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

**Andrew Huberman** (0:00)
Welcome to Huberman Lab Essentials, 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 ophthalmology at Stanford School of Medicine. And now for my discussion with Dr. Gina Poe. Dr. Gina Poe, welcome.

**Gina Poe** (0:21)
Thank you.

**Andrew Huberman** (0:22)
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 distinguished them, and perhaps frame this within the context of what would a perfect night's sleep look like?

**Gina Poe** (0:53)
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 as non-REM and REM, are the two major states of sleep. Those two states are entirely different from one another, too. And even within non-REM, 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, slow wave sleep, which is the most impressively different, which is when big slow waves sweep through our brain. And now we realize that it cleans our brain. 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 seven and a half, eight hours.

**Andrew Huberman** (2:23)
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?

**Gina Poe** (2:34)
Yeah, that's the first stage, stage one and stage two of sleep. And stage two of sleep is really cool because that has something called sleep spindles and K complexes. And what sleep spindles are, are a little brrt of activity that's 10 to 15 hertz in frequency. It's a conversation between the thalamus and the cortex. The thalamus is the gateway to consciousness.
And the neocortex, 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.

**Andrew Huberman** (3:14)
Are they quite different than the patterns of sleep and dreaming that occur later in the night or toward morning?

**Gina Poe** (3:20)
There is some evidence that the first four 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 Siddhartha Ribeiro, 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 REM sleep period moved that memory from the hippocampus to the first area that projects to it, and then the second area, and then the third area. And you can see the memory moving throughout the sleep.