How Do Brain Waves Affect Sleep?

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Whether you’re fully engrossed in your favorite show or deep in concentration at work, your brain is constantly producing electric signals. And these signals are known as brain waves.

Much like waves in a pond, brain waves are created by the electrical activity of specialized cells, called neurons, firing back and forth to each other. Similar to how different types of waves have different effects on the shoreline, brain waves can alter everything from your mood to your level of alertness. Learning how to work with them can help optimize your productivity, improve your sleep, and even reduce stress.

So, what are brain waves exactly? And how do they affect your mood, emotions, and actions? Let’s take a closer look at what these electrical signals are and how they help keep your brain functioning properly.

What are Brain Waves?

Your body is a complicated machine made up of different systems that all work together to keep you alive and functioning. The nervous system is responsible for transmitting signals between different parts of the body, and it does this by producing electrical impulses. These electrical impulses are what we know as brain waves.

Brain waves are the process by which neurons communicate how you’re thinking, feeling, and behaving at any given moment. The kind of brain waves they send off will determine what state you’re in—whether you’re awake and alert, feeling calm and relaxed, or asleep and dreaming. These electrical signals regulate everything from your heartbeat to your breathing and digestion.

There are four main types of brain waves, each associated with a different state of mind, as well as different emotions and behaviors. The four main types are:

  • Delta Waves: 1-4 Hz
  • Theta Waves: 4-8 Hz
  • Alpha Waves: 8-12 Hz
  • Beta Waves: 12-38 Hz
  • Gamma Waves: 31-100 Hz

Slower brain waves, like delta and theta, are associated with drowsiness, relaxation, and even sleep. As you might expect, faster brain waves, like beta and gamma, are linked to states of alertness and focus. And as it turns out, we go through alternating periods of fast and slow brain waves both when we’re awake and asleep, called a Basic Rest Activity Cycle or BRAC.

Your body goes through BRAC every 90 to 120 minutes. The first 70 to 100 minutes is when you’ll feel most alert, while the last 20 to 30 minutes is when you’ll start to feel drowsy.

This natural ebb and flow of brain activity are thought to be caused by the sodium and potassium balance in your neurons. When your brain uses up all the sodium and potassium it needs to function, it produces slower brain waves to conserve energy and restore its supply.

Brain Waves and Sleep Stages

As you can see, brain waves are a huge factor in how we experience the world around us. But they just affect us when we’re awake—they also play a role in our sleep.

There are four main stages of sleep: NREM 1, NREM 2, NREM 3, and REM. Understanding how brain waves change during each stage can help you sleep soundly and enjoy all the benefits of a good night’s rest.

NREM 1: Falling Asleep

NREM 1 is the first stage of sleep, and it’s when you start to drift off. Your eyes close, your muscles relax, and your brain waves slow down from their usual beta state to a theta state. You’re not quite asleep yet, but you’re well on your way.

This stage usually lasts for about one to five minutes.

NREM 2: Light Sleep

NREM 2 is the second stage, and it’s when you fall into a deeper sleep. Your brain waves slow down even further to long, one-second delta waves known as K-complexes. These bursts help you stay asleep and even consolidate memories.

This stage usually lasts for 25 minutes during your first BRAC cycle and then increases in length with each subsequent cycle. It accounts for nearly half of your total sleep time.

NREM 3: Slow Wave Sleep

NREM 3 is the third stage of sleep, and it’s when you enter deep, restful sleep. Your brain waves slow down to deeper, lower-frequency delta waves. This is the most restorative stage of sleep, and it’s when your body gets a chance to repair itself.

This stage usually lasts for 20 to 40 minutes.  

REM: Dreaming Sleep

REM sleep is the fourth and final stage of sleep, and it’s when you enter a non-restful state of rapid eye movement (hence the name). Your brain waves during REM actually increase in frequency, up to beta waves, which is the same state you’re in when you’re wide awake and alert. It’s also when you’ll experience the most vivid dreams.

This stage lasts about 10 minutes during your first BRAC and can lengthen to as long as an hour during your final BRAC.

How Brain Activity Alters Sleep

As you can see, brain activity can have a big impact on the quality and quantity of your sleep. But various conditions and injuries can alter brain waves and, in turn, your sleep.

For example, people with depression often experience less slow wave sleep, or NREM 3, and more disturbed REM sleep. And as we get older, we spend less time in slow wave sleep and more time in light sleep, which can lead to problems with memory and concentration.

Brain injuries can also cause sleep problems. People with traumatic brain injuries often have difficulty staying asleep. This is because they tend to have increased brain wave frequencies (those associated with more awake, active thinking) during NREM and REM sleep. Meaning they’re still in a state of arousal even when they’re supposed to be asleep.


While we don’t always consciously control our brain waves, they play a big role in everything from our emotions to our sleep.

Understanding how brain waves work can help us optimize our lives and get the most out of every day.

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