Body ownership towards the movement end-effector modulates motor performance under violation of motor intention

When we perform voluntary actions, our sense of body ownership and agency are dynamically shaped through an interaction between efferent and afferent signals under a consistent accordance between our intention-motor program and the perceived sensory reafferences. Previous studies examined the effects of spatiotemporal mismatches between the actual and intended consequences of the movement on motor performance and perception. We investigated the specific role of body ownership on motor performance when the seen and the intended movements do not match. Thirty healthy participants were asked to draw straight vertical lines while seeing a virtual body either from a first or a third person visual perspective. Initially, the virtual arm moved congruently with the participant’s arm, drawing straight lines synchronously. At a certain point, the movements of the virtual hand deviated spatially from the real hand movements, drawing clockwise ellipses instead of lines. We found that the ovalization index (i.e. the deviation of the real trajectory from an absolute vertical line) was significantly higher in 1PP (i.e., when the seen hand was attributed to the own body) as compared to 3PP (i.e., when the hand was attributed to another person). Additionally, this was positively correlated to the degree of body ownership and its pattern revealed an adaptation of the real drawings to the seen ellipses - as if copying them. We interpret the present findings in terms of a different weighting of prediction errors in updating one’s sensorimotor system depending on the experienced body ownership.