Visual, kinaesthetic and cross-modal judgements of length by normal and clumsy children

The Effect of a Table Tennis Exercise Program With a Task-Oriented Approach on Visual Perception and Motor Performance of Adolescents With Developmental Coordination Disorder

In this study we investigated the effects of an 8-week table tennis exercise program with a task-oriented approach on visual perception and motor performance of 31 adolescents with developmental coordination disorder (DCD). The participants were identified by their teachers as having greater difficulty than their peers (450 students from three Korean middle schools) in physical education (PE) classes. On the Bruininks-Oseretsky Test of Motor Proficiency-2, these adolescents scored below the 15th percentile and showed difficulties in performing daily life activities due to motor performance problems; they did not have physical defects, intellectual or neurological impairments, or Attention Deficit Hyperactivity Disorder. Of 98 prospective adolescents with PE difficulties, we obtained personal assent and parents' informed consent from 54, and 31 of these met screening criteria for DCD through the Developmental Coordination Disorder Questionnaire-Korean. This final group was divided in non-random fashion (based on the proximal geographic grouping of the children's schools) between an experimental group (n = 16) and a control group (n = 15). The experimental group participated in the 8-week task-oriented table tennis training program with three 90-minute sessions per week, while the control group only participated in regular PE classes twice per week. We measured participants' visual perception and motor performance in the same environment before and after the intervention program. Participants' visual perception was significantly more improved in the experimental group than the control group, with specific improved skills in visual-motor search, visual-motor speed, figure-ground, and visual closure; copying and perceptual constancy skills did not improve significantly. In addition, total motor performance and motor sub-skills, including fine manual control, manual coordination, body coordination, strength, and agility were significantly more improved in the experimental group than in the control group. Thus, our task-oriented table tennis exercise program was of greater assistance than general PE classes for improving visual perception and motor performance in adolescents at risk of DCD.

Navigating through apertures: perceptual judgements and actions of children with Developmental Coordination Disorder

Passing through a narrow gap/aperture involves a perceptual judgement regarding the size of the gap and an action to pass through. Children with DCD are known to have difficulties with perceptual judgements in near space but whether this extends to far space is unknown. Furthermore, in a recent study it was found that adults with DCD do not scale movements when walking through an aperture in the same way as their peers. The current study, therefore, considered perceptual judgements and motor behaviour of children with DCD while looking at or walking through apertures. Twenty‐nine children with DCD and 29 typically developing (TD) children took part. In Experiment 1, participants completed a perceptual task, where they made passability judgements. Children with DCD showed a significantly smaller critical ratio (aperture size at which a participant first rotates the shoulders to pass through) compared to their TD peers. In Experiment 2, participants completed an action task where they walked through the same apertures. Children with DCD showed a significantly larger critical ratio than TD peers when body size alone was accounted for. Taken together these results suggest that perception within a static context is different from that within a dynamic context for children with DCD. However, despite this difference we have demonstrated a clear relationship between perception and action in children with DCD. A video abstract of this article can be viewed at: https://youtu.be/SABXFrAJtF8

Handwriting: A Perceptual-Motor Disturbance in Children with Myelomeningocele

An explanation for the handwriting difficulties experienced by children with spina bifida myelomeningocele was sought within the framework of a closed-loop theory of motor skill acquisition. The handwriting performance of 34 children (16 boys and 18 girls) aged 6.16 to 13.42 years was detailed with available norms. Regression analyses were then performed for the five handwriting components of speed, alignment, letter formation, spacing, and size. The regressions for speed, alignment, and letter formation reached statistical significance. For speed, age provided the greatest explanation of performance (R2 = .62, p = .008). Alignment was explained substantially by age, handedness, scholastic aptitude, and kinesthesia (R2 = .55, p = .03). Letter formation was determined primarily by age and kinesthesia (R2 .71, p = .001,). The overall regression was not significant for spacing (R2 = .39, p = .30), or size (R2 = .35, p = .43), although a significant single degree of freedom was detected for the effect of age. These findings are discussed in terms of skill acquisition theory.

