<h4>Background</h4>Dyslexia is one of the most common neurodevelopmental disorders. There have been many definitions over the past century, and debate continues as to how dyslexia should be defined. This debate contributes to confusion and misinformation. We move beyond the debate by establishing areas of consensus among a wide range of experts.<h4>Methods</h4>We conducted a Delphi study with a panel of dyslexia experts, including academics, specialist teachers, educational psychologists, and individuals with dyslexia, asking them for their views on a set of key statements about dyslexia. We carried out two survey rounds, in each case accepting statements with greater than 80% consensus and reviewing and revising other statements using feedback from the expert panel. This was followed by discussion with a subset of the panel around a few statements with marginal consensus.<h4>Results</h4>Forty-two statements were ultimately accepted. In the current paper we review those statements that pertain to a definition of dyslexia, demonstrate how they align with the research literature, and build on previous definitions of dyslexia.<h4>Conclusions</h4>There was considerable consensus in our expert panel that dyslexia is a difficulty in reading and spelling, associated with multiple factors, and that it frequently co-occurs with other developmental disorders. It was agreed that difficulties in reading fluency and spelling are key markers of dyslexia across different ages and languages. We conclude with a proposed new definition of dyslexia.

In this literature review, we address the use of cognitive tests, including intelligence tests, in the assessment and diagnosis of dyslexia, from both historic and present-day perspectives. We discuss the role of cognitive tests in the operationalization of the concepts of specificity and unexpectedness, two constructs considered essential to the characterization of dyslexia since the publication of early case reports in the late nineteenth century. We review the advantages and disadvantages of several approaches to specific learning disabilities' identification that are used in schools. We also discuss contemporary debates around the use of standardized cognitive testing in dyslexia evaluations, in particular, the arguments of those who favor an approach to diagnosis based on prior history and the results of a comprehensive evaluation and those who favor an approach based on an individual's response to intervention. We attempt to explain both perspectives by examining clinical observations and research findings. We then provide an argument for how cognitive tests can contribute to an accurate and informed diagnosis of dyslexia.

The International Dyslexia Association’s current definition of dyslexia was approved by its Board of Directors on November 12, 2002. After two decades of scientific inquiry into the nature of dyslexia, it is time to reconsider and potentially revise the definition in light of what has been learned. We propose a definition of dyslexia based on its essential nature. Dyslexia is a specific learning disability in reading at the word level. It involves difficulty with accurate and/or fluent word recognition and/or pseudoword reading. We also suggest that the definition should focus solely on dyslexia’s core features and should not include risk factors, potential secondary consequences, or other characteristics. Until those factors can reliably differentiate between those with and without dyslexia at an individual level, they should not be included in the definition.

Objective: Developmental dyslexia is a specific learning disability related to reading that often leads to lifelong challenges. Accurate prevalence estimates are essential for the timely diagnosis, intervention, and formulation of appropriate educational policies. This systematic review and meta-analysis aimed to provide a reliable estimate of the prevalence of developmental dyslexia in primary school students in Iran. Method: We conducted a comprehensive search of international databases, including PubMed, Web of Science, and Scopus, alongside national databases such as SID and Magiran, using relevant search terms from 1991 to April 2024. Two researchers independently assessed the articles for the risk of bias using the Hoy checklist and extracted the data. Subgroup meta-analysis examined variations in prevalence across different subgroups. Results: A total of 18 studies, comprising 28,952 participants, were included. The overall prevalence of developmental dyslexia was 5.7% (95% CI: 4.5%-6.9%), with a higher prevalence observed in boys (7.5%, 95% CI: 5.8%-9.2%) compared to girls (4%, 95% CI: 3%-5%). Subgroup analysis revealed a statistically significant impact of diagnostic material on prevalence estimates, with informal reading tests reporting a prevalence of 3.4% (95% CI: 2.4%-4.4%) and the screening inventory reading test showing 8.8% (95% CI: 4.5%-13.2%) (P = 0.002). Prevalence also varied by sample size, with smaller studies ( 2000 participants) at 3.9% (95% CI: 2.3%-5

