So THAT's Why Our Eyes Move During REM Sleep

Rapid eye movement, or REM, is a stage of sleep in which you’re most likely to dream.

Your heart rate, blood pressure, and even temperature might rise in this phase – and your eyes, well, rapidly move. 

During REM, Harvard Health says, “muscles in your arms and legs also become temporarily unable to move” to prevent you from acting out your dreams. 

But why do our peepers stay so active? 

According to a 2022 paper published in Science, the answer to that might involve your dreams, too.

Why do our eyes move during REM?

According to the paper, in mice, it seems to happen because their eyes are following the scenes in our dreams.

Previously, scientists wondered whether this movement was random.

But this study looked at the “head direction” of dreaming mice, or the area in which their brains seemed to suggest they were going, though of course they were still. 

They compared this to the eye movement of mice in REM, too, and found they matched. 

The researchers think this could be a way to keep human dreams feeling “real” and suggest that REM furthers the idea that our nighttime hallucinations are based on real-life inputs and experiences.

The study’s senior author, Dr Massimo Scanziani, told the University of San Francisco, California’s site about a dream he used to have about breathing underwater (he’s a diver). 

Though he realised it was untrue when he woke up, “In the dream, you believe it’s real because there aren’t sensory inputs to bring you back to reality.

“It’s a perfectly harmonious fake world.”

How does REM coordinate with the brain while dreaming?

In short, we don’t know. 

But Dr Scanziani’s research found that many of the same parts of the brain coordinate during both dreaming and wakefulness, suggesting that some of the same mechanisms are at play in both. 

The hard part, the scientist said, was working out when that process became “generative” – ie during dreaming. 

“One of our strengths as humans is this capacity to combine our real-world experiences with other things that don’t exist at the present moment and may never exist,” he said.

“This generative ability of our brain is the basis of our creativity.”