Comparison of deficits in cognitive and motor skills among children with dyslexia

Motor skills and capacities in developmental dyslexia: A systematic review and meta-analysis

In recent decades, the connections between academic skills, such as reading, writing, and calculation, and motor skills/capacities have received increasing attention. Many studies provided evidence for motor difficulties in children and adolescents with dyslexia, prompting the need for a meta-analysis to combine these multiple findings. Therefore, we conducted a meta-analysis using PsycINFO, Pubmed, and SportDiscus as scientific databases. A total of 572 studies were analyzed following several stringent inclusion criteria, resulting in the inclusion of 23 peer-reviewed studies in the final analysis. Our results showed that children and adolescents with dyslexia displayed significant different performances in multiple motor tasks and these differences persisted also when the type of motor task was considered as moderator in the analysis. The present findings are in accordance with the literature that supports a close connection between reading disabilities and difficulties in motor skills/capacities.

Cognitive-Motor Training Improves Reading-Related Executive Functions: A Randomized Clinical Trial Study in Dyslexia

Children with developmental dyslexia (DD) often struggle with executive function difficulties which can continue into adulthood if not addressed. This double-blinded randomized clinical trial study evaluated the short-term effects of the Verbal Working Memory-Balance (VWM-B) program on reading-related executive functions, reading skills, and reading comprehension in Persian children with DD. The active control group [12 children with DD with a mean age of 9 years (SD = 0.90)] received training using the single-task VWM program, while the experiment group [15 children with DD with a mean age of 8 years (SD = 0.74)] received training with the dual-task VWM-B program. Both groups received fifteen training sessions, and assessments were conducted before and after the intervention. The groups were homogenized for possible confounders of age, gender, IQ level, and attention level. The study employed separate mixed ANOVA analyses to estimate the impact of training programs on various measured functions. Significant improvements were observed in the outcome measures of backward digit span, text comprehension, verbal fluency, Stroop color-word test and interference, and the reading subtests. Additionally, significant correlations were found between reading skills and backward digit span, text comprehension, verbal fluency, and Stroop variables. In conclusion, the dual-task VWM-B program was found to be more effective than the single-task VWM program in improving selective attention, cognitive inhibition, verbal working memory capacity, information processing speed, naming ability, and lexical access speed. These enhanced executive functions were associated with improved reading skills in children with DD.

Motor Proficiency, Manual Dexterity, and Visual Perception in School-age Children With ADHD: Contribution of Different Comorbidities

Attention-deficit/hyperactivity disorder (ADHD) is often comorbid with a number of other psychiatric conditions. The goal of this study was to investigate whether motor skills, manual dexterity, and visual perception differ in the presence of ADHD and comorbid psychiatric conditions in school-age boys by comparing them to a group of children with typical development (TD). We evaluated 81 boys 6 to 10 years of age in 5 groups: ADHD only (n=18); ADHD+specific learning disorders (ADHD+SLDs) (n=17); ADHD+oppositional defiant disorder (n=16); ADHD+anxiety disorders (n=15); and TD (n=15). The participants with ADHD only and those with ADHD+comorbidity had significantly lower scores than the participants in the TD group in every area we evaluated. The lowest scores were observed in the ADHD+SLD group in all motor skills domains except for the fine motor precision field. Furthermore, the group with ADHD+SLD had statistically significantly lower scores than the 3 other groups with ADHD+comorbidity in 3 areas: balance, upper extremity coordination, and speed and agility. Motor problems in patients with ADHD and comorbid conditions may not be a focus of attention in clinics. However, especially in the case of comorbid conditions accompanying ADHD, it is important to consider problems in motor skills, manual dexterity, and visual perception in evaluation and treatment to increase these children's quality of life.

Working Memory and Manual Dexterity in Dyslexic Children: A Systematic Review and Meta-Analysis

Dyslexic children have impairments in working memory and manual dexterity. Studies have shown that when cognitive development has deficits, motor development is often impaired, indicating a strong interconnection between both domains, and the possibility of interference with each other's proper functioning. Thus, a new literature review is necessary to understand which components of working memory and manual dexterity are affected in dyslexic children and the possible relationship between them. This review aimed to perform a systematic review and meta-analysis to analyze both skills in dyslexic children. The protocol was carried out according to the criteria established by PRISMA being registered at PROSPERO under number CRD 42021238901. Six literature databases were searched to locate studies published between 2001 and 2021: EMBASE, ERIC, ISI Web of Science, PubMed, PsycINFO, and Scopus. 21 studies met the inclusion criteria. The findings suggest that dyslexic children have significantly poorer visuospatial and verbal working memory with more impairments in the phonological loop. No significant differences were found in manual dexterity.

Increased reliance on top-down information to compensate for reduced bottom-up use of acoustic cues in dyslexia

Speech recognition is a complex human behavior in the course of which listeners must integrate the detailed phonetic information present in the acoustic signal with their general linguistic knowledge. It is commonly assumed that this process occurs effortlessly for most people, but it is still unclear whether this also holds true in the case of developmental dyslexia (DD), a condition characterized by perceptual deficits. In the present study, we used a dual-task setting to test the assumption that speech recognition is effortful for people with DD. In particular, we tested the Ganong effect (i.e., lexical bias on phoneme identification) while participants performed a secondary task of either low or high cognitive demand. We presumed that reduced efficiency in perceptual processing in DD would manifest in greater modulation in the performance of primary task by cognitive load. Results revealed that this was indeed the case. We found a larger Ganong effect in the DD group under high than under low cognitive load, and this modulation was larger than it was for typically developed (TD) readers. Furthermore, phoneme categorization was less precise in the DD group than in the TD group. These findings suggest that individuals with DD show increased reliance on top-down lexically mediated perception processes, possibly as a compensatory mechanism for reduced efficiency in bottom-up use of acoustic cues. This indicates an imbalance between bottom-up and top-down processes in speech recognition of individuals with DD.

