And that's not even limited to your brain! The whole world is forever in flux, if any state would ever be static then relatively there would be no way or viewpoint from which to distinguish two moments :D
OK what I'm really hoping for is something more definite from the OP, whatever Leary did or didn't mean. Markers & measures are good but does this actually prove that psychedelics bring about measurable changes?
Personally I interpreted what was posted as being more to do with a subjective counsciouness change than measurable activity - however it's vague enough for anyone to project their own preferences onto.
QFT, everybody's brain is constantly changing every second. It never stagnates into a set configuration for even a moment.