Non-invasive measurement of brain activity using functional MRI: toward the study of brain response to acupuncture stimulation

Current status of neuroimaging research on the effects of acupuncture: a bibliometric and visual analyses

OBJECTIVE

To conduct an inductive analysis of neuroimaging studies following the global popularity surrounding the effects of acupuncture.

METHODS

The relevant works of literature on acupuncture effects-related neuroimaging studies were retrieved from the web of science core collection database from the date of its establishment to 2022. Bibexcel software was used to extract information, such as article numbers, countries, journals, agencies, funding sources and keywords. The VOSviewer software's co-occurrence and clustering module was used for the co-occurrence and cluster analysis of collaborative networks and high frequency keywords, such as authors, institutions and countries.

RESULTS

Neuroimaging research on the effects of acupuncture began in the 1960 s and has since received the extensive attention of scholars. China, The United States and South Korea conduct more neuroimaging research on the effects of acupuncture than other countries. Academic journals such as Evidence-Based Complementary and Alternative Medicine, Journal of Alternative and Complementary Medicine, Neural Regeneration Research and Acupuncture in Medicine have published the highest number of acupuncture-related neuroimaging articles. Moreover, cluster analysis differentiates high-frequency keywords into six clusters. Furthermore, the use of the keyword 'density atlas' reveals that neuroimaging research on the effects of acupuncture surrounding pain and neurofunctional rehabilitation is currently the research focus.

CONCLUSIONS

This bibliometric study identifies six important research hot spots: Static brain functional connectivity analysis of acupuncture analgesic effects, key theories on the scientific problems of acupuncture, acupuncture analgesic effect of the placebo effect, the neuroimaging of acupoint ST-36, the value of acupuncture in regulating the autonomic nerves and acupuncture therapy as complementary medicine.

The History of Ear Acupuncture and Ear Cartography: Why Precise Mapping of Auricular Points Is Important

The current author had the opportunity to present a study on the history of ear acupuncture at the International Summit Forum on Clinical Application of Acupoints in August 2018 (from August 25 to August 27), in Beijing, China, and to introduce the latest ear chart by Frank R. Bahr, MD, there. This article is based on that presentation and includes more historical facts. Although the relationship between the ear and meridians was discussed previously in the famous book, The Internal Classic of the Yellow Emperor (Huang Di Neijing), the first auricular map was published in 1888 by Zhenjun Zhang in his book Essential Techniques for Massage (Lizheng Anmo Yaosu). This map was a drawing of the posterior aspect of the ear showing areas of the five Zang organs: Heart; Liver; Spleen; Kidney; and Lung. Paul Nogier, MD, discovered ear somatotopy, a representation of the whole person on the ear in the shape of a homunculus, or inverted fetus, on the ear. Dr. Paul Nogier's ear map was first published in 1957. A more-detailed presentation, the Loci Auriculomedicinae, elaborated by Drs. Paul Nogier and Bahr as well as René J. Bourdiol, MD, appeared in 1974. A new edition will soon appear in French. Auricular medicine is an excellent method, but only if the ear points are located precisely. Preconditions for this ability are excellent knowledge of the ear's anatomy, documented on a very detailed modern ear chart, such as the one recently created by Dr. Bahr, and constant practice of pulse palpation according to Dr. Paul Nogier with the vascular autonomous signal.

Ultrasonic Acupuncture and the Correlation Between Acupuncture Stimulation and the Activation of Associated Brain Cortices Using Functional Magnetic Resonance Imaging

Using medical imaging techniques, such as fMRI, the stimulation of certain acupuncture points can be shown to correlate with activity in corresponding regions of the brain. Identical activity is also seen if the acupoint is stimulated with a pulse of ultrasound rather than a needle. This article reviews the advantages offered by ultrasonic acupuncture and the impact on the practice of acupuncture.

Quantification of Electroacupuncture-Induced Neural Activity by Analysis of Functional Neural Imaging with Monocrystalline Iron Oxide Nanocolloid Enhancement

The purpose of this study was to investigate the neural activity of electroacupuncture (EA) quantitatively. The responses of Sprague–Dawley rats' brain to EA on acupoints — Hegu (LI 4) and Neiguan (PC 6) — were detected by monocrystalline iron oxide nanoparticle (MION)-enhanced functional magnetic resonance imaging (MION-fMRI), which is a 1.5 T horizontal spectrometer equipped with a circular polarized extremity coil. During EA at LI 4, neural activities were analyzed by analysis of functional neural images (AFNI). Neural activation was detected at the structures of hypothalamus, thalamus, hippocampus, and the cortex, while neural deactivation existed at the areas adjacent to the activated sites. EA on PC 6 activated the structures of thalamus and the cortex but deactivated the structures of hypothalamus and hippocampus. The brain responses to EA existed in different areas of activation and deactivation despite stimulating the same acupoint. Additionally, distinct brain neuroimages were produced through stimulating different acupoints. This study suggests that fMRI with AFNI is a good approach to quantifying brain activities. This innovative method brings new perspective into the mechanisms of acupuncture.

Methodological problems in FMRI studies on acupuncture: a critical review with special emphasis on visual and auditory cortex activations

Functional magnetic resonance imaging (fMRI) has been used for more than a decade to investigate possible supraspinal mechanisms of acupuncture stimulation. More than 60 studies and several review articles have been published on the topic. However, till now some acupuncture-fMRI studies have not adopted all methodological standards applied to most other fMRI studies. In this critical review, we comment on some of the problems including the choice of baseline, interpretation of deactivations, attention control and implications of different group statistics. We illustrate the possible impact of these problems by focussing on some early findings, namely activations of visual and auditory cortical areas, when acupoints were stimulated that are believed to have a therapeutic effect on vision or hearing in traditional Chinese medicine. While we are far from questioning the validity of using fMRI for the study of acupuncture effects, we think that activations reported by some of these studies were probably not a direct result of acupuncture stimulation but rather attributable to one or more of the methodological problems covered here. Finally, we try to offer solutions for these problems where possible.

