The effect of the direction of force-fields on transfer of learning between the arms during bimanual reaching

This study examined the effects of force-field direction (extrinsic vs. intrinsic) on transfer of learning during bimanual reaching. Subjects performed bimanual reaching tasks in two force-fields: (1) intrinsic and (2) extrinsic. Motor adaptation of each arm was determined by measuring the deviation of the hand trajectory from a straight line. It was found that rate of motor adaptation of the dominant arm was the same in the two tasks. For the nondominant arm, the rate of motor adaptation was greater during reaching in the intrinsic force-field than in the extrinsic force-field. It is concluded that the load-related sensory feedback from the dominant arm interfered with motor adaptation of the nondominant arm.