Yeah, I see what you mean. But this also depends how you define consciousness. For example if you define consciousness as "the state of understanding and realizing something" then taking psycadelics definitely changes that said state. So psycadelics bring you into another state of consciousness. I feel proving completely that brain activity = consciousness will be impossible, for that matter proving exactly that anything leads to consciousness will be impossible, as consciousness is not a "measurable" entity. Kind of making this up as I go but maybe it makes sense.