Brain functional connectivity network studies of acupuncture:a systematic review on resting-state fMRI

Background: Functional magnetic resonance imaging(f MRI) is a novel method for studying the changes of brain networks due to acupuncture treatment. In recent years, more and more studies have focused on the brain functional connectivity network of acupuncture stimulation.Objective: To offer an overview of the different influences of acupuncture on the brain functional connectivity network from studies using resting-state f MRI.Search strategy: The authors performed a systematic search according to PRISMA guidelines. The database Pub Med was searched from January 1, 2006 to December 31, 2016 with restriction to human studies in English language.Inclusion criteria: Electronic searches were conducted in Pub Med using the keywords ‘‘acupuncture" and‘‘neuroimaging" or ‘‘resting-state f MRI" or ‘‘functional connectivity".Data extraction and analysis: Selection of included articles, data extraction and methodological quality assessments were respectively conducted by two review authors.Results: Forty-four resting-state f MRI studies were included in this systematic review according to inclusion criteria. Thirteen studies applied manual acupuncture vs. sham, four studies applied electroacupuncture vs. sham, two studies also compared transcutaneous electrical acupoint stimulation vs.sham, and nine applied sham acupoint as control. Nineteen studies with a total number of 574 healthy subjects selected to perform f MRI only considered healthy adult volunteers. The brain functional connectivity of the patients had varying degrees of change. Compared with sham acupuncture, verum acupuncture could increase default mode network and sensorimotor network connectivity with pain-, affectiveand memory-related brain areas. It has significantly greater connectivity of genuine acupuncture between the periaqueductal gray, anterior cingulate cortex, left posterior cingulate cortex, right anterior insula, limbic/paralimbic and precuneus compared with sham acupuncture. Some research had also shown that acupuncture could adjust the limbic-paralimbic-neocortical network, brainstem, cerebellum,subcortical and hippocampus brain areas.Conclusion: It can be presumed that the functional connectivity network is closely related to the mechanism of acupuncture, and central integration plays a critical role in the acupuncture mechanism.