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| Sleep |
Sleep
Our lives are divided into periods of wakefulness and periods of sleep. While we are awake, input from our senses is forwarded to our brains and is actively processed to guide our activities and thinking. While we are asleep, input from our senses to our brains is dramatically reduced, our physical activity is curtailed, and our thinking processes are directed internally.
Much of our daily activity is planned around our need for a regular sleep period. We each have a biological clock attuned to a 24-hour cycle of day and night. A healthy adult human typically requires 5 to 9 hours of sleep during every 24-hour cycle. The need for sleep gradually changes with age. On average, a baby sleeps about 15 hours per day, while a senior sleeps about 7 hours per day. In aggregate, we spend about one third of our time on Earth asleep.
Pioneering research conducted by Seymour Benzer and Ron Konopka led to the discovery of a gene on the X-chromosome of Drosophila (fruit flies) that controlled their circadian rhythm. By causing mutations in this gene they were able to produce flies that had 19-hour days, 29-hour days, or random length days. The implication is that whatever the reasons for sleep, those reasons are built into every cell in the bodies of fruit flies. And since the cells in our bodies contain similar genes, our need for sleep is probably built in at the cellular level as well. When you feel tired at the end of the day, there are billions of cells in your body all asking for a nap at the same time.
Sleep seems to be necessary for survival and good health, but exactly why is not well understood. The urge to sleep typically grows near the end of a day, until we satisfy that urge. If someone is deprived of the opportunity to sleep for more than a day, the urge to sleep becomes more dominant and judgement becomes impaired. Soldiers on watch, operators of machinery, truck drivers, and pilots will eventually fall asleep even if it is obvious to the individuals that their lives will then be in peril.
How does your brain put you to sleep?
Latest research suggests that there are three components to sleeping that are controlled by three regions of the brain. The hypothalamus synchronizes our 24-hour circadian rhythm throughout the whole body, the thalamus sends out the signals that determine your level of wakefulness, and the brain stem controls the cycles from light sleep, to deep sleep, to rapid eye movement (REM) sleep. Sleep is an active mode with its own set of activities.
Sleep myths
All parts of the body slow down during sleep. In fact, parts of the brain are more active during sleep.
1. We sleep to rest. Sleep may provide an opportunity for the body to restore itself after a period of wakeful activity. Interestingly, fit and active people actually sleep less than those who are more sedentary.
2. When we sleep, our bodies simply grind to a halt. Sleep and wakefulness are states that are both actively controlled by the brain.
3. Sleep deprivation will lead to mental instability. With sleep deprivation, the urge to sleep increases, your ability to complete physical tasks is impaired, and your ability to make sound judgements is impaired. However, one or two periods of sleep will restore normal functions.
What is sleep?
Although the activity of sleeping is still somewhat of a mystery, it does have typical observable characteristics. A person who is sleeping:
Lies down, or slumps in place without any muscle effort to maintain an upright position.
1. Is quiet and still.
2. Has a low response to stimulation of the senses.
3. Awakens spontaneously or with gentle stimulation.
Our lives are divided into periods of wakefulness and periods of sleep. While we are awake, input from our senses is forwarded to our brains and is actively processed to guide our activities and thinking. While we are asleep, input from our senses to our brains is dramatically reduced, our physical activity is curtailed, and our thinking processes are directed internally.
Much of our daily activity is planned around our need for a regular sleep period. We each have a biological clock attuned to a 24-hour cycle of day and night. A healthy adult human typically requires 5 to 9 hours of sleep during every 24-hour cycle. The need for sleep gradually changes with age. On average, a baby sleeps about 15 hours per day, while a senior sleeps about 7 hours per day. In aggregate, we spend about one third of our time on Earth asleep.
Pioneering research conducted by Seymour Benzer and Ron Konopka led to the discovery of a gene on the X-chromosome of Drosophila (fruit flies) that controlled their circadian rhythm. By causing mutations in this gene they were able to produce flies that had 19-hour days, 29-hour days, or random length days. The implication is that whatever the reasons for sleep, those reasons are built into every cell in the bodies of fruit flies. And since the cells in our bodies contain similar genes, our need for sleep is probably built in at the cellular level as well. When you feel tired at the end of the day, there are billions of cells in your body all asking for a nap at the same time.
Sleep seems to be necessary for survival and good health, but exactly why is not well understood. The urge to sleep typically grows near the end of a day, until we satisfy that urge. If someone is deprived of the opportunity to sleep for more than a day, the urge to sleep becomes more dominant and judgement becomes impaired. Soldiers on watch, operators of machinery, truck drivers, and pilots will eventually fall asleep even if it is obvious to the individuals that their lives will then be in peril.
