The brain is online during dreams. The experiences you have during the day are codified and associated during dream sleep. If people are awakened from this state, they are ready to go.

A while later, I lingered in the hinterlands of sleep. Sometimes I think there is more rest in that place between wakefulness and sleep than there is in true sleep. The mind walks in the twilight of both states, and finds the truths that are hidden alike by daylight and dreams. Things we are not ready to know abide in that place, awaiting that unguarded frame of mind.

I sleep lightly and tread to keep my head out of the sea of dreams.

She sleeps. And now she wakes each day a little less. And, each day, takes less and less nourishment, as if grudging the least moment of wakefulness, for, from the movement under her eyelids, and the somnolent gestures of her hands and feet, it seems as if her dreams grow more urgent and intense, as if the life she lives in the closed world of dreams is now about to possess her utterly, as if her small, increasingly reluctant wakenings were an interpretation of some more vital existence, so she is loath to spend even those necessary moments of wakefulness with us, wakings strange as her sleepings. Her marvellous fate - a sleep more lifelike than the living, a dream which consumes the world.
'And, sir,' concluded Fevvers, in a voice that now took on the sombre, majestic tones of a great organ, 'we do believe . . . her dream will be the coming century.
'And, oh, God . . . how frequently she weeps!

I cannot sleep for dreaming; I cannot dream but I wake and walk about the house as though I'd find you coming through some door.

I have come to the borders of sleep,/ The unfathomable deep/ Forest where all must lose/ Their way.