The authors have declared that no competing interests exist.
Conceived and designed the experiments: YBY LJB RWD. Performed the experiments: YBY CGZ TX. Analyzed the data: YBY LJB CGZ. Contributed reagents/materials/analysis tools: HW ZYL WJW. Wrote the paper: JT.
As an ancient Chinese healing modality which has gained increasing popularity in modern society, acupuncture involves stimulation with fine needles inserted into acupoints. Both traditional literature and clinical data indicated that modulation effects largely depend on specific designated acupoints. However, scientific representations of acupoint specificity remain controversial. In the present study, considering the new findings on the sustained effects of acupuncture and its time-varied temporal characteristics, we employed an electrophysiological imaging modality namely magnetoencephalography with a temporal resolution on the order of milliseconds. Taken into account the differential band-limited signal modulations induced by acupuncture, we sought to explore whether or not stimulation at Stomach Meridian 36 (ST36) and a nearby non-meridian point (NAP) would evoke divergent functional connectivity alterations within delta, theta, alpha, beta and gamma bands. Whole-head scanning was performed on 28 healthy participants during an eyes-closed no-task condition both preceding and following acupuncture. Data analysis involved calculation of band-limited power (BLP) followed by pair-wise BLP correlations. Further averaging was conducted to obtain local and remote connectivity. Statistical analyses revealed the increased connection degree of the left temporal cortex within delta (0.5–4 Hz), beta (13–30 Hz) and gamma (30–48 Hz) bands following verum acupuncture. Moreover, we not only validated the closer linkage of the left temporal cortex with the prefrontal and frontal cortices, but further pinpointed that such patterns were more extensively distributed in the ST36 group in the delta and beta bands compared to the restriction only to the delta band for NAP. Psychophysical results for significant pain threshold elevation further confirmed the analgesic effect of acupuncture at ST36. In conclusion, our findings may provide a new perspective to lend support for the specificity of neural expression underlying acupuncture.
Acupuncture is one of the most important therapeutic modalities in Traditional Chinese Medicine (TCM), which treats patients by utilizing thin needles inserted into specific anatomical points named acupoints and then twirled manually
One of the most highly attention-grabbing controversies focuses on acupoint specificity, which lies in the crucial position of traditional acupuncture theory. Based upon TCM, twirling needles at acupoints can correct imbalances in the flow of
During the last few decades, advances in non-invasive imaging techniques have significantly boosted neuroscience research, among which fMRI has been the dominant tool for exploring brain activity
The current study was developed to explore whether or not divergent alteration of functional connectivity exists following verum acupuncture (Stomach Meridian 36, ST36) relative to sham acupuncture (non-meridian point, NAP). Since previous electrophysiological investigations have demonstrated differential band-limited signal changes brought about by acupuncture
In order to reduce the inter-subject difference, 28 Chinese right-handed healthy college students (14 males, 14 females, aged 24.5±1.8 years) selected from a homogeneous group were enrolled in this study. They were all acupuncture naïve. None of them had a history of major medical illness, head trauma, neuropsychiatric disorders, nor did they use any prescription medications within the last month according to a questionnaire they filled out. All subjects gave written, informed consent after the experimental procedures had been fully explained. The research procedures were approved by the Tiantan Hospital Subcommittee on Human Studies and conducted in accordance with the Declaration of Helsinki.
Twenty-eight participants were evenly divided into two groups, being matched by age and gender. Every subject received only once acupuncture stimulation. They were instructed to sit comfortably in a dark and magnetically shielded room with their eyes closed and asked to remain relaxed without engaging in mental tasks.
The experiment consisted of two functional runs. The resting-state run lasted 6 min. Acupuncture in both groups employed the single-block design paradigm, incorporating a 2 min needle manipulation, preceded by a 1 min rest epoch and followed by another 6 min resting scan (needle was kept in place without manipulation). See
Panel A indicates that acupuncture stimulation was performed at acupoint ST36 on the right leg (Zusanli, arrow pointing to the red dot). Panel B indicates that needling was performed at an adjacent nonacupoint on the right leg (NAP, arrow pointing to the green dot). The red line refers to needle administration, and the blue line represents no acupuncture manipulation but with needles inserted, while the green long line indicates a 6 min resting state or post-stimulus resting state. In this study, the two 6 min resting epochs were employed, while the rest were used for further analysis.
