What's Happening When A Baby Is Twitching?

I've always been a terrible sleeper. And, you know, there's this old adage that we study the things that we're bad at. [Mark Bloomberg, Professor, Psychology dan Brain Science, University of Iowa, USA]

I always wake up in a groggy state. I never use an alarm clock. Alarm clocks are terrible, you know, 'cause it's important to wake up naturally. Despite my knowing that, I still manage to get bad night's sleep after bad night's sleep. Woe is me.

All animals on this planet have a 24-hour cycle that is tightly linked to the sun. That's called a circadian rhythm. 

So for us humans, you're awake during the day, and asleep during the night in the brain, and it is regulated by the master clock located within a part of the brain called the hypothalamus. But that's not true for babies.

When I first started getting involved in sleep research, I started studying baby rats. What happens with babies, baby humans, baby rats, is that they cycle very rapidly between sleep and wake.

If you're looking at a baby like this, it's just complete relaxation... and then all of a sudden... Boom. Awake. And you can tell it's awake because the left arm and the left leg are in the air at the same time. And then, look at that, it just goes from this... vroom. Asleep.

So over the course of 24 hours, they can have hundreds of cycles between sleep and wake. And so that's what makes babies different. So we wanted to know, you know, why would that be?

So we started out with a very simple experiment. We put a dye into the brain of a newborn rat in the master clock region. And we wanted to know at what age does that part of the brain connect up with other parts of the brain that are important for sleep and wake?

When these baby rats were born, we have all of this red dye here where the master clock is... but when we look closer to the brain stem, we see nothing. We see no labeling at all. So, it's as if the wires connecting this part of the brain to this part of the brain just, just don't exist yet.

But, if we come over here to a week later, we now see all of this area now is red. It was black over here, it's now red over here, and that's an indication that this part of the brain is now talking to this part of the brain.

And what we found was it's also happening in humans.If you look at a model brain, I'm going to pull it apart to expose the brain stem, and the sleep/wake cycles are largely regulated in this region down here.

And then, up here in the hypothalamus, this is where the so-called master clock is located, and that's going to be governing your circadian rhythm. And in newborn infants these areas are not talking to each other, either directly or indirectly. What that means is that those connections are what's responsible for giving rise to the circadian rhythm.

Maybe if you're a parent and you're struggling to deal with the fact that you're sleep deprived because your baby is not, you know, getting through the night, you might just think, "Well, I just have to wait for these connections to form."

Because prior to three to four months, there's very little you can do to help babies sleeping throughout the night. It's just gonna have to wait for the for the circadian system to connect them.

When we studied these rats, I started noticing all of this twitching. I was using twitching as a sign that the animals were sleeping. 

But when you see a behavior like this, and it's remarkable behavior... In many animals it looks like a seizure... You start to wonder, what do these twitches represent?

This is my dog, Katie... and you can see the vigorous twitching in both of her limbs, and even some fluttering in the face. Most people look at this and they think that Katie is, you know, chasing rabbits in her sleep.

The historical view going back hundreds of years, if not millennia, is that twitching is just a byproduct of dreams. And so if you dream about running, your legs will kick a little bit. That was the dominant view, some people still believe it.

And there was this contrast between what I was seeing with my own two eyes and what I was reading in the scientific literature. So over time I just kept asking questions about it. And it evolved into a whole research program that I never anticipated.

So for these experiments, we're trying to do very precise measures of twitching, and we want to know, can we see evidence of brain activity that's related specifically to the movements that we're picking up during sleep?

What we found was when a baby is twitching, what's happening, similar to when you watch a submarine movie... when all the people on the submarine are being asked to be very, very quiet because they're about to do a sonar test.

That's similar to when these babies are asleep. There is very little brain activity... and then when a baby is twitching, boom. That is a sonar test. The captain of the submarine will shoot off one ping only out into the water. And that pinging creates an echo that is allowing you to see what's out there.

In the same way that the brain is kind of trying to figure out, "What's out there?" You know, "What do my limbs do? How many muscles do I have? How are they connected to one another?"

And what we think is happening with twitches is that you're mapping your body. You're learning about the muscles of your body, you're learning about how those muscles control joints, you learn about the relationships, the synergies among the different muscles in your limbs.

A single twitch can produce activity in hundreds, probably thousands, of neurons. And that's what we see in the EEG activity of these human infants. It is how the baby learns what kind of body that it has.

That, I think, provides even further evidence that there's something special about twitches in early development. And that's guiding us now in the work that we do.

Source: Netflix.

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