KINEMATIC CHARACTERISTICS OF REACHING IN CHILDREN WITH DOWN-SYNDROME

Movement abnormalities observed in children with Down Syndrome (DS) ma y arise from difficulties in perceiving or using relevant task cues fo r planning actions. Kinematic characteristics of reaching in 8-10-year -old DS children were investigated and compared with normally developi ng children, matched in chronological (CA-C) and in developmental (DA- C) age. Task cues were varied by manipulating size (little, big) and f unction of objects (hold, place, throw). Reaching actions were recorde d using OPTOTRAK. Compared to control children, particularly CA-C, DS subjects moved more slowly and their wrist trajectories varied conside rably over trials. The proportion of total movement time in decelerati on was greater and less smooth (more movement units) for DS children. This may reflect feedback guidance to correct spatial inaccuracy of th e reach or difficulties in grasping. While there were no systematic gr oup differences in kinematic features as a function of task cues, traj ectory shapes of DS children were least variable when reaching was fol lowed by a low-precision task when context was available (throw). Poss ible explanations of these findings are considered.