I agree with Alyzarin. DMT is way more like hypnagogia than actual dreams...yet unlike some hypnagogia, definitely cannot be directed or controlled. DMT is like a seizure...you can't control it. However I can only speak for the smoked variety, I have no idea whether or not an ayahuasca or other ingested method can be controlled in anyway. But smoking it is so intense...I can't even imagine attempting to exert any control.

"Don't fight it, you'll get brain bubbles."

Also Rick Strassman, author of The Spirit Molecule, has openly admitted that his theories about DMT are entirely speculation, and even expressed his disappointment that people seem to state his speculations as fact. DMT has never been found in the human brain/pineal gland, nor has it been shown to be directly associated to dreaming/NDEs/etc.