"Same, same but different": The optimal viewing position effect in developmental dyslexia, developmental coordination disorder and comorbid disorders

The optimal viewing position (OVP) effect indicates that words are identified most quickly when the eyes fixate near the word centre in alphabetic languages. In two studies, we tested OVP in typically developing readers and children with developmental dyslexia (DD), developmental coordination disorder (DCD) and with both disorders (DD + DCD), using a variable-viewing-position technique. Study 1 showed that typically developing readers had developed highly automatized procedures of left-to-right attentional scanning resulting in an inverted J-shape VP curve comparable to what is observed in adult readers and that dyslexics showed non-prototypical one. In Study 2, we observed more typical procedures of left-to-right attentional scanning in children with DCD, isolated or comorbid, compared to DD. Moreover, given the absence of significant group differences between children with DD + DCD and children with isolated DD or DCD, our results reinforce the idea that the comorbid condition does not add to the severity of OVP anomalies. We then concluded that OVP atypicalities are specific to children with DD. Finally, we discussed the usefulness of the OVP effect as a clinical tool to identify possible OVP atypicalities that could be specific of some neurodevelopmental disorders (i.e., DD, DCD or DCD + DD).

A neural index of inefficient evidence accumulation in dyslexia underlying slow perceptual decision making

Visual processing deficits have been widely reported in developmental dyslexia however the locus of cognitive dysfunction remains unclear. Here, we examined the neural correlates of perceptual decision-making using a dot-motion task and electroencephalography (EEG) and investigated whether presenting deficits were unique to children with dyslexia or if they were also evident in other, typically developing children with equally immature reading systems. Sixty-eight children participated: 32 with dyslexia (DD; 16 females); 21 age-matched controls (AM; 11 females) and 15 reading-matched controls (RM; 9 females). All participants completed a bilaterally presented random-dot-motion task while EEG was recorded. Neural signatures of low level sensory processing (steady state visual evoked potentials; SSVEPs), pre-target attentional bias (posterior α power), attentional orienting (N2), evidence accumulation (centro-parietal positive decision signal; CPP) and execution of a motor response (β) were obtained to dissect the temporal sequence of perceptual decision-making. Reading profile provided a score of relative lexical and sublexical skills for each participant. Although all groups performed comparably in terms of task accuracy and false alarm rate, the DD group were slower and demonstrated an earlier peak latency, reduced slope and lower amplitude of the CPP compared with both AM and RM controls. Reading profile was found to moderate the relationship between word reading ability, reaction time as well as CPP indices showing that lexical dyslexics responded more slowly and had a shallower slope, reduced amplitude and earlier latency of CPP waveforms than sublexical dyslexics. These findings suggest that children with dyslexia, particularly those with relatively poorer lexical abilities, have a reduced rate and peak of evidence accumulation as denoted by CPP markers yet remain slow in their overt response. This is in keeping with hypotheses that children with dyslexia have impairment in effectively sampling and processing evidence about visual motion stimuli.

The Neurological Basis of Developmental Dyslexia and Related Disorders: A Reappraisal of the Temporal Hypothesis, Twenty Years on

In a now-classic article published a couple of decades ago (Brain, 2000; 123: 2373-2399), I proposed an "extended temporal processing deficit hypothesis of dyslexia", suggesting that a deficit in temporal processing could explain not only language-related peculiarities usually noticed in dyslexic children, but also a wider range of symptoms related to impaired processing of time in general. In the present review paper, I will revisit this "historical" hypothesis both in the light of a new clinical perspective, including the central yet poorly explained notion of comorbidity, and also taking a new look at the most recent experimental work, mainly focusing on brain imaging data. First, consistent with daily clinical practice, I propose to distinguish three groups of children who fail to learn to read, of fairly equal occurrence, who share the same initial presentation (difficulty in mastering the rules of grapheme-phoneme correspondence) but with differing associated signs and/or comorbid conditions (language disorders in the first group, attentional deficits in the second one, and motor coordination problems in the last one), thus suggesting, at least in part, potentially different triggering mechanisms. It is then suggested, in the light of brain imaging information available to date, that the three main clinical presentations/associations of cognitive impairments that compromise reading skills acquisition correspond to three distinct patterns of miswiring or "disconnectivity" in specific brain networks which have in common their involvement in the process of learning and their heavy reliance on temporal features of information processing. With reference to the classic temporal processing deficit of dyslexia and to recent evidence of an inability of the dyslexic brain to achieve adequate coupling of oscillatory brain activity to the temporal features of external events, a general model is proposed according to which a common mechanism of temporal uncoupling between various disconnected-and/or mis-wired-processors may account for distinct forms of specific learning disorders, with reading impairment being a more or less constant feature. Finally, the potential therapeutic implications of such a view are considered, with special emphasis on methods seeking to enhance cross-modal connectivity between separate brain systems, including those using rhythmic and musical training in dyslexic patients.

Manual dexterity predicts phonological decoding speed in typical reading adults

Manual dexterity and phonological decoding involve the posterior parietal cortex, which controls location coding for visually guided actions, as well as a large fronto-cerebellar network. We studied the relationship between manual dexterity and reading ability in adult typical readers. Two measurements of manual dexterity were collected to index the procedural learning effect. A linear regression model demonstrated that phonological short-term memory, manual dexterity at time 1 and procedural learning of manual dexterity predicted phonological decoding speed. Similar results were found when left-hand dexterity at time 1 and procedural learning dexterity were entered last. The better one's phonological decoding skill was, the less fluent their manual dexterity was, suggesting a recycle from object-location to letter-location coding. However, the greater the procedural learning, the faster phonological decoding was, suggesting that larger plasticity of object-location coding was linked to better letter-location coding. An independent role of the interhemispheric connections or of the right posterior parietal cortex is also suggested.

