7. ROLE OF CONSCIOUS CONTROL AND BIORHYTHMS IN ORGANISM’S ACTIVITY
Consciousness is special form of perceiving surroundings and goal-orientated activity of person with interrelation to surroundings. Only social life forms consciousness. It involves life experience of entire society.
This ability of prefrontal areas to keep track of many bits of information could well explain abilities to prognosticate, do plan for the future, delay action in response to incoming sensory signals, consider the consequences of motor actions even before they are performed, solve complicated mathematical, legal, or philosophical problems, correlate all avenues of information in diagnosing rare diseases and control our activities in accord with moral laws.
Wilhelm Wundt’s investigations of consciousness, begun in 1879, were central to the development of psychology as a field of study. Wundt’s approach, called structuralism, sought to determine the structure of consciousness by recording the verbal descriptions provided by laboratory subjects to various stimuli, a method that became known as introspection.
The next major approach to the study of consciousness was the functionalism of William James, who focused on how consciousness helps people adapt to their environment. Behaviorism, pioneered by John B. Watson in the early 1900s, shifted interest from conscious processes to observable behaviors, and the study of consciousness faded into the background for almost half a century, especially in the United States, until it was revived by the “cognitive revolution” that began in the 1950s and 1960s.
The existence of different levels of consciousness was at the heart of Sigmund Freud’s model of human mental functioning.
In addition to the conscious level, consisting of thoughts and feelings of which one is aware, Freud proposed the existence of the unconscious, a repository for thoughts and feelings that are repressed because they are painful or unacceptable to the conscious mind for some other reason.
He also formulated the concept of the preconscious, which functions as an intermediate or transitional level of mind between the unconscious and the conscious.
A preconscious thought can quickly become conscious by receiving attention, and a conscious thought can slip into the preconsciouswhen attention is withdrawn from it. In contrast, the repressed material contained in the unconscious can only be retrieved through some special technique, such as hypnosis or dream interpretation. (What Freud called the unconscious is today referred to by many psychologists as the subconscious.)
Freud’s contemporary, Carl Jung, posited the existence of a collective unconscious shared by all people which gathers together the experiences of previous generations.
The collective unconscious contains images and symbols, called archetypes, that Jung found are shared by people of diverse cultures and tend to emerge in dreams, myths, and other forms.
In Jung’s view, a thorough analysis of both the personal and collective unconscious was necessary to fully understand the individual personality
Biological and Environmental “Clocks” That Regulate Consciousness
Throughout the course of the day, there is a natural ebb and flow to consciousness. The most obvious variation of consciousness that we experience is the daily sleep–wake cycle. But conscious states also change in more subtle ways. For example, you’ve probably noticed that your mental alertness varies throughout the day in a relatively consistent way. Most people experience two distinct peaks of mental alertness: one in the morning, usually around 9:00 or 10:00 A.M., and one in the evening, around 8:00 or 9:00 P.M. In between these two peaks, you’ll probably experience a slump in mental alertness at about 3:00 P.M. And, should you manage to stay awake, your mental alertness will probably reach its lowest point at about 3:00 A.M. One practical implication of this consistent daily pattern is the increase in the number of traffic accidents at the times when mental alertness is at its lowest points.
Mental alertness and the sleep–wake cycle are just two examples of the daily highs and lows you experience in a wide variety of bodily processes. These daily cycles are called circadian rhythms. The word circadian combines the Latin words for “about” and “day.” So, the term circadian rhythms refers to biological processes that systematically vary over a period of about 24 hours.You actually experience many different circadian rhythms that ebb and flow over the course of any given 24-hour period. Researchers have discovered over 100 bodily processes that rhythmically peak and dip each day, including blood pressure, the secretion of different hormones, and pain sensitivity.
Normally, your circadian rhythms are closely synchronized with one another. For example, the circadian rhythm for the release of growth hormone is synchronized with the sleep–wake circadian rhythm so that growth hormone is released only during sleep.
The Suprachiasmatic Nucleus – The Body’s Clock
Your many circadian rhythms are controlled by a master biological clock—a tiny cluster of neurons in the hypothalamus in the brain. Thiscluster of neurons is called the suprachiasmatic nucleus, abbreviated SCN. The SCN is the internal pacemaker that governs the timing of circadian rhythms, including the sleep–wake cycle and the mental alertness cycle (Weaver, 1998). Keeping the circadian rhythms synchronized with oneanother and on a 24-hour schedule also involves environmental time cues. The most important of these cues isbright light, especially sunlight. In people, light detected by special photoreceptors in the eye is communicated via thevisual system to the SCN in the hypothalamus (Brainard
& others, 2001a, 2001b).
How does sunlight help regulate the sleep–wake cycle and other circadian rhythms? As the sun sets each day, the decrease in available light is detected by the SCN through its connections with the visual system. In turn, the SCN triggers an increase in the production of a hormone called melatonin.
Melatonin is manufactured by the pineal gland, an endocrine gland located in the brain. Increased blood levels of melatonin make you sleepy and reduce activity levels. At night, blood levels of melatonin rise, peaking between 1:00 and 3:00 A.M. Shortly before sunrise, the pineal gland all but stops producing melatonin, and you soon wake up. As the sun rises, exposure to sunlight and other bright light suppresses melatonin levels, and they remain very low throughout the day. In this way, sunlight entrains, or sets, the SCN so that it keeps circadian cycles synchronized and operating on a 24-hour schedule (Czeisler & Wright, 1999; Lavie, 2001).
Life Without a Sundial
Free-Running Circadian Rhythms Given that sunlight is responsible for setting your internal clock, what would happen to the timing of your circadian rhythms if they were allowed to “run free” in the absence of environmental time cues like sunlight and clocks? To create free-running conditions, researchers typically use underground isolation units. In some studies, they have even constructed rooms in caves. Volunteers live in these underground bunkers for weeks or months at a time, deprived of all environmental time cues (Webb, 1994).
