Developmental dyslexia: The visual attention span deficit hypothesis

The perceptual span in dyslexic reading and visual search

Many studies have attempted to identify the root cause of dyslexia. Different theories of dyslexia have proposed either a phonological, attentional, or visual deficit. While research has used eye-tracking to study dyslexia, only two previous studies have used the moving-window paradigm to explore the perceptual span in dyslexic reading, and none have done so in visual search. The present study analysed the perceptual span using both reading and visual search tasks to identify language-independent attentional impairments in dyslexics. We found equivocal evidence that the perceptual span was impaired in dyslexic reading and no evidence of impairment in visual search. However, dyslexic participants did show deficits in the visual search task, with lower search accuracy and shorter saccades compared with controls. These results lend support for a visual, rather than attentional or phonological, account of dyslexia.

Cost and benefit of parafoveal information during reading acquisition as revealed by finger movement patterns

Contrary to expert readers, children learning to read have limited ability to preprocess letters in parafoveal vision. Parafoveal letters induce crowding cost: the features of neighboring letters interfere with target letter identification. We longitudinally studied the weight of parafoveal cost and benefit in two group of children (N = 42), during their first school year (Group 1) and at the end of second school year (Groupe 2). Using a novel digit-tracking method, a blurred text was presented and rendered unblurred by touching the screen, allowing the user to discover a window of visible text as the finger moved along it. We compared two conditions: (1) a large window, where crowding was enhanced by the presence of parafoveal information; (2) a small window, where crowding was suppressed by blurred parafoveal information. Finger kinematics were simultaneously recorded. We found that at the beginning of first-grade, digital fixations - brief slowing or stopping of the finger on a specific point - are significantly longer in the large compared to the small window condition, as parafoveal crowding increases text processing difficulty. This effect diminishes and disappears at the end of second-grade as reading performance improves. In the large window condition, longer digital saccades - rapid movements of the finger changing position - appear by the end of first grade suggesting that parafoveal exposure become more beneficial than harmful when children acquire basic reading skills. Our results show that in beginning readers, crowding has a cognitive cost that interfere with the speed of the learning reading process. Our findings are relevant to the field of education by showing that visual crowding in first grade should not be underestimated.

Visual processing and decision-making in autism and dyslexia: Insights from cross-syndrome approaches

Atypical visual processing has been reported in developmental conditions like autism and dyslexia, and some accounts propose a causal role for visual processing in the development of these conditions. However, few studies make direct comparisons between conditions, or use sufficiently sensitive methods, meaning that it is hard to say whether atypical visual processing tells us anything specific about these conditions, or whether it reflects a more general marker of atypical development. Here I review findings from two computational modelling approaches (equivalent noise and diffusion modelling) and related electroencephalography (EEG) indices which we have applied to data from autistic, dyslexic and typically developing children to reveal how the component processes involved in visual processing and decision-making are altered in autism and dyslexia. The results identify both areas of convergence and divergence in autistic and dyslexic children's visual processing and decision-making, with implications for influential theoretical accounts such as weak central coherence, increased internal noise, and dorsal-stream vulnerability. In both sets of studies, we also see considerable variability across children in all three groups. To better understand this variability, and further understand the convergence and divergence identified between conditions, future studies would benefit from studying how the component processes reviewed here relate to transdiagnostic dimensions, which will also give insights into individual differences in visual processing and decision-making more generally.

Oculomotor Rehabilitation Improves Reading Abilities in Dyslexic Children With Concurrent Eye Movement Abnormalities

The oculomotor abnormalities have been reported in some dyslexic children. The purpose of the study was to evaluate the effects of oculomotor rehabilitation on the reading performance of dyslexic children. Subjects were 50 dyslexic children. Those with oculomotor abnormalities (n = 30) were randomly assigned into 2 groups matched for age. The case group received oculomotor rehabilitation. The rehabilitation program consists of 3 different exercises. The reading and dyslexia tests were performed before and after the intervention. The correct scores of reading tests in the case group posttest increased significantly compared with the control group, and there is a significant difference between the two groups (P = .001). The positive effects of oculomotor rehabilitation on the reading performance of dyslexic children confirmed that the oculomotor program could be a practical tool for improving reading performance in dyslexic children.

Revisiting the definition of dyslexia

The International Dyslexia Association definition of dyslexia was updated 20 years ago and has been referenced frequently in research and practice. In this paper, researchers from the Florida Center for Reading Research consider the components of the definition and make recommendations for revisions. These include recognizing the persistence of word-reading, decoding, and spelling difficulties, acknowledging the multifactorial causal basis of dyslexia, clarifying exclusionary factors, and denoting comorbidity with other developmental disorders. It is also suggested that the academic and psychosocial consequences of dyslexia be highlighted to reinforce a preventive service delivery model. Lastly, the inclusion of dyslexia within a specific learning disability category is supported.

Pulsed lighting for adults with Dyslexia: very limited impact, confined to individuals with severe reading deficits

The goal of this study is to evaluate the impact of pulsed lighting on the reading performance of young adults with dyslexia. A total of 42 participants were recruited, including individuals diagnosed with developmental dyslexia and adults without reported reading difficulties. The severity of each participant's reading deficit was assessed on a continuous scale using a reading impairment score, derived from four reading tests: an isolated-word reading test, a pseudoword reading test, and two reading fluency tests. The impairment score ranged from 0 (no impairment) to 4 (severe impairment across all tests). To examine the potential effect of pulsed lighting, we measured (1) sentence reading speed, expressed as a reading accessibility index (ACC), and (2) text comprehension, expressed as a comprehension score. These measures were taken under three lighting conditions: standard lighting, pulsed lighting, and a combination of the two. Linear mixed-effects models were applied to assess the effects of lighting on ACC and comprehension, controlling for the reading impairment score. We found no effect of lighting conditions on either ACC or comprehension, except in the most impaired readers, who showed a small but significant increase of 7% in ACC. However, even with pulsed lighting, impaired readers did not reach the performance level of skilled adult readers. In conclusion, the study did not demonstrate a clear positive impact of pulsed lighting on the reading skills of adults with dyslexia.

