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We summarize some of the most important findings from research evaluating the hypothesized causes of specific reading disability ('dyslexia') over the past four decades. After outlining components of reading ability, we discuss manifest causes of reading difficulties, in terms of deficiencies in component reading skills that might lead to such difficulties. The evidence suggests that inadequate facility in word identification due, in most cases, to more basic deficits in alphabetic coding is the basic cause of difficulties in learning to read. We next discuss hypothesized deficiencies in reading-related cognitive abilities as underlying causes of deficiencies in component reading skills. The evidence in these areas suggests that, in most cases, phonological skills deficiencies associated with phonological coding deficits are the probable causes of the disorder rather than visual, semantic, or syntactic deficits, although reading difficulties in some children may be associated with general language deficits. Hypothesized deficits in general learning abilities (e.g., attention, association learning, cross-modal transfer etc.) and low-level sensory deficits have weak validity as causal factors in specific reading disability. These inferences are, by and large, supported by research evaluating the biological foundations of dyslexia. Finally, evidence is presented in support of the idea that many poor readers are impaired because of inadequate instruction or other experiential factors. This does not mean that biological factors are not relevant, because the brain and environment interact to produce the neural networks that support reading acquisition. We conclude with a discussion of the clinical implications of the research findings, focusing on the need for enhanced instruction.

Background\ud \ud Executive functioning (EF) deficits are well recognized in developmental dyslexia, yet the majority of studies have concerned children rather than adults, ignored the subjective experience of the individual with dyslexia (with regard to their own EFs), and have not followed current theoretical perspectives on EFs.\ud \ud Aims and Methods\ud \ud The current study addressed these shortfalls by administering a self-report measure of EF (BRIEF-A; Roth, Isquith, & Gioia, 2005) and experimental tasks to IQ-matched groups of adults with and without dyslexia. The laboratory-based tasks tested the three factors constituting the framework of EF proposed by Miyake et al. (2000).\ud \ud Results\ud \ud In comparison to the group without dyslexia, the participants with dyslexia self-reported more frequent EF problems in day-to-day life, with these difficulties centering on metacognitive processes (working memory, planning, task monitoring, and organization) rather than on the regulation of emotion and behaviour. The participants with dyslexia showed significant deficits in EF (inhibition, set shifting, and working memory).\ud \ud Conclusions and Implications\ud \ud The findings indicated that dyslexia-related problems have an impact on the daily experience of adults with the condition. Further, EF difficulties are present in adulthood across a range of laboratory-based measures, and, given the nature of the experimental tasks presented, extend beyond difficulties related solely to phonological processing.

The existing literature on developmental dyslexia (hereafter: dyslexia) often focuses on isolating cognitive skills which differ across dyslexic and control participants. Among potential correlates, previous research has studied group differences between dyslexic and control participants in performance on statistical learning tasks. A statistical learning deficit has been proposed to be a potential cause and/or a marker effect for early detection of dyslexia. It is therefore of practical importance to evaluate the evidence for a group difference. From a theoretical perspective, such a group difference would provide information about the causal chain from statistical learning to reading acquisition. We provide a systematic review of the literature on such a group difference. We conclude that there is insufficient high-quality data to draw conclusions about the presence or absence of an effect.

The problem of causation has proven particularly elusive in the case of developmental dyslexia (DD). The field has been dominated by very general hypotheses, such as the idea that DD is caused by a phonological deficit and/or an impairment of the magnocellular pathway. Results are contrasting and causal unidirectional links have not been persuasively demonstrated.Some studies in the Research Topic (RT) re-examine these general hypotheses from the critical perspective of more selective predictions. Others focus on less general deficit hypotheses and stay closer to reading by investigating specific aspects of the reading process such as orthographic learning ability or the ability to deal with multiple-stimulus displays. Studies benefit from new research paradigms as well as new information from research areas such as neuroimaging or genetics. Below, we sketch the general questions tackled by these studies.

Developmental dyslexia is a reading disorder—but what are the underlying cognitive and neurobiological mechanisms? The variety of different explanations in the literature ranges from phonological abilities via sensory (auditory, visual) processing to attention, learning, and cross-modal integration. Here, we suggest that it is advantageous to accept the variability encountered in dyslexia. Different cognitive profiles, or “fingerprints”, characterise groups of dyslexic individuals. Most importantly, these fingerprints have a repercussion in differential brain activation patterns in dyslexia, supporting the notion of a neurobiological basis. We conclude that considering the neurocognitive fingerprint of a dyslexic reader may be helpful to plan an individually targeted training, which, in turn, may optimise the outcome of remediation.

We used fMRI to explore the extent of the anatomical overlap of three neural systems that the literature on developmental dyslexia associates with reading: the auditory phonological, the visual magnocellular, and the motor/cerebellar systems. Twenty-eight normal subjects performed four tasks during fMRI scans: word and pseudoword reading, auditory rhyming for letter names, visual motion perception, and a motor sequence learning task. We found that the left occipitotemporal cortex (OTC), which previous studies reported to be dysfunctional in dyslexia, can be fractionated into different functional areas: an anterior and lateral area that was activated by both reading and auditory rhyming tasks; a posterior area that was commonly activated by both the reading and the motion perception task and a medial/intermediate area, including the so-called Visual Word Form Area, which was specifically activated by the reading task. These results show that the left OTC is an area of segregated convergence of different functional systems. We compared our results with the hypoactivation pattern reported for reading in a previous cross-cultural PET study on 36 dyslexic subjects from three countries. The region of decreased activation in dyslexia overlapped with regions that are specific for reading and those activated during both the auditory rhyming task and the single word and pseudoword reading task described in the present fMRI study. No overlap was found with the activation patterns for the visual motion perception task or for the motor sequence learning task. These observations challenge current theories of dyslexia.

