What does your brain do when you are sleeping?

Why is Sleep Important for the Brain?

Workers are more productive, students are better learners, and leaders make better decisions when they’ve had a good night’s sleep. Also, we all have better control over our emotions when we’re well-rested.

Scientists are still trying to understand the restorative qualities of sleep, but there’s no doubt that sleep supports learning, development and mental health. With that in mind, let’s explore this intriguing relationship between sleep and brain power.

Psychological Benefits of Sleep

Adults should aim for 6-8 hours of sleep per night. Good-quality, regular sleep can offer the following psychological benefits:

  • Improved Memory – Several human and animal studies have demonstrated how sleep improves spatial, procedural, and declarative memory. As we’ll explore, certain stages of sleep solidify certain ‘types’ of memories.
  • We Become Better Decision Makers– Studies have shown that, after a good night’s sleep, we’re confident and flexible in our decision making. Not only that, we’re better problem solvers. If you’ve ever uttered the phrase ‘let me sleep on it’, you already know how important sleep is for making good judgments.
  • Improved Cognitive Functioning – When we’ve slept well, we learn more efficiently and score higher on academic tests. This is partly because we’re more able to concentrate. When we’re well-rested, our attention span lengthens considerably.
  • Protection from Mood Disorders – Sleep deprivation de-regulates mood and emotions. Indeed, many practitioners advise people at risk of depression to sleep for 8 hours, every night.
  • Enhanced Creativity – When we enter the REM stage of sleep, we have dreams and nightmares. Some people believe that dreams inspire creativity in our waking lives. Indeed, some famous pieces of art and literature were conceived of during dreams.
  • A ‘Clean’ and Restored Brain – Recent studies suggest that sleep may actually ‘clean’ the brain of a toxin called beta-amyloid. An accumulation of beta-amyloid can cause neurological conditions such as Alzheimer’s disease.

A little later, we’ll discuss how to modify your sleeping habits to improve your brain health. For now, let’s explore the mechanics of sleep in a little more detail.

Brain Activity During Sleep

Have you ever wondered what your brain does when you are sleeping? Brain activity is incredibly complex, but it can be summarized into four ‘stages.’ Neurochemical activity differs during each of these stages. The first three stages are referred to as ‘NON-REM’ sleep, and the last stage is ‘REM’ sleep.

  • N1 – The hypothalamus (a small structure inside the brain) signals for brain activity to slow down. This is a very light stage of sleep, and most people could be easily roused from this stage of sleep.
  • N2 – Brainwaves reduce in frequency, and there is minimal eye movement. There are short, intermittent bursts of electrical activity during this stage.
  • N3 (Slow-wave Sleep) – Brainwaves slow down even further, and there are no bursts of electrical activity at this stage. This is the deepest stage of sleep – it would be hard to wake someone up from slow-wave sleep.
  • REM – During this stage, brain waves and eye movements quicken, mimicking the waking state. REM sleep (Rapid Eye Movement) occurs approximately 90 minutes after we’ve fallen asleep. We stay in REM sleep for about 10 minutes before starting the cycle again. Throughout the night, the duration of REM sleep increases.

For the brain to benefit from sleep, we should avoid sleep disruptions and get 6-8 hours’ sleep per night. This allows our bodies to pass-through the sleep cycles cyclically (without disruption) and enables us to benefit from good quality REM sleep.

To begin with, let’s explore why REM sleep and slow-wave sleep are so important for memory.

Why is REM Sleep Important for Memory?

During REM sleep our mind consolidates new information and helps us to store memories. In particular, REM sleep allows us to rehearse skills we’ve practiced during the day (i.e., driving a car safely, bicycle riding, or learning a new route).

Procedural Memory

Let’s take the example of riding a bicycle. When you learn to ride a bike, you’re not required to learn facts and figures (declarative memory). Instead, you need to remember how to maneuver the gears at the right time and how to balance yourself on the saddle. Learning to ride a bike requires ‘spatial’ and ‘procedural’ memory skills.

why does the brain need sleep?

According to a review published by Science Direct, REM sleep is crucial for rehearsing skills-based tasks. So, if you want to get better at that new hobby you’ve taken up, make sure you’re clocking-up 7-8 hours of sleep per night!

