Discussion
In this study, based on data from our previous trial (As expected, our results showed that inter-individual anatomical differences were associated with NIBS effects. The findings revealed that subjects with thinner DLPFC regions showed relatively faster reaction times than individuals with greater cortical thickness after tDCS and iTBS interventions compared to placebo, whereas the PCC, which was the deepest area investigated, presented a positive association between its left portion and reaction time performance after iTBS.Interestingly, in our first study (The inverse association between cortical thickness and working memory performance was already reported in previous studies using interventions other than NIBS. For instance, a recent trial investigated the changes in cortical thickness of healthy volunteers after two months of working memory training and found that some structural changes were negatively associated with cognitive performance, demonstrating that larger thickness reductions led to larger training-related behavioral improvements (Our results also showed that iTBS performance, but not tDCS, presented an association with the PCC, the deepest cortical thickness region investigated. As tDCS delivers a weaker electric current compared to iTBS and does not produce action potentials per se, we hypothesized that tDCS effects may have not been robust enough to modulate inner cortical structures compared to placebo, whereas iTBS might have been able to reach the PCC after only one active session. Based on these findings, we can assume that the PCC plays an important role in working memory processes and that iTBS mechanisms of action on the left DLPFC are associated with network-level efforts.Moreover, we were not able to find an association between individual cortical thickness of the mPFC and working memory performance. Although preliminary studies suggest that bilateral tDCS montages over the DLPFC can induce stronger electric fields in the medial part of the PFC (Although our results provide the first evidence of the association between individual cortical thickness differences and working memory performance following an NIBS intervention, previous studies already suggested that brain anatomy might have an influence on NIBS response. For instance, a recent study showed that individual gray matter volume of the left DLPFC might be associated with tDCS antidepressant effects (