Dr. Gina Poe on Sleep Stages, Memory and Five Habits for Better Sleep

High-Level Overview

Mel Robbins sits down with Dr. Gina Poe, a UCLA neuroscientist who has studied the functions of sleep for about 30 years, for what Mel calls a "private class" on the science of sleep. Dr. Poe walks through what changes in the brain when we fall asleep, what happens in each stage of the night, why the first and second halves of the night do different jobs, how sleep lets the brain clean itself and lock in learning, and how REM sleep may help take the sting out of painful memories. The conversation ends with five simple, free recommendations for better sleep and a candid look at Dr. Poe's own bedtime routine.

The tone is upbeat, curious and accessible. Mel plays the enthusiastic student, repeatedly pausing to translate the science into everyday language ("habits are made in your bedroom"), while Dr. Poe answers plainly and warmly. The conversation moves from basic neuroscience to the architecture of a night's sleep and then to practical habits.

The Discussion Explores:

• Why sleep is far more than rest: immunity, cognition, emotion, growth and repair
• How brain chemistry switches when we fall asleep, including acetylcholine turning off
• The stages of sleep (N1, N2, N3 and REM) and why it is called "falling" asleep
• Deep sleep as the brain's nightly cleaning wave
• REM sleep, schemas, creativity and neuroplasticity
• How REM sleep separates the emotional sting from painful memories
• Circadian rhythms, morning light, growth hormone and consistent bedtimes
• Five recommendations for better sleep and Dr. Poe's own routine

Deep Dive into Main Ideas

Why We Sleep and What Changes in the Brain

Mel opens with what she calls a possibly stupid question: why do we sleep? Dr. Poe says it is a great question that scientists have been working on for at least 70 years. So many things happen during sleep that cannot happen at any other time: sleep is great for the immune system, for cognition, for the emotional system and for growth and repair.

The difference between waking and sleeping is huge at the chemical level. When we fall asleep, the neurotransmitters in the brain change their composition. Acetylcholine, which is important for paying attention to the environment, switches off during non-REM sleep, the first state we enter. Dr. Poe notes that some animals sleep "unihemispherically, one brain hemisphere at a time, and in the sleeping hemisphere acetylcholine switches off. Her larger point is that sleep is not laziness. Because the brain is doing essential things that cannot be done while awake, she calls sleep another kind of work time, even though it's a pleasant work time," and says knowing this makes it easier to justify scheduling it like anything else in a workaholic world.

What a Perfect Night's Sleep Looks Like

Asked for a benchmark, Dr. Poe says to look at a 10-year-old. Their sleep responds beautifully both to how long they have been awake (the homeostatic drive) and to the time of day (the circadian rhythm). "Don't ever wake up a 10-year-old if you can possibly help it," she says. Teenagers need just as much sleep, about 8 to 10 hours, but their clocks shift later. Sleep usually stays good until about 40 or 50, when it can become less efficient.

For adults, the healthy target is around seven and a half to eight hours, plus or minus an hour. Some people need nine; some do fine on six for a while. Your body tells you, mainly through how sleepy you feel during the day. Ideally you are woken by sunlight, so Mel draws out a practical takeaway: pick your wake-up time, then count back seven to nine hours to find when you need to fall asleep.

The Stages of Sleep and Why We "Fall" Asleep

The night begins with dozing (N1), which lasts about two to five minutes. Our memory stops recording, which is why you forget the last couple of minutes of a book or podcast, or, as Mel jokes, the last minute and a half of what she said to her husband before he started snoring. Between N1 and N2 come hypnagogic hallucinations, as the brain loses hold of reality while different parts fall asleep at different times. These can be as mundane as feeling you are falling off a step, which prompts Mel's realization: "Is that why they call it falling asleep?" They can also be as frightening as sensing a monster on your chest, because unlike REM dreams, they occur without the muscle paralysis (atonia) that normally stops us acting out dreams.

N2 is an active stage with fairly vivid but not story-like dreams. N3, deep or slow-wave sleep, features synchronous waves of activity that break up consciousness; people woken from it report no dreams and are hard to wake. A full cycle runs from N1 to N2 to N3, back to N2, then REM, taking about 90 minutes on average in humans. Order matters: remove REM and memories cannot be consolidated; remove N3 and you wake up with what Dr. Poe calls a junky brain. About five cycles a night is ideal.

Deep Sleep: The Brain's Cleaning Wave

Deep N3 sleep is when the brain cleans itself. During waking hours proteins get unfolded, things break down and energy is used up; all of that is restored in deep sleep. Dr. Poe describes one wave per second sweeping from the front of the brain to the back, pushing the junk into the cerebrospinal fluid. Mel compares it to a Zamboni clearing the ice.

The practical catch is timing. N3 lasts about 20 to 30 minutes per cycle and is concentrated in the first half of the night, with much less later on. "If you miss the first half of the night, you'll miss most of that N3 sleep, which is the cleaning stage," Dr. Poe explains. Mel underlines the message: you cannot cheat sleep by going to bed late, because you lose the cleaning and memory assimilation you need to wake up refreshed.

