The effect of amplitude incongruence (small circles–large circles) and form incongruence (circles–lines) on the performance of the affected and non-affected arm was examined in 12 children with hemiplegic cerebral palsy in bimanual rhythmic drawing tasks. Amplitude and form incongruence are assumed to be associated with aspects of movement execution and movement planning, respectively. The following questions were addressed: Does amplitude or form incongruence in bimanual coordination result in: (a) accommodation of the affected or non-affected arm, or both, (b) an increase of temporal variability of drawing movements of the affected or non-affected arm, and (c) a decrease of bimanual coordination stability? Form incongruence resulted in accommodation of both affected and non-affected arm in a similar way found in non-disabled participants. Despite this accommodation, the temporal variability of both affected and non-affected arm was increased, and coordination stability decreased, because the spatial trajectories of affected and non-affected arm were still rather dissimilar. Amplitude incongruence resulted in accommodation of either the affected arm (large circles required) or non-affected arm (small circles required), and in an increase or decrease of temporal variability of the affected arm, depending on the degree of spatial similarity of the trajectories of affected and non-affected arm. These findings suggest that in children with hemiplegic cerebral palsy aspects of movement execution, but not aspects of movement planning are affected by the “hemiplegic” condition.
The author is with the Dept of Educational Sciences, Faculty of Social Sciences, Utrecht University, Heidelberglaan 1, 3584 CS, Utrecht, the Netherlands.