As adults we spend or should if we don’t one third of our time in sleep and as children up to half of their time. We all sleep when tired and when have a good sleep, we would feel rested. We therefore know that the sleep function is for restoration of physical tiredness or fatigue. But sleep is not just for restoration of physical fatigue, but for the restoration of the mental or brain fatigue as well. We may think that during the sleep, the body is totally shout down and in rest. But surprisingly the body is quite active in sleep and like a factory, does self-restoration or repair during the hours of sleep. In deep sleep, if we can get any, the physical restoration or repair is done and in REM (Rapid Eye Movement) or dream stage of sleep, the mental or brain restoration or repair is done. More importantly, many hormones such as growth hormone in children are secreted in sleep and mostly in deep sleep.
In this paper, the architecture or different stages of sleep will be explored. Then the sleep-wake cycle that is a major component of our circadian rhythm and our body homeostasis and health balance will be exposed. Then the importance of sleep hygiene and lack of it and the disorders of sleep will be discussed. The treatment for sleep disorders and the most common one, insomnia or sleeping pills will not be discussed, as majority are of Benzodiazepine class of drugs, addictive and more habit forming and perpetuating the insomnia. The purpose of this article among the others on this site is more to understand the pathophysiologic process of every disease, so hopefully soon move towards the prevention. Finally what is a very dilemma and question for many, the world of dream and its interpretations will be explained.
Stages of sleep:
During a night sleep of about 8 hours that is normal for adults, the body or brain goes through about 5 cycles, starting with the stage 1 that is the drowsiness or falling asleep stage lasting only a few minutes. Then the second stage that comprises about %45-50 of a normal adult sleep, that is still light and the person could be aroused by sounds and noises and it is the usual toss and turn stage of sleep. The second stage lasts about 40-45 minutes in each cycle that lasts normally 90 minutes. Then the deep sleep kicks in that is comprised of stages 3 & 4 and most adults do not get it much nowadays, while they need to have it at least %20 of their sleep. These stages of 3 & 4 or deep sleep is for the restoration of physical fatigue and if the person does not get it enough, he or she would not feel rested in the morning.
The next stage of sleep in the cycle is REM (Rapid Eye Movement) sleep that is the dream stage of sleep when the individual enters the world of his or her dreams. This stage that comprises about 20-25% of a night sleep is very active not just for the eyes that moves fast as its term suggests, but the whole body physiology such as heart beat, respiration and else are active even more than in the waking state. After the first cycle of sleep and REM, the brain may not start over from stage 1, unless someone’s sleep is very light and broken and keeps waking up in the middle of the night, or after a nightmare. So in a normal restful sleep, after the first cycle and REM, in the second cycle and thereafter, the brain starts from stage 2 and the rest. If the individual’s sleep is light, he or she may not go much or at all through the deep sleep of stages 3 &4 that is very common in the modern era of sleepless nights. Therefore everybody gets mostly stage 2 and REM sleep even if one does not remember having any dreams. REM sleep due to its high brain and physiological activity, has the vital role of restoration of brain fatigue. That’s why people with many mind preoccupation or worries may have lots of dreams and even nightmares. The following figure shows how the body enters the different stages of sleep from a waking state and the repeated sleep cycles throughout a night sleep:
Now in the following each stage of sleep will be discussed in more detail:
Stage 1 & 2 (Light sleep):
The first cycle of sleep in the normal young adult begins with stage 1 sleep, which usually persists for only a few (1 to 7) minutes at the onset of sleep. Sleep is easily discontinued during stage 1 by, for example, softly calling a person’s name, touching the person lightly, quietly closing a door, and so forth. Thus, stage 1 sleep is associated with a low arousal threshold. In addition to its role in the initial wake-to-sleep transition, stage 1 sleep occurs as a transitional stage throughout the night. A common sign of severely disrupted sleep is an increase in the amount and percentage of stage 1 sleep.
