Dreams are successions of
images,
ideas,
emotions and
sensations occurring involuntarily in the
mind during certain stages of
sleep. The content and purpose of dreams are not yet understood, though they have been a topic of speculation and interest throughout recorded history. The scientific study of dreams is known as
oneirology.
The cultural meaning of dreaming
, c. 1690, by
Michael Willmann|thumb|250px]]
Throughout history, people have sought
meaning in dreams or
divination through dreams. Dreams have also been described
physiologically as a response to neural processes during sleep;
psychologically as reflections of the
subconscious; and
spiritually as messages from
god, the deceased, predictions of the future, or from the Soul. Many cultures practice
dream incubation with the intention of cultivating dreams that are
prophetic or contain messages from the
divine.
Judaism has a traditional ceremony named Hatavat Halom. Literally meaning "making the dream a good one", through this rite disturbing dreams can be transformed to give a positive interpretation by a rabbi or a rabbinic court.
The Neurobiology of dreaming
showing brainwaves during REM sleep]]
There is not a universally accepted biological definition of dreaming. In 1952,
Eugene Aserinsky identified and defined
rapid eye movement (REM) sleep while working in the surgery of his
PhD advisor. Aserinsky noticed that the sleepers' eyes fluttered beneath their closed eyelids, later using a
polygraph machine to record their
brainwaves during these periods. In one session, he awakened a subject who was wailing and crying out during REM and confirmed his suspicion that dreaming was occurring. In 1953, Aserinsky and his advisor published the ground-breaking study in
Science.
Accumulated observation has shown that dreams are strongly associated with Rapid Eye Movement during which an electroencephalogram (EEG) shows brain activity to be most like wakefulness. Participant-remembered dreams during NREM sleep are normally more mundane in comparison. During a typical lifespan, a person spends a total of about six years dreaming (which is about two hours each night). Most dreams only last 5 to 20 minutes. As a result, motor neurons are not stimulated, a condition known as REM atonia. This prevents dreams from resulting in dangerous movements of the body.
According to a report in the journal Neuron, rat brains show evidence of complex activity during sleep, including the activation in memory of long sequences of activity. Studies show that various species of mammals and birds experience REM during sleep, and follow the same series of sleeping states as humans. As methods of introspection were replaced with more self-consciously objective methods in the social sciences in 1930s and 1940s, dream studies dropped out of the scientific literature. Dreams were neither directly observable by an experimenter nor were subjects' dream reports reliable, being prey to the familiar problems of distortion due to delayed recall, if they were recalled at all. According to Sigmund Freud, dreams are more often forgotten entirely, perhaps due to their prohibited character. Altogether, these problems seemed to put them beyond the realm of science.
The discovery that dreams take place primarily during a distinctive electrophysiological state of sleep, rapid eye movement (REM) sleep, which can be identified by objective criteria, led to the rebirth of interest in this phenomenon. When REM sleep episodes were timed for their duration and subjects woken to make reports before major editing or forgetting could take place, it was determined that subjects accurately matched the length of time they judged the dream narrative to be ongoing to the length of REM sleep that preceded the awakening. There is no "time dilation" effect; a five-minute dream takes roughly five minutes of real time to play out. This close correlation of REM sleep and dream experience was the basis of the first series of reports describing the nature of dreaming: that it is a regular nightly, rather than occasional, phenomenon, and a high-frequency activity within each sleep period occurring at predictable intervals of approximately every 60–90 minutes in all humans throughout the life span. REM sleep episodes and the dreams that accompany them lengthen progressively across the night, with the first episode being shortest, of approximately 10–12 minutes duration, and the second and third episodes increasing to 15–20 minutes. Dreams at the end of the night may last as long as 15 minutes, although these may be experienced as several distinct stories due to momentary arousals interrupting sleep as the night ends. Dream reports can be reported from normal subjects on 50% of the occasion when an awakening is made prior to the end of the first REM period. This rate of retrieval is increased to about 99% when awakenings are made from the last REM period of the night. This increase in the ability to recall appears to be related to intensification across the night in the vividness of dream imagery, colors and emotions.
