The story behind subgenual cingulate and mood had long been known . DBS targets it as well for depression

https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC2729429/

Only difference here is that normal TMS targets a part of the brain that is not the same for every one. subgenual cingulate location for every one is a bit different . With help of fmri they can know exactly where it is instead of just using a default location