Deep sleep: are humans wired to dream?

Dreaming: An Introduction to the Science of Sleep. By J. Allan Hobson. Oxford University Press, 192 pp., $14.95 paperback.

The Paradox of Sleep: The Story of Dreaming. By Michel Jouvet. MIT Press, 227 pp., 820.00 paperback.

NOT LONG AGO I had a conversation with a Roman Catholic bishop who is an excellent administrator, a thoughtful leader and a world traveler. We met in his office not far from the burial place of Bishop Frederick Baraga, a 19th-century missionary to the Ojibwa known as the "snowshoe priest"--a beloved figure among Indian people and the creator of the first Ojibwa dictionary. When our conversation turned to personal and pastoral matters, I happened to ask the bishop about dreams. He responded cordially, but with a touch of amusement: "I don't dream." When I asked what training he'd received over the years on working with dreams, he replied, "None. At least none that I can recall having any impact on me."

Should this good, wise bishop be interested, there is a fascinating world awaiting him. In the 1990s the scientific study of sleep and dreams catapulted into public awareness because of a federal initiative that funded brain research. Using sophisticated computer-driven imaging techniques like PET (positive emission tomography) and the MRI (magnetic resonance imaging), researchers opened up new details about the operation of the brain.

After a decade of study, two tightly written volumes by distinguished neuroscientists have emerged, each posing varied perspectives on this body of research. J. Allan Hobson is professor of psychiatry at Harvard Medical School. Michel Jouvet is a member of the French Academy of Sciences and professor of experimental medicine at the University of Lyons. Both neurologists remind us that all warm-blooded mammals dream, to various degrees, each and every night. Though we may not remember these nightly excursions into our own personal psychic landscapes, research continues to confirm what was first reported from electronic monitoring during the 1953 landmark studies at the University of Chicago: we're wired to dream.

Human beings sleep in episodic stages of REM (rapid eye movement) and non-REM cycles. Dreaming is associated with REM sleep. Dream sleep accounts for about 20 percent of adult sleep time. Children and infants spend 60 to 80 percent of their sleep time in the dream state. Certain pharmaceuticals, including barbiturates (sleep medications), as well as alcohol, repress REM sleep. Studies show that if dream sleep is repressed, the brain will compensate during following sleep cycles with increased REM sleep. And when REM activity is suppressed, people may sleep longer but don't feel fully rested.

Hobson, recipient of the Distinguished Scientist Award from the Sleep Research Society, examines dreaming through the lens of physiology. He lays out the complexity of thermoregulation during the dream state, the shifting interplay of neurotransmitters, and the profusion of chemicals that every second fire off billions of neural connections in the thinking-sleeping brain.

Interestingly, Hobson has reservations about common pharmacological interventions in brain function. In a description of a sleep disorder known as RBD, in which patients enact their dreams through movement, he notes that a deficiency of dopamine (a specific brain neurotransmitter) is one key marker of Parkinson's disease. He suggests, chillingly, that the prolonged use of antidepressants known as SSRIs can lead to RBD. Accordingly, he warns against long-term use of such psychotropic medications when treating depression and anxiety disorders.

Hobson casually dismisses any notion that dreams have a deep, nonphysiological meaning. He calls such notions "the mystique of fortune cookie dream interpretation." He holds up the "formal functions" of sleep states, emphasizing several critical physiological forces at play in the dreaming brain. One of the first signs of sleep deprivation, he notes, is the breakdown of the skin. Even a slight decrease in REM sleep causes a measurable drop in immune function. Thermoregulation is also affected when brains are deprived of the dream state. In lab studies, sleep-deprived rats have been invaded by bacteria from their own bowels. These lab rodents, Hodson graphically reports, are "eaten up by normally symbiotic hitchhikers that were no longer satisfied just to go along for the ride."

Every night sleep revives our emotional life and reinforces basic brain mechanisms that allow us to fight, flee, feed and procreate. A physiological restoration happens during REM sleep. Hobson is persuasive and straightforward on this point and on the goal of his research: "In the place of dream mystique," he writes, "we aim to install dream science. And the science we intend to install has a solid, firm base in neurobiology."

JOUVET'S ESSAYS take readers on a scientific and sociological tour of the history of sleep and dream research. Regarded by many of his peers as the world's leading sleep and dream researcher, he identifies the dream state as a distinct, vital "third state" of" mental activity to be respected for its unique function. For Jouvet, the function of dreaming is to restore, protect and preserve individuality.