Study Shows How Sleep Deprivation Negatively Affects Memory

Lack of adequate sleep can be a serious health issue. Not only does it lead to poor health, but it can seriously affect your cognitive processes such as your ability to learn, solve problem and retain information. Now researchers from the Universities of Groningen (Netherlands) and Pennsylvania have discovered how sleep deprivation negatively affects memory.

According to the paper published in the journal eLife, five hours of sleep deprivation leads to a loss of connectivity between neurons in the hippocampus – the area of the brain responsible for learning and the formation of memories. The result was obtained after being studied on mice to understand how the changes in the connectivity between synapses – structures through which electrical or chemical signals flows from one neuron to another other – affect 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,” said Robbert Havekes, lead author of the study, in a statement.

For the study, the team examined the impact of brief periods of sleep loss on the structure of dendrites, the short branched extensions of nerve cells along which impulses are received from other synaptic cells, in the mouse brain. Using Golgi’s silver staining technique to visualize nervous tissue, they checked the length of dendrites and number of dendritic spines in the mouse hippocampus after five hours of sleep deprivation. Their analyses showed that insufficient sleep significantly shortens the length and spine density of the dendrites belonging to the neurons in the CA1 region of the hippocampus.

Researchers repeated the sleep-loss experiment, but left the mice to sleep continuously for another three hours so that they could restore deficits caused by lack of adequate sleep. They found that the effects of sleep deprivation of five hours in the mice were reversed. And their dendritic structures were similar to those observed in the mice that had enough sleep. The team also investigated 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. 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.”

As recommended by health experts, you need at least seven to nine hours of sleep as an adult; and children even more. If taken lightly, chronic sleep deprivation can even be deadly health issue as it takes a toll on health with problems such as obesity, diabetes, increased risk of heart ailments and even early mortality.

“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,” explained Ted Abel, senior author of the study. “Despite decades of research, the reasons why sleep loss negatively impacts brain function have remained unknown. Our novel description of a pathway through which sleep deprivation impacts memory consolidation highlights the importance of the neuronal cell network’s ability to adapt to sleep loss. What is perhaps most striking is that these neuronal connections are restored with several hours of recovery sleep. Thus, when subjects have a chance to catch up on much-needed sleep, they are rapidly remodeling their brain.” [Image]

• Reference: Sleep deprivation causes memory deficits by negatively impacting neuronal connectivity in hippocampal area CA1 – eLife