Almarzouki Abeer F, Brown Christopher A, Brown Richard J, Leung Matthew H K, Jones Anthony K P
Physiology Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.
Department of Psychological Sciences, Institute of Psychology, Health and Society, University of Liverpool, Liverpool, United Kingdom.
PLoS One. 2017 Jun 30;12(6):e0180006. doi: 10.1371/journal.pone.0180006. eCollection 2017.
It is well known that the efficacy of treatment effects, including those of placebos, is heavily dependent on positive expectations regarding treatment outcomes. For example, positive expectations about pain treatments are essential for pain reduction. Such positive expectations not only depend on the properties of the treatment itself, but also on the context in which the treatment is presented. However, it is not clear how the preceding threat of pain will bias positive expectancy effects. One hypothesis is that threatening contexts trigger fearful and catastrophic thinking, reducing the pain-relieving effects of positive expectancy. In this study, we investigated the disruptive influence of threatening contexts on positive expectancy effects while 41 healthy volunteers experienced laser-induced heat pain. A threatening context was induced using pain-threatening cues that preceded the induction of positive expectancies via subsequent pain-safety cues. We also utilised electroencephalography (EEG) to investigate potential neural mechanisms underlying these effects. Lastly, we used the Fear of Pain Questionnaire to address whether the disruptive effect of negative contexts on cued pain relief was related to the degree of fear of pain. As predicted, participants responded less to pain-safety cues (i.e., experienced more pain) when these were preceded by pain-threatening cues. In this threatening context, an enhancement of the N2 component of the laser-evoked potential was detected, which was more pronounced in fearful individuals. This effect was localised to the midcingulate cortex, an area thought to integrate negative affect with pain experience to enable adaptive behaviour in aversive situations. These results suggest that threatening contexts disrupt the effect of pain relief cues via an aversive priming mechanism that enhances neural responses in the early stages of sensory processing.
众所周知，治疗效果的功效，包括安慰剂的功效，在很大程度上取决于对治疗结果的积极期望。例如，对疼痛治疗的积极期望对于减轻疼痛至关重要。这种积极期望不仅取决于治疗本身的特性，还取决于治疗呈现的背景。然而，尚不清楚先前的疼痛威胁将如何影响积极期望效应。一种假设是，威胁性背景会引发恐惧和灾难性思维，从而降低积极期望的止痛效果。在本研究中，我们调查了威胁性背景对积极期望效应的干扰影响，当时41名健康志愿者经历了激光诱导的热痛。通过在随后的疼痛安全线索引发积极期望之前使用疼痛威胁线索来诱导威胁性背景。我们还利用脑电图（EEG）来研究这些效应背后的潜在神经机制。最后，我们使用疼痛恐惧问卷来探讨负面背景对提示性疼痛缓解的干扰效应是否与疼痛恐惧程度有关。正如预期的那样，当疼痛安全线索之前有疼痛威胁线索时，参与者对疼痛安全线索的反应较小（即经历更多疼痛）。在这种威胁性背景下，检测到激光诱发电位的N2成分增强，在恐惧个体中更为明显。这种效应定位于扣带回中部皮质，该区域被认为将负面情绪与疼痛体验整合起来，以便在厌恶情境中实现适应性行为。这些结果表明，威胁性背景通过一种厌恶启动机制破坏疼痛缓解线索的效果，该机制增强了感觉处理早期阶段的神经反应。
