Types of Consciousness
Stage 1 sleep demonstrates that states of consciousness not only fluidly run into each other, but often are not recognized.
Delirium - fluctuating states of consciousness confuse the heck out of people but are very common. You often see it in elderly people, who will shift suddenly from talking about the stock market to forgetting your name or where they are. However, intoxication, often with alcohol or marijuana but now progressively more commonly through prescription medications, can produce the same effect.
Early morning wakefulness. Getting up is hard to do, as your cold brain tries to warm up and notice what's going on. This is essentially a state somewhere between stage 1 sleep and wakefulness, and can lapse in and out of the two for many minutes before people stop hitting the snooze control and actually rouse out of bed.
REM sleep - commonly thought of as dream sleep (we actually can dream in any stage of sleep) REM is a bizarre state of consciousness. Temperature controls disappear, while the many kludges of the brain seem to communicate with each other in a sometimes forlorn attempt to take the new information of the previous day, anneal it with old memories, and remake it into newer information the body then uses to remake itself. A time of much rewiring and rejiggering of memory and thoughts, including peak testosterone production, the fragments of what REM produces as it helps remake the brain become what we call complex dreams.