Dyslexia as a Neurodevelopmental Disorder and What Makes It Different from a Chess Disorder

Genetic neurodevelopmental clustering and dyslexia

Dyslexia is a learning difficulty with neurodevelopmental origins, manifesting as reduced accuracy and speed in reading and spelling. It is substantially heritable and frequently co-occurs with other neurodevelopmental conditions, particularly attention deficit-hyperactivity disorder (ADHD). Here, we investigate the genetic structure underlying dyslexia and a range of psychiatric traits using results from genome-wide association studies of dyslexia, ADHD, autism, anorexia nervosa, anxiety, bipolar disorder, major depressive disorder, obsessive compulsive disorder, schizophrenia, and Tourette syndrome. Genomic Structural Equation Modelling (GenomicSEM) showed heightened support for a model consisting of five correlated latent genomic factors described as: F1) compulsive disorders (including obsessive-compulsive disorder, anorexia nervosa, Tourette syndrome), F2) psychotic disorders (including bipolar disorder, schizophrenia), F3) internalising disorders (including anxiety disorder, major depressive disorder), F4) neurodevelopmental traits (including autism, ADHD), and F5) attention and learning difficulties (including ADHD, dyslexia). ADHD loaded more strongly on the attention and learning difficulties latent factor (F5) than on the neurodevelopmental traits latent factor (F4). The attention and learning difficulties latent factor (F5) was positively correlated with internalising disorders (.40), neurodevelopmental traits (.25) and psychotic disorders (.17) latent factors, and negatively correlated with the compulsive disorders (-.16) latent factor. These factor correlations are mirrored in genetic correlations observed between the attention and learning difficulties latent factor and other cognitive, psychological and wellbeing traits. We further investigated genetic variants underlying both dyslexia and ADHD, which implicated 49 loci (40 not previously found in GWAS of the individual traits) mapping to 174 genes (121 not found in GWAS of individual traits) as potential pleiotropic variants. Our study confirms the increased genetic relation between dyslexia and ADHD versus other psychiatric traits and uncovers novel pleiotropic variants affecting both traits. In future, analyses including additional co-occurring traits such as dyscalculia and dyspraxia will allow a clearer definition of the attention and learning difficulties latent factor, yielding further insights into factor structure and pleiotropic effects.

Developmental dyslexia in children with perinatal exposure to hypoxia: A systematic review

BACKGROUND

Research on a health-related event at the stage of labour and the occurrence of adverse outcomes at the school age has provided inconclusive results. Thus far, no systematic reviews have been conducted. Thus, the objective of this study is to investigate the association between hypoxia during pregnancy or delivery and the subsequent occurrence of a developmental dyslexia in school-age children.

METHODS

We used a standard search strategy of electronic databases (PubMed, PsycINFO, Web of Science, EMBASE, and Cochrane Library) and handsearching. We included observational studies (cohort studies, case-control studies) that consider as an exposure the presence of hypoxia during pregnancy or delivery, and as an outcome, developmental dyslexia in school-age children. Two reviewers independently conducted the search and determined eligibility, which was not restricted by language or year of publication.

RESULTS

The search took place until 1 April 2023. Of the 1,336 abstracts screened, 6 were assessed for eligibility. Of the six eligible studies, no studies met the pre-specified eligibly criteria.

CONCLUSIONS

We were unable to assess the association between hypoxia and developmental dyslexia, as no eligible studies were found. Thus, the association between hypoxia during pregnancy or delivery and dyslexia in school-age children remains unknown.

The Role of Neural and Genetic Processes in Learning to Read and Specific Reading Disabilities: Implications for Instruction

To learn to read, the brain must repurpose neural systems for oral language and visual processing to mediate written language. We begin with a description of computational models for how alphabetic written language is processed. Next, we explain the roles of a dorsal sublexical system in the brain that relates print and speech, a ventral lexical system that develops the visual expertise for rapid orthographic processing at the word level, and the role of cognitive control networks that regulate attentional processes as children read. We then use studies of children, adult illiterates learning to read, and studies of poor readers involved in intervention, to demonstrate the plasticity of these neural networks in development and in relation to instruction. We provide a brief overview of the rapid increase in the field's understanding and technology for assessing genetic influence on reading. Family studies of twins have shown that reading skills are heritable, and molecular genetic studies have identified numerous regions of the genome that may harbor candidate genes for the heritability of reading. In selected families, reading impairment has been associated with major genetic effects, despite individual gene contributions across the broader population that appear to be small. Neural and genetic studies do not prescribe how children should be taught to read, but these studies have underscored the critical role of early intervention and ongoing support. These studies also have highlighted how structured instruction that facilitates access to the sublexical components of words is a critical part of training the brain to read.

Efficacy of a Robot-Assisted Intervention in Improving Learning Performance of Elementary School Children with Specific Learning Disorders

(1) Background: There has been significant recent interest in the potential role of social robots (SRs) in special education. Specific Learning Disorders (SpLDs) have a high prevalence in the student population, and early intervention with personalized special educational programs is crucial for optimal academic achievement. (2) Methods: We designed an intense special education intervention for children in the third and fourth years of elementary school with a diagnosis of a SpLD. Following confirmation of eligibility and informed consent, the participants were prospectively and randomly allocated to two groups: (a) the SR group, for which the intervention was delivered by the humanoid robot NAO with the assistance of a special education teacher and (b) the control group, for which the intervention was delivered by the special educator. All participants underwent pre- and post-intervention evaluation for outcome measures. (3) Results: 40 children (NAO = 19, control = 21, similar baseline characteristics) were included. Pre- and post-intervention evaluation showed comparable improvements in both groups in cognition skills (decoding, phonological awareness and reading comprehension), while between-group changes favored the NAO group only for some phonological awareness exercises. In total, no significant changes were found in any of the groups regarding the emotional/behavioral secondary outcomes. (4) Conclusion: NAO was efficient as a tutor for a human-supported intervention when compared to the gold-standard intervention for elementary school students with SpLDs.

