Size and Viewpoint of an Embodied Virtual Body Affect the Processing of Painful Stimuli

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.