Sleep Spindles

Brain activity increases during the REM sleep cycle – mimicking our waking brain activity. According to a review on APA, the brain produces ‘sleep spindles’ during REM sleep. Sleep spindles are short 1-second brainwaves that rise and fall rapidly. These brainwaves help to transport information from our short-term memory to our long-term memory stores.

Sleep spindles are more likely to occur in the latter cycles of REM sleep (i.e., after 6 hours of sleep). So, if you want to strengthen your long-term memory, try to get more than 6 hours sleep on a regular basis.

Why is Slow Wave Sleep Important for Memory?

Slow-wave (delta) sleep is a very deep stage of sleep that strengthens the relationship between neurons in the brain (synapses).  Synapses help to consolidate memories. In contrast to REM sleep, slow wave sleep consolidates our ‘declarative memory’ (as opposed to our procedural memory).

Declarative Memory

Our declarative memory consists of ‘episodic’ and ‘semantic’ memories. Episodic memories are autobiographical memories (i.e., recalling what you did last Monday) and semantic memories are facts and figures (i.e., knowing that Madrid is the capital city of Spain).

Several studies have shown that slow-wave sleep is very important for consolidating our declarative memory, as opposed to our procedural memory. We require a strong declarative memory to perform well on tests and to make effective decisions.

Forgetting in Old Age

A brain region called the medial prefrontal cortex is responsible for modulating slow-wave sleep. As we get older, the medial prefrontal cortex is less active, and our slow wave sleep reduces significantly. Some older people may go nights without any slow-wave sleep at all.

According to the National Institute for Health, this explains why older people are more likely to forget things – particularly dates, names, and episodic memories. In contrast, older people are unlikely to forget how to perform a task, and their ability to learn new tasks is mostly unimpaired by age. This is because slow-wave sleep declines at a greater rate than REM sleep!

Can Daytime Naps Improve Adults’ Memory?

Studies show that naps help preschool children memorize new information, but could adults benefit from daytime naps, too?

A study published by Nature Journal found that daytime naps may improve memory skills in adults, but only if the naps contain both slow-wave sleep and REM sleep. Naps that contain both of these sleep stages would need to be at least 60-90 minutes in duration.

Why is Sleep Important for the Brain?

Although naps may improve memory, adults are probably better off getting their sleep at night time because naps can disturb our sleep/wake cycles. Indeed, according to a study published by Learning and Memory Journal, revising just before bedtime (and sleeping for 7-8 hours) is the best way for adults to exploit the memory-boosting effects of sleep.

Sleep is Important for Decision Making

The Chernobyl disaster and the American Airlines flight 1420 catastrophe were partly caused by sleep-deprived individuals. Ultimately, sleep deprivation led to poor decision making.

The prefrontal regions of the brain hel­­p to modulate emotion, judgments, and decision making. If we are sleep deprived, neurochemical activity in the prefrontal regions becomes impaired. As a result, it becomes difficult to think clearly.

Rigid and Lazy Thinking

A study published by NCBI found that just one night of sleep deprivation had a negative impact on decision making. Specifically, the sleep-deprived volunteers became very rigid in their thinking and lacked innovation in their ideas.

They were given a scenario and asked to make strategic decisions based on the information available. Even when new (crucial) data was added to the scenario, the volunteers did not modify their decisions. Ultimately, this study found that the sleep-deprived individuals were ‘lazy’ thinkers.

When we are tired, we are more likely to make ‘lazy’ judgments. In the real world, ‘lazy’ judgments are associated with prejudice and discrimination, so sleep deprivation is something we should all avoid.

Moral Judgments

Indeed, a review in the New Scientist found that sleep-deprived people took much longer to consider moral dilemmas (compared to people who’d had a good night’s sleep).

The experimenters asked moral questions such as ‘would you sacrifice one life to save 100 lives?’ They also asked neutral questions such as ‘would you substitute ingredients in a recipe?’ Interestingly, the sleep-deprived volunteers took a lot longer to answer moral dilemmas than they did neutral dilemmas.

As such, they weren’t just slow to answer the moral-based questions because they were tired, they were slow to answer these questions because sleep-deprivation modified their ability to make sound moral judgments. When it came to the moral dilemmas, they were unable to think clearly.

Studies like these suggest that decision-makers in positions of power (doctors, politicians, judges, managers) should ensure they get enough sleep, so they can be confident they’re making sound moral judgments.

Can Sleep Prevent Depression and Anxiety?

