SLEEP
Sleep normal, regular state of rest of an organism. In contrast to the waking state, sleep is characterised by relative quiescence of physiological functions (blood pressure, breathing, and heartbeat) and a relatively low response to external stimuli.
Typical Sleep Cycle
Sleep has long been treated as a behavioural state. Nonetheless, some characteristics of brain physiology such as brain-wave patterns—as recorded by electroencephalography or EEG—are now accepted as part of its definition because of their unvarying association with sleep behaviour.
Stages of Sleep
The brain waves of a person go through certain constant changes, classified as stages 1 to 4, in the course of the sleep cycle. The EEG of a person in the waking state is characterised by alpha waves (8 to 12 cycles/sec) and low-voltage activity of mixed frequency, whereas sleep onset involves a disappearance of this alpha activity. Stage 1, considered the lightest stage of sleep, is characterised by low-voltage, desynchronised activity and sometimes by low-voltage, regular activity at 4 to 6 cycles/sec as well. After a few seconds or minutes, this gives way to stage 2, a pattern showing frequent spindle-shaped tracings on the EEG, called sleep spindles, at 13 to 15 cycles/sec, and certain high-voltage spikes known as K-complexes. Soon thereafter, stage 3 begins with the appearance of delta waves (high-voltage activity at 0.5 to 2.5 cycles/sec). Eventually, in stage 4, these delta waves occupy the major part of the record.
Dreaming Sleep
The categorisation of sleep records into these four stages is a somewhat arbitrary division of a continuous process. More important, sleep exhibits four or five periods of so-called emergence from stages, 2, 3, and 4 to a stage similar to stage 1. Persons awakened during these periods of emergence frequently—60 to 90 percent of the time—report that they have been dreaming. Such periods are characterised not only by stage-1 EEG patterns and by rapid conjugate (coupled) eye movements but also by many other distinguishing factors. Among these are a great irregularity in pulse rate, respiratory rate, and blood pressure; the presence of full or partial penile erections in the male; and generalised low muscular tone interrupted by movements in small muscle groups.
Periods of emergence thus differ markedly from typical stage-1 sleep as well as from the other three stages. Because of these distinguishing characteristics and because of their specific neurophysiological and chemical character (see below), these periods are now almost universally seen as constituting a separate state of sleep. Similar sleep periods are found in nearly all mammals and birds studied. These periods are referred to as D- (desynchronised or dreaming) sleep; the remainder of sleep is called S- (synchronised) sleep. These two states are also known, respectively, as REM (rapid-eye-movement) sleep and NREM (non-rapid-eye-movement) sleep; as paradoxical sleep and orthodox sleep; or as active sleep and quiet sleep.
Anomalies
The individual EEG changes characteristic of sleep may sometimes be deceptive. The deep, slow waves usually associated with sleep, for instance, can be found in the waking state under certain pharmacological conditions and are also seen during certain phases of anaesthesia or coma. Thus, when an EEG tracing is used to make a diagnosis of sleep, the regular cyclic pattern described above and the regular alternation of the two states are the most important phenomena, rather than any single characteristic wave form.
Time Allotments
Several characteristics of a typical night's sleep are found regularly and universally. First, the four or five periods of D-sleep that occur during the night take up a total time of about 90 minutes, a little more than 20 percent of total sleep time. Second, the first D-sleep period occurs about 70 to 120 minutes after the onset of sleep. This interval may be longer in some normal subjects, but it is significantly shorter only in a few abnormal clinical and experimental conditions such as narcolepsy; and the pattern occurs whether or not the person recalls any dreams.
Some time variations occur with age, however. The young always have more sleep time, and considerably more D-sleep time, than do adults, as in any mammalian species. The new-born child sleeps 16 to 18 hours; at least half of which is D-sleep. The young adult human spends 16 to 17 hours awake and 7 to 8 hours asleep, of which perhaps 6 hours are spent in S-sleep and 1.5 hours in D-sleep. Both S- and D-sleep, on the average, decrease slightly with increasing age. The same relationship appears to hold for other mammalian species.
Sleep in Other Species
As for other animals, most vertebrates may be said to display at least a primitive form of sleep, according to the above behavioural definition. Fish and amphibians have periods of quiescence accompanied by decreased response to environmental stimuli. Concomitant EEG or other recordings, however, have not demonstrated clear-cut sleep-versus-waking differences. Reptiles demonstrate sleep behaviour, and recordings show results somewhat similar to mammalian S-sleep; in a few instances, brief episodes of a state very much resembling D-sleep have been recorded as well. Birds have definite periods of both S- and D-sleep, although the D-periods are generally very short and account for a small percentage of total sleep time. All mammals have clear S- and D-sleep, with the possible exception of a single very primitive mammal, the spiny anteater.
