The archetypal uroboros, a mythological self-contained dragon, feasting on its own tail, exemplifies the intimately intertwined relationship between dreaming and learning. The ramifications of the 50,000 hours individuals typically devote to dreaming within a lifespan, are not confined to the sleep state. They shape the quality of interactions with the environment, others and the self, particularly influencing the acquisition of information that enhances functioning. Extending beyond reciprocity, this psychologically intriguing, and biologically pertinent (Hobson, 1988) alliance provides insights into the domains of memory, cognition, evolution and consciousness. Dreaming, a psychological state, and sleep, its behavioural counterpart, are both dependent on physiology (Hobson, 1988). The 1953 discovery of Rapid Eye Movements (REM) as a reliable physiological correlate of dreaming, ushered in dream research's golden age (Simmons Company, 1998). In 1977, publication of an activation-synthesis model of dreaming, suggested that dreaming sleep is physiologically determined by a "dream state generator" located in the brain stem (LaBerge, 1985). Individuals impose an order on the random bombardment of signals from the brainstem, that is interpreted as the narrative of the dream (Hobson, 1988 in Wolf, 1994). Significant similarity in REM patterns have been discovered in identical twins (Linn, 1988), suggesting genetic predeterminates of brain stem dream generator functioning. Elegantly constructed dreams that can serve as parables, suggest that higher order mental functioning influence lower order mechanisms of the dream state generator (LaBerge, 1985). Whereas Aristotle believed dreams arose from sensory imprints (Wolf, 1994), modern theories see dreaming as endogenous neurophysiological activity (Rossi, 1972). The neurotransmitter acetylcholine (ACh) plays a vital role in facilitating REM (Tuominen, 1997), with lesion studies indicating that the amount of REM is determined by the number of ACh neurons in the dorsolateral pons (Webster & Jones, 1988 in Tuominen, 1997). The ACh pathway critical to REM is found in the dorsolateral pons. Other pathways traverse the pedunculopontin tegmental nucleus and the laterodorsal tegmental nucleus, forming the reticular activating system which regulates arousal levels (Tuominen, 1997). Profound changes in neural activity, especially jagged ponto-geniculo-occipital (PGO) waves recorded from these regions, herald the onset of REM, prior to the cortical electroencephalograph (EEG) signs of REM, demonstrating how other brain regions are influenced by activity emanating from the pontine brainstem (Simmons Company, 1998). PGO waves are implicated in dream discontinuities (Wolf, 1994), disturbances to the higher cortical processing of pontine signals. Although cognitive activity during non-REM sleep has been ascertained, this has been identified as random thoughts, lacking the narrative and images associated with dreams (Wolf, 1994). During REM sleep, cognitive processes surpass waking cerebral activity. In the absence of external stimuli, an entirely hallucinatory environment is constructed in which the self is placed (Simmons Company, 1998). Throughout the sleep and wakefulness continuum (Wolf, 1994), the central nervous system represents reality from externally gleaned information. During waking experience, sensory input provides current data, contextual and motivational information. During sleep, sensory input is limited, with remnants of sensory data, and previous expectations constructing reality (LaBerge, 1996). In the dream state, perception occurs without the constraints of external sensory input (LaBerge, 1996). In light of this frenetic cognitive activity, sleep's contribution to enhanced learning ability cannot solely be ascribed to its quiescent properties. This intuitive hypothesis, is a vestige of archaic views that during sleep, brain activity is reduced and uniform (Hobson, 1988). Although the brain energy conservation theory as a complete explanation for the restorative properties that sleep bestows has been rejected, a recuperative theory has been selectively resuscitated. Findings that small cells, with large post-synaptic domains, whose functions are hallmarks of wakefulness – the capacity to attend to the world and learn about it (Hobson, 1988) – combine with evidence that they discharge regularly during waking, are most affected by neurotransmitter depletion, and show lowest levels of activity during REM episodes (Hobson, 1988). When their generation of action potentials is quelled during REM sleep, such cells manufacture enzymes in their nuclei which are transported through the