Center for Neuroplasticity and Pain (CNAP), SMI, Aalborg University, Aalborg, Denmark.
Department of Neural and Pain Sciences, Center to Advance Chronic Pain Research, School of Dentistry, University of Maryland, Baltimore, MD, USA.
Eur J Pain. 2019 Nov;23(10):1850-1862. doi: 10.1002/ejp.1458. Epub 2019 Aug 12.
Efficacy of pain modulation is assessed as the difference in pain sensitivity during a painful conditioning, compared to before (conditioning pain modulation, CPM). Attention can be assessed with the Stroop task, in which participants report the number of words on a screen; either congruent or incongruent with the value of the words. Attention away from painful stimuli during CPM enhances the CPM effect. However, it is unknown if attention influences CPM effects when the two are done in sequence.
Healthy men (n = 25) underwent cuff algometry CPM-assessment where the pressure-pain detection and tolerance thresholds (PTT) were recorded on one leg with and without contralateral conditioning. Two identical sessions of four test stimuli equal to PTT (5 s, 1-min interval, scored on a visual analogue scale, VAS) with a painful conditioning from the second to the last test-stimulus were performed. Stroop sessions were followed by test stimuli with or without painful conditioning.
The VAS scores in the first two sessions showed excellent reliability (ICC = 0.92). VAS scores were lower in sessions with Stroop compared to sessions without Stroop (p = .05) indicating an analgesic effect of Stroop. Participants were subgrouped into CPM responders and CPM non-responders according to CPM effects in the first two sessions. CPM non-responders (n = 13) showed facilitation to repeated noxious stimuli in all sessions with no effect of conditioning or Stroop (p = .02).
Attention and CPM both modulate pain in healthy men. Attention-induced analgesia works in CPM non-responders. Results indicate that attention and CPM are not the same and that they do not demonstrate additive effects when applied in sequence.
Pain sensitivity is reduced after an attention task in healthy men. The delayed effects from attention only have minor effects on Conditioned Pain Modulation (CPM), and results support that attention-driven analgesia works independently of CPM. Results indicate that individual strategies for pain inhibition exist and that an overlap between the mechanisms of CPM and selective attention is limited. Moreover, painful phasic stimuli may increase the number of healthy volunteers with negative CPM effects.
疼痛调节的疗效是通过比较疼痛条件作用期间与之前的疼痛敏感性差异来评估的（条件性疼痛调节，CPM）。可以使用 Stroop 任务来评估注意力，参与者报告屏幕上的单词数量；与单词的数值一致或不一致。CPM 期间将注意力从疼痛刺激上转移可以增强 CPM 效应。然而，当两者按顺序进行时，注意力是否会影响 CPM 效应尚不清楚。
健康男性（n=25）接受袖带测痛 CPM 评估，其中一条腿的压力-疼痛检测和耐受阈值（PTT）在有和没有对侧条件作用的情况下记录。进行了两次相同的四个测试刺激的四个测试刺激（5 秒，1 分钟间隔，在视觉模拟量表上评分，VAS），在第二个到最后一个测试刺激之间进行疼痛条件作用。Stroop 之后进行了有或没有疼痛条件作用的测试刺激。
前两个测试刺激的 VAS 评分显示出极好的可靠性（ICC=0.92）。与没有 Stroop 的测试刺激相比，有 Stroop 的测试刺激的 VAS 评分较低（p=0.05），表明 Stroop 具有镇痛作用。根据前两个测试刺激的 CPM 效应，参与者被分为 CPM 反应者和 CPM 非反应者亚组。CPM 非反应者（n=13）在所有测试刺激中均表现出对重复有害刺激的易化作用，而无条件作用或 Stroop 作用（p=0.02）。
注意力和 CPM 均可调节健康男性的疼痛。注意力诱导的镇痛作用在 CPM 非反应者中起作用。结果表明，注意力和 CPM 不同，当按顺序应用时，它们不会表现出相加效应。
健康男性在注意力任务后疼痛敏感性降低。注意力的延迟效应仅对条件性疼痛调节（CPM）有较小影响，结果支持注意力驱动的镇痛作用独立于 CPM 起作用。结果表明，存在个体的疼痛抑制策略，CPM 和选择性注意的机制之间存在有限的重叠。此外，疼痛的阵发性刺激可能会增加具有负 CPM 效应的健康志愿者数量。
