Effect of acupuncture 'dose' on modulation of the default mode network of the brain

Abstract

Objective: Recent functional MRI (fMRI) studies show that brain activity, including the default mode network (DMN), can be modulated by acupuncture. Conventional means to enhance the neurophysiological 'dose' of acupuncture, including an increased number of needles and manual needle manipulation, are expected to enhance its physiological effects. The aim of this study was to compare the effects of both methods on brain activity.

Methods: 58 healthy volunteers were randomly assigned into four groups that received single needle acupuncture (SNA, n=15) or transcutaneous electrical nerve stimulation (TENS, n=13) as active controls, or enhanced acupuncture by way of three needle acupuncture (TNA, n=17) or SNA plus manual stimulation (SNA+MS, n=13). Treatment-associated sensations were evaluated using a visual analogue scale. Central responses were recorded before, during, and after treatment at LI4 on the left hand using resting state fMRI.

Results: TNA and SNA+MS induced DMN-insula activity and extensive DMN activity compared to SNA, despite comparable levels of de qi sensation. The TNA and SNA+MS groups exhibited a delayed and enhanced modulation of the DMN, which was not observed followed SNA and TENS. Furthermore, TNA increased precuneus activity and increased the DMN-related activity of the cuneus and left insula, while SNA+MS increased activity in the right insula.

Conclusions: The results showed that conventional methods to enhance the acupuncture dose induce different DMN modulatory effects. TNA induces the most extensive DMN modulation, compared with other methods. Conventional methods of enhancing the acupuncture dose could potentially be applied as a means of modulating brain activity.

Keywords: ACUPUNCTURE; NEUROLOGY.

Figure 1

(A) Schematic representation of experimental protocols for three needle acupuncture (TNA), single needle acupuncture (SNA) with or without manual stimulation (MS) and transcutaneous electrical nerve stimulation (TENS). Vertical black lines indicate needles. Ovals indicate acupuncture points, with the middle one representing LI4. The black circle with an arrow indicates MS. ‘∼’ indicates TENS. (B) Photograph of participant receiving TNA. (C) In TNA and SNA groups, needles were retained for 15 mins. (D) In SNA+MS and TENS groups, nine blocks of manipulation/stimulation were applied. In all groups, three fMRI scans were acquired, specifically a first scan (session 1) that was carried out before treatment, a second scan (session 2) that was carried out 9 min into treatment, and a third scan (session 3) after needle or electrode removal.

Figure 2

Subjective sensations during three needle acupuncture (TNA), single needle acupuncture (SNA) with or without manual stimulation (MS) and transcutaneous electrical nerve stimulation (TENS). The sensations experienced during mechanical or electrical stimulation were reported using a visual analogue scale rating from 0 to 100. Data are presented as mean±SD. *p<0.05: TENS versus TNA, SNA and SNA+MS groups (one-way analysis of variance (ANOVA) plus Bonferroni post hoc test).

Figure 3

Comparison of default mode network (DMN)-related activity during and post-treatment with acupuncture or transcutaneous electrical nerve stimulation (TENS). (A) Images demonstrating areas of increased DMN-related activity associated with the different treatment modalities. (B) Increased right insula activity observed as post-treatment effect in SNA+MS group. (C) Increased left insula activity observed as during treatment effect in TNA group. ‘During treatment’ and ‘post-treatment’ effects were derived from the subtraction of images from session 1 and 2, and 1 and 3, respectively. Data were analysed statistically by paired t-test. The threshold was set at p=0.001 (uncorrected) with a cluster extent threshold of 10 voxels. FOG, frontal-orbital gyrus; IPG, inferior parietal gyrus; MiOG, middle occipital gyrus; SMA, supplementary motor area.