Effects of Coils, Post-processing Methods, and Amplitude Frequency on Resting-state Brain Function After Electroacupuncture at Zusanli: A Preliminary Study

Abstract

Objective: Based on different post-processing methods and amplitude frequencies of fMRI, this study aimed to compare the ability of flexible and rigid coils for evaluating changes in spontaneous brain activity after electroacupuncture at Zusanli (ST36). Methods: A total of 28 healthy subjects who underwent the intervention of electroacupuncture at Zusanli using 12-channel flexible head coils and 16-channel rigid head coils were enrolled. BOLD-fMRI examination was conducted before and immediately after the acupuncture. The fractional amplitude of low-frequency fluctuations (fALFF), percent amplitude of fluctuation (PerAF), and wavelet amplitude of low-frequency fluctuations (Wavelet-ALFF) were used for post-processing. In addition to the conventional low-frequency band (0.01-0.1 Hz), and three sub-bands were also analyzed. A paired t-test was used to compare the changes in low-frequency amplitude before and after electroacupuncture intervention (GRF, voxel-wise p<0.01, cluster-wise p<0.05). Results: Changes in the low-frequency amplitude of the resting-state brain were found in all three analysis methods with flexible coils. In addition, the best result was obtained using PerAF method; an increase in the PerAF values of the brain regions in the limbic system, including bilateral cingulate gyri, insula, temporal lobe, the right hippocampus, and the left thalamus, were seen after electroacupuncture. Furthermore, electroacupuncture-induced changes in spontaneous brain activity are frequency-dependent, and more positive results were displayed in the conventional low-frequency and slow-5 bands. Conclusion: Flexible head coils combined with the PerAF method were more sensitive in revealing the changes in spontaneous activity of the resting-state brain after electroacupuncture at Zusanli, which were frequency-dependent.