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Whether you're in a deep sleep, taking a test, or watching a YouTube video, your brain is abuzz with activity. There are millions of electrical pulses passing between neurons that are sending messages to each other.

When those signals spread, clusters of neurons start getting feedback from others, and networks of cells synchronize their firing. It becomes a repeating cycle or rhythm: a brainwave, or as neuroscientists call them, neural oscillations. That organized electrical activity is strong enough to be detected by electrodes on the scalp with a technique called electroencephalography, or EEG.

And that's allowed us to study brainwaves to try to make sense of the brain. While things are still pretty mysterious, lately we've been making strides to link brainwaves to things like consciousness, memory, and maybe even certain diseases. Now, brainwaves aren't one-size-fits-all.

There are actually lots of different electrical patterns, defined by their frequency. They're measured in cycles, or the number of times the neurons are firing, per second. Brainwaves also vary in amplitude, with lower amplitudes as they speed up.

There are 5 main types, and there's no hard-and-fast rules about their functions. But, generally: the higher frequency the wave, the more alert and awake you are. So the slowest of these 5 waves, which are of relatively high amplitude, are delta waves.

They're typically linked with deep sleep. Slightly faster are theta waves, which are often associated with day-dreaming or meditation. The next step up are alpha waves.

These are common when you're awake, but relaxed, like when you still have your eyes closed. Beta waves are even higher frequency and lower amplitude, and seem to happen when you're awake and thinking about something. The smallest, fastest oscillations are gamma waves.

They tend to be around when you're deeply focused on something. Now, even though we talk about beta waves when you're in class or delta waves when you're sleeping for simplicity's sake, the reality is that your brain is abuzz with all different frequencies of waves. It's just that certain ones are more dominant at any given moment, depending on what you're doing and how you're feeling.

If you're chilling at the pool, and sometimes closing your eyes to bask in the sun, you probably have a lot of alpha and theta going on. But there's still some beta waves in the background. And it's not like your brain has the exact same wave frequencies throughout the whole thing.

If you look at the readings from individual electrodes on an EEG, you can see that different regions of the brain are more commonly linked with certain waves. Alpha waves, for instance, are usually strongest at the back of the brain in the occipital lobe, which handles vision. One of the amazing things about brainwaves is that these common frequencies are remarkably similar across different species, like cats, bats, and us.

But at the same time, they might be very different between individuals. Some neuroscientists have even proposed that a snapshot of all the waves going on in a brain could be used to identify a person, like a fingerprint. So, in some ways, measuring brainwaves could be very powerful.

Like, I can probably guess the moment you open your eyes just by looking at when your alpha waves drop off. Kinda freaky... And doctors have successfully used EEGs to diagnose people with epilepsy.

Brainwaves punctuated with spikes are tell-tale signs of a seizure. But we still don't fully understand why we have these rhythms in the first place. One popular idea is that the synchronized firing allows neurons to better communicate with one another.

Recent work even suggests that the use of different brainwaves helps us learn. Researchers gave monkeys a test, where they had to learn to associate pairs of images through trial and error. They found that when the animals got an answer right and received a reward, their brains seemed to be using beta waves to communicate to the hippocampus, the brain's memory center.

When the monkeys got the answer wrong, theta waves dominated. So, beta waves might be a way of reinforcing neural connections to improve memory, while theta waves are a way of saying to the brain, “hey, oops … forget that.” Gamma waves are especially interesting to neurobiologists, too, because people with Alzheimer's don't seem to use them as much. In fact, in experiments in mice, restoring gamma waves reduced the amount of beta-amyloid, the plaque protein associated with the disease.

The researchers genetically modified mouse neurons so they would respond to light, and then flashed pulses at a gamma wave frequency for an hour a day for a week. The animals that received this treatment had half as many plaques in their visual cortex compared to controls. The team thinks that gamma activity somehow makes immune cells in the brain better at gobbling up the plaques, and also changes how the protein is processed, leading to less plaque in the first place.

Scientists aren't sure why gamma waves would do this, but their work suggests brainwaves can actually change the biology of the brain. And this could be huge ... if you could figure out how to trigger gamma waves in people, they could be used as a treatment. But we really have no idea how to do that yet in humans, and of course, we don't know if it'd actually work.

Still, even if we don't totally get why they exist or how they work, it's clear that brainwaves are pretty important. Understanding the electrical activity is just as important as understanding the chemical processes when unraveling the mysteries of how our brains tick. Thanks for watching this episode of SciShow Psych, which was brought to you by our patrons on Patreon.

If you'd like to help us make more episodes like this, you can go to patreon.com/scishow. And don't forget to subscribe! [OUTRO ♪].