Motor impairment in dyslexia: the influence of attention disorders

Perinatal adversities as a common factor underlying the association between atypical laterality and neurodevelopmental disorders: A developmental perspective

Several neurodevelopmental disorders are associated with a higher prevalence of atypical laterality (e.g., left-handedness). Both genetic and non-genetic factors play a role in this association, yet the underlying neurobiological mechanisms are largely unclear. Recent studies have found that stress, mediated by the hypothalamic-pituitary-adrenal (HPA) axis, could be linked to laterality development. These findings provide an opportunity to explore new theoretical perspectives on the association between atypical laterality and neurodevelopmental disorders. This article aims to provide a theoretical framework demonstrating how perinatal adversities could disrupt the typical developmental trajectories of both laterality and neurodevelopment, potentially impacting both the HPA axis and the vestibular system. Additionally, we argue that the relationship between atypical laterality and neurodevelopmental disorders cannot be understood by simply linking genetic and non-genetic factors to a diagnosis, but the developmental trajectories must be considered. Based on these ideas, several perspectives for future research are proposed.

Prevalence of malocclusions and parafunctional habits in pediatric patients with developmental dyslexia

Objective

The study aimed to assess the prevalence of dental malocclusion, orthodontic parameters, and parafunctional habits in children with developmental dyslexia (DD).

Methods

Forty pediatric patients (67.5% boys and 32.5% girls, mean age: 11.02 ± 2.53 years, range: 6-15 years) with DD were compared with 40 age- and sex-matched healthy participants for prevalence of dental malocclusion, orthodontic parameters, and parafunctional habits. Dental examinations were performed by an orthodontist.

Results

Pediatric patients with DD exhibited a significantly higher prevalence of Angle Class III malocclusion (22.5% vs. 5.0%, P = 0.024), deep bite (27.5% vs. 7.5%, P = 0.019), midline deviation (55.0% vs. 7.5%, P < 0.0001), midline diastemas (32.5% vs. 7.5%, P = 0.010), wear facets (92.5% vs. 15.0%, P < 0.0001), self-reported nocturnal teeth grinding (82.5% vs. 7.5%, P < 0.0001), nail biting (35.0% vs. 0.0%, P < 0.0001), and atypical swallowing (85.0% vs. 17.5%, P < 0.0001) compared to that in healthy controls.

Conclusions

Pediatric patients with DD showed a higher prevalence of Class III malocclusion, greater orthodontic vertical and transverse discrepancies, and incidence of parafunctional activities. Clinicians and dentists should be aware of the vulnerability of children with dyslexia for exhibiting malocclusion and encourage early assessment and multidisciplinary intervention.

A transdiagnostic approach to neurodiversity in a representative population sample: The N+ 4 model

Background

The concept of neurodiversity draws upon scientific research, and lessons from practice and lived experience to suggest new ways of thinking about neurodevelopmental conditions. Among the formative observations are that characteristics associated with neurodevelopmental conditions are part of a "broader phenotype" of variation across the whole population, and that there appear to be "transdiagnostic" similarities as well as differences in these characteristics. These observations raise important questions that have implications for understanding diversity in neurodevelopmental conditions and in neurocognitive phenotypes across the whole population.

Method

The present work examines broader phenotypes using seven widely used self-report assessments of traits associated with autism, ADHD, dyslexia, Developmental Coordination Disorder/dyspraxia, tic disorders/Tourette's, cortical hyperexcitability associated with subclinical epilepsy, and sensory sensitivities. A representative sample of 995 adults (aged 17-77) in the UK completed self-report measures of neurodiversity, wellbeing, generalized anxiety, and depression, and cognitive abilities (nonverbal intelligence and executive functioning).

Results

We used confirmatory factor analysis to test whether variation and covariation was better characterized (1) by traditional diagnostic labels, or (2) transdiagnostically according to similarities in functions, behaviours, or phenomena. Results indicated that neurodiversity characteristics were best explained using a bifactor model with one general "N" factor and four condition-specific factors.

Conclusion

This was the largest examination to date of the factor structure of broader phenotypes relevant to neurodevelopmental conditions. It provides critical benchmark data, and a framework approach for asking systematic questions about the structure of neurocognitive diversities seen in the whole population and in people with one or more diagnoses.

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.

Phoneme Representation and Articulatory Impairment: Insights from Adults with Comorbid Motor Coordination Disorder and Dyslexia

Phonemic processing skills are impaired both in children and adults with dyslexia. Since phoneme representation development is based on articulatory gestures, it is likely that these gestures influence oral reading-related skills as assessed through phonemic awareness tasks. In our study, fifty-two young dyslexic adults, with and without motor impairment, and fifty-nine skilled readers performed reading, phonemic awareness, and articulatory tasks. The two dyslexic groups exhibited slower articulatory rates than skilled readers and the comorbid dyslexic group presenting with an additional difficulty in respiratory control (reduced speech proportion and increased pause duration). Two versions of the phoneme awareness task (PAT) with pseudoword strings were administered: a classical version under time pressure and a delayed version in which access to phonemic representations and articulatory programs was facilitated. The two groups with dyslexia were outperformed by the control group in both versions. Although the two groups with dyslexia performed equally well on the classical PAT, the comorbid group performed significantly less efficiently on the delayed PAT, suggesting an additional contribution of articulatory impairment in the task for this group. Overall, our results suggest that impaired phoneme representations in dyslexia may be explained, at least partially, by articulatory deficits affecting access to them.

