Some REM sleep can help you hold on to memories

New Delhi: When it comes to mental health and cognitive function, the importance of rapid eye-movement sleep that deep, restorative stage of sleep that we cycle in and out of throughout the night is so well established that experiments depriving humans of it would be considered unethical.

But there are still mysteries surrounding the function of REM sleep to be explored, including whether, why and how it plays a key role in memory. In a new study, researchers report they have found a novel way to conduct such research — by using tiny lights embedded in a mouse’s brain to disrupt a single aspect of sleep.

Their research has turned up evidence that, after we experience a day’s worth of interaction with our complex world, uninterrupted REM sleep is key to turning those lessons learned into emotional memories and contextual memories.

If you want to hold on to your memories, then hit the sack for some deep sleep as a new study suggests so.

Researchers at the Douglas Mental Health University Institute (McGill University) and the University of Bern provided evidence that rapid eye movement (REM) sleep, the phase where dreams appear, is directly involved in memory formation, at least in mice.

Researcher Sylvain Williams said, “We already knew that newly acquired information is stored into different types of memories, spatial or emotional, before being consolidated or integrated,” adding “How the brain performs this process has remained unclear, until now. We were able to prove for the first time that REM sleep is indeed critical for normal spatial memory formation in mice.”

To test the long-term spatial memory of mice, the scientists trained the rodents to spot a new object placed in a controlled environment where two objects of similar shape and volume stand. Spontaneously, mice spend more time exploring a novel object than a familiar one, showing their use of learning and recall.

When these mice were in REM sleep, however, the researchers used light pulses to turn off their memory-associated neurons to determine if it affects their memory consolidation. The next day, the same rodents did not succeed the spatial memory task learned on the previous day. Compared to the control group, their memory seemed erased, or at least impaired.

“Silencing the same neurons for similar durations outside REM episodes had no effect on memory. This indicates that neuronal activity specifically during REM sleep is required for normal memory consolidation,” said lead author Richard Boyce.

In particular, REM sleep is often significantly perturbed in Alzheimer’s diseases (AD), and results from this study suggest that disruption of REM sleep may contribute directly to memory impairments observed in AD, the researchers noted.