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In the valley of thought.

The outer layer, or cortex, of the brain bunches up into a convoluted mass of folded tissue that displays on its surface only the top of each fold. The cortical valleys, or fundi, that lie beneath these swarming cerebral summits may help coordinate problem solving and other complex types of thinking, two psychologists suggest in a new study.

"More demanding and complex cognitive functions...rely on cortical fundal activity to a higher degree than do less demanding processes," they conclude in the Oct. 25 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

Hans J. Markowitsch of the University of Bielefeld in Germany and Endel Tulving of the University of Toronto first noted this feature of the cortex in a positron emission tomography (PET) study of memory that they conducted (SN: 3/26/94, p.199). Sentence recall showed a link to blood-flow bursts in or near fundal tissue at the front of the cortex.

Markowitsch and Tulving then combined these data with findings from 29 PET studies conducted by other researchers. Each project included information on whether cerebral bloodflow changes during various mental tests were concentrated in or near the fundus or in other parts of the cortex.

Overall, fundal regions accounted for nearly one-half of the reported areas of peak cortical activity. Cortical valleys displayed the most activity during particularly complex problemsolving and memory tasks. Yet these areas compose only about 8 percent of the entire cortex, the scientists say.

Many investigators doubt that PET scanners clearly separate fundal activity from blood-flow surges at other spots along cortical folds. Markowitsch and Tulving disagree, citing the wide range of PET-specified fundal activity, which increases as mental tasks get tougher.

Anatomical studies indicate that fundal cells handle shortrange communications in the brain. These neurons may also serve as "hubs of cross-cortical traffic," where related lines of information converge to make complex thinking possible, Markowitsch and Tulving theorize.
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Title Annotation:complex cognitive functioning linked to activity in cordical fundi
Author:Cowen, Ron
Publication:Science News
Article Type:Brief Article
Date:Nov 12, 1994
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