Biologising the problems of reading has a long tradition. However, modern and non-invasive techniques, like functional magnetic resonance imaging (fMRI), that allow the mapping of changes in brain hemodynamic that corresponds to mental operations, boosted a wave of new research on the subject. This paper traces the history of treating a problem in teaching/learning as a disease-like condition. It also examines the beliefs of professionals in relation to dyslexia, and how they are biased by published research and the imbalance between biological and educational perspectives in published research. Overall, the educational perspective is underrepresented in published research about dyslexia, while the biological perspective is overrepresented. This is puzzling since to date biological perspectives have not produced any effective interventions for dyslexia, and almost all major claims for the biological view remain unproven. Nevertheless, biological models have a great influence on the beliefs of practitioner...

This paper provides a selective review of data on phonology, audition, vision, and learning abilities in developmental dyslexia, with a specific focus on patterns of normal alongside poor performance. Indeed we highlight the difficulties of interpreting poor performance, and we criticize theories of dyslexia that are exclusively suited to explaining poor performance, at the risk of overgeneralizing and predicting deficits in many more situations than are observed. We highlight a number of tasks and conditions where individuals with dyslexia seem to show perfectly normal performance, and we discuss the value of taking such data seriously into account and the difficulties of current theories to explain them. Finally, we discuss the experimental challenges for tasks investigating the nature of cognitive deficits in dyslexia and in other developmental disorders and the challenges for any proper theory of dyslexia aiming to explain cases of normal as well as poor performance.

Long-standing issues with the conceptualization, identification and subtyping of developmental dyslexia persist. This study takes an alternative approach to examine the heterogeneity of developmental dyslexia using taxometric classification techniques. These methods were used with a large sample of 671 children ages 6-8 who were diagnosed with severe reading disorders. Latent characteristics of the sample are assessed in regard to posited subtypes with phonological deficits and naming speed deficits, thus extending prior work by addressing whether these deficits embody separate classes of individuals. Findings support separate taxa of dyslexia with and without phonological deficits. Different latent structure for naming speed deficits was found depending on the definitional criterion used to define dyslexia. Non-phonologically based forms of dyslexia showed particular difficulty with naming speed and reading fluency.

Summary Background The visuospatial deficit is recognized as typical for dyslexia only in some definitions. However problems with visuospatial orientation may manifest themselves as difficulties with letter identification or the memorizing and recalling of sign sequences, something frequently experienced by dyslexics. Material/Methods The experimental group consisted of 62 children with developmental dyslexia. The control group consisted of 67 pupils with no diagnosed deficits, matched to the clinical group in terms of age. We used the Clock Drawing Test (CDT), the Spatial Span subtest from the Wechsler Memory Scale – third edition (WMS – III), the Rey-Osterrieth Complex Figure Test in order to analyze visuospatial functioning. Results The results show that dyslexics experienced problems with visuospatial functioning, however only while performing difficult tasks. Significant group differences were found for the Clock Drawing Test, Spatial Span – Backward and the precision of figure coping in the Rey-Osterrieth Test. In addition, the results of dyslexic boys were lower than those obtained by all other groups. Conclusions Our findings provide support for the hypothesis concerning visual deficit as characteristic for dyslexia.

Previous research into the cognitive processes involved in reading Chinese and developmental dyslexia in Chinese, revealed that the single most important factor appears to be orthographic processing skills rather than phonological skills. Also some studies have indicated that even in alphabetic languages some dyslexic individuals reveal deficits in orthographic processing skills, which are linked to a deficit in the visual magnocellular pathway. The current study therefore employed a visual psychophysical experiment together with visual and auditory event-related potential (ERP) experiments eliciting mismatch negativity (MMN) to investigate the link between visual magnocellular functional abnormalities and developmental dyslexia in Chinese. The performance levels of Chinese children with developmental dyslexia (DD) from the behavioural and electrophysiological experiments were compared to those of the chronological age-matched (CA) children and those of the reading level matched (RL) younger children. Both the behavioural and electrophysiological results suggest that the orthographic processing skills were compromised in the Chinese developmental dyslexics, which in turn is linked to a deficit in the visual magnocellular system.

SummaryFirst described over 100 years ago, developmental dyslexia (reading disability) has been a controversial subject. There has been much confusion regarding the definition, the psychological basis, the conceptualisation and even the name. Recent research has helped us to understand the main underlying cognitive deficits that lead to poor reading. Brain imaging studies conducted during the performance of reading tasks have shed light on its biological basis and genetic studies have identified a number of genes that are associated with reading difficulties. Together, these studies have led to a redefinition and new understanding of developmental dyslexia. This article examines these recent findings. A second article to appear in Advances will focus on clinical aspects of the disorder.

Specific reading disability, or dyslexia, co-occurs with other developmental disorders at higher rates than would be predicted by chance. Significant comorbidity has been reported between dyslexia ...

