Psychology - Chapter 2: Sleep
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What is sleep?
Sleep is a regularly occurring natural ASC and is primarily characterised by a loss of consciousness.
What is a sleep laboratory and why is it used?
A sleep laboratory is a bedroom that is connected to a 'control room' where researchers monitor sleep patterns throughout the night. Here, patients with sleep disorders can be diagnosed and treated, as well as studied for research purposes. Each bedroom is decorated to be as homelike and as comfortable as possible, so that the patient's behaviour patterns are as close to normal as possible.
What is a polysomnography?
The procedure for conducting sleep observations or tests in a sleep laboratory is commonly called polysomnography. Polysomnogrpahy is an intensive study of a sleeping person involving simultaneous monitoring and recording of various physiological responses during sleep.
What is an EEG? What does it show about the sleeping person and about a typical night's sleep?
An EEG or Electroencephalograph is a device that detects, amplifies and records electrical activity (DARE) produced by the brain during sleep and dreaming. The electrical activity is represented as distinctive brain waves, which are displayed as a graph. Identification of different brain wave patterns during sleep has enabled researchers to distinguish between four different stages of sleep and two types of sleep that tend to be experienced by all people during a typical night's sleep.
What is an EMG? What does it show about muscular activity during sleep?
An EMG or Electromyograph is a device that detects, amplifies and records the electrical activity (DARE) of muscles. EMG recordings generally show the strength of electrical activity occurring in the muscles, which indicates changes in muscle activity (movement) and muscle tone (tension). The information is obtained by attaching electrodes to the skin above the particular muscles whose activity is being monitored. Sometimes the activity in facial muscles is recorded. At other times, leg muscles, muscles on the trunk, or a combination of theses are recorded. The records of the EMG are displayed as line graphs, similar to the EEG and EOG. They can be produced on paper or on a computer monitor. As with EEG recordings, EMG records show that there are identifiable changes in muscular activity during the course of a typical night's sleep. For example, our muscles progressively relax (decrease in muscle tone) as we pass into deeper stages of sleep. There are also distinguishable periods when our muscles may spasm (during light sleep) or be complete relaxed (during deep sleep).
What is an EOG? What has it revealed about sleep?
An EOG or Electro-oculogram is a device used for measuring eye movements or eye positions by detecting, amplifying and recording electrical activity (DARE) in eye muscles that control eye movement. This is done through electrodes attached to areas of the face surrounding the eyes. The records of the EOG are displayed as line graphs, similar to those produced by the EEG and EMG. They can also be produced on paper or on a computer monitor. The EOG is most commonly used to measure changes in eye movements over time during different stages of sleep and while dreaming. Sleep research studies that have used the EOG have revealed that there are two different types of sleep, called rapid-eye-movement (REM) and non-rapid-eye-movement (NREM) sleep.
What has heart rate and body temperature revealed about sleep?
As with study of NWC, heart rate and core body temperature are also commonly measured physiological responses in the study of sleep and other ASC. Both heart rate and core body temperature gradually drop as we progressively drift from light sleep into a deeper sleep, and then gradually increase as we drift from deeper sleep to lighter sleep. Core body temperature can drop by more than 1°C while we are asleep. However, unlike body temperature during sleep, there can be sudden and quite dramatic changes in heart rate depending on what sleep is being experienced. For example, experiences of sleep associated with dreaming such as nightmares, night terrors and sleep disorders can change heart rate.
How is video monitoring used to study sleep?
Video monitors are used in most sleep laboratories to record externally observable physiological responses accompanying sleep (including dreaming) and changes in types and patterns of sleep. The video cameras can simultaneously record sounds and use infrared technology so that recordings can be made in conditions of little or no light. Recordings are made in real time but computer-assisted technologies can be used for later analysis of a scene or single frame. Video monitoring is particularly important with participants (or patients) who have a serious sleep disorder.
Describe how self-reports may be used to study sleep.
- Self-reports, such as a sleep diary, or sleep log, is a self-reported record of an individual's sleep and waking time activities, usually over a period of several weeks. Sleep diaries are most commonly used in partnership with polysomnographic tests to support the assessment of sleep disorders and problems, particularly their severity and causes. The data an individual is required to record in a sleep diary usually include:
- The time when trying to fall asleep
- The time when it is believed sleep onset occurred
- The number of times fallen asleep
- The time and length of awakenings during sleep
- The time of waking up in the morning
- The time of getting up following morning awakening
Briefly describe the pattern and proportions of NREM and REM sleep in a typical night's sleep.
