Control of discrete bimanual movements: How each hand benefits from the other

Lateralized sensorimotor hand functions are often investigated separately or sequentially for each hand, e.g., in matching tasks, but rarely under more ecological circumstances where both hands move simultaneously. Using a novel bimanual paradigm in 21 young, healthy participants, this study addresses how postulated lateralized control processes of one hand influence control of the other hand across modalities. More specifically, in this paradigm one hand operates under visuomotor conditions, while the other hand receives no visual feedback and operates predominantly under kinesthetic control. Performance of the hand that does not receive visual feedback is compared between when moving alone (unimanual condition) and when moving together with the contralateral visually controlled hand (bimanual condition). Results suggest that during concurrent bimanual movements the 'invisible' hand benefits from specific control proficiencies of the 'visible' hand, indicating crossmodal and interhemispheric sharing of information that complements each hand's own strengths. These findings lend further support to a more differentiated view of functional lateralization of handedness.