Motor skill learning in children with Developmental Coordination Disorder

Children with Developmental Coordination Disorder (DCD) are characterized as having motor difficulties and learning impairment that may last well into adolescence and adulthood. Although behavioral deficits have been identified in many domains such as visuo-spatial processing, kinesthetic perception, and cross-modal sensory integration, recent studies suggested that the functional impairment of certain brain areas, such as cerebellum and basal ganglia, are the underlying causes of DCD. This review focuses on the “motor learning deficits” in DCD and their possible neural correlates. It presents recent evidence from both behavioral and neuroimaging studies and discusses dominant neural hypotheses in DCD. Given the heterogeneity of this disorder, a successful intervention program should target the specific deficits on an individual basis. Future neuroimaging studies are critical steps in enhancing our understanding of learning deficits in DCD.     

Coupling online control and inhibitory systems in children with Developmental Coordination Disorder: Goal-directed reaching

For children with Developmental Coordination Disorder (DCD), the real-time coupling between frontal executive function and online motor control has not been explored despite reported deficits in each domain. The aim of the present study was to investigate how children with DCD enlist online control under task constraints that compel the need for inhibitory control. A total of 129 school children were sampled from mainstream primary schools. Forty-two children who met research criteria for DCD were compared with 87 typically developing controls on a modified double-jump reaching task. Children within each skill group were divided into three age bands: younger (6–7 years), mid-aged (8–9), and older (10–12). Online control was compared between groups as a function of trial type (non-jump, jump, anti-jump). Overall, results showed that while movement times were similar between skill groups under simple task constraints (non-jump), on perturbation (or jump) trials the DCD group were significantly slower than controls and corrected trajectories later. Critically, the DCD group was further disadvantaged by anti-jump trials where inhibitory control was required; however, this effect reduced with age. While coupling online control and executive systems is not well developed in younger and mid-aged children, there is evidence of age-appropriate coupling in older children. Longitudinal data are needed to clarify this intriguing finding. The theoretical and applied implications of these results are discussed.     

The risk of reduced physical activity in children with probable Developmental Coordination Disorder: a prospective longitudinal study

The aim of the current study was to test the hypothesis that children with probable Developmental Coordination Disorder have an increased risk of reduced moderate to vigorous physical activity (MVPA), using data from a large population based study. Prospectively collected data from 4331 children (boys = 2065, girls = 2266) who had completed motor coordination testing at 7 years and accelerometry at 12 years were analysed from the Avon Longitudinal Study of Parents and Children (ALSPAC). Probable DCD (p-DCD) was defined, using criteria based on the DSM IV classification, as those children below the 15th centile of the ALSPAC Coordination Test at seven years who had a functional impairment in activities of daily living or handwriting, excluding children with a known neurological diagnosis or IQ < 70. Secondary exposure variables consisted of subtests from the ALSPAC Coordination test (manual dexterity, ball skills and balance). Objective measurement of the average daily minutes of MVPA was recorded as ≥3600 counts per minute (cpm) using actigraph accelerometry. Boys with p-DCD were less physically active than boys without DCD (mean difference in MVPA 4.36 cpm, t = 2.69; p = 0.007). For boys, targeting skill (bean bag toss) was related to increased MVPA, after adjustment for confounding factors including neonatal, family and environmental factors as well as Body Mass Index at age seven and 12 years (β = 0.76, t = 3.37, p < 0.001, CI 0.32-1.20). There was no difference in level of MVPA in girls with and without p-DCD (mean difference 1.35 min, t = 0.97, p = 0.31), which may reflect the low levels of MVPA of girls in this cohort. Our findings suggest that the presence of movement difficulties, particularly poor targeting (bean bag toss/ball skills), at a young age is a potential risk factor for reduced MVPA in boys.     