本研究の目的は, 日本語話者の発達性読み書き障害児における視覚情報処理過程を体系的に評価し発達性読み書き障害の背景となる認知障害構造を明らかにすることである. 対象は日本語話者の発達性読み書き障害児20名と定型発達児59名である. 視機能, 視知覚, 視覚認知機能および視覚性記憶機能を測定, 評価した. 本研究の結果から, 視機能の問題は読み書きの正確性に大きな影響を与えないのではないかと思われた. 線分の傾き知覚と視覚性記憶機能は本研究で対象とした発達性読み書き障害児全例で低下していた. 視知覚と関連のあるvisual magnocellular systemとvisual parvocellular systemを検討した結果, 双方の視覚経路で機能低下を認める発達性読み書き障害児が20名中８名いた. 日本語圏の発達性読み書き障害児は海外での報告とは異なり２つの視覚経路の問題を併せもつことが多いのではないかと思われた.

本研究の目的は, 発達性ディスレクシア (DD) と後天性の大脳損傷によって生じる失読失書例との共通点と相違点について要素的認知機能の発達や局在化に関して検討することである. DD群は10名の右手利き例である. 失読失書例は右利きの男児2名である. 失読失書症例KYは8歳にてモヤモヤ病術後, 脳梗塞にて軽度失語症を発症し, その後軽微な失語症とともに失読, 失書症状が認められた発症半年後から追跡している症例である. 症例MSは, 8歳時の脳梗塞により健忘失語が観察された10年以上追跡してきている現在21歳の症例である. いずれも, 失語症状は軽微で失読失書症状が中心となる症状であった. SLTAではDD群, 失読失書例ともに読み書きに関連する項目以外は定型発達児群と差がなく音声言語にかかわる項目は正常域であった. DD群における局所血流低下部位は左下頭頂小葉を含む, 側頭頭頂葉結合領域であった. また, 機能的MRIを用いた実験により, 左下頭頂小葉にある縁上回の賦活量に関して典型発達群と比較して異なる部位であった. 一方, 失読失書2例における共通の大脳の損傷部位は左下頭頂小葉であった. DD群ではROCFT (Rey-Osterrieth Complex Figure Test) において遅延再生得点が平均の－1SDよりも得点が少なかったが, 失読失書2例においてはともに得点低下はなかった. 一方, 発達性ディスレクシアと後天性失読の大脳機能低下部位は類似していたが, 非言語的図形の処理能力は, 発達性ディスレクシア群で低く, 後天性失読例では保たれていた. 後天性言語的図形である文字と非言語的図形の処理は, 少なくとも8歳までの発達途上で機能が分離されてきているように思われた.

Contains fulltext : 90398.pdf (Publisher’s version ) (Open Access) Phonological theories of dyslexia assume a specific deficit in representation, storage and recall of phonemes. Various brain imaging techniques, including qEEG, point to the importance of a range of areas, predominantly the left hemispheric temporal areas. This study attempted to reduce reading and spelling deficits in children who are dyslexic by means of neurofeedback training based on neurophysiological differences between the participants and gender and age matched controls. Nineteen children were randomized into an experimental group receiving qEEG based neurofeedback (n = 10) and a control group (n = 9). Both groups also received remedial teaching. The experimental group improved considerably in spelling (Cohen’s d = 3). No improvement was found in reading. An indepth study of the changes in the qEEG power and coherence protocols evidenced no fronto-central changes, which is in line with the absence of reading improvements. A significant increase of alpha coherence was found, which may be an indication that attentional processes account for the improvement in spelling. Consideration of subtypes of dyslexia may refine the results of future studies. 7 p.

Visual-attentional theories of dyslexia predict deficits for dyslexic children not only for the perception of letter strings but also for non-alphanumeric symbol strings. This prediction was tested in a two-alternative forced-choice paradigm with letters, digits, and symbols. Children with dyslexia showed significant deficits for letter and digit strings but not for symbol strings. This finding is difficult to explain for visual-attentional theories of dyslexia which postulate identical deficits for letters, digits and symbols. Moreover, dyslexics showed normal W-shaped serial position functions for letter and digit strings, which suggests that their deficit is not due to an abnormally small attentional window. Finally, the size of the deficit was identical for letters and digits, which suggests that poor letter perception is not just a consequence of the lack of reading. Together then, our results show that symbols that map onto phonological codes are impaired (i.e. letters and digits), whereas symbols that do not map onto phonological codes are not impaired. This dissociation suggests that impaired symbol-sound mapping rather than impaired visual-attentional processing is the key to understanding dyslexia.

Dissecting Dyslexia and Learning Difficulties in learning to read, despite reasonable effort and instruction, form the basis of dyslexia. Gabrieli (p. 280 ; see the cover) now reviews the latest research into the causes of dyslexia. Neuroimaging studies may give early notice of impending dyslexia, and it is hoped that early interventions may lessen the impact of dyslexia. Learning occurs in many settings. Humans uniquely use the formalized settings of schools and curriculum. Infants and children also do plenty of learning outside these settings, often intermingling social interactions. Meltzoff et al. (p. 284 ) survey the variety of learning contexts that people experience and discuss how recent advances in neuroscience and robotics are driving a new synthesis of learning.

There are several group and case studies that investigate developmental dyslexia in children, and acquired and developmental reading disabilities in adults. To date however, there are few detailed investigations on cases of early acquired dyslexia. The purpose of this study was to examine such a case (participant referred to as SP). The goals of this investigation were to compare SP's reading impairments to the major subtypes of dyslexia, establish SP's specific reading deficits, and consider the neuropsychological variables that may impact on SP's reading disability.

