Planning reaching and grasping movements: theoretical premises and practical implications.

This paper presents the background, premises, and results of a model of movement planning. The model's central claims are fourfold: (a) A task is defined by a set of prioritized requirements, or what we call a constraint hierarchy; (b) movement planning works first by specifying a goal posture and then by specifying a movement to that goal posture; (c) movements have characteristic forms; and (d) movements can be shaped through simultaneous performance of different movements, even by the same effector. We review the model and then speculate on its implications for clinical concerns, especially spasticity