A Temporal Sampling Basis for Visual Processing in Developmental Dyslexia

Knowledge of oscillatory entrainment and its fundamental role in cognitive and behavioral processing has increasingly been applied to research in the field of reading and developmental dyslexia. Growing evidence indicates that oscillatory entrainment to theta frequency spoken language in the auditory domain, along with cross-frequency theta-gamma coupling, support phonological processing (i.e., cognitive encoding of linguistic knowledge gathered from speech) which is required for reading. This theory is called the temporal sampling framework (TSF) and can extend to developmental dyslexia, such that inadequate temporal sampling of speech-sounds in people with dyslexia results in poor theta oscillatory entrainment in the auditory domain, and thus a phonological processing deficit which hinders reading ability. We suggest that inadequate theta oscillations in the visual domain might account for the many magno-dorsal processing, oculomotor control and visual deficits seen in developmental dyslexia. We propose two possible models of a magno-dorsal visual correlate to the auditory TSF: (1) A direct correlate that involves "bottom-up" magnocellular oscillatory entrainment of the visual domain that occurs when magnocellular populations phase lock to theta frequency fixations during reading and (2) an inverse correlate whereby attending to text triggers "top-down" low gamma signals from higher-order visual processing areas, thereby organizing magnocellular populations to synchronize to a theta frequency to drive the temporal control of oculomotor movements and capturing of letter images at a higher frequency.

Problems in Audiovisual Filtering for Children with Special Educational Needs

There is pervasive evidence that problems in sensory processing occur across a range of developmental disorders, but their aetiology and clinical significance remain unclear. The present study investigated the relation between sensory processing and literacy skills in children with and without a background of special educational needs (SEN). Twenty-six children aged between 7 and 12 years old, from both regular classes and SEN programmes, participated. Following baseline tests of literacy, fine motor skills and naming speed, two sets of instruments were administered: the carer-assessed Child Sensory Profile-2 and a novel Audiovisual Animal Stroop (AVAS) test. The SEN group showed significantly higher ratings on three Child Sensory Profile-2 quadrants, together with body position ratings. The SEN participants also showed a specific deficit when required to ignore an accompanying incongruent auditory stimulus on the AVAS. Interestingly, AVAS performance correlated significantly with literacy scores and with the sensory profile scores. It is proposed that the children with SEN showed a specific deficit in "filtering out" irrelevant auditory input. The results highlight the importance of including analysis of sensory processes within theoretical and applied approaches to developmental differences and suggest promising new approaches to the understanding, assessment, and support of children with SEN.

Intrinsic Cortico-Subcortical Functional Connectivity in Developmental Dyslexia and Developmental Coordination Disorder

Developmental dyslexia (DD) and developmental coordination disorder (DCD) are distinct diagnostic disorders. However, they also frequently co-occur and may share a common etiology. It was proposed conceptually a neural network framework that explains differences and commonalities between DD and DCD through impairments of distinct or intertwined cortico-subcortical connectivity pathways. The present study addressed this issue by exploring intrinsic cortico-striatal and cortico-cerebellar functional connectivity in a large (n = 136) resting-state fMRI cohort study of 8–12-year-old children with typical development and with DD and/or DCD. We delineated a set of cortico-subcortical functional circuits believed to be associated with the brain’s main functions (visual, somatomotor, dorsal attention, ventral attention, limbic, frontoparietal control, and default-mode). Next, we assessed, using general linear and multiple kernel models, whether and which circuits distinguished between the groups. Findings revealed that somatomotor cortico-cerebellar and frontoparietal cortico-striatal circuits are affected in the presence of DCD, including abnormalities in cortico-cerebellar connections targeting motor-related regions and cortico-striatal connections mapping onto posterior parietal cortex. Thus, DCD but not DD may be considered as an impairment of cortico-subcortical functional circuits.

Dyslexia Augusti: Does Suetonius describe a pattern of signs consistent with dyslexia?

It is generally agreed that Morgan was the first to reliably describe dyslexia with the case of Percy F. However, Suetonius, in "The lives of the twelve Caesars" describes the Emperor Augustus as having a range of language and literacy difficulties that could be consistent with this diagnosis. Using the framework of cognitive psychology, which rarely comments on the historical record, this article argues that Suetonius describes both signs and compensating strategies typical of an adult with remediated developmental dyslexia. If accepted, this analysis would locate a possible coherent description of the condition back to the second century CE.

Development of Dyslexia: The Delayed Neural Commitment Framework

It is now evident that explanations of many developmental disorders need to include a network perspective. In earlier work, we proposed that developmental dyslexia (DD) is well-characterized in terms of impaired procedural learning within the language networks, with the cerebellum being the key structure involved. Here, we deepen the analysis to include the child's developmental process of constructing these networks. The "Delayed Neural Commitment (DNC)" framework proposes that, in addition to slower skill acquisition, dyslexic children take longer to build (and to rebuild) the neural networks that underpin the acquisition of reading. The framework provides an important link backwards in time to the development of executive function networks and the earlier development of networks for language and speech. It is consistent with many theories of dyslexia while providing fruitful suggestions for further research at the genetic, brain, cognitive and behavioral levels of explanation. It also has significant implications for assessment and teaching.

No evidence for cerebellar abnormality in adults with developmental dyslexia

Developmental dyslexia is commonly believed to result from a deficiency in the recognition and processing of speech sounds. According to the cerebellar deficit hypothesis, this phonological deficit is caused by deficient cerebellar function. In the current study, 26 adults with developmental dyslexia and 25 non-dyslexic participants underwent testing of reading-related skills, cerebellar functions, and MRI scanning of the brain. Anatomical assessment of the cerebellum was conducted with voxel-based morphometry. Behavioural evidence, that was indicative of impaired cerebellar function, was found to co-occur with reading impairments in the dyslexic subjects, but a causal relation between the two was not observed. No differences in local grey matter volume, nor in structure-function relationships within the cerebellum were found between the two groups. Possibly, the observed behavioural pattern is due to aberrant white matter connectivity. In conclusion, no support for the cerebellar deficit hypothesis or the presence of anatomical differences of the cerebellum in adults with developmental dyslexia was found.