According to TCM, the sensation induced by twirling needles at the acupoints is asserted as “
The MEG data were recorded while subjects were comfortably seated inside a magnetically shielded room using a 151-channel whole-head MEG system (CTF Systems Inc., Port Coquitlam, BC, Canada). Average distance between sensors in this system was 3.1 cm. The head position was monitored during the measurement using head position indicator coils. MEG data were recorded at the sample rate of 600 Hz. During the recording, participants were instructed to close their eyes to reduce artifact signals due to eye movements, but remained awake as much as possible. Subjects wore earplugs throughout the experiment to attenuate any sounds heard from outside of the MEG room. The investigator and MEG technician checked the signal on-line and observed the participants using a video monitor. At the beginning and end of each recording, the head position relative to the coordinate system of the helmet was recorded by leading small alternating currents through three head position coils attached to the left and right pre-auricular points and the nasion on the subject's head. If any subject's head moved more than 5 mm during the experiment, data from that subject would be discarded from further analysis. It turns out for all of the participants that the difference between the sensor locations evaluated during the whole experiment was not obvious, confirming a relatively stable head position.
A third-order gradient noise reduction (computed with CTF software) was applied on line to the MEG signals. MEG data were then digitally filtered off-line with a band-pass of 0.5–48 Hz and further down sampled to 300 Hz. Subsequently, data were band-passed into the following frequency ranges: delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz) and gamma bands (30–48 Hz)
The MEG channels were grouped into 10 regions of interest (ROIs) roughly corresponding to the major cortical areas (frontal, temporal, central, parietal and occipital for each hemisphere). Two of the original 151 channels were not available due to technical problems. Besides, the 9 midline channels were left out of clustering, leaving a total of 140 channels divided over 10 ROIs for further analysis. The band-limited power (BLP) of each channel, defined as the envelope of the band-limited signal, was calculated by first applying the Hilbert transform to the band-limited signal and then taking the absolute value of the resultant complex helical sequence
For each frequency band of interest, the pair-wise temporal correlations between the BLP signals were computed using Pearson's correlation. The end result is a
The prevalence of subjective “
A. The percentage of subjects that reported the given sensations. The frequency of aching was found to be greater following acupuncture at ST36. B. The intensity of sensations measured by average score (with standard error bars) on a scale from 0 denoting no sensation to 10 denoting an unbearable sensation. Sore, soreness; Numb, numbness; Full, fullness; Cool, coolness; Warm, warmth; SP, sharp pain; DP, dull pain; Heav, heaviness; Tinl, tingling; Ach, aching; Press, pressure. C. The pain threshold evaluated by average score (with standard error bars) before and after acupuncture at ST36 and NAP. Significant elevation of the pain threshold was observed following acupuncture at ST36.
For each condition preceding or following acupuncture, the temporal correlations of band-limited power (BLP) signals were first computed for every pair of MEG channels in each frequency band and then grouped into local and long-distance couplings. The grand averaged local and long-distance couplings for the two conditions in each group were taken in for further statistical analysis.
