We tested whether, how, and where intrasegmental touch modulates the perception of laser-evoked, acute pain. We provide evidence for a spatial organisation of touch–pain interactions within a single dermatome.
Pain relief by touch has been studied for decades in pain neuroscience. Human perceptual studies revealed analgesic effects of segmental tactile stimulation, as compared to extrasegmental touch. However, the spatial organisation of touch–pain interactions within a single human dermatome has not been investigated yet. In 2 experiments we tested whether, how, and where within a dermatome touch modulates the perception of laser-evoked pain. We measured pain perception using intensity ratings, qualitative descriptors, and signal detection measures of sensitivity and response bias. Touch concurrent with laser pulses produced a significant analgesia, and reduced the sensitivity in detecting the energy of laser stimulation, implying a functional loss of information within the ascending Aδ pathway. Touch also produced a bias to judge laser stimuli as less painful. This bias decreased linearly when the distance between the laser and tactile stimuli increased. Thus, our study provides evidence for a spatial organisation of intrasegmental touch–pain interactions.
a Institute of Cognitive Neuroscience, University College London, London, UK
b Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
c Division of Medicine, University College London, London, UK
* Corresponding author at: Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK. Tel.: +44 0 2076791151.
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Received 24 June 2013
Received in revised form 10 December 2013
Accepted 13 December 2013
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