REM Sleep, Schemas and Neuroplasticity

REM sleep is also called paradoxical sleep, because electrically the brain looks awake, with vivid dreams, while chemically it is very different. Wake someone during REM and they will report a dream about 90% of the time, even people who claim they never dream. Dr. Poe thinks people forget dreams simply because they stay solidly asleep. Two chemicals that tune us to novelty in the outside world, norepinephrine (noradrenaline) and serotonin, are switched off, so the brain turns inward. It is "not a time for new learning," she says, but a time to assimilate what you already learned into coherent patterns.

She calls these patterns schemas, clusters of related information such as everything we associate with Christmas or summer, and compares them to Lego boxes: during the day you collect the pieces, and during sleep you assemble them. This is what makes REM important for creativity and for changing your mind. Mel's summary: just as abs are made in the kitchen, "habits are made in your bedroom while you're sleeping," because that is when the brain locks in the day's learning.

First Half vs. Second Half of the Night, and Healing Painful Memories

Dr. Poe distinguishes the two halves of the night. The first half is more for locking in and sealing the things you learned during the day. The second half, with more REM, is for building new schemas, making new connections, changing your mind and resolving the emotional side of memories.

Her lab's current research, done with other labs, focuses on this. When you recall a painful event from a year or ten years ago, it is adaptive to remember the facts, but not to feel the pain again. REM sleep appears to separate the novelty, immediacy and physical reality of the emotion from the facts you keep for life. In people with insomnia and poor REM sleep, norepinephrine is too active because they are anxious while they sleep, so memories keep feeling as though they just happened. Mel connects this to trauma and chronic pain, and Dr. Poe agrees that good sleep is not just helpful for healing: "it's necessary to heal."

Circadian Rhythms and Morning Light

Every cell has a clock, and they are aligned by a master clock in the brain, the suprachiasmatic nucleus (SCN), which is reset each day by light entering the eyes. Because everyone's clock runs roughly, not exactly, on 24 hours, it needs daily resetting: "Bright light in the morning tells you time zero." Even a cloudy or rainy day outdoors is much brighter than indoor light. Twenty minutes is plenty, ideally while exercising, and even two minutes makes a difference. Dr. Poe also suggests keeping meals regular.

The flip side is avoiding bright light, especially blue light, at night. Strong blue light from phones, computers and TVs tells the circadian system it might be morning and shifts your clock later.

Growth Hormone, Melatonin and a Consistent Bedtime

Growth hormone repairs muscles, builds proteins from the amino acids we eat, helps consolidate memories and rebuilds damaged tissue. It is released in small spurts during the day, but when you go to sleep at the right time for your clock, while melatonin is being released, the two together push growth hormone release to about 10 times the waking level. Delay sleep past that melatonin surge and the growth hormone surge is much smaller.

Asked whether a melatonin supplement could produce the same spike, Dr. Poe says we don't know but she doubts it, because many other things happen alongside natural melatonin. She adds that melatonin supplements are not regulated by the FDA, so a pill might contain zero melatonin or ten times what you need. Mel compares the lesson to her kids' bedtime routine (same time, bath, story, pajamas, goodnight) and Dr. Poe agrees adults need the same.

Five Recommendations and Dr. Poe's Own Routine

Dr. Poe's five recommendations: get bright light in the morning; keep a consistent bedtime; take a warm bath at night, which vasodilates the hands and feet and helps the core cool by about half a degree, as it does when we fall asleep; exercise during the day hard enough to get your heart pounding, which for reasons not fully known gives you a wonderful night's sleep; and avoid too much caffeine too late.

Her own routine: her best bedtime is around 10:30 or 11, so she tries to stop working an hour before, takes a shower, then either prays, relaxes and breathes deeply, or plays "a really dumb little game" on her phone with blue light turned off, a simple number game where losing doesn't matter. She is usually asleep within about 10 minutes, with the phone on do not disturb, though she agrees it is better to keep the phone out of the bedroom. Reading a relaxing book works well for others. Mel closes by asking listeners to pick three changes; hers are morning light, going to bed earlier, and a nightly bath or shower.

Conclusion

Dr. Gina Poe reframes sleep as active, essential work rather than downtime. Early in the night the brain cleans itself with slow waves and seals in the day's learning; later, REM sleep assembles those pieces into schemas, fuels creativity and strips painful memories of their emotional charge. Because deep sleep clusters early and growth hormone depends on sleeping in sync with your clock, going to bed late costs more than just hours. The fixes she offers are simple and free: morning light, a consistent bedtime, a warm bath, daily exercise and less late caffeine. It is a clear, friendly primer for anyone who has ever treated sleep as optional.

This is a summary of "Dr. Gina Poe: How to Get Better Sleep and Boost Your Learning, Memory and Energy" from The Mel Robbins Podcast, giving you the GIST so you can decide if you want the REST. Listen to the full episode.