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.

Body into Narrative: Behavioral and Neurophysiological Signatures of Action Text Processing After Ecological Motor Training

Embodied cognition research indicates that sensorimotor training can influence action concept processing. Yet, most studies employ isolated (pseudo)randomized stimuli and require repetitive single-effector responses, thus lacking ecological validity. Moreover, the neural signatures of these effects remain poorly understood. Here, we examined whether immersive bodily training can modulate behavioral and functional connectivity correlates of action-verb processing in naturalistic narratives. The study involved three phases. First, in the Pre-training phase, 32 healthy persons listened to an action text (rich in movement descriptions) and a non-action text (focused on its characters' perceptual and mental processes), completed comprehension questionnaires, and underwent resting-state electroencephalogram (EEG) recordings. Second, in the four-day Training phase, half the participants completed an exergaming intervention (eliciting full-body movements for 60 min a day) while the remaining half played static videogames (requiring no bodily engagement other than button presses). Finally, in the Post-training phase, all participants repeated the Pre-training protocol with different action and non-action texts and a new EEG session. We found that exergaming selectively reduced action-verb outcomes and fronto-posterior functional connectivity in the motor-sensitive ∼ 10-20 Hz range, both patterns being positively correlated. Conversely, static videogame playing yielded no specific effect on any linguistic category and did not modulate functional connectivity. Together, these findings suggest that action-verb processing and key neural correlates can be focally influenced by full-body motor training in a highly ecological setting. Our study illuminates the role of situated experience and sensorimotor circuits in action-concept processing, addressing calls for naturalistic insights on language embodiment.

Stroop performance is related to reading profiles in Hebrew-speaking individuals with dyslexia and typical readers

There is a debate in the literature regarding the level of contribution of executive functions (EF) to reading comprehension (RC), in the context of the simple view of reading (SVR) model. The current study aims to create sub-profiles of reading and cognitive abilities based on a measure traditionally used for evaluating EF, that is, the Stroop task, and specifically, Stroop time. Ninety-seven adults with and without reading difficulties performed reading and cognitive tasks, including the Stroop tests. Four groups were created based on Stroop performance time and a reading profile was created for each group. A mediation analysis was conducted to determine if reading accuracy and linguistic abilities predict RC mediated by Stroop time. Participants with a shorter Stroop time demonstrated better reading abilities, whereas those with longer Stroop time showed decreased reading performance. Stroop time was also negatively associated with better performance in additional cognitive abilities. A mediation analysis suggested that decoding ability and linguistic ability predict RC through EF. Our findings support the SVR model and the involvement of EF in reading proficiency and might be used for designing EF-based interventions for reading and RC difficulties.

Statistical learning in children with a family risk of dyslexia

The assumption that statistical learning is affected in dyslexia has generally been evaluated in children and adults with diagnosed dyslexia, not in pre-literate children with a family risk (FR) of dyslexia. In this study, four-to-five-year-old FR children (n = 25) and No-FR children (n = 33) completed tasks of emerging literacy (phoneme awareness and RAN). They also performed an online non-adjacent dependency learning (NADL) task, based on the Serial Reaction Time (SRT) task paradigm. Children's accuracy (hits), signal sensitivity (d') and reaction times were measured. The FR group performed marginally more poorly on phoneme awareness and significantly more poorly on RAN than the No-FR group. Regarding NADL outcomes, the results were less straightforward: the data suggested successful statistical learning for both groups, as indicated by the hit and reaction time curves found. However, the FR group was less accurate and slower on the task than the No-FR group. Furthermore, unlike the No-FR group, performance in the FR group varied as a function of the specific stimulus presented. Taken together, these findings fail to show a robust difference in statistical learning between children with and without an FR of dyslexia at preschool age, in line with earlier work on older children and adults with dyslexia.

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.

Rhythm and timing as vulnerabilities in neurodevelopmental disorders

Millions of children are impacted by neurodevelopmental disorders (NDDs), which unfold early in life, have varying genetic etiologies and can involve a variety of specific or generalized impairments in social, cognitive and motor functioning requiring potentially lifelong specialized supports. While specific disorders vary in their domain of primary deficit (e.g. autism spectrum disorder (social), attention-deficit/hyperactivity disorder (attention), developmental coordination disorder (motor) and developmental language disorder (language)), comorbidities between NDDs are common. Intriguingly, many NDDs are associated with difficulties in skills related to rhythm, timing and synchrony though specific profiles of rhythm/timing impairments vary across disorders. Impairments in rhythm/timing may instantiate vulnerabilities for a variety of NDDs and may contribute to both the primary symptoms of each disorder as well as the high levels of comorbidities across disorders. Drawing upon genetic, neural, behavioural and interpersonal constructs across disorders, we consider how disrupted rhythm and timing skills early in life may contribute to atypical developmental cascades that involve overlapping symptoms within the context of a disorder's primary deficits. Consideration of the developmental context, as well as common and unique aspects of the phenotypes of different NDDs, will inform experimental designs to test this hypothesis including via potential mechanistic intervention approaches. This article is part of the theme issue 'Synchrony and rhythm interaction: from the brain to behavioural ecology'.