Impact of tactile function on upper limb motor function in children with Developmental Coordination Disorder

This study investigated the presence of, and relationship between tactile dysfunction and upper limb motor function in children with Developmental Coordination Disorder (DCD) compared to typical developing (TD) children. Participants were 36 children aged 6–12 years. Presence of DCD (n = 20) or TD (n = 16) was confirmed using the Movement Assessment Battery for Children, second edition. All children participated in a comprehensive assessment of tactile registration (Semmes Weinstein Monofilaments); tactile spatial perception (Single Point Localisation (SPL) and two-point discrimination (2PD)); haptic perception (Stereognosis); speed of simple everyday manual tasks (Jebsen–Taylor Test of Hand Function (JTTHF)); and handwriting speed and accuracy (Evaluation Tool of Children's Handwriting (ETCH)). Compared to TD children, children with DCD demonstrated poorer localisation of touch in the non-dominant hand (p = 0.04), slower speed of alphabet writing (p < 0.05) and less legible handwriting (p < 0.01), but no difference in speed of simple everyday manual tasks (JTTHF: p > 0.05). Regression analysis showed that spatial tactile perception (SPL) predicted handwriting legibility (ETCH: r = 0.11) and speed of functional tasks (JTTHF: r = 0.33). These results suggest that tactile function, specifically single point localisation, should be a primary tactile assessment employed to determine reasons for upper limb motor difficulties experienced by children with DCD.     

Health-related quality of life of children with Developmental Coordination Disorder

BackgroundAlthough Developmental Coordination Disorder (DCD) is primarily a motor disorder, it can also impact emotional and psychosocial functioning of children with this condition. Evidence suggests that children with DCD experience lower quality of life than their peers, but few studies have explicitly examined the health-related quality of life (HRQOL) of these children.AimsTo: (1) describe HRQOL of children with DCD compared to typically-developing children; (2) compare HRQOL from the perspectives of children with DCD and their parents; and (3) explore predictors of HRQOL for children with DCD.MethodsData from the KidScreen-52 and Strength and Difficulties Questionnaire were collected from 50 children with DCD [Mean(SD) age: 9.8 (1.2) years] and their parents and compared to normative data.ResultsChildren with DCD and their parents report significantly lower HRQOL compared to published norms. Caregivers have a significantly lower perception of their child’s HRQOL than their child’s self-report in many domains. Parents of children with DCD report that their children experience significantly more emotional and behavioral disturbances compared to norms. Poor motor function and attentional difficulties predict HRQOL.Conclusion and implicationsDCD appears to contribute to lower perceived HRQOL. Findings inform therapeutic targets for children with DCD, beyond motor skill intervention.     

An examination of writing pauses in the handwriting of children with Developmental Coordination Disorder

Difficulties with handwriting are reported as one of the main reasons for the referral of children with Developmental Coordination Disorder (DCD) to healthcare professionals. In a recent study we found that children with DCD produced less text than their typically developing (TD) peers and paused for 60% of a free-writing task. However, little is known about the nature of the pausing; whether they are long pauses possibly due to higher level processes of text generation or fatigue, or shorter pauses related to the movements between letters. This gap in the knowledge-base creates barriers to understanding the handwriting difficulties in children with DCD. The aim of this study was to characterise the pauses observed in the handwriting of English children with and without DCD. Twenty-eight 8–14 year-old children with a diagnosis of DCD participated in the study, with 28 TD age and gender matched controls. Participants completed the 10 min free-writing task from the Detailed Assessment of Speed of Handwriting (DASH) on a digitising writing tablet. The total overall percentage of pausing during the task was categorised into four pause time-frames, each derived from the literature on writing (250 ms to 2 s; 2–4 s; 4–10 s and >10 s). In addition, the location of the pauses was coded (within word/between word) to examine where the breakdown in the writing process occurred. The results indicated that the main group difference was driven by more pauses above 10 s in the DCD group. In addition, the DCD group paused more within words compared to TD peers, indicating a lack of automaticity in their handwriting. These findings may support the provision of additional time for children with DCD in written examinations. More importantly, they emphasise the need for intervention in children with DCD to promote the acquisition of efficient handwriting skill.     

