A Computational Mechanism to Account for Averaged Modified Hand Trajectories

Using the double-step target displacement paradigm the mechanisms underlying armtrajectory modification were investigated. Using short (10-110 msec) inter-stimulus intervals the resulting hand motions were initially directed in between the first and second target locations. The kinematic features of the modified motions were accounted for by the superposition scheme, which involves the vectorial addition of two independent point-topoint motionunits: one for moving the hand toward an internally specified location and a second one for moving between that location and the final target location. The similarity between the inferred internally specified locations andpreviously reported measured endpoints of the first saccades in double-step eye-movement studies may suggest similarities between perceived targetlocations in eye and hand motor control.