A short daytime nap could improve memory by fivefold

We have all been there; whether in class at school or a meeting at work, sometimes it feels as if our brain just gives up and leaves the building. But according to a new study by researchers from Saarland University in Germany, a short daytime nap could significantly boost brain power.

A daytime nap of around 45-60 minutes could improve learning and memory by fivefold, researchers suggest.

Publishing their findings in the journal Neurobiology of Learning and Memory, the team reveals that a sleep of around 45-60 minutes could improve learning and memory by fivefold.

This is not the first study to associate daytime napping with improved memory performance. 

Recently, we heard of a report on a study by researchers from the University of Sheffield in the UK, who found that a 30-minute nap within 4 hours of a learning task significantly improved infants' memory.

But this latest study reveals that power naps may also benefit memory for adults, with the team revealing how a short sleep may affect the brain to produce this outcome.

To reach their findings, study leader Alex Mecklinger, of the Experimental Neuropsychology Unit at Saarland, and his team enrolled 41 participants to take part in a learning task.

Participants were shown a list of 90 single words and 120 unrelated word pairs and were asked to learn them. The researchers explain that unrelated word pairs were used in order to eliminate the possibility that participants may have remembered the words as a result of familiarity.

A word pair might, for example, be 'milk-taxi.' Familiarity is of no use here when participants try to remember this word pair, because they have never heard this particular word combination before and it is essentially without meaning. They therefore need to access the specific memory of the corresponding episode in the hippocampus.

After the learning task, participants were immediately required to complete a memory recall test. Half of the participants were then asked to take a nap of up to 90 minutes, while the remaining subjects were asked to watch a DVD.

The brain activity of the napping participants was measured via electroencephalogram (EEG) while they slept, with the team specifically focusing on "sleep spindles" - a burst of activity in the hippocampus region that plays a key role in memory consolidation.

The researchers suspect that certain types of memory content, particularly information that was previously tagged, is preferentially consolidated during this type of brain activity.

Next, all participants were asked to retake the memory recall test, requiring them to once again remember the words and word pairs shown to them prior to napping or watching a DVD.

Better learning, memory linked to greater number of sleep spindles during nap

The researchers found that, compared with participants who watched the DVD, those who napped for around 45-60 minutes following the learning task performed approximately five times better when it came to remembering the word pairs.

In fact, the researchers note that word pair recall of the napping participants was just as good as it was on the memory tests completed immediately after learning.

Short naps were not associated with improvement in item memory - the ability to remember phone numbers, for example, or a friend's name - the research team says.

According to the researchers, these findings suggest that a short nap can significantly boost associative memory - the ability to remember a link between items that are unrelated, such as the name of a person we have just met.

What is more, the team found that better learning and memory recall was associated with a greater number of sleep spindles in the EEG, supporting their theory that sleep spindles play a role in specific forms of memory; in this case - associative memory.

"A short nap at the office or in school is enough to significantly improve learning success. Wherever people are in a learning environment, we should think seriously about the positive effects of sleep."

References:

1.  Nap sleep preserves associative but not item memory performance, Alex Mecklinger, et al., Neurobiology of Learning and Memory, doi:10.1016/j.nlm.2015.02.012, published online 27 February 2015, abstract.
2.  Saarland University news release, accessed 23 March 2014.