Neural substrates, experimental evidences and functional hypothesis of acupuncture mechanisms
Objectives – Although acupuncture therapy has demonstrated itself to be effective in several clinical areas, the underlying mechanisms of acupuncture in general and the analgesic effect in particular are, however, still not clearly delineated. We, therefore, have studied acupuncture analgesic effect through fMRI and proposed a hypothesis, based on the obtained result, which will enlighten the central role of the brain in acupuncture therapy.
Methods – The proposed model, termed as a broad sense hypothalamus-pituitary-adrenal (BS-HPA) axis,
was based on our observed neuroimaging results. The model incorporates the stress-induced HPA axis model together with neuro- immune interaction including the cholinergic anti-inflammatory model.
Results – The obtained results coupled with accumulating evidence suggest that the central nervous system is essential for the processing of these effects via its modulation of the autonomic nervous system, neuroimmune system and hormonal regulation.
Conclusions –Based on our fMRI study, it appears that understanding the effects of acupuncture within a neuroscience-based framework is vital. Further, we have proposed the broad sense-HPA axis hypothesis which incorporates the experimental results.
Acupuncture, the limbic system, and the anticorrelated networks of the brain
The study of the mechanism of acupuncture action was revolutionized by the use of functional magnetic resonance imaging (fMRI). Over the past decade, our fMRI studies of healthy subjects have contributed substantially to elucidating the central effect of acupuncture on the human brain. These studies have shown that acupuncture stimulation, when associated with sensations comprising deqi, evokes deactivation of a limbic-paralimbic-neocortical network, which encompasses the limbic system, as well as activation of somatosensory brain regions. These networks closely match the default mode network and the anti-correlated task-positive network described in the literature. We have also shown that the effect of acupuncture on the brain is integrated at multiple levels, down to the brainstem and cerebellum. Our studies support the hypothesis that the effect of acupuncture on the brain goes beyond the effect of attention on the default mode network or the somatosensory stimulation of acupuncture needling. The amygdala and hypothalamus, in particular, show decreased activation during acupuncture stimulation that is not commonly associated with default mode network activity. At the same time, our research shows that acupuncture stimulation needs to be done carefully, limiting stimulation when the resulting sensations are very strong or when sharp pain is elicited. When acupuncture induced sharp pain, our studies show that the deactivation was attenuated or reversed in direction.
Our results suggest that acupuncture mobilizes the functionally anti-correlated networks of the brain to mediate its actions, and that the effect is dependent on the psychophysical response. In this work we also discuss multiple avenues of future research, including the role of neurotransmitters, the effect of different acupuncture techniques, and the potential clinical application of our research findings to disease states including chronic pain, major depression, schizophrenia, autism, and Alzheimer's disease.
The human brain responseto acupuncture on same-meridian acupoints: evidence from an fMRIstudy.
Objectives: Stimulation of acupuncture points (acupoints) located on meridians has been proven to activate specific areas of the human brain, as evidenced by functional imaging studies. To date, the specificity of acu- points located on different meridians has been investigated with functional magnetic resonance image (fMRI). The present fMRI study explored the effects of stimulating 4 acupoints on 2 different meridians for the pur- pose of researching the characteristic response of acupoints on the same meridian.
Materials and methods: The acupoints studied were LR3 (Taichong) and LR6 (Zhongdu), which belong to the Liver meridian of Foot-Jueyin; ST36 (Zusanli) and ST43 (Xiangu), which belong to the Stomach meridian of Foot-Yangming; and 2 nearby sham acupoints. Fifty-three (53) healthy right-handed subjects were divided randomly into 6 groups. Each group only received acupuncture at one acupoint. All the acupoints in this study were stimulated only on the right side of the subject’s body. Through analysis of fMRI data from all subjects, we ob- tained the activation patterns in the central nervous system (CNS) evoked by acupuncture.
Results: In contrast to the CNS activation by sham acupoint, the results showed that all 4 real acupoints under consideration had the common effect of activating 2 specific areas of the brain: the bilateral primary so- matosensory area and the ipsilateral cerebellum. Acupuncture stimulation of both acupoints LR3 and LR6 evoked activation at the ipsilateral superior parietal lobe (BA7). Acupuncture stimulation of both acupoints ST36 and ST43 evoked activation at the ipsilateral middle frontal gyrus (BA10).
Conclusions: These results suggest that different acupoints on the same meridian may activate certain similar areas of the brain. In addition, acupoints that are commonly used in clinical practice might modulate a greater extent of cortical areas than uncommonly used acupoints.