Physiology and Chemistry of Sleep
A tremendous amount of knowledge has been accumulated about the central and peripheral mechanisms controlling and involving sleep. Basically, certain areas in the brain stem—the most primitive part of the brain and the part that controls such basic functions as breathing and heart rate—are involved in the control of the two sleep states. Considerable controversy still exists as to exactly which brain-stem regions are involved and how they interact, but it is known that several brain chemicals called biogenic amines—dopamine, norepinephrine, and serotonin—act as neurotransmitters and neuromodulators in regulating discharge of brain cells. The evidence is clearest for the involvement of serotonin. Serotonin is necessary for normal sleep to occur, although it is only one of many elements and is not sufficient in itself. The roles that norepinephrine and dopamine have in sleep are less certain.
Recent research demonstrates that the human nervous system controls the body's functions differently during the sleep states than during waking. The details are complex, but breathing mechanisms, temperature mechanisms, and musculature all function differently during sleep. Especially dramatic are the changes during D-sleep, in which core-body temperature is hardly controlled at all, so that mammals, including humans, become poikilothermic (cold-blooded). Differences in control mechanisms are becoming important in helping to characterise and understand a whole series of sleep-related diseases; for instance, in sleep apnea, breathing repeatedly stops or becomes very shallow during sleep.
Functions of Sleep and Sleep Requirements
Probably the most important and difficult question is that of the functions of sleep. This question has not been completely answered, and differences of opinion exist. Some scientists believe that sleep has no biological function and is simply a sort of habit. The predominance of evidence, however, suggests a biological function for sleep—in fact, most probably two functions, related to the two states of sleep. S-sleep tends to increase after exercise, after starvation, and at other times of increased metabolic need. Thus, S-sleep probably plays a role in the restoration of the body and brain, perhaps facilitating the synthesis of large molecules such as proteins and ribonucleic acids. D-sleep may play a more complex role in providing restoration for brain processes—especially some higher-level brain processes involved in focusing attention, waking ego mechanisms, performing subtle cognitive and social tasks, and so on.
The numerous investigations leading to these conclusions include studies of total sleep deprivation and of differential deprivation of different sorts of sleep, as well as studies of persons who always sleep 9 or more hours (long sleepers) and those who always sleep less than 6 hours (short sleepers). As the latter point indicates, a tremendous variation occurs in sleep requirements. Some persons function well on five hours of sleep a night, whereas others require ten hours; yet they are all physically and mentally normal. A person functioning with no sleep or almost none is occasionally heard of, but such reports have not been substantiated; apparently some sleep, at least four or five hours, is needed by everyone.
Sleep Disorders
A new field of clinical medicine is developing, related to psychiatry and neurology but not identical to either one. Called sleep medicine, it deals with sleep disorders, of which many kinds can be identified. Sleep problems are usually divided into three kinds: the insomnia’s, a group of problems producing difficulty in falling asleep or difficulty in staying asleep; hypersomnolence, characterised by too much sleep, or sleepiness when a person does not want to sleep; and episodic nocturnal events, consisting of disorders such as night terrors, nightmares, and sleepwalking .
Insomnia and hypersomnolence are only symptoms and may have many different causes. For example, insomnia can be caused by such conditions as painful arthritis; by endocrine disturbances; by the use of certain chemical substances or by the withdrawal from others (including alcohol); by psychological problems, such as anxiety and depression; and by disturbances in biorhythm such as jet lag. In terms of treatment, therefore, insomnia is not an illness that can be cured by a sleeping pill. Rather, the physician must determine and treat the insomnia's underlying cause.
Dreaming, form of mental activity, different from waking thought, which occurs during sleep. The nature of dream activity has been characterised by many clinical and laboratory studies. These studies show that dreams are more perceptual than conceptual: Things are seen and heard rather than being subjected to thought. In terms of the senses, visual experience is present in almost all dreams; auditory experience in 40 to 50 percent; and touch, taste, smell, and pain in a relatively small percentage. A considerable amount of emotion is commonly present—usually a single, stark emotion such as fear, anger, or joy rather than the modulated emotions that occur in the waking state. Most dreams are in the form of interrupted stories, made up partly of memories, with frequent shifts of scene.