Foveal crowding in children with developmental dyslexia

Excessive crowding in the visual periphery has been demonstrated in children with developmental dyslexia (DD). However, less is known about crowding in the fovea, even though foveal crowding is at least equally important, as reading is mostly accomplished through foveal vision. Here we used a special set of digit stimuli (Pelli fonts) to measure foveal crowding in DD and DD + ADHD children, and compared it to that in TD (typically developing) and ADHD children. We also used the Chinese reading acuity charts (C-READ) to assess the maximum reading speed and reading acuity, along with tests to evaluate cognitive attributes including phonological awareness, rapid automatized naming, morphological awareness, and orthographic knowledge. The results indicate significantly stronger foveal crowding in the DD and DD + ADHD groups, as well as in the ADHD group, than in the TD group. Furthermore, the DD and DD + ADHD groups exhibited poorer maximum reading speed and reading acuity compared to the ADHD and TD groups. Within the two DD groups, the slower maximum reading speed and higher reading acuity can be predicted by stronger foveal crowding. In addition, the DD and DD + ADHD groups performed the worst in four cognitive skills, with the DD group showing negative correlations between foveal crowding and performances across all these skills. Our findings thus move beyond previously well-documented peripheral crowding in dyslexia, and the easy administration of the Pelli-font-based crowding test may be useful for early diagnosis of developmental dyslexia in young children.

Neural bases of reading fluency: A systematic review and meta-analysis

Reading fluency, the ability to read quickly and accurately, is a critical marker of successful reading and is notoriously difficult to improve in reading disabled populations. Despite its importance to functional literacy, fluency is a relatively under-studied aspect of reading, and the neural correlates of reading fluency are not well understood. Here, we review the literature of the neural correlates of reading fluency as well as rapid automatized naming (RAN), a task that is robustly related to reading fluency. In a qualitative review of the neuroimaging literature, we evaluated structural and functional MRI studies of reading fluency in readers from a range of skill levels. This was followed by a quantitative activation likelihood estimate (ALE) meta-analysis of fMRI studies of reading speed and RAN measures. We anticipated that reading speed, relative to untimed reading and reading-related tasks, would harness ventral reading pathways that are thought to enable the fast, visual recognition of words. The qualitative review showed that speeded reading taps the entire canonical reading network. The meta-analysis indicated a stronger role of the ventral reading pathway in rapid reading and rapid naming. Both reviews identified regions outside the canonical reading network that contribute to reading fluency, such as the bilateral insula and superior parietal lobule. We suggest that fluent reading engages both domain-specific reading pathways as well as domain-general regions that support overall task performance and discuss future avenues of research to expand our understanding of the neural bases of fluent reading.

Revealing the Causes of Dyslexia through a Differential Diagnosis, a Short-Term Effective Treatment and an Appropriate Conceptual Framework

Various different impairments and their interactions can cause reading problems referred to as "dyslexia". Since reading requires the interaction of many abilities, the impairment of each of these abilities can result in dyslexia. Therefore, the diagnosis must differentiate various kinds of dyslexia. The diagnosis of a certain kind of dyslexia cannot be delimited to the investigation and description of symptoms but must also include the investigation of the causes of each kind of dyslexia. For this purpose, a scientifically unequivocal concept of causation and appropriate methods are needed to distinguish them from co-existing impairments that have no causal influence on reading performance. The results of applying these methods cannot be adequately accounted for by a non-scientific, intuitive understanding of necessary and sufficient conditions and causation. The methods suitable for revealing the causes of dyslexia are described in detail, and the results of applying these methods in experiments, in which 356 children with developmental dyslexia participated, are reviewed. Since the concepts of "necessary" and "sufficient" conditions and "causation" proposed in the philosophy of science are not suitable for describing causes of dyslexia and their interaction, they are replaced by a more detailed, experimentally based conceptual framework that provides an accurate description of the conditions required for correct reading and the causes of dyslexia.

Low literacy skills in adults can be largely explained by basic linguistic and domain-general predictors

Introduction

Despite having sufficient formal education, a large group of people cannot complete everyday tasks like reading, writing, or making basic calculations. Regarding reading, millions of people are not able to understand more complex texts despite the ability to read simple words or sentences; they have low literacy skills. Even though this problem has been known for decades, the causes and predictors of their poor reading comprehension skills are not fully explored. Socioeconomic, sociodemographic, and reading-related (i.e., linguistic) factors, especially of English-speaking participants and thus users of an opaque orthography, were often assessed. The goal of this study was to examine which linguistic, domain-general, or numerical factors predict substandard complex text reading as the core symptom of low literacy skills in adulthood.

Methods

To this end, we assessed a group of German-speaking participants-users of a transparent orthography-who are at risk for complex text reading deficits.

Results

The results indicated that linguistic variables (reduced word/pseudoword reading, weaker oral semantic and grammatical comprehension), working memory, and age predicted lower performance in text comprehension. This model explained 73% of the total variance, indicating that most of the deficits in complex text reading can be explained by a group of basic underlying linguistic and domain-general factors.

Discussion

We conclude that interventions for adults with low literacy skills and others at risk for complex text reading deficits should address word/pseudoword reading and focus on both written and oral comprehension.

Children with dyslexia show no deficit in exogenous spatial attention but show differences in visual encoding

In the search for mechanisms that contribute to dyslexia, the term "attention" has been invoked to explain performance in a variety of tasks, creating confusion since all tasks do, indeed, demand "attention." Many studies lack an experimental manipulation of attention that would be necessary to determine its influence on task performance. Nonetheless, an emerging view is that children with dyslexia have an impairment in the exogenous (automatic/reflexive) orienting of spatial attention. Here we investigated the link between exogenous attention and reading ability by presenting exogenous spatial cues in the multi-letter processing task-a task relevant for reading. The task was gamified and administered online to a large sample of children (N = 187) between 6 and 17 years. Children with dyslexia performed worse overall at rapidly recognizing and reporting strings of letters. However, we found no evidence for a difference in the utilization of exogenous spatial cues, resolving two decades of ambiguity in the field. Previous studies that claimed otherwise may have failed to distinguish attention effects from overall task performance or found spurious group differences in small samples. RESEARCH HIGHLIGHTS: We manipulated exogenous visual spatial attention using pre-cues in a task that is relevant for reading and we see robust task effects of exogenous attention. We found no evidence for a deficit in utilizing exogenous spatial pre-cues in children with dyslexia. However, children with dyslexia showed reduced recognition ability for all letter positions. Children with dyslexia were just as likely to make letter transposition errors as typical readers.

Developmental surface dyslexia and dysgraphia in a child with corpus callosum agenesis: an approach to diagnosis and treatment

We present a case study detailing cognitive performance, functional neuroimaging, and effects of a hypothesis-driven treatment in a 10-year-old girl diagnosed with complete, isolated corpus callosum agenesis. Despite having average overall intellectual abilities, the girl exhibited profound surface dyslexia and dysgraphia. Spelling treatment significantly and persistently improved her spelling of trained irregular words, and this improvement generalized to reading accuracy and speed of trained words. Diffusion weighted imaging revealed strengthened intrahemispheric white matter connectivity of the left temporal cortex after treatment and identified interhemispheric connectivity between the occipital lobes, likely facilitated by a pathway crossing the midline via the posterior commissure. This case underlines the corpus callosum's critical role in lexical reading and writing. It demonstrates that spelling treatment may enhance interhemispheric connectivity in corpus callosum agenesis through alternative pathways, boosting the development of a more efficient functional organization of the visual word form area within the left temporo-occipital cortex.

