Touch inhibits subcortical and cortical nociceptive responses. Issue 10 (October 2015)

• Record Type: Journal Article
• Authors: Mancini, Flavia; Beaumont, Anne-Lise; Hu, Li; Haggard, Patrick; Iannetti, Gian Domenico D.
• Is Part Of: Pain. Volume 156:Issue 10(2015)
• Publication Date: 2015-10
• Subjects: Electrophysiology -- EEG -- Somatosensory-evoked potentials -- Laser-evoked potentials -- Nociceptive blink reflex -- Gate control theory -- Analgesia -- Pain modulation; Pain -- Periodicals; Douleur -- Périodiques; Anesthésie -- Périodiques; Pain; Electronic journals; Periodicals; Electronic journals; 616.0472
• DOI: 10.1097/j.pain.0000000000000253
• Languages: English
• ISSNs: 0304-3959

Abstract

Abstract : Abstract: The neural mechanisms of the powerful analgesia induced by touching a painful body part are controversial. A long tradition of neurophysiologic studies in anaesthetized spinal animals indicate that touch can gate nociceptive input at spinal level. In contrast, recent studies in awake humans have suggested that supraspinal mechanisms can be sufficient to drive touch-induced analgesia. To investigate this issue, we evaluated the modulation exerted by touch on established electrophysiologic markers of nociceptive function at both subcortical and cortical levels in humans. Aδ and C skin nociceptors were selectively activated by high-power laser pulses. As markers of subcortical and cortical function, we recorded the laser blink reflex, which is generated by brainstem circuits before the arrival of nociceptive signals at the cortex, and laser-evoked potentials, which reflect neural activity of a wide array of cortical areas. If subcortical nociceptive responses are inhibited by concomitant touch, supraspinal mechanisms alone are unlikely to be sufficient to drive touch-induced analgesia. Touch induced a clear analgesic effect, suppressed the laser blink reflex, and inhibited both Aδ-fibre and C-fibre laser-evoked potentials. Thus, we conclude that touch-induced analgesia is likely to be mediated by a subcortical gating of the ascending nociceptive input, which in turn results in a modulation of cortical responses. Hence, supraspinal mechanisms alone are not sufficient to mediate touch-induced analgesia. Abstract : Touch inhibits Aδ and C-fibre cortical potentials. Touch also suppresses the nociceptive blink reflex, a response generated before nociceptive input reaches the cortex.