Dreaming
Dreaming
The demonstrably necessary phenomenon of dreaming would suffice to prove the importance of sleep to humans, and perhaps to other animals as well. Dreaming involves an involuntary conjuring up of sometimes magical images in a story-like sequence in which the sleeper/dreamer is usually more a participant than an observer. Most scientists agree that dreaming is stimulated by the pons and occurs during the REM phase of sleep.
Many functions have been hypothesized for dreaming. Freud postulated that dreams are the symbolic expression of frustrated desires that had been relegated to the subconsciousness, and used dream interpretation in the form of psychoanalysis he pioneered. Scientists today have become more skeptical about details of Freudian interpretation, and place more emphasis on dreaming as a requirement for organization and consolidation of recent memory and experience. Another theory is that dreaming allows an animal to play out scenarios that may help the animal avoid dangers when awake. For example, a rabbit might dream about being cornered by a lion and may play out different scenarios that might increase chances of survival should he come across a lion in reality.
Sleep deprivationMain article: sleep deprivation Failure to sleep results in progressively severe psychological and physical distress. In 1965, California teenager Randy Gardner attempted to resist sleep in an uncontrolled "experiment". As his ordeal progressed he fell into a silent stupor, bringing into doubt whether he was actually awake in any practical sense. There are occasional stories of people who are able to function with a small or no amount of sleep, in many cases due to brain damage brought on by an accident, but these cases do not appear to hold up under controlled conditions.
A study at the University of Pittsburgh School of Medicine showed that poor sleep and sleep deprivation in older adults can lead to earlier death, but another survey of more than a million people in the 1980s found that those who slept more than seven and a half hours tended to die a little earlier. It is difficult to perform such studies as controlled experiments, since persons with various physical and psychological problems may be inclined to sleep longer as a result of these illnesses. Long sleepers do tend to have a higher than average rate of sleep disorders, possibly artificially increasing their reported sleep time, and providing a statistical selection effect that undermines the validity of many such studies.
A 1999 University of Chicago team led by Eve Van Cauter limited a group of lean young men to four hours of sleep for 16 days. The subjects showed decreased levels of leptin and increased levels of cortisol. The subjects also increased their daily caloric intake by 1,000 calories. The team discovered that the subjects' insulin and blood sugar levels resembled the impaired glucose tolerance of prediabetics, an indication that they were no longer properly processing carbohydrates. Studies have also linked sleep deprivation to an increased incidence of obesity.
At Harvard Medical School, researchers have identified associations between sleep deprivation and illnesses ranging from hypertension and heart attacks to cancer. Poor sleepers generate increased levels of stress hormones and show more inflammatory changes in the walls of their small blood vessels, both of which contribute to elevated blood pressure. Because of their exposure to light at night, night-shift workers produce less melatonin, a hormone which not only promotes sleep but has been shown to have cancer-prevention benefits as well.
Despite the risks, sleeping less is attractive to some because of the additional time made available, and many people feel they have to sleep less to maintain their lifestyle. They may resort to trying polyphasic sleep, a method for minimizing the time spent asleep, while maximizing its effects. This is done by sleeping in short naps throughout the day, minimizing the time spent awake between each period of sleep and thus decreasing the workload of the brain while sleeping. People who take so-called power naps during the day are practicing a variation of polyphasic sleeping. In this regard, cultures where the siesta is customary are also taking advantage of alternative means of obtaining sufficient sleep.
Experiments with rats have been designed to measure the effects of severe sleep deprivation. In one, a pair of rats were placed on a platform, separated by a movable wall. Both were instrumented with electroencephalograms. Whenever the "subject" rat began to show signs of sleep the partition was moved, forcing both rats to move. The "control" rat, however, could sleep in between movements. After several weeks the "subject" rat became unable to regulate body temperature; even if allowed to sleep at this point, it died shortly afterward from septic shock.
Some recent studies concluded the cause of death in the rat experiments to be more closely related to REM deprivation, but also found the rats died in about a week less time. It is believed this is because, unlike non-REM sleep that repairs parts of the brain damaged by metabolism and free radicals, REM sleep repairs the repair center. It is unclear the degree to which the results of sleep deprivation in rats can be generalized to humans.
In sleep-deprived states less extreme than that suffered by Randy Gardner, humans display irritability, impaired cognitive function, and poor judgment. Experiments on sleep-deprived medical trainees, for example, have shown them less able to interpret EKGs and x-rays than their well rested peers. As late as early 21st century people thought that too little sleep could be negated by "paying back the sleep debt". However, recent studies have shown this to be false. After extensively prolonged period of awareness, average humans can sleep comfortably for as long as 14 hours in row, but any amount over that has no effect for health. Sleeping over it causes dizziness, lack of muscular control, numbness and several other symptoms often confronted with too little sleep.
That one major function of sleep is consolidation and optimization of memories (including "unlearning") is evidenced by studies showing that mental functions are impaired by sleep deprivation and that sleep deprivation can even be lethal. Adequate rest and a properly functioning immune system are closely related. Sleep deprivation compromises the immune system by altering the blood levels of specialized immune cells and important proteins called cytokines, resulting in an increased chance of infection. We may begin to understand why sleep deprivation is lethal if we understand sleep as a necessary period of anabolic activity for all animals, and the basic need for anabolic activity as a prerequisite for life itself
The demonstrably necessary phenomenon of dreaming would suffice to prove the importance of sleep to humans, and perhaps to other animals as well. Dreaming involves an involuntary conjuring up of sometimes magical images in a story-like sequence in which the sleeper/dreamer is usually more a participant than an observer. Most scientists agree that dreaming is stimulated by the pons and occurs during the REM phase of sleep.
