Background Maladaptive defensive responses such as excessive avoidance behavior have received increasing attention as a main mechanism for the development and maintenance of chronic pain complaints. However, another defensive response which is commonly studied in animals as a proxy for fear is freezing behavior. No research to date has investigated human freezing behavior in the context of pain. In addition, there is an increasing realization that social context can affect pain-relevant processes such as pain experience and pain behavior but less is known about the effects of social context on defensive responses to pain. Hence, this study investigated freezing behavior and facial pain expression in the context of pain, and their modulation by social context. Methods Healthy, pain-free participants (N = 39) stood on a stabilometric force platform in a threatening or safe social context, which was manipulated using angry or happy facial stimuli. In some trials, an auditory cue (conditioned stimulus; CS) predicted the occurrence of painful electrocutaneous stimulus (unconditioned stimulus; pain-US). We assessed body sway (an index of freezing), heart rate, facial pain expression, self-reported pain intensity, unpleasantness, and pain-US expectancy during the CS and the context alone (no CS). Results The results were mixed. Neither the anticipation of pain, nor social context affected body sway. Heart rate and painful facial expression were reduced in the threatening social context at high anxiety levels. A threatening social context also elicited higher pain-US expectancy ratings. In sum, a threatening social context increases the expectation of pain, but reduces the facial expression of pain and lowers heart rate in highly anxious individuals.

中文翻译：

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对人类疼痛的冻结样反应及其受社会背景的调节

背景 过度回避行为等适应不良的防御反应作为慢性疼痛主诉发展和维持的主要机制已受到越来越多的关注。然而，另一种通常在动物身上研究的作为恐惧代表的防御反应是冻结行为。迄今为止，还没有研究调查过疼痛背景下的人类冻结行为。此外，人们越来越意识到社会背景可以影响与疼痛相关的过程，例如疼痛体验和疼痛行为，但人们对社会背景对疼痛防御反应的影响知之甚少。因此，本研究调查了疼痛背景下的冻结行为和面部疼痛表达，以及它们受社会背景的调节。方法健康，无痛参与者 (N = 39) 在威胁或安全的社会环境中站在稳定力平台上，该平台使用愤怒或快乐的面部刺激进行操纵。在一些试验中，听觉提示（条件刺激；CS）可以预测疼痛的皮肤电刺激（非条件刺激；pain-US）的发生。我们评估了 CS 期间的身体摇摆（冻结指数）、心率、面部疼痛表情、自我报告的疼痛强度、不愉快感和疼痛-US 预期值以及单独的上下文（无 CS）。结果 结果喜忧参半。对疼痛的预期和社会背景都不会影响身体的摇摆。在高焦虑水平的威胁性社交环境中，心率和痛苦的面部表情会降低。具有威胁性的社会背景也引发了更高的疼痛-美国期望评级。总共，