Serotonin levels are high during slow wave sleep, contributing to a sensation of well-being and reduced movement.

“So in slow wave sleep something really interesting happens. There is essentially no acetylcholine. Acetylcholine production and release and action from the two major sites, which are in the brainstem, which from a nucleus if it's a”

“and a lot of serotonin. And serotonin again is associated with this desire, this sensation of kind of bliss or wellbeing, but not a lot of movement.”

“So in slow wave sleep, something really interesting happens. There's essentially no acetylcholine. And acetylcholine, as I just mentioned, is associated with focus.”

“So slow wave sleep is characterized by a particular pattern of brain activity in which the brain is metabolically active but that there's these big sweeping waves of activity that include a lot of the brain.”

“So there's something associated with the movement circuitry going on in slow wave sleep. And remember, this is happening mostly at the beginning of the night. Your sleep is dominated by slow wave sleep. So no acetylcholine, very little norepinephrine, although there is some, and a lot of serotonin. And serotonin, again, is associated with this desire, this sensation of bliss or well-being but not a lot of movement.”

“Now, the other molecules that are very active at that time are norepinephrine, which is a little bit surprising. Because normally, in waking states, norepinephrine is going to be associated with a lot of alertness and the desire to move. But there's not a ton of norepinephrine around in slow wave sleep. But it is around.”