RAPID AIMED LIMB MOVEMENTS - DIFFERENTIAL-EFFECTS OF PRACTICE ON COMPONENT SUBMOVEMENTS

Three experiments are reported in which subjects practiced rapid aimed limb movements (arm pointing and wrist rotation) toward a visible tar get region. Subjects were required to minimize their movement duration s while still landing in the target. The movement trajectories were ex amined to assess the effects of practice on separate component submove ments of the limb movements. The results revealed that practice improv ed primarily temporal, not spatial, aspects of performance. Practice r educed the overall movement durations, but had different effects on th e individual submovements: Practice allowed subjects to reduce the amo unt of time spent performing final corrective submovements, but actual ly increased slightly the time needed to produce the initial ballistic submovement. The results suggest that practice in the present task pr imarily enhanced the ability to use feedback information, but there wa s also some evidence of changes in the ballistic, preprogrammed portio n of the movements. The results demonstrate that analysis of submoveme nts can reveal important details of the underlying motor control proce sses.