History of the Study of Dreams
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Dreaming Contents History of the Study of Dreams The Interpretation of Dreams The Psychology of Dreams Dreams, Psychopathology, Psychotherapy Dreaming and Psychiatric Disorders Neurobiology of Dreaming History of the Study of Dreams R Cartwright, Rush University Medical Center, Chicago, IL, USA ã 2013 Elsevier Inc. All rights reserved. Glossary Imagery rehearsal therapy: A treatment program for Activation-synthesis theory: Hobson and McCarley theory the control of nightmares through practice during that dreams are initially random images that acquire waking of pleasant visual images. meaning following arousal. Incorporation: Inclusion in the dream report of an Atonia: Abrupt loss of muscle tone at the onset of rapid eye external stimulus. movement (REM) sleep. Mood regulation function: Dream reports Dream: A hallucinatory experience during sleep consisting are initially negative in emotion and progressively of visual images related in a story-like structure, which are become more positive at the end of the accepted as reality at the time. night. EMs: Eye movements during a REM period, which vary in Nightmares: Strongly unpleasant dreams that speed and density. These may relate to the visual content of awaken the dreamer with full recall of the dream the dream. story. The Early History of Laboratory Investigation of Dreams continuity of the reported dream story. REM periods were divided into those that were continuous and those that were Dreams have been a source of interest throughout human interrupted by a body movement. The dream reports from history. However, much of this literatureELSEVIER does not meet the these episodes were judged as being either a continuous narra- criteria of being a ‘study.’ This article will cover only investiga- tive or one with an abrupt change to another story. The data tions that test a hypothesis. Such studies began in the mid- analysis showed that REM periods, free of body movement, 1950s when laboratory-monitored sleep proved dreams could yield continuous dream reports while those with one or more be elicited reliably by awakening sleepers from a specific neu- body movements were associated with reports of unrelated rophysiological state known as rapid eye movement (REM) dreams. This established that REM sleep is typically free of sleep. This article will cover some highlights of the research body movements and that their presence interferes with that followed. dream continuity. This study led to the addition of a chin muscle monitor, in recognition that loss of muscle tone is a reliable signal of the onset of REM sleep and thus the likely Hypothesis: Dreams are Related to REM Sleep presence of dreaming. Characteristics Another hypothesis tested whether the reported dream is related to the type of eye movements (EMs) that precede the Early sleep studies, and more recent brain imaging work, hy- awakening. The EMs were divided into those that were large pothesized that REM sleep determines the psychological char- (high amplitude) and dense (occurring in bursts) versus those acteristics of dreams. The first such study hypothesized that that were slower and sparser. A significant association was found body movement within a REM period would disrupt the between the activity of the EMs and a dream story in which the 124 Encyclopedia of Sleep http://dx.doi.org/10.1016/B978-0-12-378610-4.00028-0 Dreaming | History of the Study of Dreams 125 dreamer was engaged in some activity. As per reports following Hypothesis: Dreams are Related to Each Other Within sparse EMs, the dreamer was passive or was ‘just observing.’ the Night Studies correlating REM characteristics and dream features waned following the publication of the Hobson and McCarley Testing the relation of dreams to each other found these were activation-synthesis theory of dream construction. These neu- not obviously similar within the night nor did all the dreams of roscientists had located the cells involved in initiating REM a night make up one continuous story. The conclusion was that sleep to be in the pons, an area at the base of the brain. They dreams are independent stories but with some elements in argued that as this excitation traveled upward through the common, and that those that were similar were not always occipital cortex, random visual images were stimulated. These found in reports from adjacent REM periods. Since in only a acquired meaning only during arousal when the higher brain few cases was the same theme expressed throughout all the areas attempt to make sense of these inherently meaningless dreams of a night, it was concluded that, at the level of the images. Later, brain imaging studies, using positron emission manifest content, dreams are not related to each other. This tomography (PET) scans and functional magnetic resonance raised the question of whether the experimental awakenings imaging (fMRI), identified patterns of brain areas that are more were disrupting a natural continuity of the dreams. Further or less active