Dominance of vision over proprioception on motor programming: evidence from ERP.

The brain determines positions and movements of body parts from inputs arising at least from vision and proprioception. Using the brain event-related potential called the lateralized readiness potential, which reflects motor cortical activity during motor programming, we showed in a motor task that viewing one hand in a sagittal mirror-giving the impression to see the opposite hand-generated activity in the motor cortex of the seen hand (i.e., of the nonmoving hand hidden behind the mirror). The visual influence on cortical motor region occurred even when the proprioceptive input related to the real opposite effector was not aligned on the visual feedback of the hand given by the mirror. This dominance vision over proprioception was greatly reduced when the task was executed in the dark with hand position represented by small lights fixed on the moving hand, with no motor activity being recorded in the cortical area of the inactive hand. These results give new insights into how the brain weights and integrates visual and proprioceptive information in motor control.