It’s long been known that the brain needs sleep to learn. Sleep has been shown to help the brain consolidate memories after cramming, and even to prime the brain to learn better beforehand. Now a new study looks at how sleep affects learning when the brain knows it will be tested.
The study was conducted by German researchers and looked at how sleep selects the memories that will be stored for later retrieval. They found that while sleep helps the brain to retain information, this technique works even better when the brain knows it will tested on that material later. (More on TIME.com: Can’t Sleep? It May Help to Get Out of Bed)
The Los Angeles Times reported on the study published in the Journal of Neuroscience:
A group of German researchers set about exploring how sleep selects the memories it will package up and store for later retrieval. Some 193 study participants were put through their paces at learning tasks including finger-tapping sequences, card-pair locations and lists of matched words, and then either told they would be tested later on the material or not. Some subjects were exposed to the material early in the day, when there would be no sleep involved. Others were exposed to the material just before nighttime sleep.
The researchers found that participants who were told they would be tested later were more likely to remember the tasks accurately if they had slept after being exposed to the material than if they stayed awake. Researchers also found that participants who knew they would be tested spent more of their sleep time in Stage 4 sleep, the deepest form, compared to those who weren’t expected a test. Those who showed more distinctive Stage 4 sleep patterns remembered their tasks best. (More on TIME.com: More Weekend Sleep Cuts Kids’ Obesity Risk)
So while it might seem difficult to rest easy the night before a test, your performance may depend on it.