Effects of High-Definition Transcranial Direct Current Stimulation Targeting the Anterior Cingulate Cortex on the Pain Thresholds: A Randomized Controlled Trial

Abstract

Background The majority of existing clinical studies used active transcranial direct current stimulation (tDCS) over the superficial areas of pain neuromatrix to regulate pain, with conflicting results. Nevertheless, few studies have investigated the effect of tDCS on pain thresholds by focusing on targets in deep parts of the pain neuromatrix. Methods This study applied single session of high-definition tDCS (HD-tDCS) targeting the anterior cingulate cortex (ACC) with a parallel and sham-controlled design, to compare the antinociceptive effects in healthy individuals through assessing changes in pain thresholds. Sixty-six (mean age, 20.5 ± 2.4) female individuals were randomly allocated into the anodal, cathodal, or sham HD-tDCS groups. The primary outcome of the study was pain thresholds (pressure pain threshold, heat pain threshold, and cold pain threshold), which were evaluated before and after stimulation by the quantitative sensory tests. Results Only cathodal HD-tDCS targeting the ACC significantly increased heat pain threshold (p < 0.05) and pressure pain threshold (p < 0.01) in healthy individuals compared with sham stimulation. Neither anodal nor cathodal HD-tDCS showed significant analgesic effects on cold pain threshold. Furthermore, no statistically significant difference was found in pain thresholds between anodal vs. sham HD-tDCS (p > 0.38). Independent of HD-tDCS protocols, the positive and negative affective schedule scores were decreased immediately after stimulation compared with baseline. Conclusions The present study has found that cathodal HD-tDCS targeting the ACC provided a strong antinociceptive effect (increase in pain threshold), demonstrating a positive biological effect of HD-tDCS. Clinical Trials Registration An RCT was carried out at Shanghai University of Sport, China, from December 2021 to March 2022. Trial registration: ChiCTR2100053531. Registered 24 November 2021, http://www.chictr.org.cn/index.aspx.

Transcranial Direct Current Stimulation (tDCS) Effects on Quantitative Sensory Testing (QST) and Nociceptive Processing in Healthy Subjects: A Systematic Review and Meta-Analysis

“…Finally, 29 studies [5,9,17,[19][20][21][22][23][24][25][26][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] were included in the qualitative analysis, and 17 [5,9,17,[19][20][21]24,26,40,43,44,46,48,50,53,55,56] were included in the quantitative analysis, with a total of 700 subjects. The whole screening process is shown in the PRISMA flow diagram (Figure 1).…”

“…Among the selected studies, most of the studies applied a-tDCS over M1 [5,9,19,[21][22][23][24][25]40,[42][43][44][47][48][49][50][55][56][57], and other studies applied a-tDCS over DLPFC [9,22,26,43,47,[51][52][53][54], S1 [24,53], and SO [19]. Six studies applied c-tDCS over M1 [21,24,40,47,54,57], two over DLPFC [26,47], two over S1 [45,48], and one over ACC [17]. Seven studies applied HD-tDCS [9,17,22,23,42,52,55].…”

“…Six studies applied c-tDCS over M1 [21,24,40,47,54,57], two over DLPFC [26,47], two over S1 [45,48], and one over ACC [17]. Seven studies applied HD-tDCS [9,17,22,23,42,52,55]. Regarding current density, five applied a current density of 0.028 mA/cm 2 [21,24,41,45], two applied 0.04 mA/cm 2 [19,44], nine applied 0.057 mA/cm 2 [5,25,26,40,46,47,50,57], and one applied 0.1 mA/cm 2 [53]; the rest of the studies did not report current density.…”

“…Regarding stimulation time, one applied tDCS for 7 min [38], three for 10 min [23,52], five for 15 min [21,24,41,45,57], eighteen for 20 min [5,9,19,22,26,[42][43][44][47][48][49][50][51][53][54][55][56], and one for 40 min [46]. Most studies conducted single treatment sessions [5,17,19,21,23,25,26,[40][41][42][43][45][46][47]50,52,[55][56][57], and the rest between three and five sessions [9,22,24,44,51,…”

“…Regarding outcome measures, 12 measured PPTs [9,17,19,[21][22][23]41,44,45,48,52,53,55], 13 measured VAS or NRS [5,21,24,40,43,46,47,49,51,54,56], 10 measured HPTs [5,9,17,21,24,26,40,41,45,48], and 13 measured CPTs [9,17,19,22,25,[41][42][43]45,[47][48][49]57].…”