Visuomotor performance of normal and clumsy children. I: Fast goal-directed arm-movements with and without visual feedback

Variability in coordination patterns in children with developmental coordination disorder (DCD)

High motor variability is an often-found characteristic of Developmental Coordination Disorder (DCD). Still, the role of high motor variability in DCD needs further examination. This study focused on variability in coordination patterns, which is essential considering that DCD is a coordination disorder. We examined variability in coordination patterns of the arm over repetitions of trials in goal-directed reaching movements. This variability was partitioned into variability that does not affect the index fingertip position (V_ucm) and variability that does affect the index fingertip position (V_ort). This study aimed to increase the understanding of motor variability in DCD by comparing V_ucm and V_ort between children with DCD and typically developing (TD) children in a goal-directed reaching task. Twenty-two children (eleven with DCD) ages 6-11 performed 30 reaching movements. The Uncontrolled Manifold method was used to quantify V_ucm and V_ort. Results showed that children with DCD had more V_ucm than TD children while V_ort was similar between groups, showing that coordination patterns in children with DCD are more variable, but interestingly, this higher variability does not affect performance. This study indicates that high motor variability in DCD is not necessarily negative. Possible roles of motor variability in DCD are discussed.

Influence of the Perspectives on the Movement of One-Leg Lifting in an Interactive-Visual Virtual Environment: A Pilot Study

Background

Numerous studies have confirmed the feasibility of active video games for clinical rehabilitation. To maximize training effectiveness, a personal program is necessary; however, little evidence is available to guide individualized game design for rehabilitation. This study assessed the perspectives and kinematic and temporal parameters of a participant’s postural control in an interactive-visual virtual environment.

Methods

Twenty-four healthy participants performed one-leg standing by leg lifting when a posture frame appeared either in a first- or third-person perspective of a virtual environment. A foot force plate was used to detect the displacement of the center of pressure. A three-way mixed factor design was applied, where the perspective was the between-participant factor, and the leg-lifting times (0.7 and 2.7 seconds) and leg-lifting angles (30°and 90°) were the within-participant factors. The reaction time, accuracy of the movement, and ability to shift weight were the dependent variables.

Results

Regarding the reaction time and accuracy of the movement, there were no significant main effects of the perspective, leg-lifting time, or angle. For the ability to shift weight, however, both the perspective and time exerted significant main effects, F(1,22) = 6.429 and F(1,22) = 13.978, respectively.

Conclusions

Participants could shift their weight more effectively in the third-person perspective of the virtual environment. The results can serve as a reference for future designs of interactive-visual virtual environment as applied to rehabilitation.

Similarities and dissimilarities between the movement ABC-2 and the Zurich neuromotor assessment in children with suspected developmental coordination disorder

An established tool for the assessment of motor performance in children with developmental coordination disorder (DCD) is the Movement-ABC-2 (M-ABC-2). The Zurich Neuromotor Assessment (ZNA) is also widely used for the evaluation of children's motor performance, but has not been compared with the M-ABC-2. Fifty-one children (39 males) between 5 and 7 years of age with suspected DCD were assessed using the M-ABC-2 and the ZNA. Rank correlations between scores of different test components were calculated. The structure of the tests was explored using canonical-correlation analysis. The correlation between total scores of the two motor tests was reasonable (0.66; p<0.001). However, ZNA scores were generally lower than those of M-ABC-2, due to poor performance in the fine motor adaptive component and increased contralateral associated movements (CAM). The canonical-correlation analysis revealed that ZNA measures components like pure motor skills and CAM that are not represented in the M-ABC-2. Furthermore, there was also no equivalent for the aiming and catching items of the M-ABC-2 in ZNA. The two tests measure different motor characteristics in children with suspected DCD and, thus, can be used complementary for the diagnosis of the disorder.

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.

Reaching and grasping a moving target is impaired in children with developmental coordination disorder

PURPOSE

To investigate the performance of reaching and grasping a moving target in children with developmental coordination disorder (DCD).

METHODS

Sixteen children with DCD and 11 age-matched controls were instructed to reach and grasp a toy car that was sliding down an 8° or 15° slope. Reaction time (RT), movement time (MT), and peak force (PF) were recorded.

RESULTS

Children with DCD failed 35% of total test trials. Within the successful trials, children with DCD had significantly longer RTs and MTs and generated larger PF than control children (P < .05). When the slope increased from 8° to 15°, both groups of children could adjust MT and PF (P < .01).

