Researchers in the US found that napping boosts brain power by clearing out the brain’s temporary storage space so it can absorb new information: they also propose that this clearing out process happens during a specific stage of sleep.

Lead investigator Dr Matthew Walker, an assistant professor of psychology at the University of California, Berkeley, presented the preliminary findings of a study he conducted with other colleagues on Sunday, 21st February at the annual meeting of the American Association of the Advancement of Science (AAAS) in San Diego, California.

The researchers found that an hour’s nap can dramatically boost and restore brain power: it not only refreshes the mind, but can make you smarter, they suggest.

Walker told the press that:

“Sleep not only rights the wrong of prolonged wakefulness but, at a neurocognitive level, it moves you beyond where you were before you took a nap.”

For this study, Walker and colleagues recruited 39 healthy young adult volunteers and put them into two groups: a nap group and a no-nap group.

At midday, both groups performed much the same in a challenging task that involved absorbing a lot of facts.

At 2 pm, the volunteers in the nap group took a nap for about 1.5 hours while the no-nap group stayed awake, and then at 6 pm, they underwent a new set of learning exercises.

The results showed that the group that was able to take a nap in the afternoon performed better in the evening exercise than the group that had to stay awake the whole day. And not only did the nap group perform better than the no-nap group, they also performed better than they had earlier in the day, before their nap.

Walker said the findings support the idea that sleep is a necessary process that clears the brain’s short term memory storage so there is room to absorb new information.

The findings are also in line with earlier research by the same team, where they established that working through the night, which is common practice among students facing midterm and final exams, decreases one’s capacity to absorb new facts by nearly 40 per cent due to regions of the brain shutting down as a result of sleep deprivation.

Earlier studies have revealed that the hippocampus temporarily stores fact-based memories before relaying them to the brain’s prefrontal cortex.

Walker likened the process to having an email inbox in your hippocampus. This gets full, and you need to sleep to initiate the clearing out process. Until you do, then the mail stays in the inbox and you can’t take in any more.

“It’s just going to bounce until you sleep and move it into another folder,” said Walker.

Using electroencephalography, a way of measuring the amount of electrical activity in the brain, Walker and colleagues also established that the memory-refreshing process takes place in a stage of sleep known as stage 2 non-REM sleep (non Rapid Eye Movement sleep).

Stage 2 non-REM sleep occurs between deep sleep and REM sleep and nobody really knew what it was for, but now, Walker and colleagues suggest that this is when memory-clearing takes place and may explain why humans spend at least half of their sleeping time in this stage.

The team now want to find out whether there is a link between the reduction in sleep that older people tend to experience and the supposed reduction in learning capacity that occurs as we age.

Finding such a connection could help us better understand neurodegenerative diseases like Alzheimer’s, said Walker.

Source: UC Berkeley.

Written by: Catharine Paddock, PhD