Sleep Strengthens Healthy Brain Connectivity

My 6-year-old daughter has had a regular bedtime and slept in a quiet, safe, and unpolluted environment since the day she was born. Unfortunately, this is not the case for all young children. She is very lucky. Researchers continue to discover the importance of a good night’s sleep on the mind and brain for people of all ages—especially for children.

Researchers at the University of Colorado Boulder have discovered that when young children are sleeping, their brain is very busy building and strengthening connections between the left and right hemispheres of their cerebrum. These connections are made via the splenium which is part of the corpus callosum, a thick band of fibers in the brain that connects the left and right hemispheres and facilitates communication between the two sides.

A study from October 2013 linked Albert Einstein’s genius to well-connected brain hemispheres. As the brain matures, the scaffolding built in childhood serves as an infrastructure to lay down more and more complex neural connections throughout a lifespan.

Having these initial connections made during sleep—and through daily activity during childhood—is imperative to having high-speed communication between brain hemispheres as an adult. Having both sides of your brain symmetrical and well-connected is key to maximizing learning, memory, and creativity.

In a new study, published on November 20, 2013 in the journal Brain Sciences, researchers looked at differences in brain activity during sleep as the children got older and differences in brain activity of each child during a night's sleep.

They found that connections in the brain generally became stronger during sleep as the children aged. They also found that the strength of the connections between the left and right hemispheres increased by as much as 20% over a night's sleep

The research team—led by Salome Kurth, a postdoctoral researcher, and Monique LeBourgeois, assistant professor in integrative physiology—used electroencephalograms (EEG) to measure the brain activity of eight sleeping children multiple times at the ages of 2, 3 and 5 years.

"Interestingly, during a night of sleep, connections weakened within hemispheres but strengthened between hemispheres," Kurth said. Part of neuroplasticity and healthy brain development for children is that some neural connections should become stronger and others should atrophy.

I have written in other Psychology Today blogs about the importance of neural pruning or “Neural Darwinism.” If you’d like to read more on this please check out my post from yesterday titled “The Size and Connectivity of the Amygdala Predicts Anxiety.”

Scientists have known for eons that the brain changes dramatically during early childhood. New connections are formed through neuroplasticity and others are removed through neural darwinism. Also, a fatty layer called "myelin" forms around nerve fibers in the brain. The growth of myelin around each neuron strengthens the connections and speeds up the transfer of information throughout the entire brain.

The maturation of nerve fibers leads to improvement in skills such as language, attention and impulse control as children grow older. Scientists are still not 100% certain exactly what role sleep plays in the development of such brain connections, but they know that it’s important.

The need for sleep is common sense. Everybody knows that babies and young children require an abundance of sleep. That said, having science to remind us of the importance of sleep is helpful for keeping a good night’s sleep high on the priority list througout our lives.

Salome Kurth concludes that, "There are strong indications that sleep and brain maturation are closely related, but at this time, it is not known how sleep leads to changes in brain structure.” Future studies from the University of Colorado team will be aimed at determining how sleep disruption during childhood may affect brain development and behavior.

Learning Disabilities Linked to Poorly Connected Brain Hemispheres

As is often the case with scientific research, the very same day that the researchers at University of Colorado published their study on the benefits of sleep on strengthening brain connectivity, another team of researchers at Michigan State University also published a study about the importance of well-connected brain hemispheres to prevent learning disabilities.

On November 20, 2013 researchers at MSU announced that they have discovered the first anatomical evidence that the brains of children with a nonverbal learning disability (NLVD)—long considered a “pseudo” diagnosis—may develop differently than the brains of other children. The findingsof their study titled “Smaller Splenium in Children with Nonverbal Learning Disability Compared to Controls, High-Functioning Autism and ADHD” was published in Child Neuropsychology.

The MSU researchers hope that these findings will help educators and clinicians better able to distinguish between children with a nonverbal learning disability and those with Asperger’s, or high functioning autism, which is often confused with NLVD. Understanding the biological structural differences in the corpus callosum of children with learning and behavioral challenges could help lead to more effective intervention strategies and treatments.

“Children with nonverbal learning disabilities and Asperger’s can look very similar, but they can have very different reasons for why they behave the way they do,” said Jodene Fine, assistant professor of school psychology in MSU’s College of Education.

Interestingly, children with nonverbal learning disability tend to have normal language skills but their math skills are below average and they have difficulty solving visual puzzles. Many of these children also have difficulty understanding social cues. There is an ongoing debate whether NVLD is related to high functioning autism—this new study suggests that NVLD and and HFA have different brain connections.