Among the 5 frequency bands either for verum or sham acupuncture, our results demonstrated dominant enhanced connectivity within the delta band (0.5–4 Hz). As illustrated in
A. ST36 group. B. NAP group. Lines correspond to significant changes for the average Band-Limited Power (BLP) correlation induced by acupuncture and squares to significant change in the local BLP correlation (red: local increase in the BLP correlation following acupuncture; thin line:
Delta | ||||||||
Group ST36 | Group NAP | |||||||
Areas | B_rest | P_rest | B_rest | P_rest | ||||
LC | 0.3902±0.0525 | 0.4215±0.0612 | 1.949 | 0.073 | 0.4247±0.0864 | 0.4579±0.0937 | 1.693 | 0.114 |
LF | 0.5480±0.1057 | 0.5908±0.0958 | 1.961 | 0.072 | 0.4953±0.1029 | 0.5077±0.1127 | 0.613 | 0.551 |
LO |
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0.4631±0.1203 | 0.4979±0.1018 | 1.424 | 0.178 |
LP | 0.5383±0.0670 | 0.5721±0.0692 | 2.063 | 0.060 | 0.5481±0.0926 | 0.5777±0.0996 | 2.130 | 0.053 |
LT |
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0.3999±0.0855 | 0.4204±0.1057 | 0.904 | 0.383 |
RC |
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0.4287±0.1261 | 0.4727±0.1038 | 1.947 | 0.073 |
RF |
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0.5248±0.1133 | 0.5546±0.1545 | 1.088 | 0.297 |
RO | 0.3940±0.0684 | 0.4176±0.0475 | 1.238 | 0.238 | 0.4862±0.1740 | 0.4738±0.4738 | −0.539 | 0.599 |
RP | 0.4592±0.0580 | 0.4670±0.0869 | 0.483 | 0.637 | 0.4986±0.1353 | 0.4962±0.1146 | −0.341 | 0.868 |
RT |
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0.4110±0.1107 | 0.4461±0.1150 | 1.689 | 0.115 |
LF_LP | 0.1789±0.0533 | 0.1767±0.0914 | −0.119 | 0.907 |
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LF_LT |
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0.2373±0.0733 | 0.2541±0.0757 | 0.804 | 0.436 |
LO_LP | 0.2020±0.0617 | 0.2363±0.0871 | 1.693 | 0.114 |
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LO_LT |
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0.1904±0.0914 | 0.2037±0.0457 | 0.562 | 0.583 |
RF_RP | 0.1428±0.0422 | 0.1755±0.0995 | 1.371 | 0.194 |
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RF_RT |
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RO_RP | 0.1730±0.0445 | 0.2027±0.0516 | 1.812 | 0.093 | 0.2458±0.1913 | 0.2522±0.1559 | 0.301 | 0.768 |
RO_RT |
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0.2049±0.0863 | 0.2161±0.0593 | 0.433 | 0.672 |
LC_RC | 0.1626±0.0428 | 0.1775±0.0616 | 0.903 | 0.383 |
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LF_RF |
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0.2740±0.0890 | 0.3067±0.1145 | 1.169 | 0.263 |
LO_RO | 0.1637±0.0508 | 0.1892±0.0763 | 1.149 | 0.271 | 0.2314±0.1829 | 0.2209±0.1128 | −0.436 | 0.670 |
LP_RP | 0.1516±0.0567 | 0.1525±0.0748 | 0.056 | 0.956 |
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LT_RT |
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0.2552±0.0961 | 0.2791±0.1143 | 1.083 | 0.298 |
Significant differences are indicated in bold (
Regarding the beta band (13–30 Hz), both groups displayed a prominently increased left parieto-occipital connection (
A. ST36 group. B. NAP group. Lines correspond to significant changes for the average Band-Limited Power (BLP) correlation induced by acupuncture and squares to significant change in the local BLP correlation (red: local increase in the BLP correlation following acupuncture; thin line:
Beta | ||||||||
Group ST36 | Group NAP | |||||||
Areas | B_rest | P_rest | B_rest | P_rest | ||||
