Seals sleeping in water are only half asleep in their brains TORONTO, Feb. 19 (UPI) -- Canadian researchers say a discovery of how seals can sleep with only half their brain at a time could help in research into human sleep problems. An international team of biologists including researchers from the University of Toronto and UCLA said they've identified some of the brain chemicals that allow seals to accomplish their unique sleeping habits. "Seals do something biologically amazing -- they sleep with half their brain at a time," Toronto researcher John Peever said in a university release Tuesday. The left side of their brain can sleep while the right side stays awake. Seals sleep this way while they're in water, but they sleep like humans while on land. Our research may explain how this unique biological phenomenon happens," he said. The researchers studied how different chemicals change in the sleeping and waking sides of the seal brain and found acetylcholine -- an important brain chemical -- was at low levels on the sleeping side of the brain but at high levels on the waking side, suggesting acetylcholine may drive brain alertness on the side that is awake. These findings have possible human health implications because "about 40 percent of North Americans suffer from sleep problems and understanding which brain chemicals function to keep us awake or asleep is a major scientific advance," senior study author Jerome Siegel of UCLA's Brain Research Institute said. It could help solve the mystery of how and why we sleep.