Essentials: Use Sleep to Enhance Learning, Memory & Emotional State | Dr. Gina Poe

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Welcome to Huberman Lab Essentials, [music] where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I’m Andrew Huberman and I’m a professor of neurobiology and opthalmology at Stanford School of Medicine. And now for my discussion with Dr. Gina Poe. Dr.

Gino Poe, welcome. >> Thank you. >> I’ve really been looking forward to this conversation. I know that many people are going to be excited to learn about your work as it relates to sleep, as it relates to problem solving, creativity, and a number of other important topics. To start things off, I would love for you to educate us a bit about this thing that we are all familiar with and yet very few of us understand, which is sleep.

Could you describe the various phases of sleep that exist, what distinguish them, and perhaps frame this within the context of what would a perfect night’s sleep look like? >> All right. So sleep is really different from wakefulness and in fact can’t be replaced by any state of wakefulness that we’ve been able to come up with so far. Our brain chemistry is completely different and in the different stages of sleep which there are is nonREM and REM are the two major states of sleep. Those two states are entirely different from one another too.

And even within nonREM there are three states. Stage one, which is what you slip into when you first falling asleep. It’s dozing. There’s kind of an interesting rhythm that goes on in the brain. It’s kind of a fast gamma rhythm.

And then there’s stage two, which is a really cool state. We sort of used to ignore sleep researchers because it was a transient state between wakefulness and the deep stage three slowwave sleep, which is the most impressively different, which is when big slow waves sweep through our brain. And now we’ve realized that it cleans our brain. Um, one of the things that those big slow waves do is cleans our brain and does other really important things to restore us from a day of wakefulness. And then REM sleep, which is the most popular because that’s where we have the most active dreams.

When you wake up someone out of REM sleep, they’ll almost always report having dreamed something really bizarre. That’s called REM sleep, rapid eye movement sleep. So those are the four states of sleep of human sleep. And we cycle through them every 90 minutes or so. And then we start over again.

And we have about five of those per night for a perfect night’s sleep. Four or five, something like that. So a perfect night’s sleep is 7 and 1 half, 8 hours. And >> what about the sleep where we are lightly asleep >> and we might have a dream that has us somehow thinking about movement or that we jolt ourselves awake. That often happens early in the night, right?

Yeah. That’s the first stage, stage one and stage two of sleep. And stage two sleep is really cool because that has something called sleep spindles and K complexes. And what sleep spindles are are a little of activity that’s 10 to 15 hertz in frequency. It’s a conversation between the phalamus and the cortex.

The phalamus is the gateway to consciousness and the neoortex, you know, processes all our cognition. And if you wake up out of that state, you will often report a dream like a hallucination style dream. It won’t be a long dream report like you have out of REM sleep, but it will be some hallucination state. >> Are they quite different than the patterns of sleep and dreaming that occur later in the night or toward morning? >> There is some evidence that the first 4 hours of sleep are very important for memory processing.

And in fact, if you’ve learned something new that day or have experienced a new sensory motor experience, then your early sleep dreams will incorporate that experience much more than the later sleep dreams. Later as that memory gets consolidated from the early structures which are the hippocampus deep in the temporal lobe to the cortex in a distributed fashion that memory seems to move from that hippocampus to the cortex and also the dreams that incorporate that memory also move later in the night. So >> there was a great study by Sedarto Rayo who studied the consolidation of memories from the hippocampus to the cortex in a rat across the period of a full day sleep because rats sleep in the daytime. And he found that each subsequent rim sleep period moved that memory from the hippocampus to the f first area that projects to it and then the second area and then the third area. and you can see the memory moving um through the throughout the sleep.

There’s a number of different hormones associated with the different stages of sleep. We know that melatonin is a hormone >> of night time >> of nighttime that makes us sleepy. What about growth hormone release? When does that occur during sleep? >> So growth hormone release happens all day long and all night long.

But the deep slow wave sleep that you get, the very first sleep cycle is when you get a big bolus of growth hormone release. and in men and women equally. And if you miss that first deep slow wave sleep period, you also miss that big bolus of growth hormone release. And you might get ultimately across the day just as much overall growth hormone release. But andologists will tell you that big bololises do different things than a little bit eaked out over time.

There’s also a big push to synthesize proteins. So that’s when the protein synthesis part that builds memories for example in our brain happens in that first cycle of sleep. So you don’t want to miss that especially if you’ve learned something really big and needs needs more synaptic space to encode it. >> How would somebody miss that first 90 minutes >> depriving themselves? Yeah.

So, so let’s say I normally go to sleep at 10:00 p. m. >> and then from 10 to 11:30 would be this first phase of sleep and that’s when the growth hormone big bololis of growth hormone would be released. Does that mean that if I go to sleep instead at 11:30 or midnight that I miss that first phase of sleep? Why is it not the case that I get that first phase of sleep just simply starting later?

Every cell in our body has a clock and all of those circadian clocks are synchronized and so our cells are ready to respond to that growth hormone release at a particular time and if we miss it and it’s a time in relation to melatonin also. So if you miss it, yeah, you might get some growth hormone release, but it’s occurring at a time when that your clock has already moved to the next phase. And so it’s it’s just a clock thing. So what this means is that we should have fairly consistent bedtimes in addition to fairly consistent wake times. Is that right?

Exactly. And in fact, one of the best markers of good neurological health when we get older is consistent bedtimes. >> What other things inhibit growth hormone release or other components of this first stage of sleep? Are there things that I perhaps do in the preceding hours or the preceding day like ingest caffeine or alcohol that can make that first stage of sleep less effective even if I’m going to sleep at the same time? >> Alcohol definitely will do that because alcohol is a REM sleep suppressant and it even suppresses some of that stage two transition to REM with those sleep spindles.

And those sleep spindles, we didn’t talk about their function yet, but they’re really important for moving memories to our cortex. It’s a unique time when our hippocampus the sort of like the RAM of our brains writes it to a hard disk which is the cortex and there it’s a unique time when they’re connected. So if you don’t want to miss that you don’t want to miss REM sleep when is also a part of the consolidation process and alcohol before we go to sleep will do that until we’ve metabolized alc