Under free-running conditions, two distinct effects occur (Kronauer, 1994; Lewy & Sack, 1987). First, in the absence of normal light, darkness, and other time cues, people tend to drift to the natural rhythm of the suprachiasmatic nucleus—roughly a 25-hour day, not a 24-hour day. Thus, people in a free-running condition go to sleep about an hour later each day. Exactly why the human sleep–wake cycle gravitates toward a 25-hour cycle—and under what conditions—is an issue that continues to be actively researched and debated (
Second, under free-running conditions, circadian rhythms lose their normal synchronization with one another (Aschoff, 1993, 1994). All circadian rhythms becomelonger, but to different degrees. For example, normally the sleep–wake cycle, body temperature, and the melatonin cycle are closely coordinated. At about 3:00 A.M., your body temperature dips to its lowest point, just as melatonin is reaching its highest level and you are at your sleepiest. But in the absence of environmental cues, the sleep–wake, body temperature, and melatonin–circadian rhythms become desynchronized, so that they are no longer properly coordinated with one another.
What happens when people leave the free-running condition and are once again exposed to normal daylight and darkness cues? Within days, sunlight resets the biological clock. Circadian rhythms become synchronized again and resume operating on a 24-hour rather than a 25-hour cycle (Lewy & Sack, 1987). Circadian Rhythms and the Blind Many blind people have free-running circadian cycles because they are unable to detect the light that normally sets the SCN. Like people deprived of environmental time cues, blind people can experience free-running melatonin, body temperature, and sleep–wake circadian cycles (Czeisler & others, 1995; Klerman & others, 1998). Consequently, many blind people suffer from recurring bouts of insomnia and other sleep problems (Leger & others, 1999; Sack & others, 1992).
Circadian Rhythms and Sunlight
Some Practical Implications
The close tie between your internal biological clock and environmental time cues has some very important practical applications. For example, imagine that you leave
Although numerous physiological variables are involved in jet lag, the circadian cycle of the hormone melatonin plays a key role. When it’s 10:00 A.M. in
You don’t need to travel across multiple time zones to experience symptoms of jet lag. People who work night shifts or rotating shifts often suffer from jet lag symptoms because their circadian rhythms are out of sync with daylight and darkness time cues (Monk, 1997). Like Nina in the Prologue, nurses, doctors, and other medical personnel often have to work night shifts or rotating shifts. So do people working in law enforcement and the military, broadcasting and weather services, and other businesses that operate around the clock.
For night workers, the problem of being out of sync with the environmental clock is compounded every morning when they return home in the bright morning light. Exposure to bright morning light is a potent stimulus that can reset the body clock to a day schedule (Shanahan & Czeisler, 1991). Even traces of sunlight through curtains can prevent a person’s body clock from staying in sync with the night work schedule. Because sunlight time cues exert such a powerful influence on circadian rhythms, many night-shift workers never fully adjust to a nighttime work schedule.
The Dawn of Modern Sleep Research
The invention of the electroencephalograph by German psychiatrist Hans Berger in the 1920s gave sleep researchers an important tool for measuring the rhythmic electrical activity of the brain (Stern, 2001). These rhythmical patterns of electrical activity are referred to as brain waves. The electroencephalograph produces a graphic record called an EEG, or electroencephalogram. By studying EEGs, sleep researchers have firmly established that brain-wave activity systematically changes throughout sleep.
Along with brain activity, today’s sleep researchers monitor a variety of other physical functions during sleep. Eye movements,muscle movements, breathing rate, airflow, pulse, blood pressure, amount of exhaled carbon dioxide, body temperature, and breathing sounds are just some of the body’s functions that are measured in contemporary sleep research (Ancoli-Israel, 1997; Cooper & Bradbury, 1994). The next milestone in sleep research occurred in the early 1950s. Eugene Aserinsky, a graduate student at the
Monitoring Sleep Using electrodes that are attached harmlessly to the face and scalp, the electroencephalograph records the brain’s electrical activity throughout the night. Although the equipment may look cumbersome and uncomfortable, people generally sleep just fine with all the wires attached.
The Onset of Sleep and Hypnagogic Hallucinations
Awake and reasonably alert as you prepare for bed, your brain generates small, fast brain waves, called beta brain waves. After your head hits the pillow and you close your eyes, your muscles relax. Your brain’s electrical activity gradually gears down, generating slightly larger and slower alpha brain waves. As drowsiness sets in, your thoughts may wander and become less logical.
During this drowsy, presleep phase, you may experience odd but vividly realistic sensations. You may hear your name called or a loud crash, feel as if you’re falling or floating, smell something burning, or see kaleidoscopic patterns or an unfolding landscape. These vivid sensory phenomena that occasionally occur during the transition from wakefulness to light sleep are called hypnagogic hallucinations (Mavromatis, 1987). Some hypnagogic hallucinations can be so vivid or startling that they cause a sudden awakening.
Probably the most common hypnagogic hallucination is the vivid sensation of falling. The sensation of falling is often accompanied by a myoclonic jerk—an involuntary muscle spasm of the whole body that jolts the person completely awake (Cooper, 1994). Also known as sleep starts, these experiences can seem really weird (or embarrassing) when they occur. But, you can rest assured, they are not abnormal. Almost all of our students have reported occasionally experiencing the hypnagogic hallucination of falling combined with a myoclonic jerk.
The First 90 Minutes of Sleep and Beyond The course of a normal night’s sleep follows a relatively consistent cyclical pattern. As you drift off to sleep, you enter NREM sleep and begin a progression through the four NREM sleep stages. Each progressive NREM sleep stage is characterized by corresponding decreases in brain and body activity. On average, the progression through the first four stages of NREM sleep occupies the first 50 to 70 minutes of sleep (Cooper, 1994).
Stage 1 NREM
As the alpha brain waves of drowsiness are replaced by even slower theta brain waves, you enter the first stage of sleep. Lasting only a few minutes, stage 1 is a transitional stage during which you gradually disengage from the sensations of the surrounding world. Familiar sounds, such as the hum of the refrigerator or the sound of traffic, gradually fade from conscious awareness. During stage 1 NREM, you can quickly regain conscious alertness if needed. Although hypnagogic experiences can occur in stage 1, less vivid mental imagery is common, such as imagining yourself engaged in some everyday activity, much as Mike imagined himself unpacking boxes at work. Although dreamlike, these images lack the unfolding, sometimes bizarre details of a true dream.
Stage 2 NREM
Stage 2 represents the onset of true sleep. Stage 2 sleep is defined by the pearance of sleep spindles, brief bursts of brain activity that last a second or two, and K complexes, single but large high-voltage spikes of brain activity that periodically occur (see Figure 4.2). Other than these occasional sleep spindles, brain activity continues to slow down considerably. Breathing becomes rhythmical. Slight muscle twitches may occur. Theta waves are predominant in stage 2, but large, slow brain waves, called delta brain waves, also begin to emerge. During the 15 to 20 minutes initially spent in stage 2, delta brain-wave activity gradually increases.
