Human primary somatosensory cortex is differentially involved in vibrotaction and nociception

Abstract

The role of the primary somatosensory cortex (S1) in vibrotaction is well established. In contrast, its involvement in nociception is still debated. Here we test whether S1 is similarly involved in the processing of nonnociceptive and nociceptive somatosensory input in humans by comparing the aftereffects of high-definition transcranial direct current stimulation (HD-tDCS) of S1 on the event-related potentials (ERPs) elicited by nonnociceptive and nociceptive somatosensory stimuli delivered to the ipsilateral and contralateral hands. Cathodal HD-tDCS significantly affected the responses to nonnociceptive somatosensory stimuli delivered to the contralateral hand: both early-latency ERPs from within S1 (N20 wave elicited by transcutaneous electrical stimulation of median nerve) and late-latency ERPs elicited outside S1 (N120 wave elicited by short-lasting mechanical vibrations delivered to index fingertip, thought to originate from bilateral operculo-insular and cingulate cortices). These results support the notion that S1 constitutes an obligatory relay for the cortical processing of nonnociceptive tactile input originating from the contralateral hemibody. Contrasting with this asymmetric effect of HD-tDCS on the responses to nonnociceptive somatosensory input, HD-tDCS over the sensorimotor cortex led to a bilateral and symmetric reduction of the magnitude of the N240 wave of nociceptive laser-evoked potentials elicited by stimulation of the hand dorsum. Taken together, our results demonstrate in humans a differential involvement of S1 in vibrotaction and nociception. Whereas the role of the primary somatosensory cortex (S1) in vibrotaction is well established, its involvement in nociception remains strongly debated. By assessing, in healthy volunteers, the effect of high-definition transcranial direct current stimulation over S1, we demonstrate a differential involvement of S1 in vibrotaction and nociception.

Event-related brain potentials elicited by high-speed cooling of the skin: A robust and non-painful method to assess the spinothalamic system in humans

“…The fact that the N1 wave of CEPs exhibits a clear phase reversal over central areas suggests a strong contribution of a tangential source close to the central sulcus. In fact, this scalp topography closely resembles the scalp topography of the early-latency responses of somatosensory-evoked potentials, such as the N20 wave elicited by stimulation of the median nerve (Lenoir et al, 2017; Allison et al, 1991). These scalp topographies are compatible with activity originating from the posterior bank of the central sulcus, i.e.…”

The Effect of Dual-Hemisphere Transcranial Direct Current Stimulation Over the Parietal Operculum on Tactile Orientation Discrimination

“…Previous studies have shown that tDCS over the somatosensory cortices can affect SEPs (Matsunaga et al, 2004 ; Dieckhofer et al, 2006 ; Sugawara et al, 2015 ; Lenoir et al, 2017 ; Nakagawa et al, 2017 ), tactile discrimination of vibratory stimuli (Rogalewski et al, 2004 ) and spatial acuity (Ragert et al, 2008 ; Fujimoto et al, 2014 , 2016 ; Hilgenstock et al, 2016 ). Taken together with previous findings, the current results support the efficacy of tDCS for affecting somatosensory function.…”

The effect of experimental pain on the excitability of the corticospinal tract in humans: A systematic review and meta‐analysis

“…cortical) is to measure the latency to elicit a cortical evoked potential following noxious stimulus. For electrical stimulation, the latency of the somatosensory evoked potential following the stimulation of median nerve is ~20 ms for Caucasians and the onset is ~18 ms (Cruccu et al, 2008;Lenoir et al, 2017) and reduction in corticospinal excitability prior to this latency likely comes from the spinal level. This reduction in corticospinal excitability is possible because noxious electrical stimulus bypasses the cutaneous receptors and depolarizes not only Aδ and C nociceptive fibres with a slow conduction velocity, but also the non-nociceptive Aβ-fibres, which are larger and have a lower threshold and a faster velocity of conduction (Algoet et al, 2018;Beall et al, 1977;Mouraux et al, 2010).…”