On the role of tactile motion estimates and hand side in bimanual reaching tasks

Research on hand-reaching is of great interest due to the intricate integration of sensory inputs from the musculoskeletal system, skin, and motor command models. Recently, we developed an unimanual reaching task where participants were asked to slide their right index finger over a ridged plate. We observed an effect of the plate orientation on the motion angle that suggested a role of tactile motion estimates on the control of hand motion [1]. In this new study, we extend our previous findings to investigate the integration of tactile motion estimates from the two hands in a bimanual reaching task, during coordinated sliding actions over a plate with ridges. Consistently with our previous studies, we observed a linear relationship between motion angles and plate orientations in both, unimanual and bimanual conditions, suggesting that the two hands maintain an independent representation of tactile flow. Furthermore, our results reveal a systematic error in hand trajectory, with the right hand consistently exhibiting a bias compared to the left hand. Interestingly, this bias was reduced when the task was performed bimanually. These findings shed light on the complexities of bimanual motor control and the distinct roles played by tactile and musculoskeletal information.