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Communications Biology Dec 2021For over 150 years, the study of patients with acquired alexia has fueled research aimed at disentangling the neural system critical for reading. An unreached goal,...
For over 150 years, the study of patients with acquired alexia has fueled research aimed at disentangling the neural system critical for reading. An unreached goal, however, relates to the determination of the fiber pathways that root the different visual and linguistic processes needed for accurate word reading. In a unique series of neurosurgical patients with a tumor close to the visual word form area, we combine direct electrostimulation and population-based streamline tractography to map the disconnectivity fingerprints characterizing dissociated forms of alexia. Comprehensive analyses of disconnectivity matrices establish similarities and dissimilarities in the disconnection patterns associated with pure, phonological and lexical-semantic alexia. While disconnections of the inferior longitudinal and posterior arcuate fasciculi are common to all alexia subtypes, disconnections of the long arcuate and vertical occipital fasciculi are specific to phonological and pure alexia, respectively. These findings provide a strong anatomical background for cognitive and neurocomputational models of reading.
Topics: Adult; Alexia, Pure; Dyslexia; Female; Humans; Male; Middle Aged; Nerve Net; Reading; White Matter; Young Adult
PubMed: 34931059
DOI: 10.1038/s42003-021-02943-z -
Psychological Bulletin May 2016This article reviews 95 publications (based on 21 independent samples) that have examined children at family risk of reading disorders. We report that children at family... (Meta-Analysis)
Meta-Analysis Review
This article reviews 95 publications (based on 21 independent samples) that have examined children at family risk of reading disorders. We report that children at family risk of dyslexia experience delayed language development as infants and toddlers. In the preschool period, they have significant difficulties in phonological processes as well as with broader language skills and in acquiring the foundations of decoding skill (letter knowledge, phonological awareness and rapid automatized naming [RAN]). Findings are mixed with regard to auditory and visual perception: they do not appear subject to slow motor development, but lack of control for comorbidities confounds interpretation. Longitudinal studies of outcomes show that children at family risk who go on to fulfil criteria for dyslexia have more severe impairments in preschool language than those who are defined as normal readers, but the latter group do less well than controls. Similarly at school age, family risk of dyslexia is associated with significantly poor phonological awareness and literacy skills. Although there is no strong evidence that children at family risk are brought up in an environment that differs significantly from that of controls, their parents tend to have lower educational levels and read less frequently to themselves. Together, the findings suggest that a phonological processing deficit can be conceptualized as an endophenotype of dyslexia that increases the continuous risk of reading difficulties; in turn its impact may be moderated by protective factors. (PsycINFO Database Record
Topics: Child, Preschool; Dyslexia; Humans; Infant; Language Development Disorders; Language Tests; Literacy; Longitudinal Studies; Phonetics
PubMed: 26727308
DOI: 10.1037/bul0000037 -
Journal of Learning Disabilities 2020How prevalent is dyslexia? A definitive answer to this question has been elusive because of the continuous distribution of reading performance and predictors of dyslexia...
How prevalent is dyslexia? A definitive answer to this question has been elusive because of the continuous distribution of reading performance and predictors of dyslexia and because of the heterogeneous nature of samples of poor readers. Samples of poor readers are a mixture of individuals whose reading is consistent with or expected based on their performance in other academic areas and in language, and individuals with dyslexia whose reading is not consistent with or expected based on their other performances. In the present article, we replicate and extend a new approach for determining the prevalence of dyslexia. Using model-based meta-analysis and simulation, three main results were found. First, the prevalence of dyslexia is better represented as a distribution that varies as a function of severity as opposed to any single-point estimate. Second, samples of poor readers will contain more expected poor readers than unexpected or dyslexic readers. Third, individuals with dyslexia can be found across the reading spectrum as opposed to only at the lower tail of reading performance. These results have implications for screening and identification, and for recruiting participants for scientific studies of dyslexia.
Topics: Academic Performance; Bayes Theorem; Child; Comprehension; Computer Simulation; Dyslexia; Humans; Language Tests; Meta-Analysis as Topic; Models, Psychological; Models, Statistical; Prevalence
PubMed: 32452713
DOI: 10.1177/0022219420920377 -
Wiley Interdisciplinary Reviews.... 2016Developmental dyslexia is an unexplained inability to acquire accurate or fluent reading that affects approximately 5-17% of children. Dyslexia is associated with... (Review)
Review
Developmental dyslexia is an unexplained inability to acquire accurate or fluent reading that affects approximately 5-17% of children. Dyslexia is associated with structural and functional alterations in various brain regions that support reading. Neuroimaging studies in infants and pre-reading children suggest that these alterations predate reading instruction and reading failure, supporting the hypothesis that variant function in dyslexia susceptibility genes lead to atypical neural migration and/or axonal growth during early, most likely in utero, brain development. Yet, dyslexia is typically not diagnosed until a child has failed to learn to read as expected (usually in second grade or later). There is emerging evidence that neuroimaging measures, when combined with key behavioral measures, can enhance the accuracy of identification of dyslexia risk in pre-reading children but its sensitivity, specificity, and cost-efficiency is still unclear. Early identification of dyslexia risk carries important implications for dyslexia remediation and the amelioration of the psychosocial consequences commonly associated with reading failure.
