Planning and execution of multijoint movements.

This paper reviews some recent studies related to the generation of simple multijoint arm movements. Two principal issues are considered. The first concern is how movements are represented internally by the central nervous system. There are many possible sets of coordinates that could be used to represent arm movements. Two of the possibilities are reviewed: representation in terms of joint angular motions versus representation in terms of motions of the hand in external space coordinates. A second concern is the transformation from intention to action: how is an internal representation of motion expressed by the neuromuscular system? The computational complexity of this problem is reviewed. A way in which the mechanics of the neuromuscular system could be exploited to simplify this problem is discussed.