Modulation of Bodily Self-Consciousness by Self and External Touch.

Masayuki Hara,Olaf Blanke,Noriaki Kanayama,Roy Salomon

doi:10.1109/toh.2021.3067651

Abstract

The full body illusion (FBI) is a bodily illusion based on the application of multisensory conflicts that induce changes in bodily self-consciousness (BSC). This has been used to study cognitive brain mechanisms underlying body ownership and related aspects of self-consciousness. Typically, such paradigms employ external passive multisensory stimulation, thus neglecting the possible contributions of self-generated action and haptic cues to body ownership. In this article, the effects of both external and voluntary self-touch on BSC were examined with a robotics-based FBI paradigm. We compared the effects of classical passive visuotactile stimulation and active self-touch (in which experimental participants had a sense of agency over the tactile stimulation) on the FBI. We evaluated these effects using a questionnaire, crossmodal congruency task, and measurements of changes in self-location. The results indicated that both synchronous passive visuotactile stimulation and synchronous active self-touch induced illusory ownership over a virtual body, without significant differences in their magnitudes. However, the FBI induced by active self-touch was associated with a 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.

Highlights

IntroductionT WO central aspects of self-consciousness are the sense of body ownership (i.e., the feeling that one’s body or body parts belong to him/her) and the sense of agency (i.e., the feeling of control over the body’s actions) [1]–[4]
T WO central aspects of self-consciousness are the sense of body ownership and the sense of agency [1]–[4]
These results indicate that the participants experienced the full body illusion (FBI) in both the active self-touch-enabled FBI (a-FBI) and c-FBI conditions

Summary

Introduction

T WO central aspects of self-consciousness are the sense of body ownership (i.e., the feeling that one’s body or body parts belong to him/her) and the sense of agency (i.e., the feeling of control over the body’s actions) [1]–[4]. Recent experimental studies in healthy participants suggest that body ownership is grounded in the integration of multisensory signals [15]–[18] These studies typically employ bodily illusions in which a multisensory conflict (i.e., between a tactile and a visual cue) is created to induce modulations of body ownership [19]–[24]. When the seen and felt stroking are synchronous, a multisensory conflict arises as the visual information shows the stroking on the avatar’s body while the tactile information indicates the participants’ own bodies as the one being touched This multisensory conflict gives rise to changes in bodily self-consciousness (BSC) in which the participants experience illusory ownership over the avatar’s body as measured by subjective questionnaires, behavioral changes in perceived self-location, and alterations in physiological measures [17], [21], [25]–[27]. Modulations of body ownership can be achieved from passive multisensory stimulation in the absence of action cues, suggesting an independence of body ownership from agency-related motor mechanisms

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