attention in 330 typically developing children ages 8-18 from the Philadelphia Neurodevelopmental Cohort. Multiple regression analyses were used to identify regions of the brain where grey matter (GM) volume was associated with reading or attention scores (p < 0.001, cluster FDR p < 0.05). Better attention scores correlated with increased GM in the precuneus and higher reading scores were associated with greater thalamic GM. An exploratory conjunction analysis (p < 0.05, k > 239) found that GM in the caudate and precuneus correlated with both reading and attention scores. These results are consistent with a recent meta-analysis which identified GM reductions in the caudate in both dyslexia and ADHD and reveal potential shared neural correlates of reading and attention.

White matter connectivity in uncinate fasciculus accounts for visual attention span in developmental dyslexia

The present study aimed to investigate the role of connectivity disruptions in two fiber pathways, the uncinate fasciculus (UF) and the frontal aslant tract (FAT), in developmental dyslexia and determine the relationship between the connectivity of these pathways and behavioral performance in children with dyslexia. A total of 26 French children with dyslexia and 31 age-matched control children were included. Spherical deconvolution tractography was used to reconstruct the two fiber pathways. Hindrance-modulated oriented anisotropy (HMOA) was used to measure the connectivity of each fiber pathway in both hemispheres. Only boys with dyslexia showed reduced HMOA in the UF compared to control boys. Furthermore, HMOA of the UF correlated with individual differences in the visual attention span in participants with dyslexia. All significant results found in HMOA of the UF were verified in fractional anisotropy (FA) of the UF using standard diffusion imaging model. This study suggests a differential sex effect on the connectivity disruption in the UF in developmental dyslexia. It also indicates that the UF may play an essential role in the visual attention span deficit in developmental dyslexia.

Prevalence of developmental dyslexia in primary school children: a protocol for systematic review and meta-analysis

BACKGROUND

Developmental dyslexia (DD) is a specific impairment during the acquisition of reading skills and may have a lifelong negative impact on individuals. Reliable estimates of the prevalence of DD serve as the basis for evidence-based health resource allocation and policy making. However, the prevalence of DD in primary school children varies largely across studies. Moreover, it is unclear whether there are differences in prevalence in different genders and writing systems. Hence, the present study aims to conduct a systematic review and meta-analysis to assess the global prevalence of DD and to explore related factors.

METHODS

We will undertake a comprehensive literature search in 14 databases, including EMBASE, PubMed, Web of Science, China National Knowledge Infrastructure and Cochrane, from their inception to June 2021. Cross-sectional and longitudinal studies that describe the prevalence of DD will be eligible. The quality of the included observational studies will be assessed using the Strengthening the Reporting of Observational Studies in Epidemiology statement. The risk of bias will be determined by sensitivity analysis to identify publication bias.

RESULTS

One meta-analysis will be conducted to estimate the prevalence of DD in primary school children. Heterogeneity will be assessed in terms of the properties of subjects (e.g., gender, grade and writing system) and method of diagnosis in the included primary studies. Subgroup analyses will also be performed for population and secondary outcomes.

CONCLUSION

The results will synthesize the prevalence of DD and provide information for policy-makers and public health specialists.

Reduced pattern similarity in brain activation during orthographic processing in children with developmental dyslexia

Intra-individual variability of neural response has been found to be negatively associated with cognitive proficiency and automaticity. However, whether developmental dyslexia (DD) is marked by greater intra-individual neural variability remains unclear. Using a multivariate approach and dual-control group design, the current study aims to examine whether the pattern similarity of brain activation during a visual spelling task is abnormal in children with DD compared to age control and reading control children. We found that there was reduced intra-subject pattern similarity at the left occipito-temporal regions in children with DD than both control groups, suggesting a neural signature of DD. Furthermore, we found that pattern similarity was positively associated with stability of reaction time and reading fluency in both children with DD and typical control children, suggesting that neural stability supports behavioral stability and automaticity during reading.

Decoding of speech information using EEG in children with dyslexia: Less accurate low-frequency representations of speech, not "Noisy" representations

The amplitude envelope of speech carries crucial low-frequency acoustic information that assists linguistic decoding. The sensory-neural Temporal Sampling (TS) theory of developmental dyslexia proposes atypical encoding of speech envelope information < 10 Hz, leading to atypical phonological representations. Here a backward linear TRF model and story listening were employed to estimate the speech information encoded in the electroencephalogram in the canonical delta, theta and alpha bands by 9-year-old children with and without dyslexia. TRF decoding accuracy provided an estimate of how faithfully the children's brains encoded low-frequency envelope information. Between-group analyses showed that the children with dyslexia exhibited impaired reconstruction of speech information in the delta band. However, when the quality of speech encoding for each child was estimated using child-by-child decoding models, then the dyslexic children did not differ from controls. This suggests that children with dyslexia encode neither "noisy" nor "normal" representations of the speech signal, but different representations.

