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BOB HIRSHON (host):
How the brain falls asleep…I’m Bob Hirshon and this is Science Update.
When you’re very sleepy, it’s with good reason: turns out parts of your brain are already asleep. This according to neurobiologist James Krueger of Washington State University.
JAMES KRUEGER (Washington State University):
Bits and pieces of the brain can be asleep while other parts of the brain can be awake.
He says researchers once thought a master "on/off" switch in the brain controlled sleep. But he and his colleagues have discovered that sleep isn’t a top-down phenomenon. Instead, as groups of brain cells become fatigued after a hard day’s work, they start switching to a sleep state. When enough of them reach this state, we finally lose consciousness. He says this also explains why it can take so long to wake up in the morning.
And we think this is because the neuronal assemblies are coming on line a little bit at a time. One’ll come online but others will remain in a sleeplike state.
I’m Bob Hirshon, for AAAS, the science society.