Prismatic lenses and pain

Torta, Diana [UCL]

Background: Prism adaptation (PA) is a non-invasive procedure which combines visual displacement with a visuo-motor pointing task to promote a reorganization of sensorimotor coordination that may expand to spatial cognition. Prismatic displacement (PD) of the visual field can be induced when prisms are worn but no sensorimotor task is required. PD induces cross-modal conflicts between proprioception and vision. Aims: Here we explored the effect of PA and PD on the perceived intensity of nociceptive and non-nociceptive somatosensory stimuli. In this way we were able test the effects of spatial remapping and cross-modal conflicts on somatosensory processing. Method: In three experiments in 41 healthy volunteers we induced PA (experiments 1 and 2) or PD (experiment 3) while participants had to rate the intensity of nociceptive and non-nociceptive somatosensory stimuli applied to the hands. Results: Our results indicate that: 1) PA leads to a detention of habituation for nociceptive and non-nociceptive somatosensory stimuli; 2) PA leads to a detention of habituation for nociceptive stimuli at both hands; 3) the visuo-proprioceptive conflict induced by PD does not reduce the perceived intensity of the stimuli. Conclusions: Taken together, these data indicate that a realignment of visual and motor coordinates can directly affect the perceived intensity of somatosensory stimuli, in contrast to cross-modal conflicts that have no effect on somatosensory processing.