Stage 2 of sleep, signaled by the sleep spindles or K-complexes in the EEG as we see in the following figure. In stage 2 sleep, a more intense stimulus is required to produce arousal. The same stimulus that produced arousal from stage 1 sleep often results in an evoked K-complex but no awakening in stage 2 sleep. As stage 2 sleep progresses, high-voltage slow-wave activity gradually appears in the EEG and enters the brain into the stage 3 or deep sleep.
Stage 3 & 4 (Deep sleep):
Stages of 3 & 4 due to their slow wave activities of the brain are also called “slow wave sleep” (SWS). The high-voltage (at least 75 μV) slow-wave (2 cps) activity accounting for more than 20% but less than 50% of the EEG activity. Stage 3 sleep usually lasts only a few minutes in the first cycle and is transitional to stage 4 as more and more high voltageslow-wave activity occurs. Stage 4 sleep identified when the high-voltage slow-wave activity comprises more than 50% of the record—usually lasts approximately 20 to 40 minutes in the first cycle. An incrementally larger stimulus is usually required to produce an arousal from stage 3 or 4 sleep than from stage 1 or 2 sleep.
SWS or deep sleep is the longest in the first third of the sleep, opposite to the dream or REM sleep that is the longest through the last third of the night. Stages 3 & 4 or deep sleep that are for the restoration of physical fatigue correspond or are reactive to this factor, meaning the more tired the body, the longer and deeper is the sleep. That’s why the children’s sleep due to their higher physical activities is deeper and SWS is longer in them. Physically active adults like the athletes and those engaged in regular exercises sleep deeper and have longer stages 3 & 4, thus feel more rested in the morning, compared with those whose minds are busier either with mental activities or with mind preoccupation and worries.
REM or dream stage of sleep, when the person dreams and the brain restores its functions, in the first cycle of the night is usually short-lived (1 to 5 minutes). The arousal threshold in this REM episode is variable, as it is true for REM sleep throughout the night. Theories to explain the variable arousal threshold of REM sleep have suggested that at times, the person’s selective attention to internal stimuli precludes a response or that the arousal stimulus is incorporated into the ongoing dream story rather than producing an awakening.
REM sleep, by contrast to the stages 1-4 or NREM (Non-REM) sleep is defined by EEG activation, muscle atonia, and episodic bursts of rapid eye movements.During the REM periods a remarkable psychophysiological upheaval takes place. The EEG reverts to the fast, irregular, low voltage activity which characterizes very light sleep and there is evidence of a high state of central nervous system arousal: cortical evoked potentials resemble those of the waking state and spontaneous neuronal discharge in both cortical and subcortical structures is increased; there is an increase in both cortical blood flow and brain temperature. Thus the central nervous system is aroused, in some respects to a greater degree than in the waking state. Nevertheless, behaviourally, the subject in a REM period appears to be deeply asleep.
With the notable exception of the extraocular muscles and some fine twitching of small muscle groups there is marked loss of muscle tone, both of muscle potential and the muscle reflexes. There is a high threshold for external sensory stimuli, comparable to that of deep, slow-wave sleep. Peripheral changes are equally remarkable. There is irregularity in all the vital functions with marked fluctuations in pulse rate, respiratory rate, blood pressure and temperature. In the male there are penile erections. Most striking of all, if subjects are awakened during a REM period, in a high percentage of cases they report that they have been dreaming. Mental activity also takes place during NREM sleep but it seems to differ qualitatively from the typical dreams reported after awakening from REM sleep.
REM sleep usually is not divided into stages, although tonic and phasic types of REM sleep are occasionally distinguished for certain research purposes. The distinction of tonic versus phasic is based on short-lived events such as eye movements that tend to occur in clusters separated by episodes of relative quiescence. The most commonly used marker of REM sleep phasic activity in human beings is the bursts of rapid eye movements; muscle twitches and cardiorespiratory irregularities often accompany the REM bursts. The mental activity of human REM sleep is associated with dreaming, based on vivid dream recall reported after approximately 80% of arousals from this state of sleep. Inhibition of spinal motor neurons by brainstem mechanisms mediates suppression of postural motor tonus in REM sleep. A shorthand definition of REM sleep, therefore, is an activated brain in a paralyzed body.