axons into large post-synaptic domains. Upon awakening, transmitters are again available for release (Hobson, 1988). This guarantees rest for fatigue sensitive neurons (Hobson, 1988) which are critical for efficacious arousal. Simultaneously there is high level stereotypical activation of non-fatigueable neuronal circuits, the sensorimotor networks, which are phrenetically active during REM sleep. Since waking behaviour pattens are incomplete in activating neural connections, these circuits might otherwise atrophy through disuse (Hobson, 1988). According to this view REM sleep is an active maintenance program that allows daily flexing of sensorimotor programs in a safe setting, while fatigueable attentional programs are regenerated (Hobson, 1988), preserving a constancy of synaptic structure (Krüger, Obal, Kapas, & Fang, 1995). An antecedent of the concept of sleep as functionally rehabilitative, is the postulate that REM is neurologically constructive (Hobson, 1988), especially in prenatal periods of cortical development. The high proportion of REM experienced during periods of central nervous system plasticity suggests development as one of its functional aspects (Marks, Shaffery, Oksenberg, Speciale, & Roffwarg, 1995). REM sleep seems important for cerebral cortex and occulo-motor maturation and programming of developing neuronal circuits (Simmons Company, 1998). The function of REM in this developmental period of sensorimotor circuit may include activation trials that precipitate structural change (Hobson, 1988). Safe in the amniotic bath, poorly aimed movements are performed without risk in the virtuously weightless environment (Hobson, 1988). While suspended in this amniotic home (Wolf, 1994), the absence of experiential visual data or memory precludes formation of dream images. The bumps of intra-uterine life and the muffled maternal heartbeat (Wolf, 1994) are possibly incorporated in the intense internal source of stimulation that facilitates neuronal maturation. Fifteen hours of daily dreaming have been recorded in fetuses during the last trimester (Wolf, 1994), when doubling of cortical grey matter density (Faraday, 1972), rapid maturity, and preparation for independent survival occurs (Crick & Mitchinson,1984 in Mallon, 1989). Premature infants, confronted with mastering a limitless world of stimulation (LaBerge, 1985), through an immature nervous system, spend 80% of total sleep time engaged in dreaming (Faraday, 1972). Qualitative changes in children's dream construction between the ages of three and nine have been identified. Younger children's REM sleep reports are rare. They are brief, lack a narrative,self representation or activity by dream characters. Five to seven year olds' report length triples and contains these elements. By seven to nine years, adult like reports emerge. This development is strongly related to specific cognitive gains rather than psycho-social or emotional advancement. Waking measures of visuo-spatial construction are better predictors of dream reports than waking memories for visuo-spatial material or waking ability to describe visuo-spatial material. The increase in dream reports and narrative quality during development depends on cognitive skills involved in constructing dreams rather than skills involved in reporting them. This finding suggests that constructing dreams depends upon cognitive abilities to analyse, abstract, manipulate and construct visuo-patial images and ideas (Simmons Company, 1998). Cognitive advancement is matched by increased self awareness, and superior self representation, achievements thought to be enhanced by dreaming (Wolf, 1994). An innovative program to enrich the education of underprivileged children by encouraging exploration of dreams, stimulated children's imagination (Bourhenne, 1998), and was reflected in enhanced learning. REM sleep and neural plasticity decline concurrently (Mallon, 1989), however the directionality of the relationship is unknown. Differences between dreaming patterns of normal and disabled children have been identified (Carson, 1998). Dream time has been correlated with capacity to integrate information (Mallon, 1989). Unlike the inclusion of environmental noise in dream scripts identified in normal subjects, autistic children process incoming auditory signals similarly to neonates during REM sleep, suggesting developmental delay (Mallon, 1989). A phylogenic correlate is that precocious animals such as guinea pigs do not display maturational changes in sleep patterns (Carson, 1998). Down's Syndrome is also accompanied by disturbances in REM sleep. This has been explained by serotonin's involvement in dreaming sleep and the deficit