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  • Chapter9 Power Point Lecture

    1. 1. Chapter 9 Wakefulness and Sleep
    2. 2. Rhythms of Waking and Sleep <ul><li>Animals generate endogenous 24 hour cycles of wakefulness and sleep. </li></ul><ul><li>Some animals generate endogenous circannual rhythms, internal mechanisms that operate on an annual or yearly cycle. </li></ul><ul><ul><li>Example: Birds migratory patterns, animals storing food for the winter. </li></ul></ul>
    3. 3. Rhythms of Waking and Sleep <ul><li>All animals produce endogenous circadian rhythms, internal mechanisms that operate on an approximately 24 hour cycle. </li></ul><ul><ul><li>Regulates the sleep/ wake cycle. </li></ul></ul><ul><ul><li>Also regulates the frequency of eating and drinking, body temperature, secretion of hormones, volume of urination, and sensitivity to drugs. </li></ul></ul>
    4. 4. Fig. 9-2, p. 267
    5. 5. Rhythms of Waking and Sleep <ul><li>Circadian rhythms: </li></ul><ul><li>Remains consistent despite lack of environmental cues indicating the time of day </li></ul><ul><li>Can differ between people and lead to different patterns of wakefulness and alertness. </li></ul><ul><li>Change as a function of age. </li></ul><ul><ul><li>Example: sleep patterns from childhood to late adulthood. </li></ul></ul>
    6. 6. Rhythms of Waking and Sleep <ul><li>Experiments designed to determine the length of the circadian rhythm place subjects in environments with no cues to time of day. </li></ul><ul><li>Results depend upon the amount of light to which subjects are artificially exposed. </li></ul><ul><ul><li>Rhythms run faster in bright light conditions and subjects have trouble sleeping. </li></ul></ul><ul><ul><li>In constant darkness, people have difficulty waking. </li></ul></ul>
    7. 7. Rhythms of Waking and Sleep <ul><li>Human circadian clock generates a rhythm slightly longer than 24 hours when it has no external cue to set it. </li></ul><ul><li>Most people can adjust to 23- or 25- hour day but not to a 22- or 28- hour day. </li></ul><ul><li>Bright light late in the day can lengthen the circadian rhythm. </li></ul>
    8. 8. Rhythms of Waking and Sleep <ul><li>Mechanisms of the circadian rhythms include the following: </li></ul><ul><ul><li>The Suprachiasmatic nucleus. </li></ul></ul><ul><ul><li>Genes that produce certain proteins. </li></ul></ul><ul><ul><li>Melatonin levels. </li></ul></ul>
    9. 9. Rhythms of Waking and Sleep <ul><li>The suprachiasmatic nucleus (SCN) is part of the hypothalamus and the main control center of the circadian rhythms of sleep and temperature. </li></ul><ul><ul><li>Located above the optic chiasm. </li></ul></ul><ul><ul><li>Damage to the SCN results in less consistent body rhythms that are no longer synchronized to environmental patterns of light and dark. </li></ul></ul>
    10. 10. Fig. 9-4, p. 269
    11. 11. Rhythms of Waking and Sleep <ul><li>The SCN is genetically controlled and independently generates the circadian rhythms. </li></ul><ul><li>Single cell extracted from the SCN and raised in tissue culture continues to produce action potential in a rhythmic pattern. </li></ul><ul><li>Various cells communicate with each other to sharpen the circadian rhythm. </li></ul>
    12. 12. Rhythms of Waking and Sleep <ul><li>Two types of genes are responsible for generating the circadian rhythm. </li></ul><ul><ul><li>Period - produce proteins called Per. </li></ul></ul><ul><ul><li>Timeless - produce proteins called Tim. </li></ul></ul><ul><li>Per and Tim proteins increase the activity of certain kinds of neurons in the SCN that regulate sleep and waking. </li></ul><ul><li>Mutations in the Per gene result in odd circadian rhythms. </li></ul>
    13. 13. Fig. 9-5, p. 270
    14. 14. Rhythms of Waking and Sleep <ul><li>The SCN regulates waking and sleeping by controlling activity levels in other areas of the brain. </li></ul><ul><li>The SCN regulates the pineal gland , an endocrine gland located posterior to the thalamus. </li></ul><ul><li>The pineal gland secretes melatonin , a hormone that increases sleepiness. </li></ul>