Saccade adaptation deficits in developmental dyslexia suggest disruption of cerebellar-dependent learning

BACKGROUND

Estimates of the prevalence of developmental dyslexia in the general population range from 5% to as many as 10%. Symptoms include reading, writing, and language deficits, but the severity and mix of symptoms can vary widely across individuals. In at least some people with dyslexia, the structure and function of the cerebellum may be disordered. Saccadic adaptation requires proper function of the cerebellum and brainstem circuitry and might provide a simple, noninvasive assay for early identification and sub-phenotyping in populations of children who may have dyslexia.

METHODS

Children between the ages of 7 and 15 served as participants in this experiment. Fifteen had been diagnosed with developmental dyslexia and an additional 15 were typically developing children. Five of the participants diagnosed with dyslexia were also diagnosed with an attention deficit hyperactivity disroder and were excluded from further analyses. Participants performed in a saccadic adaptation task in which visual errors were introduced at the end of saccadic eye movements. The amplitudes of primary saccades were measured and plotted as a function of the order in which they occurred. Lines of best fit were calculated. Significant changes in the amplitude of primary saccades were identified.

RESULTS

12/15 typically developing children had significant adaptation of saccade amplitude in this experiment. 1/10 participants with dyslexia appropriately altered saccade amplitudes to reduce the visual error introduced in the saccade adaptation paradigm.

CONCLUSIONS

Proper cerebellar function is required for saccadic adaptation, but in at least some children with dyslexia, cerebellar structure and function may be disordered. Consistent with this hypothesis, the data presented in this report clearly illustrate a difference in the ability of children with dyslexia to adapt saccade amplitudes in response to imposed visual errors. Saccadic adaptation might provide a noninvasive assay for early identification of dyslexia. Future work will determine whether reduced saccadic adaptation is pervasive in dyslexia or whether this identifies a sub-phenotype within the larger population of people identified with reading and language deficits.

Morphology and Spelling in French: A Comparison of At-Risk Readers and Typically Developing Children

We present two studies that examine the role of morphology in French spelling. In Study 1, we examined the concurrent and longitudinal relationships between inflectional awareness and derivational awareness and spelling within a sample of 77 children in a French immersion programme in Canada. Children completed a non-verbal reasoning measure and French measures of phonological awareness, word reading, vocabulary, morphological awareness, and spelling. Results showed that inflectional morphological awareness in Grade 3 was a predictor of spelling in the same grade. Inflectional awareness in Grade 2 predicted Grade 3 spelling, controlling for reading-related skills and spelling at Grade 2. These analyses support the role of inflectional morphological awareness in the development of spelling of children of a range of reading and spelling abilities. In contrast, derivational awareness in Grades 2 and 3 did not predict spelling concurrently in both grades respectively. Study 2 contrasted the morphological errors in the spellings of six children at risk for reading difficulties with those of six chronological age-matched and six reading level-matched children. Analyses showed that at-risk children exhibited more difficulties with spelling roots and suffixes in words as compared with their age-matched peers, although they performed similarly to children matched on reading level. Copyright © 2017 John Wiley & Sons, Ltd.

Exploring the Link between Visual Perception, Visual-Motor Integration, and Reading in Normal Developing and Impaired Children using DTVP-2

Reading is known to be primarily a linguistic task. However, to successfully decode written words, children also need to develop good visual-perception skills. Furthermore, motor skills are implicated in letter recognition and reading acquisition. Three studies have been designed to determine the link between reading, visual perception, and visual-motor integration using the Developmental Test of Visual Perception version 2 (DTVP-2). Study 1 tests how visual perception and visual-motor integration in kindergarten predict reading outcomes in Grade 1, in typical developing children. Study 2 is aimed at finding out if these skills can be seen as clinical markers in dyslexic children (DD). Study 3 determines if visual-motor integration and motor-reduced visual perception can distinguish DD children according to whether they exhibit or not developmental coordination disorder (DCD). Results showed that phonological awareness and visual-motor integration predicted reading outcomes one year later. DTVP-2 demonstrated similarities and differences in visual-motor integration and motor-reduced visual perception between children with DD, DCD, and both of these deficits. DTVP-2 is a suitable tool to investigate links between visual perception, visual-motor integration and reading, and to differentiate cognitive profiles of children with developmental disabilities (i.e. DD, DCD, and comorbid children). Copyright © 2017 John Wiley & Sons, Ltd.

Shared and differentiated motor skill impairments in children with dyslexia and/or attention deficit disorder: From simple to complex sequential coordination

Dyslexia and Attention deficit disorder (AD) are prevalent neurodevelopmental conditions in children and adolescents. They have high comorbidity rates and have both been associated with motor difficulties. Little is known, however, about what is shared or differentiated in dyslexia and AD in terms of motor abilities. Even when motor skill problems are identified, few studies have used the same measurement tools, resulting in inconstant findings. The present study assessed increasingly complex gross motor skills in children and adolescents with dyslexia, AD, and with both Dyslexia and AD. Our results suggest normal performance on simple motor-speed tests, whereas all three groups share a common impairment on unimanual and bimanual sequential motor tasks. Children in these groups generally improve with practice to the same level as normal subjects, though they make more errors. In addition, children with AD are the most impaired on complex bimanual out-of-phase movements and with manual dexterity. These latter findings are examined in light of the Multiple Deficit Model.

