Sunday, November 15, 2015

REMemory



Scientists: Shallow REM sleep helps development of memory  
graphic: The Asahi Shimbun

The Asahi Shimbun  November 13, 2015  By SUSUMU YOSHIDA/ Staff Writer

Shallow sleep involving dreams, known as rapid eye movement (REM) sleep, helps form memory in the brain during the subsequent stage of deep sleep, Japanese scientists said.

A research team from the University of Tsukuba, the Riken national research institute and other institutions said their findings from experiments with mice could help finally reveal the roles of REM sleep. The studies might also help unravel the mysteries of Alzheimer’s disease, depression and other illnesses.

REM sleep is a condition found in birds and mammals. In humans, REM sleep is common in newborn babies, and accounts for about 15 percent of the duration of sleep in adults. But its specific roles have remained unknown.

Yu Hayashi, an assistant professor of neuroscience at the University of Tsukuba, and co-researchers identified nerve cells in the brain that are involved in switching from REM sleep to deep, non-REM sleep. They genetically engineered mice whose switches can be manipulated at will to study the effects of REM sleep.

They discovered that slow delta waves generated in the brain during non-REM sleep gradually weakened in mice that were deprived of REM sleep. In contrast, an increase in REM sleep strengthened the delta waves generated during non-REM sleep.

Delta waves are known to assist the formation of memory and the recovery of brain functions.

“REM sleep is apparently prompting memory to be organized in the brain,” Hayashi said.

Delta waves decrease during sleep among patients with Alzheimer’s disease and depression.

The team’s research results were published Oct. 22 in the U.S. academic journal Science.