Pain Processing in a Social Context and the Link with Psychopathic Personality Traits-An Event-Related Potential Study.

Empathy describes the ability to understand another person's feelings. Psychopathy is a disorder that is characterized by a lack of empathy. Therefore, empathy and psychopathy are interesting traits to investigate with respect to experiencing and observing pain. The present study aimed to investigate pain empathy and pain sensitivity by measuring event-related potentials (ERPs) extracted from the ongoing EEG in an interactive setup. Each participant fulfilled subsequently the role of "villain" and "victim". In addition, mode of control was modulated resulting in four different conditions; passive villain, active villain, active victim and passive victim. Response-, visual- and pain ERPs were compared between the four conditions. Furthermore, the role of psychopathic traits in these outcomes was investigated. Our findings suggested that people experience more conflict when hurting someone else than hurting themselves. Furthermore, our results indicated that self-controlled pain was experienced as more painful than uncontrolled pain. People that scored high on psychopathic traits seemed to process and experience pain differently. According to the results of the current study, social context, attention and personality traits seem to modulate pain processing and the empathic response to pain in self and others. The within-subject experimental design described here provides an excellent approach to further unravel the influence of social context and personality traits on social cognition.

Evidence for a Priori Existence of Attentional Bias Subgroups in Emotional Processing of Aversive Stimuli.

Little is known regarding inter-individual differences in attentional biases for pain-related information; more knowledge is crucial, since these biases have been associated with differences in pain processing as well as in predicting the risk of postoperative pain. The present study investigated EEG correlates of attentional bias patterns for pain-related information, with specific focus on avoidance- and vigilance-like behavior. Forty-one participants performed a dot-probe task, where neutral and pain-related words were used to create neutral, congruent, incongruent, and double (two pain-related words) trials. EEG was recorded, which was used to generate ERP's of the word-processing phase and the post-dot phase. Participants were placed in two subgroups based on the direction of their attentional bias (either positive; toward the pain-related words, or negative; away from pain-related words). Using t-profiles, four latency windows were identified on which the two subgroups differed significantly. These latency windows yield areas which correspond with the P1-N1 domain and the P3b for the word-processing phase, while the post-dot phase latency windows cover the areas of the P200 and the P3b. The two subgroups show differences on congruent, incongruent, and the double trials, but interestingly also on the neutral trials. Most notably, the area in the word-phase associated with the P3b is diminished in the subgroup showing a negative bias. The deflections associated with both early and late attentional components, including the P3B, as well as a positive deflection in the timeframe of proposed response evaluation processes differ significantly between subgroups. In this study we demonstrated that different attentional biases exist in the healthy population, by showing differences in ERP's. We also show differences in processing neutral trials, which suggests there are fundamental differences between these groups in processing words in general.

The effect of high-frequency conditioning stimulation of human skin on reported pain intensity and event-related potentials.

High-frequency conditioning electrical stimulation (HFS) of human skin induces an increased pain sensitivity to mechanical stimuli in the surrounding nonconditioned skin. The aim of this study was to investigate the effect of HFS on reported pain sensitivity to single electrical stimuli applied within the area of conditioning stimulation. We also investigated the central nervous system responsiveness to these electrical stimuli by measuring event-related potentials (ERPs). Single electrical test stimuli were applied in the conditioned area before and 30 min after HFS. During electrical test stimulation, the reported pain intensity (numerical rating scale) and EEG (ERPs) were measured. Thirty minutes after conditioning stimulation, we observed a decrease of reported pain intensity at both the conditioned and control (opposite arm) skin site in response to the single electrical test stimuli. In contrast, we observed enhanced ERP amplitudes after HFS at the conditioned skin site, compared with control site, in response to the single electrical test stimuli. Recently, it has been proposed that ERPs, at least partly, reflect a saliency detection system. Therefore, the enhanced ERPs might reflect enhanced saliency to potentially threatening stimuli.

Neural correlates of heterotopic facilitation induced after high frequency electrical stimulation of nociceptive pathways.

BACKGROUND: High frequency electrical stimulation (HFS) of primary nociceptive afferents in humans induce a heightened sensitivity in the surrounding non-stimulated skin area. Several studies suggest that this heterotopic effect is the result of central (spinal) plasticity. The aim of this study is to investigate HFS-induced central plasticity of sensory processing at the level of the brain using the electroencephalogram (EEG). To this end we measured evoked potentials in response to noxious electrical pinprick-like stimuli applied in the heterotopic skin area before, directly after and 30 minutes after HFS. RESULTS: We observed potential cortical electrophysiological correlates of heterotopic facilitation. Two different cortical correlates were found; the first one was a lateralized effect, i.e. a larger N100 amplitude on the conditioned arm than the control arm 30 minutes after end of HFS. This was comparable with the observed lateralized effect of visual analogue scale (VAS) scores as response to the mechanical punctate stimuli. The second correlate seems to be a more general (non-lateralized) effect, because the result affects both arms. On average for both arms the P200 amplitude increased significantly 30 minutes after end of HFS with respect to baseline. CONCLUSIONS: We suggest that for studying heterotopic nociceptive facilitation the evoked brain response is suitable and relevant for investigating plasticity at the level of the brain and is perhaps a more sensitive and reliable marker than the perceived pain intensity (e.g. VAS).