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For other uses, see Dream (disambiguation).

Dreams are the images, thoughts and feelings experienced while asleep, particularly strongly associated with rapid eye movement sleep. The contents and purpose of dreams are poorly understood, though they have been a topic of speculation and interest throughout recorded history.

Neurology of dreams

There is no universally agreed biological definition of dreaming. General observation shows that dreams are strongly associated with rapid eye movement (REM) sleep, during which an electroencephalogram shows brain activity to be most like wakefulness. Participant-remembered dreams during non-REM sleep are normally more mundane in comparison.[1] During a typical lifespan, a human spends a total of about six years dreaming[2] (which is about 2 hours each night[3]). It is unknown where in the brain dreams originate, if there is a single origin for dreams or if multiple portions of the brain are involved, or what the purpose of dreaming is for the body or mind.

Stages of sleep

Main article: Sleep

When the body decides that it is time to sleep, neurons near the eyes begin to send signals throughout the body. According to J. Allan Hobson, these neurons are located in such close proximity to neurons that control eyelid muscles that the eyelids begin to grow heavy.[4] Glands begin to secrete a hormone that helps induce sleep and neurons send signals to the spinal cord which cause the body to relax.

Discovery of REM

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In 1953 Eugene Aserinsky discovered REM sleep while working in the lab of his PhD advisor. Aserinsky noticed that the sleepers' eyes fluttered beneath their closed eyelids, later using a polygraph machine to record their brain waves during these periods. In one session he awakened a subject who was crying out during REM and confirmed his suspicion that dreaming was occurring.[5] In 1953 Aserinsky and his advisor published the ground-breaking study in Science.[6]

In 1976, J. Allan Hobson and Robert McCarly proposed a new theory that changed dream research, challenging the previously held Freudian view of dreams as subconscious wishes to be interpreted. The 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 in 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 and McCarly'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.[7] 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.[8]

Continual-activation theory

Combining Hobson's activation synthesis hypothesis with Solms's 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 temporary 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).[9][10]

Dreams and 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.[11]

Location of hippocampus

Hippocampus and memory

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.[12] 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 Nadel hypothesize that these memories are then consolidated into a smooth narrative, similar to a process that happens when memories are created under stress.[13]

Functions of dreams

There are many hypotheses about the function of dreams.[14] During the night there may be many external stimuli bombarding the senses, but the mind interprets the stimulus and makes it a part of a dream in order to ensure continued sleep.[15] The mind will, however, awaken an individual if they are in danger or if trained to respond to certain sounds, such as a baby crying. Dreams may also 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.[16] Freud suggested that bad dreams let the brain learn to gain control over emotions resulting from distressing experiences.[14] Dreams also let the mind express things that would normally be suppressed in the waking world, thus keeping itself in harmony. Dreams may also offer a view at how future events might proceed; this is similar to running future events through the mind, for instance: a work presentation, a job interview, or a first date.

Jung suggested that dreams may compensate for one-sided attitudes held in waking consciousness.[17] Ferenczi[18] proposed that the dream, when told, may communicate something that is not being said outright. There have also been analogies made with the cleaning-up operations of computers when they are off-line. Dreams may remove parasitic nodes and other "junk" from the mind during sleep.[19][20] Dreams may also create 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. Blechner[21] calls this the theory of "Oneiric Darwinism." Dreams may also regulate mood.[22] Hartmann[23] 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 Griffin has lead to the formulation of the 'expectation fulfilment theory of dreaming', which suggests that dreaming metaphorically completes patterns of emotional expectation and lowers stress levels.[24][25]

Cultural history

Jacob's dream of a ladder of angels

Dreams have a long history both as a subject of conjecture and as a source of inspiration. Throughout their history, people have sought meaning in dreams or divination through dreams. They have been described physiologically as a response to neural processes during sleep, psychologically as reflections of the subconscious, and spiritually as messages from God or predictions of the future. Many cultures practiced dream incubation, with the intention of cultivating dreams that were prophetic or contained messages from the divine.

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.[26] 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.

Emotions

The most common emotion experienced in dreams is anxiety. Negative emotions are more common than positive feelings.[26] The U.S. ranks the highest amongst industrialized nations for aggression in dreams with 50 percent of U.S. males reporting aggression in dreams, compared to 32 percent for Dutch men.[26]

Gender differences

It is believed that in men's dreams an average of 70 percent of the characters are other men, while a female's dreams contain an equal number of men and women.[27] Men generally had more aggressive feelings in their dreams than women, and children's dreams did not have very much aggression until they reached teen age. These findings parallel much of the current research on gender and gender role comparisons in aggressive behavior. Rather than showing a complementary or compensatory aggressive style, this study supports the view that there is a continuity between our conscious and unconscious styles and personalities.

