The Frontal Cortex

Naps, Learning and REM

It’s a shame that we stop encouraging naps once the preschool years are over. After all, there’s a growing body of scientific evidence that the afternoon siesta is an important mental tool, which enhances productivity, learning and memory. (It’s really much more effective than a cup of coffee.) Here’s the Times:

Have to solve a problem? Try taking a nap. But it has to be the right kind of nap — one that includes rapid eye movement, or REM, sleep, the kind that includes dreams.

Researchers led by Sara C. Mednick, an assistant professor of psychiatry at the University of California, San Diego, gave 77 volunteers word-association tests under three before-and-after conditions: spending a day without a nap, napping without REM sleep and napping with REM sleep. Just spending the day away from the problem improved performance; people who stayed awake did a little better on the 5 p.m. session than they had done on the 9 a.m. test. Taking a nap without REM sleep also led to slightly better results. But a nap that included REM sleep resulted in nearly a 40 percent improvement over the pre-nap performance.

The study, published June 8 in The Proceedings of the National Academy of Sciences, found that those who had REM sleep took longer naps than those who napped without REM, but there was no correlation between total sleep time and improved performance. Only REM sleep helped.

Numerous studies have now demonstrated that REM sleep is an essential part of the learning process. Before you can know something, you have to dream about it.

This outlandish notion began with a scared rabbit. In the early 1950s, scientists at UCLA discovered that the rabbit hippocampus, when aroused by some fearful stimulus in its environment (a coyote, for example), would start pulsing with a very distinctive beat, which they dubbed the “theta rhythm.” Subsequent studies found the same beat in several species, but only when the animals were extremely excited or scared or were engaged in an active motor movement. Rats exuded a theta rhythm whenever they were exploring their cage. Cats had it stalking prey. But what was this rhythm’s function? Why did the hippocampus–a brain structure involved in learning and memory–become active in this way during moments of intense awareness? Stumped, the UCLA scientists shelved their work and moved on to other things.

Years later, Case H. Vanderwolf of the University of Western Ontario made an even stranger discovery: Theta rhythm was also present during sleep–activity and rest provoked the same strange brain activity. Nobody could figure out the meaning of this.

The breakthrough came in 1972, when psychologist Jonathan Winson came up with a simple theory: The rabbit brain exhibited the same pattern of activity when it was scared and when it was dreaming because it was dreaming about being scared. The theta rhythm of sleep was just the sound of the mind processing information, sorting through the day’s experiences and looking for any new knowledge that might be important for future survival. They were learning while dreaming, solving problems in their sleep.

Winson’s theory was ridiculed. At the time, most scientists assumed that our dreams were accidents of the brain stem, nothing more than a Dadaist montage of meaningless hallucinations. But Winson maintained that this hypothesis made no sense. For one thing, our dreams don’t seem random. Instead, they unfold in intricate narrative scenarios, which tend to reflect our daily activities. According to Winson, these nighttime stories–that flurry of theta rhythm–were actually carefully scripted events, in which our new knowledge was put to the test. Did our new learning help us solve our invented problems? Was it a good “survival strategy?” If the answer was yes, then the knowledge was woven into the brain. We woke up a smarter person. The rabbit figured out how to escape its predator. We also, therefore, learn by pretending to do.

Whatever the elegance of Winson’s theory, he lacked conclusive evidence. What he needed was a study that directly linked a brain’s real-world experience with its manufactured dreams. That study arrived in 2001, when Matthew Wilson, a professor at MIT, published a paper in Neuron (“Temporally Structured Replay of Awake Hippocampal Ensemble Activity during Rapid Eye Movement Sleep”) about the dreams of rats.

Wilson began his experiment by training rats to run through mazes. While a rat was running through one of these labyrinths, Wilson measured clusters of neurons in the hippocampus with multiple electrodes surgically implanted in its brain. As he’d hypothesized, Wilson found that each maze produced its own pattern of neural firing. To figure out how dreams relate to experience, Wilson recorded input from these same electrodes while the rats were sleeping. The results were astonishing. Of the 45 rat dreams recorded by Wilson, 20 contained an exact replica of the maze they had run earlier that day. The REM sleep was recapitulating experience, allowing the animals to consolidate memory and learn new things. Wilson’s lab has since extended these results, demonstrating that “temporally structured replay” occurs in both the hippocampus and visual cortex.

Comments

  1. #1 NYD
    June 25, 2009

    Does this mean that we can learn through osmosis? Could we not just program our dreams and aquire knowlege without actual experience. Kind of like when athletes utilize their imagination and visualisation to enhance performance.

