Littérature scientifique sur le sujet « Dyslexia (DD) »

Despite proving its usefulness for over a century, the concept of developmental dyslexia (DD) is currently in severe disarray because of the recent introduction of the phonological theory of its causation. Since mastering the phonological principle is essential for all reading, failure to do so cannot be used to distinguish DD from the many other causes of such failure. To overcome this problem, many new psychological, signal detection, and neurological theories have been introduced recently. All these new theories converge on the idea that DD is fundamentally caused by impaired signalling of the timing of the visual and auditory cues that are essential for reading. These are provided by large ‘magnocellular’ neurones which respond rapidly to sensory transients. The evidence for this conclusion is overwhelming. Especially convincing are intervention studies that have shown that improving magnocellular function improves dyslexic children’s reading, together with cohort studies that have demonstrated that the magnocellular timing deficit is present in infants who later become dyslexic, long before they begin learning to read. The converse of the magnocellular deficit in dyslexics may be that they gain parvocellular abundance. This may often impart the exceptional ‘holistic’ talents that have been ascribed to them and that society needs to nurture.

Background: Doublecortin domain-containing 2 (DCDC2) is a doublecortin domain-containing gene family member and the doublecortin domain has been demonstrated to bind to tubulin and enhance microtubule polymerization. It has been associated with developmental dyslexia and this protein family member is thought to function in neuronal migration where it may affect the signaling of primary cilia. Objectives: The objective of the study is to find out if there is any association of genetic variants of DCDC2 with developmental dyslexia in Chinese children from Hong Kong. Methods: The dyslexic children were diagnosed as developmental dyslexia (DD) using the Hong Kong Test of Specific Learning Difficulties in Reading and Writing (HKT-SpLD) by the Department of Health, Hong Kong. Saliva specimens were collected and their genotypes of DCDC2 were studied by DNA sequencing or TaqMan Real Time PCR Assays. Results: The most significant marker is rs6940827 which is associated with DD with nominal p-value (0.011). However, this marker did not remain significant after multiple testing corrections and the adjusted p-value from permutation test was 0.1329. Using sliding window haplotype analysis, several haplotypes were found to be nominally associated with DD. The smallest nominal p values was 0.0036 (rs2996452-rs1318700, C-A). However, none of the p values could withstand the multiple testing corrections. Conclusion: Despite early findings that DCDC2 is a strong candidate for developmental dyslexia and that some of the genetic variants have been linked to brain structure and functions, our findings showed that DCDC2 is not strongly associated with dyslexia.

AbstractAn accumulating body of evidence highlights the contribution of general cognitive processes, such as attention, to language-related skills.Objective:The purpose of the present study was to explore how interference control (a subcomponent of selective attention) is affected in developmental dyslexia (DD) by means of control over simple stimulus-response mappings. Furthermore, we aimed to examine interference control in adults with DD across sensory modalities.Methods:The performance of 14 dyslexic adults and 14 matched controls was compared on visual/auditory Simon tasks, in which conflict was presented in terms of an incongruent mapping between the location of a visual/auditory stimulus and the appropriate motor response.Results:In the auditory task, dyslexic participants exhibited larger Simon effect costs; namely, they showed disproportionately larger reaction times (RTs)/errors costs when the auditory stimulus and response were incongruent relative to RT/errors costs of non-impaired readers. In the visual Simon task, both groups presented Simon effect costs to the same extent.Conclusion:These results indicate that the ability to control auditory selective attention is carried out less effectively in those with DD compared with visually controlled processing. The implications of this impaired process for the language-related skills of individuals with DD are discussed.

Developmental dyslexia (DD) is a multifactorial, specific learning disorder. Susceptibility genes have been identified, but there is growing evidence that environmental factors, and especially stress, may act as triggering factors that determine an individual’s risk of developing DD. In DD, as in most complex phenotypes, the presence of a genetic mutation fails to explain the broad phenotypic spectrum observed. Early life stress has been repeatedly associated with the risk of multifactorial disorders, due to its effects on chromatin regulation, gene expression, HPA axis function and its long-term effects on the systemic stress response. Based on recent evidence, we discuss the potential role of stress on DD occurrence, its putative epigenetic effects on the HPA axis of affected individuals, as well as the necessity of early and appropriate intervention, based on the individual stress-associated (endo)phenotype.

