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Dream

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For other uses, see Dream (disambiguation).
Pierre-Cécile Puvis de Chavannes: The Dream, 1883
File:SickGirlInPyjamas.jpg
A girl sleeps in her bed, before reaching REM sleep.

A dream is the experience of imagined images, voices, or other sensations during sleep. Dreams often portray events which are impossible or unlikely in reality, and are usually outside the control of the dreamer. Many people report experiencing strong emotions while dreaming, and frightening or upsetting dreams are referred to as nightmares. The scientific discipline of dream research is oneirology.

Dreams have a long history both as a subject of conjecture and as a source of inspiration (artistic or otherwise). Throughout history, people have sought meaning in dreams. They have been described physiologically as a response to neural processes during sleep, psychologically as reflections of the unconscious, and spiritually as messages from God or predictions of the future (oneiromancy).

Most scientists believe that almost all humans dream with approximately the same frequency. Even those who rarely recall dreams report having them if awakened during rapid eye movement REM sleep. Dreaming in animals varies from species to species.

Understanding dreams

Neurology of dreams

There is no universally agreed-upon biological definition of dreaming. Dreams are typically associated with REM sleep, a phase of brain activity which occurs towards the end of the sleep cycle. REM sleep is characterized by rapid horizontal eye movements, stimulation of the pons, increased respiratory and heart rate, and temporary paralysis of the body. Subjects awakened during REM sleep usually report having been dreaming. However, a small fraction of subjects also report dreaming in other phases of sleep. Some neurologists even group mental phenomena such as daydreaming under the umbrella of dreaming.

Some studies on time sense during dreams have determined that a subject's sense of time during a dream closely matches their time sense during waking activity. In other words, if a dream feels like it lasted twenty minutes, these studies suggest it was indeed about twenty minutes. However, other studies have found this to be inaccurate. Thus, there is some debate regarding the distribution of time in a dream corresponding to reality.

It is unknown where in the brain dreams originate — if there is such a single location — or why dreams occur at all. However, there are many competing theories of the neurology of dreams.

During a typical lifetime a person spends about 6 years dreaming[1] (which is about 2 hours each night[2]).

The activation synthesis theory developed by Allan Hobson and Robert McCarley asserts that the sensory experiences are fabricated by the cortex as a means of interpreting random 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.[3] Memory, attention and the other features lacking in the dream state are taken to depend on the neurotransmitters norepinephrine and serotonin, which are present in reduced concentrations during REM sleep. This chemical change is hypothesized to produce a psychotic state, as well as a lack of orientation.

In simpler terms, activation synthesis argues that at certain stages of sleep the brain will fire neurons randomly - perhaps to keep the brain warm during cold nights. To make sense of all these random and unrelated thoughts, the brain will construct a story or scenario to try and make sense of it all. Therefore, this theory is excellent in explaining the bizzare nature of dreams.

On the other hand, research by Mark Solms suggests that dreams are generated in the forebrain, and that REM sleep and dreaming are not directly related.[4]

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, and at the same time, dreaming and REM sleep are controlled by different brain mechanisms. The theory is developed through a series of hypotheses. By introducing a temporary memory stage into the memory process, Zhang first proposed that the memory formed during waking time is not saved directly into the long-term memory; instead it is saved into a temporary memory store. He, then, divides brain into two subsidiary systems: the conscious brain and the non-conscious brain. Zhang hypothesizes that the function of sleep is to process, encode and transfer the data from the temporary memory to the long-term memory. NREM sleep processes the conscious related memory (declarative memory); and REM sleep processes the non-conscious related memory (procedural memory). He further hypothesizes that both conscious and non-conscious subsidiary systems of brain have to be continually activated through their life times. When the level of activation of either subsidiary system descends to a given threshold, a continual-activation mechanism will be triggered to maintain brain continual activation. Zhang assumes that during REM sleep, the non-conscious part of brain is busy to process the procedural memory; in the meanwhile, the level of activation in the conscious part of 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 brain. Zhang suggests that this pulse-like brain activation is the inducer of each dream. He proposes that, with the involvement of brain associative thinking system, dreaming is, thereafter, self maintained with 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 scene changes (between two dreams).[5][6]

Eugen Tarnow suggests that dreams are ever present excitations of the long term memory system, even during waking life — McCarley also observes that when asked to recall their last thought, subjects often reported somewhat hallucinatory thoughts. The strangeness of dreams is then due to long-term memories being stored in "dream format"; this is reminiscent of the 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.