Preliminary Report on Neuroanatomical Differences Among Reading Disabled, Nonverbally Gifted, and Gifted-Reading Disabled College Students

Regional comparisons (cortical surface area and thickness) were performed on a well described sample of adults with reading disability alone (RD), nonverbal giftedness alone (G), and reading disability and nonverbal giftedness combined (GRD). These anatomical results are considered in relation to behavioral and functional work previously reported on this sample. GRD-RD regional differences were found in both hemispheres and were more common than GRD-G differences. Regional differences were found in the temporal, parietal, occipital and frontal lobes. While these data are preliminary given the small sample sizes, they suggest future avenues of research on the neurodevelopment of atypical samples.

Visual Attention Processes and Oculomotor Control in Autism Spectrum Disorder: A Brief Review and Future Directions

Autism spectrum disorder (ASD) is defined as persistent deficits in social communication and social interaction, and restricted, repetitive patterns of behavior, interests or activities Diagnostic and Statistical Manual of Mental Disorders (5th ed., DSM-5; American Psychiatric Association, 2013). However, individuals with ASD show clearly atypical visual patterns. So far, indications of abnormal visual attention and oculomotor control concerning stimuli independent of social function in ASD have been found. The same findings have been shown in individuals suffering of other neurodevelopmental disorders (e.g., developmental coordination disorder and developmental dyslexia [DD]). Furthermore, visual attention processes and oculomotor control are supposed to be subserved by the magnocellular visual system, which has been found, in turn, to be dysfunctional in ASD and other neurodevelopmental disabilities (i.e., DD). The purpose of this article is to briefly review the link between oculomotor control and visual attention processes and ASD, and to discuss the specificity and overlap of eye movement findings between ASD and other neurodevelopmental disorders.

Comparing Children with and without Dyslexia on the Movement Assessment Battery for Children and the Test of Gross Motor Development

Dyslexia is the most commonly occurring learning disability in the United States, characterized by difficulties with word recognition, spelling, and decoding. A growing body of literature suggests that deficits in motor skill performance exist in the dyslexic population. This study compared the performance of children with and without dyslexia on different subtests of the Test of Gross Motor Development and Movement Assessment Battery for Children and assessed whether there were developmental changes in the scores of the dyslexic group. Participants included 26 dyslexic children (19 boys and 7 girls; 9.5 yr. old, SD = 1.7) and 23 age- and sex-matched typically developing (17 boys and 6 girls; 9.9 yr. old, SD = 1.3) children as a control group. Mann-Whitney U tests indicated that the dyslexic group performed significantly lower than the control group only on the Total Balance subtest of the Movement Assessment Battery for Children. Additionally, the young dyslexic group performed significantly better on the Total Balance subtest, compared to the older dyslexic group. These results suggest that cerebellar dysfunction may account for differences in performance.

Influence of kindergarten on numbers of multiple developmental delays in preschoolers: an analysis over 14 years

OBJECTIVES

The aim of the study was to calculate the impact that the duration of attendance and the location of the kindergarten (rural versus urban) has on the prevalence of multiple delays in preschool children.

METHODS

We analyzed data from 14,068 preschool children, over a period of 14 consecutive years (1997-2010) from the Bavarian Pre-School Morbidity Survey using software package SPSS 21.0. We assessed the incidence of multiple developmental impairments (twofold or above) in various developmental domains.

RESULTS

The highest prevalence for multiple delays in development existed for twofold impairments in the area of motor (7.9 %) and lowest in fivefold delays in cognition (0.4 %). A shorter duration of visiting a kindergarten (OR: 4.43) and an urban location (OR: 2.53) was associated with an increased risk of multiple delays in development.

CONCLUSIONS

A shorter duration and an urban location of kindergarten attendance are associated with an increased risk for children having multiple developmental impairments. From a public health perspective, the setting and duration of kindergarten attendance may be an important focus in preventive efforts to optimize health outcomes in children.

Relations among motor, social, and cognitive skills in pre-kindergarten children with developmental disabilities

Despite the comorbidity between motor difficulties and certain disabilities, limited research has examined links between early motor, cognitive, and social skills in preschool-aged children with developmental disabilities. The present study examined the relative contributions of gross motor and fine motor skills to the prediction of improvements in children's cognitive and social skills among 2,027 pre-kindergarten children with developmental disabilities, including specific learning disorder, speech/language impairment, intellectual disability, and autism spectrum disorder. Results indicated that for pre-kindergarten children with developmental disabilities, fine motor skills, but not gross motor skills, were predictive of improvements in cognitive and social skills, even after controlling for demographic information and initial skill levels. Moreover, depending on the type of developmental disability, the pattern of prediction of gross motor and fine motor skills to improvements in children's cognitive and social skills differed. Implications are discussed.

Rapid Naming in Brazilian Students with Dyslexia and Attention Deficit Hyperactivity Disorder

INTRODUCTION

The effective development of reading and writing skills requires the concerted action of several abilities, one of which is phonological processing. One of the main components of phonological processing is rapid automatized naming (RAN)-the ability to identify and recognize a given item by the activation and concomitant articulation of its name.

OBJECTIVE

To assess the RAN performance of schoolchildren with dyslexia and attention deficit hyperactivity disorder (ADHD) compared with their peers.

METHODS

In total, 70 schoolchildren aged between 8 and 11 years participated in the study. Of these, 16 children had a multiprofessional diagnosis of ADHD while 14 were diagnosed with dyslexia. Matched with these groups, 40 schoolchildren with no history of developmental impairments were also evaluated. The RAN test was administered to assess the length of time required to name a series of familiar visual stimuli. The statistical analysis was conducted using measures of descriptive statistics and the 2-sample t-test at the 5% significance level.

RESULTS

The performance of the group with dyslexia was inferior to that of the control group in all tasks and the ADHD group had inferior performance for color and letters-naming tasks. The schoolchildren with dyslexia and those with ADHD showed very similar response times. Age was an important variable to be analyzed separately. As they aged, children with typical language development had fast answers on colors and digits tasks while children with dyslexia or ADHD did not show improvement with age.