"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).

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.

Effect of comorbid developmental dyslexia on oculomotor behavior in children with developmental coordination disorder: A study with the Developmental Eye Movement test

Studies have suggested a dysfunction in oculomotor skills in children with developmental coordination disorder (DCD). It has been proposed that the Developmental Eye Movement (DEM) test is useful in testing the dyslexics' (DD) oculomotor behavior during reading, in a simple and indirect manner. The present study aimed at exploring the oculomotor behavior in children with DCD as assessed with the DEM test. We thus compared children with DCD to children with DD and to children with both DCD and DD in order to investigate the specificity of the oculomotor difficulties, as measured by the DEM test. Results showed that 1) children with DCD presented mild atypical performance at the DEM test (error z-score only), 2) children with DD presented particularly poor performance at the DEM test, and 3) the co-morbid condition (DCD + DD) did not add to the severity of atypical performance at the DEM test. In sum, children with DCD were the less affected according to the DEM test, and children with DD (isolated or comorbid) presented the most atypical performance. Results at the DEM test did not allow to highlight clear oculomotor atypicalities in DCD. We thus concluded that more research using eye-tracking techniques is needed to explore the nature of oculomotor atypicalities in DCD children, to distinguish DD and DCD oculomotor behavior, and to understand the profile of children with dual diagnosis.

Validation and diagnostic accuracy of coin rotation task for manual dexterity and coordination in children with specific learning disorder

BACKGROUND

This study aimed at determining validity, reliability, and diagnostic accuracy of Coin Rotation Task (CRT) in assessing manual dexterity and coordination of children with specific learning disorder (SLD).

METHODS

In this non-experimental cross-sectional study, 120 children (typically developing children = 60, children with SLD = 60, mean age ± SD =9.18 ± 0.55) were recruited. Test-retest reliability and construct validity of CRT were assessed. Multivariate regression analysis was performed on CRT scores by considering age and gender as covariates and children with SLD with mild dexterity impairment and severe dexterity impairment (SDI) as outcome variables. Receiver-operating characteristics (ROC) curve analysis was carried out to derive validity parameters.

RESULTS

Test-retest reliability of the CRT scores in both subtests were excellent in children with SLD (ICC_2,1: 0.93-0.95) and good to excellent in typically developing children (ICC_2,1: 0.72-0.82). Acceptable construct validity of CRT was also found. The CRT cut-off points were 23 (sensitivity= 89.29%, specificity= 70.37%) and 28 (sensitivity= 80.33%, specificity= 86.36%) for discriminating children with SLD and SDI from typically developing children in dominant and non-dominant hand, respectively.

CONCLUSIONS

The present study indicated good to excellent test-retest reliability, acceptable validity, and high diagnostic accuracy for diagnosing children with SLD based on their dexterity impairment level.Implications for RehabilitationThe Coin Rotation Task (CRT) was modified and validated for use in children.The CRT is a reliable and valid tool with high diagnostic accuracy.The CRT has a good ability for discriminating children with specific learning disorder with severe dexterity impairment form typically developing children.Treatment plans and research designs can be performed by using this valid, reliable, and easy to administer tool.

Action representation deficits in adolescents with developmental dyslexia

Developmental dyslexia (DD), a severe and frequent disorder of reading acquisition, is characterized by a diversity of cognitive and motor deficits whose interactions still remain under debate. Although deficits in the automatization of sensorimotor control have been highlighted, internal action representation allowing prediction has never before been investigated. In this study, we considered action representation of 18 adolescents with pure DD and 18 age-matched typical readers. Participants actually and mentally performed a visually guided pointing task involving strong spatiotemporal constraints (speed/accuracy trade-off paradigm). While actual and mental movement times of typical readers were isochronous and both conformed to Fitts' law, the movement times of dyslexics differed between conditions, and only the actual movement times conformed to Fitts' law. Furthermore, the quality of motor imagery correlated with word reading abilities. This suggests that the process of action representation is impaired in pure DD and supports the sensorimotor perspective of DD. Theoretical implications are discussed.

Children with dyslexia utilize both top-down and bottom-up networks equally in contextual and isolated word reading

INTRODUCTION

Executive functions (EF) include cognitive processes that support learning and reading. Children with dyslexia experience challenges with both reading and reading comprehension. The neurobiological support for EF deficits during reading comprehension, however, has yet to be defined. Here we aimed to identify the neural networks related to EF during a reading comprehension task focusing on top-down and bottom-up networks in children with dyslexia and typical readers (TR).

METHOD

Twenty children with dyslexia and 19 TR aged 8-12 were scanned during a sentence comprehension (SC) task that included isolated words and sentences that make sense, in addition to undergoing reading and EF behavioral assessment. Functional connectivity within and between four EF networks related to top-down and bottom-up processing were calculated.