Activation synthesis theory
In 1976
J. Allan Hobson and
Robert McCarley proposed a new theory that changed dream research, challenging the previously held
Freudian view of dreams as subconscious wishes to be interpreted.
Activation synthesis theory asserts that the sensory experiences are fabricated by the cortex as a means of interpreting
chaotic signals from the
pons. They propose that during REM sleep, the ascending
cholinergic PGO (ponto-geniculo-occipital) waves stimulate higher
midbrain and
forebrain cortical structures, producing rapid eye movements. The activated forebrain then synthesizes the dream out of this internally generated information. They assume that the same structures that induce REM sleep also generate sensory information.
Hobson's 1976 research suggested that the signals interpreted as dreams originated in the brain stem during REM sleep. However, research by Mark Solms suggests that dreams are generated in the forebrain, and that REM sleep and dreaming are not directly related. While working in the neurosurgery department at hospitals in Johannesburg and London, Solms had access to patients with various brain injuries. He began to question patients about their dreams and confirmed that patients with damage to the parietal lobe stopped dreaming; this finding was in line with Hobson's 1977 theory. However, Solms did not encounter cases of loss of dreaming with patients having brain stem damage. This observation forced him to question Hobson's prevailing theory which marked the brain stem as the source of the signals interpreted as dreams. Solms viewed the idea of dreaming as a function of many complex brain structures as validating Freudian dream theory, an idea that drew criticism from Hobson. In 1978, Solms, along with partners William Kauffman and Edward Nadar, undertook a series of traumatic-injury impact studies using several different species of primates, particularly howler monkeys, in order to disprove Hobson's postulation that the brain stem played a significant role in dream pathology. Unfortunately, Solms' experiments proved inconclusive, as the high mortality rate associated with using a hydraulic impact pin to artificially induce brain damage in test subjects meant that his final candidate pool was too small to satisfy the requirements of the scientific method.
Continual-activation theory
Combining Hobson's activation synthesis hypothesis with Solms' findings, the continual-activation theory of dreaming presented by
Jie Zhang proposes that dreaming is a result of brain activation and synthesis; at the same time, dreaming and REM sleep are controlled by different brain mechanisms. Zhang hypothesizes that the function of sleep is to process, encode and transfer the data from the
short-term memory to the
long-term memory, though there is not much evidence backing up this so-called "consolidation."
NREM sleep processes the conscious-related memory (declarative memory), and REM sleep processes the unconscious related memory (procedural memory).
Zhang assumes that during REM sleep the unconscious part of a brain is busy processing the procedural memory; meanwhile, the level of activation in the conscious part of the brain will descend to a very low level as the inputs from the sensory are basically disconnected. This will trigger the "continual-activation" mechanism to generate a data stream from the memory stores to flow through the conscious part of the brain. Zhang suggests that this pulse-like brain activation is the inducer of each dream. He proposes that, with the involvement of the brain associative thinking system, dreaming is, thereafter, self-maintained with the dreamer's own thinking until the next pulse of memory insertion. This explains why dreams have both characteristics of continuity (within a dream) and sudden changes (between two dreams).
Dreams as excitations of long-term memory
Eugen Tarnow suggests that dreams are ever-present excitations of
long-term memory, even during waking life. The strangeness of dreams is due to the format of long-term memory, reminiscent of
Penfield & Rasmussen's findings that electrical excitations of the
cortex give rise to experiences similar to dreams. During waking life an executive function interprets long-term memory consistent with reality checking. Tarnow's theory is a reworking of Freud's theory of dreams in which Freud's unconscious is replaced with the long-term memory system and Freud's "Dream Work" describes the structure of long-term memory.
