The Beacon

Seals Sleep with Only Half of Their Brain at a Time

Hey sleepyhead. Photo: Wikimedia Commons

If you've ever seen a clip of a seal being ambushed by a great white you might understand why they only sleep with one half of their brain at a time. With enemies like The Man in the Gray Suit it's always advisable to maintain at least a marginal degree of 'round-the-clock alertness.

A new study led by scientists at UCLA and the University of Toronto, and published in the February Journal of Neuroscience, investigated this phenomenon of half-brain sleeping.

"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," said Professor John Peever of the University of Toronto.

The researchers found higher levels of an important brain chemical, acetylcholine, in the waking halves of the seal brains than the sleeping halves. The discovery could aid in the understanding of human sleep disorders, the study's senior author Jerome Siegel of UCLA's Brain Research Institute claims.

"About 40% 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."

Sleep tight seals, and don't let the great white sharks bite.

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