REM sleep

[nibor]

I have heard that when you sleep you have 90 minute periods of deep sleep mixed with REM sleep. But how many minutes after you fall asleep
does your first REM period begin?

/nibor

[Logic]

Every hour or so, with decreasing time between intervals.

[nibor]

So, if you don't have any REM-sleep the first hour you sleep, what about dreams that you have just minutes (or directly) after you fall asleep? Are those some other thing, like Astral projection?

[upstream]

I have heard that when you sleep you have 90 minute periods of deep sleep mixed with REM sleep. But how many minutes after you fall asleep does your first REM period begin?

It depends mostly on the amount of prior wakefulness. The more time you have been awake, the more time your brain need to recuperate before active sleep (REM). All this works like a balance sheet and called the homeostatic process of sleep regulation.

On the other hand there is an another process, the circadian that increase and decrease the possibility of REM onset in cycles along the day. The counteracting interaction of these processes at bed-, and waketime establish the monophasic sleep architecture that most people follow, that is sleeping 5-10 hours of sleep without interruption.

Hypnagogic pictures could be considered as attempts of the brain to enter REM sleep directly from wakefulness. This isn't possible except the case when the need for deep sleep is already sated and the circadian phase is proper (or you are good in stabilizing and manipulating the hypnagogics).

So the REM latency you have asked for is between 0 and 80 min. Below 15 min the REM sleep period is called sleep onset REM period (SOREMP) which is desirable for entering the dream state fully lucid. To have more SOREMP you need to manipulate the architecture of your sleep by wisely placed interruptions and naps.