How visual attention span and phonological skills contribute to N170 print tuning: An EEG study in French dyslexic students

Developmental dyslexia is a disorder characterized by a sustainable learning deficit in reading. Based on ERP-driven approaches focusing on the visual word form area, electrophysiological studies have pointed a lack of visual expertise for written word recognition in dyslexic readers by contrasting the left-lateralized N170 amplitudes elicited by alphabetic versus non-alphabetic stimuli. Here, we investigated in 22 dyslexic participants and 22 age-matched control subjects how two behavioural abilities potentially affected in dyslexic readers (phonological and visual attention skills) contributed to the N170 expertise during a word detection task. Consistent with literature, dyslexic participants exhibited poorer performance in these both abilities as compared to healthy subjects. At the brain level, we observed (1) an unexpected preservation of the N170 expertise in the dyslexic group suggesting a possible compensatory mechanism and (2) a modulation of this expertise only by phonological skills, providing evidence for the phonological mapping deficit hypothesis.

EEG based functional brain networks analysis in dyslexic children during arithmetic task

Developmental Dyslexia is a neuro-developmental disorder that often refers to a phonological processing deficit regardless of average IQ. The present study investigated the distinct functional changes in brain networks of dyslexic children during arithmetic task performance using an electroencephalogram. Fifteen dyslexic children and fifteen normally developing children (NDC) were recruited and performed an arithmetic task. Brain functional network measures such as node strength, clustering coefficient, characteristic pathlength and small-world were calculated using graph theory methods for both groups. Task performance showed significantly less performance accuracy in dyslexics against NDC. The neural findings showed increased connectivity in the delta band and reduced connectivity in theta, alpha, and beta band at temporoparietal, and prefrontal regions in dyslexic group while performing the task. The node strengths were found to be significantly high in delta band (T3, O1, F8 regions) and low in theta (T5, P3, Pz regions), beta (Pz) and gamma band (T4 and prefrontal regions) during the task in dyslexics compared to the NDC. The clustering coefficient was found to be significantly low in the dyslexic group (theta and alpha band) and characteristic pathlength was found to be significantly high in the dyslexic group (theta and alpha band) compared to the NDC group while performing task. In conclusion, the present study shows evidence for poor fact-retrieval mechanism and altered network topology in dyslexic brain networks during arithmetic task performance.

Global reading processes in children with high risk of dyslexia: a scanpath analysis

The study presents the first systematic comparison of the global reading processes via scanpath analysis in Russian-speaking children with and without reading difficulties. First, we compared basic eye-movement characteristics in reading sentences in two groups of children in grades 1 to 5 (N = 72 in high risk of developmental dyslexia group and N = 72 in the control group). Next, using the scanpath method, we investigated which global reading processes these children adopt to read the entire sentence and how these processes differ between the groups. Finally, we were interested in the timeframe of the change in the global reading processes from the 1st to the 5th grades for both groups. We found that the main difference in word-level measures between groups was the reading speed reflected in fixation durations. However, the examination of the five identified global reading processes revealed qualitative similarities in reading patterns between groups. Children in the control group progressed quickly and by the 4th grade engaged in an adult-like fluent reading process. The high-risk group started with the beginner reading process, then similar to first graders in the control group, engaged mostly in the intermediate and upper-intermediate reading processes in 2nd to 4th grades. They reach the advanced process in the 5th grade, the same pattern preferred by the control group second graders. Overall, the scanpath analysis reveals that although there are quantitative differences in the word-level eye-tracking measures between groups, qualitatively children in the high-risk group read on par with typically developing peers but with a 3-year reading delay.

