Characterizing Acupuncture Stimuli Using Brain Imaging with fMRI - A Systematic Review and Meta-Analysis of the Literature

Abstract

BackgroundThe mechanisms of action underlying acupuncture, including acupuncture point specificity, are not well understood. In the previous decade, an increasing number of studies have applied fMRI to investigate brain response to acupuncture stimulation. Our aim was to provide a systematic overview of acupuncture fMRI research considering the following aspects: 1) differences between verum and sham acupuncture, 2) differences due to various methods of acupuncture manipulation, 3) differences between patients and healthy volunteers, 4) differences between different acupuncture points.Methodology/Principal FindingsWe systematically searched English, Chinese, Korean and Japanese databases for literature published from the earliest available up until September 2009, without any language restrictions. We included all studies using fMRI to investigate the effect of acupuncture on the human brain (at least one group that received needle-based acupuncture). 779 papers were identified, 149 met the inclusion criteria for the descriptive analysis, and 34 were eligible for the meta-analyses. From a descriptive perspective, multiple studies reported that acupuncture modulates activity within specific brain areas, including somatosensory cortices, limbic system, basal ganglia, brain stem, and cerebellum. Meta-analyses for verum acupuncture stimuli confirmed brain activity within many of the regions mentioned above. Differences between verum and sham acupuncture were noted in brain response in middle cingulate, while some heterogeneity was noted for other regions depending on how such meta-analyses were performed, such as sensorimotor cortices, limbic regions, and cerebellum.ConclusionsBrain response to acupuncture stimuli encompasses a broad network of regions consistent with not just somatosensory, but also affective and cognitive processing. While the results were heterogeneous, from a descriptive perspective most studies suggest that acupuncture can modulate the activity within specific brain areas, and the evidence based on meta-analyses confirmed some of these results. More high quality studies with more transparent methodology are needed to improve the consistency amongst different studies.

Psychophysical and neurophysiological responses to acupuncture stimulation to incorporated rubber hand

“…Neuroimaging studies investigating the acupuncture process have observed overlapping brain activations in the cortical sensorimotor and salient networks, as well as deactivations in the limbic-paralimbic neocortical network [7,13]. From a neurological point of view, the sensations induced by acupuncture are not only the product of the bottom-up modulation of simple needling at somatosensory receptors, but also of the reciprocal interaction of top-down modulation from the brain, such as the incorporation of focused attention and accentuated bodily awareness [21].…”

The Effect of Acupuncture on the Success of Inferior Alveolar Nerve Block for Teeth with Symptomatic Irreversible Pulpitis: A Triple-blind Randomized Clinical Trial

“…As described previously, acupuncture may cause the release of some mediators, which can inhibit substance P (a neurotransmitter that stimulates pain) and increase the release of cortisol, which helps the patients control their stress and anxiety (25). In addition, brain imaging studies have revealed that acupuncture varies the activation patterns in the pain processing areas of the brain (41). It is assumed that the needle stimulation causes the endogenous pain modulation's mechanisms to reduce pain perception; these mechanisms are diffuse noxious inhibitory controls, segmental inhibition, and descending pain control pathways (42,43).…”

Acupuncture as a Treatment Modality in Dermatology: A Systematic Review

“…19,20,22,24 Modern investigations into possible mechanisms of acupuncture have mixed results on the validity of meridians, but consistent across studies is involvement of the autonomic nervous system and hypothalamus-pituitary-adrenal (HPA) axis, recruited via peripheral sensory receptors. [37][38][39][40][41][42][43][44] Functional magnetic resonance imaging studies on humans found modulation of areas in the central nervous system involved in stress and nociception, such as the hypothalamus, nucleus accumbens, amygdala, hippocampus, and anterior cingulate gyrus. 39,[41][42][43][44] The downstream release of endogenous opioids is thought to contribute to subsequent analgesic and antipruritic effects.…”