Contribution of visual and proprioceptive feedback to the control of arm movements : influence of the instruction on the integration of sensitive information

Multisensory integration in motor control has been widely studied for decades. Visual and proprioceptive feedback principally contribute to the estimation of the position of the arm and the dynamics of the environment. However, it remains unknown how vision and proprioception are integrated during online control when they convey incongruent information. Here, we analyzed the way that feedback from these modalities is integrated when participants were aware of the deviation between visual feedback and their true hand location during reaching movements under mechanical perturbations. To do this, participants realized two experiments with a similar protocol but different instructions. In one experiment, they were asked to control the hand-aligned cursor without knowing that it could be deviated from the actual position of their hidden hand. The second experiment consisted in asking them to control their hand, they were aware of the possibility of a deviation of the visual cursor. We observed that participants were not able to ignore the visual feedback even if they were aware of its incongruency and that they tended to have greater corrective responses when they had to control their hand rather than the visual cursor. We hypothesized that this increase in corrective response while controlling their hand is due to the inability of the participants to model the environment they were in, leading them to adopt a robust control strategy.