CONCLUSIONS

The schoolchildren with dyslexia took longer to complete all tasks and ADHD took longer to complete digits and objects tasks in comparison to their peers with typical development. This ability tended to improve with age, which was not the case, however, with schoolchildren who had ADHD or dyslexia.

Developmental coordination disorder: core sensori-motor deficits, neurobiology and etiology

Among developmental disorders, DCD is one of the least studied and less understood one (Bishop, 2010). This review summarizes the current understanding of developmental coordination disorder in neuropsychology with a focus mainly on high level sensorimotor impairments, its etiology and its neural bases. We summarize these core deficits in the framework of an influent motor control model (Blakemore et al., 2002). DCD has several environmental risk factors which probably interplay with genetic factors but those have not been sufficiently identified. High-level sensori-motor deficits are probably multifactorial in DCD and involve predictive coding deficits as well as weaknesses in perceptual and sensory integration. At the brain level, DCD is associated with impaired structure and functions within the motor network. Throughout the review we highlight exciting new findings as well as potential future lines of research to provide a more comprehensive understanding of this disorder.

Impaired Statistical Learning in Developmental Dyslexia

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.

Probabilistic category learning in developmental dyslexia: Evidence from feedback and paired-associate weather prediction tasks

OBJECTIVE

Developmental dyslexia is presumed to arise from specific phonological impairments. However, an emerging theoretical framework suggests that phonological impairments may be symptoms stemming from an underlying dysfunction of procedural learning.

METHOD

We tested procedural learning in adults with dyslexia (n = 15) and matched-controls (n = 15) using 2 versions of the weather prediction task: feedback (FB) and paired-associate (PA). In the FB-based task, participants learned associations between cues and outcomes initially by guessing and subsequently through feedback indicating the correctness of response. In the PA-based learning task, participants viewed the cue and its associated outcome simultaneously without overt response or feedback. In both versions, participants trained across 150 trials. Learning was assessed in a subsequent test without presentation of the outcome, or corrective feedback.

RESULTS

The dyslexia group exhibited impaired learning compared with the control group on both the FB and PA versions of the weather prediction task.

CONCLUSIONS

The results indicate that the ability to learn by feedback is not selectively impaired in dyslexia. Rather it seems that the probabilistic nature of the task, shared by the FB and PA versions of the weather prediction task, hampers learning in those with dyslexia. Results are discussed in light of procedural learning impairments among participants with dyslexia.

Dyslexic and skilled reading dynamics are self-similar

The shape of a word pronunciation time distribution supplies information about the dynamic interactions that support reading performance. Speeded word-naming pronunciation and response time distributions were collected from 20 sixth grade Dutch students with dyslexia and 23 age-matched controls. The participants' pronunciation times were modeled and contrasted with a lognormal inverse power-law mixture distribution. Identical contrasts were also conducted on the same participants' response time distributions derived from flanker, color-naming, and arithmetic tasks. Results indicated that children with dyslexia yield slower, broader, and more variable pronunciation time distributions than their age-matched counterparts. This difference approximated a self-similar rescaling between the two group's aggregate pronunciation time distributions. Moreover, children with dyslexia produced similar, but less prominent trends toward slower and more variable performance across the three non-reading tasks. The outcomes support a proportional continuum rather than a localized deficit account of dyslexia. The mixture distribution's success at describing the participants' pronunciation and response time distributions suggests that differences in proportional contingencies among low-level neurophysiological, perceptual, and cognitive processes likely play a prominent role in the etiology of dyslexia.

Mental rotation and motor performance in children with developmental dyslexia

We compared the performance of normal-reading (N=14) and dyslexic children (N=14) in a chronometric mental rotation task (cMRT) using letters, animals and pseudo-letters, which are objects that look like letters. In a typical chronometric mental rotation task two items are presented simultaneously on a screen whereby the right item is a rotated version of the left item and could be the same or a mirror version of the left item. The mental rotation paradigm is an appropriate method to test predictions of two different approaches trying to explain the problems for dyslexics when reading. According to the functional coordination deficit (FCD) model dyslexics show a failure in suppression of symmetry in the representation of graphemic material and therefore cannot decide whether the letter is normal or mirrored because of an ambiguous mapping between phoneme and grapheme representations. Therefore, the deficits of dyslexic children regarding mental rotation performance are restricted to the stimulus "letters". According to findings that propose the involvement of the cerebellum in mental rotation tasks and a cerebellar deficit in dyslexia, an impaired mental rotation is expected affecting all types of stimuli. To investigate the involvement of the cerebellum, motor performance was additionally assessed because the cerebellum plays an important role in motor functions and motor imagery. For the cMRT we found that the dyslexic children show both slower reaction times regarding the stimulus "letters" and "pseudo-letters" and increased overall reaction times compared to non-dyslexic children. The mental rotation effect was more pronounced in dyslexic children than in normal readers. In contrast to previous approaches, the results of our study support the idea that poor results in mental rotation result from deficits in mental rotation itself rather than from a decision problem after mental rotation which supports the predictions of the cerebellar deficit hypothesis. However, since the impairment of dyslexics regarding mental rotation performance is letter-specific and motor results show no differences between dyslexic and non-dyslexic children, further approaches next to the cerebellar deficit hypothesis must be taken into account, especially in consideration of the fact that there are a number of causes for the failure in reading.

Sensory and motor secondary symptoms as indicators of brain vulnerability

In addition to the primary symptoms that distinguish one disorder from the next, clinicians have identified, yet largely overlooked, another set of symptoms that appear across many disorders, termed secondary symptoms. In the emerging era of systems neuroscience, which highlights that many disorders share common deficits in global network features, the nonspecific nature of secondary symptoms should attract attention. Herein we provide a scholarly review of the literature on a subset of secondary symptoms––sensory and motor. We demonstrate that their pattern of appearance––across a wide range of psychopathologies, much before the full-blown disorder appears, and in healthy individuals who display a variety of negative symptoms––resembles the pattern of appearance of network abnormalities. We propose that sensory and motor secondary symptoms can be important indicators of underlying network aberrations and thus of vulnerable brain states putting individuals at risk for psychopathology following extreme circumstances.