Stage 3 and Stage 4 NREM
Stages 3 and 4 of NREM are physiologically very similar. Both stages are defined by the amount of delta brain-wave activity. In combination, stages 3 and 4 are sometimes referred to as slow-wave sleep. When delta brain waves represent more than 20 percent of total brain activity, the sleeper is said to be in stage 3 NREM. When delta brain waves exceed 50 percent of total brain activity, the sleeper is said to be in stage 4 NREM (Cooper, 1994).
During the 20 to 40 minutes spent in the night’s first episode of stage 4 NREM, delta waves eventually come to represent 100 percent of brain activity. At that point, heart rate, blood pressure, and breathing rate drop to their lowest levels. Not surprisingly, the sleeper in stage 4 NREM is virtually oblivious to the world. Noises as loud as 90 decibels may fail to wake him (Empson, 1993). However, his muscles are still capable of movement. For example, if sleepwalking occurs, it typically happens during stage 4 NREM sleep.
It can easily take 15 minutes or longer to regain full waking consciousness from stage 4. It’s even possible to answer a ringing phone, carry on a conversation for several minutes, and hang up without ever leaving stage 4 sleep—and without remembering the conversation the next day. When people are briefly awakened by sleep researchers during stage 4 NREM and asked to perform some simple task, they often don’t remember it the next morning (Dinges, 1990; Goodenough, 1991).
In both sexes, sexual arousal may occur, which is not necessarily related to dream content. This first REM episode tends to be brief, about 5 to 15 minutes. From the beginning of stage 1 NREM sleep through the completion of the first episode of REM sleep, about 90 minutes have elapsed. Beyond the First 90 Minutes Throughout the rest of the night, the sleeper cycles between NREM and REM sleep. Each cycle lasts about 90 minutes on average, but the duration of cycles may vary from 70 to 120 minutes. Usually, four more 90-minute cycles of NREM and REM sleep occur during the night. Just before and after REM periods, the sleeper typically shifts position (Hobson, 1995). The progression of a typical night’s sleep cycles. Stages 3 and 4 NREM, slow-wave sleep usually occur only during the first two 90-minute cycles. As the night progresses, REM sleep episodes become increasingly longer and less time is spent in NREM. During the last two 90-minute sleep cycles before awakening, NREM sleep is composed primarily of stage 2 sleep and periods of REM sleep can last as long as 40 minutes. In a later section, we’ll look at dreaming and REM sleep in more detail. Changes in Sleep Patterns over the Lifespan Over the course of our lives, the quantity and quality of our sleep change considerably. REM sleep begins long before birth, as scientists have discovered by using ultrasound to document fetal eye movements and by studying the sleep of premature infants. Four months before birth, REM sleep seems to constitute virtually all of fetal life.
By one month before birth, the fetus demonstrates distinct sleep–wake cycles, spending around 12 hours each day in REM sleep (Mindell, 1997).
A newborn sleeps about 16 hours a day, about 50 percent of which is REM sleep. By the end of the first year of life, total sleep time drops to around 13 hours a day, about one-third of which is REM sleep. In general, from birth onward, the average amount of time spent sleeping each day gradually decreases (see Figure 4.4). The amount of time devoted to REM sleep and slow-wave NREM sleep each night also gradually decreases over the lifespan (Bliwise, 1997).Young children can easily spend two hours or more each night in the deep sleep of stages 3 and 4 NREM. By early adulthood, about an hour is spent in deep sleep each night. And by late adulthood, only about 20 minutes of a night’s sleep is spent in stages 3 and 4 NREM sleep (Williams & others, 1994). By the time people reach their sixties, total sleep time averages about six hours per night and the quality of sleep is much more shallow. That we have a biological need for sleep is clearly demonstrated by sleep deprivation studies. After as little as one night’s sleep deprivation, research subjects develop microsleeps, which are episodes of sleep lasting only a few seconds that occur during wakefulness. People who go without sleep for a day or more also experiencedisruptions in mood, mental abilities, reaction time, perceptual skills, and complex motor skills (Gökcebay & others, 1994).
Getting less sleep than you need (as many adults do) can also have negative effects. In one study, young men whose sleep was restricted to four hours a night for as few as six consecutive nights experienced harmful changes in metabolic and endocrine functioning (Spiegel & others, 1999). As sleep researcher Eve Van Cauter (1999) explained, “After only one week of sleep restriction, young, healthy males had glucose levels that were no longer normal. That’s a rapid deterioration of the body’s functions.” Sleep researchers have also selectively deprived people of different components of normal sleep. For example, to study the effects of REM deprivation, researchers wake sleepers whenever the monitoring instruments indicate that they are entering REM sleep. After several nights of being selectively deprived of REM sleep, the subjects are allowed to sleep uninterrupted. What happens? The first time subjects are allowed to sleep without interruption, they experience REM rebound—the amount of time spent in REM sleep increases by as much as 50 percent (Ellman & others, 1991). Similarly, when people are selectively deprived of NREM stages 3 and 4, they experience NREM rebound, spending more time in NREM sleep. The phenomena of REM rebound and NREM rebound seem to indicate that the braieeds to make up for missing components of sleep. Clearly, we need both to sleep and to experience the full range of sleep stages. But what particular functions does sleep serve? The restorative theory of sleep suggests that sleep promotes physiological processes that restore and rejuvenate the body and the mind (Gökcebay & others, 1994). According to this theory, NREM and REM sleep serve different purposes. NREM sleep is thought to be important for restoring the body, whereas REM sleep is thought to restore mental and brain functions (Maquet, 2001; Stickgold & others, 2001).
Evidence supporting the role of NREM sleep in restoring the body comes from studies that have demonstrated increased deep sleep following sleep deprivation, starvation, and strenuous athletic activity. The secretion of growth hormone, testosterone, prolactin, and other hormones increases during NREM sleep (Hirshkowitz & others, 1997).