RESULTS

Children with dyslexia scored significantly lower in reading and EF testing in several subdomains compared to TR. Children with dyslexia displayed decreased accuracy in both task conditions compared to TR during the SC task. Neuroimaging data analysis revealed that TR had greater functional connectivity within and between top-down and bottom-up processes, in the sentence vs. isolated word condition, compared to children with dyslexia.

DISCUSSION

TR demonstrate a reliance on top-down and bottom-up networks only during sentence comprehension. In children with dyslexia, however, this reliance was not found in either of the task conditions, suggesting that both conditions were equally challenging for them. These findings emphasize the involvement of EF networks in the reading comprehension process and highlight their impaired functionality among children with reading difficulties.

Unisensory and multisensory temporal processing in autism and dyslexia: A systematic review and meta-analysis

This study presents a comprehensive systematic review and meta-analysis of temporal processing in autism spectrum disorder (ASD) and developmental dyslexia (DD), two neurodevelopmental disorders in which temporal processing deficits have been highly researched. The results provide strong evidence for impairments in temporal processing in both ASD (g = 0.48) and DD (g = 0.82), as measured by judgments of temporal order and simultaneity. In individual analyses, multisensory temporal processing was impaired for both ASD and DD, and unisensory auditory, visual and tactile processing were all impaired in DD. In ASD, speech stimuli showed moderate impairment effect sizes, whereas nonspeech stimuli showed small effects. Greater reading and spelling skills in DD were associated with greater temporal precision. Temporal deficits did not show changes with age in either disorder. In addition to more clearly defining temporal impairments in ASD and DD, the results highlight common and distinct patterns of temporal processing between these disorders. Deficits are discussed in relation to existing theoretical models, and recommendations are made for future research.

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.

The Effects of Script and Orthographic Complexity on the Handwriting and Spelling Performance of Children With Dyslexia

Handwriting and spelling problems are often associated in dyslexia. However, the nature of their association is still unclear, and most of the existing research in this area is on deep orthographies (mainly English). The extent to which findings are applicable across languages is uncertain. This article examines the effects of script (manuscript/cursive) and orthographic complexity (complex/simple spellings) on the word dictation and word-copying performance of a group of 24 Italian children with dyslexia and handwriting difficulties (DH group, aged 8-10). Their performance was compared with that of a chronologically age-matched group (CA) and a group of younger children matched to the DH group for their handwriting skills (HA: handwriting age group). Children performed two classical handwriting tasks: the alphabet task and a sentence-copy task, and dictation and copy tasks of orthographically complex words and orthographically simple words. Copying was performed in manuscript and cursive. The results show that although the DH group shows a significant deficit in graphomotor processes, orthographic complexity more than the visual-motor characteristics of the task (i.e., script) affects their performance in handwriting. An advantage for cursive script in DH children, but not in the other two groups, emerges from the study.

Daily motor characteristics in children with developmental coordination disorder and in children with specific learning disorder

An association between learning disorders and coordination problems has been reported in several studies over the last few decades. In this study, we have investigated daily motor characteristics in children with a diagnosis of specific learning disorder (SLD) and compared them with those of children with developmental coordination disorder (DCD) and those of typically developing controls. Ninety-six children aged 5 to 12 years were included: 29 with a diagnosis of SLD, 33 of DCD, and 34 controls. The Italian version of the Developmental Coordination Disorder Questionnaire 2007 (DCDQ-Italian) was used to measure children's coordination in everyday functional activities. The mean DCDQ-Italian total score was significantly lower in both SLD and DCD groups as compared with controls. Regarding subscores, both clinical groups scored significantly lower than controls on "Fine motor/handwriting" skills and on "General coordination." The DCD group scored also significantly lower than controls on "Control during movement." Moreover, clinical groups differed from each other, with SLD children scoring significantly higher on "Control during movement" and "General coordination" subscores. SLD children diverged from typically developing children in some motor skills during ordinary activities, and although this discrepancy was not as severe as in DCD children, it could have an impact on self-esteem and sport inclusion.

Cognitive predictors of sequential motor impairments in children with dyslexia and/or attention deficit/hyperactivity disorder

This study examined cognitive predictors of sequential motor skills in 215 children with dyslexia and/or attention deficit/hyperactivity disorder (ADHD). Visual working memory and math fluency abilities contributed significantly to performance of sequential motor abilities in children with dyslexia (N = 67), ADHD (N = 66) and those with a comorbid diagnosis (N = 82), generally without differentiation between groups. In addition, primary diagnostic features of each disorder, such as reading and inattention, did not contribute to the variance in motor skill performance of these children. The results support a unifying framework of motor impairment in children with neurodevelopmental disorders such as dyslexia and ADHD.

Feedforward motor control in developmental dyslexia and developmental coordination disorder: Does comorbidity matter?

BACKGROUND AND AIM

Feedforward and online controls are two facets of predictive motor control from internal models, which is suspected to be impaired in learning disorders. We examined whether the feedforward component is affected in children (8-12 years) with developmental dyslexia (DD) and/or with developmental coordination disorder (DCD) compared to typically developing (TD) children.