How does your brain put you to sleep?
Latest research suggests that there are three components to sleeping that are controlled by three regions of the brain. The hypothalamus synchronizes our 24-hour circadian rhythm throughout the whole body, the thalamus sends out the signals that determine your level of wakefulness, and the brain stem controls the cycles from light sleep, to deep sleep, to rapid eye movement (REM) sleep. Sleep is an active mode with its own set of activities.
Sleep myths
All parts of the body slow down during sleep. In fact, parts of the brain are more active during sleep.
1. We sleep to rest. Sleep may provide an opportunity for the body to restore itself after a period of wakeful activity. Interestingly, fit and active people actually sleep less than those who are more sedentary.
2. When we sleep, our bodies simply grind to a halt. Sleep and wakefulness are states that are both actively controlled by the brain.
3. Sleep deprivation will lead to mental instability. With sleep deprivation, the urge to sleep increases, your ability to complete physical tasks is impaired, and your ability to make sound judgements is impaired. However, one or two periods of sleep will restore normal functions.
What is sleep?
Although the activity of sleeping is still somewhat of a mystery, it does have typical observable characteristics. A person who is sleeping:
Lies down, or slumps in place without any muscle effort to maintain an upright position.
1. Is quiet and still.
2. Has a low response to stimulation of the senses.
3. Awakens spontaneously or with gentle stimulation.
Sleep cycles and brain waves
In 1929 a Swiss psychiatrist, Hans Berger, first used an electroencephalogram (EEG) to measure brain activity during sleep. An EEG measures the overall electrical activity of the brain at different frequencies and displays the results as wavy lines on a strip chart recorder. EEG measurements show that each night during sleep our brain activity passes through a number of well-defined cycles. The most common EEG frequencies observed during sleep are named after letters of the Greek alphabet so you may hear references to alpha, beta, gamma, delta, or theta waves in discussions of sleep cycles.
A typical night’s sleep activity passes through the following phases: you feel drowsy and alpha waves dominate while you fall asleep; your sleep then passes through 5 or 6 cycles of about 90 minutes each.
Each cycle passes systematically back and forth through five stages:
Stage 1: Light sleep – When questioned a person may claim to have still been awake.
In 1929 a Swiss psychiatrist, Hans Berger, first used an electroencephalogram (EEG) to measure brain activity during sleep. An EEG measures the overall electrical activity of the brain at different frequencies and displays the results as wavy lines on a strip chart recorder. EEG measurements show that each night during sleep our brain activity passes through a number of well-defined cycles. The most common EEG frequencies observed during sleep are named after letters of the Greek alphabet so you may hear references to alpha, beta, gamma, delta, or theta waves in discussions of sleep cycles.
A typical night’s sleep activity passes through the following phases: you feel drowsy and alpha waves dominate while you fall asleep; your sleep then passes through 5 or 6 cycles of about 90 minutes each.
Each cycle passes systematically back and forth through five stages:
Stage 1: Light sleep – When questioned a person may claim to have still been awake.
Stage 2: Medium sleep – A person is definitely asleep, but may react to loud noises.
Stage 3: Deep sleep – If awakened a person is confused and disoriented.
Stage 4: Relaxed sleep – Muscles are relaxed; blood pressure is lower, heart rate and breathing rates are lowered.
Stage 5: REM sleep – Muscles are still relaxed but a person’s eyes can be seen to move rapidly back and forth under the eyelids, as if following an active visual field. Blood flow to the brain increases.
Our brains are active all night long. Most dreaming occurs during Stage 3 and Stage 5
sleep. Most sleep-talking, sleep-walking, and nightmares occur during Stage 3 or Stage 4.
Why do we sleep?
All mammals, birds, and most other creatures sleep during some part of each day, and it is generally agreed that sleep must serve some basic biological function that enhances survival. The nature of that function remains poorly understood.
Sleep may be a process to conserve energy. When an animal falls asleep its metabolic rate decreases by about 10% and its body temperature falls by about 2ºC. Hibernation is an extension of sleep and has an obvious energy conservation function.
Periods of sleep might help to keep an animal safe from predators. If you can obtain enough food and drink in half a day, and are tucked up cozy, safe, asleep, and out of harm’s way for the rest of the day then there is less chance that you will stumble into some other hungry creature and be eaten.
Perhaps we sleep so that we can dream.
Dreams
It used to be thought that dreams were infrequent, unpredictable, and of very short duration. Dreams were thought to be bizarre, unrealistic and emotionally charged.
However, research over the past 50 years has led to a better understanding of the dream process.
