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Annual Review of Clinical Psychology 2015This review uses a levels-of-analysis framework to summarize the current understanding of developmental dyslexia's etiology, brain bases, neuropsychology, and social... (Review)
Review
This review uses a levels-of-analysis framework to summarize the current understanding of developmental dyslexia's etiology, brain bases, neuropsychology, and social context. Dyslexia is caused by multiple genetic and environmental risk factors as well as their interplay. Several candidate genes have been identified in the past decade. At the brain level, dyslexia is associated with aberrant structure and function, particularly in left hemisphere reading/language networks. The neurocognitive influences on dyslexia are also multifactorial and involve phonological processing deficits as well as weaknesses in other oral language skills and processing speed. We address contextual issues such as how dyslexia manifests across languages and social classes as well as what treatments are best supported. Throughout the review, we highlight exciting new research that cuts across levels of analysis. Such work promises eventually to provide a comprehensive explanation of the disorder as well as its prevention and remediation.
Topics: Brain; Child; Dyslexia; Humans; Molecular Biology; Risk Factors
PubMed: 25594880
DOI: 10.1146/annurev-clinpsy-032814-112842 -
Current Opinion in Pediatrics Dec 2016We review current knowledge about the nature of reading development and disorders, distinguishing between the processes involved in learning to decode print, and the... (Review)
Review
PURPOSE OF REVIEW
We review current knowledge about the nature of reading development and disorders, distinguishing between the processes involved in learning to decode print, and the processes involved in reading comprehension.
RECENT FINDINGS
Children with decoding difficulties/dyslexia experience deficits in phoneme awareness, letter-sound knowledge and rapid automatized naming in the preschool years and beyond. These phonological/language difficulties appear to be proximal causes of the problems in learning to decode print in dyslexia. We review data from a prospective study of children at high risk of dyslexia to show that being at family risk of dyslexia is a primary risk factor for poor reading and children with persistent language difficulties at school entry are more likely to develop reading problems. Early oral language difficulties are strong predictors of later difficulties in reading comprehension.
SUMMARY
There are two distinct forms of reading disorder in children: dyslexia (a difficulty in learning to translate print into speech) and reading comprehension impairment. Both forms of reading problem appear to be predominantly caused by deficits in underlying oral language skills. Implications for screening and for the delivery of robust interventions for language and reading are discussed.
Topics: Child; Child Language; Child, Preschool; Comprehension; Dyslexia; Humans; Reading; Risk Factors
PubMed: 27496059
DOI: 10.1097/MOP.0000000000000411 -
Language, Speech, and Hearing Services... Oct 2018This review summarizes what is known about the structural and functional brain bases of dyslexia. (Review)
Review
PURPOSE
This review summarizes what is known about the structural and functional brain bases of dyslexia.
METHOD
We review the current literature on structural and functional brain differences in dyslexia. This includes evidence about differences in gray matter anatomy, white matter connectivity, and functional activations in response to print and language. We also summarize findings concerning brain plasticity in response to interventions.
RESULTS
We highlight evidence relating brain function and structure to instructional issues such as diagnosis and prognosis. We also highlight evidence about brain differences in early childhood, before formal reading instruction in school, which supports the importance of early identification and intervention.
CONCLUSION
Neuroimaging studies of dyslexia reveal how the disorder is related to differences in structure and function in multiple neural circuits.
Topics: Brain; Child; Child, Preschool; Cognition; Dyslexia; Humans; Neuroimaging; Neuronal Plasticity; Reading
PubMed: 30458541
DOI: 10.1044/2018_LSHSS-DYSLC-18-0020 -
Current Opinion in Psychiatry Mar 2021Within the past decade tremendous advances have occurred in our understanding of dyslexia. (Review)
Review
PURPOSE OF REVIEW
Within the past decade tremendous advances have occurred in our understanding of dyslexia.
RECENT FINDINGS
Reliable data now validate the definition of dyslexia as an unexpected difficulty in reading in an individual who has the ability to be a much better reader. That dyslexia is unexpected is now codified in US federal law (PL 115-391). Replicated studies using functional brain imaging have documented a neural signature for dyslexia. Epidemiologic, longitudinal data now demonstrate that dyslexia is highly prevalent, affecting 20% of the population, affecting boys and girls equally. These data further demonstrate that the achievement gap between dyslexic and typical readers is now evident as early as first grade and persists. Evidence-based, efficient, inexpensive screening tools now offer the possibility of universal screening to identify children at risk for dyslexia as early as first grade. Specialized schools which focus on dyslexic students provide welcoming communities, ensuring that dyslexic children will not only survive but thrive.
