Pre-stimulus alpha power affects vertex N2-P2 potentials evoked by noxious stimuli

Claudio Babiloni, Claudio Del Percio, Alfredo Brancucci, Paolo Capotosto, Domenica Le Pera, Nicola Marzano, Massimiliano Valeriani, Gian Luca Romani, Lars Arendt-Nielsen, Paolo Maria Rossini

Research output: Contribution to journalArticlepeer-review


It is well known that scalp potentials evoked by nonpainful visual and auditory stimuli are enhanced in amplitude when preceded by pre-stimulus low-amplitude alpha rhythms. This study tested the hypothesis that the same holds for the amplitude of vertex N2-P2 potentials evoked by brief noxious laser stimuli, an issue of interest for clinical perspective. EEG data were recorded in 10 subjects from 30 electrodes during laser noxious stimulation. The artifact-free vertex N2-P2 complex was spatially enhanced by surface Laplacian transformation. Pre-stimulus alpha power was computed at three alpha sub-bands according to subject's individual alpha frequency peak (i.e. about 6-8 Hz for alpha 1, 8-10 Hz for alpha 2 and 10-12 Hz for alpha 3 sub-band). Individual EEG single trials were divided in two sub-groups. The strong-alpha sub-group (high band power) included halfway of all EEG single trials, namely those having the highest pre-stimulus alpha power. Weak-alpha sub-group (low band power) included the remaining trials. Averaging procedure provided laser evoked potentials for both trial sub-groups. No significant effect was found for alpha 1 and alpha 2 sub-bands. Conversely, compared to strong-alpha 3 sub-group, weak-alpha 3 sub-group showed vertex N2-P2 potentials having significantly higher amplitude (p <0.05). These results extend to the later phases of pain processing systems the notion that generation mechanisms of pre-stimulus alpha rhythms and (laser) evoked potentials are intrinsically related and subjected to fluctuating "noise". That "noise" could explain the trial-by-trial variability of laser evoked potentials and perception.

Original languageEnglish
Pages (from-to)581-590
Number of pages10
JournalBrain Research Bulletin
Issue number5
Publication statusPublished - Mar 28 2008


  • CO laser
  • Laser evoked potentials (LEPs)
  • Noxious stimulation
  • Pre-stimulus alpha rhythms
  • Vertex N2-P2 complex

ASJC Scopus subject areas

  • Neuroscience(all)


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