Peak experience: open to scientific scrutiny?

The following is from a recent exchange with a friend who is in the "enlightenment" business. I wrote:

There's no doubt in my mind there is a 'peak' experience that thousands or millions of people have had. You can't--I mean any responsible investigator--ignore the consistency of the subjective reports: non-duality, that is, a feeling of unity with the everything and everyone; conviction that their experience was not a hallucination, that something really happened that transcended all other experience or knowledge; ineffability, that is, they can't put it into words. The Tao that can be spoken of is not the Tao.

Now we can either say (1) science has no role to play here, that it's beyond our comprehension now and forever. Or (2) we can say, this is fascinating! How is it possible for people from all faiths and ages, to have this consistent experience?

(1) says that it's something metaphysical, like god, which gives rise to "enlightenment" phenomena (in which case it's beyond rational investigation, end of discussion). (2) says there might be something in the architecture of our brains which does it. This is the one I'm interested in looking at.

So for instance, one hypothesis is that our unconscious mind (which seems to be vast compared to the fraction of brain activity of which we're aware) has some sort of integration module which takes all the unconscious brain activity, integrates it and feeds it up to our consciousness-- giving us the illusion we're this unified whole self, rather than the ragged, somewhat chaotic and huge mess of bits and pieces of neurons and synapses comprising dozens or hundreds of different brain parts. Sometimes, through grace or introspection or psychedelics or just plain dumb luck, we break through, below the level of language, and have this direct experience, past words and reasoning. (I wish I didn't have to use metaphors like "break through" and "below the level of..." and "past"--that's for a future post.)

OK, that's one idea, which has the great advantage over a faith-based explanation that it's open to empirical investigation--change brain chemistry consistently and see if you get consistent results.

Incidentally, if it's correct, it implies that enlightenment probably doesn't represent Bedrock Truth (this is slightly supported by the accounts of "levels" of enlightenment). Maybe experiences beyond this would expose us to a zillion competing brain messages, totally incomprehensible, and perhaps meaning that further investigation would have to take place in mental hospitals.