Why animals must sleep is a mystery to scientists. But a new study suggests that a vital function of sleep is to refuel the brain.
Canadian scientists report that energy stores in the brains of rats decline when the animals are forced to stay awake and the stock rebuilds while the animals sleep. The findings support a hypothesis that dwindling energy stores in the waking brain induce sleep (SN: 5/24/97, p. 316: http://www.sciencenews.org/sn_arc97/5_24_97/fob2.htm).
Most past attempts to test the hypothesis failed because there was no good way to measure brain-energy stores, says Jonathan D. Geiger of the University of Manitoba in Winnipeg, a coauthor of the report. Glycogen, the complex carbohydrate that provides short-term energy storage for brain and muscle, rapidly deteriorates in tissue taken from an animal. So, scientists can't measure glycogen concentrations accurately. Geiger and his colleagues dodged this problem by applying powerful microwaves to rat brains, ki