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Chapter 3 - Sleep

Chapter 3 - Sleep. Unit 3 – Area of Study 1: Mind, brain and body Pages 132-176. Study Design Content.

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Chapter 3 - Sleep

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  1. Chapter 3 - Sleep Unit 3 – Area of Study 1: Mind, brain and body Pages 132-176

  2. Study Design Content • sleep as an altered state of consciousness: purpose, characteristics and patterns of the stages of sleep including rapid eye movement (REM) and the non-rapid eye movement (NREM) stages of sleep • methods used to study the level of alertness in normal waking consciousness and the stages of sleep: – measurement of physiological responses including electroencephalograph (EEG), electrooculargraph (EOG), heart rate, body temperature and galvanic skin response (GSR) – the use of sleep laboratories, video monitoring and self reports • the effects of total and partial sleep deprivation: – loss of REM and NREM sleep – sleep recovery patterns including amount of sleep required, REM rebound and microsleeps – sleep-wake cycle shifts during adolescence compared with child and adult sleep including delayed onset of sleep and need for sleep

  3. Sleep • Sleep is a naturally and regularly occurring ASC that usually occurs spontaneously and is primarily characterised by a loss of conscious awareness • Over a lifetime we spend about one-third of our time asleep

  4. Ways to Study Sleep • There are a few different methods we can use to study sleep: • Sleep laboratories • Electroencephalograph (EEG) • Electromyograph (EMG) • Electro-oculogram (EOG) • Heart rate/Core body temperature • Video reporting • Self-reports

  5. Ways to Study Sleep Sleep Laboratories • Most research takes place in sleep laboratories, also known as sleep units. • A sleep laboratory is made to resemble the bedroom and aims to make the patient as comfortable as possible. • Patients try to keep a normal routine before going to sleep, including an evening meal, television etc.

  6. Ways to Study Sleep • The procedure for conducting research at a sleep laboratory is known as polysomnography • Polysomnography is an intensive study of a sleeping person involving simultaneous monitoring and recording of various physiological responses of the sleeper over the course of a night • Box 3.1 – Preparing for sleep in a sleep laboratory, pg.136

  7. Ways to Study Sleep Electroencephalograph (EEG) • The most important information about sleep is given from the EEG. • An EEG detects, amplifies and records electrical activity in the brain. • The identification of EEG patterns during sleep has led researchers to distinguish between four different stages of sleep which are experienced by all people in a typical night’s sleep.

  8. Ways to Study Sleep Electromyograph(EMG) • The electromyograph (EMG) is a device used to detect, amplify and record electrical activity of muscles. • This is done through electrodes attached to the skin above the muscles. • EMG recordings show changes in muscle activity, muscle tone or muscle tension. • There are systematic changes in muscular activity during the course of a night’s sleep. Chapter 9 - Sleep

  9. Ways to Study Sleep Electro-oculargram(EOG) • The electro-oculargram (EOG) is a device used for measuring eye movements or eye positions by detecting, amplifying and recording electrical activity in eye muscles that control eye movements. • The EOG is most commonly used to measure changes in eye movements during different stages of sleep and while dreaming. Chapter 9 - Sleep

  10. Ways to Study Sleep Heart Rate/Core Body Temperature • Both heart rate and core body temperature drop throughout the progression from light sleep to deep sleep, and increase as we progress back to light sleep • Core body temperature can drop by as much as 1oC while we are asleep • Heart rate however, can have sudden and dramatic changes during sleep which are commonly associated with dreaming and the experiences of nightmares or night terrors

  11. Ways to Study Sleep Video Monitoring • Video cameras can be sued in sleep laboratories to record observable physiological responses during sleep • Sounds can be simultaneously recorded and infrared technology used so recordings can be made in little or no light • Video monitoring is particularly important for patients with serious sleep disorders

  12. Ways to Study Sleep Self-Reports • A sleep-diary is a common self-report used in the study of sleep • A sleep-diary is a self-reported record of an individuals sleep and waking patterns over a period of time, usually several weeks • Sleep-diaries are usually used in conjunction with polysomnography to support the assessment of sleep disorders and problems • Learning Activity 3.1 – Review questions, pg. 139

  13. Characteristics and Patterns of Sleep • Over the course of the night we experience two distinctly different types of sleep: • NREM Sleep: non-rapid-eye movement sleep • REM Sleep: rapid-eye movement sleep • These occur in continuous cycles with each following the other • In adults, one cycle of NREM sleep can last between 70-90minutes and consists of four distinct stages, each of which is identified by electrical brain wave pattern (EEG)

