Many people’s idea of a good night’s sleep involves a quiet brain with slow waves, low awareness, and few interruptions. Instead, a new study from the IMT School for Advanced Studies Lucca finds that vivid, immersive dreams can actually make sleep feel deeper, even when brain activity is higher.
The findings, published in PLOS Biology, provide a new perspective on what makes sleep feel deep and restorative. They also raise questions about why some people feel unrested even after what they perceive as a good night of sleep.
Measuring Perceived Sleep Depth
Scientists usually define deep sleep by slow brain waves, low cortical activity, and minimal conscious experience. In contrast, dreams most often occur during REM sleep, a stage marked by increased brain activity and vivid mental imagery. Despite this, many people describe REM sleep as feeling deep, even though the brain is more active during this stage.
Researchers conducted a study of 44 healthy adults who slept in a lab while their brain activity was measured with high-density electroencephalography (EEG). These results were recorded over four nights per participant. The team analyzed 196 overnight recordings and collected more than 1,000 reports of participants awakening. This created one of the largest datasets connecting brain activity, dream experiences, and subjective sleep perception.
Participants woke repeatedly from NREM2 sleep, a stage that accounts for about half of total sleep time and shows wide variation in dream frequency and perceived sleep depth. Each time a participant woke up, they described their mental experiences and rated how deeply they felt they had been sleeping.
Dreams Effect on Sleep Perception
The results revealed a clear, but surprising pattern. Participants said they felt the deepest sleep not just after dreamless unconsciousness, but also after vivid, immersive dreams.
“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,” said 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.”
As the night went on, biological markers of sleep pressure decreased, but participants still reported their sleep felt deeper. This sense of deeper sleep matched an increase in the immersive quality of their dreams. This suggests that vivid dreams may help sustain the feeling of deep sleep, even as the body’s need for sleep decreases.
Implications Beyond the Lab
“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,” Bernardi said. “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 connects to a long-standing hypothesis in sleep research that dreams may protect sleep by shielding the sleeper from disruptions, rather than just reflecting what is happening in the brain. These findings may help explain why some people feel tired even when their sleep appears normal by standard measures. If immersive dreams help people feel that their sleep is deep, then changes in dream quality, even without changes in sleep duration, could be important.
It is unclear whether improving dream quality could help people who struggle with sleep feel more rested. However, the study suggests that the nature of our dreams may be just as important as standard sleep metrics such as how long or how deeply we sleep.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.