Use Sleep to Enhance Learning, Memory & Emotional State | Dr. Gina Poe
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- Dr. Gina Poe
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- ~4 min
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- 13 Feb 2023
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KEYPOINTS
- 01
The first 90-minute cycle is timed to your body clock
Most growth hormone is released in one big pulse during the first sleep cycle, along with a surge of protein synthesis that helps build memories. Poe explains that every cell's clock, timed relative to melatonin, expects this pulse at a particular time. If you go to bed late, you may still release some growth hormone, but your tissues have already moved on to the next phase.
- 02
Alcohol damages the memory-consolidating parts of sleep
Alcohol suppresses REM sleep and the sleep spindles of the stage-two transition into REM. During spindles, the hippocampus (the brain's RAM) writes memories to the cortex (the hard disk). Poe agrees with Huberman's suggestion of no alcohol in the 4–6 hours before sleep, or none at all, while saying she doesn't know the dose-response.
- 03
Later cycles are a different stage you shouldn't cut short
Each successive cycle contains more REM sleep, while growth hormone and melatonin decline and other hormones rise. Cutting the night short removes REM-heavy sleep, which is involved in consolidating memories and updating your mental models (schemas).
- 04
REM sleep clears the hippocampus by switching off noradrenaline
The locus coeruleus releases norepinephrine (and seems to be the hippocampus's source of dopamine), which strengthens synapses while you're awake. It falls silent only during REM sleep. Poe says that silence lets synapses weaken, erasing the 'thumb drive' once its contents have been written to the cortex, which is essential for continued learning.
- 05
In PTSD, the locus coeruleus may not switch off during REM
Norepinephrine levels in people with PTSD look normal during the day and early night but diverge in the early-morning hours, when REM sleep peaks. Heart-rate patterns point the same way. Poe's preliminary rat data agree. The traumatic memory then stays stuck in novelty-encoding structures instead of being erased after it's consolidated.
- 06
Common antidepressants may work against trauma recovery during sleep
Poe, stressing she isn't a physician, argues that drugs keeping norepinephrine in synapses (such as bupropion) suppress REM sleep, and that any REM sleep you do get is 'noradrenergic' REM. She thinks that may hinder the adaptive REM needed to resolve trauma. She says SSRIs are problematic too.
- 07
Sleep spindles track learning
Baseline spindle density correlates with intelligence. Whatever your baseline, an increase in spindles the night after learning almost perfectly predicts how well you consolidate the new information into existing knowledge. People with schizophrenia have very few spindles. Work by Julie Seibt and Anita Lüthi links spindles to plasticity in distal dendrites, which Poe thinks may support creativity.
- 08
You probably can't oversleep
In a study Poe describes where people could stay in bed 12 hours, they first slept 10–11 hours to pay back debt, then settled at about 8 hours 15 minutes and spent the rest of the time awake. Adolescents and other developing brains are the exception: let them sleep, because development has its own windows.
- 09
Opioid withdrawal leaves the stress system without its brake
Long-term opioid use reduces the number of opioid receptors. When the drug is withdrawn, your own opioids can't calm the locus coeruleus, which fires constantly, disrupts sleep and feels like anxious depression. Poe calls sleep disturbance a strong predictor of relapse, and her group (with Pamela Kennedy at UCLA) is testing whether restoring sleep reduces relapse in animals.
EXAMPLES
- 01
Psychedelics as a REM-like state
Poe describes psychedelic states as REM-sleep-like, though with major differences. She argues that current psilocybin and MDMA trials should be studying sleep, since none that Huberman knows of focus on it.
- 02
Children and fire alarms
Children's slow-wave sleep is so deep that loud fire alarms often fail to wake them. Poe notes efforts to design alarms that say the child's name, which is quieter but more meaningful to them.
- 03
Estrogen after trauma
Female rats' locus coeruleus fails to quiet fully in REM during three phases of the estrous cycle and quiets properly only during the high-estrogen phase. Poe cites retrospective studies of women in emergency rooms: those who happened to be taking a pill containing estrogen were much less likely to develop PTSD after a trauma.
- 04
Meditation and REM-like theta
Theta activity, which occurs during learning and REM sleep, increases during transcendental meditation. Poe suggests meditation might mimic some REM functions, but it's unknown whether norepinephrine and serotonin switch off, which erasing the hippocampus requires.
- 05
Sleep inertia
Waking from deep slow-wave sleep causes grogginess. Poe doesn't use an alarm except for flights and recommends waking naturally when possible, while Huberman suggests timing alarms near the end of a 90-minute cycle.
OTHER RELEVANT
- 01
Pay back sleep debt with extra sleep
Poe says cognitive deficits build up with each night of sleep deprivation, and recovery requires actually sleeping more. That's also why the people in the 12-hour study slept 10–11 hours at first before settling at their natural amount.
- 02
Keep your bedtime consistent
Because the growth hormone pulse is tied to your circadian clock, regular bedtimes matter. Huberman says he's now keeping his bedtime within about ±30 minutes and reports better sleep scores and daytime vigor.
- 03
Go to bed calm, not anxious or wired
Going to sleep anxious or hyped up keeps the locus coeruleus active and can make sleep maladaptive. Poe suggests meditation, deep breathing, a warm bath or a comforting book, something neither too exciting nor too boring.
- 04
Use NSDR or yoga nidra for insomnia and middle-of-the-night waking
Relaxing the facial muscles, breathing with long exhales and doing body scans all push away from locus coeruleus activation and help you fall back asleep, though nothing replaces sleep itself. Poe notes insomnia feeds on itself: anxiety about not sleeping becomes the thing that keeps you awake.