Purpose Developmental dyslexia (DD) is commonly thought to arise from phonological impairments. However, an emerging perspective is that a more general procedural learning deficit, not specific to phonological processing, may underlie DD. The current study examined if individuals with DD are capable of extracting statistical regularities across sequences of passively experienced speech and nonspeech sounds. Such statistical learning is believed to be domain-general, to draw upon procedural learning systems, and to relate to language outcomes. Method DD and control groups were familiarized with a continuous stream of syllables or sine-wave tones, the ordering of which was defined by high or low transitional probabilities across adjacent stimulus pairs. Participants subsequently judged two 3-stimulus test items with either high or low statistical coherence as being the most similar to the sounds heard during familiarization. Results As with control participants, the DD group was sensitive to the transitional probability structure of the familiarization materials as evidenced by above-chance performance. However, the performance of participants with DD was significantly poorer than controls across linguistic and nonlinguistic stimuli. In addition, reading-related measures were significantly correlated with statistical learning performance of both speech and nonspeech material. Conclusion Results are discussed in light of procedural learning impairments among participants with DD.

Objectives: Korean developmental dyslexic upper grade children’s text comprehension abilities were investigated considering the mode of texts (reading vs listening) as well as the type of texts (narrative vs expository).Methods: Sixteen 5th to 6th graders with developmental dyslexia (DD) and grade and cognition-matched typically developing children (TD) participated in 4 text comprehension tasks. Each child responded to 32 questions, 8 in each text, tapping comprehension of texts counterbalancing the effect of mode and type of texts.Results: First, children with DD performed lower than TD children in text comprehension, reflecting developmental dyslexic Korean children’s performance cross linguistically even with the high orthographic transparency of Hangeul. Second, children with DD performed better in the mode of reading compared to the mode of listening, which was the same as the TD children. Third, the effect of type of text was meaningful to only children with DD, while TD children’s performance between narrative and expository text was not different.Conclusion: Korean upper grade children with DD seemed to rely heavily on the mode of reading in comprehending texts similarly to their grade-matched children, while children with DD had greater difficulties in comprehending the expository texts both in reading and listening modes compared to the narrative texts. Each child with DD’s developmental level of the type and mode of texts needs to be considered to support his/her text comprehension abilities. Further studies need to be extended to the Korean language considering the type of texts with the DIER model.

This study investigated which components of the writing production process are impaired in Spanish children with developmental dyslexia (DD) aged 8 to 12 years. Children with and without dyslexia ( n = 60) were assessed in their use of the lexical and the sublexical routes of spelling as well as the orthographic working memory system by manipulating lexical frequency, phonology-to-orthography (P-O) consistency, and word length in a copying task and a spelling-to-dictation task. Results revealed that children with dyslexia produced longer written latencies than chronological age-matched (CA) controls, more errors than CA and reading age-matched (RA) controls, and writing durations similar to CA controls. Latencies were more affected by frequency, consistency, and length in the DD group and the RA group than in CA controls. Children in the DD and RA groups produced longer written latencies in the copying than in the spelling-to-dictation task, while controls in the CA group were not affected by the task. Results indicate that spelling impairments in Spanish children with dyslexia affect the relative involvement of lexical and sublexical information during handwriting. Meanwhile, effects on writing speed seem to be related to deficits in reading ability, and accuracy scores seem to be poorer than expected by children’s reading skill.

ABSTRACTIn the light of the literature describing oral language difficulties in developmental dyslexia (DD), event-related potentials were used in order to compare morphosyntactic processing in 16 adults with DD (aged 20–28 years) and unimpaired controls. Sentences including subject–verb agreement violations were presented auditorily, with grammaticality and subject number as main factors. Electrophysiological data revealed differences between groups concerning both the latency of the P600 component and the additional presence in the DD group of a negativity broadly diffused all over the scalp. Moreover, these electrophysiological anomalies increased when plural sentences were processed. On the whole, the results support the hypothesis of a linguistic deficit and of different language processing modalities in DD participants.