Visual and Motor Sequencing in Normal and Clumsy Children

An information-processing approach was used to investigate motor performance differences between normal children and children designated as clumsy. The focus of this study was on the planning stages of motor skill. Following a motor skills screening test, 38 children 6 to 9 years old were divided into a control group, consisting of children who had passed the screening and an experimental group consisting of children who had failed the screening. The children then performed three tasks involving visual and motor sequencing selected for this study: (a) visual sequencing and short-term recall of visual stimuli, (b) visual sequencing and long-term recall of skilled motor acts, and (c) visual sequencing and short-term recall with motor reproduction. Results of the study indicated that children who had failed the motor skills screening did significantly worse than the control group on the three tasks. Implications for occupational therapy are discussed in terms of the importance of perception in motor skill performance.

Differentiation of motor planning ability in normal and learning-disabled children

Twenty children with learning disabilities (LD) and 40 normal children aged from seven to 12 years were studied to examine the relation between motor planning ability and learning disabilities. It was expected that children with LD would score significantly lower on a test of praxis than normal children, and different types of apraxia would be identified in LD children. In addition, the relation between apraxia and writing disability, speaking disability, distractibility, hand dominance and socio-economic factors was explored. Results indicated that the motor planning ability of children with LD is disturbed and that different types of apraxia occur. The child's failure on these tests has an influence on academic performance and daily life.

Aspects of Motor Performance and Preacademic Learning

This study examined preschool children's performance on a pursuit tracking task in relation to specific performance on motor and cognitive measures of preacademic skill development. Fifty children, ages 4.3 to 5.8 years were tested using the Miller Assessment for Preschoolers (MAP)and number/counting items. High and low performance groups were designated based on performance on the MAP, individual MAP spatial items as well as number/counting items. Groups were compared based on their performance on a pursuit tracking task. Results indicated that the low performance number/counting concept group demonstrated a significantly slower average response time, overshoot movement time and reaction time. These findings offer support for an underlying perceptual-motor difficulty in children exhibiting low scores on preacademic tasks of mathematical concepts. The low MAP and spatial groups demonstrated a significantly higher rate of overshoots, suggesting difficulty in processing visual spatial information.

Timing and Force Characteristics of Muscle Activity: Postural Control in Children with and Without Developmental Coordination Disorders

Setting appropriate timing and force parameters of muscle activity is a significant part of producing skillful movement behavior: Data reported here suggest that an important characteristic of children with developmental coordination disorders (DCD) is inconsistency and lack of precision in regulating timing and force characteristics of muscle activity to correct for perturbations to balance. Children with and without DCD stood on a moveable platform. Balance was perturbed under fully redundant sensory conditions and under conditions where vision was removed or vestibular input was modified. EMG activity in tibialis anterior and quadriceps leg muscles was recorded. Children with normal motor development produced less force than children with DCD. Children with DCD tended to rely on proximal muscle activity to respond to perturbations to balance and, in contrast to children with normal motor development, modified temporal but not force characteristics of muscle activity when the sensory framework for balance was modified.

Developmental coordination disorders: state of art

In the literature, descriptions of children with motor coordination difficulties and clumsy movements have been discussed since the early 1900s. According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), it is a marked impairment in the development of fine or global motor coordination, affecting 6% of school-age children. All these children are characterized for developmental coordination disorder (DCD) in motor learning and new motor skill acquisition, in contrast to adult apraxia which is a disorder in the execution of already learned movements. No consensus has been established about etiology of DCD. Intragroup approach through factor and cluster analysis highlights that motor impairment in DCD children varies both in severity and nature. Indeed, most studies have used screening measures of performance on some developmental milestones derived from global motor tests. A few studies have investigated different functions together with standardized assessments, such as neuromuscular tone and soft signs, qualitative and quantitative measures related to gross and fine motor coordination and the specific difficulties -academic, language, gnosic, visual motor/visual-perceptual, and attentional/executive- n order to allow a better identification of DCD subtypes with diagnostic criteria and to provide an understanding of the mechanisms and of the cerebral involvement.

Development of multisensory reweighting is impaired for quiet stance control in children with developmental coordination disorder (DCD)

Background

Developmental Coordination Disorder (DCD) is a leading movement disorder in children that commonly involves poor postural control. Multisensory integration deficit, especially the inability to adaptively reweight to changing sensory conditions, has been proposed as a possible mechanism but with insufficient characterization. Empirical quantification of reweighting significantly advances our understanding of its developmental onset and improves the characterization of its difference in children with DCD compared to their typically developing (TD) peers.

