Development of bilateral motor control in children with developmental coordination disorders

Effect of verbal cues on the coupling and stability of anti-phase bimanual coordination pattern in children with probable developmental coordination disorder

The study of the emergence and stability of bimanual and interlimb coordination patterns in children with Developmental Coordination Disorder (DCD) has shown that they encounter greater difficulties in coupling their limbs compared to typically developing (TD) children. Verbal cues have been identified as strategies to direct children's attention to more relevant task information, thus potentially improving motor performance. Consequently, this study investigated the effect of providing verbal cues on the execution of bimanual tasks in children with and without probable DCD. Twenty-eight children aged 9-10, matched by age and gender, were divided into two groups: pDCD [n = 14] and TD. The children performed bilateral trajectory movements with both hands (horizontal back-and-forth), holding a pen on a tablet, in anti-phase (180°) coordination pattern, in two conditions: No cues and Verbal cues. In the last condition, children received verbal cues to maintain the anti-phase pattern even with an increase in hand oscillation frequency. Relative phase and variability of relative phase between the hands were calculated for analysis of pattern coupling and stability. Hand cycles, movement amplitude, and tablet pressure force were calculated to analyze pattern control parameters. All these variables were compared between groups and conditions. The results indicated that despite the pDCD group showing greater variability in the anti-phase coordination pattern compared to the TD group, both groups performed better in the Verbal cues than the No cues condition. Furthermore, the pDCD group exhibited more hand movement cycles and applied greater pressure force compared to the TD group, suggesting different motor control strategies during the bimanual task. It is suggested that the use of verbal cues during bimanual task execution improves children's performance, potentially by promoting interaction between attention, as a cognitive function, and intrinsic coordination dynamics, thereby reducing variability in the perceptual-motor system.

Associations Between Coordination and Wearable Sensor Variables Vary by Recording Context but Not Assessment Type

Motor coordination is an important driver of development and improved coordination assessments could facilitate better screening, diagnosis, and intervention for children at risk of developmental disorders. Wearable sensors could provide data that enhance the characterization of coordination and the clinical utility of that data may vary depending on how sensor variables from different recording contexts relate to coordination. We used wearable sensors at the wrists to capture upper-limb movement in 85 children aged 6-12. Sensor variables were extracted from two recording contexts. Structured recordings occurred in the lab during a unilateral throwing task. Unstructured recordings occurred during free-living activity. The objective was to determine the influence of recording context (unstructured versus structured) and assessment type (direct vs. indirect) on the association between sensor variables and coordination. The greatest associations were between six sensor variables from the structured context and the direct measure of coordination. Worse coordination scores were associated with upper-limb movements that had higher peak magnitudes, greater variance, and less smoothness. The associations were consistent across both arms, even though the structured task was unilateral. This finding suggests that wearable sensors could be paired with a simple, structured task to yield clinically informative variables that relate to motor coordination.

Children with developmental coordination disorder have less variable motor unit firing rate characteristics across contractions compared to typically developing children

Introduction

Understanding the nuances of neuromuscular control is crucial in unravelling the complexities of developmental coordination disorder (DCD), which has been associated with differences in skeletal muscle activity, implying that children with DCD employ distinct strategies for muscle control. However, force generation and control are dependent on both recruitment of motor units and their firing rates and these fine details of motor function have yet to be studied in DCD. The purpose of this study was therefore to compare motor unit characteristics in a small muscle of the hand during low level, handgrip contractions in typically developing (TD) children and children with DCD.

Methods

Eighteen children (9 TD vs. 9 DCD) completed a series of manual handgrip contractions at 10 ± 5% of their maximum voluntary contraction. High density surface electromyography was used to record excitation of the first dorsal interosseus muscle. Recorded signals were subsequently decomposed into individual motor unit action potential trains. Motor unit characteristics (firing rate, inter-pulse interval, and action potential amplitude) were analysed for contractions that had a coefficient variation of <10%.

Results and Discussion

This study found few differences in average motor unit characteristics (number of motor units: TD 20.24 ± 9.73, DCD 27.32 ± 14.00; firing rate: TD 7.74 ± 2.16 p.p.s., DCD 7.86 ± 2.39 p.p.s.; inter-pulse interval: TD 199.72 ± 84.24 ms, DCD 207.12 ± 103 ms) when force steadiness was controlled for, despite the DCD group being significantly older (10.89 ± 0.78 years) than the TD group (9.44 ± 1.67 years). However, differences were found in the variability of motor unit firing statistics, with the children with DCD surprisingly showing less variability across contractions (standard deviation of coefficient of variation of inter-pulse interval: TD 0.38 ± 0.12, DCD 0.28 ± 0.11). This may suggest a more fixed strategy to stabilise force between contractions used by children with DCD. However, as variability of motor unit firing has not been considered in previous studies of children further work is required to better understand the role of variability in motor unit firing during manual grasping tasks, in all children.

Unimanual and bimanual motor performance in children with developmental coordination disorder (DCD) provide evidence for underlying motor control deficits

Much of our understanding of motor control deficits in children with developmental coordination disorder (DCD) comes from upper limb assessments focusing on the dominant limb. Here, using two robotic behavioural tasks, we investigated motor control in both the dominant and non-dominant limbs of children with DCD. Twenty-six children with diagnosed DCD (20 males; mean age 10.6 years ± 1.3 years) and 155 controls were included in this cross-sectional study. Participants completed a visually guided reaching task with their dominant and non-dominant limbs and a bimanual object hitting task. Motor performance was quantified across nine parameters. We determined the number of children with DCD who fell outside of the typical performance range of the controls on these parameters and compared the DCD and control groups using ANCOVAs, accounting for age. Children with DCD demonstrated impairments in six out of nine parameters; deficits were more commonly noted in the non-dominant limb. Interestingly, when looking at individual performance, several children with DCD performed in the range of controls. These findings indicate that children with DCD display deficits in motor control in both the dominant and non-dominant limb and highlight the importance of including detailed assessments of both limbs when investigating children with DCD. They also demonstrate the variability in motor control performance evidenced by children with DCD.

Effects of practice on visual finger-force control in children at risk of developmental coordination disorder

BACKGROUND

The production of finger force control is essential for a large number of daily activities. There is evidence that deficits in the mechanisms of accuracy and control of finger force tasks are associated with children's motor difficulties.

OBJECTIVE

To compare the effect of practice of an isometric finger force/torque task between children with significant movement difficulty and those with no difficulty movement.

METHODS

Twenty-four children aged between 9 and 10 years (12 at risk of developmental coordination disorder and 12 with no movement difficulty - typically developing children) were asked to produce finger force/torque control in a continuous and constant 25% of maximum voluntary torque with visual feedback during 15s. Practice was given during five consecutive days with 15 trials per day. After the practice with visual feedback, children were asked to perform five trials without visual feedback. In these trials, feedback was removed 5s after the start of the trial.

RESULTS

Typically developing children were consistently more accurate in maintaining finger force/torque control than those children at risk of developmental coordination disorder. Children from both groups improved the performance in the task according to practice sessions. Also, children at risk of developmental coordination disorder poorly performed the task without visual feedback as they did when visual feedback was available.

CONCLUSION

The present study give support to the idea that movement difficulty is associated with finger force/torque control and children at risk of developmental coordination disorder can improve finger force/torque control with practice when visual feedback is available.

Inter-limb coordination and control in boys with and without DCD in ball catching

The purpose of the study was to examine the nature of inter-limb coordination and control, exhibited by ten boys with (M=10.5 years, SD=1.0) and without Developmental Coordination Disorder (DCD), in a ball catching task across different ball speeds. In line with the predictions of coordinated structure theory boys who were typically developing preserved strong and effective temporal relations when catching balls in baseline and fast conditions. Boys with DCD exhibited temporal symmetry in baseline but not in fast attempts, where the decoupling was uniformed across the group, coinciding with failures on ≥ 50% of the attempts. In terms of stability, no differences in intra-individual variability were observed between the groups. The analysis of spatial and temporal adaptations showed that boys who were typically developing, in essence, covered the same "ground" by decreasing their movement time. The opposite was true for boys with DCD who contacted the ball closer to the body, while failing to adapt the velocity of their hands. Taken together, both groups exhibited strong and stable coordinative relations, in a steady-state but not in a fast condition, where all boys with DCD failed to preserve the desired symmetry. This decoupling also coincided with different and less effective spatio-temporal adaptations at the effector level. Thus, it appears that movement control, hence flexibility of their synergistic relations, represents a movement limiter for boys with DCD who exhibit specific balls skills issues, at inter-limb level of organization. It should be noted, however, that large intra-group variance observed across some variables warrants caution when interpreting the aggregate data.

Motor fMRI and cortical grey matter volume in adults born very preterm

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Adults born very preterm (VPT) and controls performed a motor fMRI task.

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VPT adults activated the cerebellum and adjacent temporal lobe more than controls.

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Grey matter volume in the premotor cortex was smaller in the VPT group.

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Grey matter volume in premotor cortex explained 33% of activation in the cerebellum.

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Preterm birth is associated with functional neuroanatomical alterations in adulthood.

The primary aim of this study was to investigate the functional neuroanatomy of motor planning, initiation and execution in a cohort of young adults (mean age 20 years) who were born very preterm (VPT; <33 weeks of gestation), as these individuals are at increased risk of experiencing neuromotor difficulties compared to controls. A cued motor task was presented to 20 right-handed VPT individuals and 20 controls within a functional magnetic resonance imaging (fMRI) paradigm. Whole-brain grey matter volume was also quantified and associations with functional data were examined. Despite comparable task performance, fMRI results showed that the VPT group displayed greater brain activation compared to controls in a region comprising the right cerebellum and the lingual, parahippocampal and middle temporal gyri. The VPT group also displayed decreased grey matter volume in the right superior frontal/premotor cortex and left middle temporal gyri. Grey matter volume in the premotor and middle temporal clusters was significantly negatively correlated with BOLD activation in the cerebellum. Overall, these data suggest that preterm birth is associated with functional neuronal differences that persist into adulthood, which are likely to reflect neural reorganisation following early brain injury.

Emergence and stability of interlimb coordination patterns in children with developmental coordination disorder

The purpose of this study was to investigate the emergence and stability of coordination patterns in children with developmental coordination disorder (DCD) when performing a rhythmic interlimb coordination task on rigid (floor) and elastic (mini-trampoline) surfaces. Twelve typically developing (TD) children and 12 children with DCD were required to clap while jumping under different conditions: in a chosen pattern - Free; when the feet touched the surface - Clapping-surface; when the body reached the maximum jumping height - Clapping-jump; and when the feet touched the surface and the body reached the maximum jumping height - Clapping-both. The results showed that the coordination pattern of children with DCD was more variable in the Free, Clapping-surface, and Clapping-jumping conditions and more variable on the mini-trampoline than on the floor under the Free condition when compared with the TD children. Clapping-jumping was more difficult to perform than Clapping-surface for both groups. These findings suggest that the children with DCD were less capable of rhythmically coordinating the jumping-clapping task because they used a type of exploratory strategy regarding the physical properties of the surfaces, whereas the TD children used a type of adaptive strategy displaying behavior that was more consistent across the tasks/environmental demands.

Development and validation of the computerized bilateral motor coordination test

The purpose of this study was to explore the validity of computerized scaling of bilateral, motor coordination in children 4-6 years of age. There were 623 children with an average age of 5, years and 2 months (standard deviation=6 months) that participated. The 290 girls (46.5%) and 333, boys (53.5%) were from a purposive sample taken from public and private kindergartens in Taiwan. The computerized bilateral motor coordination test included two subtests, bilateral coordination, movements and projected actions. The motion analysis, with mark position and contour motion, was, used to collect important variables from the subtests. Using the judgments of the experts as the, criterion standards, the accuracy, sensitivity, and specificity of the tool were calculated to evaluate the, validity of the computerized bilateral motor coordination test. The accuracy, sensitivity, and, specificity of the bilateral coordination movement subtests were on average 83.9%, 86.4%, and 83.1%, respectively. The accuracy, sensitivity, and specificity of the projected action subtests were on average, 90.5%, 88.1%, and 90.4%, respectively. The computerized bilateral motor coordination tests showed, an average accuracy of 86.3%, a sensitivity of 87.0%, and a specificity of 85.8%. The computerized, bilateral motor coordination test could be a valuable tool when used to identify problems of bilateral, motor coordination and in permitting early intervention to remedy these problems.

Early deprivation impairs the development of balance and bilateral coordination

This study examined balance and bilateral coordination skills in a sample of internationally adopted, post-institutionalized (PI) children. We compared the performance of these PI children to two age-matched groups. One was a group of children who were internationally adopted from foster care (FC). The second group consisted of non-adopted children being raised in their birth families, who served as controls (Control). Both PI and FC children scored lower than control children on balance, while PI children scored lower than both FC and control children on bilateral coordination. These results suggest that aspects of institutional rearing impact the development of bilateral coordination, while factors common to internationally adopted children other than institutionalization impact the development of balance. Region of birth (Asia, Latin/South America, Russia/Eastern Europe) did not moderate associations between institutional duration and bilateral coordination.

Age as a factor in sensory integration function in Taiwanese children

OBJECTIVE

Sensory integration progresses along a normal developmental sequence. However, few studies have explored how age difference affects the way sensory integration functions in Taiwanese children as they develop. Therefore, this study aims to pinpoint the role of age in sensory integration.

METHOD

A purposive sampling plan was employed. The study population comprised 1,000 Chinese children aged 36 to 131 months (mean = 74.48 months, standard deviation = 25.69 months). Subjects were scored on seven subsets of the Test of Sensory Integration Function (TSIF). An analysis of variance (ANOVA) was used to identify differences between four age groups (ages 3-4, 5-6, 7-8, and 9-10 years), in the categories of the TSIF.

RESULTS

ANOVA revealed that age is a significant factor in each of the seven tasks of sensory integration associated with various stages of development. The effect of age was significant in all four groups for the subscale of Bilateral Integration Sequences. The function of sensory integration for the children aged 5-8 years did not produce statistically significant results for the subscale of Postural Movement, Sensory Discrimination, Sensory Seeking, or Attention and Activity. For the subscale of Sensory Modulation and Emotional Behavior, the effect of age was significant in only group 1 (children aged 3-4 years) and group 2 (children aged 5-6 years).

CONCLUSION

There was significant difference between group 1 and group 2 for seven categories. Significant differences were contributed by the differences from group 1 (3-4 years) and group 4 (9-10 years) in five subscales (Postural Movement, Bilateral Integration Sequences, Sensory Discrimination, Sensory Seeking, and Attention and Activity). There were three developmental trends in the seven categories of the TSIF.

Altered postural control strategies and sensory organization in children with developmental coordination disorder

The postural control of children with and without developmental coordination disorder (DCD) was compared under conditions of reduced or conflicting sensory input. Twenty-two children with DCD (16 males, 6 females; mean age 7 years 6 months, SD 1 year 5 months) and 19 children with normal motor development were tested (13 males, 6 females; mean age 6 years 11 months, SD 1 year 1 month). Standing balance, sensory organization and motor control strategy were evaluated using the sensory organization test (SOT). The results revealed that children with DCD had lower composite equilibrium scores (p<.001), visual ratios (p=.005) and vestibular ratios (p=.002) than normal children in the control group. No significant between-group difference in their average somatosensory ratio was observed. Additionally, children with DCD had lower motor strategy scores (swayed more on their hips) than the normal children when forced to depend on vestibular cues alone to balance (p<.05). We conclude that children with DCD had deficits in standing balance control in conditions that included reduced or conflicting sensory signals. The visual and vestibular systems tended to be more involved in contributing to the balance deficits than the somatosensory system. Moreover, children with DCD tended to use hip strategy excessively when forced to rely primarily on vestibular signals to maintain postural stability.

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.

Can children with developmental coordination disorder adapt to task constraints when catching two-handed?

PURPOSE

To compare the nature and extent of inter and intralimb coupling during two-handed catching and the effect of manipulating task constraints in children with Developmental Coordination Disorder (DCD) and their typically developing peers (AMC).

METHOD

Twenty children aged 7 - 10 years, ten with DCD and 10 AMC attempted to catch a ball ten times in condition 1 (C1), ball to the midline; condition 2 (C2), ball to the left shoulder and condition 3 (C3), ball to the right shoulder. Both 3D kinematic data and video data were collected.

RESULTS

Children with DCD caught fewer balls than the AMC children, regardless of age or condition (p <or= 0.001). Children with DCD demonstrated a higher degree of linkage between limbs in C1 and a lower degree of between limb coupling in C2 and C3 when compared to the AMC (p <or= 0.05). Differences between the AMC7 - 8 and AMC9 - 10 group were found with respect to interlimb coupling.

CONCLUSIONS

The influence of manipulating task constraints and the individual nature of children with DCD must be considered by those involved in rehabilitation. By doing so, children with DCD may search for appropriate motor solutions to many functional movement tasks required for everyday life.

Physical fitness in children with developmental coordination disorder

The protective effects of physical activity and fitness on cardiovascular health have clearly been shown among normally developed children. However data are currently lacking pertaining to children with developmental coordination disorder (DCD). The purpose of this study was to examine differences in fitness measures, body composition, and physical activity among children with and without DCD. A cross-sectional design was implemented examining 261 children (118 girls, 143 boys) ages 4-12 years (mean age 7.8 +/- 1.9 years). Children were categorized as having DCD if they scored less than or equal to the 5th percentile (n=71) or between the 6th and the 15th percentile (n=5) on the Movement Assessment Battery for Children (MABC; Henderson & Sugden, 1992). The typically developing children had scores between the 16th and the 50th percentile (n=16) or above the 50th percentile (n=3) on the MABC. The age-related body mass index was used to characterize body composition. Physical fitness was assessed with a 6-min run, 20-m sprint, jump-and-reach test, medicine ball throw, curl-ups, and sit-and-reach test. Physical activity was estimated with a questionnaire. The percentage of overweight and obese children ages 10-12 years were significantly higher in the DCD groups (severe: 50%, moderate: 23.1%) than in the typically developing groups (medium: 5.6%, high: 0%; p < .05). Significant interactions (MABC x Age Group) were found for the fitness tests (p values < .05), except flexibility; whereby specifically, compared to the children in the typically developing groups children in the DCD groups ages 4-6 years achieved significantly worse results for the 20-m sprint, and children of the DCD groups ages 10-12 years achieved significantly worse results for the 6-min run, jump-and-reach test, and medicine ball throw. The study demonstrates poorer performance in fitness tests with high demands on coordination in children with DCD compared to their typically developing peers. Furthermore, the differences in fitness increased with age between children in the DCD groups versus the typically developing groups.

Motor and gestural performance in children with autism spectrum disorders, developmental coordination disorder, and/or attention deficit hyperactivity disorder

Motor and gestural skills of children with autism spectrum disorders (ASD), developmental coordination disorder (DCD), and/or attention deficit hyperactivity disorder (ADHD) were investigated. A total of 49 children with ASD, 46 children with DCD, 38 children with DCD+ADHD, 27 children with ADHD, and 78 typically developing control children participated. Motor skills were assessed with the Bruininks-Oseretsky Test of Motor Proficiency Short Form, and gestural skills were assessed using a test that required children to produce meaningful gestures to command and imitation. Children with ASD, DCD, and DCD+ADHD were significantly impaired on motor coordination skills; however, only children with ASD showed a generalized impairment in gestural performance. Examination of types of gestural errors revealed that children with ASD made significantly more incorrect action and orientation errors to command, and significantly more orientation and distortion errors to imitation than children with DCD, DCD+ADHD, ADHD, and typically developing control children. These findings suggest that gestural impairments displayed by the children with ASD were not solely attributable to deficits in motor coordination skills.

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.

MRI measurements of the pons and cerebellum in children born preterm; associations with the severity of periventricular leukomalacia and perinatal risk factors

Our purpose was to measure the size of the pons and cerebellum in preterm babies with periventricular leukomalacia (PVL), and to study their relationship with the severity of PVL and with perinatal risk factors. We examined 33 premature children, mean gestational age 31 weeks, range 26-36 weeks with PVL on MRI, and 27 full-term controls. On MRI at 0.4-5.5 years (mean 1.4 years) we measured the area of the corpus callosum and vermis, the anteroposterior diameter of the pons and the volume of the cerebellum. The area of the corpus callosum was used as a marker of white matter loss and PVL severity. All regional brain measurements except that of the vermis were significantly lower in patients than controls: corpus callosum (mm(2)): 239.6+/-92.5 vs 434.8+/-126.8, P <0.01; pons (mm): 14.8+/-3.0 vs 17.9+/-1.4, P <0.01]; cerebellum (cm(3)): 68.2+/-31.6 vs 100.6+/-28.3, P <0.01; vermis (mm(2)): 808.1+/-292.2 vs 942.2+/-246.2, NS. Significant reduction in the area of the vermis: 411.3+/-203.3 vs 935+/-252.6 mm(2); cerebellar volume: 16.3+/-12.5 vs 96.6+/-20.2 mm(3); and the diameter of the pons: 10.1+/-2.2 vs 17.5+/-1.3 mm ( P<0.01) were observed in seven children with gestational age < or =28 weeks, severe hypotension and large patent ductus arteriosus (PDA). There was a significant correlation between the duration of mechanical ventilation and the size of the vermis, pons and cerebellum (R=-0.65, -0.57 and -0.73, respectively, P <0.01).

Developmental coordination disorder in extremely low birth weight children at nine years

Developmental coordination disorder (DCD) is defined as an impairment in the development of motor coordination that interferes with academic achievement or activities of daily living (DSM-IV). DCD has been reported to affect 5% to 9% of children in the normal population. This study describes the prevalence of DCD in a cohort of extremely low birth weight children (ELBW, < or = l800 g) at 8.9 years of age, from which were excluded children with major impairments. Seventy-three children were included in the study group, along with 18 term-born, socially matched controls. Of the 73 ELBW children, 37 (51%) were classified as having DCD. ELBW children with DCD also had significantly lower Performance IQ (PIQ) scores and were more likely (43%) to have a learning difficulty in arithmetic than ELBW children who did not have DCD. This study found that DCD is a common problem in school-aged ELBW children.

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.

Cognitive and motor function and the size of the cerebellum in adolescents born very pre-term

Individuals born before 33 weeks' gestation are at risk of brain lesions, which have the potential to disrupt subsequent neurodevelopment. As a result they manifest an increased incidence of neuromotor signs and cognitive deficits, which can still be detected in adolescence. The cerebellum is known to be involved in both the co-ordination of movement and in cognitive processes. We therefore set out to establish whether cognitive and motor impairments in adolescents born very pre-term are associated with abnormalities of the cerebellum as revealed by volumetric analysis of brain MRI scans. The volume of the whole cerebellum was determined manually using a PC-based Cavalieri procedure in 67 adolescents born very pre-term and 50 age-matched, full-term born controls. Cognitive and neurological assessments were performed at 1, 4, 8 and 14-15 years of age as part of the long-term follow-up of the pre-term subjects. The pre-term-born subjects had significantly reduced cerebellar volume compared with term-born controls (P<0.001). This difference was still present after controlling for potential confounders. There was no association between cerebellar volume and motor neurological signs. However, there were significant associations between cerebellar volume and several cognitive test scores, in particular the Wechsler Intelligence Scale for Children-Revised, the Kaufman Assessment Battery for Children and the Schonnel reading age. This provides further evidence implicating the cerebellum in cognition and suggests that cerebellar abnormalities may underlie some of the cognitive deficits found in individuals born very pre-term.