Exposure to multiple metals and the risk of dyslexia - A case control study in Shantou, China

Environmental heavy metal exposure has been considered to be the risk factor for neurodevelopmental disorders in children. However, the available data on the associations between multiple metals exposure and the risk of dyslexia in China are limited. The purpose of our study was to examine the associations between urinary metal concentrations and Chinese dyslexia risk. A total of 56 Chinese dyslexics and 60 typically developing children were recruited. The urinary concentration of 13 metals were measured by inductively coupled plasma-mass spectrometer (ICP-MS). Binary logistic regression and the Probit extension of Bayesian kernel machine regression (BKMR-P) were used to explore the associations between multiple metal exposure and the risk of Chinese dyslexia. Our results indicated that Co, Zn and Pb were significantly associated with Chinese dyslexia in the multiple-metal exposure model. After adjusting the covariates, a positive association was observed between Pb and the risk of Chinese dyslexia, with the odds ratio (OR) in the highest quartiles of 6.81 (95%CI: 1.07-43.19; p-trend = 0.024). Co and Zn were negatively associated with the risk of Chinese dyslexia. Compared to the lowest quartile, the ORs of Co and Zn in the highest quartile are 0.13 (95%CI: 0.02-0.72; p-trend = 0.026) and 0.18 (95%CI: 0.04-0.88; p-trend = 0.038), respectively. In addition, BKMR-P analysis indicated that with the cumulative level across Co, Zn and Pb increased, the risk of Chinese dyslexia gradually declined and then rebounded, albeit non-significantly, and Pb was the major contributor in this association. In general, the urinary concentrations of Co, Zn and Pb were significantly associated with Chinese dyslexia. More prospective studies are needed to confirm the health effects of multiple metals exposure in children with Chinese dyslexia.

Lateralization of early orthographic processing during natural reading is impaired in developmental dyslexia

Skilled reading requires specialized visual cortical processing of orthographic information and its impairment has been proposed as a potential correlate of compromised reading in dyslexia. However, which stage of orthographic information processing during natural reading is disturbed in dyslexics remains unexplored. Here we addressed this question by simultaneously measuring the eye movements and EEG of dyslexic and control young adults during natural reading. Isolated meaningful sentences were presented at five inter-letter spacing levels spanning the range from minimal to extra-large spacing, and participants were instructed to read the text silently at their own pace. Control participants read faster, performed larger saccades and shorter fixations compared to dyslexics. While reading speed peaked around the default letter spacing, saccade amplitude increased and fixation duration decreased with the increase of letter spacing in both groups. Lateralization of occipito-temporal fixation-related EEG activity (FREA) was found in three consecutive time intervals corresponding to early orthographic processing in control readers. Importantly, the lateralization in the time range of the first negative left occipito-temporal FREA peak was specific for first fixations and exhibited an interaction effect between reading ability and letter spacing. The interaction originated in the significant decrease of FREA lateralization at extra-large compared to default letter spacing in control readers and the lack of lateralization in both letter spacing conditions in the case of dyslexics. These findings suggest that expertise-driven hemispheric functional specialization for early orthographic processing thought to be responsible for letter identity extraction during natural reading is compromised in dyslexia.

Comparative research on neural dysfunction in children with dyslexia under different writing systems: A meta-analysis study

Developmental dyslexia is a special learning disorder which is prevalent in all languages. A central question in dyslexia is whether the neural mechanism of their defects is universal or distinct in different writing systems. Using meta-analytic approach, we created meta-images using activation abnormalities in Chinese and alphabetic children with dyslexia to find convergence and divergence under different writing systems. The results revealed that dyslexic children have a universal attention-related dysfunction with hypoactivation in the left inferior frontal cortex (IFC) and the anterior cingulate cortex (ACC) under different writing systems, in spite of differences of degree and spatial extent in those regions. Alphabetic dyslexic children additionally showed hypoactivation in the left occipito-temporo-parietal regions. Chinese dyslexic children showed specific hyperactivation in the right postcentral gyrus, the left rectus, and the right middle temporal gyrus. The present meta-analysis for the first time showed both shared and distinct abnormalities in children with dyslexia under Chinese and alphabetic writing systems.

The influence of intelligence and cognitive abilities on the reading ability of Japanese students with developmental disorders

OBJECTIVE

We examined the differences in reading skills between Japanese students with developmental dyslexia (DD) having developmental disorders who had borderline IQ (BIQ) and those who had normal IQ (NIQ), and the influence of cognitive factors through subscale scores of the Wechsler Intelligence Scale for Children - Fourth Edition on the reading skills of all students with DD having developmental disorders.

METHODS

One-way analysis of variance revealed differences in reading scores among the four groups (DD with NIQ, DD with BIQ, as well as non-DD with NIQ and non-DD with BIQ as control groups). To examine the influence of cognitive factors, we used multiple regression analysis for all participants, and then for participants with DD.

