Developmental Dyslexia Children Research Articles

Exploring brain plasticity in developmental dyslexia through implicit sequence learning.

Developmental dyslexia (DD) is defined as difficulties in learning to read even with normal intelligence and adequate educational guidance. Deficits in implicit sequence learning (ISL) abilities have been reported in children with DD. We investigated brain plasticity in a group of 17 children with DD, compared with 18 typically developing (TD) children, after two sessions of training on a serial reaction time (SRT) task with a 24-h interval. Our outcome measures for the task were: a sequence-specific implicit learning measure (ISL), entailing implicit recognition and learning of sequential associations; and a general visuomotor skill learning measure (GSL). Gray matter volume (GMV) increased, and white matter volume (WMV) decreased from day 1 to day 2 in cerebellar areas regardless of group. A moderating effect of group was found on the correlation between WMV underlying the left precentral gyrus at day 2 and the change in ISL performance, suggesting the use of different underlying learning mechanisms in DD and TD children during the ISL task. Moreover, DD had larger WMV in the posterior thalamic radiation compared with TD, supporting previous reports of atypical development of this structure in DD. Further studies with larger sample sizes are warranted to validate these results.

Speech disfluencies in children with developmental dyslexia: How do they differ from typical development?

Disfluency is a multifactorial concept that can be linked to several of the language production levels, in both typical and atypical populations. In children, the language system is still developing and few studies have explored disfluency patterns. In typical development (TD), in particular, studies have shown discrepancies according to the language being considered. In neurodevelopmental disorders, such as developmental dyslexia (DD), it is still unclear whether the pattern of disfluency is similar to TD. To analyse the type of disfluency and their evolution in French children aged 8-12 years. Also to compare the pattern of disfluency in DD and TD, and to test whether disfluencies were correlated with reading difficulties. A total of 25 children with DD and 21 children with TD aged 8-12.6 years produced an autobiographical narrative. Seven types of disfluencies were coded: part-word repetitions; repetitions of monosyllabic words; other types of repetitions (words and phrases); filled pauses; revisions-substitutions; revisions-additions; and abandoned utterances. We compared the proportion of each disfluency in DD and TD. Spearman correlations were then performed between disfluencies, reading performance and age. The results showed that both DD and TD children mainly produced filled pauses, repetitions of monosyllabic words and substitutions. Both groups displayed a high rate of disfluency (> 10%). No correlations with age were found. Correlations with reading performance were significant in the TD group only. The study showed that DD is not characterized by a specific pattern of disfluency. Additionally, disfluency rates were similar in children aged 8-12 years. In contrast to other languages, the current study suggests that French-speaking children have a high rate of disfluency. The study also suggests that disfluency should be interpreted with caution in DD, given that TD children also have a high rate of disfluency. Therefore, it seems important to adapt the pathological threshold of disfluency to the language being spoken in order to avoid an overestimation of the prevalence of these deficits in French-speaking children. What is already known on this subject TD children produce a high rate of disfluency, which is also influenced by the language being spoken. No study looked at the effect of DD on disfluency production. Nonetheless, problems in reading comprehension and reduced reading experience may impact lexical development and speech fluency. What this paper adds to the existing knowledge In our study, both groups (French-speaking children) produced a substantial amount of disfluency as compared with other languages (> 10%). Additionally, the pattern of disfluency was similar in TD and DD (namely, filled pauses, prolongations repetitions of monosyllabic words and substitutions). In the DD group, disfluency production was not correlated with reading performance. What are the potential or actual clinical implications of this work? These results indicate that it is crucial to consider the language being spoken when examining disfluency in order to avoid an overestimation of language difficulties in some languages, such as in French. Moreover, the production of disfluencies in DD should not be considered as language dysfunction since the pattern of disfluency what quite similar in TD and DD, and did not correlate with their reading difficulties.

