Sleep Loss Influences the Brain's Creation of Memories

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U.S. Marines catch some sleep at sunrise during multi-day training as part of the Rim of the Pacific 2016 exercise held at Camp Pendleton, California, July 13. Reuters

This article was originally published on Medical Daily.

It is a known fact that the lack of sleep impacts cognitive processes such as attention, reasoning and problem solving. Now researchers at the universities of Groningen (Netherlands) and Pennsylvania have found how sleep deprivation harms memory.

The study, which will be published in peer-reviewed eLife journal, conducted experiments on mice to understand how memory is affected due to changes in the connectivity between synapses — the tiny gaps where a signal passes from one nerve cell (neurons) to the other. Their results showed that five hours of lack of sleep results in loss of connectivity between neurons in the hippocampus, the area of the brain linked with learning and memory.

"It's clear that sleep plays an important role in memory—we know that taking naps helps us retain important memories. But how sleep deprivation impairs hippocampal function and memory is less obvious," Robbert Havekes, first author of the study, said in a statement.

For their study, researchers examined the impact of lack of sleep in mice on the structure of dendrites, the threadlike extensions of nerve cells along which impulses are received from other synaptic cells. They also checked the length of dendrites and number of dendritic spines in the mice's hippocampus after sleep loss of five hours.

The study showed that lack of sleep considerably shortened the length and spine density of the dendrites in the hippocampal region.

Researchers then let the mice sleep continuously for three hours. They found the negative effect that lack of five-hour sleep had on the mice was reversed. The structure of dendrites was similar to those seen in the mice that had enough sleep.

"We were curious about whether the structural changes in the hippocampus might be related to increased activity of the protein cofilin, since this can cause shrinkage and loss of dendritic spines," Havekes said. "Our further studies revealed that the molecular mechanisms underlying the negative effects of sleep loss do in fact target cofilin. Blocking this protein in hippocampal neurons of sleep-deprived mice not only prevented the loss of neuronal connectivity, but also made the memory processes resilient to sleep loss. The sleep-deprived mice learned as well as non-sleep deprived subjects."

The National Heart, Lung and Blood Institute recommends seven to eight hours of sleep for adults, including the elderly. Lack of sleep takes a toll on health with increased risk of heart ailments and diabetes.

Sleep Loss Influences the Brain's Creation of Memories | Tech & Science