— Sleep deprivation can severely hamper the brains ability to learn, a new study demonstrates.
The experiment showed that people who fail to get a good nights sleep before studying new information remember roughly 10% less than their well-rested counterparts. The researchers say it is a worrying finding considering the average amount of sleep people get each night is decreasing.
Seung-Schik Yoo at Harvard Medical School in Boston, Massachusetts, US, and colleagues asked 14 people to avoid sleeping one night by playing board games and checking email in the lab. The participants stayed awake until the next evening, when they had to view a sequence of 150 images as their brains were scanned before going home to sleep.
After two good nights rest, the participants returned to the lab thinking they would simply have to sign some papers. But researchers surprised them with a pop quiz: The subjects had to pick out the 150 images they had seen before from a series of 225 pictures.
They correctly identified 74% of the previously viewed images, on average. By comparison, another group who had a proper nights rest before viewing the 150 images at the start of the experiment correctly identified 86% of these pictures in the pop quiz.
Brain images captured by an fMRI scanner when the test subjects had first viewed the pictures indicate that sleep deprivation diminishes activity in the hippocampus, a brain region involved in memory processing. This study shows that the brain has to be well rested to receive and store information for memory processing, says Yoo.
Studies in rats have shown that sleep deprivation can increase levels of stress hormone in the brain, which subsequently disrupts nerve activity in the hippocampus (see Cant remember what you just read? Take a nap). Yoo says it could be possible that a similar mechanism causes memory deficits in sleep-deprived humans.
Previous studies have also shown that a full nights rest after studying can improve learning. But Yoo says his new experiment is the first to demonstrate the importance of sleeping well before studying new information.
How many hours of sleep is good enough? We dont have the answer to that yet, he adds.
Journal reference: Nature Neuroscience (DOI: 10.1038/nn1851)