Have a hard time waking up this morning? According to research published today in the journal Nature, maybe that’s because your hypocretin neurons were feeling a bit sluggish.

Hypocretin is a chemical messenger in the brain that’s notably lacking in people with narcolepsy. But so far, its specific role in wakefulness has been unclear. Scientists from Stanford genetically engineered specific neurons within the hypothalamus–a part of the brain that regulates the sleep cycle–to produce more hypocretin when hit with light. (For more on this new technology, see “A Light Switch for the Brain” and “TR10: Neuron Control.”) Specially designed fiber optics were then implanted into the animals’ brains. When genetically engineered animals were exposed to bursts of blue light, they woke up much more quickly than their normal counterparts, suggesting that hypocretin triggers wakefulness.