Dreams for strengthening of semantic memories
A 2001 study showed evidence that illogical locations, characters, and dream flow may help the brain strengthen the linking and consolidation of
semantic memories. These conditions may occur because, during REM sleep, the flow of information between the
hippocampus and
neocortex is reduced. Increasing levels of the
stress hormone
cortisol late in sleep (often during REM sleep) cause this decreased communication. One stage of
memory consolidation is the linking of distant but related memories. Payne and Nadal hypothesize these memories are then consolidated into a smooth narrative, similar to a process that happens when memories are created under stress.
Dreams for removing junk
Robert (1886), a physician from Hamburg, was the first who suggested that dreams are a need and that they have the function to erase (a) sensory impressions which were not fully worked up and (b) ideas which were not fully developed during the day. By the dream work incomplete material will be either removed or deepened and included into memory. Robert's ideas were cited repeatedly by Freud in his Traumdeutung.
Hughlings Jackson (1911) viewed that sleep serves to sweep away unnecessary memories and connections from the day. This was revised in 1983 by Crick and Mitchison's "
reverse learning" theory, which states that dreams are like the cleaning-up operations of computers when they are off-line, removing parasitic nodes and other "junk" from the mind during sleep. However, the opposite view that dreaming has an information handling, memory-consolidating function (Hennevin and Leconte, 1971) is also common. Dreams are a result of the spontaneous firings of neural patterns while the brain is undergoing memory consolidation during sleep.
Dreams as resonance in neural circuits
During sleep the eyes are closed, so that the brain to some degree becomes isolated from the outside world. Moreover all signals from the
senses (except
olfaction) must pass through the
thalamus before they reach the
brain cortex, and during sleep thalamic activity is suppressed. This means that the brain mainly works with signals from itself. A well-known phenomenon in dynamical
physical systems where the level of input and output from the system is low is that
oscillation makes spontaneous
resonance patterns to occur. Hence, dreams may be the simple consequence of
neural oscillation.
Psychology of sleep and dreams
Dreams for testing and selecting mental schemas
Coutts describes dreams as playing a central role in a two-phase sleep process that improves the mind's ability to meet human needs during wakefulness. During the accommodation phase, mental schemas self-modify by incorporating dream themes. During the
emotional selection phase, dreams test prior schema accommodations. Those that appear adaptive are retained, while those that appear maladaptive are culled. The cycle maps to the sleep cycle, repeating several times during a typical nights sleep.
Alfred Adler suggested that dreams are often emotional preparations for solving problems, intoxicating an individual away from common sense toward private logic. The residual dream feelings may either reinforce or inhibit contemplated action.
Evolutionary psychology theories of dreams
Numerous theories state that dreaming is a random by-product of REM sleep physiology and that it does not serve any natural purpose . Flanagan claims that "dreams are evolutionary epiphenomena" and they have no adaptive function in the least. "Dreaming came along as a free ride on a system designed to think and to sleep ." Hobson, for different reasons, also considers dreams to be epiphenomena. He believes that the substance of dreams have no significant influence on waking actions, and most people go about their daily lives perfectly well without remembering their dreams . Hobson proposed the activation-synthesis theory, which states that “there is a randomness of dream imagery and the randomness synthesizes dream-generated images to fit the patterns of internally generated stimulations .” This theory is based on the physiology of REM sleep, and Hobson believes dreams are the outcome of the forebrain reacting to random activity beginning at the brainstem. Overall, this theory has obtained broad support for a while because it corresponds to physiological data and its explanation of dreaming applies to a majority of peoples’ random dream experiences . The activation-synthesis theory hypothesizes that the peculiar nature of dreams is attributed to certain parts of the brain trying to piece together a story out of what is essentially bizarre information .
However, evolutionary psychologists believe dreams serve some adaptive function for survival.