This broad characterisation includes a great variety of dream experiences. Many dreams collected in sleep laboratories are rather ordinary, but most people have at least some bizarre dreams. At the start of the 20th century, Sigmund Freud proposed that a mental process quite different from that used in the waking state dominates the dreaming mind. He described this “primary process” as characterised by more primitive mechanisms, by rapid shifts in energy and emotions, and by a good deal of sexual and aggressive content derived from childhood.
Biology of Dreaming
Research in recent years has clarified many of these aspects of dreaming, but what may be of greatest significance has been the discovery of biology of dreaming. Starting with the work of the American sleep researchers Eugene Aserinsky and Nathaniel Kleitman in 1953, studies have shown that a dream does not consist of fleeting imagery that occurs while a person awakens from sleep, but instead that it takes place during a biological state of its own.
Thus, two clearly distinguishable states of sleep exist. The first state, called S-synchronised sleep, or NREM-sleep (non-rapid-eye-movement sleep), occupies most of the sleep period and is associated with a relatively low pulse and blood pressure, little activation of the autonomic nervous system, and few or no reports of dreaming. The second type of sleep, known as D-sleep (dreaming, or desynchronised, sleep), or REM-sleep (rapid-eye-movement sleep), occurs cyclically during the sleep period and is characterised by activation of the autonomic nervous system, rapid eye movements, and frequent dream reports. Typically, a person has four or five periods of D-sleep during the night, whether the dreams are remembered often, rarely, or not at all; they occur at intervals of about 90 minutes and altogether constitute about 25 percent of the night's sleep (as much as 50 percent in a new-born child). Evidence indicates that a dream period usually lasts from 5 to 20 minutes.
Such stimuli as sounds and touches impinging on a dreamer can be incorporated into a dream if they occur during a D-period. These stimuli, however, do not initiate a D-period if one is not already in progress, so that, at least in such cases, dreams do not “protect” sleep in the way that Freud suggested. Although mental activity may be reported during NREM-sleep, these are usually short, fragmented, thought like experiences.
Other Animals
As to whether other animals dream, a definite statement can be made for mammals, at least, that they do have D-sleep periods; and reasons exist for thinking that dreams occur during these periods. For example, other mammals as well as humans show intense activation of the visual cortex during D-sleep, and in humans this corresponds to the experiencing of visual sensations. One study further demonstrated that monkeys that had been trained to push a lever whenever they saw pictures on a screen in front of them as they awoke in a dark room suddenly began to push the lever a number of times during their sleep periods.
Dream Content
This new knowledge of the biology of dreaming does not suggest that dreams have no meaning. Dreams are meaningful mental products, just as thoughts and daydreams are. They express important wishes, fears, concerns, and worries of the dreamer; so undoubtedly the study and analysis of dreams can sometimes be a useful procedure, revealing different aspects of a person's mental functioning.
Consciousness, States of, no simple, agreed-upon definition of consciousness exists. Attempted definitions tend to be tautological (for example, consciousness defined as awareness) or merely descriptive (for example, consciousness described as sensations, thoughts, or feelings). Despite this problem of definition, the subject of consciousness has had a remarkable history. At one time the primary subject matter of psychology, consciousness as an area of study suffered an almost total demise, later re-emerging to become a topic of current interest.
Historical Background
Most of the philosophical discussions of consciousness arose from the mind-body issues posed by the French philosopher and mathematician René Descartes in the 17th century. Descartes asked: Is the mind, or consciousness, independent of matter? Is consciousness extended (physical) or unextended (non-physical)? Is consciousness determinative, or is it determined? English philosophers such as John Locke equated consciousness with physical sensations and the information they provide, whereas European philosophers such as Gottfried Wilhelm Leibniz and Immanuel Kant gave a more central and active role to consciousness.
The philosopher who most directly influenced subsequent exploration of the subject of consciousness was the 19th-century German educator Johann Friedrich Herbart, who wrote that ideas had quality and intensity and that they may inhibit or facilitate one another. Thus, ideas may pass from “states of reality” (consciousness) to “states of tendency” (unconsciousness), with the dividing line between the two states being described as the threshold of consciousness. This formulation of Herbart clearly presages the development, by the German psychologist and physiologist Gustav Theodor Fechner, of the psychophysical measurement of sensation thresholds, and the later development by Sigmund Freud of the concept of the unconscious.