Reading problems and their connection with visual search and attention

Attention has been hypothesized to act as a sequential gating mechanism for the orderly processing of letters and words. These same visuoattentional processes are often assumed to partake in some but not all types of visual search. In the current study, 24 dyslexic and 36 typical readers completed an attentionally demanding visual conjunction search. Visual feature search served as an internal control. It has been suggested that reading problems should go hand in hand with specific problems in visual conjunction search-particularly elevated conjunction search slopes (time per search item)-often interpreted as a problem with visual attention. Results showed that reading problems were associated with slower visual search, especially conjunction search. However, reading deficits were not associated with increased conjunction search slopes but instead with increased search intercepts, traditionally not interpreted as reflecting attention. We discuss these results in the context of hypothesized visuoattentional problems in dyslexia. Remaining open to multiple interpretations of the data, the current study demonstrates that difficulties in visual search are associated with reading problems, in accordance with growing literature on visual cognition problems in developmental dyslexia.

Reading Skill Profiles in School-Aged Italian-Speaking Children: A Latent Profile Analysis Investigation into the Interplay of Decoding, Comprehension and Attentional Control

Our study examined the complex relationships among reading performance (decoding, comprehension) and language, visuo-spatial, and attentional control abilities in 115 Italian-speaking children. Latent profile analysis was used to identify distinct clusters of participants showcasing quantitative differences in decoding skills, including word, pseudo-word, text reading speed and accuracy. Then, we used this classification to investigate group differences in a variety of linguistic, working memory, and visuo-spatial tasks, as well as in reading comprehension skills, by means of multivariate and univariate tests. Our results reveal significant links between reading proficiency and several key factors: language skills, visuo-spatial abilities, and attentional control. These findings illuminate the nuanced impact of domain-general processes that govern a series of linguistic and visuo-perceptive subcomponents during reading tasks. Additionally, using dominance analysis, predictors of written text comprehension were identified. Our findings suggest that effective reading comprehension relies on a synergistic interplay of adequate reading speed, attentional control, working memory, and verbal fluency, accounting for 23% of the explained variance. This study highlights the multifaceted nature of reading proficiency and suggests that a broader perspective is necessary to fully understand reading development and support its improvement.

A Systematic Review on Visual-Processing Deficits in Neurofibromatosis Type 1: What Possible Impact on Learning to Read?

This systematic review aimed to examine the possible implication of visual-perceptual, visuo-attentional and oculomotor processing in the reading deficits frequently experienced by children with Neurofibromatosis type 1 (NF1), as previously shown in dyslexia. Using PRISMA methodological guidelines, we examined 49 studies; most of these reported visual-processing deficits in this population, raising the importance of directly studying the visuo-perceptual and visuo-attentional processes and eye-movement control involved in the learning-to-read process in NF1. The discussion provides a reflection for a better understanding of how visual-processing skills interact with reading deficits in NF1, as well as new avenues for their screening and care.

Visuo-Attentional and Phonological Deficits Explored in French Students with Dyslexia: Eye Movements Recorded during a Phonological Lexical Decision Task

Whether dyslexia is caused by phonological or attentional dysfunction remains a widely debated issue. To enrich this debate, we compared the eye movements of 32 French university students with (14 students) and without (18 students) dyslexia while performing a delayed phonological lexical decision task on 300 visually presented stimuli. The processing stimuli involved either a lexical (i.e., words) or a non-lexical route relying on a grapheme-phoneme correspondence (pseudohomophones and pseudowords), while other stimuli involved only a visual search (consonant and symbol sequences). We recorded the number of fixations, the duration of the first fixation and the amplitude of saccades made on the stimuli. Compared to the controls, the participants with dyslexia made more fixations while reading regardless of the type of stimulus (lexical and non-lexical). Crucially, the participants with dyslexia exhibited longer first fixations in particular while reading phonologically challenging stimuli such as pseudohomophones and pseudowords compared to stimuli involving a simple visual search (consonants, symbols). Taken together, these results suggest that both visual and phonological impairments may be implicated in dyslexia, supporting the hypothesis that dyslexia is a multifactorial deficit.

Cognitive Predictors of the Overlap of Reading and Math in Middle School

Math and reading skills are known to be related, and predictors of each are well researched. What is less understood is the extent to which these predictors, uniquely and collectively, overlap with one another, are differentially important for different academic skills, and account for the overlap of math and reading. We examined 20 potential predictors from four domains (working memory, processing speed, attention, and language) using latent variables and both timed and untimed achievement skill, in a sample (N=212) of at-risk middle schoolers, half of whom were English learners. The predictors accounted for about half of the overlap among achievement skills, suggesting that other factors (e.g., domain specific skills) might also be relevant for the overlap. We also found some differential prediction (language for reading, working memory for math). The present results extend and refine our understanding of the contribution of these cognitive predictors for reading and math.

Attentional modulation of neural sound tracking in children with and without dyslexia

Auditory selective attention forms an important foundation of children's learning by enabling the prioritisation and encoding of relevant stimuli. It may also influence reading development, which relies on metalinguistic skills including the awareness of the sound structure of spoken language. Reports of attentional impairments and speech perception difficulties in noisy environments in dyslexic readers are also suggestive of the putative contribution of auditory attention to reading development. To date, it is unclear whether non-speech selective attention and its underlying neural mechanisms are impaired in children with dyslexia and to which extent these deficits relate to individual reading and speech perception abilities in suboptimal listening conditions. In this EEG study, we assessed non-speech sustained auditory selective attention in 106 7-to-12-year-old children with and without dyslexia. Children attended to one of two tone streams, detecting occasional sequence repeats in the attended stream, and performed a speech-in-speech perception task. Results show that when children directed their attention to one stream, inter-trial-phase-coherence at the attended rate increased in fronto-central sites; this, in turn, was associated with better target detection. Behavioural and neural indices of attention did not systematically differ as a function of dyslexia diagnosis. However, behavioural indices of attention did explain individual differences in reading fluency and speech-in-speech perception abilities: both these skills were impaired in dyslexic readers. Taken together, our results show that children with dyslexia do not show group-level auditory attention deficits but these deficits may represent a risk for developing reading impairments and problems with speech perception in complex acoustic environments. RESEARCH HIGHLIGHTS: Non-speech sustained auditory selective attention modulates EEG phase coherence in children with/without dyslexia Children with dyslexia show difficulties in speech-in-speech perception Attention relates to dyslexic readers' speech-in-speech perception and reading skills Dyslexia diagnosis is not linked to behavioural/EEG indices of auditory attention.