    15. 15. Rhythms of Waking and Sleep <ul><li>Melatonin secretion usually begins 2 to 3 hours before bedtime. </li></ul><ul><li>Melatonin feeds back to reset the biological clock through its effects on receptors in the SCN. </li></ul><ul><li>Melatonin taken in the afternoon can phase-advance the internal clock and can be used as a sleep aid. </li></ul>
    16. 16. Rhythms of Waking and Sleep <ul><li>The purpose of the circadian rhythm is to keep our internal workings in phase with the outside world. </li></ul><ul><li>Light is critical for periodically resetting our circadian rhythms. </li></ul><ul><li>A zeitgeber is a term used to describe any stimulus that resets the circadian rhythms. </li></ul><ul><li>Exercise, noise, meals, and temperature are others zeitgebers. </li></ul>
    17. 17. Rhythms of Waking and Sleep <ul><li>Jet lag refers to the disruption of the circadian rhythms due to crossing time zones. </li></ul><ul><ul><li>Stems from a mismatch of the internal circadian clock and external time. </li></ul></ul><ul><li>Characterized by sleepiness during the day, sleeplessness at night, and impaired concentration. </li></ul><ul><li>Traveling west “phase-delays” our circadian rhythms. </li></ul><ul><li>Traveling east “phase-advances” our circadian rhythms. </li></ul>
    18. 18. Fig. 9-6, p. 272
    19. 19. Rhythms of Waking and Sleep <ul><li>Light resets the SCN via a small branch of the optic nerve known as the retinohypothalamic path . </li></ul><ul><ul><li>Travels directly from the retina to the SCN. </li></ul></ul><ul><li>The retinohypothalamic path comes from a special population of ganglion cells that have their own photopigment called melanopsin . </li></ul><ul><ul><li>The cells respond directly to light and do not require any input from the rods or cones. </li></ul></ul>
    20. 20. Stages of Sleep And Brain Mechanisms <ul><li>Sleep is a specialized state that serves a variety of important functions including: </li></ul><ul><ul><li>conservation of energy. </li></ul></ul><ul><ul><li>repair and restoration. </li></ul></ul><ul><ul><li>learning and memory consolidation. </li></ul></ul>
    21. 21. Stages of Sleep And Brain Mechanisms <ul><li>The electroencephalograph (EEG) allowed researchers to discover that there are various stages of sleep. </li></ul><ul><li>Over the course of about 90 minutes: </li></ul><ul><ul><li>a sleeper goes through sleep stages 1, 2, 3, and 4 </li></ul></ul><ul><ul><li>then returns through the stages 3 and 2 to a stage called REM. </li></ul></ul>
    22. 22. Stages of Sleep And Brain Mechanisms <ul><li>Alpha waves are present when one begins a state of relaxation. </li></ul><ul><li>Stage 1 sleep is when sleep has just begun. </li></ul><ul><ul><li>the EEG is dominated by irregular, jagged, low voltage waves. </li></ul></ul><ul><ul><li>brain activity begins to decline. </li></ul></ul>
    23. 23. Stages of Sleep And Brain Mechanisms <ul><li>Stage 2 sleep is characterized by the presence of: </li></ul><ul><ul><li>Sleep spindles - 12- to 14-Hz waves during a burst that lasts at least half a second. </li></ul></ul><ul><ul><li>K-complexes - a sharp high-amplitude negative wave followed by a smaller, slower positive wave. </li></ul></ul>
    24. 24. Stages of Sleep And Brain Mechanisms <ul><li>Stage 3 and stage 4 together constitute slow wave sleep (SWS) and is characterized by: </li></ul><ul><ul><li>EEG recording of slow, large amplitude wave. </li></ul></ul><ul><ul><li>Slowing of heart rate, breathing rate, and brain activity. </li></ul></ul><ul><ul><li>Highly synchronized neuronal activity. </li></ul></ul>