Phonological Awareness and Rapid Automatized Naming: The Mediating Effect of Word Reading and Spelling in Children with Developmental Dyslexia, Attention Deficit Hyperactivity Disorder, and Mild Intellectual Disability

Introduction: In learning to read, children learn to integrate orthographic, phonological, and semantic codes into highly specified and redundant lexical representations. The aim is to test a proposed model for the relationship between phonological awareness (PA) and rapid automatized naming (RAN) as mediated by word reading (WR) and spelling (SP) in children with developmental dyslexia (DD), attention deficit hyperactivity disorder (ADHD), and mild intellectual disability (ID). Methods: The relation between PA and RAN was found to be mediated by WR and SP in children with DD, ADHD, and mild ID. Three groups of children were included: DD children (N = 70), ADHD children (N = 68), and ID children (N = 69). This is a quantitative correlational, cross-sectional study investigating the strength and direction of relationships among proposed variables. Results: The relation between PA and RAN was found to be mediated by WR and SP. Based on their correlation analysis, the researcher concluded that there are significant correlations between PA, RAN, WR, and SP. PA correlates positively with RAN and SP. RAN correlates positively with WR and SP. Conclusion: The study extended our knowledge of the relationship between PA and RAN as mediated by WR and SP in children with DD, ADHD, and mild ID. In practice, this is conducive to promote the utilization of “PA” and “RAN” so as to improve the early literacy skills (WR and SP) among children with DD, ADHD, and mild ID.

Developmental dyslexia, developmental coordination disorder and comorbidity discrimination using multimodal structural and functional neuroimaging

Developmental dyslexia (DD) and developmental coordination disorder (DCD) are two common neurodevelopmental disorders with a high co-occurrence rate. This led several authors to postulate that the two disorders share, at least partially, similar neural underpinning. However, even though several studies examined brain differences between typically developing (TD) children and children with either DD or DCD, no previous study directly compared DD, DCD and children with both disorders (COM) using neuroimaging. We acquired structural and resting-state functional MRI images of 136 children (TD = 42, DD = 45, DCD = 20, COM = 29). Difference between TD children and the other groups was assessed using univariate analysis of structural indexes including grey and white matter volumes and functional indexes quantifying activity (fraction of the amplitude of the low frequency fluctuations), local and global connectivity. Regional differences in structural and functional brain indexes were then used to train machine learning models to discriminate among DD, DCD and COM and to find the most discriminant regions. While no imaging index alone discriminated between the three groups, grouping grey and white matter volumes (structural model) or activity, local and global connectivity (functional model) made possible to discriminate among the DD, DCD and COM groups. The most important discrimination was obtained using the functional model, with regions in the cerebellum and the temporal lobe being the most discriminant for DCD and DD children, respectively. Results further showed that children with both DD and DCD have subtle but identifiable brain differences that can only be captured using several imaging indexes pertaining to both brain structure and function.

Reduced pattern similarity in brain activation during orthographic processing in children with developmental dyslexia

Intra-individual variability of neural response has been found to be negatively associated with cognitive proficiency and automaticity. However, whether developmental dyslexia (DD) is marked by greater intra-individual neural variability remains unclear. Using a multivariate approach and dual-control group design, the current study aims to examine whether the pattern similarity of brain activation during a visual spelling task is abnormal in children with DD compared to age control and reading control children. We found that there was reduced intra-subject pattern similarity at the left occipito-temporal regions in children with DD than both control groups, suggesting a neural signature of DD. Furthermore, we found that pattern similarity was positively associated with stability of reaction time and reading fluency in both children with DD and typical control children, suggesting that neural stability supports behavioral stability and automaticity during reading.

Disruption of Functional Brain Networks Underlies the Handwriting Deficit in Children With Developmental Dyslexia.