Foundations of Modern Research
The experimental analysis of consciousness dates from 1876, when the German psychologist Wilhelm Max Wundt started his research laboratory. For Wundt, the task of psychology was the study of the structure of consciousness, which extended well beyond sensations and included feelings, images, memory, attention, duration, and movement. Because early interest focused on the content and dynamics of consciousness, it is not surprising that the central methodology of such studies was introspection; that is, subjects reported on the mental contents of their own consciousness. This introspective approach was developed most fully by the American psychologist Edward Bradford Titchener at Cornell University. Setting his task as that of describing the structure of the mind, Titchener attempted to detail, from introspective self-reports, the dimensions of the elements of consciousness. For example, taste was “dimensionalised” into four basic categories: sweet, sour, salt, and bitter. This approach was known as structuralism.
By the 1920s, however, a remarkable revolution had occurred in psychology that was to essentially remove considerations of consciousness from psychological research for some 50 years: Behaviourism captured the field of psychology. The main initiator of this movement was the American psychologist John Broadus Watson. In a 1913 article, Watson stated, “I believe that we can write a psychology and never use the terms consciousness, mental states, mind . . . imagery and the like.” Psychologists then turned almost exclusively to behaviour, as described in terms of stimulus and response, and consciousness was totally bypassed as a subject. A survey of eight leading introductory psychology texts published between 1930 and the 1950s found no mention of the topic of consciousness in five texts, and in two it was treated as a historical curiosity.
Interest in Altered States
Beginning in the late 1950s, however, interest in the subject of consciousness returned, specifically in those subjects and techniques relating to altered states of consciousness: sleep and dreams, meditation, biofeedback, hypnosis, and drug-induced states. Much of the surge in sleep and dream research was directly fuelled by a discovery relevant to the nature of consciousness. A physiological indicator of the dream state was found: At roughly 90-minute intervals, the eyes of sleepers were observed to move rapidly, and at the same time the sleepers' brain waves would show a pattern resembling the waking state. When people were awakened during these periods of rapid eye movement, they almost always reported dreams, whereas if awakened at other times they did not. This and other research clearly indicated that sleep, once considered a passive state, was instead an active state of consciousness.
During the 1960s, an increased search for “higher levels” of consciousness through meditation resulted in a growing interest in the practices of Zen Buddhism and Yoga from Eastern cultures. A full flowering of this movement in the United States was seen in the development of training programs, such as Transcendental Meditation, that were self-directed procedures of physical relaxation and focused attention. Biofeedback techniques also were developed to bring body systems involving factors such as blood pressure or temperature under voluntary control by providing feedback from the body, so that subjects could learn to control their responses. For example, researchers found that persons could control their brain-wave patterns to some extent, particularly the so-called alpha rhythms generally associated with a relaxed, meditative state. This finding was especially relevant to those interested in consciousness and meditation, and a number of “alpha training” programs emerged.
Another subject that led to increased interest in altered states of consciousness was hypnosis, which involves a transfer of conscious control from the subject to another person. Hypnotism has had a long and intricate history in medicine and folklore and has been intensively studied by psychologists. Much has become known about the hypnotic state, relative to individual suggestibility and personality traits; the subject has now largely been demythologised, and the limitations of the hypnotic state are fairly well known. Despite the increasing use of hypnosis, however, much remains to be learned about this unusual state of focused attention.
Finally, many people in the 1960s experimented with the psychoactive drugs known as hallucinogens, which produce disorders of consciousness. The most prominent of these drugs are lysergic acid diethylamide, or LSD; and psilocybin; the latter two have long been associated with religious ceremonies in various cultures. LSD, because of its radical thought-modifying properties, was initially explored for its so-called mind-expanding potential and for its psychotomimetic effects (imitating psychoses). Little positive use, however, has been found for these drugs, and their use is highly restricted.
Consciousness Theory Today
As the concept of a direct, simple linkage between environment and behaviour became unsatisfactory in recent decades, the interest in altered states of consciousness may be taken as a visible sign of renewed interest in the topic of consciousness. That persons are active and intervening participants in their behaviour has become increasingly clear. Environments, rewards, and punishments are not simply defined by their physical character. Memories are organised, not simply stored. An entirely new area called cognitive psychology has emerged that centres on these concerns. In the study of children, increased attention is being paid to how they understand, or perceive, the world at different ages. In the field of animal behaviour, researchers increasingly emphasise the inherent characteristics resulting from the way a species has been shaped to respond adaptively to the environment. Humanistic psychologists, with a concern for self-actualisation and growth, have emerged after a long period of silence. Throughout the development of clinical and industrial psychology, the conscious states of persons in terms of their current feelings and thoughts were of obvious importance. The role of consciousness, however, was often de-emphasised in favour of unconscious needs and motivations. Trends can be seen, however, toward a new emphasis on the nature of states of consciousness.