During a typical night's sleep, people move through each NREM stages one by one and once they've entered NREM stage 4 they go back through stages 3 and 2 and then enter REM sleep. For example; a typical sleeping pattern is NREM sleep stages 1, 2, 3, 4, 3, 2 and then REM sleep. People cycle in and out of REM and NREM in a 90 minute cycle which occurs four or five times during a typical night's sleep - however the distribution of REM and NREM changes as the night goes on. For example; as sleep progresses, the periods of NREM sleep get shorter and periods of REM sleep get longer and cycle closer together.
Why are NREM stages 3 and 4 referred to as slow wave sleep (SWS)?
Because both NREM stages 3 and 4 record very slow frequency and large amplitude Delta brain waves by the EEG.
Why is REM sleep sometimes referred to as paradoxical sleep?
REM sleep is sometimes referred to as paradoxical sleep - because during REM sleep, internally, the brain and body are active, while, externally, the body appears calm and inactive. An observer might say the sleeper appears paralyzed during REM sleep even though the body's internal functioning is very active.
Briefly describe two general trends in the pattern and proportion of NREM and REM sleep across the lifespan.
- From birth onwards, the amount and proportion of total sleep time spent in REM sleep decreases, but then remains relatively stable into adulthood and old age
- The amount of NREM sleep also decreases as we age
Compare and contrast sleep-wake patterns of children, adolescents and adults with reference to two distinguishing features of each lifespan stage.
As we get older the amount of time we spend sleeping decreases. In addition, the proportion of total sleep time spent in REM sleep decreases markedly from infancy to adolescence, and then remains stable into adulthood and old age. The amount of NREM sleep time also decreases, but compared with the drop in REM sleep up to adolescence, NREM sleep tends to be relatively stable. For example:
· Newborn infants - Sleep for around 16 hours a day, about 50% is REM sleep.
· End of Infancy - Total sleep time drops to around 12-13 hours and about 25-30% is REM sleep
· End of childhood / Onset of adolescence - Total sleep time drops to around 9 hours a day and about 20% is REM sleep
· Late adulthood - Total sleep time averages about 6-7 hours and about one-third is REM sleep
Individuals in their sixties and older tend to report that their sleep is much lighter with increased awakenings during the night. This combined with polysomnography research findings suggest that NREM sleep of elderly people is mostly stage 2. Furthermore, by age 90, stage 3 and 4 is rarely experienced, if at all.
What does the term sleep-wake cycle shift mean?
During adolescence, there is hormonally induced shift of the body clock forward by about one to two hours, making the adolescent sleepier one to two hours later. This is known as the sleep-wake cycle shift, resulting in sleepiness at a later time. This affects the adolescent's ability to fall asleep and also means that there is a biologically driven need to sleep one to two hours longer.
Briefly describe the sleep-wake cycle shift occurring during adolescence.
- In general, adolescents between the ages of 13 and 19 years require more than 9 hours of sleep each night to function well when awake; however, most adolescents, have less than 8 hours a night. In addition, studies of adolescent sleep patterns indicate that adolescents tend to have sleep problems, such as:
- Requiring a lengthy time to fall asleep
- Insufficient night time sleep on weekdays
- Difficulty waking up in the morning
What does 'delayed onset of sleep' mean?
A delayed onset of sleep means that it takes longer to 'wind down' and actually go to sleep due to biological problems, such as the body clock going forward 1-2 hours that exerts considerable pressure towards later sleep times.
What is 'sleep debt'?
Sleep debt is an accumulated nightly sleep loss that is owed and needs to be made up. For example, early school (or work) starts don't allow an adolescent to sleep in and have the additional sleep that would normally occur, resulting in a sleep debt of 90 minutes between Monday and Friday adding up to a total sleep debt of 7½ hours, which adolescents then try to make up the loss sleep by sleeping in on weekends. ½
Briefly describe the purpose of sleep in terms of restorative theory.
The purpose of sleep in terms of restorative theories proposes that sleep is a period of physiological rest, which provides 'time out' to help us recover from depleting activities during waking time that use up the body's physical and mental resources. For example, sleep provides an opportunity for the body to replenish the stores of energy that have been depleted during the day. It also allows any damaged cells to be repaired and various muscles to be detoxified or to rid themselves of waste products.
What is REM rebound? Why does it occur?
