TMS may be used to increase activity in the underactive prefrontal cortex in depression by stimulating the left dorsolateral prefrontal cortex.

“And then a third outcome, which is important, that it's inert, it doesn't do either. So you can have stimulation approaches that do one, you know, increase activity, decrease activity, or are inert. And so what they found was, oh, we can excite certain brain regions. Then my mentor, Mark George said, had this kind of aha moment where he said, "Wow, there's underactivity in prefrontal cortex in depression, and we can increase activity using this thing that we know we can increase activity in motor cortex. We just need to put it in the left dorsolateral prefrontal cortex."”