Why do we dream what we dream

Questioner: Hermann F. from Esslingen

Published: 01/01/2012

Some hunt criminals or fight shaggy monsters, others eat chocolate cakes as high as a house or meet their secret crush. Everything is possible in a dream. But why does the brain produce so many colorful films every night?

The answer from the editors is:

Michael Schredl, sleep researcher at the Central Institute for Mental Health in Mannheim: There are no people who do not dream. Even if we don't remember, we still dreamed. Dreaming is defined as our subjective experience during sleep. This subjective experience never turns itself off - just like in the waking state. If you repeatedly wake people up while falling asleep or while they are asleep, they almost always report bits of dream.

However, it is difficult to answer whether dreaming has a function of its own. Because so that I know what someone has dreamed, they have to tell me the dream. It can be that he is thinking about the dream and therefore has a better idea in the waking state or is able to cope better with a situation. Then I don't know whether the effect comes from the dream itself or from telling and thinking about the dream.

Nevertheless, there are several theories about the meaning of dreaming: During sleep, our brain solidifies and processes what we have learned during the day. Some scientists suspect that dreaming plays an important role in this. Their idea is that when dreaming, the brain mixes new information with old information and then stores it. Because test participants report that in their dreams new experiences mix with old ones, both of which are often emotionally connected. The sleeper works on topics that concern him and, through the creativity of dreams, may find solutions to his current problems.

A similar theory is that in dreams we prepare for situations and train practical skills that we will need later. Because even small children experience a lot of REM sleep, the sleep with the most intense dreams. This sleep stage occurs in four to five phases during the night and makes up about twenty percent of total sleep in an adult. REM stands for Rapid Eye Movement, as the eyes move quickly back and forth under the closed eyelids. This is when the brain is most active, compared to NON-REM sleep or deep sleep. Today it is assumed that we also dream in the other phases of sleep, but the pictorial intense experience is most pronounced in REM sleep.

Other scientists assume that we learn to deal with fearful situations in dreams. Nightmares are only the top of the iceberg. Whenever one experiences a dicey situation during the day, one solidifies the knowledge in the dream in order to avoid this dangerous situation next time. Because those who avoid dangers have a higher chance of survival.

The whole brain works to create dream images, and there is a lot of resemblance to the waking state. When you want to move, the motor cortex is also active. Only the transmission to the muscle is blocked in the brain stem, otherwise the dreaming would move in his sleep. Two differences in brain activity are particularly noticeable in REM sleep: The amygdala, which is responsible for processing emotions, is more active during dreaming than when awake. On the other hand, the prefrontal cortex fires less strongly than in the waking state, which is primarily responsible for planning and straightforward thinking and acting. Some researchers suggest that because of this lower prefrontal cortex activity, dreams are often bizarre.

recorded by Hanna Drimalla