Vivid dreams trick your brain into thinking you slept well
Popular Science...
Picture your perfect morning wake-up. Your eyes flutter open, the sun is gently streaming in through the window, and you actually feel rested from the night before instead of groggy. That sensation of getting a really good night’s sleep comes from more than just the recommended seven to nine hours of shut eye. It’s also up to our perception of how deeply we slept without interruption. And dreams may be the key to that perception.
Our dreams—particularly the more vivid and immersive ones—could help us feel like our sleep was deeper and restorative. Instead of tiring us out, all of that dreaming may make us feel more rested, according to a study published today in the journal PLOS Biology.
Deep sleep is often thought of as the brain being more “switched off,” with slower brain waves, little activity, and no awareness of the outside world. In this school of thought, the deeper the sleep, the less active the brain.
By comparison, dreaming has been associated with Rapid Eye Movement (REM) sleep and partial awakenings of the brain during sleep. We also experience the REM stage-–marked by intense dreaming and brain activity similar to when we are awake—as relatively deep sleep.
To investigate this contradiction between our brain’s activity and how we perceive our level of restfulness, scientists analyzed overnight recordings from 44 healthy adults. The participants slept in a laboratory, while researchers measured their brain activity with high-density electroencephalography (EEG). In the experiment, the team repeatedly awakened the participants from non-REM sleep. They asked the participants to report their mental experiences just before waking up, and to rate perceived sleep depth and level of sleepiness.
The team found that the participants reported the deepest subjective sleep after more vivid and immersive dreams. By comparison, minimal or fragmentary sleep experiences, like a vague sense of being present somewhere without clearly understanding what was going on in a dream, were associated with the shallowest perceived sleep.
“In other words, not all mental activity during sleep feels the same: the quality of the experience, especially how immersive it is, appears to be crucial,” Giulio Bernardi, a study co-author and neuroscientist at IMT School for Advanced Studies Lucca in Italy, said in a statement. “This suggests that dreaming may reshape how brain activity is interpreted by the sleeper: the more immersive the dream, the deeper the sleep feels.”
Surprisingly, although physiological markers of sleep pressure steadily decreased throughout the night, participants reported feeling like their sleep was becoming deeper. This indicates that dream experiences may help sustain that feeling of deep sleep, even as the biological drive for sleep decreases. It’s possible that even as our brains are active, immersive dreams may help maintain a defining feature of restorative sleep—our sense of disconnection from the world.
“Understanding how dreams contribute to the feeling of deep sleep opens new perspectives on sleep health and mental well-being,” said Bernardi. “If dreams help sustain the feeling of deep sleep, then alterations in dreaming could partly explain why some people feel they sleep poorly even when standard objective sleep indices appear normal.”
Immersive dreams may help buffer changes in brain activity and help sustain the experience of being deeply asleep. In other words, neurologist Sigmund Freud may have been onto something when he said that dreams are the “guardians of sleep.”
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