Deirdre Barrett describes dreaming as simply "thinking in different biochemical state" and believes people continue to work on all the same problems—personal and objective—in that state. Her research finds that anything—math, musical composition, business dilemmas—may get solved during dreaming, but the two areas especially likely to help are 1) anything where vivid visualization contributes to the solution, whether in artistic design or invention of 3-D technological devices and 2) problem where the solution lies in "thinking outside the box"—i.e. the person is stuck because conventional wisdom on how to approach the problem is wrong. In a related theory, which
Mark Blechner terms "Oneiric Darwinism," dreams are seen as creating new ideas through the generation of random thought mutations. Some of these may be rejected by the mind as useless, while others may be seen as valuable and retained. Finnish psychologist Antti Revonsuo posits that dreams have evolved for "threat simulation" exclusively. According to the Threat Simulation Theory he proposes, during much of human evolution physical and interpersonal threats were serious, giving reproductive advantage to those who survived them. Therefore dreaming evolved to replicate these threats and continually practice dealing with them. In support of this theory, Revonsuo shows that contemporary dreams comprise much more threatening events than people meet in daily non-dream life, and the dreamer usually engages appropriately with them . It is suggested by this theory that dreams serve the purpose of allowing for the rehearsal of threatening scenarios in order to better prepare an individual for real-life threats.
A more extensive view of ‘dreaming as play’ is proposed by Humphrey who proposes we dream to practice many different physical, intellectual and social skills, not just to eveolve past threats .
The main competitors against this kind of theory regard dreaming as a necessary by-product of random cortical activation, which occurs for other reasons . Crick and Mitchison believe that “cortical neural networks become overloaded during learning and that the function of REM sleep is to remove superfluous connections by randomly flooding them .” In other words this theory believes we dream so that we can forget.
Psychosomatic theory
Dreams are a product of "dissociated imagination," which is
dissociated from the conscious self and draws material from sensory memory for simulation, feedback resulting in hallucination. By simulating the sensory signals to drive the autonomous nerves, dreams can affect mind-body interaction. In the brain and spine, the autonomous "repair nerves," which can expand the blood vessels, connect with compression and pain nerves. Repair nerves are grouped into many chains called meridians in Chinese medicine. When a repair nerve is prodded by compression or pain to send out its repair signal, a chain reaction spreads out to set other repair nerves in the same meridian into action. While dreaming, the body also employs the meridians to repair the body and help it grow and develop by simulating very intensive movement-compression signals to expand the blood vessels when the level of growth enzymes increase.
Other hypotheses on dreaming
There are many other hypotheses about the function of dreams, including:
Dreams allow the repressed parts of the mind to be satisfied through
fantasy while keeping the conscious mind from thoughts that would suddenly cause one to awaken from shock.
Freud suggested that bad dreams let the brain learn to gain control over emotions resulting from distressing experiences.
Ferenczi proposed that the dream, when told, may communicate something that is not being said outright.
Dreams regulate mood.
Hartmann says dreams may function like psychotherapy, by "making connections in a safe place" and allowing the dreamer to integrate thoughts that may be dissociated during waking life.
More recent research by psychologist
Joe Griffin, following a twelve-year review of data from all major sleep laboratories, led to the formulation of the
expectation fulfilment theory of dreaming, which suggests that dreaming metaphorically completes patterns of emotional expectation in the autonomic nervous system and lowers stress levels in mammals.
Dream content
From the 1940s to 1985,
Calvin S. Hall collected more than 50,000 dream reports at
Western Reserve University. In 1966 Hall and Van De Castle published
The Content Analysis of Dreams in which they outlined a coding system to study 1,000 dream reports from college students. It was found that people all over the world dream of mostly the same things. Hall's complete dream reports became publicly available in the mid-1990s by Hall's protégé
William Domhoff, allowing further different analysis.
Personal experiences from the last day or week are frequently incorporated into dreams. In some cases, sexual dreams may result in
orgasms or
nocturnal emissions. These are colloquially known as
wet dreams.
Recurring dreams
While the content of most dreams is dreamt only once, many people experience recurring dreams—that is, the same dream narrative is experienced over different occasions of sleep. Up to 70% of females and 65% of males report recurrent dreams.
Color vs. black and white
A small minority of people say that they dream only in black and white.
