Why are we knocked out even after a good night's sleep? #shorts
941Researchers from the Netherlands Institute of Neuroscience and the University of Lausanne have discovered that the brain has a rather specific pattern for waking up from sleep. They described this in a study published on July 16, 2025, in the journal Current Biology. This new model could help and improve research into sleep disorders.
To study this phenomenon, the researchers placed 256 electrodes on the heads of around twenty participants and analyzed the brain's electrical activity in more than 1,000 transitions from sleep to waking.
The results reveal a pattern, a diagram that repeats itself with each new awakening. This pattern differs depending on the type of sleep (deep or REM) we are in. One characteristic remains constant, however: the wave of sleep starts at the front of the brain (central and frontal areas) and spreads backward.
Aurélie Stephan, lead author of the article, details the results in a press release: "This progression likely reflects how signals from subcortical arousal centers (deeper in the brain) reach the cortex, with shorter paths to frontal areas and longer paths to more posterior regions."
Sleep consists of different stages. These include rapid eye movement (REM) sleep (known as REM and associated with dreams) and deep sleep, referred to as non-REM sleep (or non-REM) in the study. The researchers distinguished two different patterns depending on the type of sleep from which participants awoke.
In non-REM sleep, awakening began with slow, progressive electrical waves, which then continued with rapid electrical waves. "In non-REM sleep, neurons connecting arousal centers to the cortex alternate between active and silent states—a dynamic known as 'bistability.'" "Because of this bistability, any exciting stimulus first triggers a slow wave, before moving on to faster activity," explains Aurélie Stephan.
And to make matters worse, there are different types of slow waves during non-REM sleep. Some of them are intended to signal wakefulness and therefore arousal, while others help keep us asleep. These waves can be present before or after waking up, and they explain why we can be drowsy early in the day.
The author continues: "In contrast, REM sleep lacks this bistable pattern, so the cortex reacts immediately to the rapid activity, similar to waking up." In the REM sleep phase, the brain therefore emits rapid electrical waves directly, bypassing the slow wave stage. The brain then wakes up more quickly, but leaves the person feeling drowsy.
"This study offers a new perspective on the brain's journey from sleep to wakefulness, providing a window into one of the most fundamental transitions in human consciousness," concludes the researcher. She hopes her research will lead to advances for people with sleep disorders.