The experience of pain can be described using two dimensions – sensory and affective-motivational – of which the affective-motivational component is strongly modulated by context and the cognitive appraisal of pain. In pain research, the sensory component is commonly represented by ratings of pain intensity, while the affective component is represented by ratings of pain unpleasantness. However, there is evidence to suggest that test subjects tend to judge pain intensity different from unpleasantness whenever separate scales for both dimensions are presented concurrently. This study used a startle reflex as an objective measure of affective response to stimuli of varying intensities to determine whether the affective component can be abolished when predictable stimulation paradigms are applied.BACKGROUND: Experimental pain research has shown that the affective component of pain is influenced strongly by situational characteristics; affective pain processing appears to be particularly pronounced in situations that provoke a feeling of uncertainty and uncontrollability.OBJECTIVES: To determine whether the affective component of pain can be completely abolished if a ‘safe’, particularly predictable stimulation paradigm is applied.METHOD: Forty healthy volunteers recruited at the University of Bamberg (Bamberg, Germany) were assessed in two experiments. Tonic contact heat stimuli staged in three intensities (warmth, heat and pain) relative to the individual pain threshold was applied; these were predictable with regard to intensity and course, and the subjects had easy access to control. The startle reflex was assessed as an objective measure of affective response. In addition, the subjects provided unpleasantness ratings. To compare these results to a gold standard for affective response, affective pictures taken from the International Affective Picture System were presented during temperature stimulation in the second experiment.RESULTS: Both experiments showed no potentiation of the startle reflex under painful heat stimulation compared with the two nonpainful stimulus intensities (heat and warmth), although the painful stimulation was clearly rated as more unpleasant.CONCLUSIONS: Results suggest that it is possible to develop a ‘safe’ noxious stimulus, which is rated as clearly unpleasant, but lacks physiological indication of negative affect. This divergence might be explained by subjective ratings being influenced by the instructions. The possibility of reducing the pain affect by suggesting ‘safety’ may be of therapeutic interest.

中文翻译：

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疼痛是否必定有情感成分？眨眼反射实验的负面证据

可以通过两个维度来描述疼痛的感受，即感官和情感动机，其中情感动机成分受上下文和对疼痛的认知评估的强烈调节。在疼痛研究中，感觉成分通常用疼痛强度的等级来表示，而情感成分用疼痛不适的等级来表示。但是，有证据表明，只要同时显示两个维度的独立量表，测试对象就倾向于判断疼痛强度与不适感不同。这项研究使用惊吓反射作为对不同强度刺激的情感反应的客观度量，以确定应用可预测的刺激范式是否可以消除情感成分。实验性疼痛研究表明，疼痛的情感成分受情境特征的强烈影响。目的：确定在使用``安全''，特别可预测的刺激范例后，是否可以完全消除疼痛的情感成分。方法：四十健康在两个实验中评估了班贝格大学（德国班贝格）招募的志愿者。相对于个人疼痛阈值，以三种强度（温暖，热和疼痛）分阶段进行滋补接触热刺激。这些在强度和过程方面是可以预见的，并且受试者易于控制。惊吓反射被评估为情感反应的客观指标。另外，受试者提供了不愉快等级。为了将这些结果与情感反应的金标准进行比较，第二个实验在温度刺激过程中展示了从国际情感图片系统拍摄的情感照片。无痛刺激强度（热和温暖），尽管疼痛刺激明显被认为是不愉快的。结论：结果表明，可以开发出一种“安全”的有害刺激，被认为是令人不愉快的，但缺乏阴性生理指标影响。这种差异可以通过受指令影响的主观等级来解释。通过暗示“安全性”减轻疼痛影响的可能性可能具有治疗意义。