Brains in Dreamland Scientists hope to raise the neural curtain on sleep's virtual theater.
Freud's efforts culminated in the 1900 publication of The Interpretation of Dreams. In that book, he depicted dreams as symbolic stories in which sleepers' unconscious sexual and aggressive desires play out in disguised forms.
Later in his life, Freud acknowledged that dreams don't always gratify wishes. For instance, he noted that some dreams represent attempts to master a past traumatic experience. Yet the father of psychoanalysis always held that dreams contain both surface events and subterranean themes of great personal importance. For that reason, he wrote, "the interpretation of dreams is the royal road to a knowledge of the unconscious activities of the mind."
Freud's theory of how dreams work has had a huge cultural impact over the past century, even as it attracted intense criticism. Now, brain scientists--members of the discipline that Freud left behind--have stepped to the forefront of this passionate dream dispute.
One prominent group of scientists asserts that Freud profoundly misunderstood dreams. In their, view, the act of dreaming yields a guileless collage of strange but heartfelt images that carry no hidden meanings.
These scientists say that dreaming occurs when a primitive structure called the brain stem stirs up strong emotions, especially anxiety, elation, and anger. At the same time, neural gateways to the external world shut down, as do centers of memory and rational thought. The brain then creates bizarre, internal visions that strongly resonate for the dreamer.
An opposing view corresponds in many ways to Freud's ideas. Its supporters portray dreams as products of a complex frontal-brain system that seeks out objects of intense interest or desire. When provoked during sleep, this brain system depicts deep-seated goals in veiled ways so as not to rouse the dreamer.
A third group of investigators regards the brain data as intriguing but inconclusive. Dreams may serve any of a variety of functions, they argue. Depending on the society, these uses include simulating potential threats, grappling with personal and community problems, sparking artistic creativity, and diagnosing and healing physical illnesses.
"It is striking that 100 years after Freud [published The Interpretation of Dreams], there is absolutely no agreement as to the nature of, function of, or brain mechanism underlying dreaming," says neuroscientist Robert Stickgold of Harvard Medical School in Boston.
A broad consensus exists on one point, though. If neuroscientists hope to understand the vexing relationship of brain and mind, they need to get a handle on dreams.
Freud's royal road to the unconscious looks like a scientific dead-end to psychiatrist J. Allan Hobson. Neuroscientific evidence indicates that the sleeping brain churns out dreams as an afterthought to its other duties, argue Hobson, Stickgold, and Edward F. Pace-Schott, also of Harvard Medical School.
"Unconscious wishes play little or no part in dream instigation, dream emotion is uncensored and undisguised, sleep is not protected by dreaming, and dream interpretation has no scientific status," Hobson says.
Hobson's assault on Freudian dream theory began more than a decade ago. At that time, he proposed that dreams result from random bursts of activity in a brain stem area that regulates breathing and other basic bodily functions. These brain stem blasts zip to the frontal brain during periods of rapid eye movement (REM) sleep, when the entire brain becomes nearly as active as when a person is awake.
Dreams most often occur during REM sleep. A slumbering individual enters REM sleep about every 90 minutes.
Hobson's group published a revision of this theory in the December 2000 BEHAVIORAL AND BRAIN SCIENCES. Their new approach grants that dreams harbor emotional significance, but not in the way Freud posited.
Brain imaging and sleep-laboratory data clearly delineate among wakefulness, REM sleep, and non-REM sleep, the Harvard scientists note.
Three essential processes during REM sleep make it the prime time for dreaming, they say. First, brain stem activity surges and sets off responses in emotional and visual parts of the brain. Second, brain regions that handle sensations from the outside world, control movement, and carry out logical analysis shut down. Third, brain stem cells pump out acetylcholine, a chemical messenger that jacks up activity in emotional centers.
At the same time, two neurotransmitters essential for waking activity--noradrenaline and serotonin--take a snooze.
The result, in Hobson's view: a vivid hallucination, informed by strong emotions, that takes bizarre twists and turns. REM sleep's biological makeup fosters the mistaken belief that one is awake while dreaming, saps the ability to reflect on the weirdness of dreams as they occur, and makes it difficult to recall dreams after waking up.
REM sleep conducts far more important business than dreaming, Hobson argues. Its central functions may include supporting brain development, regulating body temperature, fortifying the immune system, and fostering memories of recently learned information. The last possibility evokes heated scientific debate (SN: 7/22/00, p. 55).
Hobson's theoretical focus on brain stems and REMs doesn't do dreams justice, argues neuropsychologist Mark Solms of St. Bartholomew's and Royal London (England) School of Medicine.
"Dreaming is generated under the direction of a highly motivated, wishful state of mind," Solms holds. "I won't be at all surprised if we find that Freud's understanding of [dream] mechanisms was basically on the right track."
To dream, the brain--both in and out of REM sleep--stimulates a frontal-lobe system that orchestrates motivation and the pursuit of goals and cravings, the British scientist proposes. A neurotransmitter called dopamine ferries messages in the brain's motivation system.
The crux of Solms' argument rests on studies of brain-damaged patients. In rare instances where people incur injuries only to their brain stem, dreaming continues despite severe disruptions of REM sleep. In contrast, people who suffer damage to frontal-brain regions involved in motivation report that they no longer dream but still have nightly REM sleep. These individuals also become apathetic and lose much of their initiative, imagination, and ability to plan. This group includes several hundred mental patients who decades ago, as a therapy, had some of their frontal-brain nerve fibers surgically cut.
Additional support for Solms' view comes from brain-imaging studies indicating that frontal areas involved in motivation, emotion, and memory exhibit elevated activity during REM sleep.
