Mind & Body

Sleep Helps Your Brain Forget Unnecessary Memories

For something so simple and so universal, sleep has long baffled scientists. We still don't really know why virtually every higher-order animal spends about a third of their day curled up with their eyes closed instead of doing something more productive, like hunting or running an Etsy shop. But researchers have recently discovered that sleep is necessary for the brain to perform an essential task: forgetting everything it learned during the day that it doesn't need to remember for tomorrow.

How Memories Build Up In The Brain

All day long, your brain is busy gathering data and growing synapses in order to access that data. And we do mean all day long. Everything you experience gets logged and archived, from the important project your boss assigned you to what sandwich is on special at the local deli. When that data gets logged, your brain sprouts a new synapse to the neuron cluster the contains that information. But just because that information is there, that doesn't mean it's doing anything useful. It might just be taking up space—or worse, interfering with other memories and causing you to call Tonya "Tawny" by accident. That's why it's important for your brain to evaluate the important memories, and clear out the rest.

Pruning Your Brain's Branches

According to a pair of studies published in Science, sleep is when the majority of this pruning takes place. In fact, it might be the one of the main reasons why we do it. The first found that, during sleep, the synapses of mice would undergo numerous changes, including some that left them weakened and inaccessible. The second study went a bit further, noting that the targeted synapses were the smaller, weaker ones, and suggesting that this process might be a core function of sleep. It all adds up to a brain that won't accidentally prioritize a reuben on rye over the big work project—assuming that's where your priorities lie (we prefer the sandwich, personally).

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Written by Reuben Westmaas March 30, 2017

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