CONCLUSION

Children with DCD were slower and generated larger force to reach and grasp a moving target than their age-matched peers. However, the ability to modify the MT and grip force appeared to be preserved in children with DCD.

Relationship of Visual Perceptual Deficit and Motor Impairment in Children with Developmental Coordination Disorder

The study explored the relations of visual perceptual deficits and motor impairments in 60 children with Developmental Coordination Disorder (120.8 ± 4.0 mo.) and 60 controls (121.0 ± 5.3 mo.), who were matched by sex (29 boys and 31 girls) and age. They were separately assessed on fine and gross motor-dexterity tasks of the Movement Assessment Battery for Children, static balance and reaction time of lower extremities with eyes open or closed, and the Test of Visual-Perceptual Skills–Revised. Analysis showed the children with Developmental Coordination Disorder performed significantly worse than the control group, but only the visual perception and motor skills with timed responses were significantly correlated. When visual information was controlled, no significant correlation was noted, so motor-free visual perception appears to be significantly related to motor performance having a speed component in these children.

Optimizing assisted communication devices for Children with motor impairments using a model of information rate and channel capacity

For children who depend on devices to communicate, the rate of communication is a primary determinant of success. For children with motor impairments, the rate of communication may be limited by inability to contact buttons or cells rapidly or accurately. It is, therefore, essential to know how to adjust the device interface in order to maximize each child's rate of communication. The optimal rate of communication is determined by the channel capacity, which is the maximum value of the information rate for all possible keyboard button or cell layouts for the communication device. We construct a mathematical model for the information rate based on the relationship between movement time and the number of buttons per screen, the size of the buttons, and the length of a sequence of buttons that must be pressed to communicate each word in the vocabulary. We measure the parameters of the model using a custom-programmed touchscreen interface in 10 children with disorders of arm movement due to cerebral palsy who use a DynaVox communication device. We measure the same parameters in 20 healthy control subjects. We show that the model approximates the measured information rate and that the information rate is lower in children with motor impairments compared with control subjects. The theory predicts that for each child there is a combination of button size and number that maximizes the predicted information rate and thereby achieves communication at the optimal channel capacity. Programming communication devices with each child's predicted optimal parameters improved the communication rate in five of the ten children, compared with programming by professionals. Therefore, measurement of information rate may provide an assessment of the effect of motor disorders on success in assisted communication. Optimization of the information rate may be useful for programming assisted communication devices.

Goal-directed upper limb movements by children with and without DCD: a window into perceptuo-motor dysfunction?

BACKGROUND AND PURPOSE

Developmental co-ordination disorder (DCD) occurs in at least 6% of school-aged children. Researchers agree that motor co-ordination problems evident in DCD are, in part, the result of perceptual and cognitive processes, but the limited research available remains inconclusive. The present study investigated perceptual-motor abilities, with regard to vision, kinaesthesia and cross-modal judgement, in children with and without DCD.

METHOD

A cross-sectional study design was used. Nine children, aged six years (+/- six months) with DCD, and nine children without DCD, matched for age and gender, participated in the study. The children were required to point with the preferred hand to a target in three different positions under four sensory conditions, either with or without vision. Three-dimensional motion analysis was used to investigate trajectory lengths, endpoint error and movement time. The results were analysed using a generalized linear mixed model to examine the systematic effects of group, target position and task.

RESULTS

Compared with children without DCD, the children with DCD produced larger endpoint errors, greater movement times and longer trajectories. Children in both groups produced larger endpoint errors, greater movement times and longer trajectories in non-visually guided aiming versus visually guided aiming tasks.

CONCLUSIONS

Children with DCD moved more slowly, with longer movement trajectories and were less accurate than children without DCD when aiming to all target positions under all sensory conditions. The greatest error and trajectory length occurred for both groups when aiming movements were performed in the absence of vision. As children in the DCD group had difficulties with movement executed under kinaesthetic or visual control, the results indicate that the normal advantage of vision displayed by children without DCD is not apparent, and visual and kinaesthetic problems may be present in children with DCD.

Early identification and risk management of children with developmental coordination disorder

PURPOSE

The purpose of this study was to determine the motor control issues, motor learning differences, and secondary impairments of children with developmental coordination disorder (DCD) and to explore physical therapists' contribution to their early management.

