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In the fourth century B.C., Plato wrote, "Even in good men there is a lawless wild-beast nature, which peers out in sleep." Early last century, Freud called dreaming "a temporary psychosis." But modern sleep laboratory research debunked the notion that psychosis represents intrusion of the dream state into waking life.

In 1952 researchers at the University of Chicago discovered that sleep involved two distinct states alternating in 90-minute cycles. In one state, brain activity resembled that of waking, and eyes darted rapidly beneath closed lids. They dubbed it rapid eye movement, or REM, sleep. In the other state, brain activity slowed down and eyes were quiescent. They called this state non-REM, or NREM.

Early studies showed that about 85 percent of awakenings from REM sleep elicited reports of stories that subjects identified as dreams, while few awakenings in NREM sleep did.

The recognition that healthy normal subjects spend as much as two hours dreaming each night prompted researchers to seek the function of such activity in the time-honored way—they removed it and assessed the results.

William Dement, M.D., now at Stanford University School of Medicine, awakened sleepers as soon as they entered the REM state. Once subjects fell back to sleep, however, they returned to REM sleep almost immediately. On days after nights in which subjects were deprived of REM sleep, they reported anxiety, irritability, and difficulty concentrating. Depriving people of NREM sleep did not have these effects.

Researchers initially theorized that nightly dreaming served as a psychological safety valve to protect people from emotional storms in their waking life. They suspected that prolonged dream deprivation would produce psychotic symptoms in healthy people, but studies showed that did not happen. Nor did persons with schizophrenia suffer intensified psychotic symptoms when deprived of REM sleep. The latter finding, according to Gerald Vogel, M.D., of Emory University Medical School, "was the final, fatal blow to the notion that REM-sleep deprivation was psychologically harmful."

As laboratory dream collections grew, he said, researchers found that sleepers reported dreams from both REM and NREM sleep, showing that REM sleep is not necessary for dreaming or even for dreams that are bizarre or disorganized. Indeed, most dreams prove to be mundane, organized, ordinary stories. "The mystery about dreams," Vogel asserted, "is not that they are distorted but that even during sleep, the mind/brain produces organized, coherent, understandable stories."—L.L.