Vigilance for pain-related faces in a primary task paradigm: an ERP study

Pain-related stimuli are supposed to be automatically prioritized over other stimuli. This prioritization has often been tested using primary task paradigms in which pain information is irrelevant for completing the explicitly posed task. Task-irrelevant stimuli are only processed if they are very salient, and pain-related stimuli are assumed to be salient enough.

We wanted to further investigate this assumption by assessing event-related brain potentials (ERPs) - a very sensitive method for studying attention and reaction times in response to pictures of people in pain and other emotional faces - using a primary task paradigm. In addition, we assumed that individuals describing themselves as vigilant to pain are especially responsive to pain cues.

One hundred pain-free subjects were tested in a primary task paradigm using pictures of facial expressions of pain, anger, happiness, and neutral mood. ERPs were assessed at midline electrodes. Vigilance to pain was assessed by the pain vigilance and awareness questionnaire.

In contrast to previous studies (which have used pain words), effects of facial expressions of pain and other emotions on the ERPs and reaction times were surprisingly weak throughout and did not give evidence for a distinct processing of pain-related stimuli. However, hypervigilant subjects appeared to be strongly and cognitively absorbed by all emotional stimuli.

Accordingly, it appears that pain-related stimuli are not always of outstanding salience, but that certain characteristics (eg, type of material, emotional richness) have to be present, for pain-related stimuli to be prioritized over stimuli of other emotional content. Hypervigilance to pain may generally predispose individuals to process emotional stimuli in greater depth.