ObjectivesOur study aimed to compare the quality of life (QoL) between Chinese developmental dyslexia (DD) and healthy children.DesignA cross-sectional study.SettingThe participants were recruited from grades 3–6 in six primary schools in Tianmen, a city of Hubei Province, China.ParticipantsA total of 5679 students were recruited. After excluding children with visual and auditory dysfunction or psychiatric diseases or with a response rate on the scales or questionnaires of less than 90%, 5352 children were finally included in the analysis. DD children were diagnosed according to their clinical symptoms, which were mainly assessed by the Dyslexia Checklist for Chinese Children and the Pupil Rating Scale Revised Screening for Learning Disabilities.Outcome measuresThe QoL for DD and healthy children was appraised by the Quality of Life Scale for Children and Adolescents (QLSCA). Outcome measures included its four domain scores (psychosocial function, physiological and mental health, living environment and satisfaction with QoL) and total score.ResultsA total of 186 children were diagnosed with DD. The distribution of DD children in five levels of QoL was statistically different from that of healthy children (χ2=57.63, p<0.001). Compared with healthy children, the proportion of poor or worse QoL in DD was higher, and the proportion of moderate, better or good QoL was lower. The total QLSCA score in DD children was 3.475 lower than that in healthy children (B=−3.475, p=0.006). Psychosocial function, physiological and mental health, living environment and satisfaction with QoL of DD children were also inferior to those of healthy children.ConclusionThe QoL of DD was significantly lower than that of healthy children, prompting more public efforts to improve DD QoL.

It is a widely held belief that developmental dyslexia (DD) is a phonological disorder in which readers have difficulty associating graphemes with their corresponding phonemes. In contrast, the magnocellular theory of dyslexia assumes that DD is a visual disorder caused by dysfunctional magnocellular neural pathways. The review explores arguments for and against these theories. Recent results have shown that DD is caused by (1) a reduced ability to simultaneously recognize sequences of letters that make up words, (2) longer fixation times required to simultaneously recognize strings of letters, and (3) amplitudes of saccades that do not match the number of simultaneously recognized letters. It was shown that pseudowords that could not be recognized simultaneously were recognized almost without errors when the fixation time was extended. However, there is an individual maximum number of letters that each reader with DD can recognize simultaneously. Findings on the neurobiological basis of temporal summation have shown that a necessary prolongation of fixation times is due to impaired processing mechanisms of the visual system, presumably involving magnocells and parvocells. An area in the mid-fusiform gyrus also appears to play a significant role in the ability to simultaneously recognize words and pseudowords. The results also contradict the assumption that DD is due to a lack of eye movement control. The present research does not support the assumption that DD is caused by a phonological disorder but shows that DD is due to a visual processing dysfunction.

The present thesis faces the ongoing debate on the linguistic nature of Developmental Dyslexia (DD), based on evidence of grammatical deficits in dyslexic individuals (e.g., Robertson & Joanisse, 2010), and on the frequently reported overlap with Specific Language Impairment (e.g., Bishop & Snowling, 2004). In particular, the morphosyntactic processing deficit in DD has been explored by means of particularly sensitive measures, namely event-related potentials (ERPs). The dissertation collects the results from three studies performed on different samples of individuals with DD (Italian adults, Italian children, and German adults), reporting consistent data in support of a general morphosyntactic processing weakness. Specifically, the ERP results reveal different language processing modalities in the dyslexic samples, characterised by the need of an additional process related to rules retrieval and/or lexical access. Further behavioural data collected on the same participants support the ERP data. In the third study, advantage has been taken of the morphological features characterising German to additionally investigate the specificity of the reported morphosyntactic deficits, and their relationship with phonological and acoustical processing difficulties. The results are discussed within a developmental and psycholinguistic framework.

