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Cited by 541Pain Mechanisms and TreatmentsPain Management and TreatmentTactile and Sensory Interactions

Brain generators of laser-evoked potentials: from dipoles to functional significance

Garcia-Larrea, L, Frot, M, Valeriani, M·2003·Neurophysiologie Clinique/Clinical Neurophysiology
DOI 10.1016/j.neucli.2003.10.008
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Abstract

In this work we review data on cortical generators of laser-evoked potentials (LEPs) in humans, as inferred from dipolar modelling of scalp EEG/MEG results, as well as from intracranial data recorded with subdural grids or intracortical electrodes. The cortical regions most consistently tagged as sources of scalp LERs are the suprasylvian region (parietal operculum, SII) and the anterior cingulate cortex (ACC). Variability in opercular sources across studies appear mainly in the anterior-posterior direction, where sources tend to follow the axis of the Sylvian fissure. As compared with parasylvian activation described in functional pain imaging studies, LEP opercular sources tended to cluster at more superior sites and not to involve the insula. The existence of suprasylvian opercular LEPs has been confirmed by both epicortical (subdural) and intracortical recordings. In dipole-modelling studies, these sources appear to become active less than 150 ms post-stimulus, and remain in action for longer than opercular responses recorded intracortically, thus suggesting that modelled opercular dipoles reflect a "lumped" activation of several sources in the suprasylvian region, including both the operculum and the insula. Participation of SI sources to explain LEP scalp distribution remains controversial, but evidence is emerging that both SI and opercular sources may be concomitantly activated by laser pulses, with very similar time courses. Should these data be confirmed, it would suggest that a parallel processing in SI and SII has remained functional in humans for noxious inputs, whereas hierarchical processing from SI toward SII has emerged for other somatosensory sub-modalities. The ACC has been described as a source of LEPs by virtually all EEG studies so far, with activation times roughly corresponding to scalp P2. Activation is generally confined to area 24 in the caudal ACC, and has been confirmed by subdural and intracortical recordings. The inability of most MEG studies to disclose such ACC activity may be due to the radial orientation of ACC currents relative to scalp. ACC dipole sources have been consistently located between the VAC and VPC lines of Talairach's space, near to the cingulate subsections activated by motor tasks involving control of the hand. Together with the fact that scalp activities at this latency are very sensitive to arousal and attention, this supports the hypothesis that laser-evoked ACC activity may underlie orienting reactions tightly coupled with limb withdrawal (or control of withdrawal). With much less consistency than the above-mentioned areas, posterior parietal, medial temporal and anterior insular regions have been occasionally tagged as possible contributors to LEPs. Dipoles ascribed to medial temporal lobe may be in some cases re-interpreted as being located at or near the insular cortex. This would make sense as the insular region has been shown to respond to thermal pain stimuli in both functional imaging and intracranial EEG studies.

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  • The later N2 and P2 components reflect cortical generators in the insular and anterior cingulate cortices and largely represent cortical mechanisms that determine the subjective experience of pain.

    “The later N2 and P2 components reflect cortical generators in the insular and anterior cingulate cortices 30, 63, and also relate to the intensity of noxious stimuli, although they largely represent cortical mechanisms that determine the subjective experience of pain 48.”

    From The Analgesic Effect of Oxytocin in Humans: A Double‐Blind, Placebo‐Controlled Cross‐Over Study Using Laser‐Evoked Potentials (2016) · cites this paper as [30]

  • The early N1 component reflects activity of cortical generators in the contralateral operculoinsular and primary somatosensory cortices and is largely driven by the magnitude of ascending nociceptive input, representing an early stage of sensory processing before the perceptual outcome is determined.

    “The early N1 component, reflecting the activity of cortical generators in the contralateral operculoinsular and primary somatosensory cortices 30, 63, is largely driven by the magnitude of the ascending nociceptive input, representing an early stage of sensory processing before the perceptual outcome of the nociceptive input is determined 48, 64, 65.”

    From The Analgesic Effect of Oxytocin in Humans: A Double‐Blind, Placebo‐Controlled Cross‐Over Study Using Laser‐Evoked Potentials (2016) · cites this paper as [30]

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Authors
Garcia-Larrea, L., Frot, M., & Valeriani, M.
Affiliations
  • Lyon 1 Université (FR)
  • Università Cattolica del Sacro Cuore (IT)
ORCID
Venue
Neurophysiologie Clinique/Clinical Neurophysiology
Publisher
Elsevier BV
Published
2003-12
Volume
33
Issue
6
Pages
279-292
ISSN
0987-7053 (ISSN-L)
DOI
10.1016/j.neucli.2003.10.008
OpenAlex
W2045152969
Cited by
541
References
116
Citations by year
2026: 16 · 2025: 17 · 2024: 15 · 2023: 13 · 2022: 21 · 2021: 27 · 2020: 22 · 2019: 12 · 2018: 25 · 2017: 30 · 2016: 26 · 2015: 43 · 2014: 19 · 2013: 31 · 2012: 28
FWCI
2.27
Type
journal article
Language
en
Open access
closed
Licence
www.elsevier.com/tdm/userlicense/1.0/ (tdm)
Locations
  • Neurophysiologie Clinique (publishedVersion)
  • PubMed (publishedVersion)
  • HAL (submittedVersion)
  • Cineca Institutional Research Information System (Tor Vergata University) (submittedVersion)
Topics
  • Health Sciences › Medicine › Physiology › Pain Mechanisms and Treatments
  • Health Sciences › Medicine › Anesthesiology and Pain Medicine › Pain Management and Treatment
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Tactile and Sensory Interactions
Keywords
laser-evoked potentials, cortical generators, anterior cingulate cortex, somatosensory cortex, insula, pain processing, orienting response, intracranial recordings, subdural grids, intracortical electrodes, scalp distribution, MEG source localization, EEG
MeSH terms
Animals, Cerebral Cortex, Electroencephalography, Evoked Potentials, Humans, Lasers, Somatosensory Cortex, Magnetoencephalography

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