Essentials: Understand and Use Dreams to Learn and Forget

**Andrew D. 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. Today, we're going to talk about dreaming, learning during dreaming, as well as unlearning during dreaming, in particular unlearning of challenging emotional events. Now, numerous people throughout history have tried to make sense of dreams and in some sort of organized way, the most famous of which, of course, is Sigmund Freud, who talked about symbolic representations in dreams. A lot of that has been kind of debunked, although I think that there's some interest in what the symbols of dreaming are. And this is something that we'll talk about in more depth today, although not Freudian theory in particular. So I think in order to really think about dreams and what to do with them, and how to maximize the dream experience for sake of learning and unlearning, the best way to address this is to look at the physiology of sleep, to really just what do we know concretely about sleep? So first of all, as we get sleepy, we tend to shut our eyes, and that's because there are some autonomic centers in the brain, some neurons that control closing of the eyelids when we get sleepy. And then we transition into sleep. And sleep, regardless of how long we sleep, is generally broken up into a series of 90-minute cycles, these Ultradian cycles. 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. 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. Now, this is true regardless of whether or not you wake up at the middle of the night to use the restroom or your sleep is broken. The more sleep you're getting across the night, the more REM sleep you're going to have. And REM sleep and non-REM, as I'll refer to it, have distinctly different roles in learning and unlearning, and they are responsible for learning and unlearning of distinctly different types of information. And this has enormous implications for learning of motor skills, for unlearning of traumatic events or for processing emotionally challenging as well as emotionally pleasing events. And as we'll see, one can actually leverage their daytime activities in order to access more slow wave sleep or non-REM sleep as we'll call it, or more REM sleep depending on your particular emotional and physical needs. So it's really a remarkable stage of life that we have a lot more control and power over than you might believe. So let's start by talking about slow wave sleep or non-REM sleep. 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. Now, the interesting thing about slow wave sleep are the neuromodulators that tend to be associated with it that are most active and least active during slow wave sleep. And here's why. To remind you, neuromodulators are these chemicals that act rather slowly, but their main role is to bias particular brain circuits to be active and other brain circuits to not be active and they are associated as a consequence with certain brain functions. So we know, for instance, and just to review, acetylcholine in waking states is a neuromodulator that tends to amplify the activity of brain circuits associated with focus and attention. Norepinephrine is a neuromodulator that tends to amplify the brain circuits associated with alertness and the desire to move. Serotonin is the neuromodulator that's released and tends to amplify the circuits in the brain and body that are associated with bliss and the desire to remain still. And dopamine is the neuromodulator that's released and is associated with amplification of the neural circuits in the brain and body associated with pursuing goals and pleasure and reward. 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 you can think of slow wave sleep as these big sweeping waves of activity through the brain and a kind of distortion of space and time so that we're not really focusing on any one thing. 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. 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, the sensation of kind of bliss or well-being, but not a lot of movement. And during sleep, you tend not to move. Now in slow wave sleep, you can move. You're not paralyzed, so you can roll over. If people are going to sleepwalk, typically it's going to be during slow wave sleep. And what studies have shown through some kind of sadistic experiments where people are deprived specifically of slow wave sleep, and that can be done by waking them up as soon as the electrode recordings show that they're in slow wave sleep, or by chemically altering their sleep so that it biases them away from slow wave sleep. What studies have shown is that motor learning is generally occurring in slow wave sleep. So let's say the day before you go to sleep, you were learning some new dance move, or you were learning some specific motor skill, either a fine motor skill or a coarse motor skill. Learning of those skills is happening primarily during slow wave sleep in the early part of the night. I'd like to take a quick break and acknowledge our sponsor AG1. 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Right now, they're giving away five free travel packs plus a year supply of vitamin D3 K2. Again, that's drinkag1.com/huberman to claim that special offer. In addition, slow wave sleep has been shown to be important for the learning of detailed information. So we can think of slow wave sleep as important for motor learning, motor skill learning and for the learning of specific details about specific events. And this turns out to be fundamentally important because now we know that slow wave sleep is primarily in the early part of the night and motor learning is occurring primarily early in the night and detail learning is occurring early in the night. I want to talk about REM sleep or rapid eye movement sleep. REM sleep and rapid eye movement sleep, as I mentioned before, occurs throughout the night 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. REM sleep is fascinating. It was discovered in the 50s when a sleep laboratory in Chicago, the researchers observed that people's eyes were moving under their eyelids. Now, something very important that we're going to address when we talk about trauma later is that the eye movements are not just side to side, they're very erratic in all different directions. One thing that I don't think anyone, I've never heard anyone really talk about publicly is why eye movements during sleep, right? Eyes are closed and sometimes people's eyelids will be a little bit open and their eyes are darting around, especially in little kids. I don't suggest you do this. I'm not even sure it's ethical, but it has been done where you pull back the eyelids of a kid while they're sleeping and their eyes are kind of darting all over the place. Rapid eye movement sleep is fascinating and occurs because there are connections between the brainstem, an area called the pons and areas of the thalamus and the top of the brainstem that are involved in generating movements in different directions, sometimes called saccades, although sometimes during rapid eye movement sleep, it's not just rapid, it's kind of a jittery side to side thing, and then the eyeballs kind of roll. It's really pretty creepy to look at if you see. So what's happening there is the circuitry that is involved in conscious eye movements is kind of going haywire, but it's not haywire. It's these waves of activity from the brainstem up to the so-called thalamus, which is an area that filters sensory information and then up to the cortex. And the cortex of course is involved in conscious perceptions. In REM sleep, serotonin is essentially absent. Okay, so this molecule, this neuromodulator that tends to create the feeling of bliss and well-being and just calm placidity is absent. In addition to that, norepinephrine, this molecule that's involved in movement and alertness is absolutely absent. It's probably one of the few times in our life that epinephrine is essentially at zero activity within our system. And that has a number of very important implications for the sorts of dreaming that occur during REM sleep and the sorts of learning that can occur in REM sleep and unlearning. First of all, in REM sleep, we are paralyzed. We are experiencing what's called atonia, which just means that we're completely laid out and paralyzed. We also tend to experience whatever it is that we're dreaming about as a kind of hallucination or a hallucinatory activity. So in REM, our eyes are moving, but the rest of our body is paralyzed and we are hallucinating. There's no epinephrine around. Epinephrine doesn't just create a desire to move and alertness. It is also the chemical signature of fear and anxiety.