How the Fruit Fly Brain Differentiates Between Self-Generated Visual Movement and Externally Generated Visual Movement

What you see is not always what you get. And that, researchers at The Rockefeller University have discovered, is a good thing. “Every time you move your eye, the whole world moves on your retina,” says Gaby Maimon, Ph.D., Head of the Laboratory of Integrative Brain Function at Rockefeller. “But you don’t perceive an earthquake happening several times a second.” By measuring electrical activity in individual neurons, scientists have discovered that a fly’s brain can cancel out misleading visual signals, effectively blinding the insect to sensory information that would otherwise interfere with its ability to turn while flying. That’s because the brain can tell if visual motion is self-generated, canceling out information that would otherwise make us feel—and act—as if the world was whirling around us. It’s an astonishing bit of neural computation—one that Dr. Maimon and his team are attempting to decode in fruit flies. And the results of their most recent investigations, published in Cell on January 5, 2015 provide fresh insights into how the brain processes visual information to control behavior. The article is titled “Quantitative Predictions Orchestrate Visual Signaling in Drosophila.” Each time you shift your gaze (and you do so several times a second), the brain sends a command to the eyes to move. But a copy of that command is issued internally to the brain’s own visual system, as well. This allows the brain to predict that it is about to receive a flood of visual information resulting from the body’s own movement—and to compensate for it by suppressing or enhancing the activity of particular neurons.
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