Abstract
Illusory body ownership to a virtual body is induced by synchronous movements of own body and the virtual body. This illusion can be induced by the synchronous movement of only the hands and feet (Kondo et al., 2018). Here, we examined whether the illusory ownership to the invisible body with the hands and feet was associated with changes in tactile spatial representations. Participants observed the virtual gloves and socks which moved synchronously or asynchronously with the participant’s movements in the first-person perspective through a virtual mirror in front of them. Then, participants made speeded elevation (upper vs. lower) discriminations of tactile targets presented to any of the four positions of the participant's abdomen (upper left, upper right, lower left, and lower right of the epigastrium), while trying to ignore the visual distractor presented at congruent or incongruent elevations in the empty space between the virtual hands and feet. Crossmodal congruency effect (CCE, difference between performance in incongruent and congruent conditions) becomes large when visual and tactile stimuli are perceived to be at the same spatial location. Therefore, we hypothesized that if the synchronized movements of virtual hands and feet induced the full body ownership to the invisible body, the CCE would be larger in the synchronous condition than the asynchronous condition. We found that, although the subjective illusory ownership to the invisible body was replicated, there was no difference in CCE between the synchronous and asynchronous conditions. These results suggest that the illusory ownership of the invisible body and CCE (spatial tactile representation) may be based on separate cognitive mechanisms. However, since the studies of rubber hand illusion and full body illusion indicate a link between bodily self-consciousness (ownership and self-location) and CCE, we need to investigate the difference between invisible and visible body ownerships in future study.