SUMMARY OF KEY POINTS

DCD is a condition involving limitations in gross motor, postural, and/or fine motor performance that is not attributable to other neurological disorders. Manifestation is varied across children and depends, in part, on their level of anticipatory motor control, response to specific task demands, and ability to attend to feedback to obtain flexible, adaptive movement solutions. Children with DCD rely primarily on vision for feedback, frequently use "fixing" strategies, and exhibit limited motor repertoires. As a result of their movement problems, they tend to avoid physical activity and are prone to secondary impairments, including decreased strength and power.

CLINICAL IMPLICATIONS AND RECOMMENDATIONS

Physical therapists can 1) use their keen observational skills to identify children with DCD earlier in life and 2) use their knowledge of the secondary impairments and movement difficulties to work with families to engage children in continuous movement activities to maintain strength and power and thus obtain the physical, social, and psychosocial benefits of physical activity.

The association of abnormal cerebellar function in children with developmental coordination disorder and reading difficulties

Children with developmental coordination disorder/dyspraxia (DCD) are at high risk of reading and writing delay. The difficulties with motor skills are heterogeneous and many children have features of poor cerebellar function, reflected in problems with posture, balance and fast accurate control of movement. This study confirmed a high level of parental reporting of reading and writing delay in a clinical group of 23 children with DCD, defined on the basis of both clinical examination and standardized testing of motor function. Direct measurement of reading delay, identified still further children in the group. Those children with reading delay had associated findings typical of phonological awareness difficulties. The children also underwent a standardized test of neurological function and although they all had difficulties with cerebellar function, no distinctive pattern emerged for those whose presentation was complicated by delayed reading and writing. Both the children with DCD and 136 typically developing children, completed the pilot parental questionnaire on gross motor skills. The three skills of catching a ball, jumping on a moving playground roundabout and handwriting, distinguished the children with DCD. This study therefore confirms that children with DCD should be assessed for difficulties in phonological awareness. Additionally, children aged between 7 and 12 years are on the whole, highly competent in a range of gross motor skills and further study might determine whether a simple parental questionnaire might detect children who would benefit from further assessment. The study also suggests that all the children with DCD have cerebellar dysfunction and further work with a larger group might determine particular patterns associated with reading delay.

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.

Clinical and research diagnostic criteria for developmental coordination disorder: a review and discussion

The aim of this review was to investigate the selection criteria used in the past in studies of children with developmental motor problems (excluding those suffering from neurological dysfunctions such as cerebral palsy, muscular dystrophy, etc.). We therefore conducted an extensive analysis of 176 publications. First, an overview of the main characteristics of these studies (terminology, population, type and purpose) and the selection criteria that are reported in these publications are presented. Following this, the DSM-IV selection criteria for developmental coordination disorder (DCD) are contrasted with the selection criteria reported in 41 publications that have used this terminology to classify the children. The results of this comparison show that the inclusion criteria are largely followed, albeit with little consistency concerning selection instruments and quantitative cut-offs, while adherence to the exclusion criteria is not common practice. Strengths and weaknesses of the DSM-IV criteria, complementary to the previous discussion by Henderson and Barnett in the HMS special issue on DCD in 1998 on this same topic, are discussed. The results of the review also show that many studies have used additional selection criteria related to the specific research questions of the study concerned. In the broader context of clinical practice as well as basic research, the latter result suggests the usefulness of a distinction between Clinical Diagnostic Criteria and Research Diagnostic Criteria. This distinction helps to develop a unifying view on the use of diagnostic criteria for research and clinical practice. We conclude with a number of recommendations concerning the selection criteria for children with DCD.

Development of bilateral motor control in children with developmental coordination disorders

This research examined behavioral (i.e. movement time) and neuromuscular (EMG) characteristics of unilateral and bilateral aiming movements of children with normal motor development and children with developmental coordination disorders (DCD). Two age groups of children were studied: 6 to 7, and 9 to 10 year olds. Bilateral aiming movements involved moving the two hands to targets of either (1) the same amplitude--symmetrical bilateral movements, or (2) different amplitudes--asymmetrical bilateral movements. Unilateral aiming movements involved moving one hand to either near or far targets associated with that hand. In general, unilateral and bilateral movement times were slower in younger than older children, and in children with DCD than children with normal motor development. Our neuromuscular data suggest that the faster movement times that typically accompany increasing age in children may be the result of a change in the capacity to initiate antagonist muscle contractions. The prolonged burst of agonist activity and delayed onset of antagonist activity observed in children with DCD may contribute to their inability to produce fast, accurate unilateral movements. On both symmetrical and asymmetrical bilateral aiming movements, children with DCD had more performance errors and greater temporal inconsistencies between neuromuscular (EMG) parameters and behavioral (movement time) parameters than children with normal motor development. These new neuromuscular data suggest that there are important differences in the way the motor control systems of children with and without DCD organize bilateral aiming responses.