    25. 25. Stages of Sleep And Brain Mechanisms <ul><li>Rapid eye movement sleep (REM) are periods characterized by rapid eye movements during sleep. </li></ul><ul><li>Also known as “ paradoxical sleep ” because it is deep sleep in some ways, but light sleep in other ways. </li></ul><ul><li>EEG waves are irregular, low-voltage and fast. </li></ul><ul><li>Postural muscles of the body are more relaxed than other stages. </li></ul>
    26. 26. Fig. 9-9, p. 276
    27. 27. Stages of Sleep And Brain Mechanisms <ul><li>Stages other than REM are referred to as non-REM sleep (NREM) . </li></ul><ul><li>When one falls asleep, they progress through stages 1, 2, 3, and 4 in sequential order. </li></ul><ul><li>After about an hour, the person begins to cycle back through the stages from stage 4 to stages 3 and 2 and than REM. </li></ul><ul><li>The sequence repeats with each cycle lasting approximately 90 minutes. </li></ul>
    28. 28. Stages of Sleep And Brain Mechanisms <ul><li>Stage 3 and 4 sleep predominate early in the night. </li></ul><ul><ul><li>The length of stages 3 and 4 decrease as the night progresses. </li></ul></ul><ul><li>REM sleep is predominant later in the night. </li></ul><ul><ul><li>Length of the REM stages increases as the night progresses. </li></ul></ul><ul><li>REM is strongly associated with dreaming, but people also report dreaming in other stages of sleep. </li></ul>
    29. 29. Fig. 9-10, p. 277
    30. 30. Stages of Sleep And Brain Mechanisms <ul><li>Various brain mechanisms are associated with wakefulness and arousal. </li></ul><ul><li>The reticular formation is a part of the midbrain that extends from the medulla to the forebrain and is responsible for arousal. </li></ul>
    31. 31. Table 9-1, p. 280
    32. 32. Stages of Sleep And Brain Mechanisms <ul><li>The pontomesencephalon is a part of the midbrain that contributes to cortical arousal. </li></ul><ul><ul><li>Axons extend to the thalamus and basal forebrain which release acetylcholine and glutamate </li></ul></ul><ul><ul><li>produce excitatory effects to widespread areas of the cortex. </li></ul></ul><ul><li>Stimulation of the pontomesencephalon awakens sleeping individuals and increases alertness in those already awake. </li></ul>
    33. 33. Stages of Sleep And Brain Mechanisms <ul><li>The locus coeruleus is small structure in the pons whose axons release norepinephrine to arouse various areas of the cortex and increase wakefulness. </li></ul><ul><ul><li>Usually dormant while asleep. </li></ul></ul>
    34. 34. Fig. 9-11, p. 279
    35. 35. Stages of Sleep And Brain Mechanisms <ul><li>The basal forebrain is an area anterior and dorsal to the hypothalamus containing cells that extend throughout the thalamus and cerebral cortex. </li></ul><ul><li>Cells of the basal forebrain release the inhibitory neurotransmitter GABA. </li></ul><ul><li>Inhibition provided by GABA is essential for sleep. </li></ul><ul><li>Other axons from the basal forebrain release acetylcholine which is excitatory and increases arousal. </li></ul>
    36. 36. Fig. 9-12, p. 280
    37. 37. Stages of Sleep And Brain Mechanisms <ul><li>The hypothalamus contains neurons that release “histamine” to produce widespread excitatory effects throughout the brain. </li></ul><ul><ul><li>Anti-histamines produce sleepiness. </li></ul></ul>
    38. 38. Stages of Sleep And Brain Mechanisms <ul><li>Orexin is a peptide neurotransmitter released in a pathway from the lateral nucleus of the hypothalamus highly responsible for the ability to stay awake. </li></ul><ul><ul><li>Stimulates acetylcholine-releasing cells in the forebrain and brain stem to increase wakefulness and arousal. </li></ul></ul>
    39. 39. Stages of Sleep And Brain Mechanisms <ul><li>Decreased arousal required for sleep is accomplished via the following ways: </li></ul><ul><ul><li>Decreasing the temperature of the brain and the body. </li></ul></ul><ul><ul><li>Decreasing stimulation by finding a quiet environment. </li></ul></ul><ul><ul><li>Accumulation of adenosine in the brain to inhibit the basal forebrain cells responsible for arousal. </li></ul></ul><ul><ul><ul><li>Caffeine blocks adenosine receptors. </li></ul></ul></ul>
