Brief sleep can significantly improve retention of learned material in memory, according to a recent study.

Researchers at Saarland University in Germany found that even a short sleep lasting 45 to 60 minutes produces a five-fold improvement in information retrieval from memory.

For the study, researchers split participants into two groups: The nap group and the control group.

They found that the control group, whose members watched DVDs while the other group slept, performed significantly worse than the nap group when it came to remembering the word pairs. The memory performance of the participants who had a power nap was just as good as it was before sleeping, that is, immediately after completing the learning phase.

The researchers were particularly focused on the role of the hippocampus -- a region of the brain in which memories are "consolidated" -- the process by which previously learned information is transferred into long-term memory storage.

"We examined a particular type of brain activity, known as "sleep spindles," that plays an important role in memory consolidation during sleep," researcher Sara Studte explained. A sleep spindle is a short burst of rapid oscillations in the electroencephalogram (EEG).

"We suspect that certain types of memory content, particularly information that was previously tagged, is preferentially consolidated during this type of brain activity," Axel Mecklinger. Newly learned information is effectively given a label, making it easier to recall that information at some later time. In short, a person's memory of something is stronger, the greater the number of sleep spindles appearing in the EEG.

In order to exclude the possibility that the participants only recall the learned items due to a feeling of familiarity, the researchers used the following trick: the test subjects were required to learn not only 90 single words, but also 120 word pairs, where the word pairs were essentially meaningless.

The findings are detailed in the journal Neurobiology of Learning and Memory