Sleep-wake or circadian cycle or rhythm or the endogenous clock is a internal natural cycle not just in humans but other animals, correlating with the sunset and sunrise. Every animals have a specific centre in their nervous systems to control such cycle or internal clock. In humans, this centre resides a couple of centimetres behind the bridge of the nose, in a pair of nuclei above the crossing of the optic nerves. Each of these ‘suprachiasmatic nuclei’ (SCN) is only about the size of a grain of rice, but their qualities are remarkable. Through their coupling, these cellular clocks activate or silence genes throughout the body at the appropriate times, or to modulate our senses and behaviour. Other than the central nervous system that is the main house of such circadian clock, other tissues as different as heart, muscle or lung also hold a similar set of ‘clock genes’ for undergoing oscillatory changes to the demand of these tissues. The SCN ‘pacemaker’ and these organ clocks have different qualities, however, forming a hierarchy within the circadian system. The same genes whose expression levels reach a maximum in the early morning in the SCN do so several hours later in the periphery.
The suprachiasmatic nucleus of the hypothalamus functions as the master pacemaker to initiate daily synchronization according to the photoperiod, in turn determines the phase of peripheral cellular clocks through a variety of signaling relays, including endocrine rhythms and metabolic cycles. Moreover the circadian rhythm is in synchrony with longevity, as upon aging, there is a de-synchrony in the circadian cycle or rhythm. This occurs at the expense of peripheral metabolic pathologies and central neurodegenerative disorders with sleep symptoms, and genetic ablation of circadian genes in model organisms resembled the aging-related features. Notably, a number of studies have linked longevity nutrient sensing pathways in modulating circadian clocks. Therapeutic strategies that bridge the nutrient sensing pathways and circadian clock might be rational designs to defy aging.
The familiar ‘jetlag’ experiment in human long flight passengers, that also exists similarly in shift of day-night changes, have also been observed in lab animals, causing the shift of the cycle by several hours by different speeds and in different organs. While the SCN in the brain adjusts within one cycle, the liver is one of the body organs that can take more than six days to synchronise with the new light-dark cycle. To show that the scenario is more complicated, genetic studies have shown that numerous genes, beyond the known clock genes, are circadianly regulated in different organs and tissues. These so-called clock-controlled genes represent the output pathway of the circadian system. They facilitate the daily modulation of many physiological properties, such as blood pressure (lowest just after midnight), mental performance (best in the mid-afternoon), or hormones (cortisol is highest in the morning, melatonin at night).
To make the situation more alarming, the disruption of a clock gene in the mouse has been found recently to be associated with increased risk of irradiation-induced tumorigenesis, perhaps as a result of loss of normal circadian controls of genes concerned with regulation of cell proliferation and the cell cycle. Thus, underlying circadian behaviour is a molecular machinery that is present in practically all body cells, and the daily temporal structure of behaviour appears to be the product of a hierarchical amalgam of brain and peripheral clocks. Therefore the disruption of sleep-cycle that is ignored nowadays by many people could lead to many complications and disorders not just feeling tired and sleepy and affecting our mood and brain, but the whole organism and every single tissue and triggering many disorders from autoimmune disorders to cancer.
Sleep is also important for regulating many physiologic functions that relate to metabolism and immune system. This relationship is bidirectional as any of these diseases cause the disruption of sleep and sleep disorders, while any poor sleep hygiene and lack of sleep and disturbance in the sleep-wake cycle could perpetuate any of these metabolic or autoimmune disorders. For example there is substantial evidence to suggest that sleep habits and sleep disorders are related to diabetes risk. In specific, insufficient sleep duration and/or sleep restriction in the laboratory, poor sleep quality, and sleep disorders such as insomnia and sleep apnea have all been associated with diabetes risk. Both physiologic mechanisms such as insulin resistance, decreased leptin, and increased ghrelin and inflammation and behavioral mechanisms such as increased food intake, impaired decision-making, and increased likelihood of other behavioral risk factors such as smoking, sedentary behavior, and alcohol use predispose to both diabetes and obesity, which itself is an important diabetes risk factor.
