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Understanding Our Dreams
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15471 |
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Section : |
NATURAL SCIENCE
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| Issue
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12 / 1989 |
3,077 Words |
| Author
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David Foulkes
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It is banal but true: We are both fascinated and puzzled by our dreams. Where do they come from? What do they mean? Although not a high-priority item on today's scientific agenda, dreaming has become an object of increasing interest in recent years to both neuroscientists and cognitive scientists, who have begun to propound theories that challenge the long-standing hegemony of psychoanalysis.
Natural Science Theories
Physical or biological scientists tend to think that dreaming can be attributed to a peculiar pattern of brain functioning specific to the state of sleep. Nowadays, this view derives not only from a general frame of reference in which aberrant brain states but also from a particular discovery: REM sleep. Named for its accompanying rapid eye movements, REM sleep is a paradoxically aroused state that comprises about 25 percent of total sleep-time in adults. REM sleep was discovered at the University of Chicago in 1953 by Eugene Aserinsky and Nathaniel Kleitman, who also noted that adult volunteers reported detailed dreams on most awakenings from REM sleep and no dreams at all on most awakenings in the absence of REMs. The association of REM awakenings with reports of vivid dreaming has been confirmed in studies of thousands of adult volunteers worldwide.
Thus, recent natural scientific theories have focused on observed or hypothetical peculiarities of REM sleep to explain the seemingly mysterious properties of dream experience. Often, as in the theory of Nobel laureate Francis Crick and his colleague Graeme Mitchison, the focus is on REM sleep rather than on dreaming as such. Their theory, first advanced in 1983, proposes that the REM state involves a process of "reverse learning" or "unlearning," through which unwanted or "parasitic" neutral patterns are purged from the brain's repertoire. Dreaming is, in some unspecified way, a reflection of this unlearning process. Thus we dream not to heighten our awareness of any mental contents but rather to obliterate such contents. Evidence does suggest that most REM dreams are not remembered unless interrupted by an awakening. For Crick and Mitchison, the remembered and dwelled-upon dream is an unwitting failure of the mind-clearing process that is inherent in "unconscious" (i.e., unremembered) dreaming.
Other theories have been proposed in which the REM state is imagined to involve the consolidation, rather than the obliteration, of mental associations. Thus, Edmond Dewan of the Air Force-Cambridge Research Laboratories proposed the P (for Programming) Hypothesis in 1969, according to which REM sleep should increase in organisms undergoing much novel waking experience. Although there is some evidence that this is the case for other animals, there is little support for the hypothesis among humans. And as is also true of Crick and Mitchison's theory, the P Hypothesis is very vague on how proprieties of the experienced dream reflect the underlying brain processes assumed to be occurring in REM sleep. That is, neither theory makes a serious attempt to explain the general form of specific content of dreams.
More explicit is the activation-synthesis theory of Allan Hobson and Robert McCarley, first published in 1977 and publicized in Hobson's recent book The Dreaming Brain. Unlike the previous neuroscientific theories, the activation-synthesis theory starts not with a presumption about REM function but rather with an observation, specifically of the brain-stem
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