4. Discussion
In this study, we explored the impact of electric fields (EFs) on brain function, assessed through fMRI, across four analytical levels: voxel, ROI, cluster, and network. Voxel and ROI-level analyses showed no significant correlation between EFs and BOLD signal changes after multiple comparisons correction. Cluster-level analysis identified five active clusters in the left hemisphere with a time-by-group interaction effect in response to tDCS, but these did not correlate with EFs. Network-level analysis, however, revealed significant correlation between the frontal stimulation site and frontoparietal networks, specific to the active stimulation group. Despite these neural changes, no significant differences in self-reported craving scores were observed between the active and sham groups. Finally, we found a significant relationship between baseline frontoparietal connectivity and craving score changes post-stimulation, but this did not correlate with EF-induced network changes, suggesting that EF effects on neural activity may not directly influence subjective craving levels. Taken together, our findings highlight the complexity of EF effects on neural and behavioral outcomes, underscoring the need for multi-level analyses to fully understand the impact of electrical stimulation interventions.