CENTER ON BEHAVIORAL MEDICINE
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Effects of Sleep Deprivation on the Mind/Body Connection
James H. Farmer III
During sleep, we usually pass through five phases of sleep: stages 1,2,3,4, and REM sleep. These stages progress in a cycle from stage 1 to REM sleep, then the cycle starts over again with stage 1. We spend almost fifty percent of our total sleep time in stage 2 sleep, and about twenty percent in REM sleep, and the remaining thirty percent in the other stages (Society for Neuroscience, 1994).
Since sleep and wakefulness are influenced by different neurotransmitter signals in the brain, foods and medicines that change the balance of these signals affect whether we feel alert or drowsy and how well we sleep. Caffeinated drinks such as coffee and drugs such as diet pills and decongestants stimulate some parts of the brain and can cause insomnia, or an inability to sleep. Many antidepressants suppress REM sleep. Heavy smokers often sleep very lightly and have reduced amounts of REM sleep. They also tend to wake up after 3 or 4 hours of sleep due to nicotine withdrawal. Many people who suffer from insomnia try to solve the problem with alcohol. While alcohol does help people fall into light sleep, it also robs them of REM and the deeper, more restorative stages of sleep.
People lose some of the ability to regulate their body temperature during REM, so abnormally hot or cold temperatures in the environment can disrupt this stage of sleep. If our REM is disrupted one night, our bodies don't follow the normal sleep cycle progression the next time we doze off. Instead, we often slip directly into REM sleep and go through extended periods of REM until we "catch up" on this stage of sleep.
Many studies make it clear that sleep deprivation is dangerous. Sleep-deprived people who are tested by using a driving simulator or by performing a hand-eye coordination task perform as badly as or worse than those who are intoxicated. Sleep deprivation also magnifies alcohol's effects on the body, so a fatigued person who drinks will become much more impaired than someone who is well-rested.
Sleep also is necessary for our nervous systems to work properly. Too little sleep leaves us drowsy and unable to concentrate the next day. It also leads to impaired memory and physical performance and reduce ability to carry out math calculations. If sleep deprivation continues, hallucinations and mood swings may develop. Some experts believe sleep gives neurons used while we are awake a chance to shut down and repair themselves. Without sleep, neurons may become so depleted in energy or so polluted with by-products of normal cellular activities that they begin to malfunction. Sleep also may give the brain a chance to exercise important neuronal connections that might otherwise deteriorate from lack of activity (Columbus Sleep Consultants, 1994).
Deep sleep coincides with the release of growth hormone in children and young adults. Many of the body's cells also show increased production and reduced breakdown of proteins during deep sleep. Since proteins are the building blocks needed for cell growth and for repair of damage from factors like stress and ultraviolet rays, deep sleep may really be considered "beauty rest". Activity in parts of the brain that control emotions, decision-making processes, and social interactions is drastically reduced during deep sleep, suggesting that this type of sleep may help people maintain optimal emotional and social functioning while they are awake. People with sleep deprivation tend to have more emotional and mental problems, which may be related to their sleeping problem.
Sleep and sleep-related problems play a role in a large number of human disorders and affect almost every field of medicine. Sleeping problems occur in almost all people with mental disorders, including those with depression and schizophrenia. People with depression, for example, often awaken in the early hours of the morning and find themselves unable to get back to sleep. The amount of sleep a person gets also strongly influences the symptoms of mental disorders. Sleep deprivation is an effective therapy for people with certain types of depression, while it can actually cause depression in other people. Extreme sleep deprivation can lead to a seemingly psychotic state of paranoia and hallucinations in otherwise healthy people, and disrupted sleep can trigger episodes of mania in people with manic depression (University of Wisconsin, 2001).
In an experiment involving 100 hours of deprivation in 17 different human participants, one of the prominent changes in mood was an increase in irritability. This change in affect has been observed in animals as well. In one experiment, dogs were found to be hyper-irritable when sleep deprived. Sleep deprived rats displayed both irritability and aggressive behavior. One experiment in which human participants underwent 72 hours of sleep deprivation found extreme changes in mood during the deprivation period. These included giddiness and uninhibited and unprovoked laughter, as well as feelings of depression. One experiment reported loss of control of anger and an argumentative demeanor (Smith, Hurd, Cracraft, Hyslop, Zgheib, Hoffert, 1997). Tests used for evaluating the effects of sleep deprivation were those such as: Walter-Reed, Temporal Disorientation Scale, Visual Misperception Scale, and Vigilance Testing (Wilkinson, 1968).
