Mechanisms that underlie coordination in children with developmental coordination disorder

The authors examined potential mechanisms underlying motor coordination in children with developmental coordination disorder (DCD). Because children with DCD experience difficulty processing visual, auditory, and vibrotactile information, the authors explored patterns of choice reaction time (RT) in young (6-7 years) and older (9-10 years) children with and without DCD by using a compatibility-incompatibility paradigm and different sensory modalities. Young children responded more slowly than older children to visual, auditory, and vibrotactile stimuli. Children with DCD took longer than typical children to process visual and vibrotactile stimuli under more complex stimulus-response mappings. Young children with DCD responded more slowly than typical children to visual and vibrotactile information under incompatible conditions. Children with DCD responded faster than unaffected children to auditory stimuli. The results suggest that there is a developmental nature in the processing of visual and auditory input and imply that the vibrotactile sensory modality may be key to the motor coordination difficulties of children with DCD.     

Static balance in children with developmental coordination disorder

The purpose of this study was to compare the postural sway profiles of 9/10-year-old children with developmental coordination disorder and balance problems (DCD-BP, n=64) with those of non-DCD children (n=71). We measured center of pressure excursions in conditions with and without vision for 30s while standing still on the dominant leg, the non-dominant leg, or both legs. Sway area, total path length, and Romberg's quotient were analyzed. Most measures differed significantly between groups, except sway area when the children stood with vision on either the dominant leg or both legs. When standing on the dominant leg or both legs, DCD-BP children demonstrated greater total path length in all conditions and a greater sway area in without-vision conditions. DCD-BP children showed more difficulty standing on the non-dominant leg with eyes both open and closed. While boys showed results similar to the total group, the girls with DCD-BP only exhibited significant differences in three conditions with eyes closed, but not with eyes open. Analysis of Romberg's coefficient also indicated that children with DCD-BP did not over-rely on visual information.     

Procedural learning in children with developmental coordination disorder

Despite the fact that developmental coordination disorder (DCD) is characterised by a deficit in the ability to learn or automate motor skills, few studies have examined motor learning over repeated trials. In this study we examined procedural learning in a group of 10 children with DCD (aged 8-12 years) and age-matched controls without DCD. The learning task was modelled on that of Nissen and Bullemer. Children performed a serial reaction time (SRT) task in which they were required to learn a spatial sequence that repeated itself every 10 trials. Children were not aware of the repetition. Spatial targets were four (horizontal) locations presented on a computer monitor. Children responded using four response keys with the same horizontal mapping as the stimulus. They were tested over five blocks of 100 trials each. The first four blocks presented the same repeating sequence, while the fifth block was randomised. Procedural learning was indexed by the slope of the regression of RT on blocks 1-4. Results showed that most children displayed strong procedural learning of the sequence, despite having no explicit knowledge about it. Overall, there was no group difference in the magnitude of learning over blocks of trials - most children performed within the normal range. Procedural learning for simple sequential movements appears to be intact in children with DCD. This suggests that cortico-striatal circuits that are strongly implicated in the sequencing of simple movements appear to be function normally in DCD.     

Perceptual skills of children with developmental coordination disorder

The aim of this study was to investigate whether children with a Developmental Coordination Disorder (DCD) experience problems in the processing of visual, proprioceptive or tactile information. Different aspects of visual perception were tested with the Developmental Test of Visual Perception (DTVP-2), tactile perception was assessed with the Tactual Performance Test (TPT), and a manual pointing task was employed to measure the ability to use visual and proprioceptive information in goal-directed movements. Nineteen children with DCD and nineteen age and sex-matched controls participated in this study. Differences between groups were most pronounced in the subtests measuring visual-motor integration of the DTVP-2, and in two subtests measuring visual perception (visual closure and position in space). On average the children with DCD performed slightly below the norm for tactile perception, with only three children failing the norm. On the manual pointing task, children with DCD made inconsistent responses towards the targets in all three conditions (visual, visual-proprioceptive and proprioceptive condition). No significant differences between groups were found for absolute error. Inspection of the individual data revealed that only two children failed on the majority of perceptual tasks in the three modalities. Across tasks, no consistent pattern of deficits appeared, illustrating the heterogeneity of the problems of children with DCD.     