Typical Sleep Cycle
Sleep has long been treated as a behavioural state. Nonetheless, some characteristics of brain physiology such as brain-wave patterns—as recorded by electroencephalography or EEG—are now accepted as part of its definition because of their unvarying association with sleep behaviour.
Stages of Sleep
The brain waves of a person go through certain constant changes, classified as stages 1 to 4, in the course of the sleep cycle. The EEG of a person in the waking state is characterised by alpha waves (8 to 12 cycles/sec) and low-voltage activity of mixed frequency, whereas sleep onset involves a disappearance of this alpha activity. Stage 1, considered the lightest stage of sleep, is characterised by low-voltage, desynchronised activity and sometimes by low-voltage, regular activity at 4 to 6 cycles/sec as well. After a few seconds or minutes, this gives way to stage 2, a pattern showing frequent spindle-shaped tracings on the EEG, called sleep spindles, at 13 to 15 cycles/sec, and certain high-voltage spikes known as K-complexes. Soon thereafter, stage 3 begins with the appearance of delta waves (high-voltage activity at 0.5 to 2.5 cycles/sec). Eventually, in stage 4, these delta waves occupy the major part of the record.
Dreaming Sleep
The categorisation of sleep records into these four stages is a somewhat arbitrary division of a continuous process. More important, sleep exhibits four or five periods of so-called emergence from stages, 2, 3, and 4 to a stage similar to stage 1. Persons awakened during these periods of emergence frequently—60 to 90 percent of the time—report that they have been dreaming. Such periods are characterised not only by stage-1 EEG patterns and by rapid conjugate (coupled) eye movements but also by many other distinguishing factors. Among these are a great irregularity in pulse rate, respiratory rate, and blood pressure; the presence of full or partial penile erections in the male; and generalised low muscular tone interrupted by movements in small muscle groups.
Periods of emergence thus differ markedly from typical stage-1 sleep as well as from the other three stages. Because of these distinguishing characteristics and because of their specific neurophysiological and chemical character (see below), these periods are now almost universally seen as constituting a separate state of sleep. Similar sleep periods are found in nearly all mammals and birds studied. These periods are referred to as D- (desynchronised or dreaming) sleep; the remainder of sleep is called S- (synchronised) sleep. These two states are also known, respectively, as REM (rapid-eye-movement) sleep and NREM (non-rapid-eye-movement) sleep; as paradoxical sleep and orthodox sleep; or as active sleep and quiet sleep.
Anomalies
The individual EEG changes characteristic of sleep may sometimes be deceptive. The deep, slow waves usually associated with sleep, for instance, can be found in the waking state under certain pharmacological conditions and are also seen during certain phases of anaesthesia or coma. Thus, when an EEG tracing is used to make a diagnosis of sleep, the regular cyclic pattern described above and the regular alternation of the two states are the most important phenomena, rather than any single characteristic wave form.
Time Allotments
Several characteristics of a typical night's sleep are found regularly and universally. First, the four or five periods of D-sleep that occur during the night take up a total time of about 90 minutes, a little more than 20 percent of total sleep time. Second, the first D-sleep period occurs about 70 to 120 minutes after the onset of sleep. This interval may be longer in some normal subjects, but it is significantly shorter only in a few abnormal clinical and experimental conditions such as narcolepsy; and the pattern occurs whether or not the person recalls any dreams.
Some time variations occur with age, however. The young always have more sleep time, and considerably more D-sleep time, than do adults, as in any mammalian species. The new-born child sleeps 16 to 18 hours; at least half of which is D-sleep. The young adult human spends 16 to 17 hours awake and 7 to 8 hours asleep, of which perhaps 6 hours are spent in S-sleep and 1.5 hours in D-sleep. Both S- and D-sleep, on the average, decrease slightly with increasing age. The same relationship appears to hold for other mammalian species.
Sleep in Other Species
As for other animals, most vertebrates may be said to display at least a primitive form of sleep, according to the above behavioural definition. Fish and amphibians have periods of quiescence accompanied by decreased response to environmental stimuli. Concomitant EEG or other recordings, however, have not demonstrated clear-cut sleep-versus-waking differences. Reptiles demonstrate sleep behaviour, and recordings show results somewhat similar to mammalian S-sleep; in a few instances, brief episodes of a state very much resembling D-sleep have been recorded as well. Birds have definite periods of both S- and D-sleep, although the D-periods are generally very short and account for a small percentage of total sleep time. All mammals have clear S- and D-sleep, with the possible exception of a single very primitive mammal, the spiny anteater.