Recent studies have shown that regularly sleeping for less than 6 hours, and delaying sleep until late in the night, are both associated with depression. Sleep deprived individuals are more likely to engage in ruminating thoughts (repetitive negative thinking) than people who regularly sleep for 6-8 hours.

Also, studies have shown that sleep-deprived individuals are more likely to lose their temper with others and are less likely to be interested in socializing. This is significant because we know that social-support systems protect against anxiety and depression.

Alarm Clocks and Anxiety

According to a study on Semantic Scholar, both slow-wave sleep and REM sleep help ward-off depression. Regulating the sleeping cycles, and reducing sleep disruptions, can help prevent mood disorders developing.

Some mental health practitioners advise patients to avoid using alarms (unless necessary). Alarms can cause you to wake up in the middle of a sleep cycle. For some people, this can make anxiety worse because it disrupts chemical activity in the brain, leaving them feeling ‘on-edge’ for the rest of the day.

How sleep affects the mind

If possible, it’s better to try and train your body to wake up naturally at the time you need to wake up. You can do this by practicing good sleep hygiene and sticking to a routine.


The relationship between mood disorders and sleep is very complex, and not completely understood by scientists. Some people with depression tend to oversleep, which can make their condition worse. So, although sleep deprivation should be avoided to protect brain health, oversleeping should be avoided, too.

What Is the Function of Dreams?

Dreams and nightmares occur exclusively during REM sleep cycles. Some people are skeptical about the importance of dreams. On the other hand, many psychotherapists would say that dreaming is crucial for our psychological well-being.

Let’s explore the potential ‘function’ of dreams:


Dreams are not limited by the rules and expectations of our waking lives. As such, they could be a creative ‘outlet’ for our unconscious mind. Some people use the content of their dreams to inspire artworks in their waking lives. For example, Mary Shelley’s Frankenstein was originally conceived of in a dream.


Several studies have found that people who are regular ‘dreamers’ are better able to store and recall new information. This has led scientists to believe that dreams may be a way of our mind rehearsing and storing new information. This theory makes sense as we know that procedural memories are solidified during REM sleep and that dreams form a part of REM sleep.

Emotion Control

During REM sleep, the amygdala and limbic system are activated. These parts of the brain are strongly associated with our emotions.  Some scientists believe that dreams help us ‘work through’ our residual emotions. This might explain why we have more dreams after a profound experience – such as a bereavement, a breakup or a big personal achievement.

If it’s true that dreams enhance our waking lives in these ways, we should avoid going to bed too late, or regularly cutting our sleep short – as we’ll restrict our access to REM sleep.

Can Sleep ‘Clean’ the Brain?

According to a review by the National Institute of Health, sleep may help ‘clean’ the brain of toxic substances.

The brain has its own drainage system that helps to reduce the presence of beta-amyloid (a toxic substance). When we’re asleep, the space around our brain cells increases, allowing for effective drainage of unwanted toxins. Conversely, when we’re sleep deprived, beta-amyloid protein starts to accumulate in the brain’s tissue.

An excess of beta-amyloid is associated with many neurological diseases such as Parkinson’s, Alzheimer’s and strokes. Good quality sleep will not necessarily protect against these conditions in old age, because we naturally sleep for shorter periods when we’re older.

Nonetheless, as a result of this study, scientists created a drug which helps to encourage the drainage of beta-amyloid from brain tissue, thereby slowing down the development of Alzheimer’s disease in some patients.

Importance of Sleep for Students

According to a recent study, 73% of college students are dissatisfied with the quality of their sleep. Not only that, students who are sleep-deprived achieve poorer grades in their classes and are less likely to show an interest in career goals.

Achieving good grades requires the following skills and abilities:

  • A strong memory (to ace exams)
  • Thinking ‘outside the box’ (flexible and innovative thinking)
  • Having a long attention span (for learning)
  • Creativity

As we’ve discussed, these skills are all strengthened by regular, high-quality sleep. Unfortunately, the people who require these skills often get the least amount of sleep.

Also, socializing and peer-group relations are a crucial aspect of ‘student life.’ We know that people who get adequate sleep are more likely to be sociable and less likely to lose their temper around others. As such, sleep becomes even more important for students to avoid social isolation and get the most out of their learning experiences.

How to Improve Sleep (and Boost Brain Power)

Now we’ve discussed what sleep can do for the brain, let’s explore how you can improve your sleep – to boost your brain power!