Silent versus Reading Out Loud modes: An eye-tracking study

The main purpose of this study is to compare the silent and loud reading ability of typical and dyslexic readers, using eye-tracking technology to monitor the reading process. The participants (156 students of normal intelligence) were first divided into three groups based on their school grade, and each subgroup was then further separated into typical readers and students diagnosed with dyslexia. The students read the same text twice, one time silently and one time out loud. Various eye-tracking parameters were calculated for both types of reading. In general, the performance of the typical students was better for both modes of reading - regardless of age. In the older age groups, typical readers performed better at silent reading. The dyslexic readers in all age groups performed better at reading out loud. However, this was less prominent in secondary and upper secondary dyslexics, reflecting a slow shift towards silent reading mode as they age. Our results confirm that the eye-tracking parameters of dyslexics improve with age in both silent and loud reading, and their reading preference shifts slowly towards silent reading. Typical readers, before 4th grade do not show a clear reading mode preference, however, after that age they develop a clear preference for silent reading.

Distribution of Visual and Oculomotor Alterations in a Clinical Population of Children with and without Neurodevelopmental Disorders

A prospective, non-randomized comparative study was conducted to compare the distribution of oculomotor and visual alterations in children with neurodevelopmental disorders and healthy children without such disorders. Sixty-nine children (aged 6-13 years) were enrolled and divided into three groups: a control group (CG) of 23 healthy children; a group of 18 healthy children with oculomotor abnormalities (OAG); and a group of 28 children with a neurodevelopmental disorder (NDDG), with 15 cases of dyslexia, 7 cases of developmental coordination disorder (DCD) and 6 cases of attention deficit/hyperactivity disorder (ADHD). Significantly worse near stereopsis was found in NDDG compared with CG (p < 0.001) and OAG (p = 0.001). Likewise, a significantly lower amplitude of accommodation was found in NDDG compared with CG in both the right (p = 0.001) and left eyes (p < 0.001). No statistically significant differences between groups were found in the measurement of near and distance phoria (p ≥ 0.557), near point of convergence (p = 0.700) and fusional vergences (p ≥ 0.059). Significantly impaired oculomotor test scores were found in NDDG compared with CG (p < 0.001), with no significant differences between OAG and NDDG (p ≥ 0.063). The comparison between the three types of neurodevelopmental disorders included revealed the presence of a significantly lower amplitude of accommodation in children with DCD compared with dyslexics. Furthermore, less exophoria at near was present in children with dyslexia compared with children with ADHD (p = 0.018) and DCD (p = 0.054). In conclusion, children with dyslexia, ADHD and DCD show an altered oculomotor pattern and a more reduced amplitude of accommodation, not always compatible with the diagnostic criteria of an accommodative insufficiency. Accommodative and binocular vision problems are not always present in these children and cannot be considered an etiologic factor.

Putting the Identification of Dyslexia into a Multi-Level Perspective

There is continuing debate concerning the definition and diagnosis of dyslexia [...].

(Swiss) GraphoLearn: an app-based tool to support beginning readers

We assessed the Swiss-German version of GraphoLearn, a computer game designed to support reading by training grapheme-phoneme correspondences. A group of 34 children at risk for dyslexia trained three times a week during 14 weeks, on top of their standard school instruction. The sample was divided into two groups of 18 and 16 children, who started training at either the middle or the end of first grade. We found beneficial training effects in pseudoword reading in both training groups and for rapid automatized naming skills in the group that trained earlier. Our results suggest that both the efficiency in phonological decoding and rapid access to verbal representations are susceptible to facilitation by GraphoLearn. These findings confirm the utility of the training software as a tool to support school instruction and reading-related abilities in beginning readers. We discuss ideas to improve the content and outcomes of future versions of the training software.

Reply to “Dyslexia: Still Not a Neurodevelopmental Disorder”

In a recent opinion article, we explained why we think that defining developmental dyslexia as a neurodevelopmental disorder and neuroimaging studies on dyslexia are useful. A recent response has made some claims of generalized misinterpretation and misconception in the field. Since that was a direct reply to our article, we would like to clarify our opinion on some of those claims.

Dyslexia: Still Not a Neurodevelopmental Disorder

We recently pointed out that there is no evidence to support the commonly held view that there is something wrong with the brains of children who have great difficulty learning to read. In response, it was argued that dyslexia should be considered to be a neurodevelopmental disorder because of its potential to adversely affect quality of life, and because there are differences between the brains of people with different levels of reading skill. We agree with these two points, but they are irrelevant to the issue in question, because neither establishes the critical notion of disrupted neurodevelopment; that is, a brain fault. Differences between groups do not imply that any individuals are abnormal, and calling a brain improperly developed on the basis of cultural issues has absurd implications. Even calling brains atypical is unfounded because reference to typicality hinges on knowledge of the relevant distributions, which is currently lacking. Moreover, there is at present no obvious role for neurology- or neuroscience-based input for the critical issue of the assessment and remediation of the reading difficulties themselves. We reiterate our conclusion that there is, at the moment, no credible foundation to support the claim that dyslexia is a neurodevelopmental disorder.