But the actual process the brain goes through to wake up is a gradual, coordinated event.
Why we feel so groggy in the morning Once we’re awake, our brains still need time to reach their full cognitive capacity.
But when the cycle wanes, “our sleep is more fragile and it is easier to wake up,” she said.
That’s why Stephan advises her friends to always wake up at the same time, without the help of an alarm.
“What pushes our brain to wake up spontaneously actually remains an open question,” Stephan said.
Even though you may still feel sleepy for a while after waking up in the morning, it may feel as though your brain just turned on when the alarm went off. However, the actual way the brain wakes up is a slow, well-coordinated process. So, how does it actually occur?
Let’s first discuss what it means to be awake. Rachel Rowe, a professor of integrative physiology at the University of Colorado Boulder, explained to Live Science via email that “being awake means the brain is in a state that supports awareness, movement, and thinking.”. The slower, synchronized brain waves that characterize sleep contrast with the faster, more flexible activity that characterizes wakefulness, which enables us to react to our surroundings. “,”.
But the brain doesn’t switch from sleep to wakefulness at any point, according to Aurélie Stephan, a sleep researcher at the University of Lausanne in Switzerland. Studies have indicated that our arousal is caused by the subcortical areas of the brain, which are a collection of neural structures situated beneath the cerebral cortex. The cerebral cortex, the wrinkly outer layer of the brain, is activated by signals sent by the reticular activating system (RAS), which first functions as the “starter switch,” according to Rowe. The thalamus is a structure that transmits sensory information to other parts of the brain.
Additionally, Stephan and her colleagues discovered in a 2025 study that the brain exhibits a distinctive pattern of activity when awake. The research participants’ brain activity first displayed a brief spike in slower, sleep-like waves when they woke up from non-REM sleep, which includes various sleep stages ranging from light to deep sleep. This was followed by faster waves associated with wakefulness.
Their brain waves immediately shifted to faster activity when they awoke from REM sleep, a stage of sleep highlighted by vivid dreams and rapid eye movements. According to the researchers, participants’ brain activity seemed to originate in the front and central areas of the brain and shift to the back as they woke up, irrespective of the stage of sleep they were in.
Why we wake up feeling so sleepy.
Our brains require time to fully develop their cognitive abilities after we are awake. According to Stephan, this phase, known as sleep inertia, can last anywhere from 15 to 30 minutes, and occasionally even an hour. Although the exact cause of this morning grogginess is unknown, our mood can be significantly influenced by the time we wake up. Eliminating the alarm clock may also be beneficial.
According to Stephan, “when your brain [naturally] wakes up, it will send a signal in a moment that makes sense” to awaken you. According to her, there are numerous areas that consider both internal and external cues when deciding when to move people into various sleep stages and, eventually, when to wake them up on their own.
Every 50 seconds or so, our arousal system creates cycles in which we are more alert in response to these internal and external stimuli. Our level of alertness increases and decreases repeatedly during those 50-second intervals.
According to Stephan, “it is harder to be woken up during the buildup phase.”. However, “our sleep is more fragile and it is easier to wake up” when the cycle waned, she claimed. In other words, we have a period of continuous sleep and a period of fragile sleep during these 50 seconds. “.”.
Because of this, Stephan suggests that her friends avoid using alarm clocks and always get up at the same time.
“Your brain will wait for the right fifty seconds, and you’ll wake up feeling less drowsy,” she explained. “It’s somewhat arbitrary if you have an alarm clock. You might have severe sleep inertia after being awakened at the most inconvenient time. “.
Even so, there are still many unanswered questions about waking up. Researchers are still unsure of why getting the same amount of sleep one day feels rejuvenating but not the next. The brain’s transition from awake to asleep, or morning alertness, may be influenced by sleep duration and nutrition, according to some research.
“It’s still unclear what causes our brain to wake up on its own,” Stephan stated.
