Rubber Hand Illusion Increases Pain Caused by Electric Stimuli

Abstract

The rubber hand illusion (RHI) has been shown to alter the experience of pain, although studies have yielded inconsistent results. In this experiment we tested the influence of the RHI on the intensity of pain caused by electric stimuli. Electric stimuli were delivered to participants' experimental and control hands before RHI induction (control condition) and afterward (experimental condition), in a procedure that was double-blind with respect to location and strength of noxious stimulation. All hands were covered during the stimulation to avoid the analgesic effect of seeing one's own body part. The perceived location of the hand and of pain were measured after each trial in the experimental condition. The results showed that noxious stimuli were experienced as more painful on the hand under the illusion. In addition, in the experimental condition the perceived location of noxious stimulation applied to the experimental hand drifted toward the rubber hand. Our data suggest that the link between bodily illusions and pain could be modulated by uncertainty about location of pain and the affected body part. Future studies should aim to determine which aspects of altered body awareness lead to pain sensitization.

Perspective: We show that the RHI can change the perceived location of pain and increase pain ratings caused by electric stimuli. Our data suggest that the link between bodily illusions and pain could be modulated by uncertainty about location of pain and the affected body part.

Keywords: Rubber hand illusion; body awareness; electric stimuli; expectations; pain.