Consecutive acupuncture stimulations lead to significantly decreased neural responses

OBJECTIVE

Functional magnetic resonance imaging (fMRI), in combination with block design paradigms with consecutive acupuncture stimulations, has often been used to investigate the neural responses to acupuncture. In this study, we investigated whether previous acupuncture stimulations can affect brain activations of later acupuncture stimulations.

DESIGN

All subjects were measured twice in the same scanning session and a block design was used.

SETTING

The study was conducted at Kyung Hee University, Seoul, Republic of Korea.

SUBJECTS

Fifteen (15) healthy right-handed male volunteers participated in the study.

INTERVENTION

The subjects received two acupuncture stimulations on BL62 (Shenmai) on the right foot with a time interval of 5 minutes. In addition, sham stimulations were tested with the same paradigm.

OUTCOME MEASURES

One-sample t tests were conducted in order to map the brain activations induced by the acupuncture and sham stimulations. Moreover, paired-sample t tests were conducted to investigate the signal changes between the first and second acupuncture stimulation.

RESULTS

During the first acupuncture stimulation, in the left hemisphere, significant foci of activation were found in the hypothalamus, thalamus, claustrum, cerebellum, inferior frontal gyrus, and the superior temporal gyrus. In the right hemisphere, a significant focus of activation was found in the middle frontal gyrus. In addition, in both hemispheres, a significant focus of activation was found in the inferior parietal lobule. Interestingly, however, during the second acupuncture stimulation, the only areas that were also significantly activated were the cerebellum in the left hemisphere and the inferior parietal lobule in the right hemisphere.

CONCLUSIONS

We found that consecutive acupuncture stimulations on BL62 affected the neural responses in a significant way, resulting in decreased activations during the second acupuncture stimulation. This is an important finding, suggesting that in future fMRI studies on acupuncture, researchers should take this methodological issue more seriously.

Global trends and performances of acupuncture research

This study was designed to evaluate the global scientific output of acupuncture research in the Science Citation Index-Expanded and to assess the tendencies and research performances of leading countries/territories and institutes. Articles referring to acupuncture were assessed by distribution of document types, languages, journals, subject categories, source countries, and source institutes. Results showed that 15 languages were represented in articles from 65 countries/territories. Journal of Alternative and Complementary Medicine published the most articles, followed by American Journal of Chinese Medicine and Acupuncture & Electro-Therapeutics Research which were listed in category of integrative & complementary medicine. In the study period of 1991-2009, USA was the top producing country, followed by China (mainland) with a sharply growth trend. In 2009, publication of China (mainland) ranked top one in the world. In addition, an acupuncture research trend was found in two phases in terms of the increase of number of SCI-expanded journals' articles. Among the acupuncture research, pain control has been the most prevalent direction of study, and brain imaging is attracting the most recent attention.

The short-term effects of acupuncture on myofascial pain patients after clenching

AIM

Short-term pain reduction from acupuncture in chronic myofascial pain subjects was evaluated using an 11-point (0 to 10) numeric rating scale, visual analog scale (VAS), and pain rating of mechanical pressure on the masseter muscle.

METHODS

A single-blind, randomized, controlled, clinical trial with an independent observer was performed. Fifteen chronic myofascial pain subjects over the age of 18 were randomly assigned into groups: nine subjects received real acupuncture; six subjects received sham acupuncture. Each subject clenched his/her teeth for 2 minutes. Acupuncture or sham acupuncture was administered at the Hegu Large Intestine 4 acupoint. Sham acupuncture was conducted by lightly pricking the skin with a shortened, blunted acupuncture needle through a foam pad, without penetrating the skin. The foam pad visually conceals the needle's point of the entry, so that the subject cannot discern which technique is being used. The subjects rated their general pain on a numeric rating scale. A mechanical pain stimulus was applied with an algometer and the subject rated his/her pain on a VAS. Statistical analysis was performed using the repeated measures anova, paired t-tests, and Fisher's exact test as appropriate.

RESULTS

There was a statistically significant difference in pain tolerance with acupuncture (P = 0.027). There was statistically significant reduction in face pain (P = 0.003), neck pain (P = 0.011), and headache (P = 0.015) with perception of real acupuncture.

CONCLUSION

Pain tolerance in the masticatory muscles increased significantly more with acupuncture than sham acupuncture.

New findings of the correlation between acupoints and corresponding brain cortices using functional MRI

A preliminary study of the correlation between acupuncture points (acupoints) for the treatment of eye disorders suggested by ancient Oriental literature and the corresponding brain localization for vision described by Western medicine was performed by using functional MRI (fMRI). The vision-related acupoint (VA1) is located in the lateral aspect of the foot, and when acupuncture stimulation is performed there, activation of occipital lobes is seen by fMRI. Stimulation of the eye by directly using light results in similar activation in the occipital lobes by fMRI. The experiment was conducted by using conventional checkerboard 8-Hz light-flash stimulation of the eye and observation of the time-course data. This was followed by stimulation of the VA1 by using the same time-course paradigm as visual light stimulation. Results obtained with 12 volunteers yielded very clean data and very close correlations between visual and acupuncture stimulation. We have also stimulated nonacupoints 2 to 5 cm away from the vision-related acupoints on the foot as a control, and activation in the occipital lobes was not observed. The results obtained demonstrate the correlation between activation of specific areas of brain cortices and corresponding acupoint stimulation predicted by ancient acupuncture literature.