in REM sleep than in waking, or in nonrapid eye study showed the amount of time spent awake for the sleeper movement (NREM) sleep and the relation of these to the to report their dream was negatively related to the continuity known function of these brain areas. These studies added between that dream and the report from the next REM awak- specificity to the description of REM as a highly activated ening. The longer the time awake, the less the continuity was. brain state. Finding strong activity in the limbic and paralimbic Although awakenings from REM yielded a report of dream- cortex (the amygdala, hypothalamus, the anterior cingulate) ing 80% of the time, those from nonrapid eye movement supports that dreams are more likely to involve negative emo- (NREM) sleep yielded widely varied percentages of dream re- tions. The deactivation of the prefrontal cortex accounts for the ports. The highest percent was found at sleep onset. More difficulty remembering dreams and the weakening of reality typically, NREM reports differed in quality from REM reports. testing (accepting the dream as if real). Dream reports collected They were described as less imagistic and more thought-like, during these imaging studies verified that dreams were being less emotional and more pleasant than the highly emotional, experienced during a specific pattern of increased and de- unpleasant reports from REM. To test whether the failure to creased brain activity in healthy persons but these varied in find continuity between dreams of the same night was because different clinical samples. This moved the dream interpretation the dream theme was set prior to the first REM, the next question back from being a waking afterthought to being due investigation collected samples from both NREM and REM to the particular brain areas active in the REM state. sleep, sampling all Electroencephalography (EEG) stages of sleep. Sleepers were awakened either 30 or 90 min following sleep onset by a coin toss. The coin toss was repeated following Hypothesis: Dream Images are Internally Generated each report to determine the timing of the next awakening. This resulted in 6–9 reports each night in random sequences of Early experiments attempted to test whether the images reported various sleep stages. The reports were examined for repeated in dreams could be influenced by applying a variety of external images or themes in the manifest content. Sometimes, the stimuli during an ongoing REM episode. They first used an initial report was from a NREM stage before any REM had auditory tone, a flashing light, and a spray of water, followed occurred. Repeated elements were found in different sequences by a doorbell to awaken the sleeper to report their experience. of sleep stages. Testing continuity of the sleeping mind using None of these stimuli was ‘markedly effective’ in modifying the this random awakening schedule presents a real difficulty: ongoing dream. Another study used auditory stimuli of spoken repeated elements may be present but missed if the random proper names, two of which were emotionally salient and two protocol skipped a time when reports were most connected. were neutral. The finding was that half of the dream reports In conclusion, there were nights with little or no repeated ele- showed some effect although this wasELSEVIER not by a direct inclusion ments and others when these were plentiful in both NREM and of the names but by a similarity in sound of a word in the report REM sleep. During nights when these were frequent, they were to the stimulus name (via assonance). Familiar names, their also the most vivid and memorable of the reported dream but own or those of ex-girlfriends, were more likely to have an effect were embedded into distinctly independent contexts, suggesting on the dream content than neutral names. The finding that that they were driven by intense preoccupations (possibly pre- emotional stimuli have more effect on dream content than conscious day residues), which then interfaced in sleep with those neutral in tone has been a repeated finding. ongoing unconscious (latent) dream thoughts. The conclusion To test whether the auditory stimuli had more effect on was that there is an interaction of preconscious and unconscious dreams than the visual, because the receptor organs (ears) streams of thought throughout sleep but that the methods used were open in sleep while the eyes were not, volunteers were to analyze dreams were not appropriate to identify these. tested while sleeping with their eyes taped open. Once REM was identified, an experimenter held up an object in front of the sleeper’s eyes, before they were awakened to give a dream report. Judges attempted to match these reports to the stimulus Hypothesis: Dreams Relate to the Presleep object. As they were not able do this at a rate better than Waking State chance, the conclusion was that dream images are internally generated and only on rare occasions are external stimuli re- The findings of the TV study reported above pushed the ques- sponsible for some element of a dream.