Some of the subtle and most profound effects of sleep involve some aspect of cognition. One experimenter distinguished between three types of psychological changes during sleep deprivation. These include psychoneurotic-like, schizophrenic-like, and paranoid-like reactions. Each of these reactions includes a number of sub-systems. Psychoneurotic-like reactions include anxiety, psychomotor complaints, and irritation. Schizophrenic-like reactions include illusions, delusions, and hallucinations, disturbances in thinking, and unprovoked emotion, such as laughter. These types of reactions are some of the most commonly reported experience during extended periods of sleep loss. Visual hallucinations have been observed in other experiments as well. Examples of these include the perception of tile squares to be pulsating and growing darker and larger, mistaking a desk for a water fountain, and the floor of the lab "appearing to be covered by a layer of shimmering water". The frequency of these hallucinations may increase with sleep deprivation. A number of stages of visual hallucinations have been identified. These include identifying a disturbed perception, labeling a hallucination with no doubt as to its reality, labeling a hallucination with doubt as to its reality, and labeling and believing in a misperception. It has been suggested that visual hallucinations during sleep deprivation are centrally caused due to stress on the eyes. This is consistent with the finding that visual acuity is unimpaired during sleep deprivation. It has been suggested that the visual hallucinations during sleep deprivation are actually hypnogogic hallucinations that occur in the micro-sleeps of attention lapses. Hypnogogic hallucinations are dream-like thoughts that occur at sleep onset (MacAlester College, 2001).
Disturbances in thought are another common experience in sleep-deprived individuals. These include such things as loss of memory for recent events that occurred during the period of extended wakefulness, rambling and garrulous speech, lack of coherent logical structure in thought and speech, and difficulty answering questions. In one experiment, memorization tasks that required about 100 seconds to perform after a night of recovery required 20 minutes to complete only 1/3 of the task during the advanced stages of sleep deprivation. In another instance, the task was not completed at all, and was abandoned. It should be noted here that a confounding variable in such tasks is the participants inability to pay attention to the task long enough to perform. It may not be that memory, per se, is impaired. Rather, a short attention span may inhibit the concentration required for memorization. However, other experiments have demonstrated that memory for things that had just occurred can be impaired. In addition, though this memory deterioration is recognizable at 72 hours of continual wakefulness, at 96 hours of wakefulness the deterioration is marked.
Impairment of a coherent logical structure in thought and speech is another prominent symptom of sleep deprivation. Cognitive disorganization is apparent. The focus of this organization is the inability to sustain a continuous mental operation. Sleep deprived individuals may demonstrate difficulty in thinking of words, correctable mistakes in thought and speech, losing one's train of thought, and incoherence of thought and speech. Other experiments report participants experiencing confusion and irrationality. Similar findings of spatial and temporal disorientation have also been reported. Temporal organization has been measured by a person's ability to estimate a period of time. Mistakes in time judgement increased with degree of sleep deprivation. Mistakes in time judgement were made in the direction of the study being complete. One experimenter reported that sleep deprived subjects had difficulty forming and expressing thoughts in a coherent manner, and demonstrated general confusion particularly in conversation. It is interesting to note that the former experiment no impairment was evident during formal psychological testing, but when the participant was not under the pressure of a cognitive test, he or she felt and behaved in an impaired manner. Another author suggested that the subtle higher functions of organization and synthesis or mental life appeared to be effected. A third type of psychological deficit that sleep deprivation instigates is paranoid reactions. These include symptoms of acute schizophrenia, such as delusions of grandeur and persecution, hallucinations, and unprovoked aggression. Other symptoms in this category include some types of psychotic behavior, personality changes, and other dream-like mental experiences that are inconsistent with the waking state. Other studies have confirmed these reports of paranoid delusions, some of persecution, as well as defensiveness. Thought disturbances during sleep deprivation, in conjunction with spontaneous laughter and postural abnormalities, have been observed to occur in waves, interspersed by periods of apparently normal behaviors (Home, 1989).