    40. 40. Stages of Sleep And Brain Mechanisms <ul><li>(cont’d): </li></ul><ul><li>Accumulation of prostaglandins that accumulate in the body throughout the day to induce sleep. </li></ul><ul><ul><li>Prostaglandins stimulate clusters of neurons that inhibit the hypothalamic cells responsible for increased arousal. </li></ul></ul>
    41. 41. Stages of Sleep And Brain Mechanisms <ul><li>During REM sleep: </li></ul><ul><ul><li>Activity increases in the pons (triggers the onset of REM sleep), limbic system, parietal cortex and temporal cortex. </li></ul></ul><ul><ul><li>Activity decreases in the primary visual cortex, the motor cortex, and the dorsolateral prefrontal cortex. </li></ul></ul>
    42. 42. Stages of Sleep And Brain Mechanisms <ul><li>REM sleep is also associated with a distinctive pattern of high-amplitude electrical potentials known as PGO waves . </li></ul><ul><li>Waves of neural activity are detected first in the pons and then in the lateral geniculate of the hypothalamus, and then the occipital cortex. </li></ul><ul><li>REM deprivation results in high density of PGO waves when allowed to sleep normally. </li></ul>
    43. 43. Fig. 9-13, p. 281
    44. 44. Stages of Sleep And Brain Mechanisms <ul><li>Cells in the pons send messages to the spinal cord which inhibit motor neurons that control the body’s large muscles. </li></ul><ul><ul><li>Prevents motor movement during REM sleep. </li></ul></ul><ul><li>REM is also regulated by serotonin and acetylcholine. </li></ul><ul><ul><li>Drugs that stimulate Ach receptors quickly move people to REM. </li></ul></ul><ul><ul><li>Serotonin interrupts or shortens REM. </li></ul></ul>
    45. 45. Stages of Sleep And Brain Mechanisms <ul><li>Insomnia is a sleep disorder associated with inability to fall asleep or stay asleep. </li></ul><ul><ul><li>Results in inadequate sleep. </li></ul></ul><ul><ul><li>Caused by a number of factors including noise, stress, pain medication. </li></ul></ul><ul><ul><li>Can also be the result of disorders such as epilepsy, Parkinson’s disease, depression, anxiety or other psychiatric conditions. </li></ul></ul><ul><ul><li>Dependence on sleeping pills and shifts in the circadian rhythms can also result in insomnia. </li></ul></ul>
    46. 46. Fig. 9-15, p. 282
    47. 47. Stages of Sleep And Brain Mechanisms <ul><li>Sleep apnea is a sleep disorder characterized by the inability to breathe while sleeping for a prolonged period of time. </li></ul><ul><li>Consequences include sleepiness during the day, impaired attention, depression, and sometimes heart problems. </li></ul><ul><li>Cognitive impairment can result from loss of neurons due to insufficient oxygen levels. </li></ul><ul><li>Causes include, genetics, hormones, old age, and deterioration of the brain mechanisms that control breathing and obesity. </li></ul>
    48. 48. Stages of Sleep And Brain Mechanisms <ul><li>Narcolepsy is a sleep disorder characterized by frequent periods of sleepiness. </li></ul><ul><li>Four main symptoms include: </li></ul><ul><ul><li>Gradual or sudden attack of sleepiness. </li></ul></ul><ul><ul><li>Occasional cataplexy - muscle weakness triggered by strong emotions. </li></ul></ul><ul><ul><li>Sleep paralysis- inability to move while asleep or waking up. </li></ul></ul><ul><ul><li>Hypnagogic hallucinations- dreamlike experiences the person has difficulty distinguishing from reality. </li></ul></ul>
    49. 49. Stages of Sleep And Brain Mechanisms <ul><li>(Insomnia cont’d) </li></ul><ul><li>Seems to run in families although no gene has been identified. </li></ul><ul><li>Caused by lack of hypothalamic cells that produce and release orexin. </li></ul><ul><li>Primary treatment is with stimulant drugs which increase wakefulness by enhancing dopamine and norepinephrine activity. </li></ul>
