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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 -
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 -
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 -
Pediatrics and Neonatology May 2021There is a growing interest in understanding dyslexia and the mechanisms involved in reading difficulties. Inquiries into the morphological and physiological changes of... (Review)
Review
There is a growing interest in understanding dyslexia and the mechanisms involved in reading difficulties. Inquiries into the morphological and physiological changes of the brain have contributed to our increased understanding of reading ability and dyslexia. Similarly, inquiries into brain chemistry and reading provide a neurometabolic framework of dyslexia in terms of poor reading and phonological measures. Also, studies of the genetic etiology of reading yield substantial evidence of genes and SNPs associated with dyslexia. However, little is known about the interface between these distinct areas of knowledge. Therefore, we offer an exhaustive perspective on dyslexia using the idea of modularity by assimilating the findings and implications from the brain morphological, neurophysiological, neurochemical, genetic, and educational insights into dyslexia. We contend that this endeavor will provide a beneficial foundation for aiming at the possibilities of a holistic intervention and informed solutions for reading difficulties.
Topics: Brain; Cognition; Dyslexia; Humans; Reading
PubMed: 33775610
DOI: 10.1016/j.pedneo.2021.03.001 -
Handbook of Clinical Neurology 2022The acquisition of reading by children is supported by deep changes in the brain systems devoted to vision and language. The left temporal lobe contributes critically to... (Review)
Review
The acquisition of reading by children is supported by deep changes in the brain systems devoted to vision and language. The left temporal lobe contributes critically to both systems, and lesions affecting it may therefore cause both peripheral vision-related and central language-related reading impairments. The diversity of peripheral dyslexias reflects the anatomical and functional division of the visual cortex into early visual regions, whose lesions have a limited impact on reading; ventral regions, whose lesions are mostly associated to Pure Alexia; and dorsal regions, whose lesions may yield spatial, neglect-related, and attentional dyslexias. Similarly, central alexias reflect the broad distinction, within language processes, between phonological and lexico-semantic components. Phonological and surface dyslexias roughly result from impairment of the former and the latter processes, respectively, while deep dyslexia may be seen as the association of both. In this chapter, we review such types of acquired dyslexias, their clinical features, pathophysiology, and anatomical correlates.
Topics: Child; Dyslexia, Acquired; Humans; Language; Perceptual Disorders; Reading; Semantics
PubMed: 35964977
DOI: 10.1016/B978-0-12-823493-8.00003-1 -
International Journal of Language &... Nov 2020Every language has certain specific idiosyncrasies in its writing system. Cross-linguistic analyses of alexias and agraphias are fundamental to understand commonalities...
BACKGROUND
Every language has certain specific idiosyncrasies in its writing system. Cross-linguistic analyses of alexias and agraphias are fundamental to understand commonalities and differences in the brain organization of written language. Few reports of alexias and agraphias in the Spanish language are currently available.
AIMS
To analyse the clinical manifestations of alexias and agraphias in Spanish, and the effect of demographic variables.
METHODS & PROCEDURES
Spanish versions of the Western Aphasia Battery (WAB) and Boston Diagnostic Aphasia Examination (BDAE) were used for language assessment. Lesion localization was obtained by using computed axial tomography and magnetic resonance imaging. The final sample included 200 patients: 195 (97.5%) right-handed and five (2.5%) left-handed; 119 men and 81 women with a mean age of 57.37 years (SD = 15.56), education of 13.52 years (SD = 4.08), and mean time post-onset of 6.58 months (SD = 12.94). Using the WAB, four quotients were calculated: aphasia quotient (AQ), reading-writing quotient (RWQ), language quotient (LQ) and cortical quotient (CQ).
