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Brain separates working memory: Hemispheres independent in mental version of RAM.

Like side-by-side computer RAM cards, the left and the right hemispheres of the brain store information separately, a new study in monkeys finds. The results help explain why people can remember only a handful of objects at one time and suggest that it maybe possible to maximize mental performance by delivering information in equal doses to both sides of the brain, researchers report in the July 5 Proceedings of the National Academy of Sciences.

On average, people can hold about four things in their working memory at once, such as the location of four cards in a game of Concentration. Scientists still don't completely understand how the brain reaches this limit.

"Why can't you think about 100 things simultaneously, or 50 things simultaneously? Why only four?" says study coauthor Earl Miller of MIT. "If we understand something about that, we'll understand something very deep about how the brain represents information and how thoughts are made conscious."

Miller and his colleagues tested two monkeys (which also have a four-item working memory capacity) in a simple task. First, the monkeys saw two to five colored squares flash on a computer screen for less than a second. The screen went blank, and then the squares reappeared--but one was a different color. The monkeys were rewarded for spotting the change.

As the number of squares increased, the monkeys got worse at finding the color change. But Miller and his colleagues noticed a curious twist: Adding an extra square to the left side of the computer screen didn't affect a monkey's ability to remember squares on the right side of the screen, and vice versa.

Since the monkeys could track about two objects on each side of the screen, this means the magic number of four is really a sum: two objects tracked by each brain hemisphere.

While the monkeys were playing the square game, the researchers also eavesdropped on brain activity using electrodes, which showed a distinctive split in working memory performance. Packing one side of the screen with squares caused nerve cells to go haywire. But adding squares to the sparsely populated side of the screen caused little chaos.

This split-brain finding may lead to techniques for boosting working memory capacity, Miller says. Working memory ability reflects the thinking power that is measured by IQ tests, SAT scores and the ability to learn a second language, says neuroscientist Edward Vogel of the University of Oregon. "The more we understand about these basic capacity limits, the more that's going to tell us something deep about the core cognitive abilities that differ from individual to individual."
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Title Annotation:Body & Brain
Author:Sanders, Laura
Publication:Science News
Geographic Code:1USA
Date:Jul 30, 2011
Words:431
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