本論文では, 発達性dyslexia 1例 (症例ST) と発達性dyslexia 6例 (症例1-6) を対象とし, 成人を対象とした認知神経心理学を発達性dyslexiaに直接適用する際の問題点について述べることを目的とする. 症例１でみられる発達性書字障害の障害構造は従来の二重経路モデルでは解釈しきれず, 同じ症例において音韻障害が認められないにもかかわらずひらがな, カタカナの音読においては, 音韻性dyslexia様の症状を呈することを述べた. 反対に, 発達性dyslexia 6例のうちの5例に関して漢字の非語と非一貫語 (不規則語) の音読成績の乖離を基準に分類すると, 要素的認知機能検査にて音韻障害が認められているにもかかわらず表層性 (surface) dyslexiaと解釈される児童が認められた. 以上のように, 発達性dyslexiaに成人領域でのモデルを直接適用すると矛盾が生じる場合があるように思われ, 発達を考慮したモデルを構築すべきではないかと思われた. しかし, 本報告では症例数, 定型発達児数ともに少ないこと, 十分に統制された刺激が使用されていないこと, 音読年齢を基準に比較されていないことなど, 今後検討されるべき問題点についても言及した.

The Jyvaskyla Longitudinal Study of Dyslexia project (JLD) has followed the development of 200 children from birth until 10 years of age. Half the children are from families in which at least one of the parents has dyslexia, thus the child has a high risk of becoming dyslexic, and half have no such risk. Here the main findings of four studies in linguistics from the JLD project are reviewed. The speech processing skills were studied in 6, 18, 24 and 30-month-old children. The findings show that early signs of dyslexia can be detected in speech processing both phonologically and morphosyntactically. These precursors can be seen in perception or production of duration, in the prosody and phonotactics of word production attempts and word structures, as well as in the complexity of morphosyntactic features of expressions. This information can be useful in practice to provide early and appropriate assistance for those children who most likely will face difficulties in learning to read and write at school.

There are several causal explanations for dyslexia, drawing on distinctions between dyslexics and control groups at genetic, biological, or cognitive levels of description. However, few theories explicitly bridge these different levels of description. In this paper, we review a long-standing theory that some dyslexics' reading impairments are due to impairments in hemispheric transfer. We test this theory in a computational model of reading, implementing anatomical features of the visual system. We demonstrate that, when callosal transfer is impaired, the model reads nonwords as well as an unimpaired model, but reads exception words poorly: a pattern of behaviour similar to surface dyslexia. This computational modelling provides a causal link between brain-based theories of dyslexia to cognitive-level theories that refer specifically to phonological impairments within the reading system.

Academic success and occupational outcome rely on a person's ability to attend to and learn from their surroundings. The cognitive mechanisms underlying these respective skills are impaired in individuals with attention deficit hyperactivity disorder (ADHD) and learning disability (LD). The high co-occurrence between ADHD and the learning disability developmental dyslexia has raised the possibility of a common etiology. We propose that studying the functional anatomy of disordered executive control and reading-related skills using carefully selected paradigms, coupled with rigorous studies of intervention efficacy, provide the most promising avenue for ameliorating these two commonly encountered impediments to learning.

