Each of us has an internal clock that tells us when to sleep and when to stay awake. Fruit flies have these clocks too, and they respond keenly to food. A full belly makes you sleepy, while hunger drives you to search for food. For a long time, scientists didn't know exactly how food controls these clocks. Now they have found the answer.
It's like a radio where you turn the volume knob rather than resolder the antenna. When a fly is put on a poor diet, it sleeps less and worse. But if you give it normal food back, everything recovers within four hours. The wiring between the cells doesn't change; only the sensitivity does.
Scientists tested this in both larvae and adult flies. It turned out that the mechanism is the same. This means that nature has found a simple and reliable way to link sleep to nutrition throughout life. Perhaps in humans, similar processes explain why malnutrition in childhood can affect sleep and memory for a lifetime. For now this is only a hypothesis, but it points the way for future research.
A Drosophila larva needs just four hours on normal food to restore the daily sleep rhythm it had completely lost on the poor diet. And the synaptic contacts between clock and arousal neurons never appear: the signal travels "through the air," via a neuropeptide.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.