Sleep deprivation stops brain cells communicating properly and affects how people see the world around them, a new study has shown.

The new research, which has serious implications for driving while tired, shows that parts of the brain actually turn themselves off to rest even though a person is still awake.

Brain scans of sleep deprived people by scientists at the University of California Los Angeles (UCLA) have shown for the first time that fatigue disrupts the speed the brain cells communicate and prevents memories being encoded properly. It also causes temporary lapses in memory and vision.

Dr Itzhak Fried, professor of neurosurgery at UCLA, said the effect could prevent a tired person noticing a pedestrian stepping in front of a car.

“Starving the body of sleep also robs neurons of the ability to function properly,” he said.

“This paves the way for cognitive lapses in how we perceive and react to the world around us. The very act of seeing the pedestrian slows down in the driver's over-tired brain. It takes longer for his brain to register what he's perceiving.

“Inadequate sleep exerts a similar influence on our brain as drinking too much. Yet no legal or medical standards exist for identifying over-tired drivers on the road the same way we target drunk drivers."