Fig. 3: MRI results of TI stimulation.
a Schematic of TI stimulation. Two electrode pairs with each sharing the same current and frequency but with opposite poles. Frequencies f1 and f2 were assigned to currents I1 and I2, with a difference Δf = f2–f1. b Electrode placements for the left EC stimulation protocol. 1A, 1B and 2A, 2B respectively represented the two electrode pairs. The placement followed the international 10–10 system, with positions at C5, CP5, FT10, and F8. c Electrode placement for the right EC stimulation protocol with positions at F9, FT9, CP4, and C6. d–f Envelope simulation results for left EC stimulation protocol with 32 participants recruited. d Axial view with two cortex ROIs under electrodes (C5, CP5) in the left hemisphere. e Average absolute envelope intensities comparisons between the left EC and cortex ROI1 (t(30) = 2.193, p = 0.036), cortex ROI2 (t(30) = 2.879, p =  0.007), and the whole brain average (t(30) = 3.454, p = 0.002). All statistical comparision were done through two-sided paired t-tests with no adjustments. Data are presented as mean values +/− SD. f Group-averaged voxel-wise values of the absolute envelope values. g–i Results under right EC stimulation protocol with all settings similar to (d–f). h Envelope intensities comparisons between the right EC and cortex ROI1 (t(30) = 8.039, p < 0.001), cortex ROI2 (t(30) = 9.072, p <  0.001), and the whole brain average (t(30) = 5.425, p < 0.001). j–k Resting-state fMRI results under left stimulation protocol. The sham group with n = 9 participants, left group n = 11, and right group, n = 12. j FC comparisons between the left stimulation group and sham group. The alternations from before to during stimulation of FCs between left EC and other ROIs, together with the alternations of FCs between right EC and other ROIs. k Classification accuracy of FC differences between left EC and sham condition, calculated by subtracting data before TI stimulation from during stimulation. Box plots indicate median (middle line), 25th, 75th percentile (box) and min to max (whiskers) as well as all data points. l–m Resting-state fMRI results under the right EC stimulation protocols, with all settings similar to (j–k). Note: *≤ 0.05, **≤ 0.01, and ***≤ 0.001.