Developmental dyslexia (DD) is a neurological-based learning disorder that affects 5-17.5% of children. Handwriting difficulty is a prevailing symptom of dyslexia, but its neural mechanisms remain elusive. Using functional magnetic resonance imaging (fMRI), this study examined functional brain networks associated with handwriting in a copying task in Chinese children with DD (n = 17) and age-matched children (n = 36). We found that dyslexics showed reduced network connectivity between the sensory-motor network (SMN) and the visual network (VN), and between the default mode network (DMN) and the ventral attention network (VAN) during handwriting, but not during drawing geometric figures. Moreover, the connectivity strength of the networks showing group differences was correlated with handwriting speed, reading and working memory, suggesting that the handwriting deficit in DD is linked with disruption of a large-scale brain network supporting motoric, linguistic and executive control processes. Taken together, this study demonstrates the alternations of functional brain networks that underly the handwriting deficit in Chinese dyslexia, providing a new clue for the neural basis of DD.

Dissociating executive function and ADHD influences on reading ability in children with dyslexia

Developmental dyslexia (DD) and attention-deficit/hyperactivity disorder (ADHD) are two of the most common neurodevelopmental disorders among school-age children. These disorders frequently co-occur, with up to 40–50% of children with one diagnosis meeting criteria for the other, and similar percentages of children with either DD or ADHD exhibiting impaired executive functions (EF). Although both ADHD and EF deficits are common in dyslexia, there is little evidence about how ADHD and EF deficits specifically influence the brain basis of reading difficulty in dyslexia, and whether the influences of ADHD and EF on dyslexia can be disentangled. The goal of the current study was to investigate, at both behavioral and brain levels, whether reading performance in individuals with dyslexia is more strongly associated with EF or with diagnostic status of comorbid ADHD. We examined reading abilities and EF in children (8-13 years old) with typical reading ability, DD only, or both DD + ADHD. Across both groups with dyslexia, impaired EF was associated with greater impairment on measures loading onto a reading fluency, but not a reading accuracy, factor. There were no significant differences between the DD and DD + ADHD groups on measures of reading fluency or reading accuracy. During functional magnetic resonance imaging (fMRI) while performing a rhyme-matching reading task requiring phonological awareness, typically developing readers showed greater left-hemisphere reading network activation than children with DD or DD + ADHD. Children with DD and DD + ADHD did not show differential activation, but DD children with unimpaired EF showed greater activation than those with impaired EF in reading-related areas. Thus, ADHD status alone had no measurable influence on reading performance or brain activation. Impaired EF in dyslexia, independent of ADHD status, was associated with greater deficits in reading fluency and greater reductions of activation in response to print in the typical left-hemisphere reading network.

Morphosyntactic Skills Influence the Written Decoding Accuracy of Italian Children With and Without Developmental Dyslexia.

Some types of developmental dyslexia (DD) are associated with morphology. Deep DD leads to morphological and semantic errors, and possible comorbidity with syntactic deficits; phonological-output-buffer DD causes problems in decoding longer morphologically complex words. In addition, cross-linguistic studies highlight the effects of morphological awareness on reading accuracy and fluency. The role of morphosyntactic abilities on reading is, however, not clear. This study explores the influence of morphosyntactic competence on reading in Italian children with and without DD. A total of 14 children with DD and 28 with Typical Development (TD) attending the Italian primary school were tested on written decoding, syntactic comprehension of different grammatical structures, and syntactic production of direct object clitic pronouns. DD children were significantly less accurate and slower in reading than TD children. Syntactic skills of the two groups did not differ significantly, but some differences in their acquisitional pace emerged. Syntactic comprehension and production of direct-object-clitic pronouns predicted reading accuracy standard scores, thus suggesting that morphosyntactic abilities, beyond clitics’ weak phonological status, affect decoding accuracy. Decoding accuracy was influenced by reading errors related to morphology (morphological, semantic, and phonological-output-buffer errors). Decoding speed was a specific weakness of DD children and was rather affected by multi-letter combinations. Consistent with a dual-route approach to orthographic processing, we argue that accuracy depends on fine-grained decoding strategies maximizing the precise ordering of letters, thus it is more sensitive to morphosyntactic skills. Morphological reading errors were associated with phonologically weak (determiners, clitic pronouns, and prepositions) and salient words (verbs). This suggests that the decoding of function words and morphologically complex words is particularly demanding and related to both phonological and morphosyntactic skills. Age had a negative predictive effect on semantic errors, compatible with the gradual acquisition of lexical decoding strategies, which seemed to be slowed down by DD. We conclude that oral morphosyntactic skills play a role in reading accuracy in the Italian shallow orthography for both DD and TD children. It is then advisable to assess children’s linguistic profile during DD diagnoses to establish whether some reading errors are related to morphosyntactic weakness. In this case, ad hoc morphosyntactic training might support reading accuracy.

