Is Our Brain Ever Fully Asleep? It May Stay Awake Even as We Dream
Each night, our brains cycle through hours of activity that remain surprisingly mysterious. Even though much of that time is spent dreaming, scientists still don’t fully understand what the brain is doing while we sleep.
Now, researchers have taken a big step toward solving that mystery. In the largest project of its kind, an international team created DREAM — the Dream EEG and Mentation database, an open-access collection of brain recordings linked to dream reports. Electroencephalography (EEG) tracks tiny electrical pulses in the brain.
Their findings, published in Nature Communications, reveal that dreams can arise in any stage of sleep, not just during the rapid-eye-movement (REM) phase long thought to be their exclusive home. And when people dream during deeper, non-REM (NREM) sleep — the calmer, slow-wave stages — their brain activity resembles that of someone awake, suggesting the dreaming brain may be “partly awake” even when the body isn’t.
Dreams Don’t Only Happen During REM Sleep
For decades, REM sleep, marked by vivid imagery, rapid eye movements, and temporary paralysis, was believed to be the main stage of dreaming. But the DREAM data tell a different story.
Across thousands of awakenings, participants reported dreams after about 85 percent of REM sleep and roughly 40 to 60 percent of NREM sleep. As sleep deepened, dream frequency decreased but never disappeared entirely. Even in the slowest stages, some people described thoughts or emotions, conscious experiences occurring while they appeared sound asleep.
When researchers examined brain waves before each awakening, they found that NREM dreams showed faster, smaller oscillations, a pattern typical of quiet wakefulness. In deep sleep, the brain briefly shifted toward a more “awake-like” state — as if parts of the mind stirred while the rest stayed still.
Read More: Difficulty Reaching REM Sleep May Signal Early Warning for Alzheimer’s
AI Helps Scientists Read Dreams
The DREAM database combines 2,643 awakenings from 505 volunteers across 20 studies in 13 countries, merging decades of research into one platform. Each awakening was labeled as an “experience” (a dream), an “experience without recall” — sometimes called a “white dream” — or “no experience.”
Using both EEG and magnetoencephalography (MEG) — which measures magnetic fields from brain activity — the team compared the final 30 seconds of brain data before each awakening with the dream report that followed.
They then trained artificial-intelligence models to tell whether a person had been dreaming. In deep NREM sleep, simpler brain-wave features gave moderate accuracy; in REM sleep, more complex patterns worked better. The results show that dreaming leaves a measurable neural signature, a pattern that could one day let scientists detect dreams without waking sleepers.
As co-author Giulio Bernardi said in a press release, “The work presented in the article, coordinated by Monash University (Australia), resulted from the efforts of 53 authors from 37 institutions across 13 countries, and represents a decisive step in the scientific exploration of human consciousness by bringing together and making decades of dream research available in one place.”
Why Studying Dreams Can Unlock the Secrets of Sleep
Dreams offer a glimpse into consciousness during sleep, moments when the brain creates experiences without outside input. Because they occur in both REM and NREM stages, they help scientists trace how awareness fades and reappears through the night.
By standardizing how brain and dream data are collected, the DREAM project gives researchers a shared foundation to study what the mind is doing while we sleep. As the database grows, scientists hope it will reveal why we dream, why some people recall them more vividly than others, and how the brain balances rest with awareness.
Read More: Yes, You Can Control Your Dreams: The Strange Science of Lucid Dreaming
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