Methodology/Principal Findings

Twenty children with DCD (6.6 to 11.8 years) were tested with a protocol in which visual scene and touch bar simultaneously oscillateded medio-laterally at different frequencies and various amplitudes. Their data were compared to data on TD children (4.2 to 10.8 years) from a previous study. Gains and phases were calculated for medio-lateral responses of the head and center of mass to both sensory stimuli. Gains and phases were simultaneously fitted by linear functions of age for each amplitude condition, segment, modality and group. Fitted gains and phases at two comparison ages (6.6 and 10.8 years) were tested for reweighting within each group and for group differences. Children with DCD reweight touch and vision at a later age (10.8 years) than their TD peers (4.2 years). Children with DCD demonstrate a weak visual reweighting, no advanced multisensory fusion and phase lags larger than those of TD children in response to both touch and vision.

Conclusions/Significance

Two developmental perspectives, postural body scheme and dorsal stream development, are provided to explain the weak vision reweighting. The lack of multisensory fusion supports the notion that optimal multisensory integration is a slow developmental process and is vulnerable in children with DCD.

Neuromotor deficits in developmental coordination disorder: evidence from a reach-to-grasp task

Developmental coordination disorder (DCD) has been classified as a specific learning disability, nonetheless the underlying cognitive mechanisms are still a matter of discussion. After a summary of the main hypotheses on the principal neuromotor causes of DCD, this study applies a causal model framework to describe the possible coexistence of more than one deficit in this disorder. For this purpose, kinematic analysis was applied to an ecological task, the reach-to-grasp action, introducing the manipulation of three variables: vision, distance and object size. After a thorough neurological and neuropsychological evaluation, 9 children with DCD (7-9 years old) were selected and compared to 27 age-matched control children. The results suggest that children with DCD have a normal neurological characterization of the reaching and grasping movements, in terms of proximal to distal action, but their grasping aperture (MGA) was always wider with respect to controls, particularly when vision was not allowed. In addition, the performance of children with DCD was always slower, more dependent on vision and more variable than that of controls. The MGA of children with DCD could be explained by a deficit in the internal construction of movement for a forward model, while slowness could be related to a control problem in the neuronal firing of the muscles. The idea of a possible coexistence of these two deficits is discussed in accordance to a causal model framework and also addressed considering recent neurophysiologic evidences.

Developmental delay syndromes: psychometric testing before and after chiropractic treatment of 157 children

OBJECTIVE

This study presents a case series of 157 children with developmental delay syndromes, including the conditions such as dyspraxia, dyslexia, attention-deficit hyperactivity disorder, and learning disabilities who received chiropractic care.

CLINICAL FEATURES

A consecutive sample of 157 children aged 6 to 13 years (86 boys and 71 girls) with difficulties in reading, learning, social interaction, and school performance who met these inclusion criteria were included.

INTERVENTION AND OUTCOMES

Each patient received a multimodal chiropractic treatment protocol, applied kinesiology chiropractic technique. The outcome measures were a series of 8 standardized psychometric tests given to the children by a certified speech therapist pre- and posttreatment, which evaluate 20 separate areas of cognitive function, including patient- or parent-reported improvements in school performance, social interaction, and sporting activities. Individual and group data showed that at the end of treatment, the 157 children showed improvements in the 8 psychometric tests and 20 areas of cognitive function compared with their values before treatment. Their ability to concentrate, maintain focus and attention, and control impulsivity and their performance at home and school improved.

CONCLUSIONS

This report suggests that a multimodal chiropractic method that assesses and treats motor dysfunction reduced symptoms and enhanced the cognitive performance in this group of children.

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.

Impaired re-weighting of sensory feedback for maintenance of postural control in children with developmental coordination disorder

To further the understanding of postural control impairments seen in children with developmental coordination disorder (DCD) and the effect of these impairments on motor performance in these children, 30 children with and without DCD (mean age=9 years, 7 months +/- 1 year, 10 months) were administered the Movement Assessment Battery for Children (M-ABC), Wechsler Abbreviated Scale of Intelligence and the Sensory Organization Test. Analyses of covariance revealed that children with DCD had greater difficulty maintaining postural control when visual and somatosensory feedback were compromised in sensory conflict environments (p=.031). Group differences in postural control were independent of age. Additionally, no correlation was seen between motor performance on the M-ABC and postural control measures for the Sensory Organization Test. Our results demonstrate that impaired ability to utilize vestibular feedback while re-weighting somatosensory and visual feedback for orientation may be responsible, in part, for the postural control impairments observed in some children with DCD.

