Why our eyes move as we dream
Study finds they flicker because we see images just as when we are awake
Our eyes move while we are asleep because we see images just as when we are awake, according to a study.
They flicker as they respond to what our unconscious mind 'sees'. Each flicker during Rapid Eye Movement (REM) sleep - the period when we experience vivid dreams - then signifies a 'change of scene'.
For the study, 19 epilepsy patients had electrodes fitted to monitor their brain activity for two weeks.
The monitoring went on 24 hours a day so the researchers were able to compare what it was like when they were awake with when they were asleep.
Research focused on the medial temporal lobe, an area of the brain that deals with concepts, but not directly with vision.
The results showed that, when patients were shown an image, the neurons in the medial temporal lobe burst into action.
Dr Yuval Nir, of Tel Aviv University in Israel, said that the neurons behaved in a 'similar way' when participants were in REM sleep.
He said: 'It becomes very probable that the eye movements represent some type of reset, or "moving on to the next dream frame".
' It's almost like when I was growing up and we had slide projectors. You move to the next dream slide, if you like.'
Dr Nir, who conducted his research with the University of California, Los Angeles, said the findings may explain why blind people's eyes also flutter during sleep.
He said: 'Even people who are congenitally blind … can still dream about their aunt coming to visit: her voice, the emotions and all the associations that go with that.'
Professor Jim Horne, who established the Sleep Research Centre at Loughborough University, said the new findings backed up other research on REM sleep.
He told BBC News: 'I see REM sleep as rather like the screensaver on your computer; all you need is the touch of a button and your computer leaps to life. It's very close to wakefulness.
'Non-REM sleep is more like when you switch your computer off, and waking up requires a process of rebooting.'