Impaired visuo-motor sequence learning in Developmental Coordination Disorder

The defining feature of Developmental Coordination Disorder (DCD) is the marked impairment in the development of motor coordination (DSM-IV-TR, American Psychiatric Association, 2000). In the current study, we focused on one core aspect of motor coordination: learning to correctly sequence movements. We investigated the procedural, visuo-motor sequence learning abilities of 18 children with DCD and 20 matched typically developing (TD) children, by means of the serial reaction time (SRT) task. Reaction time measurements yielded two important findings. Overall, DCD children demonstrated general learning of visuo-motor task demands comparable to that of TD children but failed to learn the visuo-motor sequence. Interestingly, a sequence recall test, administered after the SRT task, indicated some awareness of the repeating sequence pattern. This suggests that the sequence learning problems of DCD children might be located at the stage of motor planning rather than sequence acquisition.     

Behavioral comparisons in Autism Spectrum Disorder and Developmental Coordination Disorder: A systematic literature review

BackgroundAutism Spectrum Disorder (ASD) and Developmental Coordination Disorder (DCD) are developmental disorders that, since the DSM-5, can be diagnosed as co-occurring conditions. While some recent studies suggest that ASD and DCD have similar traits, others show clear behavioral distinctions between the two conditions. By gathering all studies that included (1) an ASD group and a DCD group, (2) an ASD + DCD group and a DCD group, or (3) ASD, ASD + DCD, and DCD groups, we aimed to identify similarities and differences in behaviors between the two disorders.MethodWe used a systematic search of PubMed (1946 –), Scopus (1970 –), PsycINFO (via EBSCO, 1600 –), CINAHL (via EBSCO, 1937 –), SportDiscus (via EBSCO, 1985 –), and WorldCat (via FirstSearch) in addition to reference list and author name searching PubMed, Scopus, PsycINFO, CINAHL, SportDiscus, and WorldCat to identify original studies that met the following criteria: (1) an ASD group and a DCD group, (2) an ASD + DCD group and a DCD group, or (3) ASD, ASD + DCD, and DCD groups.ResultsFrom the 1598 articles screened, 11 were included in the qualitative analysis. The articles included reported more differences than similarities in individuals with ASD and DCD, with clear distinctions for working memory ability, gestural performance, grip selection, and cortical thickness. Only two studies reported similarities in face processing abilities and perceived competence, and the interventional studies showed group similarities in behavior improvement, such as intelligence and attention.ConclusionsBased on the articles reviewed, we conclude that while DCD and ASD share some behavioral symptoms, the symptom profiles of each disorder are unique and separable. We recommend that the evaluation of potential DCD in individuals with ASD be performed systematically and thoroughly, so as to distinguish this co-occurring condition from sensorimotor symptoms associated with ASD.     

Age-related validity and reliability of the Dutch Little Developmental Coordination Disorder Questionnaire (LDCDQ-NL)

BackgroundEarly recognition of children at risk of Developmental Coordination Disorder (DCD) is important, but variability in motor development in preschool children affects the validity of instruments to reliably detect children at risk of DCD.AimsTo investigate the age-related validity and reliability of the Dutch version of the Little Developmental Coordination Disorder Questionnaire (LDCDQ-NL).Methods and proceduresTwo hundred and sixty 3- to 5-year old children were recruited in the Netherlands. Parents filled out the LDCDQ-NL and children were assessed with the Movement Assessment Battery for Children-2 Test (MABC-2 Test). Internal consistency of the LDCDQ-NL was determined by Cronbach’s alpha. Construct validity was investigated using factor analysis. Concurrent validity was measured by calculating correlations between the LDCDQ-NL and MABC-2. Receiver Operating Characteristics (ROC) were calculated to assess discriminant validity.Outcomes and resultsInternal consistency of the LDCDQ-NL was 0.91. Factor analysis resulted in three factors (Fine motor skills, Locomotor skills, Ball skills). Correlation between the LDCDQ-NL and MABC-2 Test increased with increasing age. With a sensitivity of 80%, specificity increased with age.Conclusions and implicationsThe LDCDQ-NL is a reliable and valid screening instrument for 4- and 5-year old Dutch children; concurrent and discriminant validity are low for 3-year olds.     