  • Establish A Routine – Try to go to sleep at the same time each night. This will prevent you having to rely on an alarm clock to wake up – so you need not be disturbed part-way through a sleep cycle. Ultimately, this should promote chemical balance in the brain and prevent mood disorders.
  • Reduce Nighttime Disturbances – Following on from the last point, try to reduce nighttime disturbances, so your ‘slow-wave sleep’ and REM sleep cycles are not unnecessarily disturbed. This will help you seize the benefits of sleep, such as memory consolidation, creative dreaming, and emotion regulation. To achieve this, try to avoid drinking fluids too near bedtime, so you do not need to wake up to use the toilet. Also, you could consider using a white noise machine.
  • Keep a Dream Diary – If you’re convinced by the potential benefits of dreaming (enhanced creativity, emotion regulation, improved memory), try to keep a dream diary. This will enable you to remember your dreams and may even encourage you to dream more often.
  • Get an Early Night When You Need It – If you’ve got an interview or meeting to attend, try not to stay up late the night before. Sleeping for 8 hours will help you think clearly. You’ll make more persuasive arguments, and ‘sell’ your ideas in innovative ways.

Other Ways to Strengthen Brain Power

Improving your sleep habits is just one way to strengthen cognition. The following lifestyle changes can strengthen neurochemical processes, and promote psychological well-being:

Increase Omega 3 Fatty Acids

A deficiency in omega three impacts levels of serotonin and dopamine in the brain – potentially leading to depression. The modern western diet contains lots of omega six fatty acids but comparatively few omega three fatty acids. Try to cut out all processed foods and eat more:

  • Soybeans
  • Oily Fish (mackerel, Sardines, anchovies, fresh tuna)
  • Shellfish (mussels, oysters, crab, squid)
  • Walnuts
  • Green leafy vegetables
  • Plant-based oils (Rapeseed/Canola, linseed, Mustard)

My mind won't shut down and let me sleep

Get More Tyrosine

Tyrosine is an amino acid that enables the brain to produce norepinephrine and dopamine. These chemicals are vital for cognitive functioning, learning, and mood control.

Foods rich in tyrosine include:

  • Eggs, milk, and cheese
  • Poultry
  • Most beans
  • Spirulina (seaweed)

Exercise Regularly

Exercise is ‘nature’s antidepressant’ because it boosts serotonin and dopamine levels in the brain. According to a review by Harvard Medical School, exercise not only improves mood, but it also boosts memory and problem-solving skills. Indeed, people who exercise regularly have more activity in their prefrontal cortex – a brain area responsible for thinking and memory!

Ginkgo Biloba

There is good evidence to suggest this herbal supplement can reduce anxiety and improve memory. In fact, some doctors are using this supplement to treat Alzheimer’s disease.  It’s thought the chemical components of ginkgo biloba have an anti-inflammatory effect on certain neural pathways, which helps to prevent neural damage.

Be Inquisitive

Although the brain is technically an organ, it operates much like a muscle; if you don’t use it, you lose it. Mental stimulation helps to generate new pathways between cells in the brain (synapses). Ultimately, this can prevent you losing too many cells through aging.

Try something that challenges you. It doesn’t have to be a huge project – just something out of the ordinary. For example, if you usually stick to Sudoku puzzles, try a crossword instead. Learning a musical instrument or making something with your hands is a great way to build new neural pathways and develop your psychomotor skills.

Moreover, when you achieve something new, your brain enjoys a boost of oxytocin (one of the ‘feel-good’ chemicals).

How Important is Sleep for Brain Health?

Sleep deprivation, whether temporary or ongoing, can be detrimental to brain health. When we sleep, neural pathways (synapses) are strengthened and restored. This helps to consolidate our memory, decision-making skills, moral awareness, and our creative skills.

If you’re trying to learn a new skill (i.e., driving), you should try to clock-up 7-8 hours of sleep every night. This will consolidate your procedural memory and hopefully help you pass your test sooner. Similarly, if you’re a student looking to improve your grades, stick to a regular sleep routine so you can enjoy the benefits of brain-boosting sleep.

Although good-quality sleep supports brain health, it’s important not to exceed the recommended 8 hours of sleep on a regular basis. Oversleeping is strongly associated with brain fog, anxiety, and depression. So, if you want to develop strong cognitive skills and enhance your mental health – inject some balance and consistency into your sleep schedule.