The synchronization of a circadian system is an active process called ‘entrainment’, with light being the predominant controller or “zeitgeber”. It is the regular alternation between night and day that has shaped the evolution of the circadian clock. In mammals, unlike in other animals, light reaches the circadian system exclusively through the eyes. The are several responsible light receptors, such as pupillary constriction, melatonin suppression and adaptation of the primary visual system, and the most recently discovered contributor, “melanopsin”, and probably more of similar other photopigments still to be discovered.
A normal sleep habit or pattern or a normal sleep-wake cycle or circadian rhythm could promote the process of neurogenesis that occurs throughout life in the subgranular zone (SGZ) of the hippocampal dentate gyrus of several mammals, including humans. Conversely any sleep disturbances or poor sleep hygiene or abnormal circadian rhythm would affect the hippocampal neurogenesis and its other functions, including learning, memory, and could cause depression. In the relationship between potentiation of neurogenesis and sleep, some sleep stages such as REM with its theta oscillations in REM sleep, and the high frequency sharp wave ripples in NREM sleep which involve 10 to 18% of hippocampal neurons are crucial.
Many hormones of the body such as growth hormone, cortisol and prolactin or the milking hormone, are under sleep regulation. For example the growth hormone secrets more in the SWS or deep sleep that children have more than adults for their growth. Therefore poor sleep or lack of sufficient deep sleep of stages 3 & 4 in children would affect their growth. The secretion of growth hormone during SWS sleep has a pulsation rhythm every two hours, associating with the deep sleep cycle. The secretion of the growth hormone has been measured to be low in SWS deprivation but not in REM sleep deprivation. The same is almost true about the secretion of cortisol from anterior pituitary gland that is more suppressed in the deep sleep as a protective or reconstructive measure of the organism against stress and diseases. Therefore poor or lack of sufficient SWS sleep would lead to mood and other metabolic or autoimmune disorders. While the growth hormone and cortisol secretion are also affected by the circadian rhythm and in the case of cortisol more so, the secretion of prolactin in the breast feeding mother is more co-related with sleep and more so with the REM stage than with the circadian rhythm.
One of the most common complaint or symptom in the medicine, is insomnia or lack or poor sleep. Insomnia is generally divided into not sleeping at all, difficulty falling asleep, maintaining sleep, and waking up too early. While lack of total sleep is very rare, most people complaining of insomnia, have difficulty falling asleep and maintaining their sleep, having a light and interrupted sleep, tossing and turning at night, even in some to the point of waking up, then falling back to sleep. Another type of insomnia is waking up too early in the morning or having a short sleep. In addition to the above three common types of insomnia, there are also sleep disturbances that could cause either waking up the person, or causing a non-restful sleep in the morning. The most common type of these sleep disturbances is having nightmares that my wake up the individual. While the nightmares like dreams occur in the REM stage of sleep, some young children may have “night-terrors” that happens in the SWS or deep sleep, wakes up the child in terror with scream and cry, being hard to calm him or her down and put back to sleep, and in the morning there will be no recollection of the incident in the child.
Another type of sleep disturbance that is not even considered as such by many, is having too many dreams, specially vivid dreams, as this may affect the resting quality of the sleep and the subject not feeling rested well in the morning. Moreover these vivid dreams like nightmares may affect the individual’s state of mind in the waking hours, causing some stress, anxiety or mind preoccupation. Restless legs is another type of sleep disturbance that could affect the resting quality of sleep, so sleep talking, bruxism or teeth grinding in sleep and more so sleep apnea. Sleep apnea that is poor oxygenation of the brain during sleep, could be caused by peripheral obstruction of the upper air pathway or respiratory tract, such as nasal polyps or some obstructions in the throat of pharynx such as large tonsils, that could be treated easily by surgical removal of the obstruction cause.