Global visual attention SPAN in different video game genres

Video games, specifically action video games, have been demonstrated to be a useful tool in improving certain visual aspects in the general population. Visual attention span, the ability to simultaneously process multiple distinct visual elements during a single fixation, has been shown to improve among action video game players. The goal of this study was to verify that visual attention span is better not only in action video games, but also in other video game genres such as sports simulators or role-playing games. A total of 41 participants, aged 18 to 40 years old, were asked about the type of video games they were playing, name and genre, and the frequency of play. Visual attention span was assessed in all participants. Participants were divided into 4 groups according to the genre of video game they played. The total percentage of letter identification in the visual attention span was not significantly different between groups. A significant difference was found in the sixth position letter, and the right hemifield performance between groups, especially in sports simulators and action video game participants who showed a better performance. The action video game group showed a significant correlation between visual attention span performance and weekly hours played. Playing regularly different genres other than action video games can contribute to raise visual attention resources.

Dyslexics Exhibit an Orthographic, Not a Phonological Deficit in Lexical Decision

Dyslexia is theorized to be caused by phonological deficits, visuo-attentional deficits, or some combination of the two. The present study contrasted phonological and visuo-attentional theories of dyslexia using a lexical decision task administered to adult participants with and without dyslexia. Homophone and pseudo-homophone stimuli were included to explore whether the two groups differed in their reliance on phonological encoding. Transposed-letter stimuli, including both TL neighbors and TL non-words, measured potential orthographic impairment predicted by visuo-attentional deficit theories. The findings revealed no significant difference in response time or accuracy between the groups for the homophone and pseudo-homophone stimuli. However, dyslexics were significantly slower and less accurate in their responses to the TL stimuli than controls. Thus, dyslexics presented deficits consistent with visuo-attentional theories, but not with the phonological deficit theory.

The effect of online visual games on visual perception, oculomotor, and balance skills of children with developmental dyslexia during the COVID-19 pandemic

PURPOSE

To evaluate the effect of online visual games on the balance, visual perception, and oculomotor skills of children with developmental dyslexia during the COVID-19 pandemic.

METHODS

In this single-blind randomized clinical trial, 50 children with developmental dyslexia, aged 7 to 11 years, were recruited from rehabilitation centers in Tehran, Iran, using a convenience sampling strategy. Participants were randomly divided into two groups: intervention (25) and control (25), with close matching based on sex, age, IQ, and type of disease. The interventions consisted of web-based online computer games focusing on visual perception and oculomotor skills. Outcome measures included the Test of Visual Perception Skills-Revised, the Pediatric Balance Scale, and videonystagmography. The Wechsler Intelligence Scale for Children-IV and the Reading and Dyslexia Test were used to evaluate IQ and reading skills, respectively.

RESULTS

The intervention group exhibited significant post-intervention improvements in the Test of Visual Perception Skills-Revised, tracking gain, saccade latency, and saccade velocity scores (all P < 0.001). In contrast, the control group showed no significant differences in these tests in pre- and post-intervention (all P > 0.05). Notably, post-intervention comparisons between the groups revealed significant differences in smooth pursuit eye movements (P < 0.001), saccade latency (P = 0.027), and saccade velocity (P < 0.001). The Pediatric Balance Scale scores remained unchanged in both groups post-intervention (intervention: P = 0.317; control: P = 0.999). Game face validity was affirmed with impact scores above 1.5 for all items, suggesting that the games were straightforward, clear, and relevant.

CONCLUSION

Online visual games enhanced oculomotor and visual perception skills in children with dyslexia but did not influence balance skills.

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.

Visual attention span deficit in developmental dyslexia: A meta-analysis

BACKGROUND

Visual attention span (VAS) refers to the number of visual elements processed simultaneously in a multielement array. Yet, there are mixed findings regarding VAS deficit in developmental dyslexia (DD) across different tasks, stimuli, languages, control groups, and ages.

AIM

The present meta-analysis aimed to investigate VAS deficit in DD and factors moderating VAS deficit in DD.

METHODS

A meta-analysis based on 32 articles, 54 independent studies, and 4211 subjects was conducted. Effect sizes for each study were calculated and a random-effect model was selected. Task and stimulus types in the VAS task, writing system, orthographic depth, control group type, and age were included as possible moderators.

RESULTS

1) VAS in dyslexic individuals was significantly worse than typically developing individuals; 2) Task-stimulus type (report-verbal/n-back-verbal/n-back-nonverbal), writing system (alphabetic vs. Chinese), and control group type (age matched vs. reading matched) significantly moderated VAS deficit in DD. VAS deficit was more severe in report task with verbal stimuli than in n-back task with verbal and nonverbal stimuli. VAS deficit was more severe in alphabetic language than in Chinese. VAS deficit was more severe when compared with age-matched controls than compared with reading-matched controls.

CONCLUSION

VAS deficit is a possible etiology for DD and moderated by task-stimulus type, writing system, and control group type. These findings have important implications for the understanding of DD.

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.

Characterizing different types of developmental dyslexias in French: The Malabi screener

Reading is a complex process involving multiple stages. An impairment in any of these stages may cause distinct types of reading deficits- distinct types of dyslexia. We describe the Malabi, a screener to identify deficits in various orthographic, lexical, and sublexical components of the reading process in French. The Malabi utilizes stimuli that are sensitive to different forms of dyslexia, including "attentional dyslexia", as it is traditionally refered to, characterized by letter-to-word binding impairments leading to letter migrations between words (e.g., "bar cat" misread as "bat car"), and "letter-position dyslexia", resulting in letter transpositions within words (e.g., "destiny" misread as "density"). After collecting reading error norms from 138 French middle-school students, we analyzed error types of 16 students with developmental dyslexia. We identified three selective cases of attentional dyslexia and one case of letter-position dyslexia. Further tests confirmed our diagnosis and demonstrate, for the first time, how these dyslexias are manifested in French. These results underscore the significance of recognizing and discussing the existence of multiple dyslexias, both in research contexts when selecting participants for dyslexia studies, and in practical settings where educators and practitioners work with students to develop personalized support. The test and supporting materials are available on Open Science Framework (https://osf.io/3pgzb/).

