REM sleep: what the dream phase does for memory and emotions
REM sleep is far more than the time when you dream. This phase is crucial for how your brain consolidates what you've learned and processes emotional experiences — and it's surprisingly easy to disrupt.
What REM sleep is — and when it occurs
REM stands for Rapid Eye Movement — the rapid eye movements that characterise this phase. Your brain is almost as active as when you're awake, yet your body is largely paralysed. This is a protective function: it prevents you from physically acting out your dreams.
REM phases are not evenly distributed throughout the night. Deep sleep dominates in the first half of the night; REM sleep accumulates mainly in the second half. A typical night contains four to six sleep cycles of around 90 minutes each, and the REM portions grow longer as the night progresses. People who regularly wake too early or fall asleep too late disproportionately cut into their REM time.
REM sleep and memory
During REM sleep, the brain consolidates declarative memory content — facts, events, newly learned material — and links it to existing knowledge. The hippocampus "replays" the day's events and transfers them to the neocortex for long-term storage. Robert Stickgold (Nature, 2005) called this process sleep-dependent memory consolidation and showed that learning performance is significantly better retrievable after good sleep than after sleep deprivation.
REM sleep is particularly relevant for procedural learning — practising skills that require patterns and sequences. Musicians learning a new piece, or athletes training movement sequences, demonstrably benefit from sufficient REM sleep on the night after training. Walker and Stickgold (Neuron, 2004) described this phenomenon as "offline processing" — the brain keeps working while you sleep.
REM sleep and emotions
REM sleep has a second, less well-known function: it acts as a kind of nightly therapy session for emotional experiences. Matthew Walker and Els van der Helm (Psychological Bulletin, 2009) described how REM sleep separates emotional memories from their affective charge — the experience remains retrievable, but loses its emotional intensity. People who sleep well after a distressing event often view it more clearly the next morning.
When REM sleep is disrupted — by alcohol, certain antidepressants or chronic sleep deprivation — this processing does not take place. The amygdala, the brain's alarm centre, then reacts more intensely to stressors, and the connection to the rational prefrontal cortex is weakened. This explains why sleep deprivation promotes emotional overreactions and why REM sleep disorders are closely associated with depression and anxiety disorders.
How much REM sleep do you need?
Adults typically spend 20 to 25 percent of their sleep time in REM sleep. With 8 hours of sleep, that is roughly 90 to 120 minutes. There is no official minimum recommendation specifically for REM sleep, because it is inseparably linked to total sleep duration: people who sleep enough and regularly generally get sufficient REM.
Sleep trackers such as Whoop or the Oura Ring measure REM phases via heart rate and movement patterns. These estimates are useful approximations, but not exact measurements — that is only possible in a sleep laboratory using polysomnography (EEG). Nevertheless, trackers can help identify trends: if your REM proportion stays consistently low over several weeks, it is worth looking into the causes.
What disrupts REM sleep — and how to protect it
Alcohol is one of the strongest suppressors of REM sleep. Even moderate amounts in the hours before bedtime shift sleep towards more deep sleep in the first half of the night — at the expense of REM sleep in the second half. Many sleeping medications (in particular benzodiazepines and Z-drugs) also suppress REM sleep, as do some antidepressants.
The good news: REM sleep can be protected by ensuring overall sleep duration. Anyone who sleeps long enough and improves both falling and staying asleep automatically gives their brain more time for REM. Regular sleep times, a cool bedroom and avoiding alcohol in the last three hours before bed are the most effective levers.
How the YUTHI app helps you
If you use a sleep tracker, you can put its REM data in context with the YUTHI app: Is your REM share in the normal range? Does it change on days when you drink alcohol or after late-evening exercise? By logging regularly, you spot patterns faster. In the magazine articles on deep sleep, sleep temperature, and alcohol & sleep you'll find additional information on how to improve your overall sleep architecture.
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Sources
- Walker MP, Stickgold R. Sleep-dependent learning and memory consolidation. Neuron. 2004;44(1):121–133.
- Stickgold R. Sleep-dependent memory consolidation. Nature. 2005;437(7063):1272–1278.
- Walker MP, van der Helm E. Overnight therapy? The role of sleep in emotional brain processing. Psychol Bull. 2009;135(5):731–748.
- Tononi G, Cirelli C. Sleep and the price of plasticity: from synaptic and cellular homeostasis to memory consolidation and integration. Neuron. 2014;81(1):12–34.