Tms especially has been looked into heavily by researchers as well as the military over the last 20 years. The results have been remarkable both as treatment but also as a concentration/ skill and learning booster with effects being maintained long after treatment. I believe NPR did a segment on this recently as well.

It's ironic to think that given everything we think we know about how the brain functions , such a gross and simple procedure as wiring a battery to your head or inducing a magnetic field would have such strong and even beneficial effects.

https://scholar.google.com/scholar?q=transcranial+magnetic+s...