Planning and execution of action in children with and without developmental coordination disorder

Ninety-five children from six English primary schools were identified on the basis of the Movement Assessment Battery for Children (Movement ABC) as having developmental coordination disorder (DCD) and, together with age- and ability-matched controls, were given three tasks that involved proprioception in the control and discrimination of limb position, and two tasks that involved planning for end state comfort after a bar was grasped and turned. The children in the DCD group performed less well on the majority of the proprioceptive tasks, but did not differ from controls in planning of grip selection. There was an improvement in grip planning with age. The results are contrasted with research indicating that people with autism do have a difficulty with planning grip selection.

Covert orienting of visuospatial attention in children with developmental coordination disorder

It is still unclear whether impairments in visuospatial processing in children with developmental coordination disorder (DCD) are a consequence of their motor deficits or are independent of them. In two experiments, 20 children with DCD and 20 matched controls were tested on the covert orienting of a visuospatial attention task (COVAT). Experiment 1 used a COVAT with peripheral cues and an 80% probability that targets would appear at the cued location. While the results suggested a deficit in the disengage operation of orienting covert attention for the DCD group, they were difficult to reconcile with models of covert orienting and the results of past research. Experiment 2 tested subjects on two new versions of the COVAT: the first used peripheral cues and no probability information (exogenous mode), and the second used central cues and an 80% probability that targets would appear at the cued location (endogenous mode). The DCD group displayed attentional orienting deficits only for the endogenous mode. These results suggest that impairments in the endogenous control of visuospatial attention are independent of motor deficits in DCD.

Visual-perceptual and phonological factors in the acquisition of literacy among children with congenital developmental coordination disorder

Much research has shown that children with congenital developmental coordination disorder (CDCD) have marked impairments in the perception of visual-spatial information, a deficit which has been assumed to be causally related to difficulties that many CDCD children experience when learning to read and spell. However, current research in reading disability suggests that poor reading is mainly related to difficulties with the processing of phonological information or with metaphonological ability, not to visual-perceptual deficits. This study aimed to explore the relationship between reading achievement and the visual-perceptual, phonological and general cognitive ability of CDCD children. Twenty-eight children with a mean age of 8.3 years were tested on motor coordination, language, general ability, visual discrimination, visual-motor integration, phoneme awareness, phoneme discrimination, reading and spelling. Results showed that phoneme awareness was the most strongly related to reading and spelling performance, and that visual discrimination showed no relationship to reading ability, although it was related to spelling performance, phonological awareness, and motor coordination. These results suggest that CDCD children who have difficulty with the acquisition of literacy may suffer from visual-perceptual problems and metaphonological deficits, but these problems are differentially related to reading and spelling.

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.

Current perspectives on minimal cerebral dysfunction

Children with minimal cerebral dysfunction (MCD) are a large client group for many paediatric physiotherapists. The increasing number of research papers published in the area of MCD are often complex and difficult to interpret because the children to whom they refer do not form an easily definable, homogeneous group and their prognosis is unclear. This review presents a summary of current findings about MCD and poses a number of questions about physiotherapy intervention. The need for physiotherapists to validate their role in the management of children with MCD is emphasised.

Visuomotor performance of normal and clumsy children. II: Arm-tracking with and without visual feedback

Tracking performance was investigated in normal and clumsy children in two age-groups, six to seven and 10 to 11 years. Target signals moving unpredictably along a straight line had to be tracked, both with and without visual feedback. Performance was described in three ways: (1) performance in the low-frequency range (LF); (2) the delay between target signal and tracking movement (DL); and (3) a measure of tracking quality or over-all similarity in the shape of target signal and tracking movement (Q). Clumsy children in both age-groups had a lower tracking quality (Q) and longer delay (DL) than the normal children. Disturbances in the regulation of attention seemed to affect tracking performance, particularly of the six- to seven-year-old clumsy children. There was no significant difference between normal and clumsy children in the effect of visual feedback on tracking performance. This suggests that clumsiness is not linked to disturbance of integration of visual feedback information and motor processes.