Dissociation between the procedural learning of letter names and motor sequences in developmental dyslexia

Motor sequence learning has been studied extensively in Developmental dyslexia (DD). The purpose of the present research was to examine procedural learning of letter names and motor sequences in individuals with DD and control groups. Both groups completed the Serial Search Task which enabled the assessment of learning of letter names and motor sequences independently of each other. Control participants learned both the letter names as well as the motor sequence. In contrast, individuals with DD were impaired in learning of the letter names sequence and showed a reliable transfer of the motor sequence. Previous studies proved that motor sequence learning is impaired in DD. The present study demonstrated that this deficit is more pronounced when the task to be learned involves linguistic units. This result implies that the procedural learning system of language is more deficient than the motor procedural learning system in individuals with DD. The dissociation between motor and letter names sequence learning in those with DD also implies that the systems underlying these two tasks are separable.

Unilateral implicit motor learning deficit in developmental dyslexia

It has been suggested that developmental dyslexia involves various literacy, sensory, motor skill, and processing speed deficits. Some recent studies have shown that individuals with developmental dyslexia exhibit implicit motor learning deficits, which may be related to cerebellar functioning. However, previous studies on implicit motor learning in developmental dyslexics have produced conflicting results. Findings from cerebellar lesion patients have shown that patients' implicit motor learning performance varied when different hands were used to complete tasks. This suggests that dyslexia may have different effects on implicit motor learning between the two hands if cerebellar dysfunction is involved. To specify this question, we used a one-handed version of a serial reaction time task to compare the performance of 27 Chinese children with developmental dyslexics with another 27 age-matched children without reading difficulties. All the subjects were students from two primary schools, Grades 4 to 6. The results showed that children with developmental dyslexic responded more slowly than nondyslexic children, and exhibited no implicit motor learning in the condition of left-hand response. In contrast, there was no significant difference in reaction time between two groups of children when they used the right hand to respond. This finding indicates that children with developmental dyslexia exhibited normal motor skill and implicit motor learning ability provided the right hand was used. Taken together, these results suggested that Chinese children with developmental dyslexia exhibit unilateral deficits in motor skill and implicit motor learning in the left hand. Our findings lend partial support to the cerebellar deficit theory of developmental dyslexia.

Investigation of language and motor skills in Serbian speaking children with specific language impairment and in typically developing children

Specific language impairment (SLI) is usually defined as a developmental language disorder which does not result from a hearing loss, autism, neurological and emotional difficulties, severe social deprivation, low non-verbal abilities. Children affected with SLI typically have difficulties with the acquisition of different aspects of language and by definition, their impairment is specific to language and no other skills are affected. However, there has been a growing body of literature to suggest that children with SLI also have non-linguistic deficits, including impaired motor abilities. The aim of the current study is to investigate language and motor abilities of a group of thirty children with SLI (aged between 4 and 7) in comparison to a group of 30 typically developing children matched for chronological age. The results showed that the group of children with SLI had significantly more difficulties on the language and motor assessments compared to the control group. The SLI group also showed delayed onset in the development of all motor skills under investigation in comparison to the typically developing group. More interestingly, the two groups differed with respect to which language abilities were correlated with motor abilities, however Imitation of Complex Movements was the unique skill which reliably predicted expressive vocabulary in both typically developing children and in children with SLI.

Striking the right balance: motor difficulties in children and adults with dyslexia

Balance difficulties are an enduring feature of dyslexia research, however results have been inconsistent. We propose that between-study heterogeneity may be attributable to variability in balance tasks, balance measurement, participant age, and inclusion of comorbid disorders such as ADHD. This study attempted to clarify these issues, employing quantitative, continuous measures of balance and blindfolded balance, and using both adult and child participants without comorbid ADHD. Eighty-seven individuals participated: dyslexic adults (n = 17), matched adult controls (n = 30), dyslexic children (n = 16) and matched child controls (n = 24). The study found significant balance deficits for the child dyslexic group in the eyes-open task and a result approaching significance in the blindfolded task. By contrast, the adult dyslexic group showed significant deficits in the blindfolded task only. This result is interpreted in terms of lack of sensitivity of the non-blindfolded balance task for adults, owing to ceiling effects. This highlights the need for the use of age-appropriate tests, and may explain some of the heterogeneity in the literature. It is concluded that there is a significant incidence of balance difficulties in children and adults with dyslexia, even for those without comorbid attention deficit.

Controlled but independent: effects of mental rotation and developmental dyslexia in dual-task settings

In two experiments, we compared the performance of normal-reading (n = 26) and dyslexic children (n = 22) in discriminating letters from their mirrored images. In experiment 1, they were always presented in the upright orientation; in experiment 2, they were presented in different angular orientations (0 degrees, 90 degrees, 180 degrees). In order to determine whether task and dyslexia affect reaction times in early or late stages of processing, a dual-task paradigm was adopted in which the primary task was tone discrimination. Stimulus onset asynchrony (SOA) between first and second task was systematically varied (50 ms versus 400 ms). In both experiments dyslexics were slower overall than controls. No effects of mirror-image letters were found. In experiment 2, mental-rotation effects were additive with SOA. In accordance with earlier findings we concluded that the mental-rotation effect involves central processing capacity. Mental-rotation effects were the same for normal-reading and dyslexic children; mental rotation is not impaired in dyslexia. Remarkably, SOA effects were larger in normal readers than in dyslexics. This result was explained by observing that dyslexics experience decision difficulties already on the first task. As a result, they do not benefit optimally from increased latencies between first and second tasks.

