Coordination and concurrency in bimanual rotation tasks when moving away from and toward the body.

In the present series of experiments we investigated how object transport and rotate movements are performed when they are directed away from (Experiment 1) and toward (Experiment 2) the body under both unimanual and bimanual conditions. Our results indicated that unimanual conditions are faster and more efficiently produced than bimanual movements in far peripersonal space, suggesting that there is a cost to performing bimanual movements. However, in near peripersonal space, bimanual same movements were performed in a manner similar to unimanual movements, indicating that there is no significant cost associated with similar bimanual movements that are performed using the lower visual field and in near peripersonal space. Both experiments also indicate that the two hands are tightly synchronized when the two movements being performed require the same rotation. However, when performing bimanual movements where the rotation being performed by the two hands is different, this synchronization is weaker. Finally, the combined results from the two experiments indicated that movements made toward the body are not performed in a similar manner to movements that are made away from the body. Specifically, it is clear from the current studies that movements toward the body are performed faster and possibly that the hands are less synchronized for bimanual movements requiring different rotations by the two hands.