The first half of the night features more deep non-REM sleep, while the second half features more light non-REM and REM sleep.

“REM sleep and rapid eye movement sleep, as I mentioned before, occurs throughout the night, but you're gonna have more of it. A larger percentage of these 90 minute sleep cycles is going to be comprised of REM sleep as you get toward morning.”

“So early in the night these 90 minute cycles tend to be comprised more of shallow sleep and slow wave sleep. So stage one, stage two, et cetera, and what we call slow wave sleep. [...] And we tend to have less so-called REM sleep, R-E-M sleep, which stands for rapid eye movement sleep.”

“What changes to your question is the ratio of non REM to REM within that 90 minute cycle as you move across the night. And what I mean by this is, in the first half of the night, the majority of those 90 minute cycles are comprised of a lot of deep non REM sleep, that's when I get my stage three and four of deep non REM sleep. Once I push through to the second half of the night, now that seesaw balance changes. And instead, the majority of those 90 minute cycles are comprised either of this lighter form of non REM sleep, stage two non REM sleep, and much more and increasingly more rapid eye movement sleep.”

“And you do that reliably, repeatedly, and I will be doing that, and I do do that every 90 minutes. At least that's the average for most adults, it's different in different species.”

“What changes to your question is the ratio of non REM to REM within that 90 minute cycle as you move across the night.”

“When you go to sleep at night, whether or not you sleep six hours or four hours or eight hours or 10 hours, that entire period of sleep is broken up into these 90-minute ultradian cycles.”

“that entire period of sleep is broken up into these 90-minute ultradian cycles. Early in the night, you tend to have more slow-wave sleep. Later in the night, you tend to have more REM sleep. But nonetheless, your sleep is broken up into these 90-minute cycles.”

“every 90 minutes or so, your patterns of sleep-- that is the percentage or ratio rather of slow wave sleep to light sleep to rapid eye movement sleep changes in a way such that each 90-minute cycle gates the next cycle.”

“So those are the four states of sleep, of human sleep, and we cycle through them every 90 minutes or so.”

“And the last few cycles, you're just doing the end to REM sleep cycle which takes less time.”

“the ratio of non-rem to REM within your 90minut cycle is not stable and what I mean is as you move across the night the the the domination of those two types of sleep within the 90-minute cycle changes such that in the first half of the night the majority of those 90 minutes Cycles are comprised of lots of deep non-rem sleep but very little REM sleep but as we push through to the second half of the night now that ratio balance that seesaw balance shifts over and instead we have much more rapid ey movement sleep and very little deep sleep”

“when you go through these on average 90minut Cycles you get most of your non-rem sleep first and then you'll have this bout of REM sleep at the end”

“you get most of your deep sleep in the first half and you get most of your REM sleep in the second half and particularly in the last quarter of the night”

“For every 90-minute cycle that we have during a night of sleep, we tend to start having more and more REM sleep. So more of that 90-minute cycle is comprised of REM sleep and less of slow wave sleep.”

“So early in the night, these 90-minute cycles tend to be comprised more of shallow sleep and slow wave sleep. And we tend to have less so-called REM sleep, R-E-M sleep, which stands for Rapid Eye Movement sleep.”

“But you're going to have more of it-- a larger percentage of these 90-minute sleep cycles is going to be comprised of REM sleep as you get toward morning.”

“In the first half of the night, the majority of those 90-minute cycles are comprised of lots of deep non-REM sleep. That's when I get my stage three and four of deep nonREM sleep. Once I push through to the second half of the night, now that seesaw balance changes and instead the majority of those 90minute cycles are comprised either of this lighter form of non-REM sleep, stage 2 non-REM sleep, and much more and increasingly more rapid eye movement sleep.”

“in this arc of the night uh slowwave sleep predominates uh early in the night and then REM sleep”

“And you do that reliably repeatedly. And I will be doing that every 90 minutes at least. That's the average for most adults.”

“So, your REM sleep happens in the latter part of the night. So you get deep sleep in the first part, then REM at the last. And if he's cutting his REM sleep to do that, I wouldn't make that trade-off.”

“such that in the first half of the night the majority of your 90-minute sleep cycles are comprised of lots of deep non REM sleep and very little REM sleep but as you push through to the second half of the night now the seesaw balance changes and the majority of those sleep cycles are comprised much more of rapid eye movement sleep and almost no deep sleep”

“you have these two different types of sleep and they will essentially as you fall asleep here in at the Sleep Center at Berkeley they will go into essentially a battle for brain domination throughout the night and that's cerebral war between non REM and REM is going to be won and lost every 90 minutes and then replayed every 90 minutes to create what we call a standard cycling architecture of sleep or what we call a hip negraph of sleep”

“so we have these two types of sleep non-rem and rem and they will play out in this beautiful battle for brain domination throughout the night and that cerebral war is going to be won and lost every 90 minutes and then replayed every 90 minutes to create the standard cycling 90-minute architecture of the sleep cycle that then just repeats throughout the night”

“the ratio of non-rem to rem within each 90 minute cycle as we move across the night changes and what i mean by this is in the first half of the night the majority of those 90-minute cycles are going to be comprised of lots of deep non-rem sleep stages three and four non-rem sleep and very little rem sleep but as you push through to the second half of the night now the brain has a shift in its taste preference for what it wants to feast on at the finger buffet of sleep stages and instead now it actually wants to consume much more rapid eye movement sleep and it's lost its appetite for deep non-rem sleep so in the second half of the night the majority of those 90-minute cycles are comprised much more of rapid eye movement sleep”

“you have to go through three to get to four you have to go to three to get to four you have to go from two to get to three to get to four”

“that cerebral war between non-rem and rem is going to be won and lost every 90 minutes and then replayed every 90 minutes to create what we call a standard cycling architecture of sleep or what we call a hypnogram of sleep”

“What changes, however, is the ratio of non-REM to REM within those 90-minute cycles as you move across the night such that in the first half of the night, the majority of those 90-minute cycles are comprised of lots of deep non-REM sleep and very little REM sleep. In the second half of the night, that balance shifts, and now you get much more REM sleep in the late morning hours and very little deep sleep.”

“we go through these 90-minute cycles, we, human beings, it's different for different animals, you always go into deep non-REM sleep first and then you always have REM sleep second. And that repeats every 90 minutes throughout the night.”

“The second cycle, you'll have a little bit less deep and a little more stage two and a little more REM. By your third cycle, you might have no deep left. It's all just stage two and REM.”