Department of Cognitive and Clinical Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.
Integrative Spinal Research Group, Department of Chiropractic Medicine, University Hospital Balgrist, University of Zurich, Zurich, Switzerland.
Eur J Pain. 2021 Sep;25(8):1702-1711. doi: 10.1002/ejp.1775. Epub 2021 May 6.
The ultimate goal of pain research is to provide effective routes for pain relief. Nevertheless, the perception pain relief as a change in pain intensity and un-/pleasantness has only been rarely investigated. It has been demonstrated that pain relief has rewarding and reinforcing properties, but it remains unknown whether the perception of pain relief changes when pain reductions occur repeatedly. Further, it remains an open question whether the perception of pain relief depends on the controllability of the preceding pain.
In this study, healthy volunteers (N = 38) received five cycles of painful heat stimulation and reduction of this stimulation to a non-painful warm stimulation once in a condition with control of the stimulation and once without control. Participants rated perceived intensity and un-/pleasantness on visual analogue scales during the heat stimulation and immediately after its reduction.
Results showed that perceived pain relief, estimated by the difference in ratings during ongoing heat stimulation and after its reduction, increased with repetitions. However, this increase levelled off after two to four repetitions. Further, perceived pain relief was larger in the condition without control compared to the condition with control.
The perception of pain relief can be modulated similar to the perception of pain by stimulus characteristics and psychological factors. Mechanistic knowledge about such modulating factors is important, because they can determine, e.g., the amount of requested pain killers in clinical settings and the efficacy of pain relief as a reinforcing stimulus.
When in pain, pain relief can become an all-dominate goal. The perception of such pain relief can vary depending on external and internal characteristics and thus modulate, e.g., requests for pain killers in clinical settings. Here, we show that perceived intensity and pleasantness of pain relief changes with repetitions and whether the preceding pain is perceived as uncontrollable. Such mechanistic knowledge needs to be considered to maximize the effects of pain relief as a rewarding and reinforcing stimulus.
疼痛研究的最终目标是提供有效的止痛途径。然而，将疼痛缓解感知为疼痛强度和不舒适/舒适程度的变化，这一观点很少被研究。已经证明，疼痛缓解具有奖励和强化的特性，但尚不清楚当疼痛减少反复发生时，疼痛缓解的感知是否会发生变化。此外，疼痛缓解的感知是否取决于先前疼痛的可控性，这仍然是一个悬而未决的问题。
在这项研究中，健康志愿者（N=38）接受了五次热刺激疼痛和将这种刺激减少到非疼痛的温暖刺激的循环，一次是在有控制的刺激条件下，一次是在没有控制的刺激条件下。参与者在热刺激期间和刺激减少后立即使用视觉模拟量表（VAS）来评估感知强度和不舒适/舒适程度。
结果表明，通过在持续热刺激期间的评分与刺激减少后的评分之间的差异来估计的感知疼痛缓解随着重复次数的增加而增加。然而，这种增加在两到四次重复后趋于平稳。此外，在没有控制的条件下，感知的疼痛缓解比在有控制的条件下更大。
疼痛缓解的感知可以像刺激特征和心理因素一样调节疼痛的感知。对这种调节因素的机制性了解是很重要的，因为它们可以确定，例如，在临床环境中请求止痛药的数量和疼痛缓解作为强化刺激的效果。
当处于疼痛中时，疼痛缓解可能成为一个主导目标。这种疼痛缓解的感知可以根据外部和内部特征而变化，从而调节，例如，在临床环境中对止痛药的请求。在这里，我们表明，疼痛缓解的感知强度和舒适度随着重复次数的变化而变化，以及先前的疼痛是否被感知为不可控。这种机制性的知识需要被考虑，以最大限度地发挥疼痛缓解作为奖励和强化刺激的效果。