  14. Characteristics and Patterns of Sleep • A period of REM sleep follows each period of NREM sleep • A complete sleep cycle consists of a period of NREM sleep (not necessarily all four stages) and a period of REM sleep (tends to increase as the night progresses) • A complete cycle of sleep lasts from 80-120minutes and we go through this cycle 4-5 times during 8 hours of sleep a night

  15. Characteristics and Patterns of Sleep

  16. NREM Sleep • Approximately 80% of our sleep time is spent in NREM sleep, and typically the first half of the night has more NREM sleep than the second half of the night. • During NREM sleep the brain is active, but not as active as REM sleep or normal waking consciousness. • Some psychologists believe that NREM sleep may be the time when the body recuperates. Chapter 9 - Sleep

  17. NREM Sleep • NREM sleep consists of four different stages in which the sleeper progresses from a stage of light sleep to the stage of deepest sleep and back again to one or more stages to light sleep. • Using an EEG, psychologists can predict an individuals stage of sleep. • It has been found that when we first close our eyes and begin to relax, our brain emits bursts of alpha waves. • Alpha wave patterns are associated with relaxation and drowsiness and are characterised by high frequency and low amplitude EEG’s. • Fig 3.10 – Sleep Waves pg. 140 Chapter 9 - Sleep

  18. Chapter 9 - Sleep

  19. NREM Sleep • This transition period from being awake to being drowsy is sometimes called the hypnogogic state, or the twilight stage of sleep, and it is characterised by slow rolling eye movements. • During this stage, which may only last for a minute or two, people may experience flashes of light or colour or dreamlike images. • In this pre-sleep stage our body is winding down and beginning to drift towards the first stage of the NREM sleep cycle. Chapter 9 - Sleep

  20. NREM Sleep – Stage 1 • Stage 1 occurs as we drift into and out of a true sleep state. • We tend to gradually lose our awareness of ourselves and our surroundings but some of the time we are actually aware of faint sounds in our environment. • Physiological changes that occur in stage 1 include a decrease in – heart rate, respiration, body temperature and muscle tension. Chapter 9 - Sleep

  21. NREM Sleep – Stage 1 • As a result of the muscles relaxing, we sometimes experience a ‘jerking’ sensation where our body seems to go into a spasm. • This is known as a hypnic jerk and is a common occurrence during stage 1. • Also in stage 1, alpha waves are replaced by the more irregular, lower frequency, higher amplitude theta waves. • Stage 1 lasts for about 5 to 10 minutes. If we are woken in this stage we may feel we have not been asleep at all. Chapter 9 - Sleep

  22. NREM Sleep – Stage 2 • Stage 2 is a light stage of sleep and marks the point where someone can be said to be truly asleep. • During stage 2, which lasts about 20 minutes, body movements lessen, breathing becomes more regular, blood pressure and temperature continue to fall and heart rate is slower. • Brain waves in stage 2 are mainly theta waves. Chapter 9 - Sleep

  23. NREM Sleep – Stage 2 • Brief bursts of higher frequency brain wave activity called sleep spindles periodically appear on the EEG. • This is the brain still responding to various internal and external stimuli such as a knock on the door or muscle tension in the leg if you stretch it. • After about 5 minutes of stage 2 sleep, we are unlikely to respond to any stimuli, indicating that sleep is deeper now. Chapter 9 - Sleep

  24. NREM Sleep – Stage 3 • Stage 3 is the start of the deepest period of sleep (known as moderately deep sleep). • Heart rate, blood pressure and body temperature continue to drop and breathing rate is slow and steady. • The individual is extremely relaxed and becomes less and less responsive to the outside world. Chapter 9 - Sleep

  25. NREM Sleep – Stage 3 • During stage 3, there is a reduction in the brain’s electrical activity and delta waves appear to begin. • These make up about 20-50% of the brain waves recorded in stage 3. • Delta waves are slow, large, regular brain waves. • The presence of delta waves marks the beginning of slow wave sleep (SWS) which begin within an hour of falling asleep and lasts for about 30 minutes. Chapter 9 - Sleep

