Parallel processing of direction and extent in reaching movements

Summary form only given. Reaching movements, in which the hand is moved to a target location, require a sensorimotor transformation; the intended path, initially specified in extrinsic coordinates, must be transformed into a set of intrinsic coordinates that specify a pattern of muscle activation that will bring the hand to the target. A common framework for studying how the nervous system achieves this transformation is derived from robotics; it assumes a series of intermediate stages, including inverse kinematics and inverse dynamics computations. Experiments to characterize the coordinate systems in which reaching movements are planned and to determine whether serial computational strategies are used for planning hand trajectories are described.<>