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
