Dreams may make sleep feel deeper, even when the brain is more active
New research suggests that vivid dreaming helps sustain the subjective feeling of deep sleep across the night, offering a new perspective on what shapes our perception of sleep depth.
IMT School for Advanced Studies Lucca
image:
Illustration of the research setting where the study was conducted.
view moreCredit: Valentina Elce
The feeling of having had “a good night’s sleep” lies not only in how much we slept, but also in the subjective impression of having slept deeply and without interruption. But what constitutes the neural base of this perception is not very well understood.
Now, a new study by researchers at the IMT School for Advanced Studies Lucca, appeared in Plos Biology, suggests that the dreams, especially the most vivid and immersive ones, rather than disrupting sleep, could help it feel deeper and restoring.
For years, we thought deep sleep meant a "switched off" brain: slow brain waves, little activity, no awareness. In this view, the deeper the sleep, the less active the brain. On the other hand, dreaming has been instead associated with Rapid Eye Movement (REM) sleep and it is acknowledged to reflect partial “awakenings” of the brain. Yet, surprisingly, this stage marked by intense dreaming and wake-like brain activity is also commonly experienced as a relatively deep sleep.
To investigate this paradox, researchers analyzed 196 overnight recordings from 44 healthy adults who slept in a laboratory while their brain activity was measured with high-density electroencephalography (EEG). The data were collected in a larger study supported by a European Research Council (ERC) Starting Grant investigating how various kinds of sensory stimulations impact on the subjective experience of sleep.
Dreaming changes how brain activity relates to sleep depth
Across four laboratory nights per participant, the researchers collected more than 1,000 awakenings with corresponding reports, creating one of the largest datasets linking brain activity, dream experience, and subjective sleep perception. For the experiment, participants were awakened repeatedly from non-REM sleep, a stage characterized by broad variability in both subjective sleep depth and dreaming, and asked to report their mental experiences just before awakening, and to rate perceived sleep depth and subjective sleepiness.
The results revealed that the deepest subjective sleep was reported not only when participants had no conscious experience, but also after vivid and immersive dreams. By contrast, minimal or fragmentary experiences, such as a vague sense of presence without clear dream content, 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” explains Giulio Bernardi, professor in neuroscience at the IMT School and senior author of the study. “This suggests that dreaming may reshape how brain activity is interpreted by the sleeper: the more immersive the dream, the deeper the sleep feels”.
The authors also found another striking element: although physiological markers of sleep pressure steadily decreased across the night, participants paradoxically reported feeling that their sleep was becoming deeper. This subjective deepening closely tracked a rise in the immersiveness of dreams, suggesting that dream experiences may help sustain the feeling of deep sleep even as the biological drive for sleep wanes. Indeed, immersive dreams may help maintain our sense of disconnection from the external world, a defining feature of restorative sleep, even as parts of the brain become more active.
Dreams as “guardians of sleep”
“Understanding how dreams contribute to the feeling of deep sleep opens new perspectives on sleep health and mental well-being,” says 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. Rather than being merely a by-product of sleep, immersive dreams may help buffer fluctuations in brain activity and sustain the subjective experience of being deeply asleep”. This idea echoes a long-standing hypothesis in sleep research - and even in classical psychoanalysis - that dreams may act as “guardians of sleep.”
###
The study was conducted within a broader collaboration between the IMT School, Scuola Superiore Sant’Anna in Pisa, and Fondazione Gabriele Monasterio, where a new sleep laboratory has been established to bring together complementary neuroscientific and medical perspectives. The laboratory provides a multidisciplinary framework for investigating sleep and the sleep–wake cycle from multiple angles, allowing researchers to more comprehensively explore the interaction between brain activity and bodily physiology. The present findings represent an important first step in this direction and lay the groundwork for future studies examining how brain–body dynamics shape sleep in both physiological and pathological conditions.
Journal
PLOS Biology
Method of Research
Observational study
Subject of Research
People
Article Title
Immersive NREM2 dreaming preserves subjective sleep depth against declining sleep pressure
Article Publication Date
24-Mar-2026
Vivid dreaming makes sleep feel deeper
Perceived sleep depth is greater after having vivid immersive dreams
PLOS
image:
An image depicting the experimental setup (the image shows on the left, a sleeping participant wearing the EEG cap and, on the right, the recorded EEG, EOG, EMG, and ECG signals during NREM2 sleep).
view moreCredit: Valentina Elce (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)
Researchers led by Guilio Bernardi at the IMT School for Advanced Studies Lucca in Italy have discovered a key relationship between dreaming and the feeling of having had a good night’s sleep. Published in PLOS Biology on March 24th, the study shows that the feeling of deep sleep is not determined solely by slow-wave brain activity. Rather, immersive dreaming that comes with increases in wake-like brain activity leads to a greater feeling of deep sleep.
Why is it that sometimes we sleep 8 hours and don’t feel rested, while other times we feel like we had a great night’s sleep after only 5 hours? Research has shown that our feeling of deep sleep is related to a shift from high- to low-frequency brain waves, which is thought to drive unconsciousness. At the same time, other reports indicate that dream (REM) sleep is also perceived as deep, despite its wake-like brain waves. To better characterize the effects of dream sleep on perceived sleep depth, the researchers analyzed EEG recordings from 44 adults who were repeatedly awoken during non-REM sleep over the course of 4 nights.
Analysis showed that shifts from faster to slower waves were indeed associated with a feeling of deep sleep. However, this relationship weakened when participants reported having had a dream, even if they could not remember the content. Perceived sleep depth was thus higher after dreaming even though this state is associated with wake-like brain activity. Specifically, vivid, bizarre, and emotionally intense dreams were all associated with subjectively deeper sleep, while abstract, reflective thought-like dreams with meta-awareness were related to more shallow feeling sleep.
These findings are contrary to the longstanding view that the feeling of deep sleep is governed solely by slow brain waves and the depth of unconsciousness, and suggest that perceptually immersive dreaming is what allows us to feel well rested – even if we can’t remember what we dreamed.
The authors add, “We already know that dreaming extends beyond REM sleep and occupies a large portion of the night, yet its function remains unclear. Our study suggests that dreams may help shape how we experience sleep by immersing us in an internal world that keeps us disconnected from the external environment.”
“Understanding how dreams contribute to the feeling of deep sleep opens new perspectives on sleep health and mental well-being. Alterations in dreaming — for example, a reduction in the richness or frequency of dreams — could influence how people perceive their sleep depth or duration, and may contribute to dissatisfaction with sleep quality.”
“This kind of research is extraordinarily demanding. Serial awakening studies require waking participants repeatedly across multiple nights and collecting detailed reports each time. It was only possible thanks to the dedication, resilience, and coordination of an exceptional team of researchers.”
In your coverage, please use this URL to provide access to the freely available paper in PLOS Biology: https://plos.io/4u6AsUi
Citation: Michalak A, Marzoli D, Pietrogiacomi F, Bergamo D, Elce V, Pedreschi B, et al. (2026) Immersive NREM2 dreaming preserves subjective sleep depth against declining sleep pressure. PLoS Biol 24(3): e3003683. https://doi.org/10.1371/journal.pbio.3003683
Author countries: Italy
Funding: see manuscript
Journal
PLOS Biology
Method of Research
Experimental study
Subject of Research
People
