How Does Sleep Make Babies' Learning And Memory Better?

Some people are night owls, but I'm very much the opposite. I'm a lark. I like to get up early in the morning. It's the time where I'm very clear-headed, I can see through my problems really well. [Rebecca Spencer, Professor, Psychology and Brain Science, University of Massachusetts, USA]

The benefit of a clear good night's sleep with a fresh morning run, it's definitely when I think the best. I feel like I got into studying sleep accidentally.

My research background was in learning. In about the mid-2000s, I was a postdoc at UC Berkeley as a neuroscientist. I remember this study coming out saying that sleep deprivation in young adults is bad for the memory, and that sleep itself was doing something good. That was really novel and somewhat revolutionary.

And because of my background, I was in a good position to be able to look at that. But I want to understand how does sleep make learning and memory better?

When we started this project, studying babies, there wasn't much that had been done in relation to sleep. They really weren't things that would get to the heart of how important sleep was for memory. We know that infants need a couple naps a day, so in our study, we wanted to find out if naps are essential to protecting the memories.

So we devised this experiment starting with nine-month-olds, and we teach them this task, which for an infant means to show them how to play with toys that they hadn't seen before.

They are shown eight toys, and four of those toys we play with in a certain way. Not the regular action an infant would be expected to take. Then we give them back those toys to see if they remember the actions we performed with the toys.

After the first step in the experiment, we record brain activity. That's when the fun begins for me as a neuroscientist to really understand whether sleep has an impact on their memory.

After that, we have two scenarios.

In the first scenario, the babies are kept awake during the time when they would normally be napping. And we then see if they remember the actions we performed with the toys.

It does seem like there may have been a decay in memory here. When that baby skipped naptime, he didn't remember any of the objects.

In the second scenario, we let the babies take their normal nap. We let them sleep, and then, when the infant wakes up, we can see whether they remembered those toys.

So what we're seeing in this study is that the infants are remembering more of those toys, or what we did with the toys, if they took a nap versus when they stayed awake during naptime.

And then we get the exciting part of really digging in and trying to make sense of it. What was sleep doing to the brain that is so important for memory?

And so these waves here is a recording of just the brain activity, um, during sleep. And these bursts you can see stand out from that record. Those are called "sleep spindles." They happen simultaneously across the brain, which provides a good mechanism for the brain to take information from short-term memory area, called the hippocampus, and relocate it in the long-term storage, called cortex.

And that simultaneous burst of activity is thought to support the idea that the memories could be moved out from the short-term hippocampus storage out to the longer-term storage by simultaneously firing all of these different parts of the brain at the same time.

But in an infant, their hippocampus is smaller. So babies need to sleep in multiple sleep bouts, two naps and that overnight sleep, because they have to take that information that's piled up in their short-term storage and move it to its permanent location more frequently than we do.

These are the kinds of results I get excited about. It struck me as a scientist, it struck me as a mom. Naps are important, and we need to value the time that the infants are spending sleeping. Yay!

It's not only something that is that downtime for a mom to take a break, but that it's actually serving a function for these infants. It's when they're laying down those memories that are the foundation for everything that they go on to do.

Source: Netflix.

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