Physical fitness in children with Developmental Coordination Disorder: Measurement matters

Children with Developmental Coordination Disorder (DCD) experience considerable difficulties coordinating and controlling their body movements during functional motor tasks. Thus, it is not surprising that children with DCD do not perform well on tests of physical fitness. The aim of this study was to determine whether deficits in motor coordination influence the ability of children with DCD to perform adequately on physical fitness tests. A case–control study design was used to compare the performance of children with DCD (n = 70, 36 boys, mean age = 8y 1mo) and Typically Developing (TD) children (n = 70, 35 boys, mean age = 7y 9mo) on measures of isometric strength (hand-held dynamometry), functional strength, i.e. explosive power and muscular endurance (Functional Strength Measurement), aerobic capacity (20 m Shuttle Run Test) and anaerobic muscle capacity, i.e. muscle power (Muscle Power Sprint Test). Results show that children with DCD were able to generate similar isometric forces compared to TD children in isometric break tests, but were significantly weaker in three-point grip strength. Performance on functional strength items requiring more isolated explosive movement of the upper extremities, showed no significant difference between groups while items requiring muscle endurance (repetitions in 30 s) and items requiring whole body explosive movement were all significantly different. Aerobic capacity was lower for children with DCD whereas anaerobic performance during the sprint test was not. Our findings suggest that poor physical fitness performance in children with DCD may be partly due to poor timing and coordination of repetitive movements.     

A comparison of the oxygen cost and physiological responses to running in children with and without Developmental Coordination Disorder

The aim of this study was to compare the oxygen cost of running in boys with and without Developmental Coordination Disorder (DCD). Fourteen boys with DCD (9.1 ± 1.4 yr) and 16 typically developing (TD) controls (9.4 ± 1.3 yr) were tested on two separate occasions at least a week apart. On the first visit, motor proficiency, body composition and maximal aerobic capacity were established. On the second visit, oxygen consumption was determined via indirect calorimetry while participants ran at three submaximal speeds (7.2 km/h, 8.0 km/h and 8.8 km/h) on a motorised treadmill for 4 min each. Additional physiological responses such as blood lactate, respiratory exchange ratio (RER), heart rate, salivary alpha amylase and pain threshold were monitored at baseline and after each submaximal effort. Although there were no differences in the oxygen cost of running at all three speeds, the boys with DCD had higher blood lactate concentration (7.2 km/h, p = 0.05; 8.0 km/h p = 0.019), heart rate (p ≤ 0.001), RER (8.0 km/h, p = 0.019; 8.8 km/h, p = 0.001), salivary alpha amylase (8.0 km/h, p = 0.023; 8.8 km/h, p = 0.020) and a lower pain threshold (p < 0.01). The higher overall metabolic cost of running in boys with DCD as indicated by the higher RER, heart rate and blood lactate concentrations, together with the higher levels of sympathoadrenal medullary activity and sensitivity to pain, may be deterring factors for participation in physical activity in this population.     

Assessment of gait characteristics and orthotic management in children with Developmental Coordination Disorder: Preliminary findings to inform multidisciplinary care

Developmental Coordination Disorder (DCD) is a neurodevelopmental disorder characterised by impaired motor co-ordination and awkward gait. Despite self-reported findings of pes planus and joint hypermobility in children with DCD, there is little objective evidence regarding the clinical management of the foot in children with DCD. The aims of this research were to report clinical findings of foot posture and lower limb hypermobility in children with DCD and to evaluate the impact of foot orthoses on spatio-temporal gait parameters. Children with DCD were recruited into the study. Participants were randomly assigned to an intervention group who received foot orthoses at the start of their rehabilitation programme or to a second group who received foot orthoses at the end of their intervention programme. Foot posture was assessed with the Foot Posture Index and lower limb hypermobility assessed with the Lower Limb Assessment Score. The effect of foot orthoses was evaluated through assessment of spatio-temporal gait characteristics at baseline and post-rehabilitation programme. Fourteen children were recruited (mdn age 7.5 years) with nine children assigned to the group receiving orthoses early (mdn age 8 years) and five children assigned to the post-rehabilitation orthoses group (mdn age 6.5 years). A pes planus foot posture (FPI score = 8) and lower limb hypermobility (LLAS score = 11) were observed. Changes in spatio-temporal gait parameters failed to reach significance (p > .012) following orthotic invention but demonstrated a trend towards a decreased cadence and increased double support duration. Despite non-significant findings this work offers preliminary support for podiatric intervention in the rehabilitation of children with DCD. Further work is required to understand the biomechanics of gait in children with DCD and appreciate the role of podiatry as a component of multidisciplinary care.     

