With exercise there are at least people who do know what they're doing you can ask. In this case there isn't anybody who really knows what they're doing, at least not to the point that they can get any benefits out of it.
I think the real "only" way to improve your brain is to improve the sophistication of the "software" that makes up the wiring of your brain. I'm pretty sure from a logical standpoint that electricity alone doesn't do this.
