REM Sleep and Memory: What Happens While You Dream

Our guide to sleep stages covers how much of each stage you need. This one goes deeper on just one stage, REM, and the specific job it does that no other stage seems to do: sorting, strengthening, and reshaping memory while you dream.

Two Sleep Stages, Two Different Jobs

A comprehensive 2013 review of sleep and memory research lays out a division of labor between sleep stages. Slow-wave (deep) sleep, concentrated earlier in the night, plays the bigger role in consolidating declarative memory, facts, names, what happened today. REM sleep, which becomes more concentrated in the later sleep cycles toward morning, is instead tied specifically to procedural memory, the kind involved in learning a physical or mental skill, and to emotional memory processing.

The Sleep to Forget, Sleep to Remember Idea

One of the more striking findings the review discusses is what researchers call sleep to forget, sleep to remember: REM sleep following an emotionally charged experience appears to strengthen the factual content of that memory while simultaneously reducing its emotional intensity. It’s a plausible explanation for the common experience of a stressful day feeling far less raw after a full night’s sleep, even though you remember exactly what happened.

The Honest Caveat

The review is careful to flag a real limitation in this research: REM-deprivation experiments in humans have been criticized because waking someone up specifically during REM repeatedly is itself stressful, which could confound the results. It’s also not the case that REM is required for all memory, some declarative memory tasks show no REM dependence at all. The fair summary is that REM plays a specific, real role in procedural and emotional memory processing, not that it’s the single stage responsible for memory in general.

How to Protect Your REM Sleep

• Don’t cut your sleep short at the wrong end. REM sleep is concentrated in the later sleep cycles, so shaving an hour off the morning removes disproportionately more REM than the same hour removed at bedtime.
• Go easy on alcohol before bed. Alcohol is well documented to suppress REM sleep, particularly in the first half of the night.
• Keep a consistent wake time. A regular schedule protects the full architecture of your sleep cycles, REM included, rather than truncating the later cycles unpredictably.
• If falling asleep itself is the problem, our guide to falling asleep fast covers techniques that get you into the full cycle sooner.

If a short daytime rest is more realistic for your schedule than fixing nighttime sleep, see our guide to the science of napping for what a nap can and can’t substitute for.

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