The busy babies’ brain
Babies look so peaceful and beautiful when they sleep. Watching your little one snoozing in complete contentment cannot fail to bring a smile to your face, especially when you know that this is also your chance to grab some shut-eye yourself! In the past few months, you have probably come to appreciate sleep and wait for baby sleep more than ever before. Experiencing sleep deprivation makes you really understand just how important sleep is. But for your baby, it is even more vital. You may think that your baby simply falls asleep when she is tired to give her body a rest and her brain takes advantage of baby sleep to switch off from the external world. Far from it! In fact, when your baby is sound asleep, her brain is busy learning. Child development also occurs during sleep. Scientists have been able to study babies’ brain activity during baby sleep, and they have discovered that specific parts of the babies’ brain are actually most active during sleep. This state of lowered consciousness and reduced physical activity enables the brain to carry out vital jobs that cannot be as efficiently accomplished during wakefulness.
While she sleeps, your baby's eyes and ears rest. They're not busy taking in everything that's going on around her, the way they do when she is awake. This gives her brain a chance to turn its attention to the important job of consolidating memory and learning. During her waking hours, your baby has endless experiences, many of them new, and her brain stores multiple different impressions of what she hears, feels, does, or sees, that will need to be further organized during sleep. It's a bit like getting around to filing your paperwork at the end of a particularly busy day at the office. In the case of the human brain, especially the young infant's, the job involves creating new connections between brain cells or neurons. It is a little as if the brain were a huge electrical circuit, and every time learning takes place, a new wire is laid down linking one part of the circuit to another. And, surprisingly, quite a lot of this "wiring up" takes place during sleep. So, next time you see your little one's eyes start to close, remember that her brain is getting ready for the night shift!
How do we know?
Curiously, it is research on the brains of baby birds that provided scientists with vital clues to the role of sleep in brain development. The chicks being studied were in the early process of learning the natural song of their species. They naturally do so by copying their mother bird's vocalisations. In the experiment itself, the baby birds heard and copied a taped recording of their mother's song. The researchers designed two different learning conditions for the chicks. One group of chicks practised their tweeting and then were isolated from all noise for a period of rest during which they stayed awake. In the second case, the group of baby birds also had a silent break following their singing practice, but this time the interval was used to induce sleep.
What the scientists discovered was astonishing. The baby birds that had slept between practice sessions were able to produce a much more accurate song at the next session than those who had stayed awake during their resting time. The researchers had also measured the birds' brain activity throughout the experiment. All the brains were very active when actually mimicking their mothers' song. When it came to the break when the recording was switched off, however, the two groups differed. The baby birds that remained awake immediately reduced their brain activity when it was time to rest. The sleeping birds, by contrast, showed sustained levels of high activity in the brain while they slept, just as if they were singing silently in their sleep or still listening to and processing their mothers' song. In other words, the findings suggest that, while they slept, this second group of chicks was consolidating what they had just learnt about their mothers' song and committing the details to memory. The chicks who stayed awaked between practice sessions did not get a chance to do this, so learnt the song more slowly. So, next time you are lucky enough to hear a nightingale, remember that it was sleep that helped its song become so beautiful.
Learning through sleep
Having discovered that sleep and learning were interlinked in birds, scientists turned their interest to human sleep to better appreciate this relationship. They also wanted to understand how different sleep states might play a role in structuring brain connections. Humans progress through phases of deep and active sleep during the night. Deep sleep is characterised by little body movements and is harder to wake up from. Active sleep is the time when we usually experience dreams and move about, twitching and turning in our beds. Having examined in detail the brain activity that occurs during different phases of sleep, scientists now know that the brain behaves very differently in active versus deep sleep. And, because the former is characterized by busy bursts of activity across most of the brain, one might conclude this is the period when the brain is doing all its work. But in fact, active sleep is not the only time when the brain is busy. On closer inspection, it turns out that a few crucial parts of the brain are actually busiest during so-called quiet, deep sleep, when overall the general activity in the brain is more subdued.
New research is now seeking to understand exactly how the different stages of sleep, including the transitions between them, might be involved in helping the brain to create new pathways for learning. What is actually happening behind your baby's closed eyes? How do the different parts of her brain co-ordinate their work to create more complex pathways? What are the implications of sleep deprivation for child development? Whatever the answers turn out to be, one thing is sure: sleep is absolutely crucial for healthy child development. Without sleep, the brain would struggle to find other opportunities to efficiently re-organize all the information taken in during the day and consolidate it in long-term memory. For your baby, consolidating information in memory is just as important as the actual process of learning. She has spent all day touching objects, listening to sounds, and looking around her environment. When she discovers an interesting new object, feels its unfamiliar texture and shape, shakes it and brings it to her mouth, each one of her senses will send to her brain a different piece of information about this fun play thing. But, while she is awake, there's often little time for bringing it all together into a single mental representation that will allow her to make full sense of this and other novel things. No wonder she needs so much sleep when her days are still filled with constant new experiences. So, next time you tiptoe into your baby's room to give her a little kiss as she sleeps, think about all the important work going on behind those tiny, closed eyelids. Her brain is busier than ever creating all the new connections she needs to make sense of the day's exciting discoveries.