Handwriting difficulties in children with dyslexia: Poorer legibility in dictation and alphabet tasks, slowness in the alphabet task.

Several studies have shown that children with dyslexia (DYS), in addition to their reading and spelling deficits, encounter handwriting difficulties that are still poorly understood in terms of their nature and origin. The present study aimed to better understand the handwriting difficulties of children with DYS by comparing their handwriting quality and speed in two tasks, a dictation task and an alphabet task, which required fewer spelling skills than the dictation task. Twenty-nine French-speaking children (Mage = 9.5 years) participated in the study, including 18 children with DYS and nine typically developing (TD) children matched on chronological age. The children performed control tasks, a dictation task with words varying in graphic and orthographic complexity and an alphabet writing task. Accuracy, handwriting quality (legibility), and fluency (speed, writing and pause time) were carefully measured using a digital tablet. GLMM analysis and t tests showed that children with DYS made more aesthetic errors (handwriting quality) in both the dictation and alphabet task than TD children. They also wrote more slowly than TD children in the alphabet task (speed, pause time). These findings suggest that children with DYS present handwriting difficulties, even in a simple alphabet task. In dictation, they seem to favour speed at the expense of handwriting quality.

Unraveling multi-fixel microstructure with tractography and angular weighting.

Recent advances in MRI technology have enabled richer multi-shell sequences to be implemented in diffusion MRI, allowing the investigation of both the microscopic and macroscopic organization of the brain white matter and its complex network of neural fibers. The emergence of advanced diffusion models has enabled a more detailed analysis of brain microstructure by estimating the signal received from a voxel as the combination of responses from multiple fiber populations. However, disentangling the individual microstructural properties of different macroscopic white matter tracts where those pathways intersect remains a challenge. Several approaches have been developed to assign microstructural properties to macroscopic streamlines, but often present shortcomings. ROI-based heuristics rely on averages that are not tract-specific. Global methods solve a computationally-intensive global optimization but prevent the use of microstructural properties not included in the model and often require restrictive hypotheses. Other methods use atlases that might not be adequate in population studies where the shape of white matter tracts varies significantly between patients. We introduce UNRAVEL, a framework combining the microscopic and macroscopic scales to unravel multi-fixel microstructure by utilizing tractography. The framework includes commonly-used heuristics as well as a new algorithm, estimating the microstructure of a specific white matter tract with angular weighting. Our framework grants considerable freedom as the inputs required, a set of streamlines defining a tract and a multi-fixel diffusion model estimated in each voxel, can be defined by the user. We validate our approach on synthetic data and in vivo data, including a repeated scan of a subject and a population study of children with dyslexia. In each case, we compare the estimation of microstructural properties obtained with angular weighting to other commonly-used approaches. Our framework provides estimations of the microstructure at the streamline level, volumetric maps for visualization and mean microstructural values for the whole tract. The angular weighting algorithm shows increased accuracy, robustness to uncertainties in its inputs and maintains similar or better reproducibility compared to commonly-used analysis approaches. UNRAVEL will provide researchers with a flexible and open-source tool enabling them to study the microstructure of specific white matter pathways with their diffusion model of choice.

Evidence of graphomotor dysfunction in children with dyslexia: A combined behavioural and fMRI experiment.

AIM: Children with dyslexia (DYS) have a deficit in spelling (i.e., central processes of writing), and past experiments have suggested that they also frequently experience difficulties in handwriting (i.e., motor peripheral processes of writing) compared with typically developing children (TD). However, the presence of handwriting difficulties in dyslexia is controversial. This experiment aimed to better understand the writing difficulties in DYS children, investigating both the central and peripheral processes of writing and combining cognitive and neuroimaging data. METHOD: Participants were 14 DYS and 14 TD (Mage = 9.5) children. They were assessed on behavioural measures (i.e., spelling, handwriting and manual dexterity). Structural and functional magnetic resonance imaging (MRI) data were collected. The fMRI task was a word-dictation task performed using pencil and paper and a head coil mirror providing visual feedback. RESULTS: Behavioural results revealed a clear spelling deficit and poorer handwriting in DYS than in TD. DYS and TD performed equally in handwriting speed and gross manual dexterity. fMRI data were analysed with an ROI approach using nine central ROIs and 10 peripheral ROIs, which constitute the writing network identified in past literature. fMRI results revealed less brain activation in both central and peripheral ROIs in DYS. The main peripheral differences were located in right lobule VI of the cerebellum. Structural data strengthened the presence of bilateral cerebellar abnormalities in dyslexia. CONCLUSION: The present findings constitute a first piece of evidence that children with dyslexia's writing difficulties are not limited to the central processes of writing (i.e., spelling) and that they extend to the peripheral processes of writing (i.e., handwriting). This experiment is the first study to use an fMRI handwriting task to investigate DYS's writing abilities. These results encourage researchers to continue investigating DYS's spelling and handwriting difficulties with a neuroimaging approach. Future experiments are needed to determine whether the functional and structural anomalies observed are consequences of deviant literacy development or whether they could have a causal role in dyslexia.

