The Why of Sleep
Brain studies may reveal the purpose of a behavior both basic and mystifying
In a lab at MIT, a small black mouse named Buddy sleeps alone inside a box. A cone resembling a satellite dish sits atop his head. But the dish doesn’t receive signals from outer space. Instead it sends transmissions from deep inside Buddy’s brain to a bank of computers across the room.
Scientists like Jennie Young eavesdrop on the transmissions, essentially reading Buddy’s mind, or at least that part of his mind occupied with a recent trip along a Plexiglas track littered with chocolate sprinkles. Young and her colleagues in Susumu Tonegawa’s laboratory are monitoring nerve cells inside the hippocampus, one of the brain’s most important learning and memory centers. Some of the cells in the sea horse–shaped hippocampus fired bursts of electrical energy as Buddy moved along the track. As he sleeps in his black box, those same cells spark to life again, replaying progress along the track in fast-forward or rapid reverse.