What Your Brain Does While You Sleep

What your brain does while you sleep is surprising and much more active than you would think. Your brain is hard at work while you slumber away.

By Nicole Gleichmann

In today’s fast-paced world, it can be easy to take sleep for granted. Many of us even daydream about what we could accomplish if only we stayed awake 24/7.

But we know that getting enough shuteye is important—it’s something we are told from a very young age. Insufficient sleep leads to low energy levels and poor physical performance. Plus, sleep is crucial for our memories and cognitive health.

In this article, we are going to take a tour of your brain while you sleep. Only then can you understand what your brain does while you sleep and why.

The Brain’s Nighttime Journey

woman hooked up for sleep study at night at sleep clinic

Part 1: Falling Asleep

We are going to begin our story in the late evening before you fall asleep. During this time, your brain undergoes many changes that ease you into a calm and sleepy state.

Some of these involve the hypothalamic region of the brain. The hypothalamus is central to our circadian rhythm, which regulates our sleep-wake cycle. For instance, as it gets darker, signals within the hypothalamus encourage a resting state.

At the same time, the activity of brain chemicals changes. Have you ever noticed that your energy levels decrease as the day progresses? The resultant sleepy sensation is partly thanks to a buildup of the molecule adenosine in our brains. In fact, caffeine’s ability to increase our alertness is thanks to it blocking adenosine buildup.

Finally, certain cells in your brain stem and hypothalamus turn on and send you into slumber.

Part 2: The Stages of Sleep

Up next, your brain travels through different types of sleep. During these, brainwaves and brain activity change. These different sleep stages play unique roles in your mental health and wellbeing.

Sleep Stage 1

As you enter this first stage of sleep, your brain slowly changes from wakefulness to sleep. If there is a change in your surroundings, you are likely to wake up.

Sleep Stage 2

Your heart rate and brain waves slow during stage 2 sleep, preparing your mind and body for restorative deep sleep.

Sleep Stage 3

During stage 3 sleep, your brain waves reach their slowest frequency, and it would be hard for anything to disturb your slumber. As a result, stage 3 sleep is also known as slow wave sleep or deep sleep. How much deep sleep you get will dictate how well-rested you feel come morning.

REM Sleep

Finally, you reach the final stage of sleep: rapid eye movement sleep (REM sleep). Your brain is the most active that it will be as you sleep. According to the National Institutes of Health, most of your dreams will occur now as your body is temporarily paralyzed. This sleep stage is pivotal for your memory and learning potential.

Related: REM rebound

This cycle will take around 90 minutes. After you complete your first cycle, it will start over again.

The Brain Benefits of Sleep

Sleep benefits the health and function of your brain in two primary ways.

1. Sleep Helps Our Brains Consolidate and Preserve Memories

Sleep is critical for memory. The National Sleep Foundation includes aspects of memory as three of the top five things that happen in the brain as we sleep. During sleep, we form new memories, consolidate memories, preserve existing memories, and shed memories deemed unimportant.

Sleep is central to both our short term memory and our long term memory. Without sufficient sleep, our learning potential suffers. As a result, we can experience trouble remembering things like where we put our keys or the name of someone we recently met.

2. Sleep Allows Toxins to Be Cleared from Our Brains

As our brains work hard during the day, they accumulate waste products that need to be cleared out. According to animal research, this cleanup happens during sleep. Thus, getting adequate sleep may help to keep your brain healthy and working well.

Sleep Disorders and Sleep

There are many sleep disorders than can influence sleep. They range from narcolepsy, which results in excessive fatigue, to insomnia, which makes it hard to get enough sleep. Sleep researchers are hard at work learning more about sleep and sleep disorders in order to help people get the sleep that they need. If you struggle with a sleep disorder, talk to your doctor or see a sleep specialist to help protect your brain’s health.


Your brain goes through many stages while you sleep, ranging from restorative slow-wave sleep to active REM sleep. Each of these stages plays an important role in the health and function of your brain. To stay sharp and boost your learning potential, aim for 7 hours of sleep each night.

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