It happens due to a mechanism of the brain that controls remembering and forgetting and its work during sleep. This is supported by Luigi De Genaro, professor at theUniversity ofRome, and his team, who used an electroencephalogram to monitor the brain activity of students as they slept.
The experiment involved 65 students: 30 who usually wake up during REM sleep (a sleep phase when the eyes are in rapid motion), and 35 who usually wake up during the second stage of sleep. Approximately two thirds of both groups remembered most of their dreams.
Those who woke up during REM sleep and remembered their dreams were more likely to have an oscillation in the brain of EEG type called Theta. The oscillation appears in the regions of the prefrontal cortex and occurs when we try to think. This type of oscillation is exactly the same as the one that help us recall our memory when we are awake.
Those who did not wake up during REM sleep but during the second stage of sleep and could remember their dreams had oscillations of Alpha type in the prefrontal lobe – these oscillations occur when we see or feel something that stimulates us emotionally when we are awake.
So in conclusion De Genaro emphasizes that when we sleep, the brain activates the same parts that we use in awake state. It was detected that when the parts of the brain responsible for emotions were activated, then the students managed to remember their dreams in more detail.