Physiology and Chemistry of Sleep
A tremendous amount of knowledge has been accumulated about the central and peripheral mechanisms controlling and involving sleep. Basically, certain areas in the brain stem—the most primitive part of the brain and the part that controls such basic functions as breathing and heart rate—are involved in the control of the two sleep states. Considerable controversy still exists as to exactly which brain-stem regions are involved and how they interact, but it is known that several brain chemicals called biogenic amines—dopamine, norepinephrine, and serotonin—act as neurotransmitters and neuromodulators in regulating discharge of brain cells. The evidence is clearest for the involvement of serotonin. Serotonin is necessary for normal sleep to occur, although it is only one of many elements and is not sufficient in itself. The roles that norepinephrine and dopamine have in sleep are less certain.
Recent research demonstrates that the human nervous system controls the body's functions differently during the sleep states than during waking. The details are complex, but breathing mechanisms, temperature mechanisms, and musculature all function differently during sleep. Especially dramatic are the changes during D-sleep, in which core-body temperature is hardly controlled at all, so that mammals, including humans, become poikilothermic (cold-blooded). Differences in control mechanisms are becoming important in helping to characterise and understand a whole series of sleep-related diseases; for instance, in sleep apnea, breathing repeatedly stops or becomes very shallow during sleep.
Functions of Sleep and Sleep Requirements
Probably the most important and difficult question is that of the functions of sleep. This question has not been completely answered, and differences of opinion exist. Some scientists believe that sleep has no biological function and is simply a sort of habit. The predominance of evidence, however, suggests a biological function for sleep—in fact, most probably two functions, related to the two states of sleep. S-sleep tends to increase after exercise, after starvation, and at other times of increased metabolic need. Thus, S-sleep probably plays a role in the restoration of the body and brain, perhaps facilitating the synthesis of large molecules such as proteins and ribonucleic acids. D-sleep may play a more complex role in providing restoration for brain processes—especially some higher-level brain processes involved in focusing attention, waking ego mechanisms, performing subtle cognitive and social tasks, and so on.
The numerous investigations leading to these conclusions include studies of total sleep deprivation and of differential deprivation of different sorts of sleep, as well as studies of persons who always sleep 9 or more hours (long sleepers) and those who always sleep less than 6 hours (short sleepers). As the latter point indicates, a tremendous variation occurs in sleep requirements. Some persons function well on five hours of sleep a night, whereas others require ten hours; yet they are all physically and mentally normal. A person functioning with no sleep or almost none is occasionally heard of, but such reports have not been substantiated; apparently some sleep, at least four or five hours, is needed by everyone.
Sleep Disorders
A new field of clinical medicine is developing, related to psychiatry and neurology but not identical to either one. Called sleep medicine, it deals with sleep disorders, of which many kinds can be identified. Sleep problems are usually divided into three kinds: the insomnia’s, a group of problems producing difficulty in falling asleep or difficulty in staying asleep; hypersomnolence, characterised by too much sleep, or sleepiness when a person does not want to sleep; and episodic nocturnal events, consisting of disorders such as night terrors, nightmares, and sleepwalking .
Insomnia and hypersomnolence are only symptoms and may have many different causes. For example, insomnia can be caused by such conditions as painful arthritis; by endocrine disturbances; by the use of certain chemical substances or by the withdrawal from others (including alcohol); by psychological problems, such as anxiety and depression; and by disturbances in biorhythm such as jet lag. In terms of treatment, therefore, insomnia is not an illness that can be cured by a sleeping pill. Rather, the physician must determine and treat the insomnia's underlying cause.
Dreaming, form of mental activity, different from waking thought, which occurs during sleep. The nature of dream activity has been characterised by many clinical and laboratory studies. These studies show that dreams are more perceptual than conceptual: Things are seen and heard rather than being subjected to thought. In terms of the senses, visual experience is present in almost all dreams; auditory experience in 40 to 50 percent; and touch, taste, smell, and pain in a relatively small percentage. A considerable amount of emotion is commonly present—usually a single, stark emotion such as fear, anger, or joy rather than the modulated emotions that occur in the waking state. Most dreams are in the form of interrupted stories, made up partly of memories, with frequent shifts of scene.
