Tiny eye movements affect how we see contrast

ScienceDaily | 1/28/2019 | Staff
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Researchers previously believed contrast sensitivity function -- the minimum level of black and white that a person needs to detect a pattern -- was mainly dictated by the optics of the eye and processing in the brain. Now, in a study published in the journal eLife, researchers, including Michele Rucci at the University of Rochester, explain that there is another factor at play: contrast sensitivity also depends on small eye movements that a person is not even aware of making.

"Historically these movements have been pretty much ignored," says Rucci, a professor of brain and cognitive sciences at Rochester. "But what seems to be happening is that they are contributing to vision in a number of different ways, including our contrast sensitivity function."

Eyes - Point - World - Microscopic - Level

When we fix our eyes on a single point, the world may appear stable, but at the microscopic level, our eyes are constantly jittering. These small eye movements, once thought to be inconsequential, are critical to the visual system in helping us reconstruct a scene, Rucci says. "Some scientists believed that because they are so small, the eye movements might not have much impact, but compared to the size of the photoreceptors on the retina, they are huge, and they are changing the input on the retina."

Think of a scene or object like a computer image made up of different pixels, or points. Each point is a different color, intensity, luminance, and so on. Our eyes take in signals from each of the points and project the signals onto photoreceptors on the retina: the arrangement of these points makes a spatial pattern that we perceive as a scene or object. But, if a spatial pattern is projected as a stationary image, it will fade from view once the retina's photoreceptors become desensitized to the signal -- like a student...
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