Obesity could be a cause of sleep apnea again by impinging on the peripheral air pathway that could be treated by lowering weight. Sleep position such as sleeping on abdomen or belly, specially in the above group who already have some obstructive air passage, could also cause sleep apnea and poor or low oxygenation of the brain during sleep. The sleep position, obstructing the peripheral air pathway could be treated by changing the sleep position. Most of the peripheral causes of sleep apnea could be identified by the sign of snoring of the individual. Sleep apnea could be also “central” or poor or low oxygenation of the brain during sleep that could have organic brain causes or simply being the effect of alcohol or drug ingestions. This could be treated by identifying and removing the organic cause.
Insomnia that generally affect the resting quality of sleep and its important functions for restoration and recuperation of the organism, mostly lower the amount of SWS or deep sleep. The quality of the sleep of an insomniac reaches almost the quality of aging people who have less deep sleep, and also complain of different types of insomnia. Although an aging brain may not need much of functional restoration of the body during sleep, so having less SWS sleep, an insomniac person who is not yet in that stage of life and needs normal quality of sleep for restoration and recuperation of the organism, would be seriously affected.
Opposite to insomnia or low amount of sleep, is hypersomnia or high amount of sleep or sleeping too much and for long hours. This often denotes to long hours of sleep at night, but some may be sleeping during the day in addition to long sleep at night as well. This could be differentiated from people who against their will fall asleep at anytime in the day, that’s another sleep disorder called “Narcolepsy” or sleep paralysis that will be discussed later. This also should be differentiated from children who need to sleep longer as a requirement of their organism for more restoration and also growth of the body and its organs.
Hypersomniac people may not even complain or present to the medical attention, but may consider themselves lucky to sleep long and well, and be in fact the subject of jealousy of others. Sleeping an hour or two above the normal amount of 8 hours sleep for adults, while could be a normal variation, as some people normally are long-sleepers, as some people could be normally short-sleepers for an hour or two. But hypersomnia, even in some an hour or two is a sleep disorder and pathology with underlying causes in need of treatment.
The most common cause of hypersomnia is atypical depression due to low dopaminergic activity of the brain to keep the body in the full arousal state. These subjects also may have overeating, feeling of fatigue and slow physical and mental levels of activities. The extreme rare examples of organic hypersomnias are diseases of the brain such as “encephalitis lethargica”, “Pickwickian syndrome”, “Kleine-Levin syndrome” and the somnolence associated with advanced hepatic, renal and other metabolic diseases.
The Narcolepsy syndrome is a dramatic tetrad of symptoms including one or all of the following: (a) Narcolepsy, or periods of extreme sleepiness which may occur at any time during the day; (b) Cataplexy, or attacks of sudden loss of muscle tone which may occur without warning, often following strong emotion such as anger or mirth, and in which the patient slumps or falls to the ground; (c) Sleep paralysis, the often terrifying experience of awakening from sleep and, though conscious, being unable to move a muscle; (d) Vivid hallucinations during the moments before falling asleep or after awakening.
These patients were formerly thought to be suffering from occult epilepsy,a form of hyperthyroidism, or hysterical states, while in fact they suffer disturbances of the neural mechanisms which regulate sleep. Whereas normal persons have some 60 to 90 minutes of NREM sleep before their first REM period, most patients who have narcolepsy, with cataplexy and/or sleep paralysis, go into REM sleep almost immediately at sleep onset. The polysomnographic studies of these individuals have shown their narcoleptic attacks of loss of muscle tone, the sleep paralysis and the hallucinations are manifestations of REM sleep occurring abnormally during “waking” hours.
Somnambulism, or sleep walking is the most dramatic of sleep disturbances, having made many unreal stories and film subjects. This condition is mostly occur in childhood and during the deep or SWS sleep and is simply of the child walks out of his or her bedroom, mostly going to the parents’ bedroom and sleeps there with no recollection of the event in the morning after. Contrary to the lay perception and exaggerated presentation of sleep walking, the subjects do not execute any risky or dangerous acts, and in fact in majority of the situations, the eyes are open and the individual sees where he or she is going, but would not have any recollection in the morning after as it had happened during stages 3 & 4 of deep sleep.
