Background

Many studies have shown effects of anodal transcranial direct current stimulation (a-tDCS) and high-frequency transcranial random noise stimulation (tRNS) on elevating cortical excitability. Moreover, tRNS with a direct current (DC)-offset is more likely to lead to increases in cortical excitability than solely tRNS. While a-tDCS over primary motor cortex (M1) has been shown to attenuate pain perception, tRNS + DC-offset may prove as an effective means for pain relief.

Objective

This study aimed to examine effects of a-tDCS and high-frequency tRNS + DC-offset over M1 on pain expectation and perception, and assess whether these effects could be influenced by the certainty of pain expectation.

Methods

Using a double-blinded and sham-controlled design, 150 healthy participants were recruited to receive a single-session a-tDCS, high-frequency tRNS + DC-offset, or sham stimulation over M1. The expectation and perception of electrical stimulation in certain and uncertain contexts were assessed at baseline, immediately after, and 30 min after stimulation.

Results

Compared with sham stimulation, a-tDCS induced immediate analgesic effects that were greater when the stimulation outcome was expected with uncertainty; tRNS induced immediate and sustained analgesic effects that were mediated by decreasing pain expectation. Nevertheless, we found no strong evidence for tRNS being more effective for attenuating pain than a-tDCS.

Conclusions

The analgesic effects of a-tDCS and tRNS showed different temporal courses, which could be related to the more sustained effectiveness of high-frequency tRNS + DC-offset in elevating cortical excitability. Moreover, expectations of pain intensity should be taken into consideration to maximize the benefits of neuromodulation.

中文翻译：

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阳极 tDCS 和运动皮层高频 tRNS 诱导的镇痛：对疼痛感知的即时和持续影响

背景

许多研究表明阳极经颅直流电刺激 (a-tDCS) 和高频经颅随机噪声刺激 (tRNS) 对提高皮质兴奋性的影响。此外，与单独的 tRNS 相比，具有直流 (DC) 偏移的 tRNS 更可能导致皮质兴奋性增加。虽然初级运动皮层 (M1) 上的 a-tDCS 已被证明可以减轻疼痛感知，但 tRNS + DC-offset 可能被证明是缓解疼痛的有效手段。

客观的

本研究旨在检查 a-tDCS 和高频 tRNS + DC 偏移对 M1 的疼痛预期和感知的影响，并评估这些影响是否会受到疼痛预期确定性的影响。

方法

使用双盲和假控制设计，招募 150 名健康参与者接受单次 a-tDCS、高频 tRNS + DC 偏移或 M1 上的假刺激。在基线、刺激后立即和刺激后 30 分钟评估在某些和不确定的环境中对电刺激的期望和感知。

结果

与假刺激相比，a-tDCS 诱导的即时镇痛效果在预期刺激结果不确定时更大；tRNS 诱导立即和持续的镇痛作用，通过降低疼痛预期介导。然而，我们没有发现 tRNS 在减轻疼痛方面比 a-tDCS 更有效的有力证据。

结论

a-tDCS 和 tRNS 的镇痛作用表现出不同的时间过程，这可能与高频 tRNS + DC-offset 在提高皮质兴奋性方面的更持久有效性有关。此外，应考虑对疼痛强度的预期，以最大限度地发挥神经调节的益处。