Does subtype of developmental coordination disorder count: is there a differential effect on outcome following intervention?

It is well known that developmental coordination disorder (DCD) is a heterogeneous condition in which children frequently present with co-occurring conditions in addition to their motor difficulties. This study considered whether there would be a differential effect of a group treatment program on subtypes of perceptual and movement problems or associated co-occurring conditions. A subset of children (n=43) from a larger clinical sample (n=100) with DCD participated in a 214 year cross-over intervention study which followed the cognitive orientation to daily occupational performance (CO-OP) approach. Original subtypes were determined by contrasting the current sample with previously published subtyping studies in DCD [Hoare, D. (1994). Subtypes of developmental coordination disorder. Adapted Physical Activity Quarterly, 11, 158-169; Macnab, J. J., Miller, L. T., & Polatajko, H. J. (2001). The search for subtypes of DCD: Is cluster analysis the answer? Human Movement Science, 20, 49-72]. No advantage was conferred to any subtype although children with more profound and complex difficulties at initial assessment, despite progress following intervention, were most likely to have continuing difficulties at the end of the project.

Stability and change in children with Developmental Coordination Disorder.

BACKGROUND: Children with Developmental Coordination Disorder (DCD) are a heterogeneous group who have a marked impairment in the performance of functional motor skills. Provision for these children is usually made via a paediatrician through occupational or physiotherapy; though with a prevalence rate of 5%, regular provision is rarely possible because of limited professional resources. METHODS: This study covers a period of nearly 4 years and initially examined a group of 31 children first identified as having DCD at 7-9 years of age. The children were observed and assessed before, during and after a total of 16 weeks of intervention carried out by parents and teachers. This was followed by a period of monitoring of performance for 26 of the children in the motor domain plus other abilities such as educational progress and self-concept. Individual children were tracked using a variety of qualitative and quantitative approaches, building up longitudinal whole child profiles. RESULTS: Following intervention, 14 of the 26 children have shown improvement and stability in all areas and no longer display DCD symptoms. Eight children have profiles which have shown variability, with the children moving in and out of the DCD classification, while the remaining four children have consistently scored poorly in their movement skills and in addition received ongoing support in school for academic subjects. CONCLUSIONS: The study has confirmed that children with DCD show varying profiles over a period of time and that the profiles have distinct characteristics related to events in the child's life. This approach to examining stability and change in the progressions of children's difficulties is in keeping with an ecological approach to explaining development with its multilayered influences creating changes.

The influence of perturbing the working surface during reaching and grasping in children with hemiplegic cerebral palsy.

PURPOSE: To examine unimanual and bimanual reaching and grasping in children with hemiplegic cerebral palsy with particular emphasis on the nature and extent of interlimb coupling when the working surface is perturbed. METHOD: Nine children with hemiplegic cerebral palsy and 7 control children with no movement difficulties took part in the study. Children were asked to pick up a cube unimamually and bimanually when the surface it was placed on was either sloping away from the child (Experiment 1) or towards the child (Experiment 2). Both 3D kinematic data and video data were gathered and qualitative descriptions of video data were made. RESULTS: The working surface did indeed influence the nature and extent of interlimb coupling and this varied from participant to participant. Analysis of the displacement data revealed that during the bimanual condition lower trajectories were produced by both the hemiplegic and non hemiplegic sides, especially in Experiment 2. The control group showed little difference between the unimanual and bimanual condition. CONCLUSIONS: Evidence of interlimb coupling is found, these studies support the findings of our previous work that indicates that there are some benefits to performing bimanual movements in children with hemiplegic cerebral palsy.

The influence of object size on discrete bimanual co-ordination in children with hemiplegic cerebral palsy.

PURPOSE: To examine the influence of perturbation of object size on the nature and extent of interlimb coupling in children with hemiplegic cerebral palsy. METHOD: Participants completed a number of trials reaching and grasping unimanually and bimanually to a small cube (1.5 cm) and a large cube (6 cm). Both 3D kinematic data and video data were gathered and qualitative descriptions of the video data were made. RESULTS: It was found that object size did influence the nature and extent of bimanual coupling. As in previous studies this varied from participant to participant and either or a combination of temporal, spatial, or postural coupling was observed. In some cases the hemiplegic hand was influenced by the non hemiplegic hand, while in others it was the reverse. CONCLUSIONS: The influence of context and the individual nature of children with cerebral palsy observed in this paper must be considered by those in rehabilitation. Additionally, the therapist might be able to use the natural tendency to couple to assist the functional control of the hemiplegic side.

Intervention approaches and children with developmental coordination disorder.

Children with Developmental Coordination Disorder (DCD) have a marked impairment in the performance of functional motor skills required to succeed at school. Longitudinal studies show that without intervention children with DCD often do not improve with development and the poor motor behaviour appears to have a detrimental effect on other aspects of functioning such as school achievement, behaviour and self esteem. Outside of clinical situations, there are only a small number of controlled empirical investigations, and from this small number two types of approaches emerge. The first concentrates on processes underlying motor skills and purports to improve areas such as kinesthesis or sensory motor processes. The second concentrates on teaching functional tasks aiming to specifically intervene in the deficient areas. Evaluations of these approaches show that they both work, producing significant improvements over control groups but show no differences between other approaches. It is hypothesized that more general learning principles are producing the effect, such as accurate assessment and tailoring activities to meet the needs of any individual child. Further, it is suggested that work with non-specialists in the motor area, such as teachers and parents, is a way forward with all but the most severely affected children.

A two-step procedure for the identification of children with developmental co-ordination disorder in Singapore.

The prevalence of Developmental Coordination Disorder (DCD) among 6- to 9- year-old Singaporean primary school children was studied from a random sample (N = 427) through a two-step identification procedure contained within Henderson's and Sugden's Movement Assessment Battery for Children. The prevalence rate from this two step procedure was 4% when the first step included the bottom 15% of the random sample. The two-step procedure moves towards fulfilling the diagnostic criteria for DCD set out by the American Psychiatric Association (DSM-IV) and the World Health Organisation (ICD-10) of a serious motor impairment in the development of motor coordination and significant interference with the activities of daily living not due in children to mental retardation or a known physical disability.

Practice variability and transfer of a racket skill.

This study used a forehand hitting task to explore the effect of racket variability on 'out of range' transfer. 48 11-yr.-old girls were randomly assigned to four treatment groups of Random Variability, Blocked Variability, Specific, and Control. The experimental groups had 32 trials for 4 successive days after which all groups were tested on 4 transfer conditions. Retention tests were given after 1, 4, and 8 days and the data were examined for treatment, range, and occasion effects. Analysis showed the superiority of practice over no practice, variable over specific practice, and random over blocked variability for transfer with two 'out of range' dimensions. Accuracy decayed between the transfer tests. These results are consistent with schema theory, and it is recommended that physical education teachers should focus variable practice on task dimensions that are new to their classes.

Molecular cloning of resistance genes and architecture of a linked gene cluster involved in biosynthesis of oxytetracycline by Streptomyces rimosus.

The isolation of mutants of Streptomyces rimosus which were blocked in oxytetracycline (OTC) production was described previously. The genes for the early steps of antibiotic biosynthesis mapped together. Genomic DNA fragments of S. rimosus which conferred resistance to OTC and complemented all of these non-producing mutants have been cloned. The cloned DNA is physically linked within approximately 30 kb of the genome of S. rimosus. The gene cluster is flanked at each end by a resistance gene each of which, independently, can confer resistance to the antibiotic. In OTC-sensitive strains of S. rimosus, the entire gene cluster including both resistance genes has been deleted. Complementation of blocked mutants by cloned DNA fragments in multi-copy vectors was often masked by a secondary effect of switching off antibiotic production in strains otherwise competent to produce OTC. This adverse effect on OTC production was not observed with recombinants using low copy-number vectors.

Homology between Streptomyces genes coding for synthesis of different polyketides used to clone antibiotic biosynthetic genes.

Many important antibiotics such as tetracyclines, erythromycin, adriamycin, monensin, rifamycin and avermectins are polyketides. In their biosynthesis, multifunctional synthases catalyse iterated condensation of thio-esters derived from acetate, propionate or butyrate to yield aliphatic chains of varying length and carrying different alkyl substituents. Subsequent modifications, including aromatic or macrolide ring closure or specific methylations or glycosylations, generate further chemical diversity. It has been suggested that, if different polyketide synthases had a common evolutionary origin, cloned DNA coding for one synthase might be used as a hybridization probe for the isolation of others. We show here that this is indeed possible. Study of a range of such synthase genes and their products should help to elucidate what determines the choice and order of condensation of different residues in polyketide assembly, and might yield, by in vitro recombination or mutagenesis, synthase genes capable of producing novel antibiotics. Moreover, because genes for entire antibiotic pathways are usually clustered in Streptomyces, cloned polyketide synthase genes are valuable in giving access to groups of linked biosynthetic genes.

An E. coli-yeast shuttle cosmid with positive selection for inserted fragments.

We describe the construction of a cosmid cloning vector, pMT555, which allows positive selection for the presence of an inserted DNA fragment. The vector contains sequences which enable its replication and selection in either E. coli or Saccharomyces cerevisiae. We demonstrate that pMT555 may be used for the efficient construction of total genomic banks from small quantities of donor DNA. The positive selection permits the stable maintenance of the cosmid in E. coli and the faithful replication of inserted sequences.

Movement speed in children.

Two experiments were conducted to investigate movement speed in children of 6, 8, 10, and 12 yr of age. Different information loads were presented to the children on a serial task (Experiment 1), and on a discrete task (Experiment 2). On both tasks there was a linear relationship between movement time and information load. Reaction time was relatively unaffected by and increase in the difficulty of the required movement. By employing the formula, capacity = (Index of Difficulty) / (movement time), there was an increase in capacity by age with very little overlap between the ages. Strategies on the serial task were discussed and comparisons with adult subjects were made.