Windows of reflection: conceptualizing dyslexia using the social model of disability

The aim of this study is to develop perceptual knowledge of dyslexia from adults diagnosed with this condition. Historically, the dominant conceptual frameworks used to study dyslexia stem from psychological or educational practice. These disciplines predominantly draw on professional neuro-biological or educational knowledge that can be broadly summarized within a medical or educational model approach. Both the medical and educational models view dyslexia as resulting from a neurological and learning dysfunction. As such, only a small amount of research has attempted to locate dyslexia within a sociological context. This paper analyses the life narratives of adults diagnosed with dyslexia using the social model of disability. The author investigates the impact that disabling barriers have in education and employment for people with dyslexia. The implications of this are discussed, particularly how issues of disabling barriers and social-class structures affect the lives of people with dyslexia. The paper argues that social-class positioning and institutional discrimination (in the form of disabling barriers) shape the experiences of people living with this condition.

[Psychocognitive and psychiatric disorders associated with developmental dyslexia: A clinical and scientific issue]

INTRODUCTION

Dyslexia is a complex neurodevelopemental disorder that affects 5 to 10% of school-age children. This condition consists in a specific learning disability with a neurological origin. These learning difficulties are unexpected in relation to other cognitive abilities and the provision of efficient classroom instruction. A range of neurobiological investigations suggests that disruption of the parieto-temporo-occipital systems underlies a failure of skilled reading to develop. The observation that dyslexia is both a familial and heritable problem was made early on and was confirmed by twin studies. They also suggested that both genetic and environmental factors are involved. Several loci have been implicated in dyslexia, notably on chromosomes 2, 3, 6, 15 and 18 and some candidate genes have been proposed, but no functional mutation has yet been identified.

LITERATURE REVIEW

Dyslexia seldom appears isolated and dyslexic people are very likely to present other kinds of learning disabilities or psychiatric disorders. Specific language impairment, often with a mild outcome, is the most frequently associated with dyslexia. Indeed, late language development is often reported by dyslexic patients and also occurs more frequently among their siblings. Genetic linkage studies suggest some common genetic factor underlying this comorbidity. Dyscalculia is associated with dyslexia in 25% of cases, but most people with dyscalculia do not have any sign of dyslexia. The question of whether dyscalculia associated with dyslexia and dyscalculia itself rely on the same cognitive impairment is still controversial. Impaired motor development is also a common feature that affects nearly 50% of dyslexics and dyslexia is frequent among dyspraxic patients. This association raises the discussion on the role of motor impairment in dyslexia's physiopathology and the cerebellar theory of dyslexia. Beyond its link with other learning disorders, the study of dyslexia's comorbidity highlights psychopathological issues. ADHD is the most frequent psychiatric disorder associated with dyslexia. Underpinnings of this link between the two disorders seem to rely on common cognitive and genetic factors. Some authors have proposed a candidate gene ADRA2A to determine the condition including ADHD and dyslexia. In addition, dyslexics are exposed to a higher risk of anxiodepressive and behavioural disorders. Dyslexic children experience three times more behavioural disorders and one third of children with behavioural problems turn out to be affected by dyslexia. The literature study reveals inconsistent findings about depressed mood among dyslexics, but evidence of a persistent increase in the rate of anxiety disorders. The authors put forward the impact of environmental factors to explain these psychiatric comorbidities.

CONCLUSION

This review emphasizes dyslexia's comorbidities because they represent an important issue, both from a scientific and clinical point of view. Indeed, for clinicians, children showing multiple learning disabilities have specific reeducation and educational needs and dyslexics have a higher risk of emotional and behavioural disorders. On the other hand, dyslexia's comorbidity study provides a powerful method for researchers to investigate the still unknown physiopathology of dyslexia.

Motor impairment and low achievement in very preterm children at eight years of age

AIM

To examine the concurrence of motor impairment and academic underachievement in a group of very preterm children at 8 years of age.

METHODS

All surviving children with a gestational age less than 30 weeks, admitted to the neonatal intensive care unit between 1987 and 1997, were prospectively enrolled in developmental follow-up. Children with a neurosensory disability or a low intelligence score (FSIQ < or = 75 points) were excluded. At 8 years of age the Bruininks Oseretsky Test of Motor Proficiency and standardised tests of academic achievement were administered to a sample of 323 very preterm children.

RESULTS

One hundred and one (31.3%) of these very preterm children were identified as having Developmental Coordination Disorder (DCD). Of the children with DCD, 54.4% also had underachievement in literacy and/or numeracy. As the severity of motor impairment increased so too did the severity and complexity of underachievement. Significantly fewer children with motor impairments participated in after-school sporting activities. Children with DCD required more mechanical ventilation support during their hospital admission.

CONCLUSIONS

This study demonstrated that a significant proportion of children born very preterm find both motor and academic skills difficult in early school years.

Motor performance and dyslexia in a national cohort of 10-year-old children

Data from the 10-year follow-up of the 1970 British Births Survey were examined for associations between motor performance and dyslexia. Five tests of motor performance were used: (a) balancing on one leg, (b) throwing a ball in the air, clapping and catching it, (c) walking backwards, (d) sorting matches and (e) graphaesthesia (recognizing shapes drawn on the palm of the hand). These tests were given to 12 950 children aged between 10 and 11 years old. The cohort was divided into nine groups based on three levels of literacy achievement and three levels of possible indicators of dyslexia. The group with the most severe underachievement and most possible indicators (children most likely to be severely dyslexic) comprised about 2% of the total. Of this group, 35.3% failed one motor test and 16.4% failed more than one (51.7% in total), compared with 26.8% and 7.7% of normal achievers. The children had greater problems with balance than those in the other two severely underachieving groups but the effects were small. It is suggested that the use of a balance test only as a screener for dyslexia could result in a proportion of dyslexics being missed and that remedial motor training programmes for children with dyslexia should be offered only to those with co-occurring motor difficulties.