This broad characterisation includes a great variety of dream experiences. Many dreams collected in sleep laboratories are rather ordinary, but most people have at least some bizarre dreams. At the start of the 20th century, Sigmund Freud proposed that a mental process quite different from that used in the waking state dominates the dreaming mind. He described this “primary process” as characterised by more primitive mechanisms, by rapid shifts in energy and emotions, and by a good deal of sexual and aggressive content derived from childhood.
Biology of Dreaming
Research in recent years has clarified many of these aspects of dreaming, but what may be of greatest significance has been the discovery of biology of dreaming. Starting with the work of the American sleep researchers Eugene Aserinsky and Nathaniel Kleitman in 1953, studies have shown that a dream does not consist of fleeting imagery that occurs while a person awakens from sleep, but instead that it takes place during a biological state of its own.
Thus, two clearly distinguishable states of sleep exist. The first state, called S-synchronised sleep, or NREM-sleep (non-rapid-eye-movement sleep), occupies most of the sleep period and is associated with a relatively low pulse and blood pressure, little activation of the autonomic nervous system, and few or no reports of dreaming. The second type of sleep, known as D-sleep (dreaming, or desynchronised, sleep), or REM-sleep (rapid-eye-movement sleep), occurs cyclically during the sleep period and is characterised by activation of the autonomic nervous system, rapid eye movements, and frequent dream reports. Typically, a person has four or five periods of D-sleep during the night, whether the dreams are remembered often, rarely, or not at all; they occur at intervals of about 90 minutes and altogether constitute about 25 percent of the night's sleep (as much as 50 percent in a new-born child). Evidence indicates that a dream period usually lasts from 5 to 20 minutes.
Such stimuli as sounds and touches impinging on a dreamer can be incorporated into a dream if they occur during a D-period. These stimuli, however, do not initiate a D-period if one is not already in progress, so that, at least in such cases, dreams do not “protect” sleep in the way that Freud suggested. Although mental activity may be reported during NREM-sleep, these are usually short, fragmented, thought like experiences.
Other Animals
As to whether other animals dream, a definite statement can be made for mammals, at least, that they do have D-sleep periods; and reasons exist for thinking that dreams occur during these periods. For example, other mammals as well as humans show intense activation of the visual cortex during D-sleep, and in humans this corresponds to the experiencing of visual sensations. One study further demonstrated that monkeys that had been trained to push a lever whenever they saw pictures on a screen in front of them as they awoke in a dark room suddenly began to push the lever a number of times during their sleep periods.
Dream Content
This new knowledge of the biology of dreaming does not suggest that dreams have no meaning. Dreams are meaningful mental products, just as thoughts and daydreams are. They express important wishes, fears, concerns, and worries of the dreamer; so undoubtedly the study and analysis of dreams can sometimes be a useful procedure, revealing different aspects of a person's mental functioning.
Consciousness, States of, no simple, agreed-upon definition of consciousness exists. Attempted definitions tend to be tautological (for example, consciousness defined as awareness) or merely descriptive (for example, consciousness described as sensations, thoughts, or feelings). Despite this problem of definition, the subject of consciousness has had a remarkable history. At one time the primary subject matter of psychology, consciousness as an area of study suffered an almost total demise, later re-emerging to become a topic of current interest.
Historical Background
Most of the philosophical discussions of consciousness arose from the mind-body issues posed by the French philosopher and mathematician René Descartes in the 17th century. Descartes asked: Is the mind, or consciousness, independent of matter? Is consciousness extended (physical) or unextended (non-physical)? Is consciousness determinative, or is it determined? English philosophers such as John Locke equated consciousness with physical sensations and the information they provide, whereas European philosophers such as Gottfried Wilhelm Leibniz and Immanuel Kant gave a more central and active role to consciousness.
The philosopher who most directly influenced subsequent exploration of the subject of consciousness was the 19th-century German educator Johann Friedrich Herbart, who wrote that ideas had quality and intensity and that they may inhibit or facilitate one another. Thus, ideas may pass from “states of reality” (consciousness) to “states of tendency” (unconsciousness), with the dividing line between the two states being described as the threshold of consciousness. This formulation of Herbart clearly presages the development, by the German psychologist and physiologist Gustav Theodor Fechner, of the psychophysical measurement of sensation thresholds, and the later development by Sigmund Freud of the concept of the unconscious.