Dyslexia Due to Visual Impairments

Reading involves many different abilities that are necessary or sufficient conditions for fluent and flawless reading. The absence of one necessary or of all sufficient conditions is a cause of dyslexia. The present study investigates whether too short fixation times and an impaired ability to recognize a string of letters simultaneously are causes of dyslexia. The frequency and types of reading mistakes were investigated in a tachistoscopic pseudoword experiment with 100 children with dyslexia to test the impact of too short fixation times and the attempts of children with dyslexia to recognize more letters simultaneously than they can when reading pseudowords. The experiment demonstrates that all types of reading mistakes disappear when the fixation time increases and/or the number of letters that the children try to recognize simultaneously is reduced. The results cannot be interpreted as being due to altered visual crowding, impaired attention, or impaired phonological awareness, but can be regarded as an effect of impaired temporal summation and a dysfunction in the ventral stream of the visual system.

The Role of Visual Factors in Dyslexia

What are the causes of dyslexia? Decades of research reflect a determined search for a single cause where a common assumption is that dyslexia is a consequence of problems with converting phonological information into lexical codes. But reading is a highly complex activity requiring many well-functioning mechanisms, and several different visual problems have been documented in dyslexic readers. We critically review evidence from various sources for the role of visual factors in dyslexia, from magnocellular dysfunction through accounts based on abnormal eye movements and attentional processing, to recent proposals that problems with high-level vision contribute to dyslexia. We believe that the role of visual problems in dyslexia has been underestimated in the literature, to the detriment of the understanding and treatment of the disorder. We propose that rather than focusing on a single core cause, the role of visual factors in dyslexia fits well with risk and resilience models that assume that several variables interact throughout prenatal and postnatal development to either promote or hinder efficient reading.

Visual attention modulates the transition from fine-grained, serial processing to coarser-grained, more parallel processing: A computational modeling study

During reading acquisition, beginning readers transition from serial to more parallel processing. The acquisition of word specific knowledge through orthographic learning is critical for this transition. However, the processes by which orthographic representations are acquired and fine-tuned as learning progresses are not well understood. Our aim was to explore the role of visual attention in this transition through computational modeling. We used the BRAID-Learn model, a Bayesian model of visual word recognition, to simulate the orthographic learning of 700 4-to 10-letter English known words and novel words, presented 5 times each to the model. The visual attention quantity available for letter identification was manipulated in the simulations to assess its influence on the learning process. We measured the overall processing time and number of attentional fixations simulated by the model across exposures and their impact on two markers of serial processing, the lexicality and length effects, depending on visual attention quantity. Results showed that the two lexicality and length effects were modulated by visual attention quantity. The quantity of visual attention available for processing further modulated novel word orthographic learning and the evolution of the length effect on processing time and number of attentional fixations across repeated exposures to novel words. The simulated patterns are consistent with behavioral data and the developmental trajectories reported during reading acquisition. Overall, the model predicts that the efficacy of orthographic learning depends on visual attention quantity and that visual attention may be critical to explain the transition from serial to more parallel processing.

Proportional Reasoning Deficit in Dyslexia

Dyslexia has been linked to an altered perception of metrical structures in language, but no study to date has explored the link between reading impairments and other forms of metrical thinking (e.g., proportional reasoning). In the present study, we assessed proportional reasoning in 16 dyslexic children and 16 age-matched controls from 7 to 10 years of age in order to investigate whether dyslexia might be also linked to an altered form of metrical thinking. We found that dyslexic children are less accurate in performing judgments about proportionality compared to typical peers and that reading accuracy correlates with proportional reasoning abilities for 7-8-year-old children. Overall, these findings suggest that a link exists between reading and proportional reasoning abilities. We might speculate that fostering reasoning based on the meter can facilitate reading because it permits the segmentation of words in syllables and that dyslexia can be identified early with alternative non-reading tasks such as the proportional reasoning task used in this work.

Visual search organization in a cancellation task in developmental dyslexia

There is converging evidence that performance on visual search tasks, often assessed with cancellation tasks, is associated with performance on reading tasks. However, results have been inconsistent across studies dealing with developmental dyslexia. One limitation of previous research is that accuracy, rather than search strategies, was assessed. The present study is the first to investigate visual search strategies during a cancellation task in developmental dyslexia. Here, 24 dyslexic and 33 non-dyslexic children were included. Difficulties in visual search accuracy and organization were highlighted in the dyslexic group compared to the non-dyslexic group. Visual search patterns were also different if dyslexic children had more difficulties in the lexical or the sublexical reading route. While several questions remain to be addressed regarding the influence of other visual attentional processes on the relationship between visual search and reading, this study supports the use of visual search tasks in dyslexia assessment.

The revision process during handwritten text production: The case of French higher education students with dyslexia

The goal of this paper is to observe revision during handwritten text production of French students with and without dyslexia. Subjects with typical language development automate spelling during childhood and adolescence, progressively with experience, this enables them-according to capacity theory applied to written text production (McCutchen, Educational Psychology Review, 8, 1996, 299)-to allocate more cognitive resources to higher-level processes (Bereiter & Scardamalia, The psychology of written composition. Hillsdale: Lawrence Erlbaum, 1987). A lack of automation in spelling could result in poor compositional performance (Fayol & Miret, Psychologie Française, 50, 2005, 391). Moreover, Morken and Helland (Dyslexia, 19, 2013, 131) have shown that young children with dyslexia, engaged in a sentence dictation task, revise their text as much as control children, however their revisions are of lower quality. If students with dyslexia have not totally automated spelling (Mazur-Palandre, Développements (Revue Interdisciplinaire du développement Cognitif Normal et Pathologique), 18, 2016, 177), what is the impact on higher-level processes, such as revision? Our goal is to examine if students with dyslexia and control students proofread their texts in the same way. Results show that they display some similarity but students with dyslexia seem to have a deficit in the error detection mechanism (Horowitz & Breznitz, International Journal of Disability, Development and Education, 58, 2011, 33) and revisions are less efficient. We discuss these results by considering previous studies we conducted on spelling, speech and neuropsychological assessments of our dyslexic participants.

Toward the characterization of a visual form of developmental dyslexia: Reduced visuo-attentional capacity for processing multiple stimuli made of separable features

Some dyslexics cannot process multiple letters simultaneously. It has been argued that this reduced visuo-attentional (VA) letter span could result from poor reading ability and experience. Here, moving away from reading context, we showed that dyslexic group exhibited slower visual search than normal readers group for "symbols", defined as graphic stimuli made up of separable visual features, but not for filled objects. Slowness in symbol visual search was explained by reduced VA field and atypical ocular behaviour when processing those letter-like stimuli and was associated with reduced VA letter span and impaired elementary visuo-spatial perception. Such a basic visual search deficit can hardly be attributed to poor reading ability and experience. Moreover, because it is specific to letter-like stimuli (i.e., "symbols"), it can specifically hinder reading acquisition. Symbol visual search can easily be tested in the pre-reading phase, opening up prospects for early risk detection and prevention of VA dyslexia.

