The neural dynamics of goal-directed arm movements: a developmental perspective

We present a neuro-dynamic architecture for the generation of movement of the hand toward a visual target that integrates movement planning based on visual input, movement initiation and termination, the generation of the time courses of virtual trajectories of the hand in Cartesian space, and their transformation into virtual joint trajectories and muscle forces. The architecture captures properties of adult goal-directed arm movements such as bell-shaped velocity profiles and on-line updating of a movement when the target is shifted. The integrated and autonomous nature of the architecture makes it possible to study how motor performance is affected when one of the three core processes, planning, timing, and transformation from end-effector to joint space, are decalibrated to reflect earlier stages of development. We find signatures of the development of reaching such as multiple movement units and curved movement paths in the "young" model.