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This is Scientific American's 60-Second Science. I'm Adam Hinterthuer. Got a minute?

If you're too tired to think straight, it might be because parts of your brain are already asleep at the wheel. A team of neuroscientists from Washington State University is challenging the belief that a specific region of the brain makes the call to hit the sack. Instead, our brains power down in stages, the researchers say. If a certain group of cells in our brain gets fatigued¹, it simply shuts off. Surrounding areas respond in kind and also begin to doze². Once a critical mass of gray matter reaches this point, our brain calls it a day. The research will appear in the December issue of the journal Nature Reviews Neuroscience.

According to the paper, a centralized sleep command center can't account for behaviors like sleepwalking and "sleep inertia," or the sluggishness³ we feel when we first wake up. In those cases, parts of our brain are obviously awake while others are fast asleep. All this suggests that regions of our brain can make their own decisions about wakefulness. So next time your partner wants to talk at bedtime and asks "Are you asleep?" don't worry about saying yes. Truth is, part of your brain is probably already snoring.

Thanks for the minute for Scientific American's 60-Second Science. I'm Adam Hinterthuer.