OUTCOMES & RESULTS
The types of aphasia were: global = 11 patients (5.5%), Broca = 31 (15.5%), Wernicke = 30 (15.0%), conduction = 22 (11.0%), transcortical sensory = 17 (8.5%), transcortical motor = 3 (1.5%), amnesic or anomic = 54 (27.0%) and mixed non-fluent = 32 (16.0%). The degree of oral and written language impairment differed across the various aphasia types. Most severe reading and writing difficulties were found in global, mixed non-fluent and transcortical motor aphasia; fewer difficulties were observed in amnesic, Broca and conduction aphasia. The severity of the written language impairments paralleled the severity of the oral language disturbances. Age negatively, while schooling positively, correlated with the scores in reading and writing tests. No effect of sex and time since onset was found.
CONCLUSIONS & IMPLICATIONS
In Spanish-speaking aphasia patients, difficulties in reading and writing are similar to oral language difficulties. This similarity of performance is mostly based on severity rather than the participants' patterns of errors. What this paper adds What is already known on the subject There is limited information about alexia and agraphia in Spanish. What this paper adds to existing knowledge An extensive study with a large sample of patients. What are the potential or actual clinical implications of this work? The study contributes to the clinical management of patients with reading and writing disturbances.
Topics: Agraphia; Brain; Chile; Databases, Factual; Dyslexia, Acquired; Female; Humans; Language; Language Tests; Linguistics; Male; Middle Aged; Reading; Tomography, X-Ray Computed
PubMed: 32735061
DOI: 10.1111/1460-6984.12566 -
Journal of Neuroscience Research May 2023Over the last 40 years, ever-growing interest in sex-related differences in the human brain has led to a vast amount of literature on the subject, a small part of which... (Review)
Review
Over the last 40 years, ever-growing interest in sex-related differences in the human brain has led to a vast amount of literature on the subject, a small part of which relates to studies of differences in the ability to read. The data concerning typically developing children mainly come from school-based screening projects (Programme for International Student Assessment, INVALSI) and partially from the standardization of reading tests. These have revealed the existence of a gap in favor of females that primarily appears during adolescence and in situations of sociocultural disadvantage, usually explained on the basis of environmental factors such as socioeconomic status and gender-based education. Dyslexia is a neurodevelopmental disorder that is significantly more prevalent among males, a difference that neuroimaging and genetic studies have attributed to the presence of hormone-related protective factors in females, although it has been hypothesized that a different neurocognitive substrate may also be involved. However, the literature on the subject is still limited, and further studies of the interactions between genetic risk, environmental factors, and brain phenotypes are needed to clarify why females are better at performing reading tasks and less susceptible to dyslexia, regardless of their language or the educational system in the country in which they live. The aim of this mini-review was to describe the studies that have investigated sex-related differences in reading ability in both typically and atypically developing subjects.
Topics: Male; Child; Female; Adolescent; Humans; Reading; Dyslexia; Brain; Risk Factors; Neuroimaging
PubMed: 34240762
DOI: 10.1002/jnr.24913 -
Medicina Mar 2023Beyond the frequent coexistence of attention deficit hyperactivity disorder (ADHD) and reading disorder (dyslexia), the present review aims to examine the available... (Review)
Review
Beyond the frequent coexistence of attention deficit hyperactivity disorder (ADHD) and reading disorder (dyslexia), the present review aims to examine the available empirical evidence on how ADHD negatively impacts on learning to read. Existing data suggest that the presence of the disorder (especially inattention symptoms), may affect i) the correct acquisition of reading, either directly or through its influence on the precursors to reading; ii) decoding skills themselves (reading accuracy and fluency), both directly and indirectly through its influence on cognitive processes such as distractibility or executive functions; and iii) reading comprehension, probably indirectly through the executive and verbal memory difficulties characteristic of ADHD. These findings have important implications for better characterizing and intervening on reading difficulties in ADHD, whether clinical or subclinical.
Topics: Humans; Attention Deficit Disorder with Hyperactivity; Comprehension; Learning; Cognition; Executive Function; Dyslexia
PubMed: 36820478
DOI: No ID Found