The role of body ownership in postural control: A virtual full body illusion study

Body self-representation entails body ownership (the feeling of owning one's body) and sense of agency (the feeling of authoring one's actions), which typically co-occur. In embodiment illusions, body ownership can trigger the sense of agency in the absence of any real action execution, and such embodied movements are represented in the sensorimotor system similarly to one's own movements. However, previous studies have focused on the embodiment of specific voluntary movements, leaving unclear whether the automatic sensorimotor processes that support the body in active and static conditions are similarly affected by the embodiment of movements. The present study investigated changes in postural control (center of pressure, CoP) during and after embodiment (first-person perspective, 1PP), or observation (third-person perspective, 3PP), of a virtual avatar performing single-leg squats. The CoP displacement during participants' steady standing shifted coherently with the flexion and extension phases of the avatar's squats only in the 1PP but not in the 3PP condition (Experiments 1-2). However, there were no significant CoP shifts during participants' steady standing or two-legged squats after exposure to either condition (Experiment 2). Together, the results suggest that embodied movements are represented in the sensorimotor system similarly to the representation of one's own movements, even at the level of automatic full-body control. This effect might be supported by multisensory integration that subserves both embodiment and postural control. However, the embodiment of movements does not have prolonged effects on the sensorimotor system beyond the duration of the illusion.