In a paper in Journal of Neuroscience by Longo et al, from by Patrick Haggard’s group (in case you didn’t know, Haggard is a very big wig in the whole sensory processing/body image stuff), they describe an experiment that I reckon is cool: they used painful laser stimuli and compared pain evoked when supposedly normal healthy volunteers (see our post on “How normal are the people who participate in experiments?‘) looked at the arm that was stimulated, looked at the opposite arm in a mirror, looked at someone else’s arm, looked at the reflection of something else. They reported that pain is less when you can see your own arm, or the reflection of your opposite one, than if you can’t. They also reported reduction of the N2/P2 wave within the laser-evoked cortical potential. The N2/P2 reflects almost entirely supramodal processing rather than the somatosensory specific aspects. The very impressive Giandomenico Iannetti and Andre Mouraux have done some great experiments on the interpretation of the N2/P2 component of cortical evoked potentials, for example here: Iannetti GD, Hughes NP, Lee MC, Mouraux A. Determinants of laser-evoked EEG responses: Pain perception or stimulus saliency? Journal of Neurophysiology 2008;100(2):815-828.
1. Matthew R. Longo, Viviana Betti, Salvatore M. Aglioti, and Patrick Haggard (2009) Visually Induced Analgesia: Seeing the Body Reduces Pain, The Journal of Neuroscience, 29(39):12125-12130