Fingertip forces during object manipulation in children with hemiplegic cerebral palsy. I: anticipatory scaling.

Previous studies of grasping and object manipulation in children with cerebral palsy (CP) have suggested a dichotomy in the ability to use anticipatory control (planning) of the fingertip force output, depending on the type of sensory information (tactile or proprioceptive) on which it is based. The present study further explores this issue by testing the ability of 15 children with hemiplegic CP aged between 8 and 14 years to scale the fingertip force output in advance during the lifting of small objects whose weight and surface texture are varied. The results indicate that children with hemiplegia can use anticipatory control based on both the weight and texture of the object, but require a greater number of trials than age-matched children without CP (control children) before they can do so. We suggest that the initial lack of anticipatory control results from an indistinct internal representation of the object's physical properties due to disturbed sensory mechanisms, which may have direct implications for therapeutic intervention.