Measuring the sensitivity of nociceptive temporal order judgment in sighted and early blind participants using the PSI method

In order to adapt behaviors to potential physical threats, it is crucial to coordinate the perception of the location of the threats in external space and that of the potential damage inflicted to the body. Therefore, the perception of somatosensory stimuli implies a remapping from a somatotopic frame of reference to a spatiotopic frame of reference, that is, a reference frame taking into account external space as coordinate, in order to integrate inputs from different sensory modalities into a multisensory representation of the body and the surrounding space. This remapping is thought to be mainly shaped by visual experience. Indeed, it has been demonstrated 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 investigate the role of vision in shaping the spatial perception of nociception by comparing the ability of visually deprived and sighted individuals to perceive and localize nociceptive stimuli. A temporal order judgment task was performed with pairs of CO2 laser heat stimulations applied on the hands either in an uncrossed or crossed posture, using an adaptive PSI method. Preliminary results show that sighted participants performed better with their hands uncrossed than crossed, suggesting that the perception of nociceptive stimuli also requires a spatial frame. Given the suggested role of vision in remapping tactile stimuli into external coordinates, we hypothesize that early blind should not display such a posture effect.