Gesture production in school vs. clinical samples of children with Developmental Coordination Disorder (DCD) and typically developing children

Dyspraxia, a difficulty in executing an operationalised act, has been associated with Developmental Coordination Disorder (DCD). However, issues relating to the area such as comparisons across modalities, comparisons of school vs. clinical populations, and developmental delay vs. pathology have not been addressed in the same, comprehensive study. In the current study, therefore, familiar gesture production in DCD was addressed in a comprehensive manner to follow-up outstanding issues from previous studies: The production of familiar gestures and praxis imagery in a school (n = 26) vs. clinic sample (n = 19) of children with DCD was examined in relation to typically developing age matched (n = 24) all aged from 9 to 11 years, and two groups of younger children within the age ranges of 5-6 (n = 23) and 4-5 (n = 26) years. Overall, children with Developmental Coordination Disorder showed an impaired ability to produce familiar gestures compared to their typical peers, and this was dependant on the type of gesture and presentation modality. Differences were found between school and clinic samples of children with DCD, suggestive of the recruitment of different underlying mechanisms in the two samples. The results have a bearing on our understanding of the relationship of developmental dyspraxia to DCD, as well as of the issue of developmental delay vs. pathology.     

The efficacy of two task-orientated interventions for children with Developmental Coordination Disorder: Neuromotor Task Training and Nintendo Wii Fit training

Neuromotor Task Training (NTT) and Nintendo Wii Fit Training (Wii training) are both task-based interventions used to improve performance in children with motor coordination problems. The aim of this study was to compare the efficacy of these two interventions on the motor performance, isometric strength and cardiorespiratory fitness (aerobic and anaerobic capacity) of children with Developmental Coordination Disorder (DCD) attending mainstream schools in a low-income setting. A pragmatic, quasi-experimental study design was utilized. Children between the ages of 6–10 years, who scored at or below the 16th percentile on the Movement Assessment Battery for Children-2 (MABC-2) and whose teacher reported a functional motor problem, were allocated to either NTT (n = 37) or Wii training (n = 19) groups depending on school of attendance. The MABC-2, a hand-held dynamometer, the Functional Strength Measure, the Muscle Power Sprint Test and the 20 m Shuttle Run Test were used to assess performance at baseline and after the intervention. The main findings show that the mean motor performance scores of both groups improved over the study period. However, significant differences in improvement were detected between groups, with the NTT group showing greater improvement in motor performance, functional strength and cardiorespiratory fitness. No improvements in isometric strength were seen in either group. The Wii training group showed significant improvement in anaerobic performance. This study provides evidence to support the use of both the Wii Training and NTT for children with DCD. However, in comparison to Wii training, the NTT approach yields superior results across measures of motor proficiency, cardiorespiratory fitness and functional strength. The decision to use either approach may be influenced by resources and time constraints.     

