The current study examines the effects of transcranial direct current stimulation (tDCS) on the early visual cortex (EVC). This research addresses a critical issue: understanding the neural mechanisms underlying tDCS effects, a significant challenge due to inconsistent results in previous studies. The authors used functional magnetic resonance imaging (fMRI) to measure blood-oxygenation-level-dependent (BOLD) responses to visual patterns while applying tDCS to the EVC. They focused on anodal-tDCS (a-tDCS) and cathodal-tDCS (c-tDCS). The study used a sham-controlled crossover design, where each subject underwent three types of daily sessions: a-tDCS, c-tDCS, and sham-tDCS. Results showed that a-tDCS elevated baseline cortical activity and enhanced spatial tuning by increasing surround suppression in the EVC. In contrast, c-tDCS had minimal effects. This study is crucial as it provides clues about the possible neural mechanisms for tDCS effects. The authors propose that a-tDCS might increase synaptic inhibition by upregulating the activity of certain GABAergic cells, enhancing surround suppression, and sharpening spatial tuning. Understanding these neural mechanisms is vital for resolving inconsistencies in tDCS research and could significantly impact therapeutic interventions using tDCS. In conclusion, this research advances our knowledge of tDCS effects on the visual cortex, offering valuable insights into the neural mechanisms involved.