Influence of the visual feedback of body orientation on motor coordination during object manipulation : a virtual-reality study

Details

Supervisors

Lefèvre, Philippe ; Opsomer, Laurent

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil mécanicien, à finalité spécialisée

Abstract

The Central Nervous System is known to orchestrate the planning and execution of movements based on somatosensory, vestibular and visual inputs. These feedbacks enable us to correctly estimate our orientation in space. However, the specific contribution of each system in the realization of movements is not perfectly mastered yet. The goal of this study was to assess in which extend the visual feedback is taken into account in the realization of movements. To do so, a virtual reality headset was used to display visual inconsistencies between what is seen and reality. Subjects performed oscillatory arm movements on different contexts while holding an object in hand. Specifically, the effect of displaying an inconsistency about the movement’s direction or about the body orientation were evaluated on different body positions: right-side-up, supine and upside down. The impact of vision on the grip dynamics and the kinematics of arm movements while holding an object was determined. It was found that the correlation between grip and load forces was accurate no matter the visual input. It seems that the CNS uses an internal model based on the perception of gravity to modulate the coupling between grip and load forces that is not easily disruptible by inconsistencies on the visual feedback. However, the combination of a visual inconsistency about the movement’s direction and an unusual body orientation induces an effect on the time modulation between grip and load forces. This can indicate that visual feedback of motion direction has an impact on the anticipation of load force changes during object manipulation and thus helps to adapt the grip force accordingly. On the other hand, body axis seems to have an impact on the kinematics of arm movement.