The importance of REM sleep in mental and brain functions is suggested by the abundance of REM sleep in the developing fetus, in infants, and in young children and its subsequent decrease throughout adulthood. Tentatively, this suggests that REM sleep plays some role in stimulating the high rate of brain development that occurs in the early stages of the lifespan. In contrast to the restorative theory, the adaptive theory of sleep suggests that the sleep patterns exhibited by different animals, including humans, are the result of evolutionary adaptation (Webb, 1975). Also called the evolutionary theory of sleep, the basic idea is that different sleep patterns evolved as a way of preventing a particular species from interacting with the environment when doing so is most hazardous. Animals with few natural predators, such as gorillas and lions, sleep as much as 15 hours a day. In contrast, grazing animals, such as cattle and horses, tend to sleep in short bursts that total only about 4 hours per day. Hibernation patterns of animals such as bears and gophers also coincide with periods during which environmental conditions pose the greatest threat to survival. Although there is evidence to support both the restorative and the adaptive theories of sleep, many questions remain. The bottom line is that researchers still aren’t sure exactly what physiological functions are served by sleep (Maquet, 2001). Sleep may well fulfill multiple purposes.
Sleep disorders are serious disturbances in the normal sleep pattern that interfere with daytime functioning and cause subjective distress (American Psychiatric Association, 2000a). Virtually everyone is seriously troubled by the quality or quantity of their sleep at some point. And, if you happen to be someone who regularly experiences sleep-related problems, you’re not alone. According to the 2002 Sleep in America Poll, seven out of ten American adults report frequent sleep problems, including inadequate amounts of sleep.
Insomnia
By far the most common sleep complaint among adults is insomnia (Dement & Pelayo, 1997). According to the 2002 National Sleep Foundation survey, 58 percent of adults are affected a few nights or more each week by at least one symptom of insomnia, such as waking up and being unable to go back to sleep. Insomnia is not defined solely on the basis of the amount of time a person sleeps, because people vary in how much sleep they need to feel refreshed. Rather, people are said to experience insomnia when they repeatedly complain about the quality or duration of their sleep, have difficulty going to sleep or staying asleep, or wake before it is time to get up. For an estimated 12 million Americans, complaints of insomnia are related to a condition called restless legs syndrome, abbreviated RLS. People with RLS complain of unpleasant creeping, crawling, tingling, itching, or prickling sensations deep inside their lower legs accompanied by an irresistible urge to move (National Institute of Neurological Disorders and Stroke, 2001). These sensations are most prominent in the evening and at night, especially when the individual lies down or sits still for any length of time (Rothenberg, 1997). Moving the legs temporarily reduces the unpleasant sensations but also interferes with the person’s ability to fall asleep or stay asleep.
More commonly, insomnia can often be traced to stressful life events, such as job or school difficulties, troubled relationships, the death of a loved one, or financial problems. Concerns about sleeping can add to whatever waking anxieties the person may already be experiencing. This can create a vicious circle— worrying about the inability to sleep makes troubled sleep even more likely, further intensifying anxiety. Numerous studies have shown that behavior therapy and different medications are effective in the short-term treatment of insomnia (M. T. Smith & others, 2002). Behavioral techniques often help people develop better sleep habits. For example, a treatment called stimulus control conditions the person to associate the bed only with sleepiness and sleep, rather than with watching television, talking on the phone, or other nonsleep activities. Relaxation training and meditation, which we will discuss later in the chapter, are also commonly used to treat insomnia (Murtagh & Greenwood, 1995).
Educating people on sleep hygiene is often part of the successful treatment of insomnia. For example, many people troubled by the inability to sleep use alcohol or over-the-counter sleep medications to induce sleep. In the Prologue to this chapter, you saw how Mike resorted to a stiff drink to help him relax and go back to sleep. Although such remedies may temporarily help people fall asleep, both sleeping pills and alcohol disrupt normal sleep cycles, including REM sleep (Roehrs & Roth, 2001). Even the sleep-inducing medications sometimes prescribed by physicians to treat insomnia must be carefully managed to avoid drug dependence.
Sleep Apnea
The second most common sleep disorder, sleep apnea, affects some 20 million Americans (Carskadon & Taylor, 1997). In sleep apnea, the sleeper repeatedly stops breathing during the night. Carbon dioxide builds up in the blood, causing a momentary awakening, during which the sleeper snorts or gulps in air. Breathing may stop for as little as 10 seconds or for so long that the sleeper’s skin turns blue before he or she wakes up. During a single night, more than 300 sleep apnea attacks can occur. Often the person has no recollection of the repeated awakenings but feels sleepy throughout the following day (Orr, 1997). Sleep apnea is more common in men over the age of 50, especially those who are overweight. Special mouthpieces, weight loss, and surgical intervention have been effective in treating sleep apnea. For people who suffer from sleep apnea only when they sleep on their backs, treatment is sometimes as simple as sewing a tennis ball to the back of their pajama tops, which forces them to sleep on their sides (Saskin, 1997).
Sleepwalking and Night Terrors
Unlike insomnia, sleepwalking and night terrors are much more common in children than in adults (Lask, 1995; Mindell, 1993). These sleep disturbances occur during the deepest stages of NREM sleep, stages 3 and 4. As noted previously, young children spend considerably more time each night in deep sleep than do adolescents or adults (Whyte & Schaefer, 1995). Not surprisingly, most instances of bedwetting, or nocturnal enuresis, also tend to occur when the child is in deep sleep (Barclay & Houts, 1995a).
About 25 percent of all children have at least one episode of sleepwalking, also known as somnambulism. Sleepwalking typically occurs during the first three hours after the child has gone to sleep. The child gets out of bed and moves about in a slow, poorly coordinated, automatic manner, usually with a blank, staring look on his face. Surprisingly, the sleepwalking child is usually able to navigate around objects without much difficulty. However, the child’s general lack of awareness of his surroundings is evident. The sleepwalker may try to dress, eat, or go to the bathroom in the wrong location (Ozbayrak & Berlin, 1995). Night terrors, or sleep terrors, also typically occur during stage 3 or 4 NREM sleep in the first few hours of sleep. Physiologically, a night terror is much more intense than a run-of-the-mill nightmare. The first sign of a night terror is sharply increased physiological arousal—restlessness, sweating, and a racing heart. Typically, the child experiencing night terrors abruptly sits up in bed and lets out a panic-stricken scream or cry for help as she thrashes about in bed or even sleepwalks.
