It's well known that REM (rapid eye movement) sleep is important for well-being.
Now, a new study shows that our ability to retain memories and skills may depend on REM.
These findings may help explain how the amount of sleep a child gets can impact how well they do in school.
The results also call into question the increasing use of medications that can suppress REM sleep, such as stimulants and antidepressants, and the effect these drugs may have on children's development.
The findings from the study, which was funded by the National Institutes of Health, were published today in Science Advances.
Enzyme Activated During REM Sleep ‘Locks in’ Experiences
Marcos Frank, Ph.D., professor of medical sciences at Washington State University, and his colleagues knew that animal babies spend much of their early life in REM sleep, but they wanted to understand more about REM's ability to change or recombine memories.
To do so, they documented the effects of sleep on vision development in young animals.
The researchers discovered that brain circuits changed in the visual cortex (responsible for processing visual information) as animals explored their environment, but that REM sleep is required to keep these changes in their memories.
The reason for this, they explained, is that changes are locked in by ERK, an enzyme that is activated only during REM sleep.
Researchers say that ERK allows traces of experiences to be more permanent and focused in the brain. Without REM sleep, the ERK isn't activated and the brain "forgets what it saw," Frank explained.
The study used a model based on findings from the 1960s that showed the visual cortex has critical periods for its development. If vision is blocked during these times, problems can occur.
Researchers placed a patch on one eye of animals and monitored their brain activity while they were awake and asleep.
While in REM sleep, some of the animals were awakened intermittently by gentle tapping. Animals in the control group were awakened during non-REM sleep times.
Normal vision did not develop in animals that did not get enough REM sleep and the ERK enzyme did not get activated in these animals.
Previously, the researchers had determined that ERK works by turning neuronal genes into proteins, which solidify the brain changes.
What the Results Mean for Children
Frank said children's brains go through critical periods when vision, speech, language, motor skills, social skills, and other higher cognitive functions are developed, such as during infancy and adolescents.
The study suggests that during these periods, REM sleep helps growing brains adjust the strength or number of their neuronal connections to match the input they receive from their environment.
These results can help explain why sleep is critical during these times, Frank said.
The findings also point to concerns regarding medications like methylphenidate (Ritalin), which affect brain activity early in life, since they can potentially suppress REM sleep.
"The fact is, we have very little preclinical research data to tell us what these drugs are doing to developing brains in both the short and long term," said Frank.
An unexpected result of the study was that experiences animals had while awake reappeared during REM sleep.
Frank said the discovery may mean that REM sleep is important for the development of other parts of the brain in addition to the visual cortex with its effects continuing throughout a person's life.