CAMBRIDGE, MA -- AUGUST 8, 2005 -- We take for granted that the person we see out of the corner of our eye is the same person when we look directly at her a moment later. But if we were put in a world that doesn't behave like ours, would we see the person differently? Neuroscientists at the McGovern Institute for Brain Research at MIT devised human experiments to address the fundamental question of how we recognize objects. By creating an artificial world, they altered subjects' visual perception without their awareness and discovered one way that the brain naturally recognizes objects. The study appeared yesterday in the advance online publication of Nature Neuroscience.

"We all have an uncanny ability to recognize familiar objects and faces even though we never see the same image on our eye twice," explains James DiCarlo head of the McGovern team. "For example, even when viewing a stable scene, the image striking our eyes changes up to 200 times a minute - each time our eyes move. Somehow the brain recognizes commonalities among the ever-changing stream of images coming into our eyes." Instead of seeing the world as if in strobe light with objects jumping in and out of existence, we perceive objects to be stable.

Although it is often believed that this ability relies on hardwired circuits in the brain, the McGovern Institute study supports the opposing hypothesis that the brain learns to recognize objects by merging images produced while our eyes explore the visual world.

"Our study focused on how eye movements might contribute to our effortless ability to recognize objects at different locations," explains DiCarlo. "Because each eye movement rapidly brings each object from one location on our eye to another, we hypothesized that the movements help us learn to recognize an object, regardless of its location." In other words, these movements might enable the brain to learn that Jane is still Jane even when we are not looking directly at her.

"To test this hypothesis, we played a trick on the brain," explains lead author David Cox, a graduate student in DiCarlo's lab. "We created an artificial visual world where objects on a computer screen did not stay the same, but were replaced by another object while the subjects' eyes were moving." Because the brain is effectively blind during the one twentieth of a second of each eye movement, the subjects were completely unaware that the altered visual world behaved any differently than the real world.

But their brains detected the difference. In tests following one or two hours of exposure to the altered world, subjects confused objects that had been swapped - in reliable and predictable ways. Subjects judged different objects to be the same object at different locations, as if their brains used their eye movements to learn what images belong together to make an "object."

This study provides more evidence of the brain's continuing plasticity and the role of experience in forming neural circuits for tasks as seemingly simple as recognizing objects in different locations. "The real world has structure, and the brain works by discovering that structure. It makes sense that brain adapts to the external reality, even if we manipulate it," DiCarlo comments. The findings may also have implications for artificial vision systems and provide insights into problems in visual recognition often associated with dyslexia and autism.

About the McGovern Institute at MIT

The McGovern Institute at MIT is a research and teaching institute committed to advancing human understanding and communications. Led by a team of world-renowned, multi-disciplinary scientists, The McGovern Institute was established in February 2000 by Lore Harp McGovern and Patrick McGovern to meet one of the great challenges of modern science - the development of a deep understanding of thought and emotion in terms of their realization in the human brain. Additional information is available at: http://web.mit.edu/mcgovern

Contacts
skyemedia, inc.
Lyn Chamberlin, 978-443-0400
lyn@skyepr.com
or
skyemedia, inc.
Derek Beckwith, 978-443-0400
derek@skyepr.com

###