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No. of bitstreams: 2 S1413-85572008000100016.pdf: 206472 bytes, checksum: 1d97a9f282bb758c806b5e28c0d24b07 (MD5) S1413-85572008000100016.pdf.txt: 52930 bytes, checksum: 19c29334a340892976f7c1a78fc7edca (MD5) Previous issue date: 2008-06-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:31:28Z No. of bitstreams: 2 S1413-85572008000100016.pdf: 206472 bytes, checksum: 1d97a9f282bb758c806b5e28c0d24b07 (MD5) S1413-85572008000100016.pdf.txt: 52930 bytes, checksum: 19c29334a340892976f7c1a78fc7edca (MD5) Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:31:28Z No. of bitstreams: 2 S1413-85572008000100016.pdf: 206472 bytes, checksum: 1d97a9f282bb758c806b5e28c0d24b07 (MD5) S1413-85572008000100016.pdf.txt: 52930 bytes, checksum: 19c29334a340892976f7c1a78fc7edca (MD5) Made available in DSpace on 2014-05-20T13:31:28Z (GMT). No. of bitstreams: 2 S1413-85572008000100016.pdf: 206472 bytes, checksum: 1d97a9f282bb758c806b5e28c0d24b07 (MD5) S1413-85572008000100016.pdf.txt: 52930 bytes, checksum: 19c29334a340892976f7c1a78fc7edca (MD5) Previous issue date: 2008-06-01 Made available in DSpace on 2014-05-20T13:31:28Z (GMT). No. of bitstreams: 2 S1413-85572008000100016.pdf: 206472 bytes, checksum: 1d97a9f282bb758c806b5e28c0d24b07 (MD5) S1413-85572008000100016.pdf.txt: 52930 bytes, checksum: 19c29334a340892976f7c1a78fc7edca (MD5) Previous issue date: 2008-06-01 A dislexia do desenvolvimento, dificuldade específica de leitura, é caracterizada pela dificuldade em realizar a decodificação fono-grafêmica e percepção de fonemas acusticamente semelhantes. Este estudo teve como objetivo caracterizar o desempenho de crianças com dislexia quanto às habilidades auditivas e de consciência fonológica, correlacionando-as. Participaram deste estudo crianças com dislexia e com bom desempenho escolar, submetidas a avaliações audiológica, do processamento auditivo e das habilidades fonológicas. Os resultados indicaram diferença estatisticamente significante entre as habilidades auditivas de seqüência para sons verbais, mensagem competitiva ipsi e contra-lateral, dicótico de dígitos e dissílabos alternados e ainda nos subtestes de síntese, segmentação, manipulação e transposição. Os achados deste estudo evidenciaram correlação entre provas de memória auditiva e manipulação silábica e fonêmica e associação entre habilidades auditivas e fonológicas, sugerindo que os processos auditivos interferem diretamente na percepção de aspectos acústicos, temporais e seqüenciais dos sons para formação de uma representação fonológica estável. Developmental dyslexia is a specific reading disability characterized by difficulty in phoneme-grapheme decoding and in perceiving similar pairs of similar phonemes. The aim of this study was to characterize the performance of dyslexic children in auditory and phonological awareness skills and correlate them on this population. A number of 20 children attending 2nd to 4th grades divided into GI: formed by 10 children with interdisciplinary diagnosis of dyslexia, both genders and aged 8 to 12 years old and GII: formed by 10 good readers, paired according to gender and age with GI. As procedure applied hearing evaluation, auditory processing evaluation and phonological awareness were used. The results revealed statistic significant difference between auditory skills of sequential memory for verbal sounds, speech intelligibility with ipsilateral and contralateral competitive message, dichotic of digits test, and staggered spondaic word test when the GI was compared to GII. The same occurred with the subtests of synthesis, segmentation, manipulation and transposition. The findings of this study evidenced correlation between hearing memory tests, syllabic and phonemic manipulation and association between hearing and phonologic abilities, suggesting that the hearing processes interfere directly in the acoustic aspects perception, temporal and sequential of the sounds for the formation of a stable phonologic representation. La dislexia del desarrollo, dificultad específica de lectura, se caracteriza por la dificultad en realizar la decodificación fono-grafema y percepción de fonemas acústicamente semejantes. Este estudio tuvo como objetivo caracterizar el desempeño de niños con dislexia en relación a las habilidades auditivas y de consCiência fonológica, correlacionándolas. Participaron de este estudio niños con dislexia y con buen desempeño escolar, sometidas a evaluaciones audio-lógicas, de procesamiento auditivo y de las habilidades fonológicas. Los resultados indicaron diferencia estadísticamente significativa entre las habilidades auditivas de secuencia para sonidos verbales, mensaje competitiva ipsi y contra lateral, dicótico de dígitos y disílabos alternados, y todavía, en los sub-testes de síntesis, segmentación, manipulación y transposición. Los hallazgos de este estudio muestran correlación entre pruebas de memoria auditiva y manipulación silábica y fonética y asociación entre habilidades auditivas y fonológicas, sugiriendo que los procesos auditivos interfieren directamente en la percepción de aspectos acústicos, temporales y secuenciales de los sonidos para formación de una representación fonológica estable. Universidade Estadual Paulista Universidade Estadual Paulista

Dyslexia is a congenital disorder characterized by unexpected difficulties in learning to read and spell in relation to one's verbal intelligence, motivation, and educational opportunities (Aylward et al., 2003; Morgan, 1896). Because dyslexia can affect 1.5–5% of the population (Aylward et al., 2003; Vellutino et al., 1996), understanding how to identify and instruct students with dyslexia is vital. Unfortunately, many of the articles and studies on this disorder are published in journals teachers rarely read. The purpose of this article is to provide a concise description of dyslexia and recent brain-based research that supports specific instructional implications.

The central tenet of the magnocellular deficit theory of dyslexia is that dyslexia is caused by a magnocellular deficit. A number of investigators have found deficiencies in visual coherent motion perception among dyslexic readers. These deficiencies have been attributed to magnocellular deficits, which means that they directly reflect the cause of dyslexia. However, similar perceptual deficiencies have been found in association with autism, Williams's syndrome, hemiplegia, and schizophrenia. These findings appear to undermine at least one of the following claims: (1) that a magnocellular deficit is the cause of dyslexia, and (2) that coherent motion is a reliable test of magnocellular sensitivity.

Developmental dyslexia is often characterized by a visual deficit, but the nature of this impairment and how it relates to reading ability is disputed (Brain 2003; 126: 841-865). In order to investigate this issue, we compared groups of adults with and without dyslexia on the Ternus, visual-search and symbols tasks. Dyslexic readers yielded more errors on the visual-search and symbols tasks compared with non-dyslexic readers. A positive correlation between visual-search and symbols task performance suggests a common mechanism shared by these tasks. Performance on the visual-search and symbols tasks also correlated with non-word reading and rapid automatized naming measures, and visual search contributed independent variance to non-word reading. The Ternus task did not discriminate reading groups nor contributed significant variance to reading measures. We consider how visual-attention processes might underlie specific component reading measures.

