title: Unmasking the obligatory components of nociceptive event-related brain potentials.
abstract: It has been hypothesized that the human cortical responses to nociceptive and nonnociceptive somatosensory inputs differ. Supporting this view, somatosensory-evoked potentials (SEPs) elicited by thermal nociceptive stimuli have been suggested to originate from areas 1 and 2 of the contralateral primary somatosensory (S1), operculo-insular, and cingulate cortices, whereas the early components of nonnociceptive SEPs mainly originate from area 3b of S1. However, to avoid producing a burn lesion, and sensitize or fatigue nociceptors, thermonociceptive SEPs are typically obtained by delivering a small number of stimuli with a large and variable interstimulus interval (ISI). In contrast, the early components of nonnociceptive SEPs are usually obtained by applying many stimuli at a rapid rate. Hence, previously reported differences between nociceptive and nonnociceptive SEPs could be due to differences in signal-to-noise ratio and/or differences in the contribution of cognitive processes related, for example, to arousal and attention. Here, using intraepidermal electrical stimulation to selectively activate Aδ-nociceptors at a fast and constant 1-s ISI, we found that the nociceptive SEPs obtained with a long ISI are no longer identified, indicating that these responses are not obligatory for nociception. Furthermore, using a blind source separation, we found that, unlike the obligatory components of nonnociceptive SEPs, the obligatory components of nociceptive SEPs do not receive a significant contribution from a contralateral source possibly originating from S1. Instead, they were best explained by sources compatible with bilateral operculo-insular and/or cingulate locations. Taken together, our results indicate that the obligatory components of nociceptive and nonnociceptive SEPs are fundamentally different.
authors: Institute of Neuroscience (IoNS), Université catholique de Louvain, Brussels, Belgium;
authors: A
authors: A
authors: Mouraux
authors: A L
authors: AL
authors: De Paepe
authors: E
authors: E
authors: Marot
authors: L
authors: L
authors: Plaghki
authors: G D
authors: GD
authors: Iannetti
authors: V
authors: V
authors: Legrain
mesh_terms: D000328:Adult; D000818:Animals; D001921:Brain / Q000502:physiology*; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008297:Male; D059225:Nociception / Q000502:physiology*; D009619:Nociceptors / Q000502:physiology; D055815:Young Adult
keywords: event-related potentials; intraepidermal stimulation; laser-evoked potentials; nociception; pain; primary somatosensory cortex