Association and dissociation between laser-evoked potentials and pain perception

Abstract

We investigated the relation between the subjective sensation of pain and two different components of the laser evoked potential, namely the vertex response (N220-P350) and an earlier lateralized response (middle-latency NP160). Brain responses to laser stimuli were obtained in 15 subjects under attentive and distractive conditions. Although stimulus intensity was kept constant, it was perceived as significantly higher when subjects attended the stimulation. There was a positive correlation between subjective intensity perception and the amplitude of the vertex potential, but no correlation existed with the middle-latency component. While laser vertex potentials may reflect attentional/perceptual mechanisms that determine subjective experience, the NP160 behaves as a pre-perceptual sensory response that should be advantageous in the assessment of early cortical pain processing.

Characterizing the Cortical Activity through Which Pain Emerges from Nociception

“…The largest wave is a negative-positive complex maximal at the scalp vertex (N2-P2; peaking at 200 -350 ms when stimulating the hand dorsum) (Bromm and Treede, 1984). This complex is preceded by a smaller negative wave (N1; peaking at ϳ160 ms) maximal over the temporal region contralateral to the stimulated side (García-Larrea et al, 1997). Several studies have shown that these waves reflect a combination of cortical activities originating from primary and secondary somatosensory cortices, the insula, and the anterior cingulate cortex (García-Larrea et al, 2003).…”

Effects of remote cutaneous pain on trigeminal laser-evoked potentials in migraine patients

“…Heterotopic pain should have strongly attracted attention in healthy subjects, and such "distractive" effects are sufficient to attenuate both pain ratings and LEPs to stimulation of another body site. As the effects of distraction are more conspicuous in vertex than in opercular LEPs [23] this might explain the dissociation observed here.…”

“…The DNIC is considered to involve second-order convergent neurons in the dorsal horn, which give rise to the spinothalamic tract [22]; many of the projections from such convergent neurons reach the lateral thalamus, and then the parietal and opercular-insular cortices, where the N1 is generated [23]. It is difficult to conceive how a "massive" inhibitory effect taking place in the dorsal horn affected solely the projections to the cingulate, leaving intact those to the operculum, so we can conceive that the effect was present but not significant for technical limits, i.e., the relief of N1 amplitude solely on the T3 derivation.…”

Detection of pain from nociceptive laser-evoked potentials using single-trial analysis and pattern recognition

“…The well-characterized relationship between the intensity of pain perception and the amplitudes of N2 and P2 of LEPs has been repeatedly confirmed by different research groups [6,8,[16][17]. Therefore, it should be in principle be possible to predict the detection of pain from features of N2 and P2 in LEPs.…”