The basic technique of dream research involves monitoring the EEGs of sleeping research subjects. Changes in the EEGs suggest when subjects are dreaming. Based on many studies, it is apparent that dreams occur during all stages of sleep and about one quarter of our sleep-time involves dreaming. When awakened, and asked about their dreams, the accounts of subjects indicate that the contents of most dreams are mundane, realistic, and have a thematic structure. REM sleep evokes the most predictable, frequent, and prolonged dream experiences.
The quality of a dream is related to the mental state of the dreamer. Talented visual thinkers tend to have more visual dream content. Depressed patients tend to give dream reports with a depressive tone. Schizophrenic patients tend to give dream reports that are disorganized and incoherent. Dreams seem to be remarkably independent of specific stimuli before, or during sleep. When subjects watched films that were violent, sad, or pornographic before sleeping, there was no measurable effect on subsequent dream content. When sleeping subjects were subjected to sounds, light flashes, cold water, or mild electrical shocks a dreamer might add the input as a temporary event, but the theme of a dream tended to remain unaffected. Some individuals have dreams that are repeated over several nights, and some dreams do involve emotional events. Many nightmares have some sort of chase sequence in which the dreamer struggles to avoid a dangerous peril.
Your conscious knowledge of a dream’s content dissipates rapidly on awakening. If you want to remember the contents of a dream you were experiencing, you have to repeat the story several times or write it down as soon as you wake up. This rapid dissipation of dream content could be explained if the experience of dreaming is actually the flow of information through your immediate-term memory while you are asleep. Recall that immediate-term memory can only hold about seven information items for up to thirty seconds. And while you are asleep immediate-term memory would receive little input from the senses, so most of its contents would have to come from your subconscious mind.
Thus the model of the conscious mind can be extended to provide a simple description of dreaming. Consciousness is the flow of information through your immediate-term memory while you are awake. This input can come from your senses or your subconscious mind. Dreams are the flow of information through your immediate-term memory while you are asleep. Since external stimuli are largely ignored during sleep, virtually all of your dream content must come from your subconscious mind.
What are dreams for? Although the functions of sleep and dreaming are not well understood, dreams seem to have at least three practical functions:
1. Dreams seem to be involved in sorting information collected during the day, and perhaps dreaming assists in filing that information away in memory. This function would account for the mundane themes yet unusual combinations of topics in most dreams. You have to browse through existing memories to find the best location for a new memory, and you want to cross-reference a new memory to other topics to increase its usefulness. There is some research that suggests a session of sleep with regular dreaming helps to entrench memories.
2. Dreams may be involved in rehearsing possible real life scenarios. In dreams you can work through a wide variety of possible actions and consequences.
Dreaming may be analogous to security training when you contemplate, plan,
and practice for all kinds of possible scenarios. The security comparison is apt because at a fundamental level our daily actions are all designed to enhance our chances of survival. Many nightmares are probably rehearsals for avoiding danger.
3. Dreams wake us up in the middle of the night so we can avoid wetting the bed.
That may seem like a trivial purpose for dreaming, but avoiding bedwetting is a basic social need and humans are social animals.
Before proceeding to Chapter 7 and a model of the Subconscious, let’s take a moment to summarize and clarify the meanings of a few key terms:
1. ‘Non-conscious’ is a term used to describe the neural systems of simple animals.
2. In animals with more complex neural systems, mental activity is divided into two realms, ‘conscious’ and ‘subconscious’.
3. There are a variety of conditions that can reduce an animal’s level of consciousness.
4. Trauma can render a conscious animal ‘unconscious’, a state in which all conscious and some subconscious activities are curtailed.
5. ‘Sleep’ represents a period of reduced consciousness. While you sleep, your subconscious mind keeps your body functioning. During a quarter of the time you are asleep, your subconscious channels information through your immediate-term memory that then becomes the subjects of your dreams.
Stage 3: Deep sleep – If awakened a person is confused and disoriented.
Stage 4: Relaxed sleep – Muscles are relaxed; blood pressure is lower, heart rate and breathing rates are lowered.
Stage 5: REM sleep – Muscles are still relaxed but a person’s eyes can be seen to move rapidly back and forth under the eyelids, as if following an active visual field. Blood flow to the brain increases.
Our brains are active all night long. Most dreaming occurs during Stage 3 and Stage 5
sleep. Most sleep-talking, sleep-walking, and nightmares occur during Stage 3 or Stage 4.
Why do we sleep?
All mammals, birds, and most other creatures sleep during some part of each day, and it is generally agreed that sleep must serve some basic biological function that enhances survival. The nature of that function remains poorly understood.