Fine and Kayla Musielak, an MSU doctoral student in school psychology, studied about 150 children ages 8 to 18. Using MRI scans of the participants’ brains, the researchers found that the children diagnosed with NVLD had smaller spleniums than children with other learning disorders such as Asperger’s and ADHD, and children who had no learning disorders.

In a second part of the study, the participants’ brain activity was analyzed after they were shown videos in an MRI that portrayed both positive and negative examples of social interaction. (A typical example of a positive event was a child opening a desired birthday present with friend; a negative event included a child being teased by other children.)

The researchers found that the brains of children with nonverbal learning disability responded differently to the social interactions than the brains of children with high functioning autism, or HFA. This suggests that the neural pathways that underlie those behaviors may be different. Interestingly, the posterior part of the corpus callosum serves the areas of the brain related to visual and spatial functioning.

Fine concludes, “So what we have is evidence of a structural difference in the brains of children with NLVD and HFA, as well as evidence of a functional difference in the way their brains behave when they are presented with stimuli. While more research is needed to better understand how nonverbal learning disability fits into the family of learning disorders.”

Jodene Fine believes these findings present, “an interesting piece of the puzzle” and concludes, “I would say at this point we still don’t have enough evidence to say NVLD is a distinct diagnosis, but I do think our research supports the idea that it might be.”

Sleep Reinforces Brain Connectivity and Learning Abilities

Children sleep longer and deeper than adults. Because of the novelty of each new day, children must take in and process enormous amounts of information every day. Swiss and German researchers collaborated to examine the ability to form explicit knowledge via an implicitly-learned motor task.

In the study, children between the ages of 8 and 11, and young adults, learned to guess the predetermined series of actions—without being aware of the existence of the series itself. If you’d like to read more on implicit and explicit learning and memory please check out my recent Psychology Today blog titled “Can Mindfulness Backfire?”

The study, from February 2013, confirmed that during sleep, our brains store what we have learned during the day. “Children's brains transform subconsciously learned material into active knowledge while they sleep—even more effectively than adult brains do,” according to Dr. Ines Wilhelm of the University of Tübingen's Institute for Medical Psychology and Behavioral Neurobiology. The paper titled, “The Sleeping Child Outplays the Adult's Capacity to Convert Implicit into Explicit Knowledge" was published in Nature Neuroscience.

Studies of adults have shown that sleeping after learning something new supports the long-term storage of the material learned. Dr. Wilhelm said, "during sleep, memory is turned into a form that makes future learning easier; implicit knowledge becomes explicit and therefore becomes more easily transferred to other areas."

After a night of sleep, or a day awake, the subjects' memories were tested. The researchers found that after a night's sleep, both age groups could remember a larger number of elements from the row of numbers than those who had remained awake in the interim. They also found that the children were much better at this test than the adults.

Wilhelm said, "In children, much more efficient explicit knowledge is generated during sleep from a previously learned implicit task. And the children's extraordinary ability is linked with the large amount of deep sleep they get at night." He concludes that, "The formation of explicit knowledge appears to be a very specific ability of childhood sleep, since children typically benefit as much or less than adults from sleep when it comes to other types of memory tasks."

Conclusion: Sleep is Crucial for Healthy Brain Development

Humans are designed to spend about one-third of our lives sleeping, which adds up to about 8 hours a night. By the time you are 60, ideally you will have slept for 20 years—5 of those years will be spent in REM sleep, dreaming. This ratio of one hour of sleep for every two hours of wakefulness is hardwired into our biology and necessary for both our survival and optimal performance. If you’d like to read more on this please check out Chapter 11 of The Athlete’s Way titled “The Sleep Remedy.”

If you’d like to read more on this topic, check out my Psychology Today blogs:

• “Neuroscientists Discover How the Brain Learns While We Sleep”
• "Musical Training Optimizes Brain Function"
• “Why Do Sleep and Movement Stimulate Creativity?”
• “Decoding the Secrets of Brain Connectivity”
• “Video Gaming Can Increase Brain Size and Connectivity”
• “Einstein’s Genius Linked to Well-Connected Brain Hemispheres"
• "Hand-Eye Coordination Improves Cognitive and Social Skills"
• "Better Motor Skills Linked to Higher Academic Scores"
• "Human Babies Rely on Primitive Reflexes to Learn Language"

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