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Sleep for better learning

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Have you heard the advice that you "remember what you learn better after a good night's sleep?"

This is absolutely true for several reasons: 

First, neuroplasticity - specifically the re-wiring of your neurons, occurs when you are sleeping. This is analogous to how you build muscles 

Second,   the And we found out about this somewhat by accident.

Matt Wilson from MIT was tracking a lab rat while it was going through a maze. The rat was wearing a head sensor, which allowed Wilson to observe the firing patterns of neurons in the rat's brain. When the rat had finished the maze, Wilson removed the rat and left it in a resting area, and went to write a report.

 

Shortly after, he heard the firing of neurons over the speaker - connected to the head sensor. In his rush to start writing, he had forgotten to remove the sensor. 

But to his surprise, he found that the rat was sleeping!

Even in sleep, the neurons were firing. 

Wilson repeated the experiment several times, to compare how the brain worked while awake vs when it as sleeping. And his findings were astounding

|| The rats were replaying the experience of the maze even while they were sleeping!

This is particularly important because as studies have shown, repetition, even if it was just playing the action over and over in our minds, creates neural patterns that are similar to if we were actually performing the action physically. We get better at something through mental imagery as well as actual practice. 

 

How the rats replayed their experience differed across the sleep cycle.

At the start, during the slow-wave cycle, brief segments of the experience were replaying in the hippocampus at very high speeds. Something that was covered in about 4 seconds in real-life was repeated in just 100-200 milliseconds during the slow-wave cycle. Additionally, this replaying during the slow wave cycle only occurs in the period of sleep immediately after the experience. It was not detectable 24 hours later.

(you might wonder how do we actually know that what was replayed in that 100-200 milliseconds is actually what took place in the 4 seconds in real life? The answer is in the pattern of neurons firing. The researchers monitored the firing activity of networks of neurons in each rat's hippocampus as the rat ran on a simple track for a food reward. During each lap, individual brain cells would fire as the animal ran back and forth on the track. Repeated over many times, the researchers then identified a pattern for how the neurons fired, corresponding to the different positions on each lap.)

In the REM cycle of sleep, the experience is replayed in a different way. REM replays are longer, lasting for several minutes at a time. The speed of replaying is also very similar to what happens in real life. Finally, unlike the slow-wave sleep cycle, REM memory reactivation was robust even after 24 hours. represent the more gradual reevaluation of older memories."

What this suggests is that the slow-wave cycle of the sleep is largely invovled in the initial storage and processing of the memory. This is followed by REM cycle where there is renactment of the experience in real speed, which acts as a rehearsal that subsequently improves the level of performance of what was learnt or experienced.

So the old adage is true. Sleep more, remember more, perform better. 

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