Sexual content

The Hall data analysis shows that sexual dreams show up no more than 10 percent of the time and are more prevalent in young to mid teens.[26] Another study showed that 8% of men's and women's dreams have sexual content.[28] In some cases, sexual dreams may result in orgasm or nocturnal emission. These are commonly known as wet dreams.[29]

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.[30]

Common themes

Content-analysis studies have identified common reported themes in dreams. These include: situations relating to school, being chased, running slowly/in place, sexual experiences, falling, arriving too late, a person now alive being dead, teeth falling out, flying, embarrassing moments, failing an examination, or a car accident. Twelve percent of people dream only in black and white.[31]

Disease-associated differences

There is evidence that certain diseases (normally only neurological diseases) can impact dreams. For instance, people with synesthesia have never reported black-and-white dreaming, and often have a difficult time imagining the idea of dreaming in black and white only.[32]

Dream interpretation

Main article: Dream interpretation

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.[33] 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.

Other associated phenomena

Lucid dreaming

Main article: 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.[34] The occurrence of lucid dreaming has been scientifically verified.[35]

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.[36]

Dreaming as a skeptical argument

Main article: Dream argument

Dreams can link to actual sensations, such as the incorporation of environmental sounds into dreams, or dreaming of urination while wetting the bed. Some philosophers have extended this idea to a skeptical hypothesis about ontology. The first recorded mention of the idea was by Zhuangzi, and was also discussed in Hinduism; Buddhism makes extensive use of the argument in its writings.[37] It was formally introduced to western philosophy by Descartes in the 17th century in his Meditations on First Philosophy.

Recalling dreams

Main article: Dream journal

The recall of dreams is extremely unreliable, though it is a skill that can be trained. 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. A dream journal can be used to assist dream recall, for psychotherapy or entertainment purposes.

Déjà vu

Main article: Déjà vu

The theory of déjà vu dealing with dreams indicates that the feeling of having previously seen or experienced something could be attributed to having dreamt about a similar situation or place, and forgetting about it until one seems to be mysteriously reminded of the situation or place while awake.[38]

Dream incorporation

In one use of the term, "dream incorporation" is a phenomenon whereby an external stimulus, usually an auditory one, becomes a part of a dream, eventually then awakening the dreamer. 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 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 .[39]