Considerando la rilevanza e complessità della valutazione del linguaggio e della lettura nei bambini bilingui, il presente lavoro raccomanda di valutare il linguaggio nella prima e nella seconda lingua e l’utilizzo di tecnologie innovative. Ricerche precedenti hanno indagato, in varie lingue, l'adeguatezza di prove che valutano il linguaggio utilizzando marcatori clinici lingua-specifici, e la lettura nella popolazione bilingue. Alcune di queste prove sono state implementate in forma computerizzata per la somministrazione e la valutazione automatizzate. Spesso queste prove computerizzati di screening sono limitate alle caratteristiche definite dagli sviluppatori e non possono essere adattate per un utilizzo in scuola o clinica. Il presente elaborato include una revisione della letteratura scientifica relativa agli strumenti di screening del linguaggio e della lettura e sei studi empirici riguardanti la costruzione, la somministrazione, la validità e l'utilità di screening computerizzati di linguaggio e lettura nei bambini bilingui. Il primo studio riguarda i metodi con cui i logopedisti valutano i bambini bilingui. Attraverso un questionario compilato da 300 logopedisti è stato indagato se loro considerano la valutazione di tutte le lingue parlate rilevante e realizzabile attraverso dei compiti computerizzati. I risultati suggeriscono uno squilibrio tra conoscenze delle prassi raccomandate e la loro effettiva applicazione. I logopedisti si dichiarano aperti alla possibilità di utilizzare delle procedure computerizzate. Il secondo studio indaga il potenziale della valutazione della lettura in entrambe le lingue attraverso procedure computerizzate. Confrontando le prestazioni di 33 bambini, parlanti mandarino-italiano e frequentando la terza e quarta elementare in Italia, in test standardizzati di lettura in italiano con quelle conseguite in compiti di screening computerizzati, implementati con E-Prime 3.0, somministrati in presenza, emerge che i test computerizzati valutano in modo affidabile le competenze di lettura nei parlanti di italiano L2. Il terzo, quarto, quinto e sesto studio indagano il potenziale della piattaforma di screening modificabile MuLiMi, creata per questo lavoro di tesi, nell'identificare il rischio di Disturbo Primario del Linguaggio e di Dislessia Evolutiva in bambini bilingui. Questi studi includono cinque gruppi linguistici, due fasce di età, due target di studio e 109 bambini e confermano che è possibile valutare le competenze di linguaggio e lettura in entrambe le lingue attraverso la procedura di screening implementata sulla web app MuLiMi. Altri risultati suggeriscono un vantaggio di paradigmi come “Chi lo dice giusto?” rispetto ai giudizi di correttezza nelle prove morfosintattiche e di consapevolezza fonologica, e la potenziale differenza nel contribuire all'identificazione del rischio da parte di diverse sottocategorie di item, per esempio comprensione di verbi vs. nomi e nonparole lingua-specifiche vs. non lingua-specifiche. Il sesto studio indaga l'usabilità di MuLiMi analizzando le impressioni degli esaminatori e dei bambini valutati. I risultati suggeriscono che entrambi i gruppi trovano l’uso della piattaforma facile, anche utilizzata a distanza. Alcune delle risposte indicano la necessità di migliorare la velocità del sistema. In conclusione, i risultati riguardano la possibilità di utilizzare compiti somministrati e corretti in modo automatico per l'individuazione dei soggetti bilingui a rischio per disturbi di linguaggio e di lettura, rispettando i requisiti di affidabilità e validità delle prove e consentendo una valutazione valutata come facile, utile e piacevole. L'utilizzo di MuLiMi sembra soddisfare i requisiti relativi alla valutazione del linguaggio e della lettura nei bilingui, consentendo il confronto tra le competenze in entrambe le lingue, e favorendo negli esaminatori un processo decisionale consapevole per la diagnosi e l’intervento.
