By Cindy Wooldridge

One of the frequent gimmicks supplied to educators is that a product enhances “brain learning” or something of that sort. Well, folks, we’re here to tell you that all learning takes place in the brain. (And so these are marketing ploys.) In today’s blog, I will share some background information about how learning happens in the brain and then I will review an article fresh off the presses that examines the neuroscience behind how sleep may enhance learning.

“Brain Learning”

In order to understand “brain learning,” one must first understand the brain… or at least some basics. The brain is made up of billions of specialized cells called neurons, which communicate with one another through a giant network. Any two neurons do not actually touch; they have a space between them called a “synapse” where chemicals pass from one neuron to another. The connections between neurons vary in strength based on many different factors, including the number synapses and amount of chemicals that pass between the two, etc.

Now again, these neurons make up a giant web of connections that are responsible for everything we think, feel, and remember. When we acquire new knowledge (of any kind), neurons become more strongly connected, which creates a stronger network and allows the neurons to communicate with each other faster and more efficiently.

While the neuroscience of learning and memory is, of course, much more complicated, those are the basics. For more information, check out neuroscience for kids or brainfacts.org.

Sleep and “Brain Learning”

In a recent article in Science, de Vivo et al. (1) looked more closely at the relationship between sleep and learning. We have talked about the importance of sleep previously. As a reminder, recall is enhanced after sleep (compared to not sleeping), but there are even larger benefits when it comes to understanding information or solving problems. While we have previously talked about the amount of information retained, the current research explored the mechanism of learning that takes place at the synaptic level.

According to one hypothesis, memories are likely strengthened during sleep because our neurons are able to fire without interference from what is going on around us. One way that this might happen is for lots of connections (synapses) to become bigger during the day while we are learning and for those neurons to then be pared down at night, with only the important connections spared.

In their experiment, the researchers measured the size of synapses in three groups of mice. One group of mice slept, one group was kept awake, and the final group stayed awake on their own. The researchers then compared the size of the synapses between the sleep and wake groups. What they found was that synapse size was reduced after sleep, but there was no difference between the two wake groups. Importantly, not all synapses shrank during sleep; only certain synapses were affected, indicating that the neurons that were spared maintained the changes that had happened during learning. The synapses that did shrink were in weaker, less stable synapses (which they could identify using other criteria).

The researchers found these changes in multiple different brain regions and similar changes have been found in flies, so it’s very possible that these same mechanisms exist in the human brain and allow for both learning of new information, but also the integration of that new information with prior knowledge.

The reduction in synapses at night may serve a very important purpose. Throughout the day we acquire tons of new information and the vast majority of it isn’t very useful. I don’t need to recall the color of my students’ clothing, the design of the house on a television show, etc. Because only certain synapses become smaller at night, it is possible that those unimportant memories are targeted so that when we are trying to recall important information, we don’t have a flood of memories. That is, the selective downscaling of synapses might help to reduce memory interference.

Take Away

Any time we learn, our brains change. We know from behavioral studies that sleep enhances the learning that takes place during waking hours. It is possible that the mechanism by which sleep enhances memory is by reducing the unimportant information we acquire during the day so that they do not interfere with our recall.

References:

De Vivo, L., Bellesi, M., Marshall, W., Bushong, E.A., Ellisman, M.H., Tunoni, G., & Cirelli, C. (2017). Ultrastructural evidence for synaptic scaling across the wake/sleep cycle. Science, 355, 507-510.