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To sort lots of input, brain drives vision

CARNEGIE MELLON (US) — Researchers have identified how different parts of the brain communicate to determine what to visually pay attention to and what to ignore.

For example, if you are looking for a particular object, such as a yellow pencil on a cluttered desk, how does your brain work to visually locate it?

The finding is a major discovery for visual cognition and will guide future research into visual and attention deficit disorders, neuroscientists say.

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“We have demonstrated that attention is a process in which there is one-to-one mapping between the first place visual information comes from the eyes into the brain and beyond to other parts of the brain,” says Adam S. Greenberg, postdoctoral fellow of psychology  at Carnegie Mellon University.

The study, published in the Journal of Neuroscience, used various brain imaging techniques to show exactly how the visual cortex and parietal cortex send direct information to each other through white matter connections in order to specifically pick out the information that you want to see.

“With so much information in the visual world, it’s dramatic to think that you have an entire system behind knowing what to pay attention to,” says Marlene Behrmann, professor of psychology and an expert in using brain imaging to study the visual perception system.

“The mechanisms show that you can actually drive the visual system—you are guiding your own sensory system in an intelligent and smart fashion that helps facilitate your actions in the world.”

For the study, the research team conducted two sets of experiments with five adults. They first used several different functional brain scans to identify regions in the brain responsible for visual processing and attention.

One task had the participants look at a dot in the center of the screen while six stimuli danced around the dot. The second task asked the participants to respond to the stimuli one at a time. These scans determined the regions in both the visual and parietal cortices. The researchers could then look for connectivity between these regions.

The second part of the experiment collected anatomical data of the brain’s white matter connectivity while the participants had their brains scanned without performing any tasks. Then, the researchers combined the results with those from the functional experiments to show how white matter fibers tracked from the regions determined previously, the visual cortex and the parietal cortex.

The results demonstrated that the white matter connections are mapped systematically, meaning that direct connections exist between corresponding visual field locations in visual cortex and parietal cortex.

The researchers used a technique called “diffusion spectrum imaging,” to generate the fiber maps of the white matter connectivity. This gives researchers access to the structural characteristics of brain tissue—something previously only available in humans during autopsy.

This method was combined with high-resolution tractography, a new procedure that allows scientists an extremely detailed estimate of the hard-wired connections between brain regions, providing increased accuracy over conventional tractography methods.

“Because we know that training can alter white matter, it might be possible, through training, that the ability to filter out irrelevant or unwanted information could be improved,” says Greenberg, lead author of the study.

Researchers from Johns Hopkins University, the University of Pittsburgh, and the University of California, San Diego contributed to the study that was funded by the National Institutes of Health.

More news from Carnegie Mellon University: www.cmu.edu/news/

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