METHODS

Children underwent a bimanual unloading paradigm during which a load supported to one arm, the postural arm, was either unexpectedly unloaded by a computer or voluntary unloaded by the subject with the other arm.

RESULTS

All children showed a better stabilization (lower flexion) of the postural arm and an earlier inhibition of the arm flexors during voluntary unloading, indicating anticipation of unloading. Between-group comparisons of kinematics and electromyographic activity of the postural arm revealed that the difference during voluntary unloading was between DD-DCD children and the other groups, with the former showing a delayed inhibition of the flexor muscles.

CONCLUSION

Deficit of the feedforward component of motor control may particularly apply to comorbid subtypes, here the DD-DCD subtype. The development of a comprehensive framework for motor performance deficits in children with learning disorders will be achieved only by dissociating key components of motor prediction and focusing on subtypes and comorbidities.

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.

Neural changes associated to procedural learning and automatization process in Developmental Coordination Disorder and/or Developmental Dyslexia

OBJECTIVE

Recent theories hypothesize that procedural learning may support the frequent overlap between neurodevelopmental disorders. The neural circuitry supporting procedural learning includes, among others, cortico-cerebellar and cortico-striatal loops. Alteration of these loops may account for the frequent comorbidity between Developmental Coordination Disorder (DCD) and Developmental Dyslexia (DD). The aim of our study was to investigate cerebral changes due to the learning and automatization of a sequence learning task in children with DD, or DCD, or both disorders.

METHOD

fMRI on 48 children (aged 8-12) with DD, DCD or DD + DCD was used to explore their brain activity during procedural tasks, performed either after two weeks of training or in the early stage of learning.

RESULTS

Firstly, our results indicate that all children were able to perform the task with the same level of automaticity, but recruit different brain processes to achieve the same performance. Secondly, our fMRI results do not appear to confirm Nicolson and Fawcett's model. The neural correlates recruited for procedural learning by the DD and the comorbid groups are very close, while the DCD group presents distinct characteristics. This provide a promising direction on the neural mechanisms associated with procedural learning in neurodevelopmental disorders and for understanding comorbidity.

Neural Signature of DCD: A Critical Review of MRI Neuroimaging Studies

The most common neurodevelopmental disorders (e.g., developmental dyslexia (DD), autism, attention-deficit hyperactivity disorder (ADHD)) have been the subject of numerous neuroimaging studies, leading to certain brain regions being identified as neural correlates of these conditions, referring to a neural signature of disorders. Developmental coordination disorder (DCD), however, remains one of the least understood and studied neurodevelopmental disorders. Given the acknowledged link between motor difficulties and brain features, it is surprising that so few research studies have systematically explored the brains of children with DCD. The aim of the present review was to ascertain whether it is currently possible to identify a neural signature for DCD, based on the 14 magnetic resonance imaging neuroimaging studies that have been conducted in DCD to date. Our results indicate that several brain areas are unquestionably linked to DCD: cerebellum, basal ganglia, parietal lobe, and parts of the frontal lobe (medial orbitofrontal cortex and dorsolateral prefrontal cortex). However, research has been too sparse and studies have suffered from several limitations that constitute a serious obstacle to address the question of a well-established neural signature for DCD.

Attention during functional tasks is associated with motor performance in children with developmental coordination disorder: A cross-sectional study

This cross-sectional and exploratory study aimed to compare motor performance and electroencephalographic (EEG) attention levels in children with developmental coordination disorder (DCD) and those with typical development, and determine the relationship between motor performance and the real-time EEG attention level in children with DCD.Eighty-six children with DCD [DCD: n = 57; DCD and attention deficit hyperactivity disorder (ADHD): n = 29] and 99 children with typical development were recruited. Their motor performance was assessed with the Movement Assessment Battery for Children (MABC) and attention during the tasks of the MABC was evaluated by EEG.All children with DCD had higher MABC impairment scores and lower EEG attention scores than their peers (P < 0.05). After accounting for age, sex, body mass index, and physical activity level, the attention index remained significantly associated with the MABC total impairment score and explained 14.1% of the variance in children who had DCD but not ADHD (P = 0.009) and 17.5% of the variance in children with both DCD and ADHD (P = 0.007). Children with DCD had poorer motor performance and were less attentive to movements than their peers. Their poor motor performance may be explained by inattention.

Association, characterisation and meta-analysis of SNPs linked to general reading ability in a German dyslexia case-control cohort

Dyslexia is a severe disorder in the acquisition of reading and writing. Several studies investigated the role of genetics for reading, writing and spelling ability in the general population. However, many of the identified SNPs were not analysed in case-control cohorts. Here, we investigated SNPs previously linked to reading or spelling ability in the general population in a German case-control cohort. Furthermore, we characterised these SNPs for functional relevance with in silico methods and meta-analysed them with previous studies. A total of 16 SNPs within five genes were included. The total number of risk alleles was higher in cases than in controls. Three SNPs were nominally associated with dyslexia: rs7765678 within DCDC2, and rs2038137 and rs6935076 within KIAA0319. The relevance of rs2038137 and rs6935076 was further supported by the meta-analysis. Functional profiling included analysis of tissue-specific expression, annotations for regulatory elements and effects on gene expression levels (eQTLs). Thereby, we found molecular mechanistical implications for 13 of all 16 included SNPs. SNPs associated in our cohort showed stronger gene-specific eQTL effects than non-associated SNPs. In summary, our results validate SNPs previously linked to reading and spelling in the general population in dyslexics and provide insights into their putative molecular pathomechanisms.

