REM sleep critical for young brain development; medication interferes

Rapid eye movement or REM sleep actively converts waking experiences into lasting memories and abilities in young brains reports a new study from Washington State University Spokane.

The finding, published in Science Advances, broadens the understanding of children's sleep needs and calls into question the increasing use of REM-disrupting medications such as stimulants and antidepressants.

The study was funded by the National Institutes of Health.

Making experience 'stick'

Professor of medical sciences Marcos Frank said scientists have known that infant animals spend much of their early life in REM sleep, but little was understood about the actual nuts and bolts of REM's ability to change or recombine memories.

Providing new insights, Frank and his colleagues documented the effects of sleep on vision development in young animals. The researchers found that brain circuits change in the visual cortex as animals explore the world around them, but that REM sleep is required to make those changes "stick."

The scientists showed that the changes are locked in by ERK, an enzyme that is activated only during REM sleep.

"REM sleep acts like the chemical developer in old-fashioned photography to make traces of experience more permanent and focused in the brain," said Frank.

"Experience is fragile," he said. "These traces tend to vanish without REM sleep and the brain basically forgets what it saw."

Frank said young brains, including those of human children, go through critical periods of plasticity - or remodeling - when vision, speech, language, motor skills, social skills and other higher cognitive functions are developed.

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, he said.

REM and vision development

In the 1960s, Frank said surgeons noticed that delayed removal of congenital cataracts in children resulted in severe problems such as double vision and the inability to align the eyes.

"The visual cortex is very sensitive to information it is receiving and there are critical periods for its development," he said. "If vision is blocked at these stages, then problems result."

The study used a model based on that finding to determine the specific effects of REM sleep on vision development. Animals had a patch placed over one eye and their brain activity was monitored both while awake and during sleep.

While in REM sleep, the animals were awakened intermittently by gentle tapping on their enclosures. Controls were awakened during non-REM sleep.