(SeaPRwire) –   In the transitional space between falling asleep and waking up, your brain cycles through countless states. Using an electroencephalogram (EEG)—a tool that records the brain’s electrical activity—scientists and doctors can distinguish between these stages. However, the exact role each stage plays isn’t fully understood. Sleep reduces tiredness, helps the brain process daily events, and seems to support memory and learning. But which stage is responsible for which function? Finding the answer could unlock ways to achieve higher-quality sleep.

To gain a better understanding, researchers carry out serial awakening experiments—lab studies where they wake sleeping participants multiple times throughout the night and ask them to complete surveys. (If that sounds like your worst nightmare, be grateful to the people volunteering for science.) A recent study in the journal PLOS Biology centers on awakenings during non-rapid-eye-movement sleep stage 2 (NREM2 for short), which typically accounts for roughly half of our total sleep time. The team made an interesting discovery: When participants were woken from immersive dreams—whose EEG patterns closely resemble those of wakefulness—they still reported feeling they’d slept deeply. The researchers hypothesize this implies that vivid dreams in this sleep phase might contribute to the perception of having slept deeply. 

What is the purpose of dreaming? 

Dreaming is so universal that it’s surprising scientists still don’t know why we do it. One method for studying dreams involves modifying them—by playing specific sounds to sleepers or waking them up and letting them fall back asleep—and then observing if these changes impact their subsequent feelings.

“We try to modulate brain activity, and we try to have an effect on how subjects feel subjectively, in terms of sleep depth and what they experience during sleep,” says Dr. Giulio Bernardi, a professor at IMT School for Advanced Studies Lucca in Italy and an author of the new paper. 

In this new study, Bernardi and his team examined NREM2 sleep, a phase that encompasses various states: immersive dreams, simple dreams, and periods with no dreaming at all. The researchers woke 44 participants during NREM2 and asked them to describe their thoughts, including whether they’d been dreaming. Sometimes participants had dreamed but couldn’t recall any details—this is known as a “white dream.” For those who remembered their dreams, they rated factors like vividness and immersiveness, and also how deeply they felt they’d been sleeping. 

Participants reported the deepest subjective sleep most often when their EEG showed they were deeply unconscious, with the electrical patterns associated with consciousness absent. 

However, participants also reported feeling deeply asleep when they’d had immersive dreams—even though their EEG patterns resembled those of a conscious state. 

“The brain can become more active, more awake, and still we can feel that we are deeply asleep if we are dreaming,” says Bernardi. 

What this finding means remains unclear

Does dreaming determine whether a night’s sleep is restless or satisfying? This study can’t answer that, as it doesn’t look at morning restfulness. Because participants were awakened so frequently, it’s challenging to separate the effect of dreaming from the impact of repeated awakenings on their perceptions of sleep.

However, the study does indicate that the connection between dreams and sleep depth is a topic that deserves more investigation.

Karen Konkoly, a dreaming researcher at the University of Cambridge in the U.K. who wasn’t part of this study, has taken part in a similar experiment. “It was fascinating to observe my mind at different times of night and realize how often I actually didn’t feel like I’d been fully asleep,” she wrote in an email. 

“So to me, the best way to tell that I was in fact deeply asleep is when I was awoken from an immersive dream. I knew I was asleep because I was dreaming. That is my best intuition explaining this finding, that it’s difficult to tell how deeply asleep one is, and an immersive dream is one clear way to answer that question.”  

Bernardi believes there’s more to the story. “While dreaming does indicate sleep, it does not necessarily imply ‘deep’ sleep per se,” he wrote in an email. “What I find particularly telling in our work is that participants sometimes reported having been deeply asleep even when they could not recall any specific dream content; only a general impression of having been in a rich or immersive state.”

He hypothesizes that this feeling of deep sleep might stem from a sense of being disconnected from the outside world. This disconnection can come from being fully unconscious or from a dream so immersive that external reality doesn’t seep in.

The study serves as a reminder that sleep is more than just being unconscious. Perceptions play a strong role: For example, many people who say they have insomnia are actually asleep for most of the night. In these cases, their perception of having slept is distorted. 

However, some dreams can feel overly real. Those who experience “epic dreaming” report dreaming all night long, often engaging in repetitive tasks with tedious detail. 

“In the end, when they wake up in the morning, they are super-tired, as if they worked for the whole night,” says Bernardi. “So dreams probably have to stay in the right range, let’s say, of immersivity—otherwise they become negative for our sleep.”