Laser evoked potential amplitude and laser-pain rating reduction during high-frequency non-noxious somatosensory stimulation

Publication date: Available online 24 February 2018
Source:Clinical Neurophysiology
Author(s): Massimiliano Valeriani, Costanza Pazzaglia, Vincenzo Rizzo, Angelo Quartarone, Catello Vollono
ObjectiveTo investigate the mechanism subtending the analgesic effect of high frequency non-painful somatosensory stimulation.MethodsLaser evoked potentials (LEPs) and laser-pain rating were obtained from healthy subjects to stimulation of different parts of the body. LEPs were recorded at baseline and during non-painful electrical stimulation of the superficial branch of the right radial nerve (RRES).ResultsRRES reduced N2/P2 LEP amplitude to right radial (F(8,10)=82.4, p<0.001), left radial (F(8,10)=22.2, p<0.001), and right ulnar (F(8,10)=7.2, p=0.008) stimulation, while the N2/P2 amplitude to left ulnar territory stimulation remained unchanged (F(8,10)=3.6, p=0.07). The laser-pain rating was reduced by RRES to bilateral radial territory stimulation (p<0.05). In a control experiment, laser-pain rating and LEPs to left foot stimulation were not modified by RRES (p>0.05).ConclusionsOur study confirms that the non-nociceptive afferents dampen the nociceptive input. The spatial pattern of this interaction suggests that, when conditioning higher frequency non-painful stimulation is used, the inhibition takes place at the spinal cord.SignificanceOur experimental design reproduces what happens when non-painful somatosensory stimuli are used to reduce pain, such as rubbing a wound or during transcutaneous electrical nerve stimulation. Therefore, in these situations the analgesia is likely to occur at the spinal cord level.



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