Weimer Katja, Horing Björn, Muth Eric R, Enck Paul
Psychosomatic Medicine and Psychotherapy, University Hospital Tübingen;
Department of Psychology, Clemson University.
J Vis Exp. 2014 Dec 14(94):52471. doi: 10.3791/52471.
Placebo responses occur in every medical intervention when patients or participants expect to receive an effective treatment to relieve symptoms. However, underlying mechanisms of placebo responses are not fully understood. It has repeatedly been shown that placebo responses are associated with changes in neural activity but for many conditions it is unclear whether they also affect the target organ, such as the stomach in motion sickness. Therefore, we present a methodology for the multivariate assessment of placebo responses by subjective, behavioral and objective measures in motion sickness with a rotation chair paradigm. The physiological correlate of motion sickness is a shift in gastric myoelectrical activity towards tachygastria that can be recorded with electrogastrography. The presented study applied the so-called balanced placebo design (BPD) to investigate the effects of ginger compared to placebo and the effects of expectations by verbal information. However, the study revealed no significant main or interactional effects of ginger (as a drug) or information on outcome measures but showed interactions when sex of participants and experimenters are taken into considerations. We discuss limitations of the presented study and report modifications that were used in subsequent studies demonstrating placebo responses when rotation speed was lowered. In general, future placebo studies have to identify the appropriate target organ for the studied placebo responses and to apply the specific methods to assess the physiological correlates.
当患者或参与者期望接受有效治疗以缓解症状时，安慰剂反应会出现在每一种医学干预中。然而，安慰剂反应的潜在机制尚未完全明确。研究反复表明，安慰剂反应与神经活动的变化有关，但对于许多病症而言，尚不清楚它们是否也会影响靶器官，比如晕动病中的胃部。因此，我们提出一种方法，通过旋转椅范式，采用主观、行为和客观测量手段对晕动病中的安慰剂反应进行多变量评估。晕动病的生理关联是胃肌电活动向胃动过速转变，这可以通过胃电图记录下来。本研究采用所谓的平衡安慰剂设计（BPD），以研究生姜与安慰剂相比的效果以及言语信息所产生的期望效应。然而，该研究未发现生姜（作为一种药物）或信息对结果测量指标有显著的主效应或交互效应，但在考虑参与者和实验者的性别时显示出交互作用。我们讨论了本研究的局限性，并报告了后续研究中所做的改进，这些改进在降低旋转速度时证明了安慰剂反应。总体而言，未来的安慰剂研究必须确定所研究的安慰剂反应的合适靶器官，并应用特定方法来评估其生理关联。