In line with relevance and complexity of language and reading assessment in bilingual children, this work incorporates recommended language assessment of bilingual children’s first as well as their second language and making use of innovative technologies. Previous research relates to the suitability of tasks assessing language with language-specific clinical markers, and reading skills in the bilingual population across languages. Some of these tasks have been implemented as computerized tasks allowing for automatic administration and evaluation. However, these computerized tasks are restricted to the characteristics defined by developers and cannot be adapted for use in school or clinical settings. This manuscript includes a review of the scientific literature concerning language and reading screening approaches and six empirical studies on the construction, administration, suitability and useful-ness of computerized bilingual language and reading screenings. The first study concerns how Speech and Language Therapists assess bilingual children. In a survey with 300 Speech and Language Therapists it was investigated how far Speech and Language Therapists consider assessment of both languages spoken relevant and realizable with computerized screening tasks. Results suggest an imbalance between the knowledge of the specific requirements for assessment of multilingual children and their application at work. Speech and Language Therapists also indicated open-ness towards computerized solutions. The second study investigates the potential of reading assessment in both languages through automatic task administration and evaluation. The performance in standardized Italian reading tests of 33 Mandarin-speaking children living in Italy, attending grades 3 and 4 in primary school, is compared to task performance in computerized screening tasks, implemented on E-Prime 3.0, administered in presence of the examiner. Results suggest that computerized reading and language tests reliably assess reading performance in L2 speakers of Italian. The third, fourth, fifth and sixth study investigate the potential of the modifiable screening platform MuLiMi, created for this dissertation, in the risk identification of Developmental Language Disorders and Developmental Dyslexia risk in bilingual children. These studies covering five language groups, two age ranges and two different screening purposes, testing 109 child participants indicate that it is possible to automatically assess language and reading skills in both languages with the screenings implemented on the MuLiMi web app. Further interesting findings suggest an advantage of paradigms such as “Who says it right?” over judgement tasks for screening tasks on morphosyntactic processing and phonological awareness as well as to the potential difference in contribution to risk identification between different item subcategories, e.g. verbs vs. noun comprehension and language-specific vs. non-language-specific nonwords. In addition to that, study six assesses the usability of this screening platform as perceived by the examiners administrating the screenings and by the children. The results generally suggest user-friendliness and ease in use even when administering these screenings remotely. Some of the information obtained indicate the need of improvement concerning the system speed. In summary, findings concern the possibility of using fully automatically administered and scored tasks for the identification of bilingual children at risk for language or reading disorders, meeting the requirements concerning reliability and validity of the tests and allowing an assessment perceived as easy, useful and pleasant. The application of the screening platform MuLiMi appears to meet the requirements concerning bilingual language and reading assessment, allowing for the comparison of both languages as well as conscious decision-making for diagnoses and intervention need.