of this neurotransmitter in mental retardation (Mallon, 1989). REM sleep appears to be especially important to neurologically impaired individuals since the brain attempts to develop neural paths during dream sleep to compensate for deficits inhibiting effective learning (Mallon, 1989). Chemical damage to the brain, including alcoholic poisoning, also results in large rebound REM time (Faraday, 1972). Reduced REM time has been identified in Alzheimer's disease patients, reflecting the decline in cholinergic function (Simmons Company, 1998), which regulates neurotransmitter activity while asleep (Wolf, 1994). This may impair consolidation of new information (Mackin, 1997). Long-term potentiation (LTP), a basic mechanism for neuronal memory processing and storage, has been discovered during REM sleep (Wolf, 1994). Hippocampal recordings and REM correlates from sub-primate animals identified theta waves' (6 Hz) central role in memory processing during dreams, and as a facilitator of LTP. Memory is stored when LTP pulses are separated by the period between two theta waves, a time span of approximately 200ms, which are called bytes. This has implicated theta waves in memory processing. During REM, in the absence of novel incoming data, the neo-cortical hippocampus network is paced by theta rhythm (Wolf, 1994) which assists REM sleep reprocessing of novel information gleaned in daily learning (Winson, 1990 in Wolf, 1994). Bursts of theta waves appear in sleeping humans' EEG but not with the consistency or organization demonstrated in sub-primate species (Wolf, 1994). The dense structure of the cortex and the deep location of the hippocampus is thought to impede its recording. Direct measurement from the hippocampus may detect similar theta phenomena in humans (Hobson, 1988 in Wolf, 1994). The marked decline from newborns' daily eight hours of REM to two year olds' three hour dreaming sojourn, is at an age when hippocampal function matures, and REM sleep begins to adopt interpretive, information processing roles (Wolf, 1994). This suggests that the function of REM instigates developmental advances, or evolves according to cognitive demands throughout the lifespan. Whereas non-REM sleep deprivation leads to rapid homeostatic deterioration (Nathan, 1998), long term deprivation of REM – up to two weeks experimentally, and lasting several years, as a side effect of certain anti-depressants – had little overt effect on adult behaviour (Nathan, 1998). However, if the function of REM is to provide opportunities for chemical synthesis connected with memory duplication, REM deprivation would not be expected to impair behaviour for an extended period of time (Faraday, 1972). Dream images connect material in memory especially between recently experienced material, day residue, and old memories, helping to anchor the new material in long term memory (Hartmann, 1996). Material learned during the day and consolidated over a night of sleep is recalled better the next morning (Hennevin, Hars, Maho & Bloch, 1995), with consolidation occurring during sleep dependent on the integrity of REM (Sagi, 1996). It is possible that daily experience is compared with memory and instinctive expectancies for efficient storage (Hobson, 1988). Only the important discrepancies are registered in long term memory, which is thought to be curtailed in the absence of active sleep (Bourhenne, 1997; Mallon, 1989; Simmons Company, 1998). Learning without periods of rest to process information results in only short term storage (BCM, 1996; Rause, 1997). It is not clear whether this is purely a sleep related phenomenon or merely represents the absence of interference (Simmons Company, 1998; Mallon, 1989) during wakefulness by the flood of incoming information. Consolidation of procedural and implicitly learned material is especially impaired by subsequent REM deprivation (Smith, 1995), with declarative learning only mildly affected in normal contexts (Mackin, 1997; Dotto, 1996). Memory required to preform cognitive procedural tasks is affected by loss of REM on the first and third night after skill acquisition (Dotto, 1996). In dreaming, much of the action occurs without articulation, and motor activity is usually disproportionate to sedentary waking life (Wolf, 1994). Since motor skills are refreshed by activity, not rumination, this may indicate that motor program generators, activated by REM sleep, are reviewing the unarticulated sub-narrative instructions of procedural memory. Unprepared learning, more slowly mastered and difficult, is especially dependent on the quality of REM (Greenberg & Pealman, 1974 in LaBerge, 1985). Learning tasks requiring significant concentration