But as radio stations transmit and receive sub-visible spectrum electromagnetic radiation, the brain transmits and receives quantum probability waves (or something like that).
Follow me on this ... the brain, being more complex and fundamentaly significant in the scheme of reality than a radio station, has five curious antennae: we call 'em "nose", "eyes", "tounge", "ears", "epidermal nerves-(?)". These antennae transmit and receive quantum inforamtion carried by molecules, electricity (electrons,) and photons (what amounts to basically "the outside world"). We interact with the outside world as the brain (a quantum computer?) computes and processes at about 10^12+ calculations per second, all the input data. It then reacts by secreting chemicals and creates a reality: we call this consciousness.
So somehow or another, psychedelics allow the brain to "tune" into another "radio station". The experience is as real as any other, just not as involved with "outside world" as it is with the "inside world". But perhaps "inside world" is a misnomer; it's just as outside the brain as the computer I'm looking at can be considered. (Or is the computer I'm looking at just a bunch of collaboration between the optical nerve and the central processesing unit, all taking place "inside"?)
Either way, say there is another world out there. Not so much a parallel universe that sci-fi writers describe, or spiritual plane that shamans describe, but rather this world is right here with us right now (under our nose so to speak). We just can't see it.
All the radio station transmissions occupy the same airwaves simultaneously, correct? All you do is adjust the tuner. Just as a radio tuner tuned to 98.5 won't pick up dialogue from "wild 102", we can't pick up experiences from the other facets of the universe. You've got to change the channel.
The brain does this naturaly when you die. It doesn't secrete testosterone or dopamine; it secretes the most powerful psychedelic thus known to science. Indeed, the universe uses atmoic dust and moleculer bonds to create even the afterlife experience. Consciousness on many levels (and spiritual planes) is all encoded in hierarchies of matter (protons and neutrons on up to axions - yanniru ; ) and anti-tachyons (I made that up ;) ). It's all about the signals we receive and from where they're transmitted. Psychedelics = different station.
P.S. One of the things I find exceedingly curious is: why did the subjects (in the book) always describe an overwhelming feeling of belonging and of waking up to whatever it was they "woke up" to?
One guy said he heard a bunch of what seemed like electronic elves whispering franticly, "Here's here, he's here! He's back, I can't believe it! He made it! I'm so excited! I didn't take him that long after all..." The elves (as can best be described) welcomed him and tried to comfort him. Then they all made way for a blue floating orb and fell to their knees in worship. The orb explained to him how he was not supposed to be back yet. This took place just as his body started to metabolize the DMT (so said the scientist), as twenty mintues into the trip the subject was saying such gibberish as "God, I have so many things I wanted to ask you. Can I stay a while longer?". As the effects of the drug wore off, God took his elves and went back into some sort of wormhole. "We'll see you when you get back. It won't be long." Crazy, crazy, crazy...