RESULTS

Regarding hiragana nonword fluency reading, no difference was observed between the two DD groups, and cognitive factors did not affect the performance of all participants with DD. Concerning hiragana word fluency reading, DD with NIQ group performed better than DD group with BIQ, and working memory index affected reading skills of participants with DD. Regarding kanji accuracy reading, DD with NIQ group performed better than DD with BIQ group, and processing speed index affected performance of participants with DD.

CONCLUSIONS

The results of hiragana reading suggest that the two DD groups shared similar weak sub-lexical route processing, while the acquisition of lexical route processing was hindered by lower IQ and weak phonological working memory in transparent phonographic hiragana reading. For kanji reading, lower IQ and weak visuomotor processing ability hampered the learning of visually complex logographic kanji characters.

Factors relevant to work participation from the perspective of adults with developmental dyslexia: a systematic review of qualitative studies

Background

This review is focused on workers with developmental dyslexia (DD). In this review DD is considered an expression of neurodiversity, a consequence of a natural variant of the brain. Evidence was synthesized to explore which factors workers with DD consider relevant for their participation in work and whether these factors reflect shifts in the concepts of health and sustainable employability. The factors were classified according to the International Classification of Functioning, Disability and Health (ICF), adapted for occupational health.

Methods

A systematic review of qualitative studies was performed. Two search strings were used to determine the population and the context of work. The factors were classified using a recently proposed rearrangement of the ICF scheme that places participation in a central position and incorporates preliminary lists of work-related environmental factors and personal factors.

Results

Fifty-one factors were found that appeared in 35% or more of the included studies and that were relevant to work participation according to the workers themselves. These factors were dispersed over all ICF categories. In the category Functions and Structures (11 factors), most of the factors had negative connotations. In the category Activities (9 factors), all the factors cause difficulties, except speaking (which is ambiguous). In the category Participation (4 factors), the formal relationships are important for the degree of participation. Overall, more than half of the factors are environmental (18) or personal (9) and they both hinder and facilitate work participation.

Conclusions

The results of this review give an indication for the importance of the biopsychosocial model as a relevant approach for people with a disability in the world of work. This review also adds data for the usefulness of the proposals for the reconsideration of the ICF scheme. The data has not (yet) returned any visible trends revealing that the concept of neurodiversity is common in organizations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13436-x.

Atypical delta-band phase consistency and atypical preferred phase in children with dyslexia during neural entrainment to rhythmic audio-visual speech

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Children with and without dyslexia showed consistent phase entrainment.

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Dyslexic children had significantly reduced delta band phase consistency.

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Dyslexic children had a different preferred phase in delta compared to controls.

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The dyslexic brain showed faster pre-stimulus delta band angular velocity.

According to the sensory-neural Temporal Sampling theory of developmental dyslexia, neural sampling of auditory information at slow rates (<10 Hz, related to speech rhythm) is atypical in dyslexic individuals, particularly in the delta band (0.5–4 Hz). Here we examine the underlying neural mechanisms related to atypical sampling using a simple repetitive speech paradigm. Fifty-one children (21 control children [15M, 6F] and 30 children with dyslexia [16M, 14F]) aged 9 years with or without developmental dyslexia watched and listened as a ‘talking head’ repeated the syllable “ba” every 500 ms, while EEG was recorded. Occasionally a syllable was “out of time”, with a temporal delay calibrated individually and adaptively for each child so that it was detected around 79.4% of the time by a button press. Phase consistency in the delta (rate of stimulus delivery), theta (speech-related) and alpha (control) bands was evaluated for each child and each group. Significant phase consistency was found for both groups in the delta and theta bands, demonstrating neural entrainment, but not the alpha band. However, the children with dyslexia showed a different preferred phase and significantly reduced phase consistency compared to control children, in the delta band only. Analysis of pre- and post-stimulus angular velocity of group preferred phases revealed that the children in the dyslexic group showed an atypical response in the delta band only. The delta-band pre-stimulus angular velocity (−130 ms to 0 ms) for the dyslexic group appeared to be significantly faster compared to the control group. It is concluded that neural responding to simple beat-based stimuli may provide a unique neural marker of developmental dyslexia. The automatic nature of this neural response may enable new tools for diagnosis, as well as opening new avenues for remediation.