Terrified and disoriented, the child may struggle with a parent who tries to calm her down. Night terrors tend to be brief, usually lasting only a matter of seconds. Amazingly, the child almost immediately goes back to quiet sleep and wakes in the morning with no recollection of the incident. Unlike the unfolding dream story of a nightmare, night terrors are usually accompanied by a single but terrifying sensation, such as being crushed or falling. Often, the child imagines that she is choking or that a frightening figure is present, such as a threatening animal or monster (Kahn & others, 1991). Though dramatic, night terrors are not regarded as a true sleep disorder or psychological problem unless they occur frequently.
For the vast majority of children who often experience night terrors, the problem usually resolves itself by early adolescence (Lask, 1995).
REM Sleep Behavior Disorder
Another,more serious parasomnia is REM sleep behavior disorder (Mahowald & Schenck, 1990). REM sleep behavior disorder typically affects men over the age of 60 and is characterized by the brain’s failure to suppress voluntary muscle movements during REM sleep. Consequently, the dreamer acts out his dreams, sometimes leaping out of bed, lashing out at imagined intruders, or tackling a chest of drawers. Such behavior might seem comical if the potential for serious injury to the sleeper or the sleeper’s bed partner weren’t so great. Evidence suggests that the cause of REM sleep behavior disorder is deterioration or damage in the lower brain centers that control physical and mental arousal during sleep (Zoltoski & Gillin, 1994).
Narcolepsy
If you’ve ever tried to stay awake for 36 hours or longer, you know how incredibly sleepy you can get. That experience gives you an inkling of what life is like for people with narcolepsy. The most common, and most troubling, symptom of narcolepsy is excessive and recurring bouts of daytime sleepiness. People with narcolepsy experience an overwhelming sleepiness, lapsing into brief periods of sleep throughout the day that usually last an hour or less. These daytime sleep episodes occur regardless of how much nighttime sleep the person has had. They also often occur at inappropriate times, such as in the middle of a meeting. The onset of these daytime sleep episodes is sometimes accompanied by frightening hypnagogic hallucinations, such as the house or building being on fire. As the person awakens, he or she may briefly experience the sensation of being unable to move, which is termed sleep paralysis.
When these daytime sleep episodes occur suddenly, they are termed “sleep attacks.” Along with excessive daytime sleepiness, narcolepsy is often characterized by regular episodes of cataplexy. Cataplexy is the sudden loss of voluntary muscle strength and control, lasting from several seconds to several minutes. Cataplexy is usually triggered by a sudden, intense emotion, such as laughter, anger, or surprise. In mild episodes, the person’s head may droop or facial muscles sag (Siegel, 2000). In more severe episodes, the person may completely lose muscle control. As shown in the accompanying series of photos, the person’s knees buckle and he collapses on the floor. The onset of narcolepsy typically occurs during adolescence, and it is considered a chronic, lifelong condition. Although estimates vary, approximately 250,000 Americans have narcolepsy, and it affects men and women equally (Carskadon & Taylor, 1997; Littner, 2001). Genetics seems to play an important role, as the disorder tends to run in families (Mignot, 1998). Adding to the genetic evidence, scientists have identified the genes that produce narcoleptic symptoms in mice and dogs (Chemelli & others, 1999; Lin & others, 1999).
Although the cause of narcolepsy is still unknown, recent evidence suggests that people with narcolepsy lack a hormone called hypocretin, which is manufactured in the brain’s hypothalamus (Nishino & others, 2000). Hypocretin is involved in regulating arousal, sleep, and eating behavior (Hungs & Mignot, 2001; Mignot, 2001). Many sleep researchers are hopeful that such discoveries will lead to new treatments for this debilitating sleep disorder. Although narcolepsy cannot be cured, a drug called modafinil (Provigil), reduces daytime sleepiness in people with narcolepsy (Schwartz & others, 2000). Antidepressant medications can reduce episodes of cataplexy, hypnagogic hallucinations, and sleep paralysis. Stimulant drugs, such as Dexedrine and Ritalin, are also used to minimize narcoleptic symptoms. Dreams have fascinated people since the beginning of time. On average, about 25 percent of a night’s sleep, or almost two hours every night, is spent dreaming. So, assuming you live to a ripe old age, you’ll devote more than 50,000 hours, or about six years of your life, to dreaming.
Although dreams may be the most spectacular brain productions during sleep, they are not the most common. More prevalent is sleep thinking, which takes place during NREM sleep and consists of vague, uncreative, bland, and thoughtlike ruminations about real-life events (Hobson & Stickgold, 1995; Schatzman & Fenwick, 1994). For example, just before an important exam, students may review terms and concepts during NREM sleep.
In contrast to sleep thinking, a dream is an unfolding episode of mental images that is storylike, involving characters and events. According to sleep researcher J. Allan Hobson (1988), dreams have five basic characteristics:
· Emotions can be intense.
· Content and organization are usually illogical.
· Sensations are sometimes bizarre.
· Even bizarre details are uncritically accepted.
· Dream images are difficult to remember.
Many people believe that dreams occur only during REM sleep, but this is not the case. Dreams occur during both NREM and REM sleep (Rosenlicht & Feinberg, 1997). However, dreams during REM sleep are more frequent and of longer duration than are dreams during NREM sleep (Foulkes, 1997). When people are awakened during REM sleep, they will report a dream up to 90 percent of the time—even people who claim that they never dream. People usually have four or five episodes of dreaming each night. Earlymorning dreams, which can last as long as 40 minutes, are the dreams people are most likely to remember. Contrary to popular belief, dreams happen in real time, not in split seconds. In fact, dreamers tend to be quite accurate in estimating how long they’ve been dreaming (Empson, 1993).
The Brain During REM Sleep
What happens in the brain during REM sleep? Earlier in the chapter, we noted that EEG measurements show that the brain is highly active during REM sleep. In a recent series of PET scans of sleeping subjects, neuroscientist Allen Braun and his colleagues (1998) showed that the brain’s activity during REM sleep is distinctly different from its activity during either wakefulness or slow-wave (NREM) sleep. Braun found that both the primary visual cortex and the frontal lobes are essentially shut down during REM sleep. The primary visual cortex is the area at the back of the brain that first registers visual information transmitted by the retinas of the eye. The frontal lobes are the brain areas responsible for higher-level cognitive processes, including reasoning, planning, and integrating perceptual information. Thus, during REM sleep, the sleeper is cut off from information about the external world and from the brain centers most involved in rational thought. Other brain areas, however, are highly active during REM sleep. Activated areas include the amygdala and the hippocampus, structures of the limbic system that are involved in emotion, motivation, and memory. Also highly active are other parts of the brain’s visual system that are involved in generating visual images.