Dream interpretations
Dreams were historically used for healing (as in the
asclepieions found in the
ancient Greek temples of
Asclepius) as well as for guidance or divine inspiration. Some
Native American tribes used
vision quests as a rite of passage, fasting and praying until an anticipated guiding dream was received, to be shared with the rest of the tribe upon their return.
During the late 19th and early 20th centuries, both Sigmund Freud and Carl Jung identified dreams as an interaction between the unconscious and the conscious. They also assert together that the unconscious is the dominant force of the dream, and in dreams it conveys its own mental activity to the perceptive faculty. While Freud felt that there was an active censorship against the unconscious even during sleep, Jung argued that the dream's bizarre quality is an efficient language, comparable to poetry and uniquely capable of revealing the underlying meaning.
Fritz Perls presented his theory of dreams as part of the holistic nature of Gestalt therapy. Dreams are seen as projections of parts of the self that have been ignored, rejected, or suppressed. Jung argued that one could consider every person in the dream to represent an aspect of the dreamer, which he called the subjective approach to dreams. Perls expanded this point of view to say that even inanimate objects in the dream may represent aspects of the dreamer. The dreamer may therefore be asked to imagine being an object in the dream and to describe it, in order to bring into awareness the characteristics of the object that correspond with the dreamer's personality.
Relationship with medical conditions
There is evidence that certain medical conditions (normally only neurological conditions) can impact dreams. For instance, some people with
synesthesia have never reported entirely black-and-white dreaming, and often have a difficult time imagining the idea of dreaming in only black and white.
Therapy for recurring nightmares (often associated with posttraumatic stress disorder) can include imagining alternative scenarios that could begin at each step of the dream. Arthur Schopenhauer said: "A dream is a short-lasting psychosis, and a psychosis is a long-lasting dream." In the field of psychoanalysis, Sigmund Freud wrote: "A dream then, is a psychosis," and Carl Jung: "Let the dreamer walk about and act like one that is awake and we have the clinical picture of dementia praecox."
McCreery has sought to explain these similarities by reference to the fact, documented by Oswald, that sleep can supervene as a reaction to extreme stress and hyper-arousal. McCreery adduces evidence that psychotics are people with a tendency to hyper-arousal, and suggests that this renders them prone to what Oswald calls "microsleeps" during waking life. He points in particular to the paradoxical finding of Stevens and Darbyshire that patients suffering from catatonia can be roused from their seeming stupor by the administration of sedatives rather than stimulants.
Griffin and Tyrrell go so far as to say that "schizophrenia is waking reality processed through the dreaming brain."
Other associated phenomena
Lucid dreaming
Lucid dreaming is the conscious perception of one's state while dreaming. In this state a person usually has control over characters and the environment of the dream as well as the dreamer's own actions within the dream. The occurrence of lucid dreaming has been scientifically verified.
Oneironaut is a term sometimes used for those who lucidly dream.
Dreams of absent-minded transgression
Dreams of absent-minded transgression (DAMT) are dreams wherein the dreamer absentmindedly performs an action that he or she has been trying to stop (one classic example is of a quitting smoker having dreams of lighting a cigarette). Subjects who have had DAMT have reported waking with intense feelings of
guilt. One study found a positive association between having these dreams and successfully stopping the behavior.