Bed wetting or “Nocturnal enuresis” like sleep walking is a sleep disorder of young children up to the age of 3 or 4 years. A higher incidence occurs in boys, and perhaps in some emotionally disturbed children. Several investigations involving all-night EEG and other physiological studies, have demonstrated that enuresis takes place during sudden arousal from deep slow-wave sleep to wakefulness or to a lighter stage of sleep.
Restless Legs and Limb Movements:
The restless legs/limbs syndrome (RLS) is a common, today still under-diagnosed, sensorimotor disorder. The disease can appear in childhood, its course is usually chronic with rare periods of remission. The severity of symptoms varies largely but usually enhances with age. This syndrome that’s called as such due to its significant variation in manifestation, could include movement, kicking the legs or even arms, muscle spams or twitches that could be painful in some and waking up the individual. The disorder is chronic and associated with multiple comorbidities, such as insomnia, psychiatric mostly mood disorders, and occasionally with daytime excessive sleepiness and fatigue. Primary and secondary forms could be associated with iron deficiency, pregnancy, uremia, spinal cord diseases, parkinsonian disorders, and spinal-cerebral atrophies.
Sleep hygiene or how to promote a more normal and restful sleep is largely unknown and even not much recommended by physicians who mostly prescribe hypnotics or sedatives, or sleeping pills that many are narcotic or addictive and make the sleep disorder or mostly insomnia chronic. Sleep disorders and on the top, insomnia is mostly not only a disease on its own but a symptom manifestation of another disorder such as mood disorders. Therefore to treat the sleep disorder, the underlying pathology needs to be treated first. The following is a list of some recommendations on sleep hygiene for improvement of the sleep quality that could be used by anyone with sleep disorders secondary to primary condition or people with habitual insomnia due to bad sleep-wake cycle habits:
- Avoid offensive causes:These could include any caffeine or other stimulant containing beverages and food such as coffee, tea, soft drinks. Alcohol while may lead to fast falling asleep and maintaining sleep for a few hours, it usually causes early arousal and needs to be avoided specially heavy and regular drinking. Any other substances such as narcotic like marijuana or weed while they lead to early and fast sleep, they could cause early hours awakening. Smoking also is a common cause of insomnia and other sleep disturbances as an addicted brain to nicotine, would wake up due to the withdrawal and it is not uncommon to observe the heavy smokers wake up in the middle of the night to smoke.
- Exercise:To have a restful and more deep sleep, regular exercise is vital, but late hours of exercise in the evening right before or close to sleep time could cause reversal of benefit.
- Sleep Timing Regularity:This could be the most important aspect of the sleep hygiene that is missed or ignored by majority of people who suffer from insomnia and perhaps other sleep disorders. The regularity of sleep timing and other sleep habits is closely associated with other physiological regularity of the organism and the circadian rhythm, all leading to a normal homeostasis. Going to bed and sleep relatively early and at the same time every night, allowing an 8 hours sleep is crucial for a healthy and restful sleep. Even if the individual has nothing to do to wake up in the morning, sleeping too late and wake up too late, or sleeping in the daytime, out of the circadian rhythm is breaking the sleep-wake cycle and could have irreparable consequences on the general well being of the person.
- Stay in bed:It is common that people with insomnia or other sleep disturbances, causing the interruption of their sleep and wake up, engage in other activities such as playing with their phones or other digital gadgets, or get out of bed drinking, eating or watching TV, then expect to be able to go back to sleep. Any such interruption could cause more insomnia and harder to return to sleep. Therefore if the sleep gets interrupted for whatever reason, the best would be to remain in bed until sleep resumes its line. In contrary to many beliefs, even tossing and turning is considered rest and sleep, and should not prompt one to get out of bed or totally wake up and enroll in other activities. We should remember that most of, up to half or more , of an adult sleep nowadays is comprised of stage 2 sleep that is light and consists of toss and turn.