Improving Functional Connectivity in Developmental Dyslexia through Combined Neurofeedback and Visual Training

This study examined the effects of combined neurofeedback (NF) and visual training (VT) on children with developmental dyslexia (DD). Although NF is the first noninvasive approach to support neurological disorders, the mechanisms of its effects on the brain functional connectivity are still unclear. A key question is whether the functional connectivities of the EEG frequency networks change after the combined NF–VT training of DD children (postD). NF sessions of voluntary α/θ rhythm control were applied in a low-spatial-frequency (LSF) illusion contrast discrimination, which provides feedback with visual cues to improve the brain signals and cognitive abilities in DD children. The measures of connectivity, which are defined by small-world propensity, were sensitive to the properties of the brain electrical oscillations in the quantitative EEG-NF training. In the high-contrast LSF illusion, the z-NF reduced the α/θ scores in the frontal areas, and in the right ventral temporal, occipital–temporal, and middle occipital areas in the postD (vs. the preD) because of their suppression in the local hub θ-network and the altered global characteristics of the functional θ-frequency network. In the low-contrast condition, the z-NF stimulated increases in the α/θ scores, which induced hubs in the left-side α-frequency network of the postD, and changes in the global characteristics of the functional α-frequency network. Because of the anterior, superior, and middle temporal deficits affecting the ventral and occipital–temporal pathways, the z-NF–VT compensated for the more ventral brain regions, mainly in the left hemispheres of the postD group in the low-contrast LSF illusion. Compared to pretraining, the NF–VT increased the segregation of the α, β (low-contrast), and θ networks (high-contrast), as well as the γ2-network integration (both contrasts) after the termination of the training of the children with developmental dyslexia. The remediation compensated more for the dorsal (prefrontal, premotor, occipital–parietal connectivities) dysfunction of the θ network in the developmental dyslexia in the high-contrast LSF illusion. Our findings provide neurobehavioral evidence for the exquisite brain functional plasticity and direct effect of NF–VT on cognitive disabilities in DD children.

Quality of life in Chinese children with developmental dyslexia: a cross-sectional study

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...

Specific Cues Can Improve Procedural Learning and Retention in Developmental Coordination Disorder and/or Developmental Dyslexia.

The present study investigates procedural learning of motor sequences in children with developmental coordination disorder (DCD) and/or developmental dyslexia (DD), typically-developing children (TD) and healthy adults with a special emphasis on (1) the role of the nature of stimuli and (2) the neuropsychological functions associated to final performance of the sequence. Seventy children and ten adults participated in this study and were separated in five experimental groups: TD, DCD, DD, and DCD + DD children and adults. Procedural learning was assessed with a serial reaction time task (SRTT) that required to tap on a specific key as accurately and quickly as possible when stimuli appeared on the screen. Three types of stimuli were proposed as cues: the classical version of the SRTT with 4 squares aligned horizontally on the screen, giving visuospatial cues (VS cues), and two modified versions, with 4 letters aligned horizontally on the screen (VS + L cues) and letters at the center of the screen (L cues). Reaction times (RT) during the repeated and random blocks allowed assessing three phases of learning: global learning, specific learning and retention of the sequence. Learning was considered as completed when RT evolved significantly in the three phases. Neuropsychological assessment involved, among other functions, memory and attentional functions. Our main result was that learning and retention were not influenced by the available cues in adults whereas learning improved with specific cues in children with or without neurodevelopmental disorders. More precisely, learning was not completed with L cues in children with neurodevelopmental disorders. For children with DD, learning was completed with the VS and VS + L cues whereas for children with DCD (with or without DD), learning was completed with combined VS + L cues. Comorbidity between DD and DCD had no more impact on procedural learning than DCD alone. These results suggest that learning depends on the nature of cues available during practice and that cues allowing learning and retention depend on the type of disorder. Moreover, selective attention was correlated with RT during retention, suggesting that this neuropsychological function is important for procedural learning whatever the available cues.