Many functions have been hypothesized for dreaming. Freud postulated that dreams are the symbolic expression of frustrated desires that had been relegated to the subconsciousness, and used dream interpretation in the form of psychoanalysis he pioneered. Scientists today have become more skeptical about details of Freudian interpretation, and place more emphasis on dreaming as a requirement for organization and consolidation of recent memory and experience. Another theory is that dreaming allows an animal to play out scenarios that may help the animal avoid dangers when awake. For example, a rabbit might dream about being cornered by a lion and may play out different scenarios that might increase chances of survival should he come across a lion in reality.
Sleep deprivationMain article: sleep deprivation Failure to sleep results in progressively severe psychological and physical distress. In 1965, California teenager Randy Gardner attempted to resist sleep in an uncontrolled "experiment". As his ordeal progressed he fell into a silent stupor, bringing into doubt whether he was actually awake in any practical sense. There are occasional stories of people who are able to function with a small or no amount of sleep, in many cases due to brain damage brought on by an accident, but these cases do not appear to hold up under controlled conditions.
A study at the University of Pittsburgh School of Medicine showed that poor sleep and sleep deprivation in older adults can lead to earlier death, but another survey of more than a million people in the 1980s found that those who slept more than seven and a half hours tended to die a little earlier. It is difficult to perform such studies as controlled experiments, since persons with various physical and psychological problems may be inclined to sleep longer as a result of these illnesses. Long sleepers do tend to have a higher than average rate of sleep disorders, possibly artificially increasing their reported sleep time, and providing a statistical selection effect that undermines the validity of many such studies.
A 1999 University of Chicago team led by Eve Van Cauter limited a group of lean young men to four hours of sleep for 16 days. The subjects showed decreased levels of leptin and increased levels of cortisol. The subjects also increased their daily caloric intake by 1,000 calories. The team discovered that the subjects' insulin and blood sugar levels resembled the impaired glucose tolerance of prediabetics, an indication that they were no longer properly processing carbohydrates. Studies have also linked sleep deprivation to an increased incidence of obesity.
At Harvard Medical School, researchers have identified associations between sleep deprivation and illnesses ranging from hypertension and heart attacks to cancer. Poor sleepers generate increased levels of stress hormones and show more inflammatory changes in the walls of their small blood vessels, both of which contribute to elevated blood pressure. Because of their exposure to light at night, night-shift workers produce less melatonin, a hormone which not only promotes sleep but has been shown to have cancer-prevention benefits as well.
Despite the risks, sleeping less is attractive to some because of the additional time made available, and many people feel they have to sleep less to maintain their lifestyle. They may resort to trying polyphasic sleep, a method for minimizing the time spent asleep, while maximizing its effects. This is done by sleeping in short naps throughout the day, minimizing the time spent awake between each period of sleep and thus decreasing the workload of the brain while sleeping. People who take so-called power naps during the day are practicing a variation of polyphasic sleeping. In this regard, cultures where the siesta is customary are also taking advantage of alternative means of obtaining sufficient sleep.
Experiments with rats have been designed to measure the effects of severe sleep deprivation. In one, a pair of rats were placed on a platform, separated by a movable wall. Both were instrumented with electroencephalograms. Whenever the "subject" rat began to show signs of sleep the partition was moved, forcing both rats to move. The "control" rat, however, could sleep in between movements. After several weeks the "subject" rat became unable to regulate body temperature; even if allowed to sleep at this point, it died shortly afterward from septic shock.
Some recent studies concluded the cause of death in the rat experiments to be more closely related to REM deprivation, but also found the rats died in about a week less time. It is believed this is because, unlike non-REM sleep that repairs parts of the brain damaged by metabolism and free radicals, REM sleep repairs the repair center. It is unclear the degree to which the results of sleep deprivation in rats can be generalized to humans.
In sleep-deprived states less extreme than that suffered by Randy Gardner, humans display irritability, impaired cognitive function, and poor judgment. Experiments on sleep-deprived medical trainees, for example, have shown them less able to interpret EKGs and x-rays than their well rested peers. As late as early 21st century people thought that too little sleep could be negated by "paying back the sleep debt". However, recent studies have shown this to be false. After extensively prolonged period of awareness, average humans can sleep comfortably for as long as 14 hours in row, but any amount over that has no effect for health. Sleeping over it causes dizziness, lack of muscular control, numbness and several other symptoms often confronted with too little sleep.
That one major function of sleep is consolidation and optimization of memories (including "unlearning") is evidenced by studies showing that mental functions are impaired by sleep deprivation and that sleep deprivation can even be lethal. Adequate rest and a properly functioning immune system are closely related. Sleep deprivation compromises the immune system by altering the blood levels of specialized immune cells and important proteins called cytokines, resulting in an increased chance of infection. We may begin to understand why sleep deprivation is lethal if we understand sleep as a necessary period of anabolic activity for all animals, and the basic need for anabolic activity as a prerequisite for life itself
posted by loseword @ 11:21 PM
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