In the last few years, mental health professionals have asked whether sleep deprivation plays a role in the increase in cases of depression reported on campuses. According to a study by psychologists at Kansas State University and published in February in Professional Psychology, the number of college-age students treated for depression has doubled since 1989. The study involved more than 10,000 students at more than 100 colleges. That incidence is twice the rate for the general population: one in 10 men and one in four women will have clinical depressive episode in their lifetimes. Since 1989, the number of college students consulting doctors for sleep problems increased even more, some experts say. Dr. Roseanne Armitage, director of the Sleep and Chronophysiology Laboratory at the University of Michigan Depression Center states, "there is no question that college kids are sleeping less than they used to". Last year, college students averaged 6 to 6.9 hours of sleep a night, far less than the suggested 8 to 9.25 and down from 7 to 7.5 in the 1980's.
Psychologists are not certain whether sleep problems are a potential cause or a symptom of depression. Treating depression with antidepressants is not always as effective for sleep problems as for other symptoms. Some medications like the widely prescribed selective serotonin reuptake inhibitors can actually cause insomnia. Many experts have even succeeded with patients with severe depression for short periods by depriving them of sleep. The role of sleep disturbances in depression has, become very interesting to neuroscience since a study from the National Institute of Mental Health in 1989 reported that sleep disturbances lasting longer than two weeks increased the risk of developing many psychiatric illnesses, especially depression. One analogy that they use would be having a high serum cholesterol and the risk of heart attacks. Just because you have a high cholesterol level does not necessarily mean that you are definitely going to have a heart attack. But it is a definite risk factor. The same could be said for sleep disturbances and the risk of developing depression.
Dr. John F. Greden, chairman of the psychiatry department at the University of Michigan, said: "We have pretty good evidence that staying up late all night and then trying to catch up with an erratic schedule of naps quickly creates a situation called delayed sleep phase insomnia. This is detrimental for mood regulation". Many students stay up until 3 a.m., sleep until 1 p.m., try to catch up with a nap and then do it again night after night. But getting back on schedule for 8 or 9 a.m. classes is difficult. The student's sleep is perpetually disrupted, as if they had jet lag, and especially for those with a vulnerability to depression, the patterns are highly likely to be a risk factor.
Sleep deprivation is a commonplace occurrence in modern culture. Every day there seems to be twice as much work and half as much time to complete it in. This results in either extended periods of wakefulness or a decrease in sleep over an extended period of time. While some people may like to believe that they can train their bodies to not require as much sleep as they once did, is a false belief. Sleep is needed to regenerate certain parts of the body, especially the brain, so that it may continue to function optimally. After periods of extended wakefulness or reduced sleep neurons may begin to malfunction, visibly effecting a person's behavior. Some organs, such as muscles, are able to regenerate even when a person is not sleeping so long as they are resting. This could involve lying awake but relaxed within a quite environment. Even though cognitive functions might not seem necessary in this scenario the brain, especially the cerebral cortex, is not able to rest but rather remains semi-alert in a state of quiet readiness. Certain stages of sleep are needed for the regeneration of neurons within the cerebral cortex while other stages of sleep seem to be used for forming new memories and generating new synaptic connections. The effects of sleep deprivation on deprivation on behavior have been tested with relation to the presence of activity in different sections of the cerebral cortex. The temporal lobe of the cerebral cortex is associated with the processing of language. During verbal learning tests on subjects who are fully rested functional magnetic resonance imaging scans show that this area of the brain is very active. However, in sleep deprived subjects there is no activity within this region. The effects of this inactivity can be observed by the slurred speech in subjects who have gone for prolonged periods with no sleep. Even severely deprived people are still able to perform to some degree on a verbal learning test. This implies that some other area of the brain must become active to compensate for the loss of temporal lobe functioning. In fact, activity can be seen in the parietal lobe that is not present during verbal learning tests using rested subjects. Greater activity within this region corresponded to better performance by subjects in research studies. Still, sleep deprived people do not perform as well on these tests as do fully rested subjects. One possible reason for the poorer performance after missing sleep, aside from un-regenerated neurons, could be the fact that since the parietal lobe is not usually used to performing tasks such as these it is not as adept at carrying them out. Therefore, when control switches from the temporal lobe to the parietal lobe some speed and accuracy is naturally lost. Interestingly, sleep deprived subjects have been shown to have better short-term memory abilities than their well-rested counterparts. Since memory is associated with this region of the cerebral cortex the fact that it is already active in sleep deprived people could make it easier for new synapses to be created, thus forming new short-term memories more easily (Leproult et al., 1997). While activity is seen within the parietal lobes of rested people as they think through math problems no corresponding activity is visible within the brains of sleep-deprived subjects. Also, no new area of the brain becomes active while the sleep deprived people work on math problems. Since sleep deprived people can still complete math problems, even though with less speed and accuracy than a well-rested individual, this data implies that a region of the brain already in use is used for this task (Bonnet, 1986).