    50. 50. Stages of Sleep And Brain Mechanisms <ul><li>Periodic limb movement disorder is the repeated involuntary movement of the legs and arms while sleeping. </li></ul><ul><ul><li>Legs kick once every 20 to 30 seconds for periods of minutes to hours. </li></ul></ul><ul><ul><li>Usually occurs during NREM sleep. </li></ul></ul>
    51. 51. Stages of Sleep And Brain Mechanisms <ul><li>REM behavior disorder is associated with vigorous movement during REM sleep. </li></ul><ul><ul><li>Usually associated with acting out dreams. </li></ul></ul><ul><ul><li>Occurs mostly in the elderly and in older men with brain diseases such as Parkinson’s. </li></ul></ul><ul><ul><li>Associated with damage to the pons (inhibit the spinal neurons that control large muscle movements). </li></ul></ul>
    52. 52. Stages of Sleep And Brain Mechanisms <ul><li>“Night terrors” are experiences of intense anxiety from which a person awakens screaming in terror. </li></ul><ul><ul><li>Usually occurs in NREM sleep. </li></ul></ul><ul><li>“Sleep talking” occurs during both REM and NREM sleep. </li></ul><ul><li>“Sleepwalking” runs in families, mostly occurs in young children, and occurs mostly in stage 3 or 4 sleep. </li></ul>
    53. 53. Why Sleep? Why REM? Why Dreams? <ul><li>Functions of sleep include: </li></ul><ul><ul><li>Energy conservation. </li></ul></ul><ul><ul><li>Restoration of the brain and body. </li></ul></ul><ul><ul><li>Memory consolidation. </li></ul></ul>
    54. 54. Why Sleep? Why REM? Why Dreams? <ul><li>The original function of sleep was to probably conserve energy. </li></ul><ul><li>Conservation of energy is accomplished via: </li></ul><ul><ul><li>Decrease in body temperature of about 1-2 Celsius degrees in mammals. </li></ul></ul><ul><ul><li>Decrease in muscle activity. </li></ul></ul>
    55. 55. Why Sleep? Why REM? Why Dreams? <ul><li>Animals also increase their sleep time during food shortages. </li></ul><ul><ul><li>sleep is analogous to the hibernation of animals. </li></ul></ul><ul><li>Animals sleep habits and are influenced by particular aspects of their life including: </li></ul><ul><ul><li>how many hours they spend each day devoted to looking for food. </li></ul></ul><ul><ul><li>Safety from predators while they sleep </li></ul></ul><ul><ul><ul><li>Examples: Sleep patterns of dolphins, migratory birds, and swifts. </li></ul></ul></ul>
    56. 56. Fig. 9-17, p. 287
    57. 57. Why Sleep? Why REM? Why Dreams? <ul><li>Sleep enables restorative processes in the brain to occur. </li></ul><ul><ul><li>Proteins are rebuilt. </li></ul></ul><ul><ul><li>Energy supplies are replenished. </li></ul></ul><ul><li>Moderate sleep deprivation results in impaired concentration, irritability, hallucinations, tremors, unpleasent mood, and decreased responses of the immune system. </li></ul>
    58. 58. Why Sleep? Why REM? Why Dreams? <ul><li>People vary in their need for sleep. </li></ul><ul><ul><li>Most sleep about 8 hours. </li></ul></ul><ul><li>Prolonged sleep deprivation in laboratory animals results in: </li></ul><ul><ul><li>Increased metabolic rate, appetite and body temperature. </li></ul></ul><ul><ul><li>Immune system failure and decrease in brain activity. </li></ul></ul>
    59. 59. Why Sleep? Why REM? Why Dreams? <ul><li>Sleep also plays an important role in enhancing learning and strengthening memory. </li></ul><ul><ul><li>Performance on a newly learned task is often better the next day if adequate sleep is achieved during the night. </li></ul></ul><ul><li>Increased brain activity occurs in the area of the brain activated by a newly learned task while one is asleep. </li></ul><ul><ul><li>Activity also correlates with improvement in activity seen the following day. </li></ul></ul>
    60. 60. Why Sleep? Why REM? Why Dreams? <ul><li>Humans spend one-third of their life asleep. </li></ul><ul><li>One-fifth of sleep time is spent in REM. </li></ul><ul><li>Species vary in amount of sleep time spent in REM. </li></ul><ul><ul><li>Percentage of REM sleep is positively correlated with the total amount of sleep in most animals. </li></ul></ul><ul><li>Among humans, those who get the most sleep have the highest percentage of REM. </li></ul>
