Sleep deprivation can harm your memory: study

Five hours of sleep deprivation may harm your memory as it leads to a loss of connectivity between neurons in the hippocampus, a region of the brain associated with learning and memory, a new study has found.
"It is clear that sleep plays an important role in memory - we know that taking naps helps us retain important memories," said Robbert Havekes from University of Groningen in the Netherlands.
"But how sleep deprivation impairs hippocampal function and memory is less obvious," said Havekes.
It has been proposed that changes in the connectivity between synapses - structures that allow neurons to pass signals to each other - can affect memory.

To study this further, researchers examined the impact of brief periods of sleep loss on the structure of dendrites, the branching extensions of nerve cells along which impulses are received from other synaptic cells, in the mouse brain.
They first used the Golgi silver-staining method to visualise the length of dendrites and number of dendritic spines in the mouse hippocampus following five hours of sleep deprivation, a period of sleep loss that is known to impair memory consolidation.

Their analyses indicated that sleep deprivation significantly reduces the length and spine density of the dendrites belonging to the neurons in the CA1 region of the hippocampus.

They repeated the sleep-loss experiment, but left the mice to sleep undisturbed for three hours afterwards. This period was chosen based on the scientists' previous work showing that three hours is sufficient to restore deficits caused by lack of sleep.
The effects of the five-hour sleep deprivation in the mice were reversed so that their dendritic structures were similar to those observed in the mice that had slept.
Researchers then studied what was happening during sleep deprivation at the molecular level.
"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," said Havekes.

"Our further studies revealed that the molecular mechanisms underlying the negative effects of sleep loss do in fact target cofilin," he said.
Researchers found that five hours of sleep deprivation leads to a loss of connectivity between neurons in the hippocampus, a region of the brain associated with learning and memory.
"Lack of sleep is a common problem in our 24/7 modern society and it has severe consequences for health, overall wellbeing, and brain function," said Ted Abel from University of Pennsylvania in the US.
When subjects have a chance to catch up on much-needed sleep, they are rapidly remodelling their brain, he said.

The findings were published in the journal eLife.