The relationship between cognitive control and lexical conflict resolution in developmental dyslexia

Previous studies have revealed that cognitive control functions contribute to the resolution of lexical interference. Both cognitive control (CC) deficits and reduced speed of lexical retrieval in Rapid Automatized Naming (RAN) tasks are characteristics of Developmental Dyslexia (DD), but it is still not fully understood how these deficits relate to each other and to reading problems. To examine this question, we tested adolescents with DD (n = 38), poor readers (PR; n = 25) and typical readers (TR; n = 33) matched on age and IQ, on CC functions with Stroop, Stop Signal, Simon, Backward Digit Span and n-back tasks and on lexical retrieval and lexical conflict resolution with RAN of pictures in semantically homogeneous vs. mixed trials. As expected, in the blocked RAN Task DD individuals showed longer naming times and a greater effect of lexical conflict resolution (indexed by difference scores of naming times in the homogeneous and mixed conditions) than TR participants. We also found significant group differences (TR = PR > DD) in CC measures. Naming time was associated with CC, while the lexical interference effect did not show any association with this set of abilities. These findings suggest that DD individuals show impairments in multiple cognitive functions, such as cognitive control, lexical retrieval and lexical conflict resolution. Our results also suggest that CC functions are involved in lexical retrieval, but we have not found evidence for their involvement in lexical conflict resolution processes.

Shallow or deep? The impact of orthographic depth on visual processing impairments in developmental dyslexia

The extent to which impaired visual and phonological mechanisms may contribute to the manifestation of developmental dyslexia across orthographies of varying depth has yet to be fully established. By adopting a cross-linguistic approach, the current study aimed to explore the nature of visual and phonological processing in developmental dyslexic readers of shallow (Italian) and deep (English) orthographies, and specifically the characterisation of visual processing deficits in relation to orthographic depth. To achieve this aim, we administered a battery of non-reading visual and phonological tasks. Developmental dyslexics performed worse than typically developing readers on all visual and phonological tasks. Critically, readers of the shallow orthography were disproportionately impaired on visual processing tasks. Our results suggest that the impaired reading and associated deficits observed in developmental dyslexia are anchored by dual impairments to visual and phonological mechanisms that underpin reading, with the magnitude of the visual deficit varying according to orthographic depth.

Enhanced reading abilities is modulated by faster visual spatial attention

Research has shown improved reading following visual magnocellular training in individuals with dyslexia. Many studies have demonstrated how the magnocellular pathway controls visual spatial attention. Therefore, we have investigated the relationship between magnocellular pathway and visual spatial attention deficits in dyslexia in order to better understand how magnocellular-based interventions may help children to learn to read. Magnocellular function, visual spatial attention, and reading abilities of thirty elementary school students with dyslexia, aged between 8 and 10, were measured. The experimental group received magnocellular-based visual motion training for 12 sessions, while the control group received neutral sessions. All tests were repeated at the end of the training and after 1 month. The magnocellular functioning, visual spatial attention, and reading abilities of the experimental group improved significantly compared to the controls. Additionally, improvement in reaction time of invalid conditions predicted improvements in saccadic eye movements. We conclude that visual magnocellular training improved saccadic eye movement control, visual spatial orientation, and reading ability.

Altered brain network topology during speech tracking in developmental dyslexia

Developmental dyslexia is often accompanied by altered phonological processing of speech. Underlying neural changes have typically been characterized in terms of stimulus- and/or task-related responses within individual brain regions or their functional connectivity. Less is known about potential changes in the more global functional organization of brain networks. Here we recorded electroencephalography (EEG) in typical and dyslexic readers while they listened to (a) a random sequence of syllables and (b) a series of tri-syllabic real words. The network topology of the phase synchronization of evoked cortical oscillations was investigated in four frequency bands (delta, theta, alpha and beta) using minimum spanning tree graphs. We found that, compared to syllable tracking, word tracking triggered a shift toward a more integrated network topology in the theta band in both groups. Importantly, this change was significantly stronger in the dyslexic readers, who also showed increased reliance on a right frontal cluster of electrodes for word tracking. The current findings point towards an altered effect of word-level processing on the functional brain network organization that may be associated with less efficient phonological and reading skills in dyslexia.

Lateralization of word and face processing in developmental dyslexia and developmental prosopagnosia

In right-handed adults, face processing is lateralized to the right hemisphere and visual word processing to the left hemisphere. According to the many-to-many account (MTMA) of functional cerebral organization this lateralization pattern is partly dependent on the acquisition of literacy. Hence, the MTMA predicts that: (i) processing of both words and faces should show no or at least less lateralization in individuals with developmental dyslexia compared with controls, and (ii) lateralization in word processing should be normal in individuals with developmental prosopagnosia whereas lateralization in face processing should be absent. To test these hypotheses, 21 right-handed adults with developmental dyslexia and 21 right-handed adults with developmental prosopagnosia performed a divided visual field paradigm with delayed matching of faces, words and cars. Contrary to the predictions, we find that lateralization effects in face processing are within the normal range for both developmental dyslexics and prosopagnosics. Moreover, the group with developmental dyslexia showed right hemisphere lateralization for word processing. We argue that these findings are incompatible with the specific predictions of the MTMA.