  26. NREM Sleep – Stage 4 • This is the deepest stage of sleep (known as very deep sleep). • Muscles are completely relaxed and we barely move. • Delta waves dominate our brain activity but they are larger than stage 3. • A person in stage 4 is very difficult to wake. • When awoken in stage 4, a person usually takes 10 minutes to orientate themselves and have a poor memory of sleep events (also known as sleep drunkenness or sleep inertia). Chapter 9 - Sleep

  27. NREM Sleep – Stage 4 • As the night progresses, less and less time is spent in stages 3 and 4. • In sleep stages close to the morning, there may be no stage 3 or 4 sleep at all. • This has led to the belief that sleep before midnight is best because it may be the most beneficial and rejuvenating sleep. • During stages 3 and 4, sleep phenomena such as sleepwalking, sleep talking and night terrors occur. Chapter 9 - Sleep

  28. NREM Sleep – Stage 4 • Moving through the sleep cycle from stage 1 to stage 4 takes about 30 to 45 minutes before we progressively move back up to stages 3, 2 and then 1. • Having progressed through one cycle lasting 70 to 90 minutes, we do not awaken, although our brain and body begin to respond as if we are about to wake up. • These are the signs that we are about to move into REM sleep. Chapter 9 - Sleep

  29. REM Sleep • During REM sleep the eyeballs rapidly move beneath the closed eyelids, darting back and forth and up and down in jerky movements. • The brain wave pattern associated with REM sleep is irregular, consisting of short high frequency beta waves. • However, REM sleep is slightly deeper than stage 1 and 2 NREM sleep because people are still difficult to wake during this period. Chapter 9 - Sleep

  30. REM Sleep • The body’s internal functioning is quite active during REM sleep as heart rate, blood pressure and breathing is higher/faster and more irregular. • Although there are some twitches in the face, fingers and toes, most skeletal muscles are still quite limp. • REM sleep is often called paradoxical sleep – internally the brain and body are active, while externally the body appears calm and inactive. Chapter 9 - Sleep

  31. REM Sleep • Research indicates that it is during REM sleep when most dreaming occurs. • In sleep laboratories, if a research participant is woken, about 80% of the time they will have reported that they were in fact dreaming and can remember the dream. • Some people believe that the rapid eye movements correspond to activity in the dream. Chapter 9 - Sleep

  32. REM Sleep • Throughout the night we pass continually from NREM and REM sleep cycles. • REM sleep periods usually lengthen and occur closer together as the night progresses. • A REM phase early in the night can last only a few minutes, whereas later in the night it can last for up to an hour. • Manual Activity 5 – Characteristics of Sleep Patterns, pg. 9 Chapter 9 - Sleep

  33. Sleep Overview • Box 3.2 – Case study: The man without REM sleep, pg. 145 • Box 3.4 – Why we dream? pg. 146 • Learning Activity 3.2 – Review questions, pg. 148 • Learning Activity 3.3 – Data analysis, pg. 149

  34. Changes in Sleep Patterns Over the Lifetime • The amount of time spent in NREM and REM sleep over the lifetime is highly variable • From birth onward the total amount of sleep decreases gradually as you age • The proportion of time spent in REM sleep decreases markedly from infancy to adolescence, remaining relatively stable into adulthood

  35. Changes in Sleep Patterns Over the Lifetime

  36. Changes in Sleep Patterns over the Lifetime • A newborn infant sleeps around 16 hours a day, with 50% of that time spent in REM sleep • By the end of infancy, total sleep time drops to 12-13 hours and about 25-30% is REM sleep • At the onset of adolescence, total sleep time is around 9 hours with 20% REM sleep • The gradual decrease in total sleep time continues throughout adulthood • Manual Activity 5 – Characteristic patterns for the stages of sleep – Learning through graphs and diagrams, pg.

  37. Sleep-Wake Cycle Shift during Adolescence • In general, the sleep of adolescent males and females declines from 10 hours a night to under 8 hours a night • Numerous research however, has shown that adolescents require more than 9 hours of sleep to function well when awake (Joseph & Blunden, 2009) • In addition, studies of adolescent sleep patterns indicate this population tend to have sleep problems, such as requiring a long time to fall asleep, insufficient night-time sleep on weekdays and difficulty waking up in the mornings • Insufficient sleep can have significant affects on normal daytime functioning

