Sleep clears the mind

And speaking of milestones, the Harvard Science in the News Flash – a student written and student edited writing series just posted their 100th article:

Sleep clears the mind: How sleep prepares the brain for new learning

Despite the fact that sleep is essential to our health, its function and what makes it necessary have remained mysterious. Over the years, scientists have accumulated data showing that sleep, or the lack thereof, affects the brain. Most of this work focused on the idea that sleep is important for consolidating newly formed memories. However, evidence is now building that sleep also makes room for the formation of new memories, acting as a sort of “spring cleaning” for the brain. The idea that sleep may help balance brain resources and space is known as the homeostatic theory of sleep. While you are awake, your brain is constantly exposed to new information coming in from your senses. This information allows you to form new memories and learn about the world around you. Interacting with the environment also causes changes in your brain – its cells branch and grow, and new connections are formed between them. These changes require energy as well as physical space, both of which are limited.

The website is a bit ugly (I’ve been assured that there are folks working on that), and there’s a link on the left to my first (now defunct) attempt at science blogging (lesson learned: never try to blog by committee, even the name is terrible). But the Flash articles are usually well written, always well researched and provide a great avenue for students interested in science writing to get a crack at it (while getting some expert feedback from a talented list of student editors). Give it a read, and leave some feedback if you’re willing.

For more on the neuroscience of sleep, check out the always fabulous Radiolab.


  1. #1 Adam K
    September 7, 2011

    I think that dreaming is sometimes a form ‘analysing’ new information by our brain when we’re unconscious.

  2. #2 Elizabeth Munroz
    September 8, 2011

    Grandmother used to say that sleep is healing, so when one is sick they need to rest. Is there any evidence that the immune system works more efficiently if a person gets adequate sleep? or less efficiently if not. would a sleep deprived person be more likely to be susceptible to colds and flu, for example?

  3. #3 Kevin
    September 9, 2011

    @ Elizabeth – It’s known that stress suppresses the immune system, and that sleep deprivation causes stress. Also, there have been a number of studies showing that sleep deprivation can disrupt the immune system in a number of ways. I found one review that said:

    Significant detrimental effects on immune functioning can be seen after a few days of total sleep deprivation or even several days of partial sleep deprivation.

    So the short answer to both of your questions is “yes.”

  4. #4 Belphegor
    September 12, 2011

    Oh well, sometimes I feel that “spring cleaning” more than I wished. In the exam time, for example. 🙂

  5. #5 Andrew
    September 28, 2011

    You stated that sleep does Spring cleaning to the mind. There is an old wives tale that states, “Too much sleep is bad for your mind.” I was wondering if this is really true and if so what would be the right amount to “Clear the mind”. If this wives tale is not true I am curious why. Furthermore I found your article fascinating, I was unaware that your brain actually makes room from sleep. I also am curious how they would test this? What would a simplistic version of your lab look like?

  6. #6 Katy W
    September 30, 2011

    For a long time, I’ve thought that sleeping is a pretty useless thing. It’s was almost frustrating to me that human beings spend about a third of their day doing absolutely nothing. It didn’t make sense to why humans needed to do this so often when all it did was waste time. The idea that sleeping actually has an important purpose to offer in that it consolidates memories and clears up room in the brain for more information helps me to understand why humans have a need for sleep.

  7. #7 Kevin
    September 30, 2011

    @ Andrew – I didn’t write this piece, and I don’t study sleep myself, so I’m not entirely sure what experiments are done to figure this stuff out. I think they might talk about it in that radiolab episode I linked to though.

    @ Katy – I think the best argument that sleep does something is that we haven’t evolved to not do it. Sleep is dangerous, and as you say, seems wasteful in terms of the 3 F’s, so if evolution could figure out a way to not do it, it seems like it would have.

  8. #8 Alyssa
    September 30, 2011

    First of all I don’t think humans will evolve away from sleep. All species sleep, and as the article says it’s important. We physically need sleep to be able to understand our environment. Although is sleep really like “spring cleaning”? I thought our minds were incapable of creating new brain cells or is that a myth? Furthermore what happens to the information that is “pruned”? Information can’t just disappear, does the brain recycle the chemicals so it can hold a new memory? I find it amazing that your body can do so much even while you’re sleeping.

  9. #9 Kevin
    October 1, 2011

    @ Alyssa – The information in our brains is not stored in Neurons, it’s stored in the connections between neurons. So it’s not actual cells being created or destroyed, it’s synapses.

    As for the chemicals – yes they are constantly being recycled. When a neuron sends a signal, it releases a bunch of neurotransmitters (which are just chemicals), and then reabsorbs them to get ready to send another signal.

  10. #10 Maxine
    December 23, 2011

    This was very refreshing. The blog post was simple and easy to understand. I spent multiple 90-minute classes learning about sleep and how it helps the brain. It is so important! The most fascinating thing in this article, was the fruit fly experiment! I’m so baffled at how we learned about human brains from a fruit fly, such a tiny creature! The part that referred to enriching environments, and how that helps the brain, has to do with neurogenesis. Those types of environments allow the brain to grow new neural connections and make new pathways. Then, when we go to sleep, our brain goes through and gets rid of the unnecessary connections we made. I love learning about sleep and the brain, so this post was very interesting!

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