Pre-stimulus alpha power affects vertex N2-P2 potentials evoked by noxious stimuli.
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 6-8Hz for alpha 1, 8-10Hz for alpha 2 and 10-12Hz 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.
Babiloni
Claudio
C
Dipartimento di Fisiologia Umana e Farmacologia, Università La Sapienza, Piazzale Aldo Moro 5, Rome, Italy.
Del Percio
Claudio
C
Brancucci
Alfredo
A
Capotosto
Paolo
P
Le Pera
Domenica
D
Marzano
Nicola
N
Valeriani
Massimiliano
M
Romani
Gian Luca
GL
Arendt-Nielsen
Lars
L
Rossini
Paolo Maria
PM
D000328:Adult; D000513:Alpha Rhythm; D000704:Analysis of Variance; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005073:Evoked Potentials, Somatosensory / Q000502:physiology / Q000528:radiation effects*; D005260:Female; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008297:Male; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology / Q000528:radiation effects*; D011930:Reaction Time / Q000502:physiology; D013057:Spectrum Analysis / Q000379:methods