Attention disengagement in children with developmental coordination disorder

PURPOSE

Previous research has shown that children with Developmental Coordination Disorder (DCD) have poorly developed strategies for allocating attention. This study examines the allocation of attention and integration of visuo-spatial and motor systems in children with DCD in a motor (look+hit condition) and a motor-free (look condition) task.

METHOD

Three groups of control children were used to compare the performance of a group of children with DCD. Children were seated in front of a central fixation point and six peripheral targets, and were asked to look at or hit targets when illuminated. Saccade/hand movement latencies were measured on gap trials (gap between fixation offset and target onset) and overlap trials (fixation offset and target onset overlapped).

RESULTS

DCD children were not slower than controls to disengage attention during the look condition. However, during the look+hit condition the DCD children showed a prolonged disengagement period, which was also seen in younger control children.

CONCLUSIONS

The results suggest that DCD children may have deficits in the allocation of attention for action, in both the speed of onset of a movement and the accuracy of the movement. It is concluded that attention disengagement may contribute to problems of visuo-motor integration in DCD.

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.

Disorders of motor development (clumsy child syndrome)

This presentation will focus on motor competence, the clumsy child, perceptual deficits in clumsy children and possible neurological dysfunction in this group of children. Motor competence not only allows children to carry out everyday practical tasks, but it is also an important determinant of their level of self-esteem and of their popularity and status in their peer group. Research has shown that about 6-10% of children have motor competences well below the norm. It is unusual for motor problems to simply disappear over time. In the absence of intervention the syndrome is likely to manifest itself. In the clinical literature attempts have been made to establish causal links between surface manifestations of clumsiness and underlying perceptual deficits. In this respect the attention is primarily directed towards the concept of inter- and intra-modal matching, particularly with respect to vision and proprioception, an ability deemed to underlie many real-life motor skills. Neurobehavioural model of inter- and intra-modal matching and deficit model is presented. Findings from studies using this paradigm are discussed and it is argued that clumsiness must be seen as a neurological dysfunction (insufficiency).

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.

Do 'clumsy' children have visual recognition problems?

OBJECTIVE

Visual recognition by 8-year-old children with hand-eye co-ordination problems (HECP), and by a control group of children without such problems was tested using a task of visual closure.

DESIGN

The task required the children to identify common objects from an incomplete visual presentation.

RESULT

As predicted, it was found that the HECP children, who were designated as such solely on the basis of their motor difficulties, identified significantly fewer correct objects than their control counterparts.

CONCLUSIONS

This finding raises the possibility that the visual processing problems of clumsy children contribute to, or even strongly determine, not only their movement problems but also their learning difficulties.

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.

Developmental coordination disorder: a review of research on subtypes and comorbidities

The interest in Developmental Coordination Disorder (DCD) has grown considerably over the last decade. Nevertheless, its etiology and prognosis are still poorly understood. The idea is growing that DCD may not be a uniform disorder. This review summarizes research on DCD, with a particular focus on subtype and comorbidity studies. The main message of the paper is that, in order to understand the etiology and prognosis of DCD, we need to have a better understanding of its nature. This requires an awareness of the existence of subtypes and comorbidities. Current theories on comorbidity phenomena are discussed in terms of their possible merit for the development of the field. Particular attention is given to the Automatization Deficit Hypothesis, a theory based on research on dyslexia.

Do 'clumsy' children have visual deficits

Visual processing by 10-year-old children diagnosed on the basis of standardised tests as having developmental 'clumsiness' syndrome, and by a control group of children without motor difficulties, was tested using three different psychophysical tasks. The tasks comprised a measure of global motion processing using a dynamic random dot kinematogram, a measure of static global pattern processing where the position of the target was randomised, and a measure of static global pattern processing in which the target position was fixed. The most striking finding was that the group of clumsy children, who were diagnosed solely on the basis of their motor difficulties, were significantly less sensitive than the control group on all three tasks of visual sensitivity. Clumsy children may have impaired visual sensitivity in both the dorsal and ventral streams in addition to their obvious problems with motor control. These results support the existence of generalised visual anomalies associated with impairments of cerebellar function.

Hand preference in children with developmental coordination disorders: cause and effect?