Failure of resting-state frontal–occipital connectivity in linking visual perception with reading fluency in Chinese children with developmental dyslexia

It is widely accepted that impairment in visual perception impedes children's reading development, and further studies have demonstrated significant enhancement in reading fluency after visual perceptual training. However, the mechanism of the neural linkage between visual perception and reading is unclear. The purpose of this study was to examine the intrinsic functional relationship between visual perception (indexed by the texture discrimination task,TDT) and reading ability (character reading and reading fluency) in Chinese children with developmental dyslexia (DD) and those with typical development (TD). The resting-state functional connectivity (RSFC) between the primary visual cortex (V1, BA17) and the entire brain was analyzed. In addition, how RSFC maps are associated with TDT performance and reading ability in the DD and TD groups was examined. The results demonstrated that the strength of the RSFC between V1 and the left middle frontal gyrus (LMFG, BA9/BA46) was significantly correlated with both the threshold (SOA) of the TDT and reading fluency in TD children but not in DD children. Moreover, LMFG-V1 resting-state connectivity played a mediating role in the association of visual texture discrimination and reading fluency, but not in character reading, in TD children. In contrast, this mediation was absent in DD children, albeit their strengths of RSFC between V1 and the left middle frontal gyrus (LMFG) were comparable to those for the TD group. These findings indicate that typically developing children use the linkage of the RSFC between the V1 and LMFG for visual perception skills, which in turn promote fluent reading; in contrast, children with dyslexia, who had higher TDT thresholds than TD children, could not take advantage of their frontal–occipital connectivity to improve reading fluency abilities. These findings suggest that visual perception plays an important role in reading skills and that children with developmental dyslexia lack the ability to use their frontal–occipital connectivity to link visual perception with reading fluency.

Action Video Games Enhance Attentional Control and Phonological Decoding in Children with Developmental Dyslexia.

Reading acquisition is extremely difficult for about 5% of children because they are affected by a heritable neurobiological disorder called developmental dyslexia (DD). Intervention studies can be used to investigate the causal role of neurocognitive deficits in DD. Recently, it has been proposed that action video games (AVGs)—enhancing attentional control—could improve perception and working memory as well as reading skills. In a partial crossover intervention study, we investigated the effect of AVG and non-AVG training on attentional control using a conjunction visual search task in children with DD. We also measured the non-alphanumeric rapid automatized naming (RAN), phonological decoding and word reading before and after AVG and non-AVG training. After both video game training sessions no effect was found in non-alphanumeric RAN and in word reading performance. However, after only 12 h of AVG training the attentional control was improved (i.e., the set-size slopes were flatter in visual search) and phonological decoding speed was accelerated. Crucially, attentional control and phonological decoding speed were increased only in DD children whose video game score was highly efficient after the AVG training. We demonstrated that only an efficient AVG training induces a plasticity of the fronto-parietal attentional control linked to a selective phonological decoding improvement in children with DD.

