For more than a century, researchers who study sleep have looked for its purpose and structure in the brain.
On the face of it, that might seem improbable. Studies by a team in South Korea and Japan showed that the hydra periodically drops into a rest state that meets the essential criteria for sleep. It does not have a brain, or even much of a nervous system.Īnd yet, new research shows, it sleeps. The foot clings to a surface underwater - a plant or a rock, perhaps - and the mouth, ringed with tentacles, ensnares passing water fleas. Less than half an inch long, its tubular body has a foot at one end and a mouth at the other. This means not just keeping your bedroom dark, but also making sure you get enough light during the day, to reinforce your circadian rhythms.įor those finding it difficult to drop off, rest assured it will always come in the end, says Franks: "The drive is so powerful that sleep is truly inescapable." And far more welcome than death and taxes.The hydra is a simple creature. The second, and most important, is light. The first is temperature: a study in Franks' lab showed having a warm bath before bed induces the brain's circuitry to make you sleepier. Sleep-related neurons aren't just found in commonly associated areas such as the hypothalamus or brainstem, the team found, but are spread throughout the brain.īy better understanding these circuits, the researchers hope to better understand the relationships between sleep malfunctions and conditions such as dementia.Īs for how humans can get a better night's sleep, Franks suggests paying attention to two key variables. The work greatly expanded our knowledge of which brain regions are involved in sleep regulation. They studied the brain activity of mice to find out more about the phenomena at the level of brain circuitry. Like consciousness, it may be difficult to ever know whether all animals sleep-and whether they experience it in the same way we do.įinding the underlying mechanisms for sleepĪs part of the EU-funded DNCSS project, Franks and his colleagues investigated the underlying regulatory mechanisms of sleep. "The question is, are they really getting sleep as we understand it in humans?" It's true that all animals have a period of quiescence each day, Franks remarks, such as moving less. These regulate our sleep patterns, and the effect is even present in blind animals. But that might not be the same for a fly, whose brain is a more passive structure, explains Franks: "The benefit that a fly gets from sleep may be very different to the benefits we get."Īll animals appear to follow circadian rhythms, biological changes based on Earth's 24-hour pattern of light and dark. We know sleep in humans is essential, that it must keep the brain healthy, and that it can't be done while we are conscious. In part this is because of technical issues-you can't measure EEG in flies.Īlso confounding us is the fact that we are still yet to prove what sleep is actually for. Yet extrapolating beyond mammals is fraught with difficulties, he adds. We can safely say that all humans sleep, says Franks, and probably all mammals too, because similar brain patterns and behaviors can be seen using an EEG. And we still don't have a concrete reason why either should exist. Sleep, like consciousness, is a first-person experience. "If I asked you the question, 'are all animals conscious?' what would you say?" Franks likens the two phenomena for two reasons. "It all depends on what you mean by sleep," says Franks, a researcher at Imperial College London.
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