What do they mean, these dreams that occupy one fourth of a person's sleeping time?For the most part, those who explore the meaning and purpose of dreams have been steeped in myth and religion or in a coldly mechanistic view of the way the brain works.

But now a view of dreams is emerging from the scientific community that takes a more middle ground.

At the fourth annual conference last week of the Association for the Study of Dreams, scientists said that research into dreams is providing new information about memory formation, neurological development and personality.

While psychologists still see dreams, as Freud did, as "the royal road to the unconscious," many scientists now are explaining the process of dreaming, especially the images in dreams, primarily in biological terms.

Dr. Milton Kramer, president of the association and director of the Sleep Disorders Center of Greater Cincinnati, decried the "defacatory theory of dreams," which holds that dreams are no more than the brain's ridding itself of byproducts of a day's worth of stimulation.

"The dream has been dismissed as meaningless, meant to be forgotten," Kramer told participants at the three-day conference held at Marymount University in Arlington. "But I believe the dream has a meaning and the dream has a function."

On one side of the debate is Dr. Francis Crick, co-discoverer of the double helix of DNA and now a scientist at the Salk Institute for Biological Research in La Jolla, Calif. In 1983, Crick and his colleague Graeme Mitchison, a mathematician at Cambridge University, caused a stir among dream researchers when they wrote in the British journal Nature that "we dream in order to forget." The brain takes in each day more than it can ever incorporate, wrote Crick and Mitchison; dreams are the brain's way of dumping all the unneeded matter.

On the other side are the psychoanalysts, who for many years dominated the field of dream research. Sigmund Freud first proposed that dreams were a form of unconscious wish fulfillment and that their bizarre nature allowed a person to bring disturbing thoughts, in disguise, to the level of consciousness.

In arguments over why people dream, there is little doubt that dreaming serves some purpose. The question is what purpose.

Now, many psychiatrists think dreaming occurs not for wish fulfillment but for memory formation. "Dreaming is part of the information-processing structure of our minds," says Dr. Stanley Palombo, clinical associate professor of psychiatry at George Washington University. "In a dream, representations of the events of the current day are being matched up with events from the past that have been stored in permanent memory."

Dr. Rosalind Cartwright, director of the Sleep Disorders Service and Research Center at Rush-Presbyterian-St. Luke's Medical Center in Chicago, agrees that the dreamer compares the present with the past, but she says this occurs as a way of putting the day's experiences onto the "template of our personality." This process occurs without conscious effort, according to Cartwright; even for people who never remember them, dreams help find order in chaos.

The dream's real purpose is "sorting and associating our more emotional experiences of the day to earlier memories of similar emotional content," Cartwright says.

Latter-day psychoanalysts have put theories about the meaning and purpose of dreams into the context of what has been learned about sleep physiology. Scientists now know that people dream in cycles, moving from REM (rapid eye movement, or dreaming) sleep to other stages four or five times a night; that dreams are remembered only when they occur immediately before awakening; that dreaming occupies up to two hours a night; and that dream periods get progressively longer throughout the night, with the last dream lasting nearly an hour.New information about REM sleep has led Dr. Martin Seligman, a University of Pennsylvania psychologist, to a theory of dream structure that seems to synthesize the mechanistic and psychoanalytic poles. The theory, described in the lead article in the current issue of Behaviour Research and Therapy, begins with the observation that REM sleep comprises short bursts of eye "jiggling," followed by a minute or two of quiescence.

During the rapid eye movements, Seligman says, the sleeper reports experiencing visual hallucinations; during the intervals, his dream reports are more like emotional, almost intellectual, daydreaming, with no clear visual images.

These sporadic images occur against a background of a heightened emotional state, which results from the activation of the limbic system during REM sleep, Seligman says. And the dreamer, being an individual driven to find sense in chaos, takes these random images and inchoate emotions and imposes on them all a story line.

"If you want to look at the meaning of the dream," says Seligman, "don't look at the content of the visual bursts or the emotional storms. Look at the story line. The real dream activity is in the plot."

This is also the view of Dr. Allan Hobson, professor of psychiatry at Harvard University, who has been portrayed as one of the leading proponents of the biological view of dreams. According to Hobson, the brainstem is "switched on" during REM sleep and begins firing erratically. Because the sleeping brain shuts out external stimuli, it "generates its own signals," he says, which become the random, disconnected images of our dreams.

Like Seligman, Hobson says individuals try to impose meaning on those random images, and in doing so invent a narrative to make sense of them. That narrative, Hobson says, is the part of the dream that reveals something about the dreamer's personality and preoccupations.

Hobson has theorized that dreams are primarily a way for the brain to establish and maintain crucial circuitry. He speculates that "dreams may be a scientific read-out of the brain's own test system, sort of as if you're running all your programs without the clutch."

In direct contradiction to the Freudian interpretation of dreams, Hobson says the dream images themselves, which are the result of low-level firings of the brain, have no psychological significance.

"The dream process is a physiological Rorschach test," Hobson says. "It's our effort to impose meaning on a set of images over which we have no control."

Dreaming in utero and during early infancy may serve the related function of establishing important neural connections in the developing brain, Hobson says. He points out that fetuses during the last trimester spend all of their time in REM sleep, and newborns spend up to eight hours a day dreaming. "That's a lot of time to spend working on infantile wishes," he says in criticism of the pscyhanalytic view of dreams.

Hobson says the debate over dream function misses an important distinction between dreaming and the dream itself. "Dreaming is a process," he says, "and the dream is one's individual experience of that process. Once you make that distinction, a lot of the arguments turn out to be false."

The question of whether dreams are windows into the psyche or the result of non-significant brain activity is, Hobson says, "not an either/or issue; it's both/and."