Evidence of Altered Functional Connectivity at Rest in the Writing Network of Children with Dyslexia.

AIM: Handwriting abilities in children with dyslexia (DYS) are not well documented in the current literature, and the presence of graphomotor impairment in addition to spelling impairment in dyslexia is controversial. Using resting-state functional connectivity (RSFC), the present study aims to answer the following question: are there markers of graphomotor impairment at rest in DYS children? METHOD: The participants were children with DYS and typically developing (TD) children (n = 32) from French-speaking primary schools (Mage = 9.3 years). The behavioural evaluation consisted of spelling and handwriting measures. Participants underwent a resting-state fMRI scan. RESULTS: Analyses of RSFC focused on a brain region responsible for graphomotor processes-the graphemic/motor frontal area (GMFA). The RSFC between the GMFA and all other voxels of the brain was measured. Whole-brain ANOVAs were run to compare RSFC in DYS and TD children. The results demonstrated reduced RSFC in DYS compared to TD between the GMFA and brain areas involved in both spelling processes and motor-related processes. CONCLUSIONS: For the first time, this study highlighted a disruption of the writing network in DYS. By identifying functional markers of both spelling and handwriting deficits at rest in young DYS participants, this study supports the presence of graphomotor impairment in dyslexia.

How Do Spelling, Handwriting Speed, and Handwriting Quality Develop During Primary School? Cross-Classified Growth Curve Analysis of Children's Writing Development.

Aim: Longitudinal studies are rare in the field of writing research, and little is known about the concurrent development of the two transcription skills: spelling and handwriting. This study was designed to provide a comprehensive picture of the development and the longitudinal relations between spelling, handwriting speed, and handwriting quality at the word level. Method: Over a period of 3 years (coh1: Grades 2-4; coh2: Grades 3-5), 117 French-speaking children were assessed on a single-word dictation task. At each testing time, measures of spelling accuracy, handwriting speed, and handwriting quality were collected on 40 words. Words varied in both orthographic and graphic complexity, making it possible to investigate the influence of these levels of complexity on transcription abilities. Results: Linear growth analyses using cross-classified Bayesian structural equation modeling (CC-BSEM) revealed that spelling and speed continued to improve until Grade 5, while handwriting quality reached an early plateau in Grade 2. In the younger cohort, graphic complexity had a significant influence on the pace of development of handwriting speed and on spelling and handwriting quality performance in Grade 2. In the older cohort, a positive relation between spelling and speed and a negative relation between handwriting speed and handwriting quality were found, indicating that fast handwriting is associated with high spelling ability and that fast handwriting is detrimental to handwriting quality. By providing a better understanding of writing development, this study yields innovative findings not only regarding the development of transcription skills but also regarding how spelling, handwriting speed, and handwriting quality can influence each other's performance throughout primary school.

Do children with dyslexia present a handwriting deficit? Impact of word orthographic and graphic complexity on handwriting and spelling performance.

Several studies have demonstrated that children with dyslexia frequently show poor and slow handwriting skills. It is not clear whether these difficulties are a consequence of their spelling deficit or if they arise from graphomotor difficulties. The present study aims to test the hypothesis of the presence of handwriting difficulties in dyslexia, through the investigation of the impact of graphic and orthographic complexity of words on writing. Participants were all monolingual French-speaking children. Twenty-three children with dyslexia (DYS) were compared to two groups of typically developing children: 23 chronological-age (CA) matched children and 23 spelling-age (SA) matched children. They were assessed on a single-word dictation task of 40 words on a digital tablet. The target words varied in orthographic complexity and in graphic complexity (simple vs. difficult). This task was scored on spelling accuracy, handwriting quality and handwriting speed. General Linear Mixed Model analyses revealed no global differences between the three groups for handwriting quality. However, the DYS children were more impacted by the graphic complexity of words than both the CA and SA children. These findings support the idea that children with dyslexia struggle with the graphomotor aspects of writing and have potential implications for educational and clinical supports.