LC | 0.4420±0.0750 | 0.4431±0.0748 | 0.074 | 0.942 | 0.4373±0.0690 | 0.4328±0.0872 | −0.540 | 0.598 |
LF | 0.4104±0.0991 | 0.4186±0.0860 | 1.381 | 0.190 | 0.3898±0.0786 | 0.3875±0.0811 | −0.275 | 0.788 |
LO | 0.4337±0.0490 | 0.4480±0.0548 | 1.658 | 0.121 |
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LP | 0.6715±0.0574 | 0.6823±0.0673 | 0.880 | 0.395 | 0.6398±0.0604 | 0.6414±0.0724 | 0.250 | 0.806 |
LT | 0.3608±0.0470 | 0.3586±0.0511 | −0.402 | 0.694 | 0.3554±0.0674 | 0.3560±0.0752 | 0.089 | 0.931 |
RC | 0.4231±0.0791 | 0.4164±0.0955 | −0.412 | 0.687 | 0.4118±0.0675 | 0.4043±0.0874 | −0.677 | 0.510 |
RF | 0.4822±0.0680 | 0.4793±0.0670 | −0.284 | 0.781 | 0.4545±0.0808 | 0.4492±0.0821 | −0.692 | 0.501 |
RO | 0.4175±0.0582 | 0.4299±0.0717 | 1.152 | 0.270 | 0.4333±0.0564 | 0.4456±0.0615 | 1.609 | 0.132 |
RP | 0.6959±0.0568 | 0.6987±0.0479 | 0.263 | 0.797 | 0.6779±0.0503 | 0.6788±0.0594 | 0.116 | 0.909 |
RT | 0.3662±0.0324 | 0.3645±0.0278 | −0.300 | 0.769 | 0.3600±0.0638 | 0.3511±0.0663 | −1.303 | 0.215 |
LF_LP | 0.0865±0.0389 | 0.1029±0.0505 | 1.879 | 0.083 | 0.0746±0.0371 | 0.0837±0.0452 | 1.791 | 0.097 |
LF_LT |
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0.1224±0.0461 | 0.1308±0.0411 | 1.803 | 0.095 |
LO_LP |
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LO_LT | 0.1598±0.0388 | 0.1688±0.0474 | 1.272 | 0.226 | 0.1706±0.0617 | 0.1808±0.0762 | 1.712 | 0.111 |
RF_RP | 0.0901±0.0338 | 0.1088±0.0474 | 1.834 | 0.090 | 0.0842±0.0447 | 0.0877±0.0473 | 0.585 | 0.568 |
RF_RT | 0.1999±0.0407 | 0.199±0.0424 | −0.001 | 0.999 | 0.1717±0.0663 | 0.1714±0.0616 | −0.047 | 0.963 |
RO_RP | 0.2176±0.0527 | 0.2373±0.0594 | 2.128 | 0.053 | 0.2061±0.0550 | 0.2182±0.0554 | 1.671 | 0.119 |
RO_RT | 0.1539±0.0464 | 0.1631±0.0453 | 1.084 | 0.298 | 0.1747±0.0519 | 0.1739±0.0577 | −0.089 | 0.930 |
LC_RC | 0.1361±0.0495 | 0.1449±0.0605 | 0.972 | 0.349 | 0.1174±0.0435 | 0.1234±0.0572 | 0.838 | 0.417 |
LF_RF | 0.1729±0.0455 | 0.1865±0.0561 | 1.791 | 0.097 | 0.1460±0.0582 | 0.1495±0.0572 | 0.597 | 0.561 |
LO_RO | 0.1838±0.0530 | 0.1921±0.0670 | 0.792 | 0.443 | 0.1982±0.0776 | 0.2124±0.0941 | 1.614 | 0.130 |
LP_RP | 0.2224±0.0562 | 0.2531±0.0755 | 1.693 | 0.114 | 0.2054±0.0504 | 0.2201±0.0492 | 1.640 | 0.125 |
LT_RT | 0.1915±0.0500 | 0.1837±0.0532 | −0.805 | 0.435 | 0.1904±0.0539 | 0.1881±0.0695 | −0.303 | 0.767 |
Significant differences are indicated in bold (
As for the gamma band (30–48 Hz), shared patterns of long and short distance interactivity alteration could be detected in both groups to certain extent (
A. ST36 group. B. NAP group. Lines correspond to significant changes for the average Band-Limited Power (BLP) correlation induced by acupuncture and squares to significant change in the local BLP correlation (red: local increase in the BLP correlation following acupuncture; thin line:
Gamma | ||||||||
Group ST36 | Group NAP | |||||||
Areas | B_rest | P_rest | B_rest | P_rest | ||||
LC | 0.2669±0.0856 | 0.2473±0.0798 | −1.553 | 0.144 | 0.2777±0.0880 | 0.2656±0.0902 | −1.584 | 0.137 |
LF | 0.2187±0.0825 | 0.2104±0.0660 | −0.884 | 0.393 | 0.2279±0.0934 | 0.2244±0.0892 | −0.605 | 0.555 |
LO |
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LP | 0.4430±0.0723 | 0.4307±0.0766 | −0.886 | 0.392 | 0.4486±0.0879 | 0.4432±0.0883 | −0.574 | 0.576 |
LT | 0.2145±0.0333 | 0.2232±0.0321 | 1.850 | 0.087 | 0.2131±0.0483 | 0.2133±0.0454 | 0.068 | 0.947 |
RC | 0.2281±0.0739 | 0.2112±0.0791 | −1.672 | 0.118 | 0.2396±0.0753 | 0.2275±0.0789 | −1.550 | 0.145 |
RF | 0.2568±0.0768 | 0.2578±0.0762 | 0.109 | 0.915 | 0.2640±0.0904 | 0.2632±0.0797 | −0.112 | 0.913 |
RO | 0.3197±0.0410 | 0.3144±0.0309 | −0.547 | 0.594 | 0.3127±0.0388 | 0.3151±0.0415 | 0.768 | 0.456 |
