Science Ventures into Dreamland
Scientific study of dreams began in earnest in 1953 when research ers at the University of Chicago verified that a dream is likely to be in progress during rapid eye movement (REM). This phase of sleep is characterized by fluttering eyelids and other physiological symptoms, combined with particular brain-wave patterns.
What really is a dream? There is no definitive answer to this question. Science can explain a great deal about the mechanics of dreaming, but the exact substance of a dream and the reason why people have dreams remain a mystery. Some scientists believe that dreams are created only by the interplay of chemicals in the brain and have no psychological or spiritual value. Others believe that dreams are vital to the total health and the survival of a person and to the survival of humanity.
THE PHYSICAL PROCESS OF DREAMING
Dreaming originates in the brain stem and is controlled by neurotransmitters that turn dreams on and off. The “on switch” uses acetylcholine to begin the dream. The “off switch” uses norepinephrine and serotonin to end it. Norepinephrine and serotonin are necessary to imprint messages in long-term memory, which may explain why we forget the majority of our dreams. Since the two chemicals are suppressed during the dreaming process, dreams cannot be stored in long-term memory without help, such as writing them down or recording them upon awakening.
When the chemicals are suppressed, the acetylcholine allows electrical signals to be sent to the cortex. The brain stem neurons also start a theta rhythm in the hippocampus. This is a seahorse-shaped brain structure believed responsible for memory storage. Meanwhile, the nerves that usually carry information from the out-side world shut down.
If the dream occurs during the REM phase of sleep, the sleeper experiences increased heart and respiration rates and a state of temporary paralysis. The brain stem freezes muscular activity to prevent the sleeper from acting out his or her dream.
TYPES OF DREAMS
Dreams differ significantly according to when in the sleep pattern they occur. There are four stages of non-REM (NREM) sleep that precede REM sleep. As the sleeper descends through stages one through four, brain waves decrease in frequency. After reaching stage four, the sleeper reverses the process and ends up back in stage one. Then REM sleep begins, when the most vivid dreaming takes place. The stages are:
1 Light sleep, in which the brain shifts from the alpha waves of wake-fulness to theta waves of sleepiness. It is easy to awaken someone in light sleep. Fragmentary dream images are common, including jumbled images, voices, and sensations of falling.
2 Deepening sleep, characterized by mostly theta waves. This stage usually lasts only a few minutes.
3 Deep sleep, in which the theta waves slow to delta.
4 Deep sleep, in which more than half of the brain wave activity is in delta, with the remainder in theta. It is difficult to awaken a person in deep sleep.
These stages then reverse, and REM sleep begins.
All mammals (except the spiny anteater) and a few types of birds and reptiles experience REM sleep. In humans REM sleep decreases with age. Fetuses as young as 23 weeks spend nearly all their time in REM, and newborns spend about eight hours per day in REM. Up to 50 percent of the sleep of infants and small children is spent in REM. Adult sleep is 20 percent REM; for the elderly it is only 15 percent.
Four or five REM stages occur nightly, at about 90-minute intervals. The length of each session increases as the night goes on, until the average adult has spent about two hours in REM by morning.
People awakened during REM sleep are highly likely to remember their dreams, which differ from NREM dreams in their vivid-ness, complexity, and generally bizarre nature. External factors such as noises can be immediately incorporated into REM dreams. For example, the sound of a car door slamming outside may become an explosion in a dream.
Non-REM dreams are more logical and concern current or recent events in the dreamer’s life. These are the “day residues” defined by Sigmund Freud.
Hypnagogic dreams occur as we fall asleep, in the gray “twilight” between consciousness and sleep. Hypnagogic dreams are characterized by jumbled words and images, especially faces. Similar dreams are experienced in the hypnapompic state, which is the “twilight” that occurs in the transition from sleep to wakefulness.
WHY PEOPLE DREAM
The ancients were certain that the purpose of dreams was to learn the future, receive guidance, and heal the body. Most scientists agree that dreaming—at least REM dreaming— plays a part in the learning process. Theta waves are active in the hippocampus during REM, and the hippocampus is involved in memory processing. In humans the hippocampus doesn’t become functional until the age of two, the earliest age that most people can remember their dreams.
Some psychologists believe dreams to be compensatory and heal-ing; they help people process and balance their emotions. Individuals see personal and spiritual benefit to dreaming, with help for solving problems, getting ideas, and providing help in major life transitions.
Clinical psychologist and dream researcher Montague Ullman advanced the hypothesis that our dreams are not concerned primarily with people as individuals, but rather with the survival of the human species. Granted, individuals are the stars of their nightly shows, but looking beyond the personal meanings of dreams, it can be seen that they do address a larger social arena. Dreams reveal to people their state of connectedness to the whole of humanity, and how they feel about it, according to Ullman.
The human species has been so fragmented into different cultures and geographies that the survival of the whole is at risk, said Ullman. Dreaming holds humanity together.
Got questions about dreams? Following are answers to the most common things people want to know.
Do people dream every night?
Scientific research indicates that, with few exceptions, everyone dreams every night. A small number of people who have suffered brain damage experience a loss of dreaming. How people cope depends on the extent of brain damage and its effects on the nervous system and senses. Some people experience difficulty sleeping.
Why are dreams sometimes hard to remember?
Stress, food, and medication can affect sleep patterns and in turn affect recall ability. Also, natural chemicals in the brain that are related to memory decrease during sleep.
Does everyone dream in color?
About 75 percent of people dream in color. More women dream in color than men. It’s not unusual to dream primarily in color and also occasion-ally have black-and-white dreams.
How long do dreams last?
Most dreams are very short, ranging from a half-minute or so to several minutes in length. Some dreams can run as long as 15 to 20 minutes.
Do men and women dream differently?
Women’s dreams contain more dialogue, social interaction, emotion, and detail. Men’s dreams contain more action and male figures, and less dialogue. Women’s dreams more often set indoors and men’s dreams are more often set outdoors.
The implicate order is the seamless whole of the universe, the unbroken continuum of all things. It is a deep level of reality that contains all time and yet is timeless. It holds all potentiality. It is fluid. From the implicate order unfolds the explicate order, which is what we know as our physical reality. There is a constant flow of energy between the two orders.
Ullman said that the wisdom that flows into our dreams may come from the implicate order: the infinite source. Dreams may be a bridge into the explicate order, or physical reality as part of our evolution.
One thing is clear from scientific research: Dreaming is necessary to maintain physical health. In controlled laboratory experiments, people prevented from REM dreaming become anxious or even panicky, fatigued, irritable, and have difficulty concentrating and remembering. If deprived of sleep long enough, they eventually dream while awake, that is, they hallucinate. When finally allowed their REM sleep, their brains compensate for lost time by greatly increasing the percentage of sleep spent in the REM stage.
Another possible biological function of dreaming relates to the body’s maintenance of the proper balance of hormones. During REM sleep, there are higher levels of hormones in the body than at other times. Some neurons are dormant during REM, and this period may function to restore and replenish them.
During NREM sleep great amounts of growth hormone, which is responsible for body tissue renewal, enter the bloodstream. REM sleep may aid in brain tissue renewal.