Extraordinary progress in functional brain imaging, primarily advances in functional magnetic resonance imaging, now allows scientists to understand the neural systems serving reading and how these systems differ in dyslexic readers. Scientists now speak of the neural signature of dyslexia, a singular achievement that for the first time has made what was previously a hidden disability, now visible. Paralleling this achievement in understanding the neurobiology of dyslexia, progress in the identification and treatment of dyslexia now offers the hope of identifying children at risk for dyslexia at a very young age and providing evidence-based, effective interventions. Despite these advances, for many dyslexic readers, becoming a skilled, automatic reader remains elusive, in great part because though children with dyslexia can be taught to decode words, teaching children to read fluently and automatically represents the next frontier in research on dyslexia. We suggest that to break through this “fluency” barrier, investigators will need to reexamine the more than 20-year-old central dogma in reading research: the generation of the phonological code from print is modular, that is, automatic and not attention demanding, and not requiring any other cognitive process. Recent findings now present a competing view: other cognitive processes are involved in reading, particularly attentional mechanisms, and that disruption of these attentional mechanisms play a causal role in reading difficulties. Recognition of the role of attentional mechanisms in reading now offer potentially new strategies for interventions in dyslexia. In particular, the use of pharmacotherapeutic agents affecting attentional mechanisms not only may provide a window into the neurochemical mechanisms underlying dyslexia but also may offer a potential adjunct treatment for teaching dyslexic readers to read fluently and automatically. Preliminary studies suggest that agents traditionally used to treat disorders of attention, particularly attention-deficit/hyperactivity disorder, may prove to be an effective adjunct to improving reading in dyslexic students.

This study was designed to explore the double-deficit hypothesis (DDH) of developmental dyslexia in a sample of 133 Spanish children between the ages of 7 and 12 years. Four groups were formed on the basis of their performance in phonemic awareness and rapid automatized naming (RAN): (1) one group with low performance in naming speed (NS), but average in phonological awareness (PA; naming deficit subtype); (2) a second group with low performance in PA, but normal in NS (phonological deficit subtype); (3) a third group with low performance in both variables (doubledeficit subtype); and (4) a fourth group with no deficit in PA and NS (control group). The four groups were compared on measures of lexical access (naming word and pseudowords), fluency, orthographic abilities, and reading comprehension. The double-deficit subtype showed the most difficulties with reading, and the presence of deficit in RAN in naming deficit subtype affected measures of fluency but not orthographic abilities. However, fewer differences were noted between single-deficit subgroups. These results are partially consistent with the predictions of the DDH.

This chapter introduces the emerging factors in educational research that have highlighted the performance of bilingual or multilingual children in comparison with English peers. It summarizes theories of dyslexia and their impact on bilingualism, and presents case studies of screening and intervention with bilingual children. It provides the children who are multilingual have an enriched language environment that allows their intellectual development to flourish, despite some initial delays in language learning. Dyslexia is found in all languages including Asian languages such as Chinese and Japanese. The issue of multilingualism according to a recent report is becoming of increasingly higher relevance in the UK, with growing numbers of English as Additional Language (EAL) children in their schools. It has been argued that ethnic minorities are at a disadvantage within the UK education system, but the report indicates that disadvantaged white children with poor language skills are now showing the greatest difficulty in achievement, indexed by their results at GCSE.

Developmental dyslexia is a language-based learning disability characterized by persistent difficulty in learning to read. While an understanding of genetic contributions is emerging, the ways the environment affects brain functioning in children with developmental dyslexia are poorly understood. A relationship between the home literacy environment (HLE) and neural correlates of reading has been identified in typically developing children, yet it remains unclear whether similar effects are observable in children with a genetic predisposition for dyslexia. Understanding environmental contributions is important given that we do not understand why some genetically at-risk children do not develop dyslexia. Here, we investigate for the first time the relationship between HLE and the neural correlates of phonological processing in beginning readers with (FHD+, n = 29) and without (FHD−, n = 21) a family history of developmental dyslexia. We further controlled for socioeconomic status to isolate the neurobiological mechanism by which HLE affects reading development. Group differences revealed stronger correlation of HLE with brain activation in the left inferior/middle frontal and right fusiform gyri in FHD− compared to FHD+ children, suggesting greater impact of HLE on manipulation of phonological codes and recruitment of orthographic representations in typically developing children. In contrast, activation in the right precentral gyrus showed a significantly stronger correlation with HLE in FHD+ compared to FHD− children, suggesting emerging compensatory networks in genetically at-risk children. Overall, our results suggest that genetic predisposition for dyslexia alters contributions of HLE to early reading skills before formal reading instruction, which has important implications for educational practice and intervention models.

In this study, we concurrently investigated 3 possible causes of dyslexia-a phonological deficit, visual stress, and a reduced visual attention span-in a large population of 164 dyslexic and 118 control French children, aged between 8 and 13 years old. We found that most dyslexic children showed a phonological deficit, either in terms of response accuracy (92.1% of the sample), speed (84.8%), or both (79.3%). Deficits in visual attention span, as measured by partial report ability, affected 28.1% of dyslexic participants, all of which also showed a phonological deficit. Visual stress, as measured by subjective reports of visual discomfort, affected 5.5% of dyslexic participants, not more than controls (8.5%). Although phonological variables explained a large amount of variance in literacy skills, visual variables did not explain any additional variance. Finally, children with comorbid phonological and visual deficits did not show more severe reading disability than children with a pure phonological deficit. These results (a) confirm the importance of phonological deficits in dyslexia; (b) suggest that visual attention span may play a role, but a minor one, at least in this population; (c) do not support any involvement of visual stress in dyslexia. Among the factors that may explain some differences with previously published studies, the present sample is characterized by very stringent inclusion criteria, in terms of the severity of reading disability and in terms of exclusion of comorbidities. This may exacerbate the role of phonological deficits to the detriment of other factors playing a role in reading acquisition. (PsycINFO Database Record

