Picture the perfect morning after waking up. Your eyes open slowly, sunlight pours softly through the window, and you feel rested and refreshed. That feeling isn’t just because you slept the recommended 7–9 hours. It also depends on how deep and uninterrupted your sleep felt. And may be the key to that perception.
Neuroscientists at the IMT School for Advanced Studies in Lucca, Italy, say that particularly vivid and engaging dreams help people feel like they slept deeply and fully recovered. (IMT is an acronym for “Institutions, Markets, Technologies”).
In a new study published in PLOS Biology, the team found that detailed, vivid dreams — rather than leaving people feeling tired — give them a sense of restoration.
The most vivid narrative dreams typically happen during the rapid eye movement phase, or REM sleep, where the brain is almost as active as it is when awake. But for this study, the team examined the second stage of slow-wave sleep — NREM2. Neuroscientists say this so-called light-sleep stage makes up the largest share of a night’s sleep — about 50 percent — and it shows wide variation both in whether dreams occur and in how deep sleep feels.
Reminder: a full sleep cycle includes three stages of slow-wave sleep, or NREM phases (sleep onset, light sleep, and deep sleep), plus the REM phase. While the first NREM stage is important for physical recovery, the second stage is especially important for emotional health, creativity, and processing complex information.
What the study found
To investigate the disconnect between brain activity during NREM2 and how people perceive their rest, the scientists analyzed lab recordings of overnight sleep from 44 healthy adult volunteers of both sexes. The researchers measured the volunteers’ brain activity using high-density electroencephalography (EEG).
During the experiment, the team repeatedly woke participants from NREM2 and asked them to rate how deep their sleep felt and how sleepy they were. It turned out that volunteers reported feeling the deepest sleep and the most restored after vivid, meaningful dreams.
“In other words, not all mental activity during sleep is felt the same; the quality of the experience — especially its richness — likely matters. So dreams can change how a sleeping person interprets brain activity: the more engaging the dream feels, the deeper the sleep feels,” said Giulio Bernardi, the study’s lead author.
Even though the physiological need for sleep steadily decreased across the night, participants reported that their sleep felt deeper. That suggests dreams help maintain the sense of deep sleep even as biological sleep pressure falls. And even while the brain stays active, engaging dreams are closely tied to preserving a sense of detachment from the world — a defining feature of restorative sleep.
Dr. Bernardi says that understanding how dreams affect the feeling of deep sleep “opens new avenues for improving sleep health and mental wellbeing.”
So, diving into vivid dreams contributes to a sense of deep, restorative sleep. was probably right when he called dreams “the guardians of sleep.”
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