Tonight, once you close your eyes in bed, something strange will occur to you: your mind will move from a standard thought to a dream, but it would be unimaginable to say when it happened. We imagine that the boundary between sleep and wakefulness is evident: once we are awake, we expect. When we sleep, we dream. Still, ours studyPublished in Cell Reports, we show that this range is more vulnerable than you’re thinking that. You can dream before you fall asleep, and plan your day after drifting off.
From thought to dream and every part in between
Think about what it means to get up. Right now, as you read these lines: the sounds reach you, the sunshine falls on you, the material touches your skin. You are anchored on the planet. Sleep is the alternative. You are still, cut off from the surface world and inhabited by experiences created from inside: dreams.
There is a time gap between the 2. We don’t go from one state to a different, like flipping a light-weight switch. This is A gradual transition In which mental activity slows down, muscles loosen up, respiration deepens. And the mind doesn’t stop working. It takes on other forms by generating thoughts concerning the day ahead or the day ahead, fleeting images, a number of pieces of music, fragments of dreams… researchers call it a half-awake, half-asleep state. “Hypnagogia”.
The problem is that these experiences are temporal and ever-changing, difficult to report and difficult to categorize. “What am I going to eat tomorrow?” How can we move forward? “I’m sitting on an underwater train”? Until now, researchers have tried to sort them into categories based on what they’re (“This sounds weird, it must be a dream”) or after they occur (“I exclude everything that happens during waking hours”). Conclusion: We knew that many experiences go through the mind through the onset of sleep, but without being sure which of them, nor when or how the brain produces them. This is strictly what we set out to know.
Letting the info speak
To get a transparent picture, we had to desert pre-defined categories and let the info speak. We recorded the brain activity of 103 participants while they took a nap within the lab, using electroencephalography, or EEG: Electrodes were placed across the scalp to capture neural signals and make it possible to differentiate wakefulness (fast alpha waves) from light sleep (slow theta and sigma waves), with the slowest waves called ultra-slow sleep. Spindle).
We interrupted them at intervals with a voice and asked a quite simple query: “What was going through your mind before the alarm went off?” We then asked them to rate their experience along 4 dimensions: how strange (and strange), how fluid and continuous (or, conversely, fragmented) and the way spontaneous it was (without voluntary control), in addition to their impression of being awake or asleep.
In total, we collected 375 experiments during sleep onset. Instead of deciding for ourselves what counts as a dream or a waking thought, we used a Machine Learning Algorithms to group these experiences into “states of mind” without specifying prematurely what they were presupposed to be.
By taking into consideration participants’ rankings on all 4 dimensions, the algorithm searched for groups of experiences that resembled one another—a bit like in search of “families” on a four-coordinate map. Typically: fragments of memory (“An image of my father came to mind”), peripheral thoughts (“I was hearing the sounds of the street”), dreamlike imagery (“I was seeing little strangers”), and deliberate reflection (“I was thinking about what I was going to do tomorrow”).
The next query naturally got here: At what time does each of those states occur between wakefulness and sleep?
Dreaming while awake, pondering while sleeping
This is where the outcomes get surprising. We expected a straightforward scenario: rational thoughts during wakefulness, strange imagery during sleep. And some patterns went in that direction: As people fell asleep faster, mental states related to surroundings and deliberate reflection became rarer.
But that is the guts of our findings: All 4 states appeared across the board – during wakefulness, sleep onset (stage N1), and in additional established sleep (stage N2). What goes through our mind doesn’t determine whether we’re awake or asleep.
In practice, some cases turned out to be, frankly, contradictory. One participant, who was wide awake (alpha waves on the EEG, an indication of wakefulness), reports: “Ants were crawling over me with crossword puzzles in the background.” Another participant sleeping in stage N2 (sudden large slow waves on the EEG recording, a classic marker of sleep) simply said: “I was thinking about work.” We dream before we sleep. We think while we sleep.
One point needs clarification: the brain doesn’t work the identical way during wakefulness and sleep. During sleep, it slows down, it becomes synchronized. So how can a dream-like experience occur in each wakefulness and sleep? To understand this, we zoomed in: shorter time windows to capture rapid changes in brain waves, 64 electrodes to exactly cover the cortex, and higher metrics than traditionally used brain signals.
We found brain signatures of mental states. Dreamlike imagery, for instance, was accompanied by poor communication between distant brain regions, as if these brain regions were unable to speak with one another. Key point: These signatures were the identical whether the person was awake or asleep. In other words, the mind can produce the identical form of mental experience whatever the state of alertness.
What about you? What goes through your mind once you sleep? These findings raise the next equally interesting questions: Are all people’s mental experiences the identical? In the identical order? And does it tell us anything about who we’re?
To discover, we designed Flowing mindan roughly twenty-minute online questionnaire that explores your mental experiences during sleep onset. About 5,000 people across five continents have already participated. The goal is to discover sleep onset profiles within the population and see in the event that they depend upon age, gender, and culture, but in addition in the event that they are related to characteristics corresponding to creativity, anxiety, mental imagery, or sleep quality.
At the tip of the questionnaire, you discover your sleep onset profile and might compare yourself to others. Participate here!
What we’re attempting to do is deeply understand what the brain produces on this “in-between” zone, and what it says about us. So tonight, as soon as you shut your eyes, you’ll walk through this strange corridor once more. Pay attention to the moment and what is going on through your mind before you allow…