Vision and spatial perception of pain : measuring the sensitivity of nociceptive temporal order judgments in sighted and blind participants using the PSI method
Camille Vanderclausen · Digital Access to Libraries (Université catholique de Louvain (UCL), l'Université de Namur (UNamur) and the Université Saint-Louis (USL-B)) · 2017
In order to adapt our behavior to potential physical threats, it is crucial to coordinate the perception of the location of the threats in external space and the position of the damage inflicted to the body. Therefore, the perception of somatosensory stimuli involves different coordinate systems, conceptualized as a remapping from a somatotopic frame of reference, coding the body space, toward a spatiotopic frame of reference, taking external space into account. Previous studies have pointed out the role of visual experience in the development of such a spatial remapping for the perception and localization of touch. Indeed, it has been shown that crossing the hands over the body midline affects the ability to perceive the temporal order of two tactile stimuli in sighted but not in early blind individuals. Here, we investigated the role of vision in shaping the spatial perception of nociceptive inputs by comparing the ability of visually deprived and normally sighted participants to localize nociceptive stimuli. A temporal order judgment task was performed by all the participants with pairs of CO₂ laser heat stimulations applied on the hands either in an uncrossed or crossed posture, using an adaptive PSI method. Results show that sighted participants performed better with their hands uncrossed than crossed, suggesting that the perception of nociceptive stimuli requires a spatial frame in order to integrate inputs from different sensory modalities. The perception of tactile and nociceptive stimuli thus seem to share the same spatial organization in normally sighted participants, although the finality of the multisensory integration would be of even greater relevance for nociceptive inputs because it would allow defensive behaviors to take place. On the contrary, early blinds were not affected by the posture. Together, these results suggest an important role of visual experience in shaping the perception of nociceptive stimuli in external space. However, the use of a spatial frame of reference to process nociception would not strictly depend on vision given the fact that early blind individuals can navigate in space and develop efficient abilities to adapt their behavior according to the environment.