Identifying Signs of Dyslexia Test: Evidence of Criterion Validity

Abstract In Brazil, there is a lack of valid instruments for screening for Developmental Dyslexia (DD) and so the aim of this study was an in-depth investigation of evidence of validity based on the relations with external variables for the Identifying Signs of Dyslexia Test (TISD). More specifically, it seeks to investigate the validity of the criterion, i.e. whether such instruments would be capable of identifying this diagnosis. The research involved comparing two samples: (a) children with DD diagnosis (n = 15) and (b) children without complaints of reading and writing difficulties (n = 146). It was found that in all the subtests of which the instrument is made up (reading, writing, visual attention, calculation, motor skills, phonological awareness, rapid naming, short term memory) there were significant differences between the groups, and in the test total. The results suggest that the TISD was able to identify the group with DD, evidencing the validity of the criterion for this instrument.

Improving action video games abilities increases the phonological decoding speed and phonological short-term memory in children with developmental dyslexia

Learning to read is extremely difficult for about 10% of the children because they are affected by a heritable neurobiological disorder called developmental dyslexia (DD). The causal role of cognitive deficits typically associated to DD can be investigated through intervention studies. It has been demonstrated that visual-attention and reading speed could be simultaneously improved by using action video game (AVG) training both in shallow and deep alphabetic orthographies. Here, in a clinical study we showed that after this general-domain behavioral intervention both the phonological decoding speed and phonological short-term memory were increased only in DD children in which their video game score was improved. These findings confirm that an AVG training enhances the efficiency of both visual and auditory processing. The plasticity of the multi-sensory attentional network could explain the reading and reading-related improvements induced by the AVG training in children with DD.

Developmental dyslexia and specific language impairment: distinct syntactic profiles?

ABSTRACTRecent work exploring syntax in developmental dyslexia (DD) has identified morphosyntactic deficits, striking parallelisms between children with DD and specific language impairment (SLI). The question remains open if the underlying causes for such deficits are related to difficulties in phonology, which is affected in DD, or to working memory, as has been previously reported for SLI. We focus on the production of third person accusative clitic pronouns (ACC3) and of homophonous definite determiners in French-speaking children with DD and SLI as well as typically developing (TD) controls. If syntactic complexity modulates performance of DD children, as has already been shown for SLI, we predict children with DD to perform significantly worse on ACC3 compared to definite determiners, which are homophonous but syntactically simpler. In addition, if impairment in ACC3 stems from phonology or working memory difficulties, we expect ACC3 performance in both clinical groups to relate to performance on non-word repetition or forward/backward digit spans. We studied 2 groups of 21 children and adolescents, with DD and SLI (7–15 years) and age-matched TD controls. Results reveal significant weaknesses with ACC3 in DD and SLI groups compared to TD controls, but no difficulty for homophonous definite determiners, confirming a deficit relating specifically to syntactic complexity. As for links to phonology and working memory, a single correlation emerged between ACC3 and the backward digit span in SLI, but not in DD, suggesting different underlying sources for syntactic deficits in these populations. Clinical implications of these results are discussed.

Maternal Stress and Coping Strategies in Developmental Dyslexia: An Italian Multicenter Study.

Studies about the impact of developmental dyslexia (DD) on parenting are scarce. Our investigation aimed to assess maternal stress levels and mothers' copying styles in a population of dyslexic children. A total of 874 children (500 boys, 374 girls; mean age 8.32 ± 2.33 years) affected by DD was included in the study. A total of 1,421 typically developing children (789 boys, 632 girls; mean age 8.25 ± 3.19 years) were recruited from local schools of participating Italian Regions (Abruzzo, Calabria, Campania, Puglia, Umbria, Sicily) and used as control-children group. All mothers (of both DD and typically developing children) filled out an evaluation for parental stress (Parenting Stress Index-Short Form) and coping strategies [Coping Inventory for Stressful Situations (CISS)]. No statistical differences for mean age (p = 0.456) and gender (p = 0.577) were found between DD and control children. Mothers of children affected by DD showed an higher rate of all parental stress indexes (Parental Distress domain p < 0.001, Difficult Child p < 0.001, Parent-Child Dysfunctional Interaction p < 0.001, and Total Stress subscale score p < 0.001) than controls mothers. According to the CISS evaluation, mothers of DD children reported a significantly higher rate of emotion-oriented (p < 0.001) and avoidance-oriented (p < 0.001) coping styles than mothers of typical developing children. On the other hand, a lower representation of task-oriented coping style was found in mothers of DD children (p < 0.001) in comparison to mothers of control-children. Our study shows the clinical relevance of the burden carried by the mothers of children affected by DD and suggests the importance to assess parents, particularly mothers, to improve family compliance and clinical management of this disorder.