Inter- and intra-modal matching by eight-year-old children diagnosed as having hand-eye coordination problems (HECP) and categorized as left-handed, together with a left-handed control group of children without such problems, were tested using a manual sensory matching task. The task required the children to locate target pins, visually (seen target), proprioceptively (felt target) or in combination (felt and seen target), while matching to the located target was always carried out without vision. Performance was superior when the target was located visually or visually/proprioceptively for both groups of children. These results question the conclusion that intra-modal will always be more accurate than inter-modal matching. When the combined scores for both hands were analyzed, the HECP children showed inferior performance to the control children in both inter- and intra-modal matching. Separate right and left hand analyses, demonstrated that the differences between the HECP group and control children could be accounted for by lowered performances when the right hand (nonpreferred) was used to match the located target position. Putative neurological disorders related to the development of the hemisphere controlling the nonpreferred hand (left hemisphere) are invoked to account for the poor performance with the nonpreferred hand of the HECP children.

A longitudinal study of motor ability and kinaesthetic acuity in young children at risk of developmental coordination disorder

Several studies have linked poor kinaesthetic ability with poor motor coordination in school-aged children. However, few studies have investigated kinaesthesis in younger children. The aim of this study was to determine if preschool aged children who have been identified as at risk of developing developmental coordination disorder (DCD) have poorer kinaesthetic ability than matched controls. Kinaesthetic ability and performance IQ were examined in a group of children aged between 4 and 5 years. Following individual assessment of 291 children, 31 were identified as at risk of DCD at this age. One year later, 30 of these children were retested, and 23 were still found to be at risk. These children were matched on verbal IQ, age and sex with control children and their performance compared on the kinaesthetic acuity test (KAT) [D.J. Livesey and N.A. Parkes, Aust. J. Psychol., 47 (1995) 160] and three subtests of the WPPSI-R performance IQ (D. Wechsler, Manual for the Wechsler preschool and primary scale of intelligence--revised, Psychological Corporation, New York, 1989). Both the KAT and the performance subtest scores were found to be significantly poorer in the children at risk of DCD. Follow-up testing one year later showed that both groups improved their kinaesthetic acuity score although the control children remained significantly better than the children with poor motor coordination.

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.

The search for subtypes of DCD: is cluster analysis the answer?

Studies using cluster analysis as a method to identify distinct subtypes of developmental coordination disorder (DCD) have been inconclusive leading some authors to conclude that the method of cluster analysis should be abandoned while others call for the validation of previously defined subtypes. The objective of the current study was to examine the use of cluster analysis as a method of searching for subtypes of DCD to gain a better understanding of how different samples and different measures influence the interpretation of results. The paper provides a detailed review of three commonly cited cluster analytical studies and then explores the possible reasons for the discrepant results by replicating the approach with a different clinical sample. The results highlight the impact of different measures on cluster structure and the importance of adoption of a common standard to facilitate interpretation across studies.

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.

Proximal versus distal control in proprioceptively guided movements of motor-impaired children

Two groups of 7-year-old children diagnosed as motor-impaired (N = 6) or as controls (N = 6) were required to perform a task that involved locating targets under a table-top with one hand while attempting to match the position of the target with the other, on the table-top (intra-modal matching), always without visual control. The experimental design involved three different conditions: proximal control (P), distal control (D) or both (PD). Target distance errors were analysed in terms of absolute (AE) and variable error. When the scores for each hand were combined, the motor-impaired group showed inferior mean performance (AE scores) on all three conditions as compared with the control children and were also more variable in their behaviour. Analyses of scores achieved with the right and the left hand separately, however, demonstrated that the difference could largely be attributed to the scores obtained when matching with the right hand in conditions P and PD, and matching with the left hand in condition D. Possible explanations of these findings are discussed in the context of 'delay' (developmental lag) and/or 'deviancy' (neurological lesion/disconnection).

Relation of visual perception and visual-motor integration for clumsy children

The purpose of this study was to examine the relationship between visual perception and visual-motor integration in 30 normal children compared to 30 clumsy children. Difficulty in visual perception, as assessed by the Test of Visual-Perceptual Skills, accounts for about half the variance in the clumsy children's performance in visual-motor integration, as assessed by the Developmental Test of Visual Motor Integration. In contrast, the correlation between scores on these tests for normal control children was low and not significant. These results suggest that visual perception and visual-motor integration may be separate functions in normally developing children. When considering clumsy children, however, these functions cannot be considered as two independent skills.

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.

Fragile X, iron, and neurodevelopmental screening in 8 year old children with mild to moderate learning difficulties

OBJECTIVE

To examine the value of neurodevelopmental examination, fragile X testing, iron studies, and other screening procedures in children with mild to moderate learning difficulties.

DESIGN

A cross sectional case-control study.

SUBJECTS

A 34% random sample (n = 130) of children with mild to moderate learning difficulties born between 01/07/83 and 30/06/84 and resident in North and West Belfast. Controls were 130 children without learning difficulties matched for age and geographical area.

RESULTS

The prevalence of mild to moderate learning difficulties in North and West Belfast was 16%; 115 (89%) of the learning difficulties group and 80 (58%) of the control group consented to participate. Children in the learning difficulties group scored significantly lower in neurodevelopmental testing and were more likely to fail their audiometry assessment than controls. Children in the learning difficulties group were also more likely to be anaemic and had lower serum iron and transferrin saturation than controls. No cases of fragile X were identified. Thyroid function tests and urinary amino acids were all within normal limits There were no significant differences in anthropometry, head circumference, or formal neurological examinations.

CONCLUSIONS

Children with learning difficulties are more likely to be neurodevelopmentally immature and iron depleted than controls. Iron depletion should be aggressively sought and treated. The role for routine assessment for fragile X, thyroid function tests, and amino acid chromatography is doubtful.

Kinaesthetic sensitivity and motor performance of children with developmental co-ordination disorder

Earlier research has demonstrated a number of variables contributing to motor co-ordination problems (clumsiness) in children. The present study examined the contribution of kinaesthetic sensitivity in determining level of motor co-ordination in children. 20 children with significant movement problems were compared with 20 control children matched for age, gender and Verbal IQ. The kinaesthetic perception and memory test from Laszlo and Bairstow's Kinaesthetic Sensitivity test was a powerful measure for distinguishing clumsy from control children. The authors' passive kinaesthetic acuity test did not distinguish the two groups, but did so when administered actively. These results indicate that future research on clumsiness in children should involve more complex tasks, as problems associated with the central translation processes may cause the co-ordination difficulties seen in clumsy children.

Is clumsiness a marker for Asperger syndrome?

Although Asperger syndrome (AS) has been included in the ICD-10 as a distinct category within the pervasive developmental disorders, it is still unclear to what extent it differs from normal-intelligence autism (high-functioning autism; HFA). Persons with AS are said to be particularly clumsy. To test the hypothesis that clumsiness can reliably distinguish AS from autism, the present authors compared 11 patients with AS (ICD-10; 10 males; mean age, 13.6 years; mean IQ, 98) with nine patients with HFA (ICD-10/DSM-III-R; eight males; mean age, 12.9 years; mean IQ, 84). Clumsiness was assessed by the Bruininks-Oseretsky test. Both groups showed problems with coordination and the distribution of standard scores was virtually identical. This suggests that motor clumsiness, as measured by tests of coordination, may not reliably distinguish AS from HFA. However, qualitative differences may occur between the two groups in the manner in which movements are performed. Further research with larger samples may elicit differences into the pattern of motor deficits that occur in autism and AS.

Visuospatial difficulties and clumsiness: on the interpretation of conjoined deficits

Sixteen children with motor difficulties and 16 controls, matched on age, gender and verbal I.Q., were assessed on the Test Of Motor Impairment, various graphic tasks and a measure of visuospatial discrimination. Poor perceptual and motor performance tended to co-occur but contrary to the visuospatial deficit account of clumsiness these abilities were uncorrelated even when attention was restricted to the less proficient children. There was no tendency for the control group's superiority in graphic reproduction to diminish when visual feedback was withheld. Some suggestions are offered concerning more appropriate methods for framing and testing causal deficit hypotheses.

Clumsiness in children: a defect of kinaesthetic perception?

Abnormal clumsiness in otherwise normal children has been recognized for many years, but the causes of this disorder are heterogeneous or unknown. Although equivocal, there is some evidence from reaction time studies suggesting that clumsiness is associated with a defect in perception of movement in the kinaesthetic modality and of motor programming. In this experiment clumsy children and matched controls performed simple and choice kinaesthetic reaction time tasks with either simple or complex responses. The requirement to discriminate between kinaesthetic stimuli was found to increase reaction time more for clumsy than for control children, but increasing response complexity had no significant effect on the reaction time of either group. These results were interpreted as suggesting that clumsiness is associated with a perceptual defect in the kinaesthetic modality, but providing no support for an association of clumsiness with a defect of motor programming.