  2. #2 David Kerlick
    June 25, 2009

    In the 1970s I read an account of a British surgeon(?) in World War I who recounted that soldiers who had made near fatal mistakes dreamed about the situations in trying how to avoid the same mistakes in the future.

  3. #3 Alison
    June 25, 2009

    What about those of us who can’t nap? I generally have to be jet-lagged or sick in order to actually nap. I do have a pretty strong biological clock though; if I don’t get at least 7 hours, I’m a mess the next day. Have there been any studies on naps vs. regular night sleep? And if naps in addition to a good night’s sleep are extra helpful?

  4. #4 Ric
    June 25, 2009

    I just wanted you to know that I thoroughly enjoy this blog.

  5. #5 teiana
    June 25, 2009

    Now i can’t remember where i heard this but i think there is a theory that one reason we are capable of being scared in sleep (nightmares) is to let us rehearse it in a safe environment so we don’t all just have heart attacks when we are scared for real..

  6. #6 catgirl
    June 25, 2009

    So how long do naps have to be to get into the REM sleep?

  7. #7 Turing Machine
    June 25, 2009

    catgirl(post #6),

    Going by the theory (Winson’s) Lehrer mentioned, REM during sleep should have more to do with experiencing something that involved problem solving (while awake) rather than the length of the nap.

    My question regarding M. Wilson’s experiment is: of the 20 rats that showed the same neural activity during sleep, how many performed better the next time they were on that maze?

  8. #8 Thomas Schroeder
    June 25, 2009

    I’ve had similar thoughts on the purpose of dreams so this information helps support my understanding of them. Thanks for sharing, Jonah!

  9. #9 Thomas Schroeder
    June 25, 2009

    ps Thanks to David Kerlick (comment#2) and teiana’s (comment#5) too. You’ve given me more support for my understanding of dreams.

  10. #10 intransigentia
    June 25, 2009

    That totally matches with my experience. When I’ve taken intensive/compressed courses, I’ve had dreams that are, for example, just series of forms and dialog boxes. Or code. Yes, seriously.

  11. #11 Stentor
    June 25, 2009

    I’m in the same boat as Alison. If Iv’e pulled an all-nighter, I can nap the next day, but in any other situation I either just lie there wide awake, or wake up groggier and more disoriented than I ever was pre-nap. So I think now that we’ve got research telling us how naps are awesome, we need research on how to get us to actually be able to nap.

  12. #12 Gustavo
    June 26, 2009

    To Stentor (Comment #11): There are relaxation techniques to train yourself to be able to nap. I’ve had the experience myself, you fall asleep fast and deep, and you wake up feeling fresh and energized. I usually feel groggy and disoriented after a common nap, but if I do it using a relaxation technique the results are 100% different.

    I’ve always heard that sleep enables the brain to “process” the day experiences. I’ve read about research showing that people who are not allowed to sleep can´t remember well what happened in the days preceding the sleepless nights.

  13. #13 nick
    June 26, 2009

    if you drink and nap, does that impair your ability to learn?

    Or do you just have more fun?

  14. #14 Donna B.
    June 26, 2009

    When I first discovered Tetris, I played it as much as I could as often as I could until I started having dreams about playing it.

    That was a wake-up call :-)

  15. #15 Meryl
    June 30, 2009

    These questions may not be directly related to the Topic, nevertheless…

    1) Have studies been done on Lucid Dreaming? This has been practised by Buddhist monks for ages.

    2) How does the experience of Time Flow affect Dreams in general, and in Lucid Dreaming, in particular?

    3) How does Lucid Dreaming and “alterations (if any) made to the dreamer’s psyche” (namely resolutions of thoughts, consolidations of memories, assimilations of experiences, etc)thereof, affect the consciousness when the dreamer is not asleeped.

    In some non-scientific accounts of Lucid Dreaming, the dreamer can affect events, and Time seems to be fluid and at the control of the dreamer.

    I wonder if these types of dreams and such dreamers can be studied under “lab conditions”.

  16. #16 W. Keith Griffith
    July 7, 2009

    Really looking forward to

    “How We Learn”

    Hint,Hint,Hint…..

  17. #17 beautyrest mattress
    November 23, 2009

    Great advice, it will really help me make the most out of my napping time.

  18. #18 Richard
    January 22, 2010

    Great article. I have noticed that I get a better quality nap on my posturepedic bed.

The site is currently under maintenance and will be back shortly. New comments have been disabled during this time, please check back soon.