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Scientists have discovered how seals are able to sleep with only half of their brain at a time, according to a new study.

The findings, published in the Journal of Neuroscience, identify some of the brain chemicals that allow the seal brain to remain half awake and asleep.

The latest study could help researchers understand the biological mechanisms that enable the brain to remain alert during waking hours and go off-line during sleep.

"Seals do something biologically amazing -- they sleep with half their brain at a time. 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," Professor John Peever of the University of Toronto said in a university news release.

Researchers made the discovery by measuring how different chemicals change in the sleeping and waking sides of the brain.  They found that an important brain chemical called acetylcholine was at low levels on the sleeping side of the brain but at high levels on the waking side, suggesting that acetylcholine may drive brain alertness on the side that is awake.

Surprisingly, researchers found that another essential brain chemical called serotonin was present in equal levels on both sides of the brain whether the seals were awake or asleep.  Researchers said that the finding is unexpected because the chemical serotonin was long been thought to trigger brain arousal.

Researchers said that the latest findings could 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. It could help solve the mystery of how and why we sleep," researchers wrote in the study.