YouUnless you have a very bad night, you will eventually fall asleep, your head falling into the pillow, and your mind losing control of consciousness. If you have insomnia, reaching that blissful moment may take much longer. But once your brain opens the door to the elusive boundary beyond full consciousness, it will be more like “falling” than you think.
Researchers recently discovered that the transition from wakefulness to sleep reaches a tipping point of sorts, after which sleep immediately sets in, and that this point can be easily predicted within 49 seconds of the event using EEG. The discovery flies in the face of common models of how sleep works, which have long been thought to be a journey into darkness that unfolds over time.
“We found that falling asleep is a bifurcated process, rather than a gradual process, with a clear tipping point that can be predicted in real time,” lead study author Nir Grossman of Imperial College London said in the paper. statement.
To map this moment of sleep, Grossman and his colleagues collected overnight scalp EEG readings from more than 1,000 people, tracking what they call “sleep distance,” or how close your brain is to falling asleep, moment by moment. Their resultspublished in Nature Neurosciencecan help develop early warnings of drowsiness to promote safe driving, as well as the diagnosis and treatment of sleep disorders such as insomnia, narcolepsyand excessive daytime sleepiness.
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In the group data, the scientists found that brain activity dropped sharply about four and a half minutes before the onset of normal sleep. This occurred regardless of age, gender, or how long it took the person to fall asleep. The researchers first observed the dynamics in their sample of 1,000 people and then replicated the results in a smaller cohort of 36 people in the lab, with each participant spending an average of seven nights in the sleep lab. To further validate their results, they used the data to successfully predict individual sleep progress in real time.
Until now, our understanding of how sleep occurs has been largely based on the classification system proposed more than three decades ago by a trio of Japanese researchers Tadao Hori, Mitsuo Hayashi and Toshio Morikawa, who believed that falling asleep consists of a sequential transition between nine different EEG patterns, such as trains of alpha waves, intermittent alpha waves and sharp apex waves. But the time spent in each of these stages varied greatly among individuals and was time consuming to measure.
More recently, neuroscientists have attempted to quantify gradual changes in specific EEG characteristics, but the transition process between wakefulness and testable sleep was still often characterized as a prolonged state of sleepiness. Ultimately, the researchers of the new paper note, these approaches have neither helped us understand the actual experience of falling asleep nor developed new methods for managing and treating poor sleep.
The team noticed that sleep onset travels through different parts of the brain at different times. For example, the occipital cortex, which is involved in processing visual information, begins to shut down earlier than the frontal cortex, which is involved in planning and decision-making. And they acknowledge that the tipping point model proposed based on their data does not exclude other possible models of the sleep process.
But if what they discovered is correct, then what we call “snagging away” is actually more like falling off a cliff into oblivion.
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