Personal Experience: I am pretty sure this state of mind is similar to what is induced by ASMR. There is this idea of a braingasm, that I learned to self induce when I was around 10. Euphoria is the best way to describe it. I have noticed it to be similar to what people describe with ASMR, although I have not experimented with ASMR at all so I am not certain. I have also noticed it to be extremely similar to the transitory state into and out of sleep. I haven't tried using it for brainstorming, I guess I've got some more experimenting to do.