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Dreams, Sleep and Memory |
We still don't understand exactly why we dream, although there are some prevailing notions. Sigmund Freud published The Interpretation of Dreams in 1900 and presents an idea which most believe still to be relevant. This is the idea that dreams are a function of repressed emotions. Freud tells us that dreams are "the royal road to knowledge of the unconscious activities of the mind." The tendency of modern people to trace their problems to childhood traumas or other repressed emotions begins with Freud. One of Freud's more important discoveries is that emotions buried in the unconscious surface in disguised form during dreaming, and that the remembered fragments of dreams can help uncover buried feelings (Reading About the World, Volume 2, edited by Paul Brians). The idea that we can actually help ourselves cope with the stresses of everyday life is truly alluring. No one would doubt the interest evoked for anything that provided us with insight into ourselves. Freud believed that dream content was a sort of mixture of repressed childhood anxiety, and the previous day's occurrence. This appears sound because our dreams do seem to, at least as far as content is concern, reflect recent experience. According to Brandan Schulze (©1997 ThinkQuest Team 11189), "If our minds have been dealing with too much denial, regression, or repression, it causes an internal conflict, a dream in this case, to take place. This prevents us from building up intolerable states of psychological tension in waking life. This is why, if you become too emotional, it actually works to sleep it off." So dreams in deed do have a purpose, and act as a kind of daily tension release value.
A second theory, advanced by Evans (1984) suggests that dreams are a by-product of the nightly reorganizing efforts of our brains. During REM sleep, the conscious mind goes offline and our brain begins the process of "scanning in" and sorting through the information gathered during the day in order to commit it to memory. During sleep, our conscious mind somehow peeks behind the curtain and catches glimpses of the brain feverishly sorting and filing. These bits and pieces are considered and interpreted by the mind as if we were still awake, and these interpretations become the content of our dreams. Interesting, and not without some sense of being exactly correct. We've all had the experience of sleeping on a problem that, after resting, results in our shouting "EUREKA, why didn't I think of that yesterday". It makes sense that after all the facts are considered, properly sorted and filed, answers to problems materialize. It also feels right that our dreams might be a hodgepodge of yesterday's sensory inputs which we somehow try to string together into some logical story line. Often the story line causes us to scratch our heads the next morning, as we try to reconstruct the dream.
In 1983, Crick & Mitchison (F. Crick & G. Mitchison - The function of dream sleep. Nature 304, 111-114) proposed that one function of REM sleep was as an unlearning mechanism. Their theory of dreams, similar to Evans, sees the brain operating during REM sleep to sort through the multitude of yesterday's sensory inputs. We know the brain is extremely active during REM sleep. Crick and Mitchison believe that what our brain is actually doing is busily cleaning up our neural networks. We take in so much sensory input during the day, it makes sense we would need to discard or erase what Crick and Mitchison refer to as "spurious memory". What better time to clean up our neuronal networks than while we are asleep; when sensory input has all but ceased.
Further evidence and adding strength to Evans' as well as Crick and Mitchison's theories is the fact that we perform better after a good night's rest. This from Bill Klemm, Ph. D. Found in his article entitled Getting from Here to There: Making Memory Consolidation Work, "Experiments have shown that human memory performance unexpectedly deteriorated if learning sessions were increased to four 60-minute sessions at regular intervals on the same day. In other words, the more the subjects were trained, the poorer they performed. However, this interference did not occur if subjects were allowed to nap for 30-60 minutes between the second and third sessions. This is yet another reason why students should not cram-study for exams. Learning should be optimized by rehearsing the same learning material on separate days where normal sleep occurred each night.
Furthermore, a recent study conducted by Prof. Avi Karni and Dr. Maria Korman of the Center for Brain and Behavior Research at the University of Haifa found a ninety minute daytime nap helps speed up the process of long term memory consolidation. The hope of further research is to discover methods to accelerate memory consolidation in adults and to create stable memories in a short time. Until then it's nice to know as I age that napping is a good thing and sweet dreams! |
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