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Ppt Chap 9

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  • 1. Chapter 9 Wakefulness and Sleep
  • 2. Rhythms of Waking and Sleep <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. 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><li>Animals generate endogenous 24 hour cycles of wakefulness and sleep. </li></ul><ul><ul><li>Also regulates the frequency of eating and drinking, body temperature, secretion of hormones, urination, and sensitivity to drugs. </li></ul></ul>
  • 4. Rhythms of Waking and Sleep <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>
  • 5. 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>Human circadian clock generates a rhythm slightly longer than 24 hours when it has no external cue to set it. </li></ul><ul><li>Resetting our circadian rhythms is sometimes necessary. </li></ul>
  • 6. Rhythms of Waking and Sleep <ul><li>Free-running rhythm is a rhythm that occurs when no stimuli resets it. </li></ul><ul><li>A zeitgeber is a term used to describe any stimulus that resets the circadian rhythms. </li></ul><ul><li>Light is the primary one. </li></ul><ul><li>Exercise, noise, meals, and temperature are others zeitgebers. </li></ul>
  • 7. 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>
  • 8.  
  • 9. Rhythms of Waking and Sleep <ul><li>Circadian rhythms remain consistent despite lack of environmental cues indicating the time of day </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>People who engage in shift work often fail to adjust completely. </li></ul>
  • 10. 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>
  • 11. 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>
  • 12.  
  • 13. Rhythms of Waking and Sleep <ul><li>The SCN generates circadian rhythms in a genetically controlled, unlearned manner. </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>
  • 14. 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>
  • 15.  
  • 16. 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>
  • 17.  
  • 18. 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>
  • 19. 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>
  • 20. Stages of Sleep And Brain Mechanisms <ul><li>Sleep is a state that the brain actively produces. </li></ul><ul><li>Characterized by a moderate decrease in brain activity and decreased response to stimuli. </li></ul><ul><li>Sleep differs from the following states: </li></ul><ul><ul><li>Coma </li></ul></ul><ul><ul><li>Vegetative state </li></ul></ul><ul><ul><li>Minimally conscious state </li></ul></ul><ul><ul><li>Brain death </li></ul></ul>
  • 21. Stages of Sleep And Brain Mechanisms <ul><li>Coma – extended period of unconsciousness caused by head trauma, stroke, or disease characterized by low brain activity that remains fairly steady </li></ul><ul><ul><li>Person shows little response to stimuli </li></ul></ul><ul><li>Vegetative state – person alternates between periods of sleep and moderate arousal but no awareness of surrounding </li></ul><ul><ul><li>Some autonomic arousal to painful stimulus </li></ul></ul><ul><ul><li>No purposeful activity/ response to speech </li></ul></ul>
  • 22. Stages of Sleep And Brain Mechanisms <ul><li>Minimally conscious state - one stage higher than a vegetative state marked by occasional brief periods of purposeful action and limited speech comprehension </li></ul><ul><li>Brain death - no sign of brain activity and no response to any stimulus </li></ul>
  • 23. 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>Allows researchers to compare brain activity at different times during sleep. </li></ul><ul><li>A polysomnograph is a combination of EEG and eye-movement records </li></ul>
  • 24.  
  • 25. 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>
  • 26. 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-complex - a sharp high-amplitude negative wave followed by a smaller, slower positive wave. </li></ul></ul>
  • 27. 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>
  • 28. 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 know as paradoxical sleep 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>
  • 29.  
  • 30. 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>
  • 31. 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>
  • 32.  
  • 33. 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>
  • 34. 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>
  • 35. 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>
  • 36.  
  • 37. Structure Neurotransmitter(s) it releases Effects on Behavior Pontomesencephalon Acetylcholine, glutamate Increases cortical arousal Locus coeruleus Norepinephrine Increases information storage during wakefulness; suppresses REM sleep Basal forebrain Excitatory cells Acetylcholine Excites thalamus and cortex; increases learning, attention; shifts sleep from NREM to REM Inhibitory cells GABA Inhibits thalamus and cortex Hypothalamus (parts) Histamine Increases