Topics: Animals; Biomarkers; Brain; Brain Mapping; Child; Child, Preschool; Diffusion Tensor Imaging; Dyslexia; Electroencephalography; Evoked Potentials; Female; Humans; Infant; Infant, Newborn; Magnetic Resonance Imaging; Reading; Risk Factors; Speech Perception
PubMed: 26836227
DOI: 10.1002/wcs.1383 -
Journal of Autism and Developmental... Feb 2014Although best known for work with children and adults with intellectual disabilities and autism spectrum disorders, training in speech pathology and a doctorate in... (Review)
Review
Although best known for work with children and adults with intellectual disabilities and autism spectrum disorders, training in speech pathology and a doctorate in clinical psychology and neuropsychology was the foundation for Sara Sparrow's long-term interest in reading disabilities. Her first papers were on dyslexia and laterality, and the maturational lag theory of developmental dyslexia proposed with Paul Satz, her mentor. The research program that emerged from this work had a wide impact on early neuropsychological models of reading disabilities. Although Sara went on to research focused on children with other developmental disabilities after she moved to Yale University, this initial research influenced her career- long interests in assessment, developmental models of disabilities, and early screening methods.
Topics: Adult; Brain; Child; Dyslexia; Female; Functional Laterality; Humans; Radiography; Reading
PubMed: 21594745
DOI: 10.1007/s10803-011-1273-2 -
Journal of Neurodevelopmental Disorders Aug 2023Developmental dyslexia (DD) and attention deficit/hyperactivity disorder (ADHD) are highly comorbid neurodevelopmental disorders. Individuals with DD or ADHD have both...
BACKGROUND
Developmental dyslexia (DD) and attention deficit/hyperactivity disorder (ADHD) are highly comorbid neurodevelopmental disorders. Individuals with DD or ADHD have both been shown to have deficits in white matter tracts associated with reading and attentional control networks. However, white matter diffusivity in individuals comorbid with both DD and ADHD (DD + ADHD) has not been specifically explored.
METHODS
Participants were 3 and 4 graders (age range = 7 to 11 years; SD = 0.69) from three diagnostic groups ((DD (n = 40), DD + ADHD (n = 22), and typical developing (TD) (n = 20)). Behavioral measures of reading and attention alongside measures of white matter diffusivity were collected for all participants.
RESULTS
DD + ADHD and TD groups differed in mean fractional anisotropy (FA) for the left and right Superior Longitudinal Fasciculus (SLF)-Parietal Terminations and SLF-Temporal Terminations. Mean FA for the DD group across these SLF tracts fell between the lower DD + ADHD and higher TD averages. No differences in mean diffusivity nor significant brain-behavior relations were found.
CONCLUSIONS
Findings suggest that WM diffusivity in the SLF increases along a continuum across DD + ADHD, DD, and TD.
Topics: White Matter; Dyslexia; Attention Deficit Disorder with Hyperactivity; Analysis of Variance; Attention; Humans; Child; Reading; Executive Function
PubMed: 37550628
DOI: 10.1186/s11689-023-09495-9 -
Journal of Learning Disabilities 2022Several crucial reasons exist to determine whether an adult has had a reading disorder (RD) and to predict a child's likelihood of developing RD. The Adult Reading...
Several crucial reasons exist to determine whether an adult has had a reading disorder (RD) and to predict a child's likelihood of developing RD. The Adult Reading History Questionnaire (ARHQ) is among the most commonly used self-reported questionnaires. High ARHQ scores indicate an increased likelihood that an adult had RD as a child and that their children may develop RD. This study focused on whether a subset of ARHQ items (ARHQ-Brief) could be equally effective in assessing adults' reading history as the full ARHQ. We used a machine learning approach, lasso (known as L1 regularization), and identified 6 of 23 items that resulted in the ARHQ-Brief. Data from 97 adults and 47 children were included. With the ARHQ-Brief, we report a threshold of 0.323 as suitable to identify past likelihood of RD in adults with a sensitivity of 72.4% and a specificity of 81.5%. Comparison of predictive performances between ARHQ-Brief and the full ARHQ showed that ARHQ-Brief explained an additional 10%-35.2% of the variance in adult and child reading. Furthermore, we validated ARHQ-Brief's superior ability to predict reading ability using an independent sample of 28 children. We close by discussing limitations and future directions.
