Rhudy Jamie L, Williams Amy E, McCabe Klanci M, Rambo Philip L, Russell Jennifer L
Department of Psychology, The University of Tulsa, 600 South College Ave., Tulsa, OK 74104, USA.
Pain. 2006 Dec 15;126(1-3):221-33. doi: 10.1016/j.pain.2006.06.027. Epub 2006 Aug 4.
Recent evidence suggests that emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. The present study attempted to replicate these findings and determine the effect of noxious stimulus predictability. Participants viewed pictures from the International Affective Picture System (IAPS), during which pain and nociceptive flexion reflexes (NFR) were elicited by electric shocks delivered to the sural nerve. For half of the participants (n=25) shocks were preceded by a cue (predictable), whereas the other half received no cue (unpredictable). Results suggested emotion was successfully induced by pictures, but the effect of picture-viewing on the NFR was moderated by the predictability of the shocks. When shock was unpredictable, spinal nociception (NFR) and pain ratings were modulated in parallel. Specifically, pain and NFR magnitudes were lower during pleasant emotions and higher during unpleasant emotions. However, when shocks were predictable, only pain was modulated in this way. NFRs from predictable shocks were not altered by pictures. Further, exploratory analyses found that pain ratings, but not NFRs, were lower during predictable shocks. These data suggest emotional picture-viewing is a reliable method of engaging descending modulation of spinal nociception. However, descending modulation could not be detected in NFRs resulting from predictable noxious stimuli. Although preliminary, this study implies that separate mechanisms are responsible for emotional modulation of nociception at spinal vs. supraspinal levels, and that predictable noxious events may disengage modulation at the spinal level. The current paradigm could serve as a useful tool for studying descending modulation.
近期证据表明,观看情绪性图片是一种引发脊髓伤害性感受下行调制的可靠方法。本研究试图重复这些发现,并确定有害刺激可预测性的影响。参与者观看了国际情绪图片系统(IAPS)中的图片,在此期间,通过向腓肠神经施加电击来诱发疼痛和伤害性屈曲反射(NFR)。对于一半的参与者(n = 25),电击之前有一个提示(可预测),而另一半则没有提示(不可预测)。结果表明图片成功诱发了情绪,但观看图片对NFR的影响受到电击可预测性的调节。当电击不可预测时,脊髓伤害性感受(NFR)和疼痛评分平行调制。具体而言,在愉快情绪期间,疼痛和NFR幅度较低,而在不愉快情绪期间较高。然而,当电击可预测时,只有疼痛以这种方式被调制。来自可预测电击的NFR不受图片影响。此外,探索性分析发现,在可预测电击期间,疼痛评分较低,但NFR没有变化。这些数据表明观看情绪性图片是一种引发脊髓伤害性感受下行调制的可靠方法。然而,在由可预测的有害刺激引起的NFR中未检测到下行调制。尽管是初步的,但本研究表明,脊髓和脊髓上水平的伤害性感受情绪调制由不同机制负责,并且可预测的有害事件可能会在脊髓水平解除调制。当前的范式可作为研究下行调制的有用工具。