Atypical Reinforcement Learning in Developmental Dyslexia

OBJECTIVES

According to the Procedural Deficit Hypothesis, abnormalities in corticostriatal pathways could account for the language-related deficits observed in developmental dyslexia. The same neural network has also been implicated in the ability to learn contingencies based on trial and error (i.e., reinforcement learning [RL]). On this basis, the present study tested the assumption that dyslexic individuals would be impaired in RL compared with neurotypicals in two different tasks.

METHODS

In a probabilistic selection task, participants were required to learn reinforcement contingencies based on probabilistic feedback. In an implicit transitive inference task, participants were also required to base their decisions on reinforcement histories, but feedback was deterministic and stimulus pairs were partially overlapping, such that participants were required to learn hierarchical relations.

RESULTS

Across tasks, results revealed that although the ability to learn from positive/negative feedback did not differ between the two groups, the learning of reinforcement contingencies was poorer in the dyslexia group compared with the neurotypicals group. Furthermore, in novel test pairs where previously learned information was presented in new combinations, dyslexic individuals performed similarly to neurotypicals.

CONCLUSIONS

Taken together, these results suggest that learning of reinforcement contingencies occurs less robustly in individuals with developmental dyslexia. Inferences for the neuro-cognitive mechanisms of developmental dyslexia are discussed.

Atypical viewing position effect in developmental dyslexia: A behavioural and modelling investigation

The probability of recognizing a word depends on the position of fixation during processing. In typical readers, the resulting word-recognition curves are asymmetrical, showing a left-of-centre optimal viewing position (OVP). First, we report behavioural results from dyslexic participants who show atypical word-recognition curves characterized by the OVP being right of centre with recognition probability being higher on the rightmost than on the leftmost letters. Second, we used BRAID, a Bayesian model of word recognition that implements gaze position, an acuity gradient, lateral interference and a visual attention component, to examine how variations in the deployment of visual attention would affect the OVP curves. We show that the atypical dyslexic curves are well simulated assuming a narrow distribution of visual attention and a shifting of visual attention towards the left visual field. These behavioural and modelling findings are discussed in light of current theories of visual attention deficits in developmental dyslexia.

Maladaptive compensation of right fusiform gyrus in developmental dyslexia: A hub-based white matter network analysis

Cognitive theories have been proposed to clarify the causes and symptoms of dyslexia. However, correlations between local network parameters of white matter connectivity and literacy skills remain poorly known. An unbiased hypothesis-free approach was adopted to examine the correlations between literacy symptoms (reading and spelling) and hub-based white matter networks' connectivity parameters [nodal degree fractional anisotropy (FA) values] of 90 brain regions based on Anatomical Atlas Labels (AAL) in a group of French children with dyslexia aged 9-14 years. Results revealed that the higher the right fusiform gyrus's (FFG) nodal degree FA values, the lower the reading accuracy for words and pseudowords in dyslexic children. The results indicate that the severity of word/pseudoword reading symptoms in dyslexia relates to a white matter network centered around the right FFG. The negative correlation between right FFG network connectivity and reading accuracy, in particular pseudoword reading accuracy, suggests that right FFG represents a maladaptive compensation towards a general orthography-to-phonology decoding ability in developmental dyslexia.

Animal models of developmental dyslexia: Where we are and what we are missing

Developmental dyslexia (DD) is a complex neurodevelopmental disorder and the most common learning disability among both school-aged children and across languages. Recently, sensory and cognitive mechanisms have been reported to be potential endophenotypes (EPs) for DD, and nine DD-candidate genes have been identified. Animal models have been used to investigate the etiopathological pathways that underlie the development of complex traits, as they enable the effects of genetic and/or environmental manipulations to be evaluated. Animal research designs have also been linked to cutting-edge clinical research questions by capitalizing on the use of EPs. For the present scoping review, we reviewed previous studies of murine models investigating the effects of DD-candidate genes. Moreover, we highlighted the use of animal models as an innovative way to unravel new insights behind the pathophysiology of reading (dis)ability and to assess cutting-edge preclinical models.