Abstract
Precision of goal-directed aiming movements toward visuo-haptic targets is generally higher than toward visual or haptic only targets. However, the role of each modality in visuo-haptic reaching is still unknown. In the present study, we investigated how removing or providing visual information during a reaching movement toward a haptically perceived target modulates precision (end point variability). Participants were asked to perform rapid and accurate reaches to the top of three cylinders (diameter: 10, 25 and 35 mm, height: 50 mm) located 200 mm from the starting position. In one block, vision and haptics were always available before reach initiation and during the whole movement (HV), whereas in the other block, only haptics was available (H). However, in both blocks, on half of the trials, vision was suddenly removed (HV-) or added (HV+) during the reaching movement. These perturbations occurred at the 25% or 50% of the movement. Precision was highest in HV and worst in H. However, while removing vision at different points of the hand path (HV-) had a slight worsening effect on precision, adding it (HV+) strongly improved precision, without, however, ever reaching the HV or HV- level. Interestingly, while movement time did not depend on the initial sensory conditions, time to movement onset was longer in H and HV+ than in HV and HV-, indicating a longer movement planning phase when only haptics was available during movement preparation. Our findings show that integrating visual and haptic sensory information during the planning phase leads to much better action performance compared to when the senses are integrated on-line, even when vision is provided in the very early stages of the movement. Thus, when haptic information is strengthened by an early visuo-haptic sensory integration, preventing on-line visual feedback has only minor repercussions on movement performance.
Meeting abstract presented at VSS 2018