The frontal lobe is the most interesting section of the brain with relation to sleep deprivation. Its functions are associated with speech as well as novel and creative thinking. Sleep deprived test subjects have difficulties thinking of imaginative words or ideas. Instead, they tend to choose repetitious words or clichéd phrases. Also, a sleep-deprived individual is less able to deliver a statement well. The subject may show signs of slurred speech, stuttering, speaking in a monotone voice, or speaking at a slower pace than usual. Subjects in research studies also have a more difficult time reacting well to unpredicted rapid changes. Sleep deprived people do not have the speed or creative abilities to cope with making quick but logical decisions, nor do they have the ability to implement them well. Studies have demonstrated that a lack of sleep impairs one's ability to simultaneously focus on several different related tasks, reducing the speed as well as the efficiency of one's actions. A person may be able to react to a complex scenario when suddenly presented with but, similar to the verbal tests, the subject will most likely pick an unoriginal solution. If presented with a similar situation multiple times with slight variations in the information presented the subject chooses the same solution, even though it might not be as applicable to the new scenario (Cardinal,1998).
Part of the frontal lobe, the pre-frontal cortex, has several functions specifically coupled with it. Judgement, impulse, control, attention, and visual association have all bee related to this region of the cerebral cortex. A recent study has shown that the prefrontal cortex, usually the most active area of the brain in rested individuals, becomes more active as a person remains awaked for long periods of time. This region regenerates during the first stage of sleep, giving a person the ability to feel somewhat refreshed after only a short nap. The length of the first stage of sleep cycle is somewhat dependant upon how long the person had previously been awake. The longer the period of wakefulness, the longer the brain remains in the first stage of sleep. When the brain enters into the REM stage of sleep, the pre-frontal cortex is active once more. The implications of this data seem to be fairly important in supporting the location of the I-function within the brain. The pre-frontal cortex is active whenever a person is awake, no matter how little sleep they have had. Also, this area is active while dreaming. Since the individual is aware of him or herself during both of these instances, but is not aware during the stages of sleep when the pre-frontal cortex is shut down, it seems that the I-function is located within this region. This indicates that the I-function is what is resting and regenerating during the first stage of sleep. It would be interesting to study pre-frontal cortex activity while a person is conscious, but unaware of his or her actions, due to an influence such as drugs or alcohol.
One of the symptoms of prolonged sleep deprivation is hallucinations. This could also be related to the I-function since it is the system that integrates the input from all other areas of the brain. If the neurons composing the I-function become too taxed then the picture in the head that the I-function produces may be more dissimilar from reality than usual. The neurons, under pressure to continue functioning but unable to perform optimally, create an image useful enough for a person to see most of his or her surroundings. Metabolic activity in the prefrontal cortex can drop as much as eleven percent after a person has missed sleep for only twenty four hours. As a person loses more sleep or continues to receive less than adequate amounts of sleep the neurons become even more taxed and the I-function may begin to generate even less coherent images possibly resulting in temporary insanity (McCann et al, 1992).
Another piece of evidence supporting the location of the I-function is that mammals have REM sleep whereas cold-blooded animals do not and mammals have a neocortex, located within the pre-frontal cortex, while cold-blooded animals do not. REM sleep stimulates areas of the brain used for learning and memory. When a person is taught a new skill his or her performance does not improve until he or she receives at least eight hours of sleep. An extended period of sleep ensures that the brain will be able to complete the full sleep cycle, including REM sleep. The necessity of sleep for learning could be due to the fact that sleep increases the production of proteins while reducing the rate at which they are broken down. Proteins are used to regenerate the neurons within the brain. Without them new synapses may not be able to be formed, thus limiting the amount of information a sleep-deprived individual can maintain (Tsai et al, 1994).
In a way sleep deprivation studies help us to study the relationship between the brain and behavior in a very unique way by observing how a person's behavior changes as the brain shuts down. By taking images of the showing where activity is located it is possible to correlate the behavior exhibited by a subject with his or her brain patterns. Just like a person cannot jog for three continuous days a person's brain cannot operate without rest breaks. Since different regions of the brain rest during different stages of the sleep cycle, sleep cannot be cut short. Without sleep our brains deteriorate, and if the argument that brain equals behavior is true, then our behavior will also suffer accordingly.
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