Seems pretty cool. I've heard great things about deep brain stimulation and how it is the SOTA for many neurological disorders. It has actual experiments in humans instead of rodents. And the humans are healthy adults too! So it ticks all boxes for me as an amature enthusiast for a potential 'enhance my cognition' method. I wonder, where the catch?
Some of the authors' earlier work in rodents painted a really exciting picture of directly driving neuronal activity from outside the brain. However, that data came from an animal with a small, smooth brain and the stimulation was actually delivered onto the skull (rather than the skin). Thus, they could make electric fields of ~400 V/m in their animals, whereas fields of ~1 V/m are about all you can expect from non-invasive (i.e., scalp) electrical stimulation of an awake, healthy human (at least one that you want to keep healthy!).
We recently did some experiments with macaques receiving tTIS through the scalp, which are much more similar to humans. It could shift the timing of individual neurons' ongoing activity, but not directly force them to spike. It generally wasn't strong enough to impose new rhythms on the brain, just muck up existing ones. This isn't nothing--"mistimed" neural activity is involved in lots of diseases and ways to fix that might be very valuable--but it's very different fro the dominant story.
Here are our results, if you want to read more: https://www.biorxiv.org/content/10.1101/2023.09.25.559340v1