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Wednesday, Aug. 20, 2014

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Study shows how the brain pays attention

With so many visual stimuli bombarding our eyes -- cars whizzing by, leaves fluttering -- how can we focus attention on a single spot -- a word on a page or a fleeting facial expression? How do we filter so purely that the competing stimuli never even register in our awareness?

A pair of Princeton scientists have found that it has a lot to do with the brain circuits that control eye movements. Neuroscientists Tirin Moore and Katherine Armstrong showed that these brain circuits serve a double function: In addition to programming eye movements, they also trigger amplification or suppression of signals that pour in from the locations where the eyes could move.

The finding, published in the Jan. 23 issue of Nature, is the first to pinpoint a neural mechanism behind one of the most fundamental aspects of mental activity -- the ability to direct attention to one thing as opposed to another.

"Without regulating your attention, you would orient to everything that appears and moves. An organism that couldn't filter anything just wouldn't work. It would be in a state of constant distraction," said Moore. "This work shows that, whether we are moving our eyes or not, the networks that control eye movements may be a source of that filtering."

Working with monkeys, the researchers picked a site in the brain area that controls eye movements and established exactly where neurons at that site made the eyes move. They then located a single neuron, in another part of the brain, that was responsible for processing visual stimuli from precisely the same location targeted by neurons at the eye movement site.

The researchers concluded that the very act of preparing an eye movement to a particular location caused an amplification of signals from that area. The study hinges on a long-known fact in visual attention -- that humans and primates can attend to something without moving their eyes to that object. This ability is useful for many animals that encounter social situations in which there is a potential danger in looking directly at another animal.

The full story is available in a news release.

Contact: Steven Schultz and Evelyn Tu (609) 258-3601

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