RP | 0.4719±0.0726 | 0.4598±0.0813 | −0.759 | 0.462 | 0.4822±0.0734 | 0.4696±0.0759 | −1.279 | 0.223 |
RT | 0.2260±0.0264 | 0.2309±0.0297 | 0.869 | 0.401 | 0.2212±0.0428 | 0.2213±0.0372 | 0.028 | 0.978 |
LF_LP | 0.0297±0.0187 | 0.0331±0.0188 | 1.319 | 0.210 | 0.0338±0.0405 | 0.0368±0.0368 | 0.964 | 0.353 |
LF_LT | 0.0489±0.0209 | 0.0546±0.0228 | 1.093 | 0.079 | 0.0528±0.0453 | 0.0558±0.0400 | 1.086 | 0.297 |
LO_LP |
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LO_LT |
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0.0768±0.0280 | 0.0816±0.0257 | 1.192 | 0.255 |
RF_RP | 0.0325±0.0160 | 0.0353±0.0190 | 0.806 | 0.435 | 0.0327±0.0210 | 0.0315±0.0153 | −0.423 | 0.679 |
RF_RT | 0.0630±0.0219 | 0.0710±0.0247 | 1.894 | 0.081 | 0.0634±0.0373 | 0.0660±0.0261 | 0.452 | 0.659 |
RO_RP | 0.1098±0.0214 | 0.1115±0.0212 | 0.449 | 0.661 | 0.1106±0.0280 | 0.1085±0.0296 | −1.169 | 0.263 |
RO_RT | 0.0734±0.0183 | 0.0780±0.0184 | 1.059 | 0.309 | 0.0692±0.0209 | 0.0714±0.0212 | 1.206 | 0.249 |
LC_RC | 0.0534±0.0289 | 0.0488±0.0320 | −1.261 | 0.229 | 0.0519±0.0317 | 0.0506±0.0341 | −0.327 | 0.749 |
LF_RF | 0.0639±0.0396 | 0.0679±0.0386 | 0.858 | 0.407 | 0.0689±0.0695 | 0.0689±0.0602 | −0.002 | 0.999 |
LO_RO | 0.1084±0.0352 | 0.1098±0.0330 | 0.143 | 0.889 | 0.0976±0.0381 | 0.1046±0.0405 | 1.865 | 0.085 |
LP_RP | 0.1192±0.0302 | 0.1210±0.0326 | 0.319 | 0.755 | 0.1176±0.0449 | 0.1176±0.0393 | 0.008 | 0.994 |
LT_RT | 0.0650±0.0245 | 0.0700±0.0269 | 1.189 | 0.256 | 0.0648±0.0374 | 0.0634±0.0346 | −0.333 | 0.744 |
Significant differences are indicated in bold (
Additionally, both theta (4–8 Hz) and alpha (8–13 Hz) bands missed significant interaction alterations of functional connectivity in the ST36 and NAP groups (
It is noteworthy that when using MEG technology, we should always take into account the question whether the correlation measured between signals at different sensors can be interpreted with physiological interactions between different brain areas. This is the well-known problem of volume conduction effects
Acupuncture-induced modulations on functional connectivity have already been illustrated in previous fMRI investigations
Although significant alterations for both the verum and sham groups were mainly confined to delta, beta and gamma bands, the functional connectivity within each presented distinct change patterns. One intriguing finding here is the increased degree of connectivity recorded by sensors overlying the left temporal cortex within the delta, theta and gamma bands. Compared to recent fMRI studies in which the temporal gyrus as well as the underlying amygdala and hippocampus were indicated as network hubs following verum acupuncture, with the advantage of MEG we observed that such modulation effects existed specifically within the above-mentioned three bands, among which delta was the most dominant
To the best of our knowledge, this MEG study is the first to demonstrate the global differences in functional connectivity alterations induced by acupuncture. However, due to the inverse problem currently not to be solved properly, this preliminary research did not involve the source reconstruction. Therefore, we are currently not able to exactly evaluate the anatomical correspondence to the temporal structures, which must be considered as a pitfall. As far as we know, there have been several MEG studies using this methodology which successfully illustrated differential functional connectivity patterns in pathological patients compared with normal control
We would like to thank Ying Jiang, Fengbing Wang and Hao Chen for valuable technical assistance in conducting this research.