See also

Footnotes

  1. ^ Dement, W. (1957). "The Relation of Eye Movements during Sleep to Dream Activity.'". Journal of Experimental Psychology. 53: 89–97. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  2. ^ How Dream Works. 2006. Retrieved 2006-05-04.
  3. ^ "Brain Basics: Understanding Sleep". National Institute of Neurological Disorders and Stroke. 2006. Retrieved 2007-12-16.
  4. ^ Wade, Nicholas (1998). The Science Times Book of the Brain. Lyons.
  5. ^ Dement, William (1996). The Sleepwatchers. Springer-Verlag. ISBN 0964933802.
  6. ^ Aserinsky, E (1953). "Regularly occurring periods of eye motility, and concomitant phenomena, during sleep". Science. 118 (3062): 273–274. doi:10.1126/science.118.3062.273. PMID 13089671. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  7. ^ Solms, M. (2000). Dreaming and REM sleep are controlled by different brain mechanisms (23(6) ed.). Behavioral and Brain Sciences. pp. 793–1121.
  8. ^ Rock dreams are not always true., Andrea (2004). "3". The Mind at Night: The New Science of How and Why we Dream. Basic Books. ISBN 0465070698.
  9. ^ Zhang, Jie (2004). Memory process and the function of sleep (PDF) (6-6 ed.). Journal of Theoretics. Retrieved 2006-03-13.
  10. ^ Zhang, Jie (2005). Continual-activation theory of dreaming, Dynamical Psychology. Retrieved 2006-03-13.
  11. ^ Tarnow, Eugen (2003). How Dreams And Memory May Be Related (5(2) ed.). NEURO-PSYCHOANALYSIS.
  12. ^ R. Stickgold, J. A. Hobson, R. Fosse, M. Fosse1 (2001). "Sleep, Learning, and Dreams: Off-line Memory Reprocessing". Science. 294 (5544): 1052–1057. doi:10.1126. {{cite journal}}: Check |doi= value (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  13. ^ Jessica D. Payne and Lynn Nadel1 (2004). "Sleep, dreams, and memory consolidation: The role of the stress hormone cortisol". LEARNING & MEMORY: 671–678. ISSN 1072-0502.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  14. ^ a b Cartwright, Rosalind D (1993). "Functions of Dreams". Encyclopedia of Sleep and Dreaming.
  15. ^ Antrobus, John (1993). "Characteristics of Dreams". Encyclopedia of Sleep and Dreaming.
  16. ^ Vedfelt, Ole (1999). The Dimensions of Dreams. Fromm.
  17. ^ Jung, C. (1948) General aspects of dream psychology. In: Dreams. Princeton, NJ: Princeton University Press, 23-66.
  18. ^ Ferenczi, S. (1913)To whom does one relate one's dreams? In: Further Contributions to the Theory and Technique of Psycho-Analysis. New York: Brunner/Mazel, 349.
  19. ^ Evans, C. & Newman, E. (1964) Dreaming: An analogy from computers. New Scientist, 419:577-579.
  20. ^ Crick, F. & Mitchison, G. (1983) The function of dream sleep. Nature, 304:111-114.
  21. ^ Blechner, M. (2001) The Dream Frontier. Hillsdale, NJ: The Analytic Press.
  22. ^ Kramer, M. (1993)The selective mood regulatory function of dreaming: An update and revision. In: The Function of Dreaming. Ed., A. Moffitt, M. Kramer, & R. Hoffmann. Albany, NY: State University of New York Press.
  23. ^ Hartmann, E. (1995)Making connections in a safe place: Is dreaming psychotherapy? Dreaming, 5:213-228.
  24. ^ Griffin, J. (1997) The Origin of Dreams: How and why we evolved to dream. The Therapist, Vol 4 No 3.
  25. ^ Griffin, J, Tyrrell, I. (2004) Dreaming Reality: how dreaming keeps us sane or can drive us mad'. Human Givens Publishing.
  26. ^ a b c d Hall, C., & Van de Castle, R. (1966). The Content Analysis of Dreams. New York: Appleton-Century-Crofts. Content Analysis Explained
  27. ^ http://www.dreamresearch.net/Library/fmid8.html
  28. ^ Zadra, A., "1093: SEX DREAMS: WHAT DO MEN AND WOMEN DREAM ABOUT?" SLEEP, Volume 30, Abstract Supplement, 2007 A376.
  29. ^ http://www.measuredhs.com/pubs/pdf/FR157/04Chapter04.pdf Badan Pusat Statistik "Indonesia Young Adult Reproductive Health Survey 2002-2004" p. 27
  30. ^ Van de Castle, p. 340.
  31. ^ Michael Schredl, Petra Ciric, Simon Götz, Lutz Wittmann (November, 2004). "Typical Dreams: Stability and Gender Differences". The Journal of Psychology. 138 (6): 485. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |month= ignored (help)CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
  32. ^ Harrison, John E. (2001). Synaesthesia: The Strangest Thing. Oxford University Press. ISBN 0192632450.
  33. ^ Wegner, D.M., Wenzlaff, R.M. & Kozak M. (2004). "The Return of Suppressed Thoughts in Dreams" (PDF). Psychological Science. 15 (4): 232–236.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  34. ^ Lucid dreaming FAQ by 1The Lucidity Institute at Psych Web.
  35. ^ Watanabe, T. (2003). "Lucid Dreaming: Its Experimental Proof and Psychological Conditions". J Int Soc Life Inf Sci. 21 (1). ISSN 1341-9226.
  36. ^ Hajek P, Belcher M (1991). "Dream of absent-minded transgression: an empirical study of a cognitive withdrawal symptom". J Abnorm Psychol. 100 (4): 487–91. PMID 1757662.
  37. ^ Kher, Chitrarekha V. (1992). Buddhism As Presented by the Brahmanical Systems. Sri Satguru Publications. ISBN 8170302935.
  38. ^ Lohff, David C. (2004). The Dream Directory: The Comprehensive Guide to Analysis and Interpretation. Running Press 0762419628.
  39. ^ Alain, M.Ps., Geneviève (July 2003). "Replication of the Day-residue and Dream-lag Effect". 20th Annual International Conference of the Association for the Study of Dreams. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); line feed character in |work= at position 45 (help)

Further reading

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