  38. Sleep-Wake Cycle Shift during Adolescence • Biological influence on an adolescent’s sleep primarily involves the bodies circadian rhythm which is a natural inbuilt, timing system or ‘biological clock’ which utilises the sleep hormone melatonin which causes us to feel sleepy at night • During adolescence, there is a hormonally induced shift of the body clock forward by 1-2 hours, causing the adolescent to become sleepier one or two hours later • This is known as the sleep-wake cycle shift • This affects the adolescent’s ability to fall asleep at the earlier time expected of them as a child

  39. Sleep-Wake Cycle Shift during Adolescence • This shift in the onset of the sleep period (called sleep phase onset) also means that there is biologically driven need to sleep for one or two hours longer • Starting school or work early, however does not allow for adolescents to sleep in and have the additional sleep that would naturally occur, this nightly sleep loss can accumulate as a sleep debt – sleep that is owed and needs to be made up • For example a nightly sleep debt of 90 minutes between Monday and Friday would add up to a total sleep debt of 7 and a half hours – on the weekend adolescents will often sleep in to make up their sleep loss

  40. Sleep-Wake Cycle Shift during Adolescence • Psychological and social factors can also influence an adolescent’s sleep habits • These biopsychosocial factors cause sleep to become a low priority for many adolescents • This typically results in erratic sleep patterns for many adolescents and can result in sleep deprivation • Box 3.5 – National Sleep Foundation report on adolescent needs and patterns • Box 3.7 – The sleep-waking cycle as a biological rhythm • Learning Activity 3.5 – Review questions, pg. 159 • Learning Activity 3.6 – Data analysis, pg. 159

  41. The Purpose of Sleep • Observations about the differing needs of sleep between individuals and among people of different ages, and research findings on the effects of sleep deprivation, have led psychologists to propose various theories on why we sleep • One set of theories proposes that sleep has a restorative function while an alternate theory suggests we sleep as a survival mechanism

  42. Sleep for Restoration • Restorative theories of sleep propose that sleep provides ‘time out’ to aid us in recovering from our daily activities which deplete us both mentally and physically • Research on ultra-marathon runners showed that following the event, the runners slept significantly longer and deeper than normal (Shapiro & others, 1981)

  43. Sleep for Restoration • It has been suggested that NREM and REM sleep have differing restorative functions • NREM sleep is believed to be important for restoring and repairing the body • REM sleep is thought to assist with restoring the brain and may have a role in higher mental functions such as memory and learning

  44. Sleep for Restoration • There is a general agreement that REM sleep serves an important biological need • In the controlled condition of a sleep lab, individuals were woken as soon as they moved into REM sleep with no ill-effects, however when permitted to sleep uninterrupted following periods of interrupted REM sleep, they spent more time in REM sleep than they normally would • Psychologists refer to this as REM rebound – catching up on REM sleep immediately following a period of lost REM sleep

  45. Sleep for Survival • The survival theory of sleep proposes that sleep evolved to enhance survival by protecting an organism through making it inactive during the part of the day where it is most risky or dangerous to move about • According to the survival theory, sleep serves as a function of protecting the sleeper from harm or death, therefore enhancing the survival of the species

  46. Sleep for Survival • Species will few natural predators such as lions, gorillas etc sleep as much as 15 hours per day • Grazing animals such as horses, cows, buffalo who have many predators, sleep for as little as 4 hours per day • On criticism of this theory is that it does not explain our total lack of awareness during sleep, a loss of consciousness during sleep may place the organism at greater risk • Learning Activity 3.9 – Review questions, pg. 164

  47. Sleep Deprivation • The term sleep deprivation means going without sleep. • Generally sleep deprivation results in a range of uncomfortable feelings such as irritability, tiredness, lack of concentration, headaches and loss of energy. • The extent of the discomfort depends on the individual, the amount of sleep lost, and the period of time across which it occurs. Chapter 9 - Sleep

  48. Sleep Deprivation • Sleep deprivation falls into two categories: • Total deprivation • Partial deprivation • Research on animals (ie rats) has shown that if an animal is deprived of sleep for a prolonged period of time, the animal eventually dies Chapter 9 - Sleep

  49. Partial Sleep Deprivation • Partial sleep deprivation results in a range of side effects – tiredness, lack of energy, lapses in attention, inability to concentrate for a long period of time, low motivation, impaired motor skills, irritation etc • Partial sleep loss over a relatively short period of time has temporary and minor psychological and physiological effects • Prolonged partial sleep loss is thought to affect cognitive functioning and memory • This can lead to more dangerous situations where accidents can be more likely to occur – driving, work etc

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