Visual attention span capacity in developmental dyslexia: A meta-analysis

The visual attention span (VAS) deficit theory of developmental dyslexia (DD) indicates that impaired VAS may cause reading disabilities. However, whether people with dyslexia have VAS deficit is still controversial. The current review evaluates the literature regarding the relationship between VAS and poor reading, as it also examines the possible moderators in measuring the VAS capacity of individuals with dyslexia. A total of 25 papers, with participants of 859 readers with dyslexia and 1048 typically developing readers were included in the meta-analysis. The sample sizes, means and standard deviations (SDs) of the scores in VAS tasks were extracted separately from the two groups, which were used to calculate the effect sizes of group differences in SDs and means by the robust variance estimation model. Results showed higher SDs and lower averages of the VAS test scores for readers with dyslexia than those for typically developing readers, revealing high individual variability and remarkable deficits in VAS of DD. Further subgroup analyses showed that the characteristics of VAS tasks, background languages, and participants modulated the group differences in VAS capacities. Particularly, the partial report task with symbols of relatively high visual complexity and key pressing may be the optimal measurement of VAS skills. A greater VAS deficit in DD was observed in more opaque languages, with a trend of developmental increase in attention deficit, especially at the primary school level. Moreover, this VAS deficit seemed to be independent of the phonological deficit of dyslexia. These findings to some extent supported the VAS deficit theory of DD and (partially) explained the controversial relationship between VAS impairment and reading disabilities.

[Formula: see text] Visual selective attention and visual search performance in children with CVI, ADHD, and Dyslexia: a scoping review

Visual selective attention refers to the selection of relevant visual elements in a scene whilst ignoring irrelevant visual elements. Visual Selective Attention Dysfunctions (VSAD) are prevalent in children with Cerebral Visual Impairment (CVI), Attention Deficit Hyperactivity Disorder (ADHD), and Dyslexia. An important issue in the pediatric neuropsychological practice is how to discriminate between the task performance of these populations. We conducted a scoping review of the literature on visual search performance (VSP) in children with CVI, ADHD, and Dyslexia, aged 6-12 years. After a systematic selection process, 35 studies were included. Results suggest that all patient groups have some degree of impaired VSP compared to typically developing children. Children with CVI tend to react slower and less accurately. VSP impairments in children with ADHD are characterized by poor accuracy rather than reaction time. Children with Dyslexia tend to be slower and less accurate, depending on stimulus type. Besides VSAD, it is argued that other neurocognitive mechanisms might influence VSP, such as speed-accuracy trade-off or an executive functioning deficit in ADHD and a phonological deficit in Dyslexia. This paper further discusses the differences and similarities in visual search performance between the groups. The sparse data in children with an official diagnosis of CVI and the technical inconclusive data on children with ADHD and Dyslexia demonstrate complexity of discriminating between these populations in clinical practice based on VSP. New and more quantitative VSP parameters, such as eye tracking-based measures, may contribute to a refined classification among CVI, ADHD, and Dyslexia.

Letter Migrations between Words in Reading Aloud Can Result either from an Impairment in Orthographic Input or in Phonological Output

Letter migrations between words in reading aloud (e.g., reading "cane love" as "lane love" or "lane cove") are known to result from a deficit in the visual-orthographic analysis and characterize attentional dyslexia. In spontaneous speech, individuals with impairment in the phonological output buffer may show migrations of phonemes between words. The purpose of this study was to examine whether migrations between words in reading aloud can also result from a deficit in the phonological output buffer, to explore the characteristics of migrations resulting from orthographic input and from phonological output deficits, and to examine methods to distinguish these two sources. Using tasks of reading aloud of lists of 92-182 word pairs, we identified 18 adults and adolescents with developmental dyslexia who made between-word letter migrations in reading aloud, significantly more than age-matched controls (372 adults, 26 7th-graders and 44 4th-5th-graders). To distinguish between the orthographic input and phonological output sources for these migrations, we administered a test assessing orthographic input without spoken output (written semantic decision on 140 migratable word pairs) and a repetition test of 36 auditorily presented migratable word pairs, assessing spoken output without orthographic input (as well as nonword repetition and 3 span tests). These tests indicated that the migrations in reading aloud of 10 of the participants with dyslexia resulted from an orthographic input deficit-they made migrations not only in reading aloud but also in written word pair comprehension, but not in word pair repetition. For the other 8 participants, the migrations resulted from a phonological output deficit: they made migrations in reading aloud and in word pair repetition, but not in comprehension, and had limited spans and made errors in nonword repetition. We identified several differences between the two types of between-word errors: first, the individuals with attentional dyslexia made omissions of a letter that appeared in the same position in the two words, but the phonological output buffer group did not make such omissions. Second, the groups differed in the origin of migration: orthographic input migrations involve letters that are orthographically adjacent, whereas phonological output migrations involve phonologically adjacent phonemes: phonemes that have just been spoken or that are prepared together in the phonological buffer for production. Migrations from the line below and from 2 lines above the target occurred only in the orthographic input group. This study thus indicates that between-word migrations in reading aloud can result not only from attentional dyslexia, but also from a phonological output buffer deficit, and offers ways to distinguish between the two.

French Students with Dyslexia Facing the Punctuation System: Insecurity, Inventory Use, and Error Studies

Punctuation strongly contributes to the cohesion of the text. Despite this relevant role in written activity, this linguistic paradigm is too rarely observed. Moreover, it is all the more important to analyze its management as it is one of the difficulties declared by students with dyslexia. In that sense, the purpose of this paper is to analyze punctuation management during written text production by students with dyslexia, compared to matched control students. Previous English and Dutch studies confirm this feeling and reveal that students with dyslexia make many punctuation errors. That being said, there is no consensus; other studies do not reach this conclusion. For this present study, students with dyslexia and control students matched in age, university level, and gender were asked to produce spontaneous written and spoken narrative and expository texts. The written texts (N = 86) were collected using Eye and Pen© software with digitizing tablets. Results reveal that if students with dyslexia use the same inventory of punctuation marks as control students, they use fewer punctuation marks and make more errors than control students. These results are discussed and highlighted by the literature dealing with written production as a complex cognitive activity. They reveal that punctuation management is deficient for students with dyslexia, suggesting that the cohesion system can be impacted by dyslexia.

