Is there a theory about dreams

4. What is the point of dreams?

"Dreams are the products of a devil from the machine, cries for help from a trapped subconscious." An established scientist, the Munich chronobiologist Till Roenneberg, recently resorted to these drastic images. In his essay “The Dawning” he came to the conclusion that dreams are still “something mystical”, “like so much that we do not understand”.

Several theories are circulating about the meaning of dreaming, some of which seem compatible, but some of which are mutually exclusive. One of the classics is Sigmund Freud's Interpretation of Dreams, which he himself summed up as follows: "Dreams are veiled fulfillments of repressed wishes." Modern psychoanalysts still believe this: They consider dreams necessary to be mentally healthy.

“Dreams are foams.” This is the belief that Harvard physiologist J. Allan Hobson advocates. His activation synthesis theory, which he developed with Robert McCarley in the 1970s, assumes that dreams are merely the meaningless accompaniment of a general activation of the brain that emanates from the "pons" (Latin: bridge), a center in the brain stem. Because it has since been discovered that we do not only dream in the particularly active REM phase (of "Rapid Eye Movements") of sleep, Hobson had to modify his theory. However, he still does not attach any importance to the content of the dreams.

“Dreams help you forget.” This hypothesis was put forward in the early eighties by the DNA discoverer Francis Crick, who turned to neurobiology in his old age. Like cleaning the house, the sleeping brain would pick up scraps of memory to throw away.

The idea has been given new topicality through studies by two Italian psychiatrists, Chiara Cirelli and Giulio Tononi, who teach at the University of Madison / Wisconsin. They consider the whole of sleep to be a big clean-up, in which - under the influence of slow brain waves, so-called delta waves - synaptic connections are weakened so that only the strongest synapses survive the night. Dreams could be the mental accompaniment of the big cleanup.

“Dreams solidify memories,” postulate learning researchers who have found that after a night's sleep or a short nap, it is easier to remember newly learned facts or skills.

A fascinating animal experiment by neurobiologist Matthew Wilson from MIT in Cambridge (USA) points in the same direction: Wilson ran rats through a maze and recorded the nerve cell activity in their hippocampus - a part of the brain that is important for remembering. The researcher soon knew the excitation patterns so well that he could tell just by looking at the data where a rat was in the maze. When Wilson later tried his apparatus on the sleeping rats, he found the same patterns again, sometimes slightly varied, as if the rats simply continued to practice while they were asleep. It is not possible to know with certainty whether they had a dream experience. But there is plenty of evidence to suggest that animals dream - at least mammals and most birds.

But why do we not only recycle realistic memories in our sleep, but also produce bizarre stories in which - as Roenneberg enumerates - "ghosts, monsters, mythical creatures, dangerous animals and hated primary school teachers" play an uncanny role? In other words, what are nightmares for? The Finnish psychologist Prof. Antti Revonsuo has put forward an interesting hypothesis: "The biological function of dreams is to simulate threatening events and thereby practice the perception of dangers and their avoidance." He believes that it was in the early days of mankind there were enough threats to make such a nocturnal “simulator training” evolutionarily plausible.

But who is right? The neuroscientists will surely have to sleep over it several times. Judith Rauch ■

February 5, 2007