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Working memory makes a spatial move.

Spirited debate surrounds the theory that the human prefrontal cortex, a slice of brain tissue just behind the forehead, takes charge of working memory, which temporarily holds and organizes information needed for tasks such as reading or driving a car.

A new study places two distinct types of working memory, one for objects and the other for spatial relations, in separate parts of the prefrontal cortex. The exact location of spatial working memory in humans had escaped notice in the past because it lies some distance from the location of spatial working memory in monkeys, which had already been identified, according to neuroscientist Susan M. Courtney of the National Institute of Mental Health in Bethesda, Md., and her colleagues.

Brain tissue involved in spatial working memory was pushed up and back during human evolution as other prefrontal regions grew in size, the researchers theorize. Prefrontal expansion apparently aided complex problem solving and planning for the future.

Building on prior work (SN: 4/26/97, p. 258), Courtney's group used functional magnetic resonance imaging to measure second-by-second oxygen consUmption in the brains of 11 volunteers during memory tasks. Rises in oxygen use signal heightened neural activity.

On a spatial memory task, participants saw a series of three faces presented at various spots on a computer screen for 2 seconds each; after waiting 9 seconds, they viewed another face and indicated whether its location matched that of any of the prior faces. On a face memory task, volunteers indicated whether the final face was the same as any of the earlier faces.

Different prefrontal areas showed activity hikes during each task, the scientists report in the Feb. 27 Science. As in monkeys, the human spatial memory area straddles a neural site that controls eye movements, they say.

Some scientists, such as Patricia S. Goldman-Rakic of Yale University, agree that separate prefrontal regions handle working memory for objects and spatial relations in monkeys and humans.

Others, like Michael Petrides of McGill University in Montreal, argue instead that separate prefrontal areas in humans foster either immediate applications of all types of working memory or more extended manipulation of working memory contents.
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Title Annotation:new study argues that working memory for objects and spatial relations is located in different parts of the prefrontal cortex
Author:Bower, B.
Publication:Science News
Article Type:Brief Article
Date:Feb 28, 1998
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