Whether you’re cramming for an exam, or trying to learn a new musical instrument, or even trying to perfect a new sport, sleep may actually be your secret memory weapon.

Studies have actually told us that sleep is critical for memory in at least three different ways.

First, we know that you need sleep before learning to actually get your brain ready, almost like a dry sponge, ready to initially soak up new information. And without sleep, the memory circuits within the brain effectively become waterlogged, as it were, and we can’t absorb new information. We can’t effectively lay down those new memory traces.

But it’s not only important that you sleep before learning, because we also know that you need sleep after learning to essentially hit the save button on those new memories so that we don’t forget. In fact, sleep will actually future-proof that information within the brain, cementing those memories into the architecture of those neural networks. And we’ve begun to discover exactly how sleep achieves this memory-consolidation benefit.

The first mechanism is a file-transfer process. And here, we can speak about two different structures within the brain. The first is called the hippocampus and the hippocampus sits on the left and the right side of your brain. And you can think of the hippocampus almost like the informational inbox of your brain. It’s very good at receiving new memory files and holding onto them. The second structure that we can speak about is called the cortex. This wrinkled massive tissue that sits on top of your brain. And during deep sleep, there is this file-transfer mechanism. Think of the hippocampus like a USB stick and your cortex like the hard drive. And during the day, we’re going around and we’re gathering lots of files, but then during deep sleep at night, because of that limited storage capacity, we have to transfer those files from the hippocampus over to the hard drive of the brain, the cortex. And that’s exactly one of the mechanisms that deep sleep seems to provide.

But there’s another mechanism that we’ve become aware of that helps cement those memories into the brain. And it’s called replay. Several years ago, scientists were looking at how rats learned as they would run around a maze. And they were recording the activity in the memory centers of these rats. And as the rat was running around the maze, different brain cells would code different parts of the maze. And so if you added a tone to each one of the brain cells, what you would hear as the rat was starting to learn the maze was the signature of that memory. So it would sound a little bit like... (Bouncy piano music) It was this signature of learning that we could hear.

But then they did something clever. They kept listening to the brain as these rats fell asleep, and what they heard was remarkable. The rat, as it was sleeping, started to replay that same memory signature. But now it started to replay it almost 10 times faster than it was doing when it was awake. So now instead you would start to hear... (Fast bouncy piano music) That seems to be the second way in which sleep can actually strengthen these memories. Sleep is actually replaying and scoring those memories into a new circuit within the brain, strengthening that memory representation.

The final way in which sleep is beneficial for memory is integration and association. In fact, we’re now learning that sleep is much more intelligent than we ever imagined. Sleep doesn’t just simply strengthen individual memories; sleep will actually cleverly interconnect new memories together. And as a consequence, you can wake up the next day with a revised mind-wide web of associations, we can come up with solutions to previously impenetrable problems. And this is probably the reason that you’ve never been told to stay awake on a problem. Instead, you’re told to sleep on a problem, and that’s exactly what the science is teaching us.