AI-generated image for illustrative purposes. Credit: ZME Science.

Tonight, as you drift toward sleep, your mind may begin to dream before your brain has officially crossed into sleep.

You may still be awake by the measures doctors use: your brain waves may show wakefulness, your muscles may still hold tone, and the world around you may still reach your ears. Yet your personal perceptions may resemble something more dreamlike.

In a new study published in Cell Reports, researchers at the Paris Brain Institute suggest that dreaming is not a switch that flips only after sleep begins. By waking people repeatedly as they nodded off and asking what had just crossed their minds, the team found that dreamlike, bizarre mental states can appear during wakefulness, while deliberate, ordinary thoughts can continue after people have entered light sleep.

The findings challenge a familiar picture of the night: first we think, then we sleep, then we dream. Instead, the researchers argue, the mind moves through a shifting landscape in which waking thought and dreaming overlap.

The Strange Corridor Before Sleep

Scientists call the half-awake, half-asleep state at sleep onset hypnagogia. It is the time when a stray thought can become an image, when a sound in the room can fold into a scene, and when a practical question — such as what should I do tomorrow? — can turn into something stranger.

“Yet this is far from obvious. Being awake is not synonymous with being attentive, fully aware of one’s surroundings, or able to act and think rationally,” said Delphine Oudiette, a sleep researcher at Inserm and co-leader of the Paris Brain Institute’s DreamTeam. 

“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. What remained to be determined was whether the content of our thoughts also varies independently of our state of vigilance.”

Researchers have increasingly found that sleep is not a sealed chamber. Earlier work has shown that parts of the brain can show sleep-like activity during wakefulness, and that sleeping people can sometimes process the outside world. In 2021, researchers even reported two-way communication with lucid dreamers during REM sleep.

Sleep onset has also attracted attention from those looking to be more creative. Thomas Edison is said to have napped while holding an object so that, as he drifted off, it would fall and make a loud noise to wake him. This allowed him to catch fresh ideas in hypnagogia, something that Salvador Dali famously did as well. An earlier 2021 study from Oudiette and colleagues found that a brief stay in the earliest stage of sleep, N1, could boost insight on a problem-solving task.

The new study used a similar doorway into sleep, but for a different reason.  

“Sleep onset allows us to capture, within a very short time span, fluctuations in our state of vigilance, from wakefulness to sleep, and to observe the mental experiences associated with them,” said Nicolas Decat, a PhD student at the Paris Brain Institute and first author of the study. 

“As we drift toward sleep, sensations, visions, and snippets of speech unfold — what are commonly called hypnagogic experiences. Tracing the evolution from ordinary thought to dream-like narrative can help us understand how a dream emerges.”

A Nap, a Bottle and 375 Reports

The team recruited people who could nap easily in a laboratory. In all, 103 healthy volunteers began the experiment. After exclusions, the main analysis included 92 participants.

They sat back in a dark, quiet room, wearing a 64-channel EEG cap to record brain activity. In one resting session, they held a small bottle. When their hand relaxed, the bottle fell and made a noise, waking them. In another session, alarms interrupted them at set times.

Each time, the researchers asked them what had gone through their minds in the previous 10 seconds.

Participants then rated the experience on four scales: how bizarre it was, how fluid or fragmented it felt, how spontaneous it seemed, and how awake they felt. The researchers collected 485 reports, kept 420 after exclusions, and focused on 375 reports that contained a mental experience.

Rather than decide in advance which reports counted as dreams, the team used a clustering algorithm. It sorted the reports into groups based on the participants’ own ratings.

“This data-driven approach was essential for us, because in research, there is no consensus on what hypnagogic experiences actually are. It was important not to bias this exploration with our own definitions or beliefs,” Decat said in the Paris Brain Institute press release.

The algorithm found four kinds of mental states.

One was fleeting and fragmented: “An image of my dad crossed my mind.” Another stayed tied to the environment: “I was listening to the street sounds.” A third was bizarre and dreamlike: “I saw images of small aliens.” A fourth involved deliberate planning: “I was thinking about what I would do tomorrow.”

Most participants who gave more than one report moved through more than one state, the study found. 

Dreaming While Awake

The surprise came when the researchers matched those reports to the EEG.

The team classified the brain state before each interruption as wakefulness, N1 sleep or N2 sleep. Wakefulness is not just a person’s impression of being awake; it has recognizable electrical features. N2 sleep, a deeper light-sleep stage than N1, has its own markers, including K-complexes and sleep spindles.

The researchers expected ordinary thought to cluster in wakefulness and dreamlike imagery to appear after sleep began. The data did not obey that script.

Dreamlike reports appeared during EEG-confirmed wakefulness. Deliberate, practical thoughts appeared during EEG-confirmed sleep. In the paper’s stage-by-stage analysis, the “alert” state did not appear in the small N2 sample, but the broader pattern remained: mental content did not line up neatly with sleep stage.

“This is the major finding of our study. The mental states traditionally associated with dreaming can arise just as well when we are asleep as when we are awake. In other words, the content of our thoughts does not follow the boundaries between waking and sleep! One of our participants, while awake, reported seeing ants crawling on her body against a backdrop of crossword puzzles. Conversely, another participant mentally went through his schedule for the next day while he was fully asleep,” Decat said.

The alert, environment-focused state was more common during wakefulness. Fleeting and bizarre content tended to increase during N1 sleep. But the categories overlapped.

The Brain Signature of a Strange Thought

The researchers then looked for brain patterns tied to the four mental states, independent of whether a participant was awake or asleep.

The clearest signal came from the bizarre, dreamlike state. It showed reduced long-range connectivity, especially between frontal regions, which help organize attention and control, and occipital regions, which process visual information. In plain terms, distant parts of the brain seemed less synchronized during these dreamlike moments.

“This signature may well be the correlate of what we feel in such a state: lucid reasoning is overtaken by a whirlwind of vivid sensations characteristic of dreams,” Decat said.

The finding fits with a broader view of dreaming as a state in which perception-like imagery can run with less executive supervision. It also supports the idea that brain activity during the transition to sleep changes in patches, not all at once.

Why This Could Matter for Insomnia

Some people with insomnia say they barely slept, even when sleep-lab recordings show that they did. This mismatch is often called paradoxical insomnia or sleep-state misperception. Reviews describe it as a discrepancy between subjective and objective measures of sleep, and it remains difficult to diagnose and treat.

The Paris team suggests that part of the problem may lie in the categories clinicians use. Standard sleep scoring captures brain stages, but not always the patient’s lived experience. A person may be “asleep” by the EEG but still locked into a mental state that feels alert, effortful or tied to the outside world.

“These criteria are probably inadequate. Our study proposes a new one — mental content — which may be better aligned with what these patients actually experience. Through this lens, some of them may spend an unusually long time in an alert state (C2), hyperconnected to the outside world, or, conversely, very little time in a dream-like state (C3), blurring the line between their waking and sleeping lives,” Oudiette said. 

“Beyond giving patients’ reports the weight they deserve, this approach paves the way to identifying objective markers of insomnia.”

That is still a hypothesis. The study tested healthy volunteers, not insomnia patients. But it points toward a future in which sleep medicine may measure not only how the brain moves through stages, but how the mind moves through experience.

For now, the finding leaves us with a simple but unsettling thought. The dream may not begin when sleep begins. It may arrive earlier while we still think we are awake.