Allowing young children to stay up late could damage their developing brains, scientists warn.

Irregular bedtimes can disrupt the parts that are still maturing - including those involved with vision, spatial perception and processing sensory input.

After being sleep deprived a child's brain needs even more deep sleep - particularly for these specialised regions.

In a study the brain activity of 13 five to 12 year-olds was measured on two nights - a week apart - while they were sleeping at their home.

On the first occasion they went to bed at their normal hour but the second time they were allowed to stay up later causing them to sleep for half the usual amount.

The scans showed their brains responded differently to sleep deprivation compared to adults.

The reduced amount of sleep led to an increased need for deep sleep in the maturing areas at the back of the brain.

Sleep is vital for humans. If adults remain awake for longer than usual the brain responds with an increased need for deep sleep.

This is measured in the form of 'slow wave activity' using a technique known as EEG (electroencephalography).

In adults, these deep-sleep waves are most pronounced in the prefrontal cortex at the front - the region which plans and controls actions, solves problems and is involved in working memory.

But sleep deprivation in children increases deep sleep in posterior brain regions.

For the first time, the study demonstrated curtailed sleep in children also results in locally increased deep sleep.

Dr Salome Kurth, of University Hospital Zurich, said: "A child's brain reacts differently to acute sleep deprivation than an adult's.

"The deep-sleep effect doesn't appear in the front regions of the brain like in adults, but rather in the back - in the parietal and occipital lobes."

The team also discovered the heightened need for sleep - measured as an increase in deep sleep - in children is associated with the myelin content in nerve fibres in the brain's visual system.

The level of myelin - a fatty sheath around the nerve fibres which speeds up the transfer of electrical signals - is a yardstick for brain maturity and increases in the course of childhood and adolescence.

The new results published in Frontiers in Human Neuroscience now reveal the higher the myelin content in a brain region the more similar the deep-sleep effect is to adults.

Dr Kurth said: "Our results show the deep-sleep effect occurs specifically in a particular region of the brain and is linked to the myelin content."

He said the effect might only be temporary, - only occurring during sensitive developmental phases in childhood or adolescence.

The scientists assume the quality of sleep is jointly responsible for the neuronal connections to develop optimally during childhood and adolescence.

Consequently it's important for a child to sleep sufficiently during this life phase.

According to international guidelines, the recommended amount of sleep for children aged 6 to 13 is 9 to 11 hours per night.

Previous research has shown children going to bed at different times each night fare worse on mental tasks than children who have a set bedtime.

Source: Mirror