Plusieurs études ont récemment fait l'hypothèse qu'un déficit de l'apprentissage procédural commun aux troubles neurodéveloppementaux pouvait permettre d'expliquer leur fréquente association (Nicolson et Fawcett, 2007). Tout spécialement, les circuits neuronaux impliqués dans cet apprentissage (les boucles cortico-striatale, CS et cortico-cérébelleuse, CC) pouvaient rendre compte avec pertinence de la comorbidité fréquente entre Dyslexie Développementale (DD) et Trouble de l'Acquisition de la Coordination (TAC) : 40 à 60% des enfants présentent en effet la double association. Les circuits neuronaux qui soutiennent l'apprentissage d'une séquence motrice et en particulier d'une tâche de tapping de doigts (FTT, Finger Tapping Task) sont bien connus et modélisés (Doyon, Bellec, Amsel, Penhune, Monchi, Carrier et al., 2009) et concernent tout particulièrement ces deux boucles CS et CC. Nous avons donc choisi dans cette thèse d'observer les modifications cérébrales lors de l'apprentissage d'une FTT, chez des enfants âgés de 8 à 12 ans présentant une DD, un TAC ou l'association des deux troubles. Dans un premier temps, nous avons effectué une analyse des données issues des tests neurospychologiques de l'ensemble des enfants de l'étude (20 DD, 22 TAC et 23 DysTAC). Nos résultats ne montrent pas de différences entre les trois groupes aux tests attentionnels, comportementaux et psychosociaux. Nous trouvons des différences aux subtests du WISC-IV en rapport avec les capacités visuospatiales et motrices (Cubes, Symboles, Indice de Vitesse de Traitement) où le groupe DD se montre plus performant que le groupe TAC. Aucune différence n'est retrouvée entre le groupe comorbide et les deux autres groupes, suggérant d'une part un profil cognitif partagé et commun aux troubles neurodéveloppementaux et d'autre part le caractère non cumulatif de l'association des deux troubles. Dans un second temps, nous avons analysé les données issues de l'imagerie fonctionnelle par résonnance magnétique (IRMf) des 48 enfants ayant effectués la partie IRM (16 DD, 16 TAC et 16 DysTAC) afin d'explorer les activités cérébrales lors de la réalisation d'une FTT à deux stades de l'apprentissage (début d'apprentissage et stade automatique après quinze jours d'entraînement). Nos résultats indiquent que les trois groupes d'enfants ont été capable d'accéder à l'automatisation de la FTT après un entraînement approprié, mais en utilisant des processus cérébraux compensatoires différents entre les groupes. Nos résultats ne confirment pas les hypothèses et le modèle théorique de Nicolson, postulant des déficits spécialisés des boucles CS ou CC en fonction des troubles. Par contre, nos résultats mettent très nettement en évidence des mécanismes cérébraux spécifiques aux enfants TAC. Ces derniers présentent en effet une suractivation des aires attentionnelles et un recrutement de zones cérébrales plus important lors de performances similaires à celles des autres enfants. En dernier lieu, nos données indiquent que les groupes DD et DysTAC présentent un profil commun, tant dans les résultats neuropsychologiques que dans les résultats d'imagerie, alors que le groupe TAC est clairement singulier dans son fonctionnement
Many studies have pointed out the high frequency of co-morbid associations in neurodevelopmental disorders. However, few of them have given details of cognitive functions in developmental dyslexia (DD) and developmental coordination disorder (DCD) children and still fewer on the association of DD and DCD. The main purpose of this article is to compare the intellectual characteristics of the 3 populations and, in particular, to investigate the cognitive profiles of children with co-occurrence. Recent theories consider that procedural learning may support frequent overlap between neurodevelopemental disorders. In particular, the brain networks involved in this learning (cortico-striatal (CS) and cortico-cerebellar (CC) loops) could account for frequent co-morbidity between DCD and DD (about 40 to 60% of DD and DCD subjects suffer from both disorders). The aim of our study was to investigate cerebral changes due to the motor sequence learning process, especially the finger-tapping task (FTT), from acquisition through automatization, in children with DD, DCD, or DD and DCD. The neural circuitry supporting this action is well-known and well-modelled (Doyon et al., 2009), and includes, among others, CC and CS loops. Functional magnetic resonance imaging (fMRI) in 48 children (8-12 years old) with neurodevelopmental disorders (16 DD, 16 DCD and 16 DD+DCD) explored their brain activity during FTT, performed either after 2 weeks of training or in the early stage of learning. First, we analyzed the results in all participants (22 DCD, 20 DD and 23 DD+DCD) in tests assessing cognitive (WISC-IV), attentional (CPT-II) and behavioural (CBCL) abilities. No difference was found between the 3 groups in attention testing (CPT) and behavioural characteristics (CBCL). Significant between-groups differences were observed in Processing Speed Index (PSI) score and the block design and symbol search subtests. Post hoc group comparisons showed that DD fared better than DCD children. No significant differences were found between the co-morbid vs. pure groups: co-morbid association did not cause an accumulation of disorders. Second, our results indicated that all children with DD, DCD or both disorders performed the tasks with good automaticity, but suggested that different compensatory brain processes allowed them to access this automatization stage. Our fMRI results do not appear to confirm Nicolson's model but tend more towards shared disability in CS and CC loops for both DD and DCD, with slight between-group differences in these areas. Moreover, and in agreement with the results of previous fMRI studies in DCD children, our data disclosed increasing evidence that this group needs to invest more brain areas to achieve similar performances. Lastly, it appears that the co-morbid and DD groups are very close in cognitive profile (especially on WISC-IV) and in neural correlates associated with our paradigm, while the DCD group presents specific, distinct and particular characteristics. Our data therefore indicate a promising direction for future research on the neural mechanisms linked with learning in neurodevelopmental disorders and in understanding co-morbidity

Play holds an important and irreplaceable role in children's lives and development as it allows children to learn essential skills varying in nature and difficulty such as reading, arithmetic, and social skills. Children with neurodivergent conditions such as blindness, color vision deficiency (CVD), cortical visual impairment (CVI), and developmental dyslexia (DD) are unable to take advantage of their vision, a vital sense for navigating through the environment designed by and for typically developing (TD) individuals. These children are often not provided with tools and activities sufficient to learn and live at ease along with their peers. When they are in hospitals and other clinical settings, the struggles can be further amplified. This chapter discusses how these conditions affect young children and introduces various playful learning activities and interventions that can assist their social and cognitive development.