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Even if you could get more RAM for your brain, the extra storage probably wouldn't make it easier for you to find where you left your car keys.

What may help, according to a discovery published Nov. 24 in the journal Nature, is a better bouncer - as in the type of bouncer who manages crowd control for nightclubs. The study by Edward Vogel, an assistant professor of cognitive neuroscience at the University of Oregon, is the first to demonstrate that awareness, or "visual working memory," depends on your ability to filter out irrelevant information.

"Until now, it's been assumed that people with high capacity visual working memory had greater storage but actually, it's about the bouncer - a neural mechanism that controls what information gets into awareness," Vogel said.

The findings turn upside down the popular concept that a person's memory capacity, which is strongly related to intelligence, is solely dependent upon the amount of information you can cram into your head at one time. These results have broad implications and may lead to developing more effective ways to optimize memory as well as improved diagnosis and treatment of cognitive deficits associated with attention deficit disorder and schizophrenia.

The study used a new technique for measuring brainwaves, developed by Vogel and previously reported in Nature (April 2004), which allows researchers to record the effects as objects pop into the minds of their subjects on a moment-by-moment basis.

Working with two of his graduate students, Andrew McCollough and Maro Machizawa, Vogel recorded brain activity as people performed computer tasks asking them to remember arrays of colored squares or rectangles. In one experiment, researchers told subjects to hold in mind two red rectangles and ignore two blue ones. Without exception, high-capacity individuals excelled at dismissing blue, but low-capacity individuals held all of the rectangles in mind.

"People differed systematically, and dramatically, in their ability to keep irrelevant items out of awareness," Vogel said. "This doesn't mean people with low capacity are cognitively impaired. There may be advantages to having a lot of seemingly irrelevant information coming to mind. Being a bit scattered tends to be a trait of highly imaginative people."

This work was supported by grants from the National Institutes of Mental Health and the Oregon Medical Research Foundation.

At the University of Oregon since 2001, Vogel leads the Visual Working Memory and Attention Lab in the Department of Psychology.

Machizawa assisted with Vogel's research while completing his master's degree. He is now a researcher at the Riken Brain Sciences Institute, Japan's leading funding agency for scientific research.

McCollough, who is working toward his doctorate, is a graduate research assistant in Vogel's lab.

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Image caption:

a. Example of the memory filtering test conducted by University of Oregon researchers. Participants must remember only the red rectangles and ignore the blue rectangles.

b. Brainwaves for high capacity and low capacity participants. Blue line is activity for 4 red items; Black line is for 2 red items; Red line is for 2 red items and 2 blue items. If the red line is close to the black line, subjects are efficient at keeping out the blue items. If the red line is close to the blue line, the subjects are unable to keep the blue items from popping into memory.

c. Correlation between a person's memory capacity and how good they are at keeping the irrelevant items out of memory.

Contact: Melody Ward Leslie, (541) 346-2060, mleslie@uoregon.edu

Source: Edward Vogel, (541) 346-4905, vogel@uoregon.edu