How the Brain Tames the Eyes' Wild Motions Our eyes dart around constantly when taking in a scene. Yet the scene appears stable to us. Scientists have spent years trying to figure out how the brain accomplishes this feat. Now they think they know. The key is a brain circuit that monitors every eye movement and tells the brain how to compensate for it.
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How the Brain Tames the Eyes' Wild Motions

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How the Brain Tames the Eyes' Wild Motions

How the Brain Tames the Eyes' Wild Motions

How the Brain Tames the Eyes' Wild Motions

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  • <iframe src="https://www.npr.org/player/embed/6463390/6463391" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

A diagram shows how a retina scans a series of images and sends the information to the brain. Marc A. Sommer hide caption

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Marc A. Sommer

A diagram shows how a retina scans a series of images and sends the information to the brain.

Marc A. Sommer

Our eyes dart around constantly when taking in the world around us. But the scene appears stable. After spending years trying to figure out how the brain accomplishes this feat, scientists think they know how it's done.

The key is a brain circuit that monitors every eye movement and tells the brain how to compensate for it.

"It's as if I had a movie camera mounted on a bronco. It's jumping up and down," says Bob Wurtz, a senior investigator at the National Eye Institute. "What's photographed would be jumping all around -- enough to make you sick."

Scientists say that the part of the brain that assembles the images we perceive relies on a warning that the eye is about to make a sudden shift. This warning signal alerts the brain to a coming change in direction and focus.

University of Pittsburgh researchers used monkeys to test their ideas, injecting drugs that would block the warning system's messages to the brain.

Wurtz, along with scientist Marc Sommer at the University of Pittsburgh, devised an experiment to find the circuit. The scientists used monkeys to monitor specific cells in two brain areas, while the monkeys looked at moving targets.

One area of the brain tells the eye what to look at and sends a message to move. At the same time, a copy of the message goes to the brain cells that compose our image of the world.

The researchers injected a substance into the part of the brain they believed was involved in storing copies of messages sent to the eye.

Wurtz predicted that messages telling the eyes to move should still get through. But copies of those messages shouldn't.

And that's what happened. The monkeys' eyes moved normally. But their brains lost much of their ability to compensate for sudden eye movements.

In addition to obvious uses like controlling motion sickness, the research may help treat stroke victims, who sometimes lose their ability to track images.

The study appears in the journal Nature.