In order to adapt behavior to a potentially body damaging threat, it is crucial to coordinate the perception of the location of the threat in external space and that of the location of the potential damage on the body surface. Such ability presupposes interactions between nociceptive stimuli and visual stimuli occurring close to the body. We hypothesized that these interactions would rely on multisensory representations of each limb itself, extending its boundaries slightly into external space, with less influence of the global representation of the body as a whole. In most studies investigating such representations, spatial organization of the somatic and extra-somatic stimuli is made according to an egocentric frame of reference centered on the main axes of the participant's whole body (e.g. the trunk), dissociating the left vs. the right side of space. Here, the contribution of such a body-centered frame was minimized, by placing participants' hands in front of them along their anteroposterior body axis, one at a proximal, the other at a distal location. They performed a temporal order judgment task on pairs of visual stimuli, one delivered close to each hand. Visual stimuli were preceded by nociceptive stimuli applied either on one hand, or on both hands simultaneously (control condition). Results showed that, as compared to the control condition, participants' judgements were biased in favor of the visual stimuli the closest to the stimulated hand, irrespective of their distance from the trunk. This finding supports the idea that the mechanisms underlying nociceptive-visual interactions are based on spatial representations that primarily use the stimulated limb rather than the whole body as a coordinate system.
Keywords: Multisensory interactions; Nociception; Peri-limb representations; Peripersonal space; Temporal order judgments; Vision.
Copyright © 2017 Elsevier B.V. All rights reserved.