Still foggy, you wake up from a dream. Isn’t he running away from you already? “The dream is the phenomenon that we only observe during its absence. The verb to dream has almost no present ”, observed Paul Valéry. Science, however, is on the way to make the writer lie. Researchers have managed to interact in real time with sleeping dreamers. The experimenters asked them specific questions; and, in return, they gave them correct answers, in almost one in five cases. A small proportion? “It is much larger than if these good answers were the result of chance”, underlines Delphine Oudiette, researcher at Inserm and at the Brain Institute in Paris. This neuroscientist co-signs this feat in review Current biology, February 18.
All the experiments were carried out on “lucid dreamers”, during the so-called “paradoxical” sleep phase: the volunteers were aware of being dreaming. A total of 36 lucid dreamers took part in this work: 22 in the United States, 10 in Germany, three in the Netherlands, one in France. But on this French patient, 65 experiments were performed, out of a total of 158 for the four groups. This is because he was suffering from narcolepsy, a rare chronic disease which results in irrepressible sleep at any time of the day. The other groups evaluated healthy dreamers.
Difficult but possible dialogue
How did the researchers come into contact with these dreamers? On the experimental side, by sounds (speech or sound beeps), flashes of light or tactile stimuli (by tapping the back of the hand a specific number of times). Side dreamers, it was necessary to be cunning: sensors recorded their eye movements or the contractions of their facial muscles. A communication code was defined in advance. In response to a given instruction, the dreamer had to move his eyes from left to right in a very wide movement – very different from the usual movement of the eyes during REM sleep. To say “two”, for example, he had to do this wide eye movement twice. Another channel of exchange: in response to a question, he had to smile twice to say yes and frown twice to say no. The American, German and Dutch groups subjected the dreamers to very simple mathematical operations, such as “How much is 8 minus 6?” The French group asked questions such as “Do you like chocolate?” Or “How many tats are done on your hand?”
Results: of the 158 experiments, 29 (18.4%) gave correct answers, five (3.2%) to incorrect answers, 28 (17.7%) to ambiguous answers and 96 (60, 8%) to an absence of responses. Of the 36 dreamers tested, six provided at least one correct answer. “It is not so easy to converse with a lucid dreamer. But our study provides proof that it is possible, ”summarizes Delphine Oudiette. Beyond that, “it calls into question the notion that sleep is a state of loss of consciousness where one is cut off from the world”.
This work therefore gives life to this dream of a researcher: to have direct access to what is happening in the dreamer’s head. Until now, in fact, we were content to study the dream told after the sleeper had experienced it during his sleep, “a memory often biased” therefore. This new possibility opens a multitude of doors. “In particular, we could test the hypothesis that dreams promote creativity. To do this, we would ask dreamers to solve puzzles they stumbled upon during their awakening ”, already dreams Delphine Oudiette.
This work already suggests “a small revolution in the world of sleep”, notes the researcher: it is the notion of local awakening or sleep, in the brain. After a sleepless night, for example, parts of our brain might be sleeping while others are awake. Conversely, would there be, during our sleep, parts of our brain awake? The animal world illustrates this notion: dolphins, for example, sleep with only one half-brain at a time, which allows them to remain constantly vigilant and alert. “This work perhaps invites us to revise our sleep rating criteria”, concludes Delphine Oudiette.