Involuntary orienting of attention to nociceptive events: neural and behavioral signatures.

Pain can involuntarily capture attention and disrupt pain-unrelated cognitive activities. The brain mechanisms of these effects were explored by laser- and visual-evoked potentials. Consecutive nociceptive laser stimuli and visual stimuli were delivered in pairs. Subjects were instructed to ignore nociceptive stimuli while performing a task on visual targets. Because involuntary attention is particularly sensitive to novelty, in some trials (17%), unexpected laser stimuli were delivered on a different hand area (location-deviant) relative to the more frequent standard laser stimuli. Compared with frequent standard laser stimuli, deviant stimuli enhanced all nociceptive-evoked brain potentials (laser N1, N2, P2a, P2b). Deviant laser stimuli also decreased the amplitude of late latency-evoked responses (visual N2-P3) to the subsequent visual targets and delayed reaction times to them. The data confirm that nociceptive processing competes with pain-unrelated cognitive activities for attentional resources and that concomitant nociceptive events affect behavior by depressing attention allocation to ongoing cognitive processing. The laser-evoked potential magnitude reflected the engagement of attention to the novel nociceptive stimuli. We conclude that the laser-evoked potentials index the activity of a neural system involved in the detection of novel salient stimuli in order to focus attention and prioritize action to potentially damaging dangers.