Influência da atividade física no desempenho motor de crianças com queixas de dificuldades de aprendizagem

Resumo:OBJETIVO:avaliar e comparar o desempenho motor de crianças com e sem dificuldade de aprendizagem após intervenção com aulas de Educação Física direcionada.MÉTODOS:fizeram parte da pesquisa 22 crianças (13 com queixa e 9 sem queixa de dificuldade de aprendizagem) com idade entre 7 e 11 anos, submetidas à avaliação motora; 14 crianças selecionadas para intervenção realizaram 12 sessões de práticas voltadas à esgrima e atividades circenses. Os dados foram analisados por meio de estatística descritiva e inferencial.RESULTADOS:apenas as crianças com queixas de dificuldades de aprendizagem e que foram submetidas à intervenção alcançaram porcentagem de progressão total na avaliação motora maior que 20%; somente as crianças que participaram da intervenção apresentaram esta progressão entre 10 a 20%. As médias de progressão de habilidades específicas e o índice de progressão total foram maiores para o grupo de crianças com queixa de dificuldade de aprendizagem.CONCLUSÃO:indica-se que são possíveis intervenções de profissionais da Educação Física visando auxiliar crianças com dificuldades de aprendizagem e, motivando-as para à prática de atividades físicas.

Procedural learning and automatization process in children with developmental coordination disorder and/or developmental dyslexia

OBJECTIVE

There is increasing evidence to suggest that developmental dyslexia (DD) and developmental coordination disorder (DCD) actually form part of a broader disorder. Their frequent association could be justified by a deficit of the procedural memory system, that subtends many of the cognitive, motor and linguistic abilities that are impaired in both DD and DCD. However, studies of procedural learning in these two disorders have yielded divergent results, and in any case no studies have so far addressed the issue of automatization (dual-task paradigm).

METHODS

We administered a finger tapping task to participants aged 8-12 years (19 DCD, 18 DD, and 22 with both DD and DCD) to explore procedural learning and automatic movements in these three groups of children, comparing motor performances at the prelearning stage, after 2 weeks of training, and in a post-training dual-task condition.

RESULTS

First, results indicated that all the children were able to learn a sequence of movements and even automatize their movements. Second, they revealed between-groups differences in procedural/automatization learning abilities, setting the DCD group apart from the other two. Third, contrary to our expectations concerning comorbidity, they suggested that the DD+DCD association does not have an additional impact on behavioral performances.

Difficulty in Mental, Neuromusculoskeletal, and Movement-Related School Functions Associated With Low Birthweight or Preterm Birth: A Meta-Analysis

OBJECTIVE. Our objective was to perform a meta-analysis to investigate whether low birthweight (LBW) or preterm birth was associated with difficulty in mental, neuromusculoskeletal, and movement-related school function tasks.

METHOD. Two search strategies produced 40 studies that met the inclusion criteria for the meta-analysis and yielded 549 effect sizes (d). Heterogeneity was evaluated by obtaining Q and I-squared values. Egger’s regression intercept test and a funnel plot were used to check for publication bias.

RESULTS. Children born LBW exhibited considerable difficulties in mental (d = −0.655, p &lt; .0001) and neuromusculoskeletal and movement-related tasks (d = −0.391, p &lt; .0001) compared with children of normal birthweight. Children born preterm also exhibited significant difficulties compared with full-term children in mental, neuromusculoskeletal, and movement-related tasks (d = −0.237, p &lt; .0001).

CONCLUSION. Deficits in mental and motor functions in children born LBW or preterm appear to have significant effects on school readiness and academic achievement.

Writing to dictation and handwriting performance among Chinese children with dyslexia: relationships with orthographic knowledge and perceptual-motor skills

The purpose of this study was to investigate the relationships between writing to dictation, handwriting, orthographic, and perceptual-motor skills among Chinese children with dyslexia. A cross-sectional design was used. A total of 45 third graders with dyslexia were assessed. Results of stepwise multiple regression models showed that Chinese character naming was the only predictor associated with word dictation (β=.32); handwriting speed was related to deficits in rapid automatic naming (β=-.36) and saccadic efficiency (β=-.29), and visual-motor integration predicted both of the number of characters exceeded grid (β=-.41) and variability of character size (β=-.38). The findings provided support to a multi-stage working memory model of writing for explaining the possible underlying mechanism of writing to dictation and handwriting difficulties.

Handwriting speed in children with Developmental Coordination Disorder: are they really slower?