SUMMARY
Taken together, these findings indicate that we must act and act now to ensure that this 21st century knowledge of dyslexia is disseminated to educators, policy makers, and most of all to parents of dyslexic children.
Topics: Achievement; Brain Mapping; Dyslexia; Humans; Mass Screening; Reading
PubMed: 33278155
DOI: 10.1097/YCO.0000000000000670 -
Language, Speech, and Hearing Services... Oct 2018Children with dyslexia often have related writing difficulties. In the simple view of writing model, high-quality writing depends on good transcription skills, working... (Review)
Review
PURPOSE
Children with dyslexia often have related writing difficulties. In the simple view of writing model, high-quality writing depends on good transcription skills, working memory, and executive function-all of which can be difficult for children with dyslexia and result in poor spelling and low overall writing quality. In this article, we describe the challenges of children with dyslexia in terms of the simple view of writing and instructional strategies to increase spelling and overall writing quality in children with dyslexia.
METHOD
For spelling strategies, we conducted systematic searches across 2 databases for studies examining the effectiveness of spelling interventions for students with dyslexia as well as including studies from 2 meta-analyses. To locate other instructional practices to increase writing quality (e.g., handwriting and executive function), we examined recent meta-analyses of writing and supplemented that by conducting forward searches.
RESULTS
Through the search, we found evidence of effective remedial and compensatory intervention strategies in spelling, transcription, executive function, and working memory. Some strategies included spelling using sound-spellings and morphemes and overall quality using text structure, sentence combining, and self-regulated strategy development.
CONCLUSIONS
Many students with dyslexia experience writing difficulty in multiple areas. However, their writing (and even reading) skills can improve with the instructional strategies identified in this article. We describe instructional procedures and provide links to resources throughout the article.
Topics: Child; Dyslexia; Humans; Language Therapy; Writing
PubMed: 30458545
DOI: 10.1044/2018_LSHSS-DYSLC-18-0024 -
Nature Genetics Nov 2022Reading and writing are crucial life skills but roughly one in ten children are affected by dyslexia, which can persist into adulthood. Family studies of dyslexia...
Reading and writing are crucial life skills but roughly one in ten children are affected by dyslexia, which can persist into adulthood. Family studies of dyslexia suggest heritability up to 70%, yet few convincing genetic markers have been found. Here we performed a genome-wide association study of 51,800 adults self-reporting a dyslexia diagnosis and 1,087,070 controls and identified 42 independent genome-wide significant loci: 15 in genes linked to cognitive ability/educational attainment, and 27 new and potentially more specific to dyslexia. We validated 23 loci (13 new) in independent cohorts of Chinese and European ancestry. Genetic etiology of dyslexia was similar between sexes, and genetic covariance with many traits was found, including ambidexterity, but not neuroanatomical measures of language-related circuitry. Dyslexia polygenic scores explained up to 6% of variance in reading traits, and might in future contribute to earlier identification and remediation of dyslexia.
Topics: Child; Adult; Humans; Genome-Wide Association Study; Dyslexia; Reading; Language; Asian People
PubMed: 36266505
DOI: 10.1038/s41588-022-01192-y -
Language, Speech, and Hearing Services... Oct 2018The purpose of this tutorial is to discuss the language basis of dyslexia in the context of developmental language disorders (DLDs). Whereas most studies have focused on... (Review)
Review
PURPOSE
The purpose of this tutorial is to discuss the language basis of dyslexia in the context of developmental language disorders (DLDs). Whereas most studies have focused on the phonological skills of children with dyslexia, we bring attention to broader language skills.
METHOD
We conducted a focused literature review on the language basis of dyslexia from historical and theoretical perspectives with a special emphasis on the relation between dyslexia and DLD and on the development of broader language skills (e.g., vocabulary, syntax, and discourse) before and after the identification of dyslexia.
RESULTS
We present clinically relevant information on the history of dyslexia as a language-based disorder, the operational definitions used to diagnose dyslexia in research and practice, the relation between dyslexia and DLD, and the language abilities of children with dyslexia.
CONCLUSIONS
We discuss 3 clinical implications for working with children with dyslexia in school settings: (a) Children with dyslexia-with and without comorbid DLDs-often have language deficits outside the phonological domain; (b) intervention should target a child's strengths and weaknesses relative to reading outcomes, regardless of diagnostic labels; and (c) those who have dyslexia, regardless of language abilities at the time of diagnosis, may be at risk for slower language acquisition across their lifetime. Longitudinal studies are needed to assess multiple language skills early, at the time of the diagnosis of dyslexia, and years later to better understand the complex development of language and reading in children with dyslexia.
