March 26, 2005
Q: What are dreams and their purpose? - Layperson
A: To grasp the answer one must first understand sleep. In 1953, Eugene Aserinsky of the University of Chicago noticed that the eyes of sleeping babies moved beneath their eyelids at certain regular intervals. This led to the discovery of REM (Rapid Eye Movement) sleep periods, which occur at roughly 60-90 minute intervals throughout the night and which contain the dreams which are the most vivid and most often remembered. Since then, EEG (electroencephalogram) recordings, which monitor brain activity during sleep, have been used to map the various stages of sleep. These states are classified roughly into sleep onset (hypnagogia or stage 1), non-REM sleep (deep sleep or stages 2, 3, and 4), and REM (or paradoxical) sleep.
There are five distinct sleep stages that can be measured by polysomnography: rapid eye movement (REM) sleep and four stages of non-rapid eye movement (NREM) sleep states 1, 2, 3, and 4.) Stage 1 NREM sleep is a transition from wakefulness to sleep and occupies about 5% of time spent asleep in healthy adults. Stage 2 NREM sleep, which is characterized by specific EEG waveforms (sleep spindles and K complexes), occupies about 50% of time spent asleep. Stages 3 and 4 NREM sleep (slow-wave sleep) are the deepest levels of sleep and occupy about 10%-20% of sleep time. REM sleep, during which the majority of typical story-like dreams occur, occupies about 20%-25% of total sleep.
These sleep stages have a characteristic temporal organization across the night. NREM stages 3 and 4 tend to occur in the first one-third to one-half of the night and increase in duration in response to sleep deprivation. REM sleep occurs cyclically throughout the night, alternating with NREM sleep about every 80-100 minutes. REM sleep periods increase in duration toward the morning. Human sleep also varies characteristically across the life span. After relative stability with large amounts of slow-wave sleep in childhood and early adolescence, sleep continuity and depth deteriorate across the adult age range. This deterioration is reflected by increased wakefulness and stage 1 sleep and decreased stages 3 and 4 sleep.
Polysomnography is the monitoring of multiple electrophysiological parameters during sleep and generally includes measurement of EEG activity, electrooculographic activity, and electromyographic activity. Additional polysomnographic measure may include oral or nasal airflow, respiratory effort, chest and abdominal wall movement, oxyhemoglobin saturation, or exhaled carbon dioxide concentration; these measures are used to monitor respiration during sleep and to detect the presence and severity of sleep apnea. Measurement of peripheral electromyographic activity may be used to detect abnormal movement during sleep. Most polysomnographic studies are conducted during the person's usual sleeping hours-that is, at night. However, daytime polysomnographic studies also are used to quantify daytime sleepiness.
Most dreams occur in the REM stage, although they can and do occur at any stage. Dreams are the mind's way of determining future possibilities. There are generally considered to be three levels of state of mind, although different names may be used for the different levels by different authorities. They are as follows - subconscious, conscious, and superconscious. The subconscious level stores all past information gathered by the physical and spiritual senses and filters out what is necessary to the conscious level or present level. The present or conscious level determines the best possibilities to take to get to the superconscious level or future. Dreams are the mind's outlet to do this in the safest manner possible, much like different computer programs to determine the outcomes of car crash tests without smashing a car or maiming actual human occupants. Any number of factors can play into a dream depending on the upbringing and background of the person doing the dreaming. The outcomes can be quite accurate. Many creative minds including artists, musicians, scientists and so on, have been provided solutions that had taken many months or even years of laborious research without end only to fall asleep and dream about it.
Dreams usually fall into one of the categories below, although this list is not all inclusive:
Dreams also allow the body to physically repair itself and some say for the spirit side of us to travel to other dimensions, distances, realities, and so on.
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