La Jolla, CA -- Ever watch a jittery video made with a hand-held camera that made you almost ill? With our eyes constantly darting back and forth and our body hardly ever holding still, that is exactly what our brain is faced with. Yet despite the shaky video stream, we usually perceive our environment as perfectly stable.

Not only does the brain find a way to compensate for our constantly flickering gaze, but researchers at the Salk Institute for Biological Studies have found that it actually turns the tables and relies on eye movements to recognize partially hidden or moving objects. Their findings will be published in a forthcoming issue of Nature Neuroscience.

"You might expect that if you move your eyes, your perception of objects might get degraded," explains senior author Richard Krauzlis, Ph.D., an associate professor in the Systems Neurobiology Laboratory at the Salk Institute. "The striking thing is that moving your eyes can actually help resolve ambiguous visual inputs."

Our eyes move all the time, whether to follow a moving object or to scan our surroundings. On average, our eyes move several times a second in fact, in a lifetime, our eyes move more often than our heart beats. "Nevertheless, you don't have the sense that the world has just swept across or rotated around you. You sense that the world is stable," says Krauzlis.

Just like high-end video cameras, the brain relies on an internal image stabilization system to prevent our perception of the world from turning into a blurry mess. Explains lead author Ziad Hafed, Ph.D. "Obviously, the brain has found a solution. In addition to the jumpy video stream, the visual system constantly receives feedback about the eye movements that the brain is generating."

Hafed and Krauzlis took the question of how the brain is able to maintain perception under less than optimal circumstances one step further. "If you think of the video stream as a bunch of pixe
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Contact: Gina Kirchweger
kirchweger@salk.edu
858-453-4100
Salk Institute
8-Oct-2006