This forum has discussed consciousness many times.
I found an interesting analogy in my reading. Parliament, Page, and Queen.
For starters, consciousness has been observed to lag 120 milliseconds behind action. By the time a person has decided to act, the action is already in progress.
The analogy works as follows (summarised). The Parliament in the brain is a loose collection of neurons that gets information and debates what needs to be done, proposing and rejecting ideas until a decision is made. As that decision is moving towards the muscles, it is also being carried by the Page, a collection of fibres, to the Queen who makes the announcement and is effectively what we think of as consciousness.
Now in what I’m reading, if the Page is delayed sufficiently or the Queen is otherwise occupied, then a person acts like a zombie – able to walk, talk and act almost normally but without a consciousness. We can think of an animal with a primitive nervous system as like this,