Topics: Child; Child Language; Child, Preschool; Dyslexia; Humans; Language Development Disorders; Language Tests; Language Therapy
PubMed: 30458538
DOI: 10.1044/2018_LSHSS-DYSLC-18-0049 -
Pediatrics Jul 2020Dyslexia is a common learning disorder that renders children susceptible to poor health outcomes and many elements of socioeconomic difficulty. It is commonly... (Review)
Review
Dyslexia is a common learning disorder that renders children susceptible to poor health outcomes and many elements of socioeconomic difficulty. It is commonly undiagnosed until a child has repeatedly failed to learn to read in elementary school; this late diagnosis not only places the child at an academic disadvantage but also can be a precursor to psychiatric comorbidities such as anxiety and depression. Genetic and neuroimaging research have revealed that dyslexia is heritable and that it is undergirded by brain differences that are present even before reading instruction begins. Cognitive-behavioral research has revealed that there are early literacy skill deficits that represent red flags for dyslexia risk and can be measured at a preschool age. Altogether, this evidence points to dyslexia as a disorder that can be flagged by a pediatrician before school entry, during a period of heightened brain plasticity when interventions are more likely to be effective. In this review, we discuss the clinical implications of the most recent advances in dyslexia research, which converge to indicate that early identification and screening are crucial to the prevention or mitigation of adverse secondary consequences of dyslexia. We further highlight evidence-based and practical strategies for the implementation of early risk identification in pediatric practice so that physicians can be empowered in their ability to treat, educate, and advocate for their patients and families with dyslexia.
Topics: Child; Dyslexia; Early Diagnosis; Humans; Lactones; Learning; Neuroimaging; Reading; Risk Factors
PubMed: 32576595
DOI: 10.1542/peds.2019-3046 -
Handbook of Clinical Neurology 2021Alexia refers to a reading disorder caused by some form of acquired brain pathology, most commonly a stroke or tumor, in a previously literate subject. In...
Alexia refers to a reading disorder caused by some form of acquired brain pathology, most commonly a stroke or tumor, in a previously literate subject. In neuropsychology, a distinction is made between central alexia (commonly seen in aphasia) and peripheral alexia (a perceptual or attentional deficit). The prototypical peripheral alexia is alexia without agraphia (pure alexia), where patients can write but are impaired in reading words and letters. Pure alexia is associated with damage to the left ventral occipitotemporal cortex (vOT) or its connections. Hemianopic alexia is associated with less extensive occipital damage and is caused by a visual field defect, which creates problems reading longer words and passages of text. Reading impairment can also arise due to attentional deficits, most commonly following right hemisphere or bilateral lesions. Studying patients with alexia, along with functional imaging studies of normal readers, has improved our understanding of the neurobiological processes involved in reading. A key question is whether an area in the left ventral occipitotemporal cortex is specialized for or selectively involved in word processing, or whether reading relies on tuning of more general purpose perceptual areas. Reading deficits may also be observed in dementia and traumatic brain injury, but often with less consistent deficit patterns than in patients with focal lesions.
Topics: Cerebral Cortex; Dyslexia; Humans; Stroke
PubMed: 33832678
DOI: 10.1016/B978-0-12-821377-3.00010-6 -
Cortex; a Journal Devoted To the Study... Dec 2022While pure alexia was long considered a disconnection syndrome, it may also be a selective visual word agnosia due to damage to the visual word form area. Disconnection...
While pure alexia was long considered a disconnection syndrome, it may also be a selective visual word agnosia due to damage to the visual word form area. Disconnection is still the likely explanation of hemi-alexias, though, particularly when splenial lesions damage inter-hemispheric projections and cause left hemi-alexia. An intra-hemispheric disconnection causing right hemi-alexia is theoretically possible but seems very rare, with only a single report that has been challenged on the grounds of inadequate perimetry. We describe the case of PH, who had a severe reading deficit in her right hemifield. Detailed perimetry showed only a small relative hemi-scotoma along the horizontal meridian, while word reading was impaired over a much larger expanse of her right hemifield, in which object recognition was spared. Reading, lexical decisions, and perceptual discrimination of words were impaired in the right hemifield, and this extended to letters and numbers, with a trend to an effect on the perception of an unfamiliar script, namely Korean. On magnetic resonance imaging she had a large left lateral occipital meningioma with vasogenic edema of occipital white matter tracts. Functional magnetic resonance imaging showed that the visual word form area was located just anterior to the mass. Her perceptual abnormalities resolved after resection of the tumor. We conclude that right hemi-alexia exists and is most likely due to intra-hemispheric disconnection of occipital input to the visual word form area.
Topics: Humans; Female; Dyslexia; Alexia, Pure; Reading; Visual Perception; Magnetic Resonance Imaging
PubMed: 36370599
DOI: 10.1016/j.cortex.2022.09.015