This Is Why Our Eyes Move When We Sleep

Chances are, you've probably heard of rapid eye movement (aka the REM sleep cycle) before — when our eyes dart back and forth during our deepest level of snoozing. But as for why our eyes move around when we sleep? Researchers at Tel Aviv University in Israel claim to finally have the answer, and it's kinda weird, but kinda cool: We're watching our own dreams.

According to the National Institute of Neurological Disorders and Stroke (NINDS), we all experience four stages of sleep, including REM, which comes at the end. Stage one is light sleep — that phase of drifting in and out of consciousness where we could easily be woken up. During this stage, you might visualize fragmented images, feel like you're falling, lose a little awareness of your surroundings, and even lose muscle activity. Stage two, however, is when your eye movements stop and your brain waves get slower. (In fact, we hang out in this stage for about 50 percent of our sleep time.) Then there's Stage three, also known as deep sleep. Even though this is the most relaxing sleep cycle for your body, it's also the stage where night terrors and sleepwalking can happen.

Finally, there's REM — when your body is basically like "OK, I'm done, goodnight for real this time, guys!" In this stage, your muscles become paralyzed, your heart rate and body temperature become unregulated, you experience vivid dreams, and your eyes dart back and forth.

So how did researchers discover that REM happens when we're visualizing things we "see" in our dreams? According to LiveScience, neuroscientists at Tel Aviv University closely monitored the asleep and awake activity of 19 epilepsy patients for two weeks using electrodes fitted to their brains. What they found was that the parts of the brain associated with visual perception and memory lit up very quickly after patients moved their eyes in REM sleep. Their conclusion? That there must be a relationship between eye movement and the patient watching the dream. Pretty neat, right?

The findings are especially cool considering we don't know all that much about sleeping, and know even less about dreaming. Research like this could give us a ton of insight into human sleep behavior — not to mention why we dream, what we see when we dream, and what our dreams mean. Until then, I'll just assume that my recurring dreams about candy palaces and chocolate fountains mean that I have to eat something delicious and sweet for breakfast.

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