This post was written by Sara E. Alger, a postdoctoral research fellow with a doctorate in Cognitive Neuroscience. She is currently conducting research in the Sleep, Stress, and Memory Lab at the University of Notre Dame. Her research is focused on examining how daytime naps can impact the formation and storage of emotionally charged memories and whether this may change with age.
Ever heard the phrase you snooze, you lose? It couldn’t be further from the truth. Napping might carry the stigma of laziness, but what many don’t realize is that your brain is hard at work during your siesta. There are many reasons to take a nap, such as making up sleep debt from shortened overnight sleep, preparing for an upcoming loss of sleep, or getting a little extra sleep for a boost of energy. A 20-minute nap can improve alertness, mood, and performance. However, a nap that is a little longer (30-90 minutes) can allow your brain to reach the stages of sleep that are thought to facilitate memory consolidation, creativity, and emotion regulation. Adding a nap to your regular study routine which already includes Brainscape smart flashcards, of course, could be the key to your learning!
30-60 Minute Naps
When taking a nap that’s around an hour, your brain progresses through the lighter stages of sleep, Stages 1 and 2, and enters slow wave sleep (SWS), also considered your deep sleep. It is thought that declarative memories, or memories of your personal experiences and learned facts, benefit from this type of sleep, which helps in taking short-term memories to long-term storage. While a very brief nap (6-10 minutes), compared to remaining awake, may temporarily preserve memory (Lahl et al., 2008), a longer nap that gets into SWS (30-60 minutes) is needed to keep memories around for a while and to protect them from interfering information (Alger et al., 2012). In fact, the longer you are awake during the day, the more SWS you will get when you fall asleep, and naps in the afternoon may benefit these memories the best (Alger et al., 2010).
60-90 Minute Naps
Longer naps (60-90 minutes) allow the brain to progress further into sleep, transitioning from SWS into rapid eye movement (REM) sleep. This type of sleep may benefit memories that provoke an emotional response because of the connectivity between memory and emotion centers of the brain during this stage. REM sleep has been positively correlated with memory for emotional information, which is typically better remembered than neutral information (Nishida et al., 2009).
Naps and Creativity
Napping has also been found to boost creativity by allowing connections to form between related items, promoting the abstraction of embedded rules and lists common to learned items, and facilitating the integration of new information into old (Cai et al., 2009; Payne et al., 2009; Lau et al., 2010, 2011). These types of memory transformation allow a more flexible use of learned information that informs future decision-making.
Regulating Your Emotions
Aside from everything a little snooze can do for your memory, it can also improve the way you emotionally react to the world. Who doesn’t feel cranky when tired? That crankiness may cause you to view the world in a more negative light, and most likely get negativity back in return. A daytime nap, especially one with REM sleep, has been shown to reduce negative reactivity and promote a happier outlook, compared to remaining awake and feeling increased reactivity, particularly to threat-related stimuli (Gujar et al., 2010). This reduced emotional reactivity even extends to physiological responses, with habituation to negative images occurring over approximately 90 minutes of napping (Pace-Schott et al., 2011).
There are a couple caveats to longer daytime napping. Waking up from deep SWS or REM sleep can result in a feeling of grogginess and disorientation, called sleep inertia. However, this should pass in no more than 30 minutes. Also, while napping in the afternoon may have more of that memory promoting SWS, napping late in the afternoon or early evening can disrupt your normal overnight sleep, so don’t push it too late. Finally, napping works best for you if you can make it a habit, incorporating it into your routine. However, even if this is not possible, the benefits of an occasional nap are well worth it.
Alger, S. E., Lau, H., & Fishbein, W. (2010). Delayed onset of a daytime nap facilitates retention of declarative memory. PLoS ONE 5(8): e12131. doi:10.1371/journal.pone.0012131
Alger, S. E., Lau, H., & Fishbein, W. (2012). Slow wave sleep during a daytime nap is necessary for protection from subsequent interference and long-term retention. Neurobiology of Learning and Memory, 98, 188-196. http://dx.doi.org/10.1016/j.nlm.2012.06.003
Cai, D. J., Mednick, S. A., Harrison, E. M., Kanady, J. C., & Mednick, S. C. (2009). REM, not incubation, improves creativity by priming associative networks. Proceedings of the National Academy of Sciences, 106(25), 10130-10134.
Gujar, N., McDonald, S. A., Nishida, M., & Walker, M. P. (2010). A role for REM sleep in recalibrating the sensitivity of the human brain to specific emotions. Cerebral Cortex, bhq064.
Lahl, O., Wispel, C., Willigens, B., & Pietrowsky, R. (2008). An ultra short episode of sleep is sufficient to promote declarative memory performance. Journal of Sleep Research; 17, 3-10.
Lau, H., Tucker, M. A., Fishbein, W. (2010). Daytime napping: Effects on human direct associative and relational memory. Neurobiology of Learning and Memory; 93(4), 554-60.
Lau, H., Alger, S. E., & Fishbein, W. (2011). Relational memory: A daytime nap facilitates the abstraction of general concepts. PLoS ONE 6(11): e27139. doi:10.1371/journal.pone.0027139
Nishida, M., Pearsall, J., Buckner, R. L., & Walker, M. P. (2009). REM sleep, prefrontal theta, and the consolidation of human emotional memory. Cerebral Cortex; 19, 1158-1166.
Pace-Schott, E. F., Shepherd, E., Spencer, R., Marcello, M., Tucker, M., Propper, R. E., & Stickgold, R. (2011). Napping promotes inter-session habituation to emotional stimuli. Neurobiology of Learning and Memory, 95(1), 24-36.
Payne, J. D., Schacter, D. L., Propper, R. E., Huang, L. W., Wamsley, E. J., Tucker, M. A., & Stickgold, R. (2009). The role of sleep in false memory formation. Neurobiology of Learning and Memory, 92(3), 327-334.
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