Last updated on October 19th, 2018

While your body sleeps, your brain is anything but inactive. In fact, scientists and researchers can use electroencephalography (EEG) to monitor the brain’s waves and activity during sleep. They simply attach the monitoring device using electrodes placed on the scalp and (voila!) the device starts reporting brain waves.

There are 2 major types of activity that occur: K-complexes and sleep spindles. These different types of activity are somewhat similar, though not identical. Are you curious about sleep spindles and what they mean for your brain and body? Here’s a complete rundown of everything you need to know about sleep spindles.

The Mystery of Sleep Spindles Explained 1

Sleep Spindles and Intelligence

Sleep spindles may also be a way of helping us maintain memories and build intelligence.

It’s fairly common knowledge that the brain needs rest to perform at its peak potential. There’s evidence that even brief naps during the workday or school day can help with cognitive function — and there’s also evidence that sleep spindles actually help us learn.

A research team from California has found that a higher number of sleep spindles leads to a refreshed ability to learn. Participants in the study who showed the largest increases in learning ability were the ones whose sleep spindles involved the hippocampus and prefrontal cortex — both areas of the brain that are essential for learning.

Basically, as you sleep, sleep spindles are the brain’s way of reinforcing memories and things learned during the course of the day. If and when those sleep spindles are interrupted, or if stage 2 sleep is abbreviated in any way, key lessons learned and memories made may not be properly backed up in the brain for later recall.

What are Sleep Spindles?

So, what exactly are sleep spindles? Sleep spindles are sudden bursts of brain activity that typically occur during light sleep. Where do they come from? Sleep spindles are oscillatory brain activity that originates in the reticular nucleus area of the thalamus.

Sleep spindles are electrical in nature. They can spread over the entire brain or occur in localized parts of the brain. How do we know this? EEG monitoring devices can be used to track sleep spindles. On EEG readouts, sleep spindles form eye-like shapes, or shapes akin to yarn spindles — which is where the phenomenon gets its name.

Sleep Spindles and Sleep Quality

We have learned so much about sleep science in recent years, and yet many of the things that happen while our bodies are sleeping remain a mystery. For example, researchers and scientists have many theories about sleep spindles and how they affect our bodies, but they don’t have many firm conclusions.

It’s thought that sleep spindles are brief periods of time when the brain is fighting against mental processing. Sleep scientists believe that the brain tries to repress processing during sleep so that they body remains in a tranquil state. If this theory is true, sleep spindles prevent the brain’s activity from waking us up in the middle of a sleep cycle. In short, sleep spindles may be the body’s way of helping us get quality sleep.

Which Stage of Sleep is Characterized by Sleep Spindles?

Sleep spindles are associated with sleep stage 2. During sleep stage 1, the body is just starting to drift off, and it’s easy to awaken. Muscle activity starts to decelerate, and the eyes begin to move more slowly.

During sleep stage 2, eye movement stops altogether, and brain waves begin to slow dramatically — except for sleep spindles. Body temperature drops, heart rate slows, and your body prepares itself for truly deep sleep. It’s during this time when sudden spikes in brain activity appear and quickly dissipate, leaving the eye-shaped readouts known as sleep spindles.

Once the body enters into stage 3, it falls into deep sleep. The brain’s slower delta waves take over, and sleep spindles become much more rare.

What is a K-Complex?

A K-complex is a similar spike in brain activity during stage 2, but there are several key differences between a K-complex and a sleep spindle. First, a K-complex tends to be very high in voltage and very low in frequency — much lower in frequency than sleep spindles.

Perhaps the most significant difference between the different types of brain activity spikes is that sleep spindles seem to occur naturally, whereas K-complexes are induced by external stimulation.

For example, if someone enters the room where you’re sleeping and makes a noise, an EEG monitoring device may show a K-complex responding to that noise. A K-complex may also come in response to a light turning on in a room where you’re sleeping.

Abnormal Sleep Spindles

While sleep spindles remain a partial mystery to sleep scientists, there is evidence that sleep spindle abnormalities are either the cause of serious conditions or a result of serious conditions.

As you’ll see below, for example, asymmetric sleep spindles are often found in those suffering from epilepsy, as well as those with brain tumors. But perhaps the more pressing abnormality is simply a reduction in nightly sleep spindles.

Sleep spindles are thought to be brief periods of time when the brain bursts into activity, presumably to help keep the body in a tranquil state and to help reinforce memories from that day. Some patients suffering from schizophrenia, though, have shown a sharply lower number of sleep spindles than those not suffering from schizophrenia.

But that leads to a question: Does a lack of sleep spindles cause schizophrenia in part or in whole, or is a lack of sleep spindles a side effect of schizophrenia? More research is needed on this subject.

Asymmetric Sleep Spindles

Asymmetric sleep spindles may occur when health issues are present. For example, studies have shown the evidence of asymmetric sleep spindles in patients with brain tumors, as well as patients suffering from different types of epilepsy. While these studies present hypotheses as to why these asymmetrical sleep spindles emerge, each calls for more research in order to better pinpoint the causes.

Gender Differences With Sleep Spindles

Not all studies on sleep spindles control for gender, but perhaps they should. Studies that do control for gender indicate that women tend to have double the amount of sleep spindles as men. It’s possible that these gender differences in sleep spindles can be attributed to estrogen and its greater presence in women than men.

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Final Thoughts on Sleep Spindles

The Mystery of Sleep Spindles Explained 2

Most people probably never think about sleep spindles, if they’re even aware of the phenomenon in the first place. But, by all accounts, sleep spindles are a natural and normal part of getting a good night’s sleep.

While you can’t force your brain to produce sleep spindles, you can take measures to ensure you have the right environment for getting a good night’s sleep — and, hence, the right environment for producing sleep spindles.

Focus on the following 3 things to get a good night’s sleep:

1. Temperature: Studies show that people sleep best in cool rooms. Keep the temperature as cool as advisable when trying to sleep. And, if you get too hot, consider sticking just one foot outside the covers.
2. Clothing: Studies also show that people sleep best in loose-fitting clothing, so find the loose/baggy clothing that makes you feel most comfortable.
3. Noise/Light: You need a distraction-free environment to get good sleep. Make sure your room is as quiet and dark as possible.

If you follow these 3 recommendations, healthy, quality sleep – and the sleep spindles that come with it – should emerge naturally.