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When a Weary Brain Hops Over Hurdles February 22, 2000 - A sleepy brain is never as sharp as a rested brain, but the fuzziness can vary with the task at hand, according to a new study that found signs of a mechanism that can sometimes limit the impact of fatigue. The research was conducted by psychiatrists at the University of California at San Diego and at the San Diego Veterans Administration Medical Center using a brain scan to reveal patterns of activity. The psychiatrists gave 13 people a series of exercises designed to test their math and verbal abilities while normally rested and again over the course of 35 hours without sleep. The math results were reported in December in NeuroReport and the verbal last week in Nature. For math, the people were asked to subtract single digit numbers. "What we found was completely different patterns of brain activation," and a striking drop-off in performance as fatigue rose, said Dr. J. Christian Gillian, the lead author of the research paper. When the subjects were rested, doing the math lit up substantial parts of their cerebral cortex. But fatigue appeared to limit the brain function across the board. For the verbal test, subjects were read a list of 20 words and were asked either to recall them after leaving the brain scanning machine or to recognize them when they were mixed in with a larger list. The tired subjects had a poor recall of the words, but to the researchers' surprise, fatigue made little difference in the recognition test, indicating, Dr. Gillian said, that the information "got into the brain and was registered." But the biggest surprise was that the frontal lobes became more active as the subjects became sleepier. In particular, the parietal lobe, which normally plays only a secondary role in verbal processing, began to be activated. "The greater the activation of the parietal lobes, the more subjects preserved their base line performance," said Dr. Gillian, "which leads us to believe that perhaps the brain is in some way compensating for loss of function elsewhere." By JOHN O'NEIL The New York Times on the Web: Science Copyright 2000 The New York Times Company <http://www.nytimes.com/library/national/science/health/022200hth-vital-signs.html> janet paterson 52 now / 41 dx / 37 onset a new voice: http://www.geocities.com/janet313/ 613 256 8340 PO Box 171 Almonte Ontario Canada K0A 1A0