New York, July 4 (IANS): Young human brains go through critical periods when vision, speech, language, motor skills, social skills and other higher cognitive functions are being developed.

During these periods, rapid eye movement (REM) sleep actively converts waking experiences into lasting memories and abilities in young brains, says a study.

REM is a unique phase of sleep characterised by the random movement of the eyes, low muscle tone throughout the body and the propensity of the sleeper to dream vividly.

"It helps growing brains adjust the strength or number of their neuronal connections to match the input they receive from their environment," said researchers from Washington State University-Spokane.

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

Providing new insights, Frank and 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".

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

REM sleep may be important for the development of other parts of the brain beyond the visual cortex and its effects may continue throughout a lifetime.

The findings also broaden the understanding of children's sleep needs and calls into question the increasing use of REM-disrupting medications such as stimulants and anti-depressants.

The paper appeared in the journal Science Advances.