or acquisition of unfamiliar skills are followed by increased REM (LaBerge, 1985). Subjects wearing image inversion spectacles experience great increases in the proportion of REM sleep while learning to adapt (Faraday 1972). This phenomenon is not restricted to academic learning, but also applies to the central nervous system learning to process traumatic experiences and emotional adjustments (LaBerge, 1985). Dreaming sleep has a restorative function following anxiety, stress or behavioural reprogramming (Rycroft, 1981). Late in the nineteenth century, it was proposed that sleep fulfills dual functions of eradicating the preceding day's unnecessary memories and of consolidating more useful ones (Rycroft, 1981). Many inputs to the brain, processed in attempts to gain knowledge about the world, are stored as partial memories causing neural connections to overload at synapses. It has been suggested that in REM sleep, dreams are products of neurons feeding back on themselves without stimuli flooding through sensory pathways. As negative feedback loops, they weaken the strength of some neuronal connections. Crick and Mitchinson dubbed the unloading of useless information from the nervous system "reverse learning" in 1983 (Wolf, 1994). They based their erasure theory on the abstract but compelling concept that a system as elaborate as the brain is in danger of dyscontrol via intensification of its oscillations. It is especially vulnerable to parasitic resonance, a condition most likely to affect a system in a changing state during learning periods, development or intense novel experience (Hobson, 1988). REM erases superfluous associations arising from vast amounts of incoming information that require storage in memory (Wolf, 1994). In its detoxifying aspect, the hypothesis is reminiscent of psychodynamic drive-discharge theory. Along with the parasitic oscillations, unwanted memories, especially those of a potentially pathological nature such as obsessions, delusions and hallucinations (Hobson, 1988), would be expelled. If not expunged, unwanted thoughts and erroneous information may be a precursor of obsessive, paranoid pathologies (Nathan, 1998). Reverse learning through discharging dreams refreshes the dreamer by making salient survival memories accessible, in the absence of irrelevant information (Wolf, 1994). Reverse learning allows more compact storage in networks with assurance of little memory overlap. Theoretically this allows for a smaller brain. Practically, amount of REM sleep tends to be negatively correlated with brain size (Mackin, 1997). Humans have a much higher ratio of brain weight to body weight than echidnas and two species of dolphins, anomalies among mammals with their deficit of REM function. It suggests that as an adaptive feature, REM may allow smaller brains in mammals who dream than those who do not (Crick & Mitchison, 1995), since the latter may require a larger neural network to absorb unwanted information (Wolf, 1994). REM sleep has also been addressed in evolutionary terms as an adaptive advantage in novel situations. Although innate instinctual mechanisms exist, specific behaviours are not inborn since the environment is continually changing. Genetically determined dreaming allows rehearsal and refinement of instinctual behaviours without the consequences of overt motor responses (Jouvet, 1980 in LaBerge, 1985; Hobson, 1988). Dreaming sleep is present in species whose nervous systems show increased abilities to assimilate unusual information (Greenberg & Pearlman, 1974 in LaBerge, 1985). The dream state has made increasingly flexible use of information possible (LaBerge, 1985) since REM allows more complex learning to occur (LaBerge, 1985). In species with complex brains, the processes that are adaptive to lower organisms may also be functional, yet supplemented with processes that enhance higher order cognitive roles (Hobson, 1988). The evolutionary perspective of the brain optimizing survival by regulating the organism's transactions with the world and with itself, may be best achieved in the dream state, where the latter can occur with information from external stimuli at its minimum (LaBerge, 1985). Dream function is not restricted to processing previous experiences, but also encompasses fabricating novel ones. This theory views sleep as preparation for the subsequent day's activity, as well as recovery from that of the previous day. This preparatory action of sleep encompasses an anabolic role as well as a catabolic, excretory function (Hobson, 1988). Thus, new ideas, feelings and views of old problems can be expected to arise within dreams. These may be carried forward into the conscious mind