I feel this all the time. No one seems to really know what it is. I've asked around. The only reference I've ever explicitly found to it is from interviews by Hindu Swamis.
In Vedic medicine, this brain tingling is known as "Bindu Chi". Kind of like localized brain chi. Your brain is radiating extra life energy or something.
I know this sounds weird, but that's all I could find. I've had to make my own theories and experiments on top of that.
Oddly, according to yogis there is a direct relationship between bindu chi and abundant semen. This may be the sublimated sex energy that Napoleon Hill spoke of in Think and Grow Rich. He said that when men get older and ejaculate less, that is when their super-genius manifests. Time and time again this is evidenced in famous biographies of the great men. ...could this be an *actual energy*, and not just a psychology concept or metaphor? An intriguing possibility.
I've found that piracetam and magnesium oxide increase the amount of brain chi.
There's also a strange relationship between bindu chi and sound. High pitched sounds especially, but low ones too.
Binaural beats and hemi-sync especially make my brain energy go up.
This is not just chakra energy either, or kundalini energy. It's something different. Or it's at a different stage. I know that when you do have an awakening, energy explodes all around your brain and entire CNS and PNS.
I note that Scheele says to say "mmm" in the Euphoria series. He says, "say 'mmmm' and feel it in your forehead", which is a yogic way to cultivate bindu chi--via chant. Perhaps he has an understanding of this?
I also surmise that this is the same energy that Neil Slade is trying to cultivate at www.neilslade.com when he says to click your amygdala forward and energzie your frontal lobes.
All very strange, I know.
Don't mind me if this seems insane or ridiculous. I know that it must.