Handwriting difficulties are often included in descriptions of Developmental Coordination Disorder (DCD). They are cited as the most common reason for referral to health professionals following parent and teacher concerns about slow and untidy writing. The aim of this study was to compare handwriting performance in English children with and without DCD across a range of writing tasks, to gain a better understanding of the nature of 'slowness' so commonly reported. Twenty-eight 8-14 year-old children with a diagnosis of DCD participated in the study, with 28 typically developing age and gender matched controls. Participants completed the four handwriting tasks from the Detailed Assessment of Speed of Handwriting (DASH) and wrote their own name; all on a digitising writing tablet. The number of words written, speed of pen movements and the time spent pausing during the tasks were calculated. The findings confirmed what many professionals report, that children with DCD produce less text than their peers. However, this was not due to slow movement execution, but rather a higher percentage of time spent pausing. Discussion centres on the understanding of the pausing phenomenon in children with DCD and areas for further research.

Sensory-motor problems in Autism

Despite being largely characterized as a social and cognitive disorder, strong evidence indicates the presence of significant sensory-motor problems in Autism Spectrum Disorder (ASD). This paper outlines our progression from initial, broad assessment using the Movement Assessment Battery for Children (M-ABC2) to subsequent targeted kinematic assessment. In particular, pronounced ASD impairment seen in the broad categories of manual dexterity and ball skills was found to be routed in specific difficulties on isolated tasks, which were translated into focused experimental assessment. Kinematic results from both subsequent studies highlight impaired use of perception-action coupling to guide, adapt and tailor movement to task demands, resulting in inflexible and rigid motor profiles. In particular difficulties with the use of temporal adaption are shown, with "hyperdexterity" witnessed in ballistic movement profiles, often at the cost of spatial accuracy and task performance. By linearly progressing from the use of a standardized assessment tool to targeted kinematic assessment, clear and defined links are drawn between measureable difficulties and underlying sensory-motor assessment. Results are specifically viewed in-light of perception-action coupling and its role in early infant development suggesting that rather than being "secondary" level impairment, sensory-motor problems may be fundamental in the progression of ASD. This logical and systematic process thus allows a further understanding into the potential root of observable motor problems in ASD; a vital step if underlying motor problems are to be considered a fundamental aspect of autism and allow a route of non-invasive preliminary diagnosis.

Non-adjacent dependency learning in infants at familial risk of dyslexia

This study tests the hypothesis that developmental dyslexia is (partly) caused by a deficit in implicit sequential learning, by investigating whether infants at familial risk of dyslexia can track non-adjacent dependencies in an artificial language. An implicit learning deficit would hinder detection of such dependencies, which mark grammatical relations (e.g. between 'is' and '-ing' in 'she is happily singing'). In a head-turn experiment with infants aged 1;6, family risk and typically developing infants were exposed to one of two novel languages containing dependencies of the type a-X-c, b-X-d or a-X-d, b-X-c, with fixed first and third elements and twenty-four different X elements. During test, typically developing children listened longer to ungrammatical strings (i.e. that did not correspond to their training language). However, family-risk children did not discriminate between grammatical and ungrammatical strings, indicating deficient implicit learning. The implications of these findings in relation to dyslexia and other language-based disorders are discussed.

Occlusal traits in developmental dyslexia: a preliminary study

AIM

The objective of the study reported here was to assess the orthodontic features in children affected by developmental dyslexia (DD).

PATIENTS AND METHODS

A total of 28 children affected by DD (22 boys, six girls; mean age: 9.78 ± 1.69 years) were compared with 51 healthy children (38 boys, 13 girls; mean age 9.41 ± 1.48; range 7-10 years). Reading and writing skills were evaluated along with orthodontic features.

RESULTS

The DD and control groups were not significantly different in terms of total intelligence quotient (P = 0.441) and writing skills (P = 0.805 and P = 0.240, respectively), whereas significant differences were observed between the DD group and control group in both word reading (2.018 ± 1.714 vs 0.917 ± 0.563; P = 0.000) and non-word reading (2.537 ± 1.543 vs 0.862 ± 0.244; P = 0.000). Moreover, for many orthodontic features, there was no significant difference between the two groups; only in prevalence of diastemas (57.14%, P = 0.006), midline diastemas (46.42%, P = 0.007), overbite > 4 mm (71.42%, P = 0.006) and overjet > 4 mm (53.57%, P = 0.001), was there a statistically significant difference. According to univariate logistic regression analysis, the presence of diastemas (odds ratio [OR] 4.33; 95% confidence interval [CI] 1.61-11.65), midline diastemas (OR 4.68; 95% CI 1.61-13.43), an overbite >4 mm (OR 1.75; 95% CI 0.64-4.71), or an overjet >4 mm (OR 2.76; 95% CI 1.06-7.20) seems to play a role in the relationship between occlusal abnormalities and DD in children.

CONCLUSION

Children with DD tend to present with altered dental features, particularly in the area of the incisors, suggesting that a persistently different tongue kinematic profile may thus affect both the developmental variability of the tongue and lip and the occlusion.