Foundations of Modern Research
The experimental analysis of consciousness dates from 1876, when the German psychologist Wilhelm Max Wundt started his research laboratory. For Wundt, the task of psychology was the study of the structure of consciousness, which extended well beyond sensations and included feelings, images, memory, attention, duration, and movement. Because early interest focused on the content and dynamics of consciousness, it is not surprising that the central methodology of such studies was introspection; that is, subjects reported on the mental contents of their own consciousness. This introspective approach was developed most fully by the American psychologist Edward Bradford Titchener at Cornell University. Setting his task as that of describing the structure of the mind, Titchener attempted to detail, from introspective self-reports, the dimensions of the elements of consciousness. For example, taste was “dimensionalised” into four basic categories: sweet, sour, salt, and bitter. This approach was known as structuralism.
By the 1920s, however, a remarkable revolution had occurred in psychology that was to essentially remove considerations of consciousness from psychological research for some 50 years: Behaviourism captured the field of psychology. The main initiator of this movement was the American psychologist John Broadus Watson. In a 1913 article, Watson stated, “I believe that we can write a psychology and never use the terms consciousness, mental states, mind . . . imagery and the like.” Psychologists then turned almost exclusively to behaviour, as described in terms of stimulus and response, and consciousness was totally bypassed as a subject. A survey of eight leading introductory psychology texts published between 1930 and the 1950s found no mention of the topic of consciousness in five texts, and in two it was treated as a historical curiosity.
Interest in Altered States
Beginning in the late 1950s, however, interest in the subject of consciousness returned, specifically in those subjects and techniques relating to altered states of consciousness: sleep and dreams, meditation, biofeedback, hypnosis, and drug-induced states. Much of the surge in sleep and dream research was directly fuelled by a discovery relevant to the nature of consciousness. A physiological indicator of the dream state was found: At roughly 90-minute intervals, the eyes of sleepers were observed to move rapidly, and at the same time the sleepers' brain waves would show a pattern resembling the waking state. When people were awakened during these periods of rapid eye movement, they almost always reported dreams, whereas if awakened at other times they did not. This and other research clearly indicated that sleep, once considered a passive state, was instead an active state of consciousness.
During the 1960s, an increased search for “higher levels” of consciousness through meditation resulted in a growing interest in the practices of Zen Buddhism and Yoga from Eastern cultures. A full flowering of this movement in the United States was seen in the development of training programs, such as Transcendental Meditation, that were self-directed procedures of physical relaxation and focused attention. Biofeedback techniques also were developed to bring body systems involving factors such as blood pressure or temperature under voluntary control by providing feedback from the body, so that subjects could learn to control their responses. For example, researchers found that persons could control their brain-wave patterns to some extent, particularly the so-called alpha rhythms generally associated with a relaxed, meditative state. This finding was especially relevant to those interested in consciousness and meditation, and a number of “alpha training” programs emerged.
Another subject that led to increased interest in altered states of consciousness was hypnosis, which involves a transfer of conscious control from the subject to another person. Hypnotism has had a long and intricate history in medicine and folklore and has been intensively studied by psychologists. Much has become known about the hypnotic state, relative to individual suggestibility and personality traits; the subject has now largely been demythologised, and the limitations of the hypnotic state are fairly well known. Despite the increasing use of hypnosis, however, much remains to be learned about this unusual state of focused attention.
Finally, many people in the 1960s experimented with the psychoactive drugs known as hallucinogens, which produce disorders of consciousness. The most prominent of these drugs are lysergic acid diethylamide, or LSD; and psilocybin; the latter two have long been associated with religious ceremonies in various cultures. LSD, because of its radical thought-modifying properties, was initially explored for its so-called mind-expanding potential and for its psychotomimetic effects (imitating psychoses). Little positive use, however, has been found for these drugs, and their use is highly restricted.
Consciousness Theory Today
As the concept of a direct, simple linkage between environment and behaviour became unsatisfactory in recent decades, the interest in altered states of consciousness may be taken as a visible sign of renewed interest in the topic of consciousness. That persons are active and intervening participants in their behaviour has become increasingly clear. Environments, rewards, and punishments are not simply defined by their physical character. Memories are organised, not simply stored. An entirely new area called cognitive psychology has emerged that centres on these concerns. In the study of children, increased attention is being paid to how they understand, or perceive, the world at different ages. In the field of animal behaviour, researchers increasingly emphasise the inherent characteristics resulting from the way a species has been shaped to respond adaptively to the environment. Humanistic psychologists, with a concern for self-actualisation and growth, have emerged after a long period of silence. Throughout the development of clinical and industrial psychology, the conscious states of persons in terms of their current feelings and thoughts were of obvious importance. The role of consciousness, however, was often de-emphasised in favour of unconscious needs and motivations. Trends can be seen, however, toward a new emphasis on the nature of states of consciousness.
posted by docstu at 6:04 AM
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