Why Doesn't Everything Go Dark When We Blink?

Researchers in Germany have studied epilepsy patients to understand why our vision doesn't appear to cut out when we blink. Getty Images

We blink 20 times per minute, and yet our vision doesn't appear to cut out every few seconds. Why?

According to researchers behind a paper published in the journal Current Biology, the brain draws on previously received instructions when a new image isn't being projected into our eyes.

To investigate how our brains store and send out these short-term memories, scientists at the Deutsches Primatenzentrum (German Primate Center) and the University Medical Center Göttingen enlisted the help of six epilepsy patients for a small study.

Researchers hooked up the participants' brains to electrodes and showed them dot lattices on a screen. The team wanted to investigate a part of the brain known as the medial prefrontal cortex. This part of the brain plays a key role in decision-making as well as our short-term memory.

The team asked the volunteers to report whether the points were running horizontally or vertically. They then repeated the test.

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If the participants repeated the same answer, this suggested their brains had remembered the information from the first test.

The medial prefrontal cortex appeared to project images according to the information it previously received from the eyes, the authors said. This gives us a seamless visual experience without interruption, even when we blink.

The researchers were surprised to find the prefrontal cortex—usually associated with higher-order processes—was involved in this basic perceptual process, Caspar Schwiedrzik of the German Primate Center, an author of the study, told Newsweek.

"This is exciting because it indicates that there is not such a strict separation between sensory and higher-order cortices as is sometimes assumed," he said.

This is believed to be the first study to investigate blinking in the human brain by hooking participants up to electrodes, rather than via an MRI scanner.

Schwiedrzik said, "What you currently experience is always affected by your past experiences, even if you don't notice that."

Scientists are only beginning to understand the neural basis of how we continue to see despite blinking every five seconds, he said. "This is an exceptionally rare opportunity to gain insight into neural mechanisms."

Although the paper offers an interesting new insight into how our brains work on a second-by-second basis, Schwiedrzik acknowledged that the study has a number of drawbacks. For instance, studying epilepsy patients is currently the only way to obtain electrophysiological recordings directly from the human brain.

"Because our subjects have epilepsy, our results need to be taken with a grain of salt, meaning that we did not work with healthy participants and cannot rule out that epilepsy may have affected our results to some extent, although we of course took measures to make this less likely," he said.