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Half-Asleep Seals

March 11, 2013

Fur seals sleep with one half of their brain at a time.



Half-asleep seals.  I’m Bob Hirshon and this is Science Update.

When in the water, fur seals sleep with only half of their brain. The other half is awake, with one eye open, scanning for predators.

JENNIFER LAPIERRE (University of Toronto):

And then it will switch.


That’s University of Toronto biologist Jennifer LaPierre. She and her colleagues have figured out how the seals do it. They found that while one side of the brain was awake, levels of a brain chemical called acetylcholine were high. The chemical is thought to be involved in behavioral arousal.


So where we had a high level of brain activity, we had a high level of acetylcholine, so in the waking part of the brain. And the sleeping side of the brain had a low level of acetylcholine.


On land, the seals sleep with both side of their brains, in part because they have more places to hide, and can afford to be totally asleep. She says the research could help illuminate human sleep disorders. I’m Bob Hirshon, for AAAS, the science society.

On land, fur seals sleep like most other mammals - with both sides of their brain. But in the water, only half of their brain falls asleep. (Melon247/Wikipedia)