Dehghani Amin, Bango Carmen, Murphy Ethan K, Halter Ryan J, Wager Tor D
Department of Psychological and Brain Sciences, Dartmouth College, Hanover, NH, United States.
Thayer School of Engineering and Geisel School of Medicine, Dartmouth College, Hanover, NH, United States.
Pain. 2025 Jan 1;166(1):87-98. doi: 10.1097/j.pain.0000000000003338. Epub 2024 Jul 12.
Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulatory technique with the potential to provide pain relief. However, tDCS effects on pain are variable across existing studies, possibly related to differences in stimulation protocols and expectancy effects. We investigated the independent and joint effects of contralateral motor cortex tDCS (anodal vs cathodal) and socially induced expectations (analgesia vs hyperalgesia) about tDCS on thermal pain. We employed a double-blind, randomized 2 × 2 factorial cross-over design, with 5 sessions per participant on separate days. After calibration in Session 1, Sessions 2 to 5 crossed anodal or cathodal tDCS (20 minutes 2 mA) with socially induced analgesic or hyperalgesic expectations, with 6 to 7 days between the sessions. The social manipulation involved videos of previous "participants" (confederates) describing tDCS as inducing a low-pain state ("analgesic expectancy") or hypersensitivity to sensation ("hyperalgesic expectancy"). Anodal tDCS reduced pain compared with cathodal stimulation (F(1,19.9) = 19.53, P < 0.001, Cohen d = 0.86) and analgesic expectancy reduced pain compared with hyperalgesic expectancy (F(1,19.8) = 5.62, P = 0.027, Cohen d = 0.56). There was no significant interaction between tDCS and social expectations. Effects of social suggestions were related to expectations, whereas tDCS effects were unrelated to expectancies. The observed additive effects provide novel evidence that tDCS and socially induced expectations operate through independent processes. They extend clinical tDCS studies by showing tDCS effects on controlled nociceptive pain independent of expectancy effects. In addition, they show that social suggestions about neurostimulation effects can elicit potent placebo effects.
经颅直流电刺激（tDCS）是一种无创神经调节技术，具有缓解疼痛的潜力。然而，在现有研究中，tDCS对疼痛的影响存在差异，这可能与刺激方案和预期效应的不同有关。我们研究了对侧运动皮层tDCS（阳极刺激与阴极刺激）以及关于tDCS的社会诱导期望（镇痛与痛觉过敏）对热痛的独立和联合效应。我们采用了双盲、随机的2×2析因交叉设计，每位参与者在不同日期进行5次实验。在第1次实验进行校准后，第2至5次实验将阳极或阴极tDCS（20分钟，2毫安）与社会诱导的镇痛或痛觉过敏期望相结合，每次实验之间间隔6至7天。社会操纵包括播放之前“参与者”（同谋）的视频，将tDCS描述为诱导低疼痛状态（“镇痛期望”）或对感觉过敏（“痛觉过敏期望”）。与阴极刺激相比，阳极tDCS减轻了疼痛（F(1,19.9)=19.53，P<0.001，Cohen d=0.86），与痛觉过敏期望相比，镇痛期望减轻了疼痛（F(1,19.8)=5.62，P=0.027，Cohen d=0.56）。tDCS与社会期望之间没有显著的交互作用。社会建议的效果与期望有关，而tDCS的效果与期望无关。观察到的叠加效应提供了新的证据，表明tDCS和社会诱导期望通过独立的过程起作用。它们扩展了临床tDCS研究，表明tDCS对可控伤害性疼痛的影响独立于期望效应。此外，它们表明关于神经刺激效果的社会建议可以引发强大的安慰剂效应。
