Monitoring the brains of newborn babies while they sleep gives us insight into how they learn.
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Like many other people, I’m pretty sure I don’t get enough sleep. In my case, it’s partly because my four-year-old likes to wake me up for a chat at some point between 4 a.m. and 6 a.m. on a daily basis. I’m jealous of my two-year-old, who gets a 12-hour stretch overnight and a two-hour nap in the afternoon. Oh, the luxury.
Toddlers need more sleep than adults. And my youngest used to spend even more time sleeping. For the first couple of months of her life, it seemed she was barely awake. Scientists are still figuring out exactly why babies need so much sleep, but a new tool is starting to shed a bit more light on this mystery—and could help reveal what is going on inside the rapidly developing brain of a newborn.
“This is a time when … the brain is developing new connections at a rate of something like a million synapses a second,” says Topun Austin, a consultant neonatologist at Cambridge University Hospitals NHS Foundation Trust in the UK. These connections are thought to play a key role in helping babies learn to make sense of the world around them. Many will later be pruned away as babies refine their understanding. But the first weeks of a baby’s life are when crucial foundations are set for life.
Sometimes, researchers will put a cap of EEG electrodes on a baby to study electrical brain activity. But this form of imaging doesn’t give much spatial resolution, making it hard to pinpoint exactly which brain regions are active at any one time.
Optogenetics and advanced imaging have helped neuroscientists understand how memories form and made it possible to manipulate them.
Others have put babies in MRI scanners that measure blood flow in the brain. If you’ve ever had an MRI scan, you can see why these hulking machines might not be the best place for a baby. They are noisy and require near-perfect stillness from the person being scanned.
Austin and Julie Uchitel, a former PhD student at the University of Cambridge and now a medical student at Stanford University, and their colleagues have developed a different approach. The team has used a cap with light sources and sensors embedded in it. Together, these components can measure blood flow in the brain in the same way as a pulse oximeter clipped onto your finger in a doctor’s office.
Similar techniques have been used to study the brain before, but they require the use of a cap with multiple fiber-optic cables coming out of it—not something a newborn is likely to want to sleep in. The new device makes use of recently developed tiles that each contain several light sources and detectors. Austin’s team has fitted 12 of these tiles into a cap suitable for newborns, connected to a computer with a single cable. The resulting system offers an image of the brain “at least 10 times the resolution of the [previous] fiber-optic cable system,” says Austin.
In a recent study published in the journal NeuroImage, the team asked new parents if they could monitor their babies while they were still in the postnatal ward of a hospital. “It’s like a little swimming cap—the babies seem very happy once it’s on,” says Austin. His team recorded activity from the brains of 28 newborns as they slept.
Babies cycle through two phases of sleep: an active phase, which is accompanied by twitching and grimacing, is followed by a quiet phase, when the baby is very still. The team filmed all the babies while their brains were monitored, so that they could later work out which phase of sleep each baby was in at any time.
The challenges of tackling this question are so daunting that few have tried. But Heather Kosakowski, a PhD candidate at MIT, is determined to find answers.
Later, when Austin and his team analyzed snapshots of the recordings, they noticed differences in the brain during active and quiet sleep. During active sleep, when the babies were more fidgety, brain regions in the left and right hemispheres seemed to fire at the same time, in the same way. This hints that new, long connections are forming all the way across the brain, says Austin. During quiet sleep, it looks as though more short connections are forming within brain regions.
It’s not clear why this might be happening, but Austin has a theory. He thinks that active sleep is more important for preparing the brain to build a conscious experience more broadly—to recognize someone else as a person rather than a series of blobs and patches of color and texture, for example. Various brain regions need to work together to achieve this.
The shorter connections being made during quiet sleep are probably fine-tuning how individual brain regions work, says Austin: “In active sleep, you’re building up a picture, and in quiet sleep [you’re] refining things.”
The more we know about how healthy newborn brains work, the better placed we are to help babies who are born prematurely, or who experience brain damage early in their lives. Austin also hopes to learn more about what each phase of sleep might be doing for the brain. Once we have a better understanding of what the brain is doing, we might be able to work out when it is safest to wake the baby for feeding, for example.
Austin envisages some kind of traffic light system that could be placed close to a sleeping baby. A green light might signal that the baby is in an intermediate sleep state and can be awakened. A red light, on the other hand, might indicate that it’s best to let the baby stay asleep because the brain is in the middle of some important process.
I’ve tried to do something similar with my own kids. A cloud-shaped toy in their room turns green and plays a song when it’s safe to wake Mummy. The cloud is ignored. Unfortunately, once their brains are ready for wakefulness, they don’t seem to mind that mine isn’t.
“This kid is squealing like crazy. The mom is nervous. The whole thing is stressful.” Rachel Fritts explores just how tricky it is to study babies’ brains in fMRI scanners in this piece from last year.
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