Working Memory Capacity Split Between Hemispheres

MIT researchers have made a surprising finding: The two hemispheres of the brain each have their own working memory capacity contributing to a combined overall working memory capacity.

Published in the Proceedings of the National Academy of Sciences today the researchers tested monkeys (who have a similar working memory capacity to humans) with visual items on the left and right of the visual field.

“Surprisingly, we found that monkeys, and by extension humans, do not have a general capacity in the brain,” says Earl Miller, the Picower Professor of Neuroscience in MIT’s Picower Institute for Learning and Memory. “Rather, they have two independent, smaller capacities in the right and left halves of the visual space. It was as if two separate brains – the two cerebral hemispheres – were looking at different halves of visual space.”

The researchers showed the monkeys from two to five colored squares on a computer screen. They then repeated the pattern but with one square altered, thus engaging their working memory. They rewarded the monkeys for noticing the change.

The more items in the sequence, the harder it became for the monkeys to identify the change. But the team noticed that an extra square to the left side of the computer screen had not effect on a monkey’s working memory for items on the right side of the screen, and vice versa. The hemispheres had independent working memory capacities.

Monitoring with electrodes showed that filling one side of the screen with squares caused hyperactivity in the nerve cells. But adding even more squares to the more sparsely populated side of the screen made little difference.

The results could lead to design innovations, Miller says. For instance, airport security staff might be better served if the monitoring display were to scroll vertically rather than horizontally, since sideways movement unnecessarily engages both hemispheres in registering the same information.

Says neuroscientist Edward Vogel of the University of Oregon in Eugene. “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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One Response to “Working Memory Capacity Split Between Hemispheres”

  1. gte697h says:

    Interesting article. Does it mean that we should arrange data vertically when possible to avoid engaging both hemispheres? I wonder if using both hemispheres helps in problem solving but is redundant for say pattern matching or other activities.

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