Sleep’s true value and the damage done by disturbances to our rest has finally been discovered by scientists who say it is a vital time for rest and recovery.
The discovery also sheds light on how sleep affects brain performance, ageing and various disorders, experts say.
Researchers found sleep allows our nerve cells to perform vital nuclear maintenance.
Three dimensional time-lapse images of activity in zebrafish shows that animals require sleep in order to protect their DNA.
Sleep is the downtime that allows our nerve cells to perform vital ‘maintenance’ tasks, suggests a new study. Imaging of chromosome dynamics (green) in A single neuron (red, dashed box) in a live zebrafish larvae
Sleep has remained essential to all organisms with a nervous system, including invertebrates such as flies and jellyfish, throughout evolution.
Little is known about why it is a necessity despite many studies that show sleep is important for memory consolidation and learning ability,
In the study, researchers at Bar-Ilan University in Israel revealed the body repairs itself during sleep.
Using the 3D time-lapse imaging techniques in live zebrafish, the team were able to define sleep in a single chromosome resolution.
it revealed single neurons require sleep in order to perform nuclear maintenance.
The zebrafish was used because of its transparency and the similar organisation of its brain to humans.
This makes them the ‘perfect’ study animal as researchers can study single cells within a live animal.
DNA damage can be caused by many processes, including radiation and oxidative stress.
This is an imbalance between the production of free radicals – chemicals that can potentially cause harm to cell tissues and have been linked to ageing and even cancer – and the ability of the body to counteract or detoxify their harmful effects
Even the processes that allow our brains to function can be a cause such damage.
The current work shows that during wakefulness, this damage consistently accumulates and can reach unsafe levels.
The role of sleep is to normalise the levels of DNA damage in each single neuron, the study says.
A certain amount of repair is done while awake but, according to the researchers, the maintenance process is not efficient enough.
Therefore, an ‘offline’ sleep period with reduced input to the brain needs to occur.
Scientists say their groundbreaking research may finally explain why people spend around a third of our lives asleep. This image shows simultaneous imaging of chromosome dynamics (red) and neuronal activity (green) in live zebrafish
The surprise discovery may also explain how sleep and sleep disturbances affect brain performance, ageing and various brain disorders, experts say. This stock image shows an adult zebrafish
Study leader Professor Lior Appelbaum, of Bar-Ilan University, said: ‘It’s like potholes in the road.
‘Roads accumulate wear and tear, especially during daytime rush hours, and it is most convenient and efficient to fix them at night, when there is light traffic.’
He calls the accumulation of DNA damage the ‘price of wakefulness’.
He and his colleagues hypothesised that sleep consolidates and synchronises nuclear maintenance within individual neurons, and set out to confirm the theory.
Using a high resolution microscope, the movement of DNA and nuclear proteins within the cell – inside the fish – can be observed while the fish are awake and asleep.
The researchers were particularly surprised to find that chromosomes are more active at night, when the body rests, but the increased activity enables the efficiency of the repair to DNA damage.
Professor Appelbaum said the results establish chromosome dynamics as a potential marker for defining single sleeping cells and propose that the restorative function of sleep is nuclear maintenance.
He said: ‘We’ve found a causal link between sleep, chromosome dynamics, neuronal activity, and DNA damage and repair with direct physiological relevance to the entire organism.
‘Sleep gives an opportunity to reduce DNA damage accumulated in the brain during wakefulness.’
‘Despite the risk of reduced awareness to the environment, animals – ranging from jellyfish to zebrafish to humans – have to sleep to allow their neurons to perform efficient DNA maintenance, and this is possibly the reason why sleep has evolved and is so conserved in the animal kingdom.’