The "dream world" and the "real world"
During the night there may be many external stimuli bombarding the senses, but the brain often interprets the stimulus and makes it a part of a dream in order to ensure continued sleep. Dream incorporation is a phenomenon whereby an actual sensation, such as environmental sounds, are incorporated into dreams, such as hearing a phone ringing in a dream while it is ringing in reality or dreaming of
urination while
wetting the bed. The mind can, however, awaken an individual if they are in danger or if trained to respond to certain sounds, such as a baby crying. Except in the case of lucid dreaming, people dream without being aware that they are doing so. Some philosophers have concluded that what we think of as the "real world" could be or is an illusion (an idea known as the
skeptical hypothesis about
ontology). There is a famous painting by
Salvador Dalí that depicts this concept, titled "
Dream Caused by the Flight of a Bee around a Pomegranate a Second Before Awakening" (1944). The first recorded mention of the idea was by
Zhuangzi, and is also discussed in
Hinduism makes extensive use of the argument in its writings. It was formally introduced to Western philosophy by
Descartes in the 17th century in his
Meditations on First Philosophy. Stimulus, usually an auditory one, becomes a part of a dream, eventually then awakening the dreamer. The term "dream incorporation" is also used in research examining the degree to which preceding daytime events become elements of dreams. Recent studies suggest that events in the day immediately preceding, and those about a week before, have the most influence.
Recalling dreams
The recall of dreams is extremely unreliable, though it is a skill that can be trained. Dreams can usually be recalled if a person is awakened while dreaming. Dreams that are difficult to recall may be characterized by relatively little
affect, and factors such as
salience,
arousal, and interference play a role in dream recall. Often, a dream may be recalled upon viewing or hearing a random trigger or stimulus. A
dream journal can be used to assist dream recall, for
psychotherapy or entertainment purposes. For some people, vague images or sensations from the previous night's dreams are sometimes spontaneously experienced in falling asleep. However they are usually too slight and fleeting to allow dream recall. At least 95% of all dreams are not remembered. Certain brain chemicals necessary for converting short-term memories into long-term ones are suppressed during REM sleep. Unless a dream is particularly vivid and if one wakes during or immediately after it, the content of the dream will not be remembered.
Déjà vu
One theory of déjà vu attributes the feeling of having previously seen or experienced something to having dreamt about a similar situation or place, and forgetting about it until one seems to be mysteriously reminded of the situation or the place while awake.
Apparent precognition
According to surveys, it is common for people to feel their dreams are predicting subsequent life events. The multi-faceted nature of dreams makes it easy to find connections between dream content and real events.
In one experiment, subjects were asked to write down their dreams in a diary. This prevented the selective memory effect, and the dreams no longer seemed accurate about the future. Another experiment gave subjects a fake diary of a student with apparently precognitive dreams. This diary described events from the person's life, as well as some predictive dreams and some non-predictive dreams. When subjects were asked to recall the dreams they had read, they remembered more of the successful predictions than unsuccessful ones.
Popular culture
Modern
popular culture often conceives of dreams, like Freud, as expressions of the dreamer's deepest fears and desires. In films such as
Spellbound (1945),
The Manchurian Candidate (1962) and
Inception (2010), the protagonists must extract vital clues from surreal dreams.
Most dreams in popular culture are, however, not symbolic, but straightforward and realistic depictions of their dreamer's fears and desires.
In speculative fiction, the line between dreams and reality may be blurred even more in the service of the story.
See also
Cognitive Neuroscience of Dreams
Daydream
Dimethyltryptamine
Dream argument
Dream art
Dream dictionary
Dream pop
Dream sequence
Dream speech
Dreamwork
Dream world (plot device)
Dream Yoga
Lilith a 6000 year old Sumerian dream demon (succubus)
List of dream diaries
Lucid Dream
Morpheus (mythology)
Oneiromancy
Spirit spouse (in dreams)
Veridical dream
References
Further reading
Lombardo G.P., Foschi R. (2008), Escape from the dark forest: The experimentalist standpoint of the Sante De Sanctis dreaming psychology. History of the Human Sciences. vol. 21, pp. 45–69 ISSN: 0952-6951.
Klemp, H. (1999). The art of spiritual dreaming. Minneapolis, MN: Eckankar.
External links
Dream Psychology by Sigmund Freud
The Dream & Nightmare Laboratory in Montreal
Archive for Research in Archetypal Symbolism website
The International Association for the Study of Dreams
More information on the expectation fulfilment theory of dreaming
Dreams at the Open Directory Project
Category:Personal life
Category:Psychotherapy
Category:Symbols
