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Reddit is a great forum for raising scientific questions, but the fact that it\u2019s discussion-based makes it difficult to know when a debate has settled on the best answer, objectively speaking. Exhibit A concerns the value of lying down with your eyes closed. How much does it do for you compared to actual sleep? The whole exercise can seem like a waste. Is it?<\/p>\n\n\n\n
Part of what makes this question so slippery is that it hinges in large part on the matter of what sleep is actually for. We can all name the benefits of sleep, but saying what sleep accomplishes is a far cry from identifying what sleep is meant to do. The distinction is important. If the point of sleep is that being inactive frees up our energy for other tasks (say, recovering from a cold), we might expect lying in bed with our eyes closed\u2014what some studies call \u201cquiet wakefulness\u201d\u2014to accomplish much the same thing.<\/p>\n\n\n\n
Researchers are growing increasingly confident, though, that sleep evolved specifically to recharge the brain. Dr. Chiara Cirelli, a neuroscientist at the University of Wisconsin, has been studying the difference between sleep and quiet wake in humans. She says that while we\u2019re awake, all of our neurons are constantly firing, but that when we\u2019re asleep, the neurons revert to an \u201cup-and-down\u201d state in which only some are active at a given time. During some stages of sleep, all neuron activity goes silent. And that\u2019s likely when the restful part of sleep takes place.<\/p>\n\n\n\n
\u201cThis period of silence and hyperpolarization of the cell membrane is probably related to the restorative function of sleep,\u201d Cirelli told me. \u201cThe fact that there are these periods of total silence, that\u2019s very typical and unique of sleep relative to wake and there might be something related to that.\u201d<\/p>\n\n\n\n
To understand the value of total neural silence, let\u2019s look at another kind of sleeping animal\u2014dolphins. Dolphins, along with whales, some sharks, and a variety of other underwater critters, need to stay moving to breathe. It follows that these animals can\u2019t go completely unconscious like humans can\u2014otherwise, the dolphins couldn\u2019t come up for air, and oxygenated water would stop flowing over the sharks\u2019 gills. And the research seems to bear that out: Brain scans show that dolphins never go into a full sleep state; instead, they turn off half of their brain for about eight hours a day, leaving the other half alert. This kind of rest has come to be called \u201cunihemispheric sleeping.\u201d<\/p>\n\n\n\n
The closest humans ever get to unihemispheric sleep is when a person who\u2019s extremely sleep-deprived shows signs of what Cirelli calls \u201clocal sleep in wake,\u201d in which a few neurons turn off by themselves. The effect is unnoticeable from the outside, because the sleep-deprived subject is still awake and moving, but researchers are able to record the changes using deep-scanning technology that measures individual neurons.<\/p>\n\n\n\n
But it\u2019s not until we get access to real, deep sleep that we get a cognitive boost from rest. In other studies, test subjects who were made to identify letters flashed on a screen for several hundred milliseconds at a time generally did worse at the exam over the course of a day. Those who got to take a nap halfway through showed more cognitive recovery than those who simply rested quietly, suggesting that there\u2019s a unique benefit to sleep that you don\u2019t get with quiet wakefulness, microsleep, or unihemispheric sleep.<\/p>\n\n\n\n
\u201cThis function is only happening when there is a real nap with real sleep as measured with EEG,\u201d Cirelli said.<\/p>\n\n\n\n
Lying down isn\u2019t completely useless\u2014it does help your muscles and other organs relax. But you\u2019d get the same results just from reclining on the couch. So sleep is still your best friend.<\/p>\n\n\n\n
The useful takeaway is that your best move, if you\u2019ve been in bed for 20 minutes and still aren\u2019t dozing off, is to get up and engage in a low-light, low-stress activity like reading until you begin to feel tired. Taking your mind off of Why am I not sleeping?! I need to sleep! is crucial. When you do get up, though, don\u2019t use your computer or phone or watch TV\u2014the blue-colored light from the screens tricks your body into thinking it\u2019s daytime and not releasing melatonin. Sweet, sweet melatonin.<\/p>\n\n\n\n