Through history, humanity have tried to understand the meaning of dreams. Philosophers, mystics, and scientists, all cared about this issue, coming to different answers. Many ancient cultures and even modern ones, interpret dreams as inspirations, divine signs, prophetic visions, sexual fantasies, alternative realities, and many other beliefs, fears, and conjectures, given its mysterious nature.

In 1900, Sigmund Freud in his book "The Interpretation of Dreams," defended the idea that dreams reflect a unconscious experience. He theorized that during the sleep thought tend to be primitive or regressive and that the effects of repression are reduced. For him, repressed desires, specially those associated with sex and hostility, were freed in dreams when consciousness is diminished. However, at that time, the physiology of sleep and dreams was unknown, leaving Freud with only his psychoanalytic interpretation of dreams.

Only in the 50's, with the discovery that rapid eye movements (the so called REM sleep, or Rapid Eye Movement sleep) were frequently an indication that the individual was dreaming (3), a new era for research on dreams emerged, and some elements of the psychoanalysis had to be modified. Dreams became then, predominantly analyzed through theories based in neurological findings.

Nowadays we know that dreams are understood as part of the biologically determined sleep cycle. Several theories have been described, based in neurophysiological and behavioral findings, obtained through the register of brain waves, or through studies of lesions and stimulation of structures of the brain (from animals) that are believed to be involved with dreams.

Why does the brain dream?

The many times bizarre and confusing nature of dreams are speculated by some researchers of the sleep and dreams, as being a means by which the brain get rid of unnecessary or wrong information obtained while the individual was awaken - a process of unlearning or reverse learning (5).

This explains why children, whose learning rhythm is intense, present more REM sleep than adults. According to this idea, they would need to forget the several wrong or meaningless associations formed during their learning while awaken favoring in this way, the storing of associations or information that are truly important.

These researchers postulate that the neocortex, a complex network of neural association, could become overloaded with great quantities of received information. The neocortex could then develop false or "parasite" thoughts, which could compromise the true and orderly storage of the memory.

In this same line of thought, other scholars theorize that dreams consist of associations and memories elicited from the frontal part of the brain, in response to random signals from the brain stem. These authors (13), suggest that dreams are a better "adjustment" that the frontal brain could provide to this random bombardment from the brain stem. In this proposition, the neurons of the pons, via thalamus, would activate several areas of the brain's cortex producing well known images or even emotions, and the cortex would then try to synthesize these disparated images. The "synthesized" dream can be completely bizarre and even without meaning because it would have been unleashed by an semi-random activity of the pons (see Neural Mechanisms of Dreams).

William Dement call us the attention to the fact that each of us are "insane", when, we dream, we manifestate the most bizarre situations. Other researchers state that failure in the ability to process REM sleep, may cause fantasy, hallucination and obssession (9). Still other, argue that lack of REM sleep induces alucinatory psycosis and other mental disorders.

Based on these findings and theories, we might think that dreams are defense and adaptation mechanisms, and the "insanity" expressed during this quietly and uncouscious state seems to be necessary for we keep ourselves "sane" during our agitated state of counsciousness.

Is It Possible to know When a Person is Dreaming?

The Meaning of Dreams

Neurobiology of Dreams (Electrical Activity) (Neural Mechanisms)

Why Don't We Act Out While Sleeping?

Do Animals Dream?

Do We Need to Dream?

Resources on Dream and Sleep

References

Author: Silvia Helena Cardoso, PhD. Psychobiologist, master and doctor in Sciences by the University of São Paulo and post doctoral fellowship by the University of California, Los Angeles. Invited Professor and Associate Researcher of the Center for Biomedical Inofrmatics, State University of Campinas (Unicamp), Brazil.