title: Size and Viewpoint of an Embodied Virtual Body Affect the Processing of Painful Stimuli.
abstract: Looking at one's own body might induce visual analgesia. However, the cognitive and physiological mechanisms underlying such visual analgesia are unknown. Because body and pain representations in the brain are multisensory, and have been reported to partially overlap, we herein investigated whether experimentally-induced changes in bodily self-consciousness (BSC) modulate pain. We measured physiological responses to pain (skin conductance response [SCR]) and the subjective experience of pain, under conditions of manipulated BSC. First we investigated whether looking at a virtual body that was associated with BSC (embodiment) reduced responses to pain, which revealed the effect of BSC on pain processing. Second, we manipulated the visual size of the virtual body during painful stimulation, a procedure known to modulate pain processing when used with biological bodies, but never studied with embodied avatars. We found reduced SCR in conditions of illusory embodiment, and a negative correlation between virtual body size and SCR, whereas subjective pain ratings were not affected by these manipulations. These results suggest that pain processing is modulated during illusory states of BSC and that these changes are greater for larger virtual bodies, which sustains that pain and its physiological mechanisms are associated with the bodily self, opening promising avenues for future pain treatments.
  
  
  CONCLUSIONS
  We show that BSC affects the processing of painful stimuli with induction of different levels of pain responses for embodied virtual bodies of different sizes. Our data reveal novel links between pain and self and suggest that embodied virtual bodies are a promising technique for future pain treatments.
authors.affiliation: University of Milan-Bicocca, Department of Psychology, Milan, Italy; NeuroMi, Milan Center for Neuroscience, Milan, Italy; Laboratory of Cognitive Neuroscience, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland; Center for Neuroprosthetics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland. Electronic address: daniele.romano@unimib.it.
authors.forename: Daniele
authors.initials: D
authors.lastname: Romano
authors.affiliation: Laboratory of Cognitive Neuroscience, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland; Center for Neuroprosthetics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland; Immersive Interaction Group, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Joan
authors.initials: J
authors.lastname: Llobera
authors.affiliation: Laboratory of Cognitive Neuroscience, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland; Center for Neuroprosthetics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Olaf
authors.initials: O
authors.lastname: Blanke
mesh_terms: D005260:Female; D005712:Galvanic Skin Response; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D010146:Pain / Q000503:physiopathology / Q000523:psychology*; D058748:Pain Perception / Q000502:physiology; D010775:Photic Stimulation; D012649:Self Concept; D014796:Visual Perception; D055815:Young Adult
keywords: Full body illusion; analgesia; body representation; pain; skin conductance response