Rapid eye movement (REM) sleep actively converts waking experiences into lasting memories and abilities in young brains, reveals a new study from Washington State University.
The finding broadens the understanding of children's sleep needs and calls into question the increasing use of REM-disrupting medications such as stimulants and antidepressants.
Researcher 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, adding that experience is fragile and 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.
The study is published in Science Advances