Motor impairments screened by the Movement Assessment Battery for Children-2 are related to the visual-perceptual deficits in children with Developmental Coordination Disorder

This study was to examine to what extent the motor deficits of children with Developmental Coordination Disorder (DCD) verified by the Movement Assessment Battery for Children-2 (MABC-2) are linked to their visual-perceptual abilities. Seventeen children with DCD and seventeen typically developing children (TD) aged 5–10 years screened from a total of 250 children were recruited. The assessments included MABC-2, traditional test of visual perceptual skills (TVPS-R), and computerized test for sequential coupling of eye and hand as well as motion coherence. The results indicated that children with DCD scored lower than TD in MABC-2, and their total scores were highly correlated with manual dexterity component scores. DCD group also showed poor visual-perceptual abilities in various aspects. The visual discrimination and visual sequential memory from the TVPS-R, the sequential coupling of eye and hand, and the motion coherence demonstrated a moderate or strong correlation with the MABC-2 in the DCD rather than the TD group. It was concluded that the motor problems screened by MABC-2 were significantly related to the visual-perceptual deficits of children with DCD. MABC-2 is suggested to be a prescreening tool to identify the visual-perceptual related motor deficits.     

Development of the Little Developmental Coordination Disorder Questionnaire for preschoolers and preliminary evidence of its psychometric properties in Israel

Purpose

The early identification of motor coordination challenges before school age may enable close monitoring of a child's development and perhaps ameliorate some of the social, psychological and behavioral sequela that often accompany unrecognized Developmental Coordination Disorder (DCD). The purpose of this study was to develop and assess the initial psychometric properties of a screening tool, the Little DCD Questionnaire (Little DCDQ), designed to identify DCD amongst preschoolers aged 3 and 4.

Methods

The suitability of the items of the DCDQ’07 for 3- and 4-year-old children was assessed. Four items were found to be suitable and new items were generated. Content validity was ensured using a Table of Specification and the items were categorized into three sub-categories (Control During Movement, Fine Motor and General Coordination). The Little DCDQ was administered to 146 children (91 boys) aged 3 and 4 (mean age = 49.39 ± 7.16 months). Ninety-one typically developing children were included (mean age = 47.80 ± 7.05 months; 46 boys) while 55 children had been referred or were being treated for some form of developmental delay (mean age = 52.02 ± 6.60 months; 45 boys). Of this sample, 28 parents completed the questionnaire twice within a 2-week interval.

Results

Test-retest reliability was evidenced by moderate to good intraclass correlation coefficient values between scores on the two administrations for the total and the three sub-category scores. Evidence of internal consistency was provided by adequate to high Cronbach's alpha co-efficients calculated for each item, each sub-category score and the total score for the total group, and separately for the control group and the clinically referred group. Validity evidence based on relations to other variables was provided by the finding of significant group differences (clinically referred and control) for the total and sub-category scores for both the age groups and the total group.

Conclusions

Based on the preliminary psychometric evidence, it appears that the Little DCDQ meets many of the necessary standards for validity and reliability as a screening instrument, and shows promise as a useful clinical and research tool.     

Evaluation of the Japanese version of the Developmental Coordination Disorder Questionnaire as a screening tool for clumsiness of Japanese children

Developmental Coordination Disorder (DCD) is characterized by clumsiness and coordination difficulties. DCD interferes with academic performance and participation in physical activities and psychosocial functions, such as self-esteem, cognition, or emotion, from childhood through adolescence to adulthood. DCD is a common pediatric condition and its prevalence is estimated to be 6% worldwide. Although English questionnaires are available, there is no questionnaire to identify DCD in Japan, and therefore, no information on its prevalence is available. Recently, we developed the Japanese version of the Developmental Coordination Disorder Questionnaire (DCDQ-J). The purpose of this study was to describe the applicability of the DCDQ-J for use with a community-based population of children in Japan and to investigate the relationships between coordination and attention-deficit hyperactivity disorder (ADHD) tendencies or intelligence. The DCDQ-J was completed by 6330 parents or guardians of children and adolescents. We employed the ADHD-rating scale and determined the intelligence quotient (IQ) of the children. Two-way analysis of variance showed that the scores linearly increased as the children's grades advanced in 2 subscales, namely, control during movement and fine motor. In contrast, non-linear changes were found in the scores of the general coordination subscale. The total scores of the DCDQ-J and ADHD-RS were significantly correlated, but no relationship between DCDQ-J scores and IQ was found. The DCDQ-J is expected to be a useful screening tool to identify and assess motor coordination difficulties of children in Japan and enable cross-cultural comparisons.     