Topics: Adult; Child; Cognition; Dyslexia; Humans; Machine Learning; Surveys and Questionnaires
PubMed: 34628989
DOI: 10.1177/00222194211047631 -
Proceedings. Biological Sciences May 2015Developmental dyslexia runs in families, and twin studies have confirmed that there is a substantial genetic contribution to poor reading. The way in which discoveries... (Review)
Review
Developmental dyslexia runs in families, and twin studies have confirmed that there is a substantial genetic contribution to poor reading. The way in which discoveries in molecular genetics are reported can be misleading, encouraging us to think that there are specific genes that might be used to screen for disorder. However, dyslexia is not a classic Mendelian disorder that is caused by a mutation in a single gene. Rather, like many other common disorders, it appears to involve combined effects of many genes and environmental factors, each of which has a small influence, possibly supplemented by rare variants that have larger effects but apply to only a minority of cases. Furthermore, to see clearer relationships between genotype and phenotype, we may need to move beyond the clinical category of dyslexia to look at underlying cognitive deficits that may be implicated in other neurodevelopmental disorders.
Topics: Cognition Disorders; Dyslexia; Genotype; Humans; Phenotype
PubMed: 25854887
DOI: 10.1098/rspb.2014.3139 -
Neurologia (Barcelona, Spain) 2010Dyslexia is a learning disability in which reading (but not any other) impairment is the most prominent symptom. There seems to be a high comorbidity among dyslexia and... (Review)
Review
INTRODUCTION
Dyslexia is a learning disability in which reading (but not any other) impairment is the most prominent symptom. There seems to be a high comorbidity among dyslexia and other learning disabilities, such as SLI, SSD or ADHD.
DEVELOPMENT
The nulear deficit in dyslexia appears to correspond to an impairment in phonological processing. Structural and functional studies in dyslexic readers converge to indicate the presence of malformations in the brain areas corresponding to the reading systems, but also a failure of these systems to function properly during reading. Genes linked (or associated) to dyslexia have been shown to be involved in neuronal migration and axon guidance during the formation of the cortex. In the developing cerebral neocortex of rats, local loss of function of most of these genes not only results in abnormal neuronal migration and neocortical and hippocampal malformations, but also in deficits related to auditory processing and learning. While the structural malformations resemble neuronal migration abnormalities observed in the brains of individuals with developmental dyslexia, processing/learning deficits also resemble deficits described in individuals affected by the disease.
CONCLUSIONS
On the whole, dyslexia seems to be on a continuum with typical reading at different biological levels (genetic, biochemical, physiological, cognitive). Furthermore, certain elements belonging to some of these levels (mainly -some of the- genes linked or associated to the disease, but also -some of the- neuronal structures whose development is regulated by these genes) would simultaneously belong to those of other cognitive abilities, which give rise to diseases of a different nature (i.e. non- dyslexic impairments) when they are impaired.
Topics: Animals; Brain; Comorbidity; Cytoskeletal Proteins; Dyslexia; Humans; Learning Disabilities; Nerve Tissue Proteins; Neurobiology; Nuclear Proteins; Protein Isoforms; Reading
PubMed: 21093706
DOI: 10.1016/j.nrl.2009.12.010 -
The European Journal of Neuroscience Nov 2018The capacity for language is one of the key features underlying the complexity of human cognition and its evolution. However, little is known about the neurobiological... (Review)
Review
The capacity for language is one of the key features underlying the complexity of human cognition and its evolution. However, little is known about the neurobiological mechanisms that mediate normal or impaired linguistic ability. For developmental dyslexia, early postmortem studies conducted in the 1980s linked the disorder to subtle defects in the migration of neurons in the developing neocortex. These early studies were reinforced by human genetic analyses that identified dyslexia susceptibility genes and subsequent evidence of their involvement in neuronal migration. In this review, we examine recent experimental evidence that does not support the link between dyslexia and neuronal migration. We critically evaluate gene function studies conducted in rodent models and draw attention to the lack of robust evidence from histopathological and imaging studies in humans. Our review suggests that the neuronal migration hypothesis of dyslexia should be reconsidered, and the neurobiological basis of dyslexia should be approached with a fresh start.
Topics: Animals; Cell Movement; Disease Models, Animal; Dyslexia; Genetic Predisposition to Disease; Humans; Neocortex; Neurons
PubMed: 30218584
DOI: 10.1111/ejn.14149