Well I dunno.... I just close my eyes and can still see light.
The feeling I have sometimes is an high pressure on my forehead and in my head.
When the crown is also active I feel hundreds of needles at my fontanelle.
Each chakra has so it's own typical feeling, the heart and solar feel best.
You can get high off of brain chemicals like DMT and seratonin, the yogi's are probably the best tool to use for analysis because they've been using their brains as a spiritual tool for so long. The human body is a aggregate of forces, a finely tuned organic computer... we can get high off of emotions too, most people do without realising it.
The pineal, ajna and pituary work together to form the Well of Dreams chakra, the doorway to spiritual consciousness. There is too much info to post here, but it's a wonderous part of the human anatomy, the student would do well to study what it does and how it works.
Ha ha, I just thought of how the pineal might be the first "gateway" drug, ha ha, get it?
This link is for Geoff Stray's site DireGnosis 2012, excellent research that is not slanted one way or another- great tool for studies on the brain, recommend this site to anyone seeking knowledge without emotionalism.
fungus > pcilocybe cyanescens? I've seen liquid air around me with these, really kickass.
If you want to play the shaman, try salvia divinorum.