Objective： To investigate whether the neural representations underlying alternating two acupoint combinations （ACs） are the same or not. Methods： In this functional magnetic resonance imaging study, two sets of analgesia ACs were utilized, including Waiguan （TE5） and Qiuxu （GB40） for Group A, and Neiguan （PC6） and Taichong （LR3） for Group B, which are the most commonly adopted in clinical treatment. Each group had 20 healthy subjects. An experinlental design was proposed, which consisted of a pre-needling resting phase, a needling phase and a post-needling resting phase. This paradigm optimally mimics the clinical protocol as well as focuses on both the stimulation and the resting periods. The results were subjected to general linear model analysis, conjunction analysis and the functional connectivity analysis. Results： The rostral anterior cingulated cortex was engaged in the initiative period of the acupuncture effect in both groups, and it was chosen as the seed region for the functional connectivity analysis for the following resting period. The results showed that several shared brain regions were involved in both groups, in particular the insula, amygdala and hypothalamus. Moreover, significant differences were located at the posterior cingulated cortex as revealed by a two sample t-test （P〈0.05, corrected）. Other regions showed no significant differences. This finding was further supported by the spatial correlation analysis that the two groups were significantly correlated （r=0.51, P〈0.01）. Conclusion： This preliminary research helps us understand the neurophysiological mechanisms of acupuncture when following clinical guidelines on ACs, as well as provides an important opportunity to develop better treatment strategies for reducing, or even preventing pain.
