title: Cortical inhibition of laser pain and laser-evoked potentials by non-nociceptive somatosensory input.
abstract: Although the inhibitory action that tactile stimuli can have on pain is well documented, the precise timing of the interaction between the painful and non-painful stimuli in the central nervous system is unclear. The aim of this study was to investigate this issue by measuring the timing of the amplitude modulation of laser evoked potentials (LEPs) due to conditioning non-painful stimuli. LEPs were recorded from 31 scalp electrodes in 10 healthy subjects after painful stimulation of the right arm (C6-C7 dermatomes). Non-painful electrical stimuli were applied by ring electrodes on the second and third finger of the right hand. Electrical stimuli were delivered at +50, +150, +200 and +250 ms interstimulus intervals (ISIs) after the laser pulses. LEPs obtained without any conditioning stimulation were used as a baseline. As compared to the baseline, non-painful electrical stimulation reduced the amplitude of the vertex N2/P2 LEP component and the laser pain rating when electrical stimuli followed the laser pulses only at +150 and +200 ms ISIs. As at these ISIs the collision between the non-painful and painful input is likely to take place at the cortical level, we can conclude that the late processing of painful (thermal) stimuli is partially inhibited by the processing of non-painful (cutaneous) stimuli within the cerebral cortex. Moreover, our results do not provide evidence that non-painful inputs can inhibit pain at a lower level, including the spinal cord.
authors.affiliation: Department of Neurosciences, Catholic University, Rome, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Testani
authors.affiliation: Department of Neurology, IRCSS S. Raffaele Pisana, Tosinvest-Sanità, Rome, Italy.
authors.forename: Domenica
authors.initials: D
authors.lastname: Le Pera
authors.affiliation: EEG Lab, IRCSS S. Raffaele Pisana, Tosinvest-Sanità, Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Del Percio
authors.affiliation: Neurology Unit, Ospedale Pediatrico Bambino Gesú, IRCCS, Piazza Sant'Onofrio 4, Rome, 00165, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Miliucci
authors.affiliation: Department of Psychological Sciences, Humanities and the Territory, 'G. d'Annunzio' University of Chieti and Pescara, Chieti, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Brancucci
authors.affiliation: Department of Neurology, Don Carlo Gnocchi Onlus Foundation, Milan, Italy.
authors.forename: Costanza
authors.initials: C
authors.lastname: Pazzaglia
authors.affiliation: Department of Neurology, IRCSS S. Raffaele Pisana, Tosinvest-Sanità, Rome, Italy.
authors.forename: Liala
authors.initials: L
authors.lastname: De Armas
authors.affiliation: EEG Lab, IRCSS S. Raffaele Pisana, Tosinvest-Sanità, Rome, Italy.|Department of Physiology and Pharmacology, University of Rome 'La Sapienza', Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Babiloni
authors.affiliation: Department of Neurosciences, Catholic University, Rome, Italy.
authors.forename: Paolo Maria
authors.initials: PM
authors.lastname: Rossini
authors.affiliation: Neurology Unit, Ospedale Pediatrico Bambino Gesú, IRCCS, Piazza Sant'Onofrio 4, Rome, 00165, Italy.|Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Valeriani
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D066331:Laser-Evoked Potentials / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D058748:Pain Perception / Q000502:physiology*; D055139:Sensory Gating / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*
keywords: cerebral cortex; gating; inhibition; pain; touch