Mark Zielinski knew he was onto something when his mice stopped sleeping. Normally, the animals woke and slept on a 12-hour cycle. When the lights were on in the lab, the mice were active. When it went dark on a timer, down they went. But Zielinski, who teaches psychiatry at Harvard Medical School, had recently tweaked their schedule to keep the mice up past their bedtime.
Zielinski and his colleagues would rustle the bedding in the mice's cages to keep them from dozing off when they started to display the telltale signs of sleepiness--drooping lids, sluggish walk, EEG readings showing their brain activity was waning. But Zielinski noticed that when the mice were left alone to slumber at will after the disruption, they didn't, or perhaps couldn't, fall asleep.
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