2023-10-15 18:30:00
Sleep is generally defined as a period during which the body and mind are at rest, as if disconnected from the world. However, a new study* indicates that the boundary between wakefulness and sleep is much more porous than it seems.
Scientists have shown that sleepers without particular problems are capable of capturing verbal information and responding to it. This astonishing ability manifests itself intermittently during almost all stages of sleep.
The researchers also show that it is possible to predict when sleepers were able to respond to stimuli.
These observations call into question the very definition of sleep and the clinical criteria that make it possible to distinguish between its different stages. They are detailed in a new study published in the journal Nature Neuroscience.
Better understand sleep disorders
These new data on sleep behavior suggest that it may eventually be possible to communicate with sleeping people to better understand how mental activity changes during sleep.
Further research will be necessary to determine whether the multiplication of these windows is correlated with sleep quality, and whether they could be used to improve certain sleep disorders or promote learning.
Finally, these new data could contribute to revising the definition of sleep, a state that is ultimately very active, perhaps more conscious than we imagined, and open to the world and to others.
How did they do it?
To distinguish wakefulness and the different stages of sleep, we have until now used simple and imprecise physiological indicators which do not allow us to understand in detail what is happening in the heads of sleepers, indicates Inserm. So, the research team recruited 22 people without sleep disorders and 27 narcoleptic patients – that is to say victims of irrepressible episodes of falling asleep. Narcoleptic individuals have the particularity of having a lot of lucid dreams.
Participants were asked to take a nap. The researchers gave them a so-called “lexical decision” test during which a human voice spoke a series of real words and made-up words. Participants had to react to them by smiling or frowning, to classify them. Upon awakening, participants were asked to report whether or not they had had a lucid dream during their nap, and whether they remembered interacting with anyone.
« Most participants, whether narcoleptic or not, were able to respond correctly to verbal stimuli while remaining asleep », Specifies Professor Isabelle Arnulf.
*supervised by Delphine Oudiette, researcher at Inserm, Isabelle Arnulf (Sorbonne University, AP-HP) and Lionel Naccache (Sorbonne University, AP-HP) within the Brain Institute. These observations are the result of close collaboration between researchers from Inserm, CNRS, Sorbonne University and AP-HP at the Institut du Cerveau and the Sleep Pathology Department of the Pitié-Hospital. Salpêtrière in Paris and doctoral students Başak Türker, Esteban Munoz Musat and Emma Chabani
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