Dyslexia, or specific reading disability, is the most common learning disorder with a complex, partially genetic basis, but its biochemical mechanisms remain poorly understood. A locus on Chromosome 3, DYX5, has been linked to dyslexia in one large family and speech-sound disorder in a subset of small families. We found that the axon guidance receptor gene ROBO1, orthologous to the Drosophila roundabout gene, is disrupted by a chromosome translocation in a dyslexic individual. In a large pedigree with 21 dyslexic individuals genetically linked to a specific haplotype of ROBO1 (not found in any other chromosomes in our samples), the expression of ROBO1 from this haplotype was absent or attenuated in affected individuals. Sequencing of ROBO1 in apes revealed multiple coding differences, and the selection pressure was significantly different between the human, chimpanzee, and gorilla branch as compared to orangutan. We also identified novel exons and splice variants of ROBO1 that may explain the apparent phenotypic differences between human and mouse in heterozygous loss of ROBO1. We conclude that dyslexia may be caused by partial haplo-insufficiency for ROBO1 in rare families. Thus, our data suggest that a slight disturbance in neuronal axon crossing across the midline between brain hemispheres, dendrite guidance, or another function of ROBO1 may manifest as a specific reading disability in humans.

We believe that the currently expanding understanding of the neurophysiology of dyslexia will lead eventually to improved diagnosis and remediation of this learning disability. The detailed mapping of brain electrical activity shows promise of providing the neuropsychologist and learning disability specialist with another "perspective" on reading disability. This technique may prove valuable in the diagnosis of dyslexia at an early age and in the tailoring of the learning experience to a child's specific deficits and capabilities. Published in Research publications - Association for Research in Nervous and Mental Disease (1988)

Dramatic favorable responses of children with learning disabilities or dyslexia and attention deficit disorder to antimotion sickness medications: four case reports. Responses of four learning disabled children who showed dramatic improvements to one or more antimotion-sickness-antihistamines and -stimulants are described qualitatively. These cases were selected from a prior quantitative study in which three antihistamines (meclizine, cyclizine, dimenhydrinate) and three stimulants (pemoline, methylphenidate, dextroamphetamine) were tested in variable combinations (using a specific clinical method) for favorable responses by 100 children characterized by diagnostic evidence of learning disabilities and cerebellar-vestibular dysfunctioning. Pending validation in double-blind controlled studies, these qualitative results suggest that the "cerebellar-vestibular (CV) stabilizing" antimotion-sickness medications, Piracetam included, and their combinations may be shown to be therapeutically useful in treating children with learning disabilities or dyslexia and attention deficit disorder. Published in Perceptual and motor skills (1991)

United Kingdom, the term learning disability generally refers to an intellectual disability, while conditions such as dyslexia and dyspraxia are usually Learning disability, or learning disorder, is a condition in the brain that causes difficulties comprehending or processing information and can be caused by several different factors. Given the "difficulty learning in a typical manner", this does not exclude the ability to learn in a different manner. Therefore, some people can be more accurately described as having a "learning difference", thus Learning disability, or learning disorder, is a condition in the brain that causes difficulties comprehending or processing information and can be caused by several different factors. Given the "difficulty learning in a typical manner", this does not exclude the ability to learn in a different manner. Therefore, some people can be more accurately described as having a "learning difference", thus avoiding any misconception of being disabled with a possible lack of an ability to learn and possible negative stereotyping. In the United Kingdom, the term learning disability generally refers to an intellectual disability, while conditions such as dyslexia and dyspraxia are usually referred to as learning difficulties. While learning disability and learning disorder are often used interchangeably, they differ in many ways. Disorder refers to significant learning problems in an academic area. These problems, however, are not enough to warrant an official diagnosis. Learning disability, on the other hand, is an official clinical diagnosis,… With impairment in reading (DSM-5-TR: F81.0, ICD-11: 6A03.0) Learning difficulties are manifested in impairments in reading skills such as word reading accuracy, reading fluency or reading comprehension. Previously termed 'reading disorder', this is the most common learning disability. Of all students with specific learning disabilities, 70–80% have deficits in reading. The term developmental dyslexia is often used as a synonym for reading disability; however, many researchers assert that there are different types of reading disabilities, of which dyslexia is one. A reading disability can affect any part of the reading process, including difficulty with accurate or fluent word recognition, or both, word decoding, reading rate, prosody (oral reading with expression), and reading comprehension. Before the term dyslexia came to prominence, this learning disability used to be known as word blindness. Common indicators of reading disability include difficulty with phonemic awareness—the ability to break up words into their component sounds, and difficulty with matching letter combinations to specific sounds (sound-symbol correspondence).