REM rebound involves catching up on REM sleep immediately following a period of lost REM sleep by spending more time than usual in REM sleep when next asleep. For example, in the controlled conditions of sleep laboratories, people were woken up each time they lapsed into REM sleep, with no obvious ill-effects. However, when they were allowed to sleep interrupted, they spent more time then they normally would in the REM stage. It seems for some reason they needed to make up for lost REM sleep. Psychologists refer to this as REM rebound.
Outline one experimental research study in support of restorative theory.
One experimental research study that supports the restorative theory was the effects of strenuous physical exercise on sleep, where researchers observed athletes who participated in a 92-kilometre ultra-marathon. It was found that the runners slept significantly deeper and longer in the two nights after the race, suggesting that sleep is a period of physiological rest, which provides an opportunity for the body to replenish the stores of energy that have been depleted during the day.
Briefly describe the purpose of sleep in terms of survival theory.
The purpose of sleep in terms of the survival theory proposes that sleep evolved to enhance survival, by protecting an organism by making it inactive during part of the day when it is most risky or dangerous to move about. For example, once an organism has fulfilled all its survival functions such as eating, drinking, caring for its young and reproducing, it must spend the rest of its time conserving energy, hidden and protected from predators. While sleeping, an organism is not physically interacting with the environment and is less likely to attract the attention of potential predators. Thus, according to the survival theory, sleep serves the function of protecting the sleeper from harm or death, and therefore enhances survival of the species.
Outline one experimental research study in support of survival theory.
One experimental research study that supports the survival theory comes from the study on behaviour patterns and sleep-waking cycles on different species. For example, it was found that animals with few natural predators, such as lions, tigers and gorillas, sleep as much as 15 hours a day, whereas grazing animals such as horses, zebras and cows have many predators and struggle to escape from their predators. They cannot hide easily, climb trees or burrow quickly to escape danger. Thus, they are safer awake and tend to sleep for short periods that total only about 4 hour per day.
Define sleep deprivation.
Sleep deprivation means going without sleep. Sleep deprivation falls into two categories, partial and total.
What is the difference between partial sleep deprivation and total sleep deprivation?
Partial sleep deprivation involves having less sleep than what is normally required, whereas total sleep deprivation involves not having any sleep at all.
List key findings of research with sleep-deprived animals.
Numerous experiments have been conducted with rats in which they were totally deprived of sleep for prolonged periods of time. It was found that the sleep deprived rats were unable to maintain a constant body temperature, resulting in excessive heat loss, in which they eventually died after 2-3 weeks of no sleep. Autopsies were conducted after their death and showed that their immune systems had collapsed, resulting in blood poisoning and ultimately death. These research findings suggest that sleep is vital to the regulation and stability of rat's internal environment and this may also apply to humans.
What are the three relevant ethical guidelines that psychologists must follow when constructing research on sleep deprivation with human participants.
- Roles and Responsibilities of the researcher: The researcher is responsible for ensuring that the research is conducted in such a manner that the wellbeing of research participants is the main concern and that participants are not placed at risk or injury or harm in any way. Under no circumstances is the researcher allowed to conduct research that causes participants severe distress
What are some common psychological and physiological effects on partial and total sleep deprivation?
- Some common psychological and physiological effects of partial sleep deprivation include:
- - Tiredness
- - Lack of energy
- - Lapses in attention
- - Inability to concentrate for a long period of time
- - Low level of motivation
- - Impaired motor skills
- - Occasional headaches
- Some common psychological and physiological effects of total sleep deprivation include:
- - Depression
- - Hallucinations
- - Delusions
- - Paranoia (a false belief that others want to harm you)
- - Hand tremors
- - Difficulty focusing the eyes
- - Lack of energy and strength
- - Slurred speech
- - Increased sensitivity to pain
How quickly and how well do people usually recover from the side effects of:
a) Partial sleep deprivation
b) Total sleep deprivation
- a) Generally, people who suffer from partial sleep deprivation only experience temporary and relatively minor psychological and physiological effects. They are able to recover quickly from the sleep loss effects when the acquired sleep debt is repaid.
- b) Prolonged total sleep deprivation has no long-lasting effects either psychologically or physiologically, and is also only temporary and disappears after a good night's sleep.
What is a microsleep and when is it more likely to occur?
A microsleep is a very short period of drowsiness or sleeping that occurs while a person appears to be awake. A microsleep is likely to occur when an individual is totally sleep deprived after 3-4 sleepless days. After a microsleep, which usually lasts for a very brief period of time, individuals may have no memory of what happened during the microsleep.
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