Enhancing reading accuracy through visual search training using symbols

Children with reading disorders present with inaccurate and/or delayed printed word identification. Regarding visual-attentional processing, printed words are letter strings, and each letter is a symbol made of separable features. Simultaneous processing of separable features has been evidenced to be specifically impaired in visual search tasks using symbols in poor readers as well as in a patient with superior parietal lobules (SPL) lesion. Additionally, activation in the SPL has been shown to be abnormally low in dyslexic readers displaying a reduced span of letter strings processing. This deficit has been assumed to impair visual-attentional sampling of printed words. An experiment conducted with 21 dyslexic children tested the hypothesis that a training program based on visual symbol search may stimulate the SPL, leading to a potential benefit transferred to reading performance. We designed the VisioCogLetters serious game and introduced it at random for one month (10 min every day) between four monthly reading sessions. No training was provided between the other (control) reading sessions. Reading accuracy increased without any speed-accuracy trade-off specifically in the session after training. Moreover, the percentage of improvement correlated with the individual time spent at home on training. These results show that improved visual search skills on symbols can translate into enhanced reading performance, and pave a new avenue for future rehabilitation tools.

Dyslexia: Causes and Concomitant Impairments

In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The present paper proposes the absence of at least one necessary condition or the absence of all sufficient conditions as causes for impaired reading. The causes of impaired reading include: an incorrect fixation location, too short a fixation time, the attempt to recognize too many letters simultaneously, too large saccade amplitudes, and too short verbal reaction times. It is assumed that a longer required fixation time in dyslexic readers results from a functional impairment of areas V1, V2, and V3 that require more time to complete temporal summation. These areas and areas that receive input from them, such as the fusiform gyrus, are assumed to be impaired in their ability to simultaneously process a string of letters. When these impairments are compensated by a new reading strategy, reading ability improves immediately.

Neural Correlates of Visual Attention and Short-Term Memory in Children with Reading Difficulty

Visual attention and memory of 20 children with reading difficulty (M_age = 134 months), 24 chronological (M_age = 138 months) and 19 reading-age controls (M_age = 92 months) were examined using object substitution masking; mask offset delay increases visual attention and visual short-term memory demands. ERP amplitude differences in the N1 (alerting), N2pc (N2-posterior-contralateral; selective attention), and SPCN (sustained posterior contralateral negativity; memory load) were expected between groups. Chronological controls performed best, but ERP results were mixed. No group differences were found for N1 or N2pc. SPCN showed enhanced negativity in reading difficulty, indicating greater memory load and anomalous inhibition.

Is learning a logographic script easier than reading an alphabetic script for German children with dyslexia?

PURPOSE

Developmental dyslexia in alphabetic languages (DD) is characterized by a phonological deficit. Since logographic scripts rely predominantly on visual and morphological processing, reading performance in DD can be assumed to be less impaired when reading logographic scripts.

METHODS

40 German-speaking children (18 with DD, 22 not reading-impaired-group C; 9-11 years) received Chinese lessons. Eye movements (EM) were recorded during naming single alphabetic words, pictures (confrontational) and Chinese characters to be named in German and Chinese. The main outcome variables were: Articulation latency, numbers and durations of fixations. Quality of life (QoL) was assessed by questionnaires.

RESULTS

While reading alphabetic words, articulation latencies and numbers of fixations were significantly higher for group DD than for group C (AL-DD = 1.13, AL-C = 0.84, p< .001; FN-DD = 3.50; FN-C = 2.00, p< .001). For naming pictures and Chinese characters in German and in Chinese, no significant group differences were found for any of the EM variables. The percentage of correct answers was high for German naming (DD = 86.67%, C = 95.24%; p = .015) and lower for Chinese naming in both groups, but significantly lower in group DD, especially for Chinese naming (DD = 56.67%, C: 83.77%; p = .003). QoL differed between groups from the children's perspective only at posttest. Parents of group DD perceived their children`s QoL to be lower compared with parents of group C at pre- and posttest.

CONCLUSIONS

Children with dyslexia performed as well as group C during naming Chinese characters in German and in Chinese regarding their EM variables, presumably because they processed Chinese characters by the visuo-spatial pathway with direct access to the semantic system. However, the significantly lower percentage of correct answers especially during Chinese naming showed that group DD had more difficulties naming Chinese characters than group C, which could be attributed to their phonological deficit, among other factors.

TRIAL REGISTRATION

German clinical trials register (DRKS00015697).

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.

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.

Visual attention span as a predictor of reading fluency and reading comprehension in Arabic

Introduction

Visual attention span is a measure of multielement parallel processing. Individuals with higher visual attention span are expected to allocate more attention to letters within strings, which boosts letter identification and translates into more efficient reading. Given the high visual complexity of the Arabic writing system, we expected visual attention span to be an important predictor of reading in the Arabic language.

Methods

Native Arabic readers from Grade 4 and Grade 5 were recruited in Iraqi schools. We assessed the contribution of visual attention span to their reading fluency performance in tasks of fully vowelized word and pseudo-word reading, non-vowelized text reading, and written text comprehension. Their phonological awareness, IQ, and single letter processing speed were further evaluated.

Results

Results showed that visual attention span was a significant unique predictor of all the reading measures. Visual attention span and phonological awareness accounted for a similar amount of variance in word and pseudo-word reading fluency. Visual attention span was a far higher predictor than phonological awareness for text reading fluency and the sole predictor of text comprehension.

Discussion

The role of visual attention span to reading is discussed by reference to current word recognition models. Higher involvement of visual attention is expected in vowelized script to compensate for increased crowding in the presence of diacritics. Visual attention would thus contribute to sub-lexical orthographic parsing and favor orthography-to-phonology mapping, in particular for the pseudo-words that do not benefit from efficient lexical feedback. In non-vowelized script, higher visual attention would enhance the accurate and fast identification of root letters within words, thus resulting in faster word recognition.

Auditory brainstem response deficits in learning disorders and developmental language disorder: a systematic review and meta-analysis

Although learning disorders (LD) and developmental language disorder (DLD) can be linked to overlapping psychological and behavioral deficits, such as phonological, morphological, orthographic, semantic, and syntactic deficits, as well as academic (e.g., reading) difficulties, they are currently separate diagnoses in the DSM-5 with explicit phenotypic differences. At a neural level, it is yet to be determined to what extent they have overlapping or distinct signatures. The identification of such neural markers/endophenotypes could be important for the development of physiological diagnostic tools, as well as an understanding of disorders across different dimensions, as recommended by the Research Domain Criteria Initiative (RDoC). The current systematic review and meta-analysis examined whether the two disorders can be differentiated based on the auditory brainstem response (ABR). Even though both diagnoses require hearing problems to be ruled out, a number of articles have demonstrated associations of these disorders with the auditory brainstem response. We demonstrated that both LD and DLD are associated with longer latencies in ABR Waves III, V, and A, as well as reduced amplitude in Waves V and A. However, multilevel subgroup analyses revealed that LD and DLD do not significantly differ for any of these ABR waves. Results suggest that less efficient early auditory processing is a shared mechanism underlying both LD and DLD.

