Dr. Gina Poe, Ph.D. (@doctorpoe) is a professor in the department of integrative biology & physiology at the University of California, Los Angeles (UCLA). Her research focuses on how sleep impacts learning, memory, hormones, and emotions.
Andrew Huberman and Gina Poe discuss the relationship between sleep, learning, and hormones, including tools to enhance the quality of sleep, how to increase deep sleep, REM sleep, sleep-related hormone release, fatigue and processing of emotion, and more.
Host: Andrew Huberman (@hubermanlab)
What happens during sleep can’t be replicated by any state of wakefulness
Phases of sleep: non-rapid eye movement (non-REM) and rapid eye movement (REM) – these two stages of sleep are present in all mammals
  • Within non-REM sleep there are three phases:
    • Phase I: dozing when you first fall asleep
    • Phase II: transient state between wakefulness and slow wave sleep, almost a relaxation or hallucination state
    • Phase III: deep slow wave sleep
  • Phase IV: REM sleep – your brain is linking things conceptually during this stage and your body is paralyzed to prevent injury and acting out dreams
When you wake someone out of REM sleep, they’ll usually report being in the middle of a bizarre dream
Sleep cycles last about 90 minutes
The first 4 hours of sleep are critical for memory processing, particularly if you learned something new that day – the memory may show up in your dream
The second half of the night: REM sleep periods are longer (non-threatening background sounds will be incorporated into dreams instead of waking up), sleep is deeper, difficult to wake someone out of this stage
Growth hormone release happens most in the first deep slow wave sleep cycle – you don’t want to miss it!
  • Our bodies know when we should be sleeping and our cells are ready to respond to growth hormone release at a specific time – you can’t catch up on this release
Sleep washout period: For the first 20 minutes we’re rebuilding adenosine into ATP and cleaning out misfolded proteins and things that are broken down and need to be rebuilt
  • Could be the expansion and contraction of neurons in unison during slow-wave (first 1/3 of the night) to leave the brain in a state of preparedness for action the next day
“One of the best markers of neurological health, when we get older, is consistent bedtimes.” – Dr. Gina Poe
A perfect night of sleep: 7.5-8 hours with about 5 sleep cycles
People need different amounts of sleep but most people who sleep 4.5-5 hours of sleep for many nights experience cognitive deficits
You can’t oversleep but if you consistently need more than 9 hours or more, if may be an underlying problem (e.g., sleep apnea, inefficiency, illness, etc.)
  • Infancy, childhood, and adolescence are an exception, you need a lot of sleep during these stages
Alcohol is a REM sleep suppressant until it’s been metabolized and removed from our bodies
Sleep trackers are at best 70% accurate at tracking sleep cycles – take it with a grain of salt
People will bias how they feel about their night of sleep based on what their score says; for example if you slept well but your score says otherwise, you will think you’re more tired
Fun fact: pets wake you up more than anything (even kids) in the middle of the night
Anti-depressants inhibit REM sleep so contraindicated if you’ve experienced trauma or PTSD because they will prevent adaptive REM sleep needed to resolve emotions
Serotonin is downregulated during REM sleep which allows us to recognize novelty again and away from familiarity, making the world feel fresh and new
Sex differences related to sleep: women with high estrogen or high hormonal cycle sleep less but sleep is more efficient
The density of sleep spindles (number produced per minute) is correlated to intelligence and the ability to remember what you learned that day
  • People with schizophrenia have few sleep spindles so it’s harder to incorporate new information
  • Glutamate (involved in learning and plasticity) is released in big amounts from a specific wave (P wave) and spindles together
  • REM sleep dreams seem random because P waves are randomly activated (or at least seem random to us)
Lucid dreaming: could be a result of the separation of subcortical and cortical structures but we know little about what’s happening
  • Con: could be activating the hippocampus in a way that it’s writing new memories and maladaptive
  • Pro: you can rewrite or change a variable in your dream to an extent and knock it out of the rut of the dream so it won’t recur – this could be useful for people who tend to have recurring dreams related to PTSD and could lead to some path of recovery
The connection between our brain and central nervous system is not fully fleshed out
With trauma, REM sleep is connecting the emotionality of the event to the memory of the event over and over
Locus coeruleus: spot on the brain packed with neurons that are filled with norepinephrine; it helps prime us to respond to the environment
  • While awake, it’s important in stress response, one-trial learning, sustained attention
  • During sleep, activity slows and shuts off completely in REM sleep to erase and breakdown synapses that no longer serve us
It’s hypothesized that the locus coeruleus doesn’t stop firing in people with PTSD
  • Norepinephrine acts at synapses to prevent weakening needed to encode novelty and learning structures – it feels repeatedly like the trauma happened that day and you respond accordingly
  • This makes it harder to learn things
  • Trauma persists even if you get enough sleep because of the locus coeruleus dysfunction
Tools to improve chances of locus coeruleus function:
  • Avoid novelty late at night, avoid stress-inducing games at night, try deep breathing exercises before sleep, calm down the sympathetic nervous system, and try not to sleep when anxious or hyped up
  • Try yoga nidra, non-sleep deep rest, intentional muscle relaxation, or prayer to relax – during meditation, our brain mimics some functions of REM sleep but we don’t know the extent
  • Women: during low estrogen phases the locus coeruleus doesn’t stop firing, if you’ve experienced recent trauma consider taking estrogen during these cycles to protect against PTSD