Developmental reading disability is a prevalent and often enduring problem with varied mechanisms that contribute to its phenotypic heterogeneity. This mechanistic and phenotypic variation, as well as relatively modest sample sizes, may have limited the development of accurate neuroimaging-based classifiers for reading disability, including because of the large feature space of neuroimaging datasets. An unsupervised learning model was used to reduce deformation-based data to a lower-dimensional manifold and then supervised learning models were used to classify these latent representations in a dataset of 96 reading disability cases and 96 controls (mean age: 9.86 ± 1.56 years). A combined unsupervised autoencoder and supervised convolutional neural network approach provided an effective classification of cases and controls (accuracy: 77%; precision: 0.75; recall: 0.78). Brain regions that contributed to this classification accuracy were identified by adding noise to the voxel-level image data, which showed that reading disability classification accuracy was most influenced by the superior temporal sulcus, dorsal cingulate, and lateral occipital cortex. Regions that were most important for the accurate classification of controls included the supramarginal gyrus, orbitofrontal, and medial occipital cortex. The contribution of these regions reflected individual differences in reading-related abilities, such as non-word decoding or verbal comprehension. Together, the results demo

The neurobiology and neuropsychology of adult learning disorders. The area of adult learning disabilities is reviewed from a neurobiological and neuropsychological perspective. The seminal contributions of Galaburda's neuroanatomic studies, Duffy's neurophysiologic findings, and recent magnetic resonance imaging studies have illustrated various possible pathophysiologic bases in dyslexia and are reviewed along with other neurobehavioral disorders that may coexist with learning disorders. Neuropsychological assessment methods in evaluating learning disabilities are reviewed and test results in a case of traumatically induced dyslexia are compared to those obtained in three adults with residual developmental dyslexia. The problems associated with treatment of adult learning disorders are discussed in the context of brain plasticity and recovery of function from the perspective of a brain-injury model. Lastly, the basis common to neurologic factors subserving learning disability and emotional dysfunction is explored. Published in Journal of learning disabilities (1992)

Neuropsychological classification and treatment of dyslexia. Evidence shows that initial and advanced learning to read are predominantly mediated by the right and left cerebral hemispheres, respectively. Premature reliance on left-hemispheric reading strategies may result in L-type dyslexia, characterized by hurried and inaccurate reading. P-type dyslexia, characterized by a slow and fragmented style of reading, may result from the inability to shift from the predominant generation of right-hemispheric reading strategies to the predominant generation of left-hemispheric reading strategies. Results of investigations concerning the validity of the L/P-typology are discussed, as are the reading effects of hemisphere-specific and hemisphere-alluding stimulation in children with L- and P-type dyslexia. Published in Journal of learning disabilities (1992)

which include visual and auditory perception. Dyslexia is a common language-based learning disability. Dyslexia can affect reading fluency, decoding, reading Language-based learning disabilities or LBLD are "heterogeneous" neurological differences that can affect skills such as listening, reasoning, speaking, reading, writing, and math calculations. It is also associated with movement, coordination, and direct attention. LBLD is not usually identified until the child reaches school age. Most people with this disability find it hard to communicate, to e La…

definition reads as follows: “Dyslexia is a specific learning disability that is neurobiological in origin … students identified with a specific learning disability (SLD). Dyslexia is currently included in the … follows: “Reading Disability is a reading and language-based learning disability, also commonly called dyslexia

there is a preference for the terms ‘Specific Learning Difficulty’ (SpLD) and Learning Disability (LD) … not directly recog- nize learning disability, dyslexia or specific learning difficulties except by inference … countries is called a learning disability (LD) in Canada. A learning disability means that the individual

Dyslexia refers to difficulties in acquiring fluent reading in the absence of an intellectual deficit. In the current study, we addressed two controversial issues surrounding this disorder. Firstly, the hypothesis of an implicit learning impairment that could contribute to the development of dyslexia, and secondly, the need to distinguish reading difficulties according to IQ, the so-called discrepancy definition between reading ability and expected ability. Of relevance, it has been suggested that implicit learning is relatively independent of IQ in comparison to explicit/strategic learning. Consequently, we compared implicit sequence learning in children (8-9 years old) with dyslexia, poor readers associated with low intellectual functioning (LIF), and typically developing children (TD). Both the Dyslexia and LIF groups learned less than the TD group. Therefore, the Dyslexia group's performance supports the hypothesis of an implicit learning deficit in this population. However, the poor learning shown by the LIF group challenges the necessity of a discrepancy definition for dyslexia (poor reading despite average IQ). This paper argues that implicit learning may influence the severity of reading difficulties rather than act as a causal factor and highlights the need for further research on the usefulness of distinguishing reading difficulties based on LIF.