Researchers have discovered the human infant’s brain, a body that is unexpectedly active during the second major sleep phase.

Human babies do more than we expected while we were sleeping.

A new study by researchers at the University of Iowa provides further insight into the coordination that occurs between the brain and body when the baby is asleep.

Researchers at Iowa have long studied the seizures of babies during REM sleep and how those seizures contribute to the ability of the baby to regulate body movements. In this study, scientists report that from about 3 months of age, babies see a marked increase in seizures in the second major stage of sleep, called quiet sleep.

“This is completely amazing and, as far as we know, is unique to humans and human babies,” said Professor and Chair of the Department of Psychological Brain Sciences and one of the authors of the study. Mark Blumberg says. “We saw something unexplained based on years of observation in baby rats and what is available in the scientific literature.”

Researchers recorded 22 sleeping babies and their seizures from 1 week to 7 months of age. Initially, scientists focused only on seizures that occur in parallel with REM sleep, in line with previous studies of seizures associated with REM sleep in other mammals.

But then a surprise arose. Researchers have noticed that babies are cramping their limbs outside of REM sleep.

“The cramps looked exactly the same,” said Greta Sokolov, a research scientist and lead author of the study at the Department of Psychology and Brain Sciences, Iowa. “I didn’t expect to see cramps during quiet sleep. After all, humans and other animals usually don’t move in that state, so quiet sleep became the name.”

Researchers were recording brain waves in sleeping babies, allowing them to study seizure-related brain activity. As expected, they noticed that during quiet sleep, the baby generated a large brain vibration called the sleep spindle about once every 10 seconds.

Sleep spindles provide a window for coordination between the brain and its motor system. Researchers found that the proportion of sleep spindles in infant subjects increased about 3 to 7 months after birth, with the cortex concentrated along the sensorimotor strips that process sensory and motor information. did. These facts about sleep spindles were especially important after researchers discovered that sleep spindles and seizures were in sync.

“Sleep spindles are widely associated with learning and memory,” says Sokolov. “Therefore, our findings are that what infants do is learn about their bodies through cramps during sleep, which we previously thought was defined by behavioral silence. Suggested. “

This discovery paves the way for a whole new study of brain-body communication that takes place while the baby is asleep.

“Our findings may reflect something important about the contribution of the cortex to motor control,” says Bloomberg. “Baby needs to integrate the brain and body in order for the system to set up and function properly. Not everything is connected at birth. There are many developments that must occur after birth. I. What we think we are seeing is a new mode of integration between the brain and different parts of the body. “

Researchers say the study had a small sample size, especially at a young age, and infants were recorded during short daytime sleep. They plan to recruit more babies and study their sleep during the day and night to see the findings.

A study, “Twitch appears postnatally during the quiet sleep of human babies and synchronizes with the sleep spindle,” was published online in the journal on June 16. Current biology..

Contributors from Iowa include James Dooley, Ryan Glanz, Rebecca Wen, Meredith Hickerson, Laura Evans, Haley Laughlin and Keith Apfelbaum.

The research was funded by the National Institute of Health and Human Development, a branch of the National Institute of Health.