Constrained action selection in children with developmental coordination disorder

The effect of advance ('precue') information on short aiming movements was explored in adults, high school children, and primary school children with and without developmental coordination disorder (n=10, 14, 16, 10, respectively). Reaction times in the DCD group were longer than in the other groups and were more influenced by the extent to which the precue constrained the possible action space. In contrast, reaction time did not alter as a function of precue condition in adults. Children with DCD showed greater inaccuracy of response (despite the increased RT). We suggest that the different precue effects reflect differences in the relative benefits of priming an action prior to definitive information about the movement goal. The benefits are an interacting function of the task and the skill level of the individual. Our experiment shows that children with DCD gain a benefit from advance preparation in simple aiming movements, highlighting their low skill levels. This result suggests that goal-directed RTs may have diagnostic potential within the clinic.     

Parameterization of movement execution in children with developmental coordination disorder

The Rhythmic Movement Test (RMT) evaluates temporal and amplitude parameterization and fluency of movement execution in a series of rhythmic arm movements under different sensory conditions. The RMT was used in combination with a jumping and a drawing task, to evaluate 36 children with Developmental Coordination Disorder (DCD) and a matched control group. RMT errors in space and in time were significantly larger for children with DCD. Omission of sensory information decreased the accuracy of movement parameterization in children with DCD more than in the control group, suggesting that children with DCD have more problems in building up an internal representation of the movement. Errors in time correlated significantly with the jumping and drawing task, while errors in space did not. Deficits of temporal movement parameterization might be one of the underlying causes of poor motor performance in some children with DCD.     

Sensory-motor deficits in children with developmental coordination disorder, attention deficit hyperactivity disorder and autistic disorder

Children who have been diagnosed with any one developmental disorder are very likely to meet diagnostic criteria for some other developmental disorder. Although comorbidity has long been acknowledged in childhood disorders, little is understood about the mechanisms that are responsible for the high level of comorbidity. In a series of studies, we have investigated the link between sensory-motor deficits and developmental disorders. Poor sensory-motor integration has long been implicated as a cause of motor problems in developmental disorders such as developmental coordination disorder (DCD), and our recent research has also investigated sensory-motor deficits in children with attention deficit hyperactivity disorder (ADHD) and autistic disorder. Based on a critical examination of relevant literature and some of our recent research findings, we argue that the importance of poor sensory-motor functioning in discriminating children with different disorders has been underestimated. Poor sensory-motor coordination appears to be linked to DCD, but not ADHD. Also, sensory-motor deficits in children with DCD and autistic disorder may provide insight into some of the social difficulties found in these groups of children. This research will increase our understanding of why children with one developmental disorder typically also have problems in other areas.     

Differences in postural control and movement performance during goal directed reaching in children with developmental coordination disorder

Poor upper-limb coordination is a common difficulty for children with developmental coordination disorder (DCD). One hypothesis is that deviant muscle timing in proximal muscle groups results in poor postural and movement control. The relationship between muscle timing, arm motion and children's upper-limb coordination deficits has not previously been studied. The aim of this study was to investigate the relationship between functional difficulties with upper-limb motor skills and neuromuscular components of postural stability and coordination. Sixty-four children aged 8-10 years, 32 with DCD and 32 without DCD, participated in the study. The study investigated timing of muscle activity and resultant arm movement during a rapid, voluntary, goal-directed arm movement. Results showed that compared to children without DCD, children with DCD took significantly longer to respond to visual signals and longer to complete the goal-directed movement. Children with DCD also demonstrated altered activity in postural muscles. In particular, shoulder muscles, except for serratus anterior, and posterior trunk muscles demonstrated early activation. Further, anterior trunk muscles demonstrated delayed activation. In children with DCD, anticipatory function was not present in three of the four anterior trunk muscles. These differences support the hypothesis that in children with DCD, altered postural muscle activity may contribute to poor proximal stability and consequently poor arm movement control when performing goal-directed movement. These results have educational and functional implications for children at school and during activities of daily living and leisure activities and for clinicians assessing and treating children with DCD.     

