Most people assume dreaming is something exclusive to sleep; however, a new study from the Paris Brain Institute suggests otherwise.
The study found that the strange, shifting mental experiences we usually associate with dreaming can also occur while we are awake. These episodes leave a measurable trace in the brain. The results, published in Cell Reports, challenge the common idea that dreaming and waking thought are completely separate experiences.
“Being awake is not synonymous with being attentive, fully aware of one’s surroundings, or able to act and think rationally,” said Delphine Oudiette, co-leader of the institute’s DreamTeam and senior author of the study. “We now know that there is a continuum between wakefulness and sleep, with intermediate states such as mind-wandering or mind-blanking, during which certain regions of the brain may be asleep.”
at the Edge of Sleep
To investigate how the brain transitions from wakefulness to sleep, the researchers worked with 92 people who often take naps and could describe their thoughts when prompted. The experiment was based on a method used by Thomas Edison, who would fall asleep while holding a heavy object. When he drifted off, the object would fall and wake him up, allowing him to recall what he was thinking at the edge of sleep.
In this study, participants held a bottle as they became drowsy. If the bottle dropped or an alarm sounded, they were asked to describe what they had been thinking about in the last ten seconds. They also rated their experiences based on how strange, changeable, spontaneous, and awake they felt. Throughout the process, the researchers recorded their brain activity using an EEG. The researchers then used a clustering algorithm to group the mental experiences based on the data. This allowed the team to identify patterns in participants’ reports without imposing predefined categories.
Four Separate Mental States
The analysis revealed four distinct types of mental states, rather than the two categories people usually expect (awake and asleep).
One type consisted of quick, involuntary flashes of images or memories that seemed to come out of nowhere. Another was grounded in the outside world, with people noticing sounds or staying tuned in to their surroundings. A third was filled with strange, dream-like experiences, such as seeing tiny aliens or feeling ants crawling on the skin, with scenes shifting rapidly. The last type focused on logical, focused thinking, such as planning or mentally running through a schedule.
All four types of mental states were found at every stage the researchers measured, including when participants were fully awake, just falling asleep, or in light sleep. This means that dream-like thoughts can happen while awake, and logical thinking can occur during sleep.
One participant, who was fully awake, said she saw ants crawling over her body with crossword puzzles in the background. Another participant, who was asleep by all measures, spent that same time mentally planning the next day’s schedule.
“The mental states traditionally associated with dreaming can arise just as well when we are asleep as when we are awake,” said lead author Nicolas Decat, a PhD student at the Paris Brain Institute. “The content of our thoughts does not follow the boundaries between waking and sleep.”
A Distinct Brain Pattern
The researchers also found a specific pattern in the brain linked to dream-like experiences. EEG data showed that the connection between the front and back parts of the brain, which are important for logical thinking and visual processing, became weaker during these states. When this connection is reduced, the brain seems less able to organize thoughts logically.
A Tool for Insomnia Diagnosis
These results could help improve the diagnosis of some sleep disorders. For example, people with paradoxical insomnia often say they feel awake all night, even when sleep tests show they were asleep. Traditional methods typically rely on brainwave patterns, which do not always align with patients’ subjective experience.
Oudiette said the study suggests using mental content as a new way to diagnose insomnia. This approach may more closely match what patients actually experience each night and could eventually help identify objective markers of the condition.
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.