Since arriving in Paris I have immersed myself in a lesser-known aspect of French culture – Naps.
While not as famous as the country’s delicious food and fine wine, the French nap, particularly when enjoyed on the banks of the Seine River or on a bus ride through Loire Valley, is a key part of the French lifestyle. In fact, napping is so important to the French that recently their minister of health, Xavier Betrand proposed that they schedule Spanish-esque siestas into the normal workday to increase napping-opportunities. He even suggested that these siestas count as paid work hours!
So, with much determination, I have subjected myself to a grueling routine of daily naps, often conveniently located at some of Paris’s most beautiful landmarks. But unfortunately this napping regime takes time, and since I’m not receiving health minister Betrand’s proposed nap-time monetary reimbursement, I needed to do some research to see if my dedication to the French culture was worth the time away from my neuroscience studies.
It turns out that napping could very well be helping my academics! There have actually been many research studies that show significant increases in ability of individuals to remember facts when they take a brief nap after learning new information.
So what is a nap?
In order to understand the research behind nap-improved memory, it’s important first that we briefly define different sleep stages, and the different types of naps associated with each.
Non-Rapid Eye Movement Sleep (NREM): NREM sleep is comprised of 4 stages. Stage N1 is the drowsy period right at the onset of sleep. N1 is often associated with body twitches and the ability to still be somewhat aware of your surroundings. The second stage, N2, is when your muscles relax and you lose all awareness of your surroundings. This stage occupies about 40% of total sleep time. The final two stages of NREM, N3 and N4, are the deepest sleep stages and are often termed slow-wave-sleep because of their distinct shape when recorded on a electrocephologram (a machine used to measure electrical activity in the brain).
Rapid Eye Movement Sleep (REM): As the name suggest this sleep is often accompanied by rapid eye movements. Additionally, when you wake yourself up by kicking or swinging your arm it most likely occurred during REM sleep.
Long Naps: Naps that last longer than 40 minutes. Includes all stages of NREM and REM sleep. Because long naps include deep sleep phases, they are often associated with sleep inertia upon waking (the groggy-feeling where it’s difficult to get fully awake).
Short Naps: Naps between 10-40 minutes. Commonly called “power naps,” these naps normally just include stages N1 and N2, however they can include N3 if approaching 40 minutes in length.
Ultra Short Naps: These are naps as short as 5 minutes and normally are just stage N1.
The science behind the French-nap
Since sleeping between class or on a bench amongst the hubbub of tourists and street vendors doesn’t lend itself well to long naps, the majority of my sleep has been limited to 6-40 minute intervals. Interestingly, there was a study recently published in the Jounral of Sleep Research that looked at this exact length of nap and it’s effect on the ability of 18 college-age individuals to remember a list of words (Lahl et al., 2008).
The study was pretty simple, each student was given a list of thirty adjectives and told to memorize as many of them as possible. At the end of two minutes the lists were taken away and the students were broken up into 3 sleep-groups. One group was allowed to sleep for 5 minutes, another for an average of 35 minutes, and a third was not allowed to sleep at all. After 60 minutes, each student was asked to repeat the adjectives they could recall from the list. The number they remembered was recorded and averaged with the other’s in their sleep-group. This experiment was done twice more with the same students, once a week after the first test, and then again another week later. To make sure the experiment was accurate they used different word lists each time and also rotated which group slept for 6 min, 35 min, or not at all. By the end of the experiment each student had been in each sleep-group once.
The results of this experiment are great news for the French-nap! It turns out that those who took a short nap were able to remember on average 1.2 more words than those who didn’t sleep at all and students who took long naps where able to remember an average of 2.2 more words than their non-sleeping peers. While 1-2 words might not seam like a huge difference, it is considered statistically significant because of the small number of total words in each list (30 words). Also, many other sleep-memory experiments have shown similar results thus helping to confirm the data from this study (Tucker et al., 2006).
Some additional experiments have been done to show exactly how this memory-improvement occurs. When you sleep, your brain doesn’t “shut-down” like many people believe; instead parts of the brain ramp up their activity. One of these areas, the hippocampus, has been shown to be a key part of the memory-forming networks in the brain (Gorfine et al., 2007). Increasing the activity of the hippocampus during sleep is a way for our brains to rehearse the events we recently experienced, thus strengthening the connections between neurons that solidify those memories in our brain. Short bursts of sleep, such as my French-naps, are thought to specifically help in the formation of factual memories. Additional research has shown that another part of the brain, the orbitofrontalcortex, might help the hippocampus in the formation and storage of these memories (Lesburgures et al., 2011). However, this research is very recent and the connection between sleeping and its effect on the orbitofrontalcortex needs to be studied in future experiments. Until then, I’m happy to know that I now have a scientifically proven excuse to nap across Paris – I’m activating my hippocampus and helping store all of the material learned in class that day. Next stop, a nap beneath the Eiffel tower!
– Camden MacDowell
Gorfine T, Yeshurun Y, Zisapel N (2007) Nap and melatonin-induced changes in hippocampal activation and their role in verbal memory consolidation. Journal Pineal Research 43: 336-342.
Lahl O, Pietrowsky P, Wispel C, Willigens B (2008) An ultra short episode of sleep is sufficient to promote declarative memory performance. Journal of Sleep Research 17: 3-10.
Lesburgures E, Alaux-Cantin O, Bontempi B, Gobbo A, Hambucken A, Trifilieff P (2011) Early tagging of cortical networks is required for the formation of enduring associative memory. Science 331, 924-928.
Tucker M., Chaklader A, Fishbein W, Hirota Y, Lau H, Warnseley E (2006) A daytime nap containing solely non-REM sleep enhances declarative but not procedural memory. Neurobiology of Learning and Memory 86: 241-247