Comorbidity of motor and language impairments in preschool children of Taiwan

Comorbidity of motor and speech/language impairments was investigated in 363 preschool children between the ages of 5 and 6 years (boys: 205, age 6.04 ± 0.48 years; girls: 158, age 5.98 ± 0.53 years). The children were sampled from two municipals of Taiwan, and were determined to present no apparent neurological, musculoskeletal, cardiopulmonary system impairment or mental insufficiency. They were administered with three speech/language tests and a motor test (Movement Assessment Battery for Children, or M-ABC). The results showed a significant correlation between the total score of the motor test and the total score of each of the speech and language tests. Regression analysis that controlled for IQ (C-TONI) further showed that manual dexterity, but not ball skills or balance, of M-ABC was predictive of all scores on the speech and language tests. To determine a deficit on a test, a score at or below the 10th percentile of the norm or a score at or below 1.25 SD from the group mean was established as the cutoff. For the speech/language impairment, a deficit on at least two out of the three tests also applied. Following these criteria, 22 children (6.1%) were identified to have Developmental Speech and Language Disorder (DSLD), and 45 (12.4%) to have Developmental Coordination Disorder (DCD). Comorbid DSLD and DCD were found in six children (1.65%). Chi-square analysis revealed a significant correlation between DSLD and DCD (p < .03). The odds of DSLD was higher (by about three-fold) among the children with DCD than among the children without (0.15 vs. 0.05). Comorbid motor and speech/language impairments in preschool children appear to be a significant clinical condition that requires the attention of the therapeutic community. Manual dexterity, in particular, seems to be an important clue for understanding the shared mechanism of motor and speech/language impairments.     

Mild impairments of motor imagery skills in children with DCD

It has been hypothesized that the underlying mechanism of clumsy motor behaviour in children with Developmental Coordination Disorder (DCD) is caused by a deficit in the internal modelling for motor control. An internal modelling deficit can be shown on a behavioural level by a task that requires motor imagery. Motor imagery skills are suggested to be related to anticipatory action planning, but motor imagery and action planning have not been tested within the same child. In the present study, action planning and motor imagery skills were assessed in 82 children between 7 and 12 years of age. Twenty-one of these children met the criteria for DCD, which was assessed by the McCarron Assessment of Neuromuscular Development and 56 of these children were used in the control group. Motor imagery was tested by a mental rotation task of hands that were shown from a back and palm point of view. The results show that motor imagery is affected in children with DCD but only in conditions with complex task constraints (i.e., rotation of hand stimuli presented in palm view). These results provide partial support for the internal modelling deficit hypothesis. We were not able to elicit motor planning deficits in this group, however, and argue that more complex planning tasks may be needed to identify such deficits.     

Examining the relationship between motor assessments and handwriting consistency in children with and without probable Developmental Coordination Disorder

Children with Developmental Coordination Disorder (DCD) often experience difficulties in handwriting. The current study examined the relationships between three motor assessments and the spatial and temporal consistency of handwriting. Twelve children with probable DCD and 29 children from 7 to 12 years who were typically developing wrote the lowercase letters “e” and “l” in cursive and printed forms repetitively on a digitizing tablet. Three behavioral assessments, including the Beery–Buktenica Developmental Test of Visual-Motor Integration (VMI), the Minnesota Handwriting Assessment (MHA) and the Movement Assessment Battery for Children (MABC), were administered. Children with probable DCD had low scores on the VMI, MABC and MHA and showed high temporal, not spatial, variability in the letter-writing task. Their MABC scores related to temporal consistency in all handwriting conditions, and the Legibility scores in their MHA correlated with temporal consistency in cursive “e” and printed “l”. It appears that children with probable DCD have prominent difficulties on the temporal aspect of handwriting. While the MHA is a good product-oriented assessment for measuring handwriting deficits, the MABC shows promise as a good assessment for capturing the temporal process of handwriting in children with DCD.