Impact of sleep loss on hippocampus

Download as PowerPoint Slide Figure 1. A schematic overview of hippocampal signaling pathways following sleep deprivation.

Impact of sleep loss on hippocampus

Researchers report sleep deprivation may lead to a loss of connectivity between hippocampal neurons. Researchers from the Universities of Groningen Netherlands and Pennsylvania have discovered a piece in the puzzle of how sleep deprivation negatively affects memory.

For the first time, a study in mice, to be published in the journal eLife, shows 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. 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, the 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 visualize 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. 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.

The researchers then investigated what was happening during sleep deprivation at the molecular level. 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. 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. Emily Packer — eLife Image Source: Published online August 23 29 doi:V.

López-Virgen, et al.: Effects of sleep deprivation in hippocampal neurogenesis 91 for diagnostic purposes) and were able to detect the presence of positive cells to BrdU and other neural markers (glial fibrillary acidic protein [GFAP], NeuN. Scientists don't know exactly how sleep enhances memory, but it appears to involve the brain's hippocampus and neocortex -- the part of the brain where long-term memories are stored.

Sleep loss often aggravates the symptoms of depression, and depression can make it more difficult to fall asleep. On the positive side, treating sleep problems can help depression and its symptoms. This indicates that sleep loss has a detrimental effect on memory in mice.

Impact of sleep loss on hippocampus

It is widely accepted that S-Dep causes memory im- pairment through its deleterious effects on the hippocampus. 4. Sleep deprivation and hippocampal synaptic plasticity.

As described above, behavioural studies looking at the effect of sleep deprivation on memory indicated that the hippocampus is . Chronic sleep loss is a widespread problem in our society (Strine and Chapman ).According to the Center for Disease Control, ∼7%–19% of adults in the US report inadequate sleep, and an estimated 50–70 million Americans suffer from chronic sleep .

The impact of sleep loss on hippocampal function