Project DyAdd: classical eyeblink conditioning in adults with dyslexia and ADHD

In this study of the project DyAdd (Adult Dyslexia and Attention Deficit Disorder in Finland), classical eyeblink conditioning (EBC) was investigated in both delay and trace paradigms in adults (18-55 years) with dyslexia (n = 37), attention deficit-hyperactivity disorder (ADHD; n = 21), their comorbid combination (n = 8), and healthy controls (n = 35). In addition, the profiles of three participants with a rare autosomal dominant cerebellar disease were assessed (episodic ataxia type 2, EA-2). We found that participants with dyslexia were overall slower learners than controls in eyeblink conditioning. Further, they were the only group that had a reduced number of CRs in mediotemporal-dependent trace paradigm compared to the more cerebellum-dependent delay paradigm. Second, ADHD was found to be related to larger CR amplitude. Third, those with a comorbid condition learned faster and manifested CRs that were not well timed. Fourth, the cerebellar patients showed nearly no conditioning at all. Correlations between EBC and various neuropsychological domains (phonological processing, reading, spelling, arithmetic, executive functions, attention, and fine motor control) over all participants resulted in significant relations only for the delay paradigm: Increased amount of reading errors related with later peak latency and increased amount of self-corrections in fine motor control related with larger response magnitude. Within those who conditioned, relations emerged only for the trace paradigm: better spelling was related to larger response magnitude. These results do not lend support to the cerebellar hypothesis of dyslexia. On the contrary, dyslexia in its pure form seems to be related to a relative dysfunction of a larger hippocampal-cerebellar network. Further, larger responses in the ADHD group are suggested to result from their lowered responding threshold.

Behavioural and cognitive phenotypes in children with neurofibromatosis type 1 (NF1): the link with the neurobiological level

Neurofibromatosis type 1 (NF1) is one of the most frequent monogenetic disorder encountered in children. Approximately 50% of children with NF1 develop learning disabilities notably for reading. Understanding the reasons of reading impairment in this context may lead to improve therapeutic methods in NF1 and more generally in reading developmental disorders. An interesting challenge is to disentangle the connections between the different levels of description proposed in the etiological approach. This is the aim of this review based on recent advances in analysis of cognitive deficits observed in children with NF1 and on results of recent brain imaging (structural and functional) or animal model studies.

When all hypotheses are right: a multifocal account of dyslexia

Many hypotheses have been proposed about the brain underpinnings of developmental dyslexia, but none of them accommodates the variable deficits observed. To address the issue of anatomical deficits in dyslexia; total and partial volumes, lateralization indices (LI), and local gray matter volumes (LGMV) were measured. Analyses were performed in large samples of control and dyslexic subjects, and in correlation with their performance on phonological, reading, and spelling tests. Results indicate an absence of net differences in terms of volumes but significant continuities and discontinuities between groups in their correlations between LI, LGMV, and performances. Structural connectivity also highlighted correlations between areas showing (dis)continuities between control and dyslexic subjects. Overall, our data put forward the idea of a multifocal brain abnormalities in dyslexia with a major implication of the left superior temporal gyrus, occipital-temporal cortices, and lateral/medial cerebellum, which could account for the diverse deficits predicted by the different theories.

Gross motor performance and self-perceived motor competence in children with emotional, behavioural, and pervasive developmental disorders: a review

AIMS

Motor performance and self-perceived motor competence have a great impact on the psychosocial development of children in general. In this review, empirical studies of gross motor performance and self-perception of motor competence in children with emotional (depression and anxiety), behavioural, and pervasive developmental disorders are scrutinized, with the objective of identifying specific motor characteristics that may be relevant to clinical practice.

METHOD

A systematic search of studies published between 1997 and 2007 was performed using nine search engines.

RESULTS

Children in all three categories (emotional, behavioural, and pervasive developmental disorders) exhibit poor gross motor performance and problematic self-perception of motor competence, with certain indications of disorder-specific characteristics. In particular, children with emotional disorders have balance problems and self-perceived motor incompetence; children with behavioural disorders show poor ball skills and tend to overestimate their motor performance; children with pervasive developmental disorders demonstrate poor gross motor performance and self-perceived motor incompetence. As a result, children with developmental and emotional disorders are restricted in participating in games and play, which may lead to inactive lifestyles and further disruption of their psychosocial and physical development.

INTERPRETATION

Motor problems need more, to some extent disorder-specific, attention in clinical practice than has been provided to date.

A novel role for DYX1C1, a chaperone protein for both Hsp70 and Hsp90, in breast cancer

AIMS

With three consecutive tetratricopeptide repeat (TPR) motifs at its C-terminus essential for neuronal migration, and a p23 domain at its N-terminus, DYX1C1 was the first gene proposed to have a role in developmental dyslexia. In this study, we attempted to identify the potential interaction of DYX1C1 and heat shock protein, and the role of DYX1C1 in breast cancer.

MAIN METHODS

GST pull-down, a yeast two-hybrid system, RT-PCR, site-directed mutagenesis approach.

KEY FINDINGS

Our study initially confirmed DYX1C1, a dyslexia related protein, could interact with Hsp70 and Hsp90 via GST pull-down and a yeast two-hybrid system. And we verified that EEVD, the C-terminal residues of DYX1C1, is responsible for the identified association. Further, DYX1C1 mRNA was significantly overexpressed in malignant breast tumor, linking with the up-regulated expression of Hsp70 and Hsp90.

SIGNIFICANCE

These results suggest that DYX1C1 is a novel Hsp70 and Hsp90-interacting co-chaperone protein and its expression is associated with malignancy.