We all know that when we’re dead tired, a quick cat nap can make all the difference in how we feel. But now a new study says that naps serve a far greater purpose and provide a bigger benefit than in simply leaving us feeling refreshed. Researchers from Saarland University in Germany have just completed a study that revealed that a short nap taken in the middle of the day can have a profound impact on our ability to remember.
The group’s findings were published in the journal Neurobiology of Learning and Memory. Their conclusions indicate that just 45 to 60 minutes of sleep taken during mid-day can improve the brain’s ability to learn and remember material by five times.
It has previously been established that napping improves memory performance: a study reported in January that was conducted by a group of scientist from the University of Sheffield in the United Kingdom indicated that if infant subjects were able to take a half hour nap within four hours of learning a new task, their chances of remembering the task were significantly improved. But this test was conducted n adults, and had a very similar outcome. Study leader Alex Mecklinger of the Experimental Neuropsychology Unit at Saarland worked with a team that recruited 41 study participants to engage in a learning task. They were provided a list of 90 words along with another list of 120 words that were unrelated an in pairs, and asked to learn all of them. In speaking with the study participants, the researchers indicated that the unrelated word pairs were being provided as a control against them remembering the words because of their familiarity. “A word pair might, for example, be ‘milk-taxi.’ Familiarity is of no use here when participants try to remember this word pair,” he explains, “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 being exposed to the words the subjects were asked to take a recall test, and then half of them were asked to take a nap that could go for as long as 90 minutes. The other group watched a DVD. During their naps, the sleeping group was monitored by electroencephalograph for brain activity, with special attention being paid to activities known as sleep spindles. These are bursts of activity that are known to play a role in memory consolidation. “We suspect that certain types of memory content, particularly information that was previously tagged, is preferentially consolidated during this type of brain activity,” Mecklinger explains. The groups were then both asked to take the memory tests again.
The results were quite telling. When comparing those who had spent the time after learning the words watching a DVD to the group that was asked to take a nap, the researchers found that the nappers remembered the new words five times better than the DVD group, and that their scores were very similar to the ones that they achieved immediately after their initial exposure to the words, while the information was fresh in their memories. The conclusion is that a short nap can make a very big difference in associative memory. The team also found that better learning and memory were linked to higher numbers of sleep spindles seen on the subjects’ electroencephalograms.