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.

The visual-attention span deficit in developmental dyslexia: Review of evidence for a visual-attention-based deficit

The visual attention span (VAS) deficit hypothesis in developmental dyslexia posits that a subset of dyslexic individuals shows a multielement parallel processing deficit due to reduced visual attention capacity. However, the attention-based interpretation of poor performance on VAS tasks is hotly debated. The purpose of the present paper is to clarify this issue through a critical review of relevant behavioural and neurobiological findings. We first examine the plausibility of alternative verbal interpretations of VAS performance, evaluating whether performance on VAS tasks might reflect verbal short-term memory, verbal coding or visual-to-verbal mapping skills. We then focus on the visual dimensions of VAS tasks to question whether VAS primarily reflects visuo-attentional rather than more basic visual skills. Scrutiny of the available behavioural and neurobiological findings not only points to a deficit of visual attention in dyslexic individuals with impaired VAS but further suggests a selective endogenous attentional system deficit that relates to atypical functioning of the brain dorsal attentional network. The overview clarifies the debate on what is being measured through VAS tasks and provides insights on how to interpret the VAS deficit in developmental dyslexia.

Use of Virtual Reality in Children with Dyslexia

In recent years, the study of dyslexia has seen rapid progress in definition and classification, neuropsychological correlates, neurobiological factors, and intervention. However, there are few studies on how virtual reality can affect improving cognitive domains and cross-cutting pedagogical skills. We, therefore, tested intervention through the use of a virtual reality rehabilitation system (VRRS) in children with dyslexia. Twenty-eight patients diagnosed with dyslexia were enrolled in this study. One-half underwent conventional neuropsychological treatment, and the other half performed VR neurorehabilitation training using the VRRS. All patients were evaluated by neuropsychological assessment at baseline (T0) and at the end of the protocol (T1). The assessment included the administration of the Wechsler Intelligence Scale for Children-IV and the Italian Battery for the Assessment of Dyslexia and Dysorthography. Our results showed a significant difference in word-reading test scores as well as in homophonic writing. In addition, treatment type was found to affect some domains of the WISC. We believe that the VRRS led to improved outcomes through the use of VR, which encourages active exploration, improves engagement, and provides motivation and enjoyment, allowing longer training sessions and improving treatment adherence.

Visual and social differences in dyslexia: deep phenotyping of four cases with spared phonology

Diagnostic criteria for dyslexia describe specific reading difficulties, and single-deficit models, including the phonological deficit theory, have prevailed. Children seeking diagnosis, however, do not always show phonological deficits, and may present with strengths and challenges beyond reading. Through extensive neurological, neuropsychological, and academic evaluation, we describe four children with visuospatial, socio-emotional, and attention impairments and spared phonology, alongside long-standing reading difficulties. Diffusion tensor imaging revealed white matter alterations in inferior longitudinal, uncinate, and superior longitudinal fasciculi versus neurotypical children. Findings emphasize that difficulties may extend beyond reading in dyslexia and underscore the value of deep phenotyping in learning disabilities.

Effects of a short and intensive transcranial direct current stimulation treatment in children and adolescents with developmental dyslexia: A crossover clinical trial

Developmental Dyslexia (DD) significantly interferes with children’s academic, personal, social, and emotional functioning. Nevertheless, therapeutic options need to be further validated and tested in randomized controlled clinical trials. The use of transcranial direct current stimulation (tDCS) has been gaining ground in recent years as a new intervention option for DD. However, there are still open questions regarding the most suitable tDCS protocol for young people with DD. The current crossover study tested the effectiveness of a short and intensive tDCS protocol, including the long-term effects, as well as the influence of age and neuropsychological processes at baseline on reading improvements. Twenty-four children and adolescents with DD were randomly assigned to receive active tDCS during the first slot and sham tDCS during the second slot or vice versa. Five consecutive daily sessions of left anodal/right cathodal tDCS set at 1 mA for 20 min were administered over the parieto-occipital regions. Reading measures (text, high frequency word, low frequency word, and non-word lists) and neuropsychological measures (visual-spatial and verbal working memory, phoneme blending, and rapid automatized naming tasks) were collected before, immediately after, 1 week and 1 month later the treatment. Our results showed that only the active tDCS condition improved non-word reading speed immediately after and 1 month later the end of the treatment compared with baseline. In addition, the improvement in non-word reading speed was significantly correlated with age and with neuropsychological measures (verbal working memory and phoneme blending) at baseline but only in the active tDCS condition. The current crossover study contributed to enforce previous effects of tDCS, including long-term effects, on non-word reading speed and to understand the effect of age and neuropsychological processes on reading outcomes. Our findings showed that tDCS could be a low-cost and easy-to-implement treatment option with long-term effects for children and adolescents with DD.

A stitch in time…: Comparing late-identified, late-emerging and early-identified dyslexia

When dyslexia is diagnosed late, the question is whether this is due to late-emerging (LE) or late-identified (LI) problems. In a random selection of dyslexia-diagnosis case files we distinguished early-diagnosed (Grade 1-3, n = 116) and late-diagnosed (Grade 4-6) dyslexia. The late-diagnosed files were divided into LE (n = 54) and LI dyslexia (n = 45). The LE group consisted of children whose national-curriculum literacy outcomes did not warrant referral for dyslexia diagnosis in Grades 1-2; the LI group of children whose literacy outcomes did, but who were referred for diagnostic assessment after Grade 3. At the time of diagnosis, the percentage of poor performers on word-level literacy measures generally did not differ between the groups. Only the LE group contained fewer poor performers than the early-diagnosed and LI group on some word-reading measures. All groups showed similar distributions of phonological difficulties. There were no indications of compensation through vocabulary, memory or IQ in either late-diagnosed group. Our diagnosis-based study confirms and extends previous research-based studies on LE dyslexia. Moreover, it shows that LI dyslexia exists, which can be regarded as the existence of instructional casualties. The findings speak to issues of identification, diagnosis and compensation and call for further efforts to improve the early identification of dyslexia.