Researchers for the first time tracked eye movement during sleep.
The study was conducted with experimental mice, Current Biology magazine reported in Discovery.
Daniel Huber's team found that pupils expanded and shrunk rhythmically during sleep. The changes almost ideally coincide with the degree of activity of the brain. And this testifies to the fact that the size of the pupils reflects the current phase of sleep. The deeper the pupils, the deeper the dream is.
There are two types of sleep known - slow and fast.
They are constantly alternating. When a person falls asleep, the phase of slow sleep occurs. Then the body gradually turns off and restores its powers.
During rapid sleep, the body enters the operating mode, but remains stationary. The eyes move chaotic, and then the brightest dreams appear.
During the slow sleep the pupils shrink. This is related to the consolidation of memories and their transfer to long-term memory. The puppies play an important role during sleep because they block external signals.