TY - JOUR T1 - Visual guidance of bimanual coordination relies on movement direction JF - bioRxiv DO - 10.1101/063404 SP - 063404 AU - Janina Brandes AU - Farhad Rezvani AU - Tobias Heed Y1 - 2016/01/01 UR - http://biorxiv.org/content/early/2016/07/12/063404.abstract N2 - Bimanual coordination is more precise for symmetrical than parallel finger movements. This symmetry advantage persists when the hands are oriented differently, despite then requiring the use of non-homologous muscles in the two hands. This finding suggests that coordination is partly guided by perceptual principles. It is unknown what kind of information induces this advantage for perceptual over anatomical movement coding. Here, we tested how different types of visual information affect the symmetry bias. Human participants made rhythmic, symmetrical and parallel, bimanual index finger movements with the hands held in the same or in different orientations. We manipulated visual feedback by placing a mirror between the hands so that participants saw the image of the left at the location of the right hand, creating the impression of bimanual symmetry independent of the right hand’s true movement. We replicated the symmetry bias, that is, symmetrical movements were generally performed more precisely than parallel movements, regardless of muscle homology. Furthermore, symmetrical mirror feedback impaired parallel movements, independent of hand posture and muscle homology. Conversely, mirror feedback improved symmetrical movements compared with regular hand view. These results suggest that immediate visual feedback about movement direction, but not about the configuration to achieve the movement, such as posture and muscle homology, determines the bimanual symmetry bias. ER -