A lot of comparison can be made between the dissociative drugs. DXM is obviously different from Ketamine, but you can see parallels in their effects. In William White's FAQ, he talks about the effects of DXM at progressively higher doses. It shuts down access to your brain piece by piece, but in a sort of different way than alcohol. It's as if they're still there and running, but anesthetized from the point of view of your conscious mind. You lose contact with the outside world, then your extremities, then finally pieces of your own mind. It's like how they say a person who loses a leg has more dexterity in their other limbs, or a blind person can hear better. The more you lose, the more your consciousness's capacity is redoubled over it's remaining range. You find yourself hyper-awake and focused as your mind loses contact with your long-term then mid-term memory, and eventually you end up in a loop of whatever has happened to enter your perception in the last 30 seconds.
Specifically with Plateau Sigma of DXM there are reports of people hearing voices telling their conscious mind what to do, and them not understanding the concept of resistance. It's as if the part of their brains that makes decisions is also outside of the little bubble that contains their waking mind. And everything outside of that bubble is automatically controlled by the subconscious.
Anyway, the point is that these disassociatives cause a looping effect, and an unusually heightened capacity in certain way via their unique brand of super-focusing. Also, with DXM at least, your mind also stores memories in such a different way that your sober mind doesn't know how to access them until you've achieve that high a few different times, indicating that your brain is existing in a different state, separate from the usual states of asleep, awake, meditating, etc. Definite potential for a mental shakeup, but whether any of this actually constitutes a psychedelic, I don't know.
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