In deep, or slow-wave, sleep, both cats and humans show slight muscle tension and low brain activity. But Dr. Jouvet found that during periods of REM sleep the muscles of cats were completely slack, even though their brain waves suggested physical activity. He called the REM state “paradoxical sleep,” since the brain is active even though the body is virtually still.
“Dreaming became the third state of the brain, as different from sleep as sleep was from waking,” Dr. Jouvet wrote in “The Paradox of Sleep: The Story of Dreaming,” published in France in 1993 and in English six years later.
He determined that a structure within the brainstem called the pons governed cats’ REM sleep. The pons is responsible for basic biological functions, like breathing and sensory perception; by contrast, the cortex, a higher brain region, governs conscious thought and actions.
Many researchers at the time assumed that since dreaming seemed to be a complex intellectual process, it would be centralized in the part of the brain responsible for reasoning. Dr. Jouvet’s discovery suggested that REM sleep could continue without the involvement of higher brain structures and that it had an important biological function even for animals with little capacity for reasoning.
Research has since confirmed that human beings have brain structures that govern REM sleep similar to those found in cats. Most warm-blooded animals, like mammals and birds, have periods of REM sleep. (Dolphins and many species of whales are notable exceptions.)
The question of whether animals dream was asked millenniums ago by Aristotle and has since occurred to virtually anyone who has watched a pet twitching in a deep sleep. Dr. Jouvet, who cautioned that there was no way for people to know for certain whether animals have what we call dreams, made a startling discovery while observing their behavior with his fellow researchers.
When certain minute structures within a cat’s pons were destroyed in experiments, he found, the cat began to move during periods of REM sleep — movements suggestive of walking, stalking prey, grooming or acting aggressively — all without reacting to outside stimuli.
The cat was exhibiting what Dr. Jouvet called “oneiric behavior,” meaning behavior related to dreams, using a word derived from the Greek word for dream, “oneiros.” He theorized that what had been destroyed in the experiments were the cerebral structures that had inhibited the cat’s motion while it was sleeping, and that the cat had been reacting to its dreams physically.
“How can we wake a cat during paradoxical sleep and ask it questions?” Dr. Jouvet wrote. “We cannot, but the discovery and analysis of oneiric behavior would lead us to believe that cats do dream.”
In 1986, many years after Dr. Jouvet’s discovery of oneiric behavior in cats, a study by Carlos Schenck and Mark Mahowald at the Minnesota Regional Sleep Disorders Center in Minneapolis pointed to a similar phenomenon in humans. The study detailed a medical condition called REM behavior disorder, in which a sleeping person acts out violently in the throes of a vivid dream. The disorder can usually be controlled with a low dose of a sedative.
Dr. Jouvet also conducted early research on Modafinil, a stimulant used to successfully treat narcolepsy and other sleep disorders. Modafinil, intended to promote wakefulness with a lower risk of addiction than amphetamines, has become popular as a so-called smart drug.
Michel Jouvet was born in Lons-le-Saunier, in eastern France, on Nov. 16, 1925. His father was a physician. As a young man Mr. Jouvet fought with the French Resistance in World War II.
After the war he studied anthropology and ethnography, but his father eventually persuaded him to enter medical school at the University of Lyon. He became a neurosurgical resident there in 1951, and in 1954 he traveled to Long Beach, Calif., to work with the neurophysiologist H. W. Magoun, who with Giuseppe Moruzzi had identified the brain structure responsible for sleep.
Dr. Jouvet left Long Beach in 1955 to travel the world, then returned to France, where he earned his doctorate in 1956.
He became a research director at the French Institute of Health and Medical Research in 1966 and a professor and the director of the department of experimental medicine at what is now Université Claude Bernard Lyon 1 in 1968.
Survivors include his wife, Anne, and four children.
Over the decades Dr. Jouvet kept meticulous journals of his own dreams, studied writings about sleep and dreaming from antiquity onward, and wrote several books. One, a novel published in 1992, is titled “The Castle of Dreams.”
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