The purpose of this study was to investigate the effects of different objects and target location of dominant hand on the non-dominant hand movement kinematics in a bimanual reaching task. Fifteen right-handed volunteers were asked to reach from same starting point to the different target point of right and left hand with grasping the objects of different size. Independent variables were 1) three different object types (small mug cup, name pen, and PET bottle), and 2) three different target locations (shorter distance, same distance, and longer distance than the non-dominant hand) of the dominant hand. Dependent variables were movement time (MT), movement distance (MD), movement mean velocity (MVmean), and movement peak velocity (MVmean) of the non-dominant hand. Repeated measures two-way analysis of variance (ANOVA) was used to test for differences in the non-dominant hand movement kinematics during bimanual reaching. The results of this study were as follows: 1) MT of the non-dominant hand was increased significantly when traveling with grasping the mug cup and reaching the far target location, and was decreased significantly when traveling with grasping the PET bottle and reaching the near target location of the dominant hand. 2) MD of the non-dominant hand was significantly increased during reaching the far target location, and significantly decreased during reaching the near target location with dominant hand. 3) MVmean of the non-dominant hand was increased significantly when traveling with grasping the PET bottle, and was decreased significantly when traveling with grasping the mug cup of the dominant hand. Therefore, it can be concluded that the changes of the ipsilateral hand movement have influence on coupling of the contralateral hand movement in bimanual reaching.

Purpose: The purpose of this study was to investigate the effective learning method of non-dominant hand for the sequential timing performance. Methods: Twenty right-handed undergraduate and graduate students were randomly assigned to the non-dominant hand practice group that practiced with only non-dominant hand or the bimanual practice group that practiced with both hands simultaneously. The participant was asked to alternatively press two buttons six times with the index finger of the non-dominant hand or both hands in order to reproduce accurately the goal rhythm pattern (3,600ms in total duration). The goal rhythm pattern had three rhythm types and two perceptual structures, which the (in)congruent structure was that the structure of auditory signal was (or not) in accordance with that of visual signal. Results: Bimanual practice group was more effective for absolute-timing learning than non-dominant hand practice group. Although absolute timing performance improved in congruent structure during acquisition phase, the learning effect on absolute timing was occurred in incongruent structure. Relative timing performance of two groups improved in congruent structure during acquisition phase, but the learning effect on relative timing was occurred in both perceptual structures. Conclusion: We suggest that practice methods should be applied differently for absolute timing or relative timing, and the possibility of improving the learning effect of a non-dominant hand by utilizing an incongruent structure of visual-auditory information.