    61. 61. Fig. 9-18, p. 289
    62. 62. Why Sleep? Why REM? Why Dreams? <ul><li>REM deprivation results in the following: </li></ul><ul><ul><li>Increased attempts of the brain/ body for REM sleep throughout the night. </li></ul></ul><ul><ul><li>Increased time spent in REM when no longer REM deprived. </li></ul></ul><ul><ul><ul><li>Subjects deprived of REM for 4 to 7 nights increased REM by 50% when no longer REM deprived. </li></ul></ul></ul>
    63. 63. Why Sleep? Why REM? Why Dreams? <ul><li>Research is inconclusive regarding the exact functions of REM. </li></ul><ul><li>During REM: </li></ul><ul><ul><li>The brain may discard useless connections </li></ul></ul><ul><ul><li>Learned motor skills may be consolidated. </li></ul></ul><ul><li>Maurice (1998) suggests the function of REM is simply to shake the eyeballs back and forth to provide sufficient oxygen to the corneas. </li></ul>
    64. 64. Why Sleep? Why REM? Why Dreams? <ul><li>Biological research on dreaming is complicated by the fact that subjects can not often accurately remember what was dreamt. </li></ul><ul><li>Two biological theories of dreaming include: </li></ul><ul><ul><li>The activation-synthesis hypothesis. </li></ul></ul><ul><ul><li>The clinico-anatomical hypothesis. </li></ul></ul>
    65. 65. Why Sleep? Why REM? Why Dreams? <ul><li>The activation-synthesis hypothesis suggests dreams begin with spontaneous activity in the pons which activates many parts of the cortex. </li></ul><ul><ul><li>The cortex synthesizes a story from the pattern of activation. </li></ul></ul><ul><ul><li>Normal sensory information cannot compete with the self-generated stimulation and hallucinations result. </li></ul></ul>
    66. 66. Why Sleep? Why REM? Why Dreams? <ul><li>Input from the pons activates the amygdala giving the dream an emotional content. </li></ul><ul><li>Because much of the prefrontal cortex is inactive during PGO waves, memory of dreams is weak. </li></ul><ul><ul><li>Also explains sudden scene changes that occur in dreams. </li></ul></ul>
    67. 67. Why Sleep? Why REM? Why Dreams? <ul><li>The clinico-anatomical hypothesis places less emphasis on the pons, PGO waves, or even REM sleep. </li></ul><ul><ul><li>Suggests that dreams are similar to thinking, just under unusual circumstances. </li></ul></ul><ul><li>Similar to the activation synthesis hypothesis in that dreams begin with arousing stimuli that are generated within the brain. </li></ul><ul><ul><li>Stimulation is combined with recent memories and any information the brain is receiving from the senses. </li></ul></ul>
    68. 68. Why Sleep? Why REM? Why Dreams? <ul><li>Since the brain is getting little information from the sense organs, images are generated without constraints or interference. </li></ul><ul><li>Arousal can not lead to action as the primary motor cortex and the motor neurons of the spinal cord are suppressed. </li></ul><ul><li>Activity in the prefrontal cortex is suppressed which impairs working memory during dreaming. </li></ul>
    69. 69. Why Sleep? Why REM? Why Dreams? <ul><li>Activity is high in the inferior part of the parietal cortex, an area important for visual-spatial perception. </li></ul><ul><ul><li>Patients with damage report problems with binding body sensations with vision and have no dreams. </li></ul></ul><ul><ul><li>Activity is also high in areas outside of V1, accounting for the visual imagery of dreams. </li></ul></ul>
    70. 70. Why Sleep? Why REM? Why Dreams? <ul><li>Activity is high in the hypothalamus and amygdala which accounts for the emotional and motivational content of dreams. </li></ul><ul><li>Either internal or external stimulation activates parts of the parietal, occipital, and temporal cortex. </li></ul><ul><li>Lack of sensory input from V1 and no criticism from the prefrontal cortex creates the hallucinatory perceptions. </li></ul>