Sleep may be a process to conserve energy. When an animal falls asleep its metabolic rate decreases by about 10% and its body temperature falls by about 2ºC. Hibernation is an extension of sleep and has an obvious energy conservation function.
Periods of sleep might help to keep an animal safe from predators. If you can obtain enough food and drink in half a day, and are tucked up cozy, safe, asleep, and out of harm’s way for the rest of the day then there is less chance that you will stumble into some other hungry creature and be eaten.
Perhaps we sleep so that we can dream.
Dreams
It used to be thought that dreams were infrequent, unpredictable, and of very short duration. Dreams were thought to be bizarre, unrealistic and emotionally charged.
However, research over the past 50 years has led to a better understanding of the dream process.
The basic technique of dream research involves monitoring the EEGs of sleeping research subjects. Changes in the EEGs suggest when subjects are dreaming. Based on many studies, it is apparent that dreams occur during all stages of sleep and about one quarter of our sleep-time involves dreaming. When awakened, and asked about their dreams, the accounts of subjects indicate that the contents of most dreams are mundane, realistic, and have a thematic structure. REM sleep evokes the most predictable, frequent, and prolonged dream experiences.
The quality of a dream is related to the mental state of the dreamer. Talented visual thinkers tend to have more visual dream content. Depressed patients tend to give dream reports with a depressive tone. Schizophrenic patients tend to give dream reports that are disorganized and incoherent. Dreams seem to be remarkably independent of specific stimuli before, or during sleep. When subjects watched films that were violent, sad, or pornographic before sleeping, there was no measurable effect on subsequent dream content. When sleeping subjects were subjected to sounds, light flashes, cold water, or mild electrical shocks a dreamer might add the input as a temporary event, but the theme of a dream tended to remain unaffected. Some individuals have dreams that are repeated over several nights, and some dreams do involve emotional events. Many nightmares have some sort of chase sequence in which the dreamer struggles to avoid a dangerous peril.
Your conscious knowledge of a dream’s content dissipates rapidly on awakening. If you want to remember the contents of a dream you were experiencing, you have to repeat the story several times or write it down as soon as you wake up. This rapid dissipation of dream content could be explained if the experience of dreaming is actually the flow of information through your immediate-term memory while you are asleep. Recall that immediate-term memory can only hold about seven information items for up to thirty seconds. And while you are asleep immediate-term memory would receive little input from the senses, so most of its contents would have to come from your subconscious mind.
Thus the model of the conscious mind can be extended to provide a simple description of dreaming. Consciousness is the flow of information through your immediate-term memory while you are awake. This input can come from your senses or your subconscious mind. Dreams are the flow of information through your immediate-term memory while you are asleep. Since external stimuli are largely ignored during sleep, virtually all of your dream content must come from your subconscious mind.
What are dreams for? Although the functions of sleep and dreaming are not well understood, dreams seem to have at least three practical functions:
1. Dreams seem to be involved in sorting information collected during the day, and perhaps dreaming assists in filing that information away in memory. This function would account for the mundane themes yet unusual combinations of topics in most dreams. You have to browse through existing memories to find the best location for a new memory, and you want to cross-reference a new memory to other topics to increase its usefulness. There is some research that suggests a session of sleep with regular dreaming helps to entrench memories.
2. Dreams may be involved in rehearsing possible real life scenarios. In dreams you can work through a wide variety of possible actions and consequences.
Dreaming may be analogous to security training when you contemplate, plan,
and practice for all kinds of possible scenarios. The security comparison is apt because at a fundamental level our daily actions are all designed to enhance our chances of survival. Many nightmares are probably rehearsals for avoiding danger.
3. Dreams wake us up in the middle of the night so we can avoid wetting the bed.
That may seem like a trivial purpose for dreaming, but avoiding bedwetting is a basic social need and humans are social animals.
Before proceeding to Chapter 7 and a model of the Subconscious, let’s take a moment to summarize and clarify the meanings of a few key terms:
1. ‘Non-conscious’ is a term used to describe the neural systems of simple animals.
2. In animals with more complex neural systems, mental activity is divided into two realms, ‘conscious’ and ‘subconscious’.
3. There are a variety of conditions that can reduce an animal’s level of consciousness.
4. Trauma can render a conscious animal ‘unconscious’, a state in which all conscious and some subconscious activities are curtailed.
5. ‘Sleep’ represents a period of reduced consciousness. While you sleep, your subconscious mind keeps your body functioning. During a quarter of the time you are asleep, your subconscious channels information through your immediate-term memory that then becomes the subjects of your dreams.
