Modulation of Bodily Self-Consciousness by Self and External Touch

The full body illusion (FBI) is a bodily illusion based on the application of multisensory conflicts inducing changes in bodily self-consciousness (BSC), which has been used to study cognitive brain mechanisms underlying body ownership and related aspects of self-consciousness. Typically, such paradigms have employed external passive multisensory stimulation, thus neglecting possible contributions of self-generated action and haptic cue to body ownership. The present paper examined the effects of both external and voluntary self-touch on the BSC with a robotics-based FBI paradigm. We compared the effects of classical passive visuo-tactile stimulation and active self-touch (in which experimental participants have the sense of agency over the tactile stimulation) on the FBI. We evaluated these effects by a questionnaire, a crossmodal congruency task, and measurements of changes in self-location. The results indicated that both the synchronous passive visuo-tactile stimulation and synchronous active self-touch induced illusory ownership over a virtual body, without significant differences in their magnitudes. However, the FBI induced by the active self-touch was associated with larger drift in self-location towards the virtual body. These results show that movement-related signals arising from self-touch impact the BSC not only for hand ownership, but also for torso-centered body ownership and related aspects of BSC.