Developmental Dyslexia With and Without Language Impairment: ERPs Reveal Qualitative Differences in Morphosyntactic Processing

This study aimed to characterize neuropsychological and linguistic skills in children with Developmental Dyslexia (DD) with and without Language Impairment (LI). Behavioral tests of short-term memory, phonemic awareness, and morphosyntactic processing and electrophysiological responses to agreement violations were administered to 32 DD children (16 with additional LI) and 16 controls. Behavioral data revealed quantitative differences among groups: DD+LI children showed the worst performance, followed by DD-only children and controls. Event-related potential results confirmed atypical morphosyntactic processing in the DD-only group, highlighting qualitative differences between groups. These results support multifactor models of learning disabilities, where different patterns of deficits characterize different subgroups.

The visual magnocellular-dorsal dysfunction in Chinese children with developmental dyslexia impedes Chinese character recognition.

The visual magnocellular-dorsal (M-D) deficit theory of developmental dyslexia (DD) is still highly debated. Many researchers have made great efforts to investigate the relationship between M-D dysfunction and reading disability. Given that visual analysis plays an important role in Chinese reading, the present study tried to examine how the M-D dysfunction affected Chinese character recognition in Chinese children with DD. Sixteen DD children with M-D deficit, fifteen DD children with normal M-D function and twenty-seven age-matched typically developing children participated in this study. A global/local decision task was adopted, in which we manipulated the spatial frequency of target characters to separate an M-D condition from an unfiltered condition. Results of reaction times and error rates showed that in the M-D condition both M-D normal dyslexics and controls exhibited a significant global precedence effect, with faster responses and lower error rates in global decision than in local decision. In contrast, this global advantage was absent for the M-D impaired dyslexics. Accordingly, we propose that the M-D impairment present in some but not all dyslexics might influence global recognition of Chinese characters in this subgroup of children with DD, which might be implicated in their difficulties in learning to read.

The contribution of discrete-trial naming and visual recognition to rapid automatized naming deficits of dyslexic children with and without a history of language delay.

Children with Developmental Dyslexia (DD) are impaired in Rapid Automatized Naming (RAN) tasks, where subjects are asked to name arrays of high frequency items as quickly as possible. However the reasons why RAN speed discriminates DD from typical readers are not yet fully understood. Our study was aimed to identify some of the cognitive mechanisms underlying RAN-reading relationship by comparing one group of 32 children with DD with an age-matched control group of typical readers on a naming and a visual recognition task both using a discrete-trial methodology, in addition to a serial RAN task, all using the same stimuli (digits and colors). Results showed a significant slowness of DD children in both serial and discrete-trial naming (DN) tasks regardless of type of stimulus, but no difference between the two groups on the discrete-trial recognition task. Significant differences between DD and control participants in the RAN task disappeared when performance in the DN task was partialled out by covariance analysis for colors, but not for digits. The same pattern held in a subgroup of DD subjects with a history of early language delay (LD). By contrast, in a subsample of DD children without LD the RAN deficit was specific for digits and disappeared after slowness in DN was partialled out. Slowness in DN was more evident for LD than for noLD DD children. Overall, our results confirm previous evidence indicating a name-retrieval deficit as a cognitive impairment underlying RAN slowness in DD children. This deficit seems to be more marked in DD children with previous LD. Moreover, additional cognitive deficits specifically associated with serial RAN tasks have to be taken into account when explaining deficient RAN speed of these latter children. We suggest that partially different cognitive dysfunctions underpin superficially similar RAN impairments in different subgroups of DD subjects.