In his science fiction film Inception (2010), Christophe Nolan imagined his protagonist entering the dreams of others and even shaping their content. But what if this story wasn’t so far removed from real life?
Our research shows that it is possible to communicate with volunteers while they sleep, and even talk to them at certain key moments.
The scientific study of dreams
While we sometimes wake up with vivid memories of our nocturnal adventures, sometimes the impression of a dreamless night prevails.
Research shows that we remember an average of one to three dreams per week. However, not everyone is equal when it comes to dream recall. People who say they never dream make up about 2.7 to 6.5% of the population.
Often these people remembered their dreams when they were children. The share of people who say they have never dreamed in their entire lives is very low: 0.38%.
Whether people remember their dreams depends on many factors, such as gender (women are more likely to remember their dreams than men), a person’s interest in dreams, and the way dreams are collected (some may find it useful to keep track of them with a “ dream diary” or a recorder for example).
The personal and fleeting nature of dreams makes it difficult for scientists to record them. However, today, thanks to the knowledge acquired in the field of neuroscience, it is possible to classify a person’s alertness by analyzing his brain activity, muscle tone and eye movements.
Scientists can thus determine whether someone is sleeping and in which sleep stage he or she is: the beginning of sleep, light slow wave sleep, deep slow wave sleep or REM sleep (Rapid Eye Movement).
What this physiological data doesn’t tell us is whether a sleeper is dreaming (dreams can occur at all stages of sleep), let alone what he or she is dreaming about. Researchers do not have access to the dream experience as it occurs.
They are therefore forced to rely on the dreamer’s story upon awakening, without any guarantee that this story is true to what happened in the sleeper’s mind.
Furthermore, to understand what happens in the brain during dreaming – and what purpose this activity serves – we would need to be able to compare brain activity at times when dreams occur with those when they are absent. It is therefore imperative to determine exactly when dreams occur to advance the science of dreams.
To achieve this, it would be ideal to be able to communicate with sleepers. Impossible? Not for everyone; that’s where lucid dreamers come into the picture.
Lucid dreams
Most of us don’t realize we’ve been dreaming until we wake up. Lucid dreamers, on the other hand, have the unique ability to remain aware of the dreaming process during REM sleep, a sleep phase in which brain activity is closer to that of the waking phase.
Even more surprising, lucid dreamers can sometimes exercise partial control over the story of their dream. They can then fly away, make people appear or disappear, change the weather or transform themselves into animals. In short, the possibilities are endless.
Such lucid dreams can arise spontaneously or be developed through specific training. The existence of lucid dreaming has been known since ancient times, but for a long time it was considered esoteric and unworthy of scientific investigation.
Such views have changed thanks to a clever experiment set up in the 1980s by psychologist Keith Hearne and psychophysiologist Stephen Laberge. These two researchers wanted to prove that lucid dreamers were indeed asleep when they realized they were dreaming.
Starting from the observation that REM sleep is characterized by rapid eye movements while the eyes are closed (hence the name ‘Rapid Eye Movement sleep’), they asked themselves the following question: would it be possible to use this property to to ask the sleeper to send a ‘telegram’ from their dream to the world around them?
Hearne and Laberge recruited lucid dreamers to find out. They agreed before falling asleep about the telegram to be sent: the participants had to make specific eye movements, such as moving their gaze from left to right three times, as soon as they became aware that they were dreaming. And while they were objectively in REM sleep, the lucid dreamers did just that.
Thanks to the new communication code, researchers could now detect dream stages in real time. The work paved the way for many research projects in which lucid dreamers act as undercover agents in the dream world, carrying out missions (such as holding their breath in a dream) and communicating them to researchers using the eye code.
It is now possible to combine such experiments with brain imaging techniques to study the brain areas involved in lucid dreaming. This represents a huge step forward in the search for a better understanding of dreams and how they are formed.
In 2021, almost 40 years after Hearne and Laberge’s groundbreaking work, our research in collaboration with academics from around the world has taken us even further.
From fiction to reality: talking to the dreamer
We already knew that lucid dreamers could transmit information from their dreams. But can they also receive it? In other words, is it possible to talk to a lucid dreamer? To find out, we exposed a lucid dreamer to tactile stimuli while he slept. We also asked him closed questions such as “Do you like chocolate?”.
He could respond by smiling to indicate ‘Yes’ and by frowning to indicate ‘No’. Lucid dreamers were also verbally presented with simple mathematical equations. While they slept, they could give appropriate answers.
Of course, lucid dreamers didn’t always respond, far from it. But the fact that they sometimes did (18% of the time in our study) opened a channel of communication between researchers and dreamers.
However, lucid dreaming remains a rare phenomenon and even lucid dreamers are not lucid all the time or during REM sleep. Was the communication portal we had opened limited to only ‘lucid’ REM sleep? To find out, we did further research.
Expansion of the communication portal
To find out if we could communicate in the same way with every sleeper, regardless of their sleep stage, we conducted experiments with non-lucid dreaming volunteers without sleep disorders, as well as with people suffering from narcolepsy.
This disease, which causes involuntary sleep, sleep paralysis and early onset of the REM phase, is associated with an increased tendency to lucid dreaming.
In our final experiment, we presented participants with existing words (e.g., “pizza”) and others we made up (e.g., “ditza”) across all sleep stages. We asked them to smile or frown to indicate whether the word was made up or not. Not surprisingly, people with narcolepsy were able to respond when lucid in REM sleep, confirming our 2021 results.
Even more surprising, both groups of participants were also able to respond to our verbal stimuli in most sleep stages, even in the absence of lucid dreaming. The volunteers could respond intermittently, as if windows of connection to the outside world temporarily opened at certain precise moments.
We were even able to determine the composition of brain activity that was conducive to these moments of openness to the outside world. By analyzing it before the stimuli were presented, we could predict whether the sleepers would respond or not.
Why do such windows of connection with the outside world exist? We can put forward the hypothesis that the brain developed in a context that required a minimum of cognitive processing during sleep.
For example, we can imagine that our ancestors had to remain alert to external stimuli during their sleep, in case a predator approached. Likewise, we know that a mother’s brain responds preferentially to her baby’s crying during sleep.
Our results suggest that it is now possible to ‘talk’ to any sleeper, whatever stage of sleep he or she is in. By refining the brain markers that predict the moments of connection with the outside world, it should be possible to further optimize communication protocols. the future.
This breakthrough paves the way for a real-time dialogue with sleepers, giving researchers the chance to explore the mysteries of dreams as they happen. But as the line between science fiction and reality becomes thinner, rest assured: neuroscientists are still a long way from deciphering your wildest fantasies.
Basak Turker, Chercheuse postdoctoral, Institut du Cerveau (ICM) and Delphine Oudiette, Chercheure en neurosciences cognitives, Inserm
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