GRASPING COMPONENT ALTERATIONS AND LIMB TRANSPORT

The kinematic changes associated with the manipulation and transport c omponents during a prehensile movement were examined using an experime ntal paradigm that required alterations in only the manipulation compo nent. Instead of starting with the thumb and index finger naturally to gether (control condition), subjects began the reach-to-grasp movement with their thumb and fingers fully extended (experimental condition). In contrast to the control condition, in the experimental conditions the thumb and index finger started to close during wrist transport, th en opened again prior to object grasp. In addition, there was a brief inflection in the ascending portion of the velocity profile of the wri st in over half the trials. However, all the primary features of the t ransport component profile remained unaltered. The results suggest tha t there can be substantial reorganization of the grip aperture during the first part of the reach without altering the temporal and spatial relationships between grip aperture and transport as the object to be grasped is approached.