- No distractions in the bedroom:People with insomnia and other sleep disorders may have many distractions in their bedroom such as TV, radio, audio-players, cell phones, computers and other digital gadgets that are the distracters for a sound and peaceful sleep that need to be totally avoided.
- Noise and other stimuli:Noise and other stimuli could disturb the sleep that one needs to control and avoid, though sometimes these external factors are incontrollable.
- Right eating and drinking habits:Eating heavy and drinking any liquid close to the bedtime would interrupt the sleep, that should be avoided for a continuous and restful sleep. Some foods such as dairy products could be sleep promoters.
The World of Dreams:
We have a long way since the publication of “The interpretation of Dreams” by Sigmund Freud at the turn of past century in 1900. The interpretation of dreams have puzzled humans from the time of antiquity and has caused numerous real events afterwards based on such interpretations and predictions, when done in the royal courts. Freud strived to make all the psychic and non-scientific interpretations of dreams, scientific and subjects of delicate studies. But he originally a neurologist could not explain the inner world of human’s psyche with neuroscience as it is a common practice now, and fell in psychological interpretation of all, including the interpretation of dreams that he recognized it as a window to our unconscious. Freud understooddreams as wish-fulfillments and distinguished between the manifest content of a dream (what the dreamer remembers) and the latent content, the symbolic meaning of the dream (i.e., the underlying wish).
Through the processes of condensation, displacement, and secondary elaboration (dreamwork) the dreams are formed and interpreted according to Freud. The process of condensation is the joining of two or more ideas/images into one. Displacement takes place when a person or object displaced or distorted to something else in the dream. This process is for the protection of the conscious mind or ego in case of bad dreams, e.g. hating or hurting someone, so the dreamer not to feel guilty upon awakening. Secondary elaboration occurs when the unconscious mind strings together wish-fulfilling images in a logical order of events, further obscuring the latent content. According to Freud, this is why the manifest content of dreams can be in the form of believable events. Later on Freud expanded his dream theory to include symbols of different natures particularly sexual to fit his ego-id-superego principal theory.
But Freud predicted that “Deeper research will one day trace the path further and discover an organic basis for the mental event.” The initial discovery of REM stage of sleep principally correlating with dreaming and more recently that NREM stages of sleep as well produce dreams, and going beyond the stages of sleep and probe into all the anatomical regions of the brain during sleep, bridging between the phenomenology of dreams and the underlying neuronal activity of the brain have partially fulfilled the Freud’s dream.
Similarities between dreaming and waking
There is a striking similarities between the dreaming and waking state in the activity of most domain of the body, from the senses to emotions, cognition and motoric system. That is why the dreams are felt so real and vivid, and if not nightmares, the individual would like to have them again as opposed in the real life, he has no control of switching them on and off, but can enjoy them without affecting his or her real daily life. So while in dream can have almost a real life experience, he has no voluntary control over its start and finish and limit in motoric activities, like cannot run well, but may be able to fly.
The similarities between waking consciousness and dreaming consciousness, relate to changes in brain activity and organization between the two states of mind or brain functions. At least superficially, the EEG looks similar in active waking and REM sleep. Positron emission tomography (PET) studies have shown that global brain metabolism is comparable between wakefulness and REM sleep. Such studies have also revealed a strong activation of high-order occipito-temporal visual cortex in REM sleep, consistent with the vivid visual imagery during dreams. There is also consistency between a subject’s cognitive and neural organization in dreaming and waking. For instance, studies of children demonstrate that dream features show a gradual development that parallels their cognitive development when awake. Patients with brain lesions that impair their waking cognition show corresponding deficits in dreams. For example, subjects with impaired face perception also do not dream of faces.
Brain lesion studies have enabled scientists to locate the corresponding neuroanatomical substrates of dreaming. Through these studies, forebrain regions rather than brainstem have been more REM sleep generators. In most cases, global cessation of dreaming follows damage in or near the temporoparieto-occipital junction (around Brodmann’s Area 40), more often unilaterally than bilaterally. This region supports various cognitive processes that are essential for mental imagery. Less frequently, global cessation of dreaming follows bilateral lesions of white matter tracts surrounding the frontal horns of the lateral ventricles, underlying ventromedial prefrontal cortex.