These results suggest that the dreamer’s uncritical acceptance of bizarre and chaotic dream images and narrative can be explained in terms of the inactivityof the frontal lobes—the very areas of the brain that are normally most active in analyzing and interpreting new information. In the absence of meaningful stimuli from the outside world, emotions and stored memories provide the raw data for the vivid visual images conjured up by the sleeping brain. Brain Changes During REM Sleep These PET scans reveal how brain activity during REM sleep differs from wakefulness (scan a) and slow-wave sleep (scan b). The PET scans are color-coded: Yellow-red indicates areas of increased brain activity, and bluish-purple indicates areas of decreased brain activity. Compared to wakefulness, scan (a) reveals that REM sleep involves decreased activity in the frontal lobes, which are involved in rational thinking, and the primary visual cortex, which processes external visual stimuli. The yellow-red areas indicate increased activity in visual areas associated with visual imagery—the images occurring in a dream. Compared to slow-wave sleep, the yellow-red areas in scan (b) indicate that REM sleep is characterized by a sharp increase in areas of the limbic system that are associated with emotion, motivation, and memory. The activation of these brain areas reflects the intense emotions that often characterize dreams. In combination, these two PET scans document the high degree of mental imagery and emotionality that takes place in the dreaming brain. But the brain changes that occur during REM sleep also show that the dreamer is cut off from the reality-testing functions of the frontal lobes—a fact that no doubt contributes to the sometimes bizarre nature of dreams.
REM Sleep and Memory Consolidation
As you’ll see in Chapter 6, memory consolidation refers to the gradual process of converting new memories into a long-term, relatively permanent form. Research suggests that REM sleep helps consolidate memories, especially procedural memories (Stickgold & others, 2001). Procedural memories are essentially memories for how to perform sequences of behaviors. For example, when you play a video game or the piano, you’re drawing on your procedural memories. Studies have shown that REM sleep increases after learning a novel task and that deprivation of REM sleep following training disrupts learning (Maquet, 2001). The importance of REM sleep was demonstrated in one study in which volunteers were trained on a simple but challenging perceptual task before going to sleep (Karni & others, 1994). Half the participants were repeatedly awakened during NREM sleep stages, while the other half were repeatedly awakened during REM sleep. The volunteers who enjoyed uninterrupted REM (dreaming) sleep improved their performance on the test the next day, but the participants whose REM sleep was disrupted did not. While REM sleep appears to play an important role in memory consolidation, exactly how it does so is still unknown. Recent studies have shown that brain areas activated during training on a particular task are actually reactivated during REM sleep (Louie & Wilson, 2001; Maquet & others, 2000). Thus, REM sleep may help stabilize the neural connections acquired through recent experience.
What Do We Dream About?
Although nearly everyone can remember an unusually bizarre dream, most dreams are a reflection of everyday life, including people we know and familiar settings (Domhoff, 1999; Weinstein & others, 1991). Recall Mike’s nightmare about his new boss, which was described in the Prologue. The giant staircase and spiral escalators were exaggerated versions of real architectural features of the atrium-style lobby of the hotel where he works. Dream researcher Calvin Hall collected and analyzed over 10,000 dreams from hundreds of people. He found that a dream’s themes often reflect the daily concerns of the dreamer (Hall & Van de Castle, 1966).Worries about exams, money, health, troubled relationships, or jobs are all likely to be reflected in our dreams—as was Mike’s anxiety about his new boss. Certain themes, such as falling, being chased, or being attacked, are surprisingly common across cultures. Although thousands of miles apart and immersed in two very different cultures, American and Japanese college students share many dream themes. Surveys of dream content in many cultures have shown that dreamers around the world report more instances of negative events than of positive events (Domhoff, 1996). Instances of aggression are more common than are instances of friendliness, and dreamers are more likely to be victims of aggression than aggressors in their dreams. There is more aggression in men’s dreams than in women’s dreams, but women are more likely to dream that they are the victims of physical aggression. Environmental cues during dreaming can also influence dream content. In sleep labs, researchers have played recordings of a rooster crowing, a bugle playing reveille, and a dog barking. Researchers have even sprayed water on sleeping subjects. Depending on the stimulus, up to half the dreamers incorporated the external stimulation into their dream content (Arkin & Antrobus, 1991).
Why Don’t We Remember Our Dreams?
Even the best dream recallers forget the vast majority of their dreams—at least 95 percent, according to one estimate (Hobson, 1995). Why are dreams so much more difficult to remember than waking experiences? Several theories have been proposed, each with at least some evidence to support it. As we’ll discuss in more detail in Chapter 6, memory requires information to be processed and stored in such a way that it can be retrieved at a later time. One theory is that the fundamental changes in brain chemistry and functioning that occur during sleep fail to support such information processing and storage. For example, frontal lobe areas are involved in the formation of new memories. But as you read earlier, PET scans of sleeping volunteers have shown that the frontal lobes are inactive during REM sleep (Braun & others, 1998). Research has also shown that the neurotransmitters needed to acquire new memories—including serotonin, norepinephrine, and dopamine—are greatly reduced during REM sleep (J. A. Hobson & others, 1998; Siegel, 2001). Some dreams are remembered, however, and several factors have been found to influence dream recall. First, you’re much more likely to recall a dream if you wake up during it (Schredl & Montasser, 1997).
When people are intentionally awakened during REM sleep, they usually recall the dream content. There are also individual differences in dream recall. Some people frequently remember their dreams in vivid detail. Other people hardly ever remember their dreams. Research has shown that people who are better at remembering visual details while awake are also better at recalling their dreams (Schredl & others, 1995). Second, the more vivid, bizarre, or emotionally intense a dream is, the more likely it is to be recalled the following morning. Vivid dreams are also more likely to be remembered days or weeks after the dream has occurred (Goodenough, 1991). In many respects, this is very similar to waking experiences. Whether you’re awake or asleep, mundane and routine experiences are most likely to be forgotten. Third, distractions on awakening interfere with our ability to recall dreams, as noted by psychologist Mary Calkins (1893) over a century ago: To recall a dream requires usually extreme and immediate attention to the content of the dream. Sometimes the slight movement of reaching for paper and pencil or of lighting one’s candle seems to dissipate the dream-memory, and one is left with the tantalizing consciousness of having lived through an interesting dream-experience of which one has not the faintest memory. Finally, it’s difficult to remember any experience that occurs during sleep, not just dreams. Sleep researchers have found that people who are briefly awakened during the night to give reports or perform simple tasks frequently do not remember the incident the next morning (Goodenough, 1991). It seems clear, then, that the brain is largely programmed to forget not only the vast majority of dream experiences but also other experiences that happen during sleep.