Dyslexia (or specific reading disability) is the most common and extensively studied of the learning disabilities, affecting 80% of all individuals identified as learning disabled. Not only is dyslexia the most thoroughly characterized of all learning disabilities but it is historically the oldest. In fact, the first description of dyslexia in children preceded the first mention of “learning disability” by over 60 years; dyslexia was first described in 1896 while the term “learning disability” was not used until 1962! As discussed throughout this chapter, the demonstration of an unexpected difficulty in reading in relation to intelligence is a key hallmark of dyslexia. Dyslexia is an unexpected difficulty in reading that is best and most reliably and clearly demonstrated by performance on a test of intelligence, on the WISC-V, most often observed using the VCI, though the Full Scale IQ may also be useful.

International audience; The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia.

Studies of basic (nonspeech) auditory processing in adults thought to have developmental dyslexia have yielded a variety of data. Yet there has been little consensus regarding the explanatory value of auditory processing in accounting for reading difficulties. Recently, however, a number of studies of basic auditory processing in children with developmental dyslexia have suggested that a reduced ability to discriminate the rate of change in amplitude envelope onsets (rise time) may be linked to phonological processing difficulties and thereby to reading difficulties. Here, we select a range of different rise-time tasks used with children, and give them to adults with developmental dyslexia, along with 2 other auditory tasks (intensity discrimination and temporal order judgment). Deficits in both rise-time perception and temporal order judgment were found to predict literacy attainment in adults with developmental dyslexia, but the data were suggestive of different causal pathways.

はじめに, 発達性dyslexiaの定義, 評価と診断方法, 背景となる認知障害説, 生物学的障害仮説について概観した.次に日本語での発達性dyslexiaの認知障害構造に関して, 理論面から, および実際の症例や大規模集団における横断的研究から考察した.その結果, 英語圏で主に考えられている音韻障害仮説は日本語での発達性dyslexiaの背景となる認知障害としては必ずしも当てはまらず, 音韻障害に加えて視覚情報処理過程の障害の強い関与があることが示唆された.

The aim of this study was to establish cognitive profiles of dyslexic adults on tests developed within the three main theories of developmental dyslexia: phonological, visual magnocellular and cerebellar and to investigate which theory can account for these profiles. The sample consisted of 15 Polish university students or alumni with a formal diagnosis of dyslexia, without ADHD and 15 controls matched on education, age, gender, IQ and handedness. The results revealed a striking heterogeneity of profiles. Nine dyslexics exhibited only a phonological deficit; one a phonological and a visual magnocellular deficit; a further three a phonological and a cerebellar deficit; two either a cerebellar or a visual magnocellular deficit. None of the three main theories of dyslexia can account for all the cases studied here. It is suggested that the best account of these data is in terms of different sub-types of dyslexia with different underlying causes, such as phonological, visual magnocellular and cerebellar, or a combination of these. However, an account in terms of Ramus' (Trends, Neurosci. 2004; 27(12): 720-726) model, according to which the phonological deficit is a core deficit in dyslexia and other deficits (magnocellular and cerebellar), are just co-morbid markers without a causal relationship to dyslexics' literacy difficulties, cannot currently be ruled out.

The aim of this study was to see whether patterns of neuro-cognitive assets and deficits seen in dyslexia also would lead to different patterns of reading and writing. A group of dyslexic children was subgrouped by language comprehension and mathematics skills in accordance with the definition of the British Dyslexia Association of 1998. This yielded three subgroups that showed three distinct neuro-cognitive profiles depicted within the Multi-Component Model of Working Memory. The participants were tested with single word reading and spelling tasks. The scores varied only to a minor degree between the subgroups. The results were discussed in view of developmental phases into literacy. Only one subgroup could be defined within the orthographic phase, while the other two were within the alphabetic phase. Thus, patterns at the neuro-cognitive level seen in the subgroups were to a limited degree reflected at the behavioural level. The results were also discussed in view of different orthographies. Since using information from phonological testing only, as currently appears to be common practice in many contexts, may result in intervention with little effect for some dyslexics, it was concluded that assessing neuro-cognitive assets and deficits targeting dyslexia is essential to intervention and the understanding of dyslexia. Copyright © 2006 John Wiley & Sons, Ltd.

Phonology has been a central concept in the scientific study of dyslexia over the past decades. Despite its central position, however, it is a concept with no precise definition or status. The present article investigates the notion of 'phonology' in the tradition of cognitive psychology. An attempt is made to characterize the basic assumptions of the phonological approach to dyslexia and to evaluate these assumptions on the basis of commonly accepted standards of empirical science. First, the core assumptions of phonological awareness are outlined and discussed. Second, the position of Paula Tallal is presented and discussed in order to shed light on an attempt to stretch the cognitive-psychological notion of 'phonology' towards auditory and perceptual aspects. Both the core assumptions and Tallal's position are rejected as unfortunate, albeit for different reasons. Third, the outcome of this discussion is a search for what is referred to as a 'vulnerable theory' within this field. The present article claims that phonological descriptions must be based on observable linguistic behaviour, so that hypotheses can be falsified by data. Consequently, definitions of 'dyslexia' must be based on symptoms; causal aspects should not be included. In fact, we claim that causal aspects, such as 'phonological deficit', both exclude other causal hypotheses and lead to circular reasoning. If we are to use terms such as 'phonology' and 'phoneme' in dyslexia research, we must have more precise operationalizations of them.

