Modified electro-convulsive therapy (MECT) is one of the most potent treatments for major depressive disorder (MDD). However, it remains a second-line option due to significant side effects, such as transient memory loss. The relationship between therapeutic efficacy and cognitive impairment warrants further investigation to develop improved treatment regimens. In this review, we examine recent evidence from magnetic resonance imaging (MRI) studies aiming to identify structural and functional brain changes specifically associated with both the antidepressant effects and the amnesic outcomes of MECT. MECT induces widespread alterations across multiple brain systems. Increases in gray matter volume (GMV) have been observed in the prefrontal, temporal, and parietal cortices, as well as in subcortical regions such as the hippocampus (HP), amygdala, and striatum. Strengthening of myelination has also been reported along the dorsolateral prefrontal-limbic pathways. Functional changes include increased spontaneous neural activity in prefrontal areas, reorganization of intrinsic connectivity within the default mode network (DMN), and altered functional connectivity (FC) among the DMN, salience network (SN), and central executive network (CEN). Correlational studies have identified structural and functional alterations linked to antidepressant efficacy, including right hippocampal volume enlargement, prefrontal cortical thickening, reduced iron deposition in the striatum, decreased FC within certain DMN nodes, and enhanced effective connectivity from the dorsolateral prefrontal cortex (DLPFC) to the right angular gyrus. In contrast, the amnesic effects have been associated with increased volumes in the left hippocampus and bilateral dentate gyrus; enhanced FC in the left angular gyrus and left posterior cingulate cortex (PCC); increased FC between the right ventral anterior insula and DLPFC; and reduced FC in the left thalamus and bilateral precuneus. Changes in the hippocampus appear to correlate with both antidepressant efficacy and memory impairment. Clinical studies have found no significant correlation between the severity of memory impairment and the reduction in depressive symptoms, suggesting that the therapeutic and adverse effects may arise from distinct regional or subregional mechanisms. Supporting this hypothesis, recent findings show that increased right hippocampal volume is significantly associated with reduced depression scores, whereas increased volume in the left dentate gyrus correlates with declines in delayed recall performance. Additionally, enhanced connectivity between the anterior hippocampus and middle occipital gyrus (MOG) has been linked to mood improvement, while decreased FC between the mid-hippocampus and angular gyrus has been associated with impairments in memory integration. In conclusion, current evidence suggests that the antidepressant and memory-impairing effects of MECT may localize to distinct hippocampal subregions. These effects likely result from differential modulation of local neural activity and functional connectivity, leading to divergent behavioral outcomes. Given that both effects may originate in deep and spatially constrained structures such as the hippocampus, small-sample studies and conventional methodologies may fail to differentiate them effectively. Future research should employ large-scale, longitudinal designs utilizing high-field MRI and multimodal neuroimaging to characterize MECT-induced structure-function coupling in the hippocampus and its integration at the network level. Additionally, multiscale analyses spanning molecular, circuit, and network dimensions would be beneficial.