or remain as a deeper creative reservoir (Hobson, 1988). REM sleep, as time spent in preparation for learning, is supported by research in which interference of REM sleep left subjects less able to negotiate novel situations (Mallon, 1989). This has been explained by new associations found to be formed during REM (Hennevin, et al., 1995) which are available to process unexpected occurrences (Mallon, 1989). Mnemonic efficiency of neural networks has also been found to increase when the networks periodically enter this altered state of functioning (Blagrove, 1991). Broader connections in dreaming, more generic or combined, rather than specific images, means less inhibitory sharpening or lower signal to noise ratio in the spread of activation (Hartmann, 1996), physiologically representing the psychodynamic concept of condensation. This state, in which creative insight is fostered (ASD, 1990), has been referred to as a "laboratory for experimenting with change" (Rossi, 1972 in LaBerge, 1985), and was the medium for the invention of the sewing machine, the identification of the structure of benzene, Descarte's postulation of Rational Empiricism, the concept of the Elemental Periodic Table, Einstein's relativity theory and Niles Bohr's basic tenants of quantum physical theory (Linn, 1988). Among the Jungian concepts that have been validated by quantum physics (Wolf, 1994), is that dreaming is crucial stimulation for self awareness structures in the mind, which arise through self refection, a process that arises in the dreaming brain in its attempts to integrate, learn, remember and forget all that is necessary for self awareness. Dreams have been likened to atomic phenomena in that they are never independent of the observer (Wolf, 1994). In the dream state, the observer is not localized to one region of the brain, but distributed throughout it, collecting information from several memory locations simultaneously (Wolf, 1994). The quantum wave in the brain is dependent on all of the possible locations of the observer so that memory recall in one location is instantly correlated with other locations, giving rise to surprising and meaningful overlaps of what are usually separate memories (Wolf, 1994). In this role, dreaming may assist learning about how consciousness arises in a quantum mechanical view (Wolf, 1994). Carl Jung believed that wish fulfilment was too restrictive to be the sole psychological reason for engaging in dreams (Wolf,1994). Unlike preceding psychodynamic theorists, he did not view dreams as suppressed unacceptable desires, but necessary for creativity, through production of germinal information for the conscious mind. He believed dream symbols were not simply constructed to conceal information, but were a universal language of archetypes, equations describing new ideas in symbolic terms. He likened them to mathematical equations, ideas represented in symbolic form in waking life (Wolf, 1994). Memory may undergo paradoxical intensification and selective suppression during dreaming. Recall is intensified within the dream as remote characters and events are amalgamated into the dream-scape. Although dreaming minds are hypermnesic with increased access to memory, consolidation of dream material after the termination of the state (Wolf, 1994) is minimal, since most are forgotten unless review occurs upon awakening. This amnesia for a hypermensic state (Hobson, 1988) indicates that memory consolidation differs markedly from waking life (Wolf, 1994). Major symptoms of mental illness are emulated by normal minds during ordinary dreaming. Since dreams may be the product of similar physiological processes that are deranged in mental illness, knowledge of dreaming processes may enhance understanding of mental illness (Hobson, 1988). The scientific journey through the landscape of sleep is still in its infancy. The learning process reveals a glimpse into the world of dreams and the study of dreams provides insight into the requirements for optimal information integration. The frontiers of lucid dreaming, an acquirable skill (LaBerge, 1993), are enthusiastically being charted scientifically. This field promises greater insight into the dreaming brain, opportunities for creative problem solving (LaBerge, 1993), and harnessing of the learning enhancement associated with REM sleep (LaBerge, 1993). The purpose of dreaming includes both development and active maintenance of the functional integrity of the brain (Hobson, 1988) and consciousness. As well as recovery from today, tonight's sojourn form waking activity will include dynamic preparation for the challenges of tomorrow.
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