The English psychologist Stan Gooch suggests that dreams are a product of the Cerebellum, a part of the brain located at the rear of the cortex. The Cerebellum is a region of the brain that plays an important role in the integration of sensory perception and motor output. It also has its own set of optic fibres, which Gooch proposes as a reason for REM during sleep, in short, that a part of the brain connected to the eyes is still experiencing the dream as an image.

The Problem Solving Theory is another interpretation of the meaning of dreams. This theory explains that a dream solves problems and works out your daily problems in creative ways. The theory does explain that any symbols remembered or seen in the dream are what they are, meaning there is no underlying to them.

Supernatural interpretations of dreams

Main article: Oneiromancy

The mysterious and often bizarre nature of dreams has led many to interpret dreams as divine gifts or messages, as predictions of the future, or as messages from the past. Alternatively, the idea of the "dream world" as real and the "day world" as imagined is another supernatural interpretation of dreams. Profound dreams believed to be sent by God have led to conversion to another religion.

Oneiromancy, prediction of the future through the interpretation of dreams, holds great credence in ancient Judeo-Christianity: in the Tanakh, Jacob, Joseph and Daniel are given the ability to interpret dreams by Yahweh; in the New Testament, divine inspiration comes as a dream to Saint Joseph, the husband of Mary, when the Angel Gabriel spoke to him in a dream and told him that the baby Mary was carrying was God's. After the visit of the Three Wise Men to them in Bethlehem, an angel appeared to him and told him to take Mary and Jesus to Egypt for their safety. The angel appeared again in a dream to tell him when it was safe to return to Israel. The story of Saint Patrick and his conversion of the people of Ireland also features dreaming. When Patrick was enslaved in Antrim he was told by God in a dream that there was a boat waiting in Wicklow to bring him back to his homeland. Some years later Patrick dreamt that the Irish were calling him to return and convert them to Christianity.

Western philosophers of a skeptical bent (notably René Descartes) have pointed out that dream experiences are indistinguishable from "real" events from the viewpoint of the dreamer, and so no objective basis exists for determining whether one is dreaming or awake at any given instant. One must, they argue, accept the reality of the waking world on the basis of faith. Lucid dreaming provides a counter-argument to this theory as it's practitionaries hold that they are in varying degrees aware of their dreaming state, often completely aware and able to dominate the dream with concious actions.

Psychodynamic interpretation of dreams

Main article: Dream interpretation

Both Sigmund Freud and Carl Jung identify dreams as an interaction between the unconscious and the conscious. They also assert together that 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.

Other

Dreams of Absent Minded Transgression

Dreams of Absent Minded Transgression (DAMT) are dreams where the individual dreaming absentmindedly performs an action that they have been trying to stop (a classic example being a smoker trying to quit dreams of lighting a cigarette). Subjects that have had DAMT dreams have reported awaking with intense feelings of guilt. Some studies have shown that DAMT dreams are positively correlated with successfully stopping the behavior compared to control subjects who did not experience these dreams.[7]

Dreaming as a skeptical argument

Main article: dream argument

While one dreams a non-lucid dream one will not realise one is dreaming. This has led philosophers to the idea that one could be dreaming right now (or atleast one can't be certain that they're not dreaming). First formally introduced by Descartes in Meditations on First Philosophy, the dream argument has become one of the most popular skeptical hypotheses.

See also

References

Cited

  1. ^ How Dream Works. 2006. Retrieved 2006-05-04.
  2. ^ Brain Basics: Understanding Sleep. 2006. Retrieved 2006-05-04.
  3. ^ Hobson, J.A. (1977). The brain as a dream state generator: An activation-synthesis hypothesis of the dream process (134 ed.). American Journal of Psychiatry. pp. 1335–1348. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ Solms, M. (2000). Dreaming and REM sleep are controlled by different brain mechanisms (23(6) ed.). Behavioral and Brain Sciences. pp. 793–1121.
  5. ^ Zhang, Jie (2004). Memory process and the function of sleep (PDF) (6-6 ed.). Journal of Theoretics. Retrieved 2006-03-13.
  6. ^ Zhang, Jie (2005). Continual-activation theory of dreaming, Dynamical Psychology. Retrieved 2006-03-13.
  7. ^ Hajek P, Belcher M. (1991). "Dream of absent-minded transgression: an empirical study of a cognitive withdrawal symptom". Journal of Abnormal Psychology. Retrieved Feb 25. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)

General

  • Crick, F. & Mitchinson, G. (1983) The function of dream sleep. Nature 304, 111-114.
  • Tarnow, E. (2003) How Dreams And Memory May Be Related. Neuro-Psychoanalysis 5(2), 177-182 and also [1]

Further reading

External links

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