Various forms of cerebral activation can trigger the motivation system and lead to dreaming, Solms suggests. This explains why vivid dreams occur shortly after falling asleep and in the morning, not just in the depths of REM sleep, he says.
Brain data can't yet confirm or disprove Freud's idea that dreams play a symbolic game of hide-and-seek with unconscious desires, Solms adds.
For now, something of a standoff exists between the dreaming-brain theories of Hobson and Solms. Hobson and his coworkers welcome the possibility, raised by neuroscientist Tore A. Nielsen of the University of Montreal, that crucial elements of REM sleep operate in non-REM states as well. For instance, as people fall asleep they display slow eye movements and electrical activity in the brain and muscles that may constitute a kind of "covert REM activity," Nielsen says.
If the REM state in one form or another saturates much of sleep, then the brain stem and related emotional centers create dreams throughout the night, Hobson asserts.
Solms regards "covert REM" as a hazy concept. REM sleep consists of diverse physiological changes in the brain and body. This sleep stage can't be equated with a few of its biological components that may appear at other times during the night, he contends.
Haziness also afflicts attempts to decipher dreams with recordings of brain activity, remarks neuroscientist Allen Braun of the National Institutes of Health in Bethesda, Md. These images of neural tissue show where the brain is stirring during specific sleep stages, Braun says, but not how those areas operate or whether they play a direct role in dreaming.
Brain-imaging reports generally support Solms' theory that dreams derive from a frontal-brain motivation system, Braun notes (SN: 1/17/98, p. 44). However, a frontal-brain area considered pivotal for self-monitoring and abstract thought naps throughout sleep. Braun considers this finding to clash with the Freudian notion of dreams as hotbeds of disguised meaning.
Freud's emphasis on wish fulfillment in dreams needs revision too, according to neuroscientist Antti Revonsuo of the University of Turku in Finland. Dreaming instead enables people to simulate threatening events so that they can rehearse ways to either deal with or avoid them, Revonsuo theorizes.
Threatening incidents of various kinds and degrees frequently appear in the dream reports of adults and children around the world, the Finnish scientist says. They also show up in descriptions of recurrent dreams, nightmares, and post-traumatic dreams.
Hunter-gatherer populations, such as the Mehinaku Indians in Brazil, report many dreams about threatening events, he adds. Mehinaku men's dreams range from fending off an attacking jaguar to dealing with an angry wife.
Revensuo's theory faces threats of its own, though. Evidence from contemporary hunter-gatherers indicates that dreaming functions in a variety of ways, argues psychologist Harry T. Hunt of Brock University in St. Catharines, Ontario. Members of these groups generally view dreams as real events in which a person's soul carries out activities while the person sleeps.
Hunter-gatherers' dreams sometimes depict encounters with supernatural beings who provide guidance in pressing community matters, aid in healing physical illnesses, or give information about the future, Hunt says. Individuals who are adept at manipulating their own conscious states may engage in lucid dreaming, in which the dreamer reasons clearly, remembers the conditions of waking life, and acts according to a predetermined plan.
Dreaming represents a basic orienting response of the brain to novel information, ideas, and situations, Hunt proposes. It occurs at varying intensities in different conscious states, including REM sleep, bouts of reverie or daydreaming, and episodes of spirit possession that individuals in some cultures enter while awake (SN: 2/17/01, p. 104).
Scientists, musicians, inventors, artists, and writers often use dreaming of one kind or another to solve problems and spark creativity, Hunt notes.
Whatever purposes dreaming serves, Hobson's group and many other researchers underestimate the extent to which the brain tunes in to the external world during sleep, says neuroscientist Chiara M. Portas of University College London. Several studies indicate that sensory areas of the brain respond to relevant sounds and other sensations during REM and non-REM sleep.
No conclusive results support any theory of dreaming or sleep, in her view.
Ironically, dreams are attracting growing scientific interest as they fade into the background of modern life. Artificial lighting and society's focus on daytime achievements have fueled this trend (SN: 9/25/99, p. 205).
Sleep now typically occurs in single chunks of 7 hours or less. Yet as recently as 200 years ago in Europe, people slept in two nightly phases of 4 to 5 hours each. Shortly after midnight, individuals awoke for 1 to 2 hours and frequently reflected on their dreams or talked about them with others.
Well before Freud's time, Europeans prized dreams for their personal insights, and particularly for what they revealed about a dreamer's relationship with God, says historian A. Roger Ekirch of Virginia Polytechnic Institute and State University in Blacksburg.
Organizing sleep into two segments encouraged people to remember dreams and to use them as paths to self-discovery, Ekirch contended in the April AMERICAN HISTORICAL REVIEW.
Dreams have lost their allure even for the psychoanalytic theorists and clinicians who are the heirs to Freud's ideas, remarks Paul Lippmann of the William Alanson White Psychoanalytic Institute in Stockbridge, Mass. These days, psychoanalysts show far more interest in dissecting the emotional nature of their dealings with patients than in eliciting and interpreting dreams, according to Lippmann, himself a psychoanalytic clinician.
Like Ekirch, Lippmann suspects that modern culture has eroded interest in dreaming. "The American Dream has little room for the nighttime variety," he said in the Fall 2000 PSYCHOANALYTIC PSYCHOLOGY.
Yet many neuroscientists seem determined to swim against that cultural tide. Even the researchers who see little psychological significance in sleep's visions want to explain how and why the brain produces them.
They can dream, can't they?
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|Title Annotation:||despite increased dream and brain research, there remains no consensus as to whether Sigmund Freud's dream theories were correct|
|Date:||Aug 11, 2001|
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