The initial equation of a physiological state (REM sleep) with a mental state (dreaming) was incorrect, or at best, an oversimplification. Moreover, neuropsychological evidence indicates that dreaming and REM sleep can be dissociated: forebrain lesions can abolish dreaming and spare REM sleep, whereas brainstem lesions can almost eliminate overt features of REM sleep without abolishing dreams.
Therefore we need to move beyond the REM–NREM sleep dichotomy and beyond traditional sleep staging. Although staging is useful, it treats brain activity as uniform in space, while increasing evidence suggests that different brain regions are in different states at the same time. For example, preliminary findings suggest that during sleep walking, thalamo-cingulate pathways are as active as when in wake, whereas the rest of the cerebral cortex is in NREM sleep. Also the study of REM sleep behavior disorder suggests that, contrary to common assumptions, wakefulness,
REM sleep and NREM sleep are not be mutually exclusive states. PET and magneto-Encephalography (MEG) suggest that medial prefrontal cortex, a part of the default network, is highly active in REM sleep,as it is during wakeful rest. Conversely, other components of the default network, including the posterior cingulate and inferior parietal cortices, are eactivated in REM sleep, as in highly engaging waking tasks. Finally the neuromodulatory milieu changes drastically in sleep, specifically,the levels of norepinephrine, serotonin, histamine and hypocretin are reduced in REM sleep compared to wake, so the presence of one or more of these neuromodulators might be necessary for external stimuli to be incorporated into one’s stream of consciousness.
Scientific research on dream has recently gone beyond the generic study of the REM and NREM sleep, but progress in signal decoding might enable researchers to investigate the neural correlates not only of dream form (what is common to all dreams) but also of dream content (what is specific to a particular dream). This can be done, for instance, by using classification techniques applied to fMRI or hd-EEG data. At least initially, it might be worthwhile considering some coarse properties of individual dreams, such as the frequency of occurrence of faces or places in a dream report, the amount of movement, or the dominant affective valence. In principle, it should be possible to predict not only the likelihood of a report upon awakening, but also the likelihood of specific features based on preceding brain activity. An important step would be to identify the contents of internally generated mental imagery using the same approach. Furthermore, some patients with epilepsy or post-traumatic stress disorder who experience recurring dream contents could provide a unique opportunity to relate specific dream content to its neural basis.
Sleep that is a basic necessity of life in any being, has been abused by the humans in the modern era by our arbitrary life settings. Above all our sleep-wake cycle, a major part of the circadian rhythm has been totally derailed. This has not only caused insomnia and all types of sleep disorders, but due to the important role of circadian rhythm or clock in every living cell of our body, we are inflicted by many new diseases such as cancers and autoimmune disorders. Our scientists desperately searching for the causes and cures of these diseases, but have forgotten the answer could be simple and in the disturbances that we ourselves have inflicted upon our living system, in addition to the microbial invasion from the environment befalling on us.
The righteous epigenetic model of pathophysiologic explanation of all our diseases explain well that the environmental casualties win our being that is protective by nature, in the battle of survival, only when our being is vulnerable and derailed off the normal pathway. And sadly and ironically this we do to ourselves, by for example not sleeping well and not following our natural sleep-wake cycle or circadian rhythm. The sleep-wake cycle or circadian rhythm have been emphasized here as only sleeping enough hours or as some do, sleeping in the daytime, is not along the path of maintaining this normal cycle and rhythm. But this cycle and rhythm follows the other cycles in the nature, such as the night and day cycle, as melatonin secrets by the pineal gland of the brain at night to regulate this cycle and rhythm. Hope this paper will open some eyes and minds to get back to the nature of things, like simply following a normal and healthy sleep and waking pattern, along keeping the physics of the body and the brain active.
Dr. Mostafa Showraki, MD, FRCPC
Lecturer, School of Medicine, University of Toronto
Author: ADHD:Revisited Book
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