The body fades away: investigating the effects of transparency of an embodied virtual body on pain threshold and body ownership.

Matteo Martini,Antonella Maselli,Maria V Sanchez-Vives,Konstantina Kilteni

doi:10.1038/srep13948

Abstract

The feeling of “ownership” over an external dummy/virtual body (or body part) has been proven to have both physiological and behavioural consequences. For instance, the vision of an “embodied” dummy or virtual body can modulate pain perception. However, the impact of partial or total invisibility of the body on physiology and behaviour has been hardly explored since it presents obvious difficulties in the real world. In this study we explored how body transparency affects both body ownership and pain threshold. By means of virtual reality, we presented healthy participants with a virtual co-located body with four different levels of transparency, while participants were tested for pain threshold by increasing ramps of heat stimulation. We found that the strength of the body ownership illusion decreases when the body gets more transparent. Nevertheless, in the conditions where the body was semi-transparent, higher levels of ownership over a see-through body resulted in an increased pain sensitivity. Virtual body ownership can be used for the development of pain management interventions. However, we demonstrate that providing invisibility of the body does not increase pain threshold. Therefore, body transparency is not a good strategy to decrease pain in clinical contexts, yet this remains to be tested.

Highlights

The feeling of “ownership” over an external dummy/virtual body has been proven to have both physiological and behavioural consequences
Immersive Virtual Reality (IVR) technology represents an effective tool as it allows the creation of sensory environments that can be replicated almost identically and that are under the full control of the experimenter[20]
We presented healthy participants with a co-located virtual body with four different levels of transparency, while participants were tested for pain threshold by increasing ramps of heat stimulation

Summary

Introduction

The feeling of “ownership” over an external dummy/virtual body (or body part) has been proven to have both physiological and behavioural consequences. Following a similar paradigm, Romano and colleagues reported a reduced skin conductance response to painful stimuli when participants saw and identified themselves with the avatar body displayed in front of them[15] All of these studies provide interesting insights on how the vision of the body can play a major role in the modulation of pain perception. Does IVR allows one to feel immersed and present in a computer-generated environment, but it makes possible the induction of the illusion of owning a virtual body[20,21], a body that can be rendered with the morphological characteristics that the experimenter determines[22] This illusion has been shown to affect the perceptual responses of participants[23]. Thanks to its unique advantage to manipulate visual information in a controlled and systematic manner, IVR represents an excellent tool for investigating body-related human perception, including pain perception, under both healthy and clinical conditions

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Discussion

Conclusion