Bimanual coordination affects motor task switching.

Task-switching paradigms have generally been used to investigate cognitive processes involved in decision making or allocating attention. This work extended the task-switching paradigm into the motor domain in order to investigate the consequences of an unexpected environmental perturbation on reaction time and movement time. Typically, task-switching paradigms have investigated consequences of rearranging task sets from one trial to the next; this work explored rearranging planned movements within the context of a single trial. Of particular interest was how the motor system reorganizes coordination patterns when reaching amplitude congruency is manipulated between the two hands. Results for Experiment 1 and the far distance in Experiment 2 indicated that reaction time switch costs were the smallest during congruent task-switch trials, where reaching amplitudes between the two hands were the same. This implies that a planned movement parameter for one hand is accessible for the other hand in the circumstance of an unexpected task switch. However, the reversed congruency effects found for the near distance in Experiment 2 suggest that the ability to capitalize on stored parameter information to decrease reaction time is dependent on environmental factors and task instructions. Movement time results showed that even if a movement with one hand is aborted in mid-execution, it can still influence the performance of the other hand during a task switch. This suggests that bimanual coordination can affect prehensile performance even though only one hand has a goal to achieve.