Working memory impairments in dyslexia are well documented. However, research has mostly been limited to the phonological domain, a modality in which people with dyslexia have a range of problems. In this paper, 22 adult students with dyslexia and 22 age- and IQ-matched controls were presented with both verbal and visuospatial working memory tasks. Performance was compared on measures of simple span, complex span (requiring both storage and processing), and dynamic memory updating in the two domains. The dyslexic group had significantly lower spans than the controls on all the verbal tasks, both simple and complex, and also on the spatial complex span measure. Impairments remained on the complex span measures after controlling statistically for simple span performance, suggesting a central executive impairment in dyslexia. The novelty of task demands on the initial trials of the spatial updating task also proved more problematic for the dyslexic than control participants. The results are interpreted in terms of extant theories of dyslexia. The possibility of a supervisory attentional system deficit in dyslexia is also raised. It seems clear that working memory difficulties in dyslexia extend into adulthood, can affect performance in both the phonological and visuospatial modalities, and implicate central executive dysfunction, in addition to problems with storage.

Extant neurobiological theories of dyslexia appear fractional in focusing on isolated brain regions, mechanisms, and functional pathways. A synthesis of current research shows support for an Interactive Specialization (IS) model of dyslexia involving the dysfunctional orchestration of a widely-distributed, attentionally-controlled, hierarchical, and interhemispheric circuit of intercommunicating neuronal networks. This circuitry is comprised principally of the frontostriatal-parietal cognitive control system of networks, the posterior corpus callosum, and the left arcuate fasciculus. During development, the coalescence of these functionally specialized regions, acting together, may be essential to preventing the core phonemic and phonological processing deficits defining the dyslexic phenotype. Research demonstrating an association of each with processing phonology presents the foundational outline for a comprehensive, integrative theory of dyslexia and suggests the importance of inclusive remedial efforts aimed at promoting interactions among all three networking territories.

A developmental disorder of language is a significant delay or impairment in the expression and/or comprehension of language in the absence of a known cause. Keywords: language; development; dyslexia; dysphasia; SLI

Developmental dyslexia is commonly thought to arise from specific phonological impairments. However, recent evidence is consistent with the possibility that phonological impairments arise as symptoms of an underlying dysfunction of procedural learning. The nature of the link between impaired procedural learning and phonological dysfunction is unresolved. Motivated by the observation that speech processing involves the acquisition of procedural category knowledge, the present study investigates the possibility that procedural learning impairment may affect phonological processing by interfering with the typical course of phonetic category learning. The present study tests this hypothesis while controlling for linguistic experience and possible speech-specific deficits by comparing auditory category learning across artificial, nonlinguistic sounds among dyslexic adults and matched controls in a specialized first-person shooter videogame that has been shown to engage procedural learning. Nonspeech auditory category learning was assessed online via within-game measures and also with a post-training task involving overt categorization of familiar and novel sound exemplars. Each measure reveals that dyslexic participants do not acquire procedural category knowledge as effectively as age- and cognitive-ability matched controls. This difference cannot be explained by differences in perceptual acuity for the sounds. Moreover, poor nonspeech category learning is associated with slower phonological processing. Whereas phonological processing impairments have been emphasized as the cause of dyslexia, the current results suggest that impaired auditory category learning, general in nature and not specific to speech signals, could contribute to phonological deficits in dyslexia with subsequent negative effects on language acquisition and reading. Implications for the neuro-cognitive mechanisms of developmental dyslexia are discussed.

The hallmark of developmental surface dyslexia in English and French is inaccurate reading of words with atypical spelling-sound correspondences. According to Douklias, Masterson and Hanley (2009), surface dyslexia can also be observed in Greek (a transparent orthography for reading that does not contain words of this kind). Their findings suggested that surface dyslexia in Greek can be characterized by slow reading of familiar words, and by inaccurate spelling of words with atypical sound-spelling correspondences (Greek is less transparent for spelling than for reading). In this study, we report seven adult cases whose slow reading and impaired spelling accuracy satisfied these criteria for Greek surface dyslexia. When asked to read words with atypical grapheme-phoneme correspondences in English (their second language), their accuracy was severely impaired. A co-occurrence was also observed between impaired spelling of words with atypical phoneme-grapheme correspondences in English and Greek. These co-occurrences provide strong evidence that surface dyslexia genuinely exists in Greek and that slow reading of real words in Greek reflects the same underlying impairment as that which produces inaccurate reading of atypical words in English. Two further individuals were observed with impaired reading and spelling of nonwords in both languages, consistent with developmental phonological dyslexia. Neither of the phonological dyslexics read words slowly. In terms of computational models of reading aloud, these findings suggest that slow reading by dyslexics in transparent orthographies is the consequence of a developmental impairment of the lexical (Coltheart, Rastle, Perry, Langdon, & Zeigler, 2001; Perry, Ziegler, & Zorzi, 2010) or semantic reading route (Plaut, McClelland, Seidenberg, & Patterson, 1996). This outcome provides evidence that the neurophysiological substrate(s) that support the lexical/semantic and the phonological pathways that are involved in reading and spelling are the same in both Greek and English.