If I fall off a cliff in my dreams and don’t wake up before I hit the bottom, will I die? The first obvious problem with this bit of folklore is that if you did die before you woke up, how would anyone know what you’d been dreaming about? Beyond this basic contradiction, studies have shown that about a third of dreamers can recall a dream in which they died or were killed. Dream sensations such as falling, soaring through the air, and being paralyzed seem to be universal. Do animals dream? Virtually all mammals experience sleep cycles in which REM sleep alternates with slow-wave NREM sleep. Animals clearly demonstrate perception and memory. They also communicate using vocalizations, facial expressions, posture, and gestures to show territoriality and sexual receptiveness. Thus, it’s quite reasonable to conclude that the brain and other physiological changes that occur during animal REM sleep are coupled with mental images. One bit of anecdotal evidence supporting this idea involved a gorilla that had been taught sign language to communicate. The gorilla signed “sleep pictures,” presumably referring to REM dream activity while it slept. What do blind people “see” when they dream? People who become totally blind before the age of five typically do not have visual dreams as adults. Even so, their dreams are just as complex and vivid as sighted people’s dreams; they just involve other sensations—of sound, taste, smell, and touch. Is it possible to control your dreams? Yes, if you have lucid dreams. A lucid dream is one in which you become aware that you are dreaming while you are still asleep. About half of all people can recall at least one lucid dream, and some people frequently have lucid dreams. The dreamer can often consciously guide the course of a lucid dream, including backing it up and making it go in a different direction. Can you predict the future with your dreams? History is filled with stories of dream prophecies. Over the course of your life, you will have over 100,000 dreams. Simply by chance, it’s not surprising that every now and then a dream contains elements that coincide with future events. Are dreams in color or black and white? Up to 80 percent of our dreams contain color. When dreamers are awakened and asked to match dream colors to standard color charts, soft pastel colors are frequently chosen.
Nightmares
An unpleasant anxiety dream that occurs during REM sleep is called a nightmare. Nightmares often produce spontaneous awakenings, during which the vivid and frightening dream content is immediately recalled. The general theme of nightmares is of being helpless or powerless in the face of great danger or destruction. Nightmares are especially common in young children (Halliday, 1995). For example, when our daughter Laura was four years old, she told us about this vivid nightmare: There was a big monster chasing me and Nubbin the Cat! And we jumped on a golden horse but the monster kept chasing us! Then Nubbin jumped off and started to eat the monster. And then Mommy came and saved me! And then Daddy took a sword and killed the monster! And then me and Mommy and Nubbin rode the horse into the clouds. Like Laura, young children often have nightmares in which they are attacked by an animal or monster. In dealing with a child who has experienced a nightmare, simple reassurance is a good first step, followed by an attempt to help the child understand the difference between an imaginary dream and a real waking experience. In adults, an occasional nightmare is a natural and relatively common experience (Wood & Bootzin, 1990). Nightmares are not considered indicative of a
psychological or sleep disorder unless they frequently cause personal distress. Sigmund Freud: Dreams as Fulfilled Wishes In the chapters on personality and psychotherapy. Freud believed that sexual and aggressive instincts are the motivating forces that dictate human behavior. Because these instinctual urges are so consciously unacceptable, sexual and aggressive thoughts, feelings, and wishes are pushed into the unconscious, or repressed. However, Freud believed that these repressed urges and wishes could surface in dreams. In his landmark work, The Interpretation of Dreams (1900), Freud wrote that dreams are the “disguised fulfillments of repressed wishes” and provide “the royal road to a knowledge of the unconscious mind.” Freud believed that dreams function as a sort of psychological “safety valve” for the release of unconscious and unacceptable urges.
Freud (1904) believed that dreams have two components: the manifest content, or the dream images themselves, and the latent content, the disguised psychological meaning of the dream. For example, Freud (1911) believed that dream images of sticks, swords, and other elongated objects were phallic symbols, representing the penis. Dream images of cupboards, boxes, and ovens supposedly symbolized the vagina.
In many types of psychotherapy today, especially those that follow Freud’s ideas, dreams are still seen as an important source of information about psychological conflicts. However, Freud’s belief that dreams represent the fulfillment of repressed wishes has not been substantiated by psychological research (Fisher & Greenberg, 1996; Schatzman & Fenwick, 1994). Furthermore, research does not support Freud’s belief that the dream images themselves—the manifest content of dreams—are symbols that disguise the dream’s true psychological meaning (Domhoff, 1996).
The Activation–Synthesis Model of Dreaming Armed with an array of evidence that dreaming involves the activation of different brain areas during REM sleep, researcher J. Allan Hobson and his colleague Robert McCarley first proposed a new model of dreaming in 1977. Called the activation–synthesis model of dreaming, this model maintains that dreaming is our subjective awareness of the brain’s internally generated signals during sleep (Hobson, 1995; Hobson & Stickgold, 1995). Since it was first proposed, the model has evolved as new findings have been reported (Hobson & others, 1998; Stickgold & others, 2001).
Specifically, the activation–synthesis model maintains that the experience of dreaming sleep is due to the automatic activation of brainstem circuits at the base of the brain. These circuits arouse more sophisticated brain areas, including visual and auditory pathways. As noted earlier, limbic system structures involved in emotion, such as the amygdala and hippocampus, are also activated during REM sleep. When we’re awake, these pathways and brain structures are involved in registering stimuli from the external world. But rather than responding to stimulation from the external environment, the dreaming brain is responding to its own internally generated signals. In the absence of external sensory input, the activated brain combines, or synthesizes, these internally generated sensory signals and imposes meaning on them. The dream story itself is derived from a hodgepodge of memories, emotions, and sensations that are triggered by the brain’s activation and chemical changes during sleep. According to this model, then, dreaming is essentially the brain’s synthesizing and integrating memory fragments, emotions, and sensations
that are internally triggered (Hobson & others, 1998).
The activation–synthesis theory does not state that dreams are completely meaningless (Hobson & Stickgold, 1995). But if there is a meaning to dreams, that meaning lies in the deeply personal way in which the images are organized, or synthesized. In other words, the meaning is to be found not by decoding the dream symbols, but by analyzing the way the dreamer makes sense of the progression of chaotic dream images.
Some Observations About the Meaning of Dreams
Subjectively, it seems obvious that at least some of our dreams mirror our real life concerns, frustrations, anxieties, and desires. Less subjectively, this observation is consistent with sleep research on the content of dreams (Weinstein & others, 1991). Large-scale analyses of dream reports demonstrate that dreams reflect the waking concerns and preoccupations of the dreamer (Domhoff, 1993, 1996). Thus, the topics you think about during the day are most likely to influence the topics you dream about at night (Nikles & others, 1998). Some dream researchers believe that most dreams, however chaotic or disorganized, are meaningfully related to the dreamers’ current concerns, problems, and waking lives (Domhoff, 1998).
It may well be that the more bizarre aspects of dream sequences—the sudden scene changes, intense emotions, and vivid, unrealistic images—are due to physiological changes in the brain during REM and NREM sleep. Dream researcher David Foulkes (1993, 1997) argues that dreaming consciousness is no different from waking consciousness in its attempt to make sense of the information that is available to it. What differs is the source of the information. When we’re awake, we monitor the external environment, making sense of the stimuli that impinge upon us from the environment as well as our own thoughts, feelings, and fantasies. During sleep, we try—as best we can—to make sense of the less orderly stimuli produced by the brain itself. If nothing else, remember that the interpretation of dreams occurs when we’re awake. It seems reasonable, then, to suggest that conscious speculations about the meaning of these elusive nightly productions might reveal more about the psychological characteristics of the interpreter than about the dream itself (Cartwright & Kaszniak, 1991).
changes in perception, memory, thoughts, and behavior (American Psychological Association, 2001). For many people the word hypnosis conjures up the classic but sinister image of a hypnotist inducing hypnosis by slowly swinging a pocket watch back and forth. But, as psychologist John Kihlstrom (2001) explains, “The hypnotist does not hypnotize the individual. Rather, the hypnotist serves as a sort of coach or tutor whose job is to help the person become hypnotized.” After experiencing hypnosis, some people are able to self-induce hypnosis. The word hypnosis is derived from the Greek hypnos, meaning “sleep.” The idea that the hypnotized person is in a sleep-like trance is still very popular among the general public. However, the phrase hypnotic trance is misleading and rarely used by researchers today (Wagstaff, 1999). When hypnotized, people do not lose control of their behavior. Instead, they typically remain aware of where they are, who they are, and what is transpiring.
Rather than being a sleeplike trance, hypnosis is characterized by highly focused attention, increased responsiveness to suggestions, vivid images and fantasies, and a willingness to accept distortions of logic or reality. During hypnosis, the person temporarily suspends her sense of initiative and voluntarily accepts and follows the hypnotist’s instructions (Hilgard, 1986a).
Although most adults are moderately hypnotizable, people vary in their responsiveness to hypnotic suggestions. About 15 percent of adults are highly susceptible to hypnosis, and 10 percent are difficult or impossible to hypnotize (Hilgard, 1982; Register & Kihlstrom, 1986). Children tend to be more responsive to hypnosis than are adults, and children as young as five years old can be hypnotized (Kohen & Olness, 1993). Evidence suggests that the degree of susceptibility to hypnosis tends to run in families. For example, identical twins are more similar in their susceptibility to hypnosis than are fraternal twins (Nash, 2001).
The best candidates for hypnosis are individuals who approach the experience with positive, receptive attitudes. The expectation that you will be responsive to hypnosis also plays an important role (Kirsch & others, 1995; Spanos & others, 1993). People who are highly susceptible to hypnosis have the ability to become deeply absorbed in fantasy and imaginary experience. For instance, they easily become absorbed in reading fiction, watching movies, and listening to music (Barnier & McConkey, 1999; Kihlstrom, 2001).
Effects of Hypnosis
Deeply hypnotized subjects sometimes experience profound changes in their subjective experience of consciousness. They may report feelings of detachment from their bodies, profound relaxation, or sensations of timelessness. More commonly, hypnotized people converse normally and remain fully aware of their surroundings. Often, they will later report that carrying out the hypnotist’s suggestions seemed to happen by itself. The action seems to take place outside the hypnotized person’s will or volition.
Sensory and Perceptual Changes
Some of the most dramatic effects that can be produced with hypnosis are alterations in sensation and perception. Sensory changes that can be induced through hypnosis include temporary blindness, deafness, or a complete loss of sensation in some part of the body (Hilgard, 1986a). For example, when the suggestion is made to a highly responsive subject that her arm is numb and cannot feel pain, she will not consciously experience the pain of a pinprick or of having her arm immersed in ice water. This property of hypnosis has led to its use as a technique in pain control (Montgomery & others, 2000). Painful dental and medical procedures, including surgery, have been successfully performed with hypnosis as the only anesthesia (Hilgard & others, 1994).
People can experience hallucinations under hypnosis. If a highly responsive hypnotic subject is told that a close friend is sitting in a chair on the other side of the room, she will not only report seeing the friend in vivid detail but will walk over and “touch” the other person. Under hypnosis, people can also not perceive something that is there. For example, if the suggestion is made that a jar of rotten eggs has no smell, a highly suggestible person will not consciously perceive any odor. Hypnosis can also influence behavior outside the hypnotic state.
When a posthypnotic suggestion is given, the person will carry out that specific suggestion after the hypnotic session is over. For example, under hypnosis, a student was given the posthypnotic suggestion that the number 5 no longer existed. He was brought out of hypnosis and then asked to count his fingers. He counted 11 fingers! Counting again, the baffled young man was at a loss to explain his results.
Some posthypnotic suggestions
have been reported to last for months, but most last only a few hours or days (Barnier & McConkey, 1998). So, even if the hypnotist does not include some posthypnotic signal to cancel the posthypnotic suggestion, the suggestion will eventually wear off.