Handwriting process and product characteristics of children diagnosed with developmental coordination disorder

Deficits in handwriting performance limit the school participation of children with developmental coordination disorder (DCD). The aim of this study was to compare the handwriting process and product characteristics of children with DCD to those of typically developing (TD) children in order to determine the best means of differentiation between the groups. Participants were 40 children, from 7 to 10 years old. The experimental group consisted of 20 children who met the criteria of DCD, and the control group consisted of 20 age- and gender-matched controls. The children were asked to perform three graded writing tasks on an electronic tablet, which was part of a computerized handwriting evaluation system (ComPET), in order to obtain measures of their handwriting process. The children's handwriting product was then evaluated by the Hebrew Handwriting Evaluation (HHE). Results showed significant differences between the groups for the handwriting process measures (on-paper and in-air time, mean pressure) and for the handwriting product characteristics (global legibility, number of letters erased or overwritten, spatial arrangement, and number of letters written in the first minute). The discriminant analysis yielded a high significant discrimination (80-90%), with the 'number of letters erased or overwritten' variable as the most differentiating variable (-.67). We concluded that an evaluation of both handwriting process and product characteristics among children with DCD provides a more comprehensive picture of their deficits. Using this method may enable practitioners to focus on children's main deficits and to tailor intervention methods so as to prevent academic underachievement and its consequences on their emotional well-being.     

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

ObjectiveThere 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).MethodsWe 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.ResultsFirst, 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.     

Rites of passage: understanding participation of children with developmental coordination disorder

Children with developmental coordination disorder (DCD) experience difficulty participating in the typical activities of childhood and are known to have a more sedentary pattern of activities than their peers. Little research has been done to investigate the impact of these deficits on the lives of children with DCD and the importance of their participation in the typical activities of childhood. This qualitative study explored the impact of the disorder and the importance of participation for children with DCD from the perspective of the parent. Twelve in-depth interviews were conducted with parents of children with DCD who attended a university clinic specializing in using the Cognitive Orientation to daily Occupational Performance (CO-OP) approach, a cognitive-based intervention. Findings revealed that incompetence in everyday activities had serious negative effects for the children. Conversely, intervention that was focused on enablement at the activity and participation level had a significant positive impact on the children's quality of life. Emerging themes highlighted the notion that performance competency played an important role in being accepted by peers and being able "to be part of the group". As well, parents reported that successful participation built confidence in their children and allowed them to try other new activities. The World Health Organization's International Classification of Functioning, Disability, and Health provides a unique framework for analyzing and understanding the impact of the physical disability on the lives of families with children with DCD. Results illustrate how intervention that focuses on enabling children to choose their own functional goals in the area of physical activity has important implications for enabling participation and building the social networks of children with DCD.     

Role of visual-perceptual skills (non-motor) in children with developmental coordination disorder

The purposes of this study were to examine test-retest reliability of the Test of Visual-Perceptual Skills (Non-Motor)-Revised (TVPS-R), to explore motor-free visual-perceptual skills, and to categorize subtypes thereof in children with developmental coordination disorder (DCD). One hundred and seventy-eight children, aged 9 and 10 years, identified as having DCD with the Movement Assessment Battery for Children (M-ABC), were assessed, along with 200 typically developing children. The results showed good test-retest reliability for the total perceptual quotient scores of the TVPS-R, but not for all subtests. Children with DCD performed significantly poorer compared to typically developing children on the visual-perceptual test, but the deficits were not common to all children with DCD. This study supported the stance that we should consider the heterogeneous characteristics of children with DCD when designing experimental studies or developing educational interventions.     

Standing balance of children with developmental coordination disorder under altered sensory conditions

Maintenance of standing balance requires that sensory inputs be organized with the motor system. Current data regarding the influence of sensory inputs on standing balance in children with developmental coordination disorder (DCD) are limited. This study compared the influence of sensory organization and each sensory input on the standing stability between a group of 20 children, 4-6 years old, with DCD and an age- and gender-matched control group of 20 children. Three types of visual inputs (eyes open, eyes closed, or unreliable vision) and two types of somatosensory inputs (fixed or compliant foot support) were varied factorially to yield six sensory conditions. Standing stability was measured with a Kistler force plate for 30s and expressed as the center of pressure sway area. The results showed that the standing stability of the children with DCD was significantly poorer than that of the control children under all sensory conditions, especially when the somatosensory input was unreliable (compliant foot support) compared to when it was reliable (fixed foot support). The effectiveness of an individual sensory system, when it was the dominant source of sensory input, did not significantly differ between the groups. The results suggest that children with DCD experience more difficulty coping with altered sensory inputs, and that such difficulty is more likely due to a deficit in sensory organization rather than compromised effectiveness of individual sensory systems.     

Working memory, reading, and mathematical skills in children with developmental coordination disorder

The aim of the present study was investigate the relationship between working memory and reading and mathematical skills in 55 children diagnosed with developmental coordination disorder (DCD). The findings indicate a pervasive memory deficit in all memory measures. In particular, deficits observed in visuospatial short-term and working memory tasks were significantly worse than in the verbal short-term memory ones. On the basis of these deficits, the sample was divided into high and low visuospatial memory ability groups. The low visuospatial memory group performed significantly worse on the attainment measures compared to the high visuospatial memory group, even when the contribution of IQ was taken into account. When the sample was divided into high and low verbal working memory ability groups, verbal working memory skills made a unique contribution to attainment only when verbal IQ was taken into account, but not when performance IQ was statistically controlled. It is possible that the processing demands of the working memory tasks together with the active motor component reflected in the visuospatial memory tasks and performance IQ subtest both play a crucial role in learning in children with DCD.     

A pilot trial of a cognitive treatment for children with developmental coordination disorder

This pilot study compared a new treatment approach, the Cognitive Orientation to daily Occupational Performance (CO-OP) to the Contemporary Treatment Approach (CTA) to treating children with Developmental Coordination Disorder (DCD). CO-OP emphasises problem-solving strategies and guided discovery of child and task specific strategies. CTA encompasses a variety of approaches, such as neuromuscular, multi-sensory, and biomechanical, focusing on motor aspects of skill acquisition. Twenty children with a mean age of 9.05 years (S.D. = 1.23) participated in the study. All children had normal intelligence, scored below the 15th percentile on a standardised test of motor ability, and demonstrated motor difficulties significant enough to warrant referral for treatment. Pre- and post-measures included the Canadian Occupational Performance Measure (COPM), the Vineland Adaptive Behavior Scales (VABS), the Bruininks-Oseretsky Test of Motor Proficiency (BOTMP), the Developmental Test of Visual-Motor Integration-Revised (VMI), the motor items of the Self-Perception Profile for Children (SPPC), and the Performance Quality Rating Scale (PQRS). In both groups, treatment goals were child-chosen. Both treatments lead to improved COPM self-ratings of performance and satisfaction; however, improvements in the CO-OP group were greater than those in the CTA group. These results were paralleled by PQRS scores, and the Motor scores on the VABS, but not on the BOTMP measures. This outcome still needs replication as no control group was involved and because of the occurrence of pre-treatment differences between the CO-OP and CTA groups on relevant measures. Follow-up data indicated that children who received CO-OP tended to experience greater long-term maintenance of their motor goals and acquired strategies; follow-up parent-report rated CO-OP treatment as more useful than CTA treatment. Self-report, observer report, standardised assessment, and follow-up all demonstrated the effectiveness of the CO-OP approach, supporting the use of CO-OP and suggesting further investigation of this new cognitive intervention.     

Identifying play characteristics of pre-school children with developmental coordination disorder via parental questionnaires

Motor coordination deficits that characterize children with Developmental Coordination Disorder (DCD) affect their quality of participation. The aim of the current study was to identify play characteristics of young children with DCD, compared to those of children with typical development in three dimensions: activity and participation, environmental factors and children’s impairments.MethodSixty-four children, aged four to six years, participated. Thirty were diagnosed as having DCD; the remaining 34 children were age, gender and socioeconomic level matched controls with typical development. The children were evaluated by the M-ABC. In addition, their parents completed a demographic questionnaire, the Children’s Activity Scale for Parents (CHAS-P), the Children’s Leisure Assessment Scale for preschoolers (CLASS-Pre), and My Child’s Play Questionnaire (MCP).ResultsChildren with DCD performed significantly poorer in each of the four play activity and participation domains: variety, frequency, sociability, and preference (CLASS-Pre). Furthermore, their environmental characteristics were significantly different (MCP). They displayed significantly inferior performance (impairments) in interpersonal interaction and executive functioning during play, in comparison to controls (MCP). Moreover, the children’s motor and executive control as reflected in their daily function as well as their activities of daily living (ADL) performance level, contributed to the prediction of their global play participation.DiscussionThe results indicate that the use of both the CLASS-Pre and the MCP questionnaires enables the identification of unique play characteristics of pre-school children with DCD via parents’ reports. A better insight into these characteristics may contribute to theoretical knowledge and clinical practice to improve the children’s daily participation.     

Developmental dyspraxia and developmental coordination disorder

This article discusses the role developmental dyspraxia plays in developmental coordination disorder (DCD), based upon a review of literature on apraxia, developmental dyspraxia, and DCD. Apraxia and dyspraxia have often been equated with DCD. However, it is argued that apraxia and dyspraxia primarily refer to the problems of motor sequencing and selection, which not all children with DCD exhibit. The author proposes to distinguish developmental dyspraxia from DCD. Other issues discussed include the assessment, etiology, and treatment of developmental dyspraxia and DCD, and the relationship between DCD and learning disabilities. A research agenda is offered regarding future directions to overcome current limitation.     

Static balance and developmental coordination disorder

The development of static balance is a basic characteristic of normal motor development. Most of the developmental motor tests include a measure of static balance. Children with a developmental coordination disorder (DCD) often fail this item. Twenty-four children at risk for DCD with balance problems (DCD-BP) and 24 matched control children in the age range of 6-12 years participated in a detailed study of balance control. Additional groups of children (6-7 years, N=25; 10-11 years, n=16; with M-ABC scores >15th percentile) were selected randomly to study developmental changes in balance control in the age range of interest. Three experiments were conducted to examine developmental and clinical differences in the control of static balance. In the first, we measured the excursion of the centre of pressure (force-plate) in conditions with and without vision while standing still on one or two legs for 20 s. In the second experiment, EMGs were measured while standing on one leg. In the third experiment, in which only a subgroup of the DCD-BP and matched control children participated, a short unexpected force in the back lightly perturbed normal standing and EMG and force-plate responses were measured during balance recovery. In conditions of one-leg stance, children were not always able to maintain balance. Only epochs of stable postural control (7.5-20 s) were analysed. The results showed improvement of static balance with age, but only subtle differences between the DCD and control groups. Centre of pressure measures differed in the more difficult conditions. DCD-BP children had more difficulty standing on one leg with eyes closed. While standing on the non-preferred leg the EMGs of the DCD-BP children showed slightly more co-activation of the muscles of lower and upper leg. Perturbation of standing resulted in longer duration of recovery in the first trial in this group. Apparently DCD children learn to compensate for the perturbation within a few trials as well as control children do. The clear improvement with age shows that our measures of balance control are sensitive to detect changes. The general conclusion that may be drawn from this study is that under normal conditions static balance control is not a problem for children with DCD. Only in difficult or novel situations they seem to suffer from increased postural sway as a result of non-optimal balance control.     

Visual information and the control of reaching in children: a comparison between children with and without developmental coordination disorder

Three experiments were performed on reach and grasp in 9- to 10-year-old children (8 controls and 8 with developmental coordination disorder [DCD]). In normal reaching, children in the DCD group were less responsive to the accuracy demands of the task in controlling the transport component of prehension and spent less time in the deceleration phase of hand transport. When vision was removed as movement began, children in the control group spent more time decelerating and reached peak aperture earlier. Children in the DCD group did not do that, although, like the control group, they did increase grip aperture in the dark. When depth cues were reduced and only the target or only the target and hand were visible, children in the control group used target information to maintain the same grip aperture in all conditions, but DCD children behaved as if the target was not visible. Throughout the studies, the control group of 9- to 10-year-olds did not produce adult-like adaptations to reduced vision, suggesting that they had not yet attained adult-like integration of sensory input. Compared with control children, children with DCD did not exhibit increased dependence on vision but showed less recognition of accuracy demands, less adaptation to the removal of vision, and less use of minimal visual information when it was available.     

Contributions of trunk muscles to anticipatory postural control in children with and without developmental coordination disorder

Current evidence suggests that movement quality is impacted by postural adjustments made in advance of planned movement. The trunk inevitably plays a key role in these adjustments, by creating a stable foundation for limb movement. The purpose of this study was to examine anticipatory trunk muscle activity during functional tasks in children with and without developmental coordination disorder (DCD). Eleven children with DCD (age 7 to 14 years) and 11 age-matched, typically-developing children performed three tasks: kicking a ball, climbing stairs, and single leg balance. Surface electromyography (EMG) was used to examine the neuromuscular activity of bilateral transversus abdominis/internal oblique, external oblique and L3/4 erector spinae, as well as the right tibialis anterior and rectus femoris muscles. Onset latencies for each muscle were calculated relative to the onset of rectus femoris activity. In comparison to the children with DCD, the typically-developing children demonstrated earlier onsets for right tibialis anterior, bilateral external oblique, and right transversus abdominis/internal oblique muscles. These results suggest that anticipatory postural adjustments may be associated with movement problems in children with DCD, and that timing of both proximal and distal muscles should be considered when designing intervention programs for children with DCD.