Children with Developmental Coordination Disorder (DCD) are reported to have high temporal variability in tasks requiring precise timing. The current study examined whether this timing deficit was due to the cerebellar 'explicit timing' process in the discontinuous, but not the continuous movement. Ten children with DCD and thirty-one typically developing children performed continuous, discontinuous circle-and line-drawing tasks. Results showed that both children with DCD and their age-matched controls had higher temporal variability in the discontinuous than that in the continuous movements. Individual comparisons between each child with DCD and the performance of typically developing children revealed that two out of ten children with DCD showed limited timing deficit in both types of discontinuous drawing (lines and circles). Additionally, three different children with DCD had timing problems with only discontinuous line drawing. Thus, the possibility of a compromised cerebellar function may exist in a subgroup of children with DCD. This work raises a critical issue with respect to the functional heterogeneity of this population and emphasizes the importance of an individualized analysis in this movement disorder.
KeywordsDevelopmental Coordination Disorder (DCD); timing; circle drawing; cerebellum One of the most salient features of coordinated movements is the temporal consistency across repetitions. Children with Developmental Coordination Disorder (DCD) [1] have demonstrated much higher temporal variability than age-matched typically developing children in tasks that require precise timing [6;13;22]. While up to 6% of American school children are thought to be affected by DCD[1], the underlying mechanism and its etiology are still not well understood.Send correspondence to: Jin Bo, Department of Kinesiology, University of Michigan, Ann Arbor, MI 48109, Fax: (734) 936-1925 Email: jinbo@umich.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. One hypothesis that has recently emerged is that the poor timing in children with developmental disorders may be attributed to impaired cerebellar function [10;15]. A few studies indicate that children who were classified as 'clumsy' had difficulties in fine motor tasks requiring precise timing, similar to that observed in adult patients with cerebellar lesions [6;13;22]. Recently, it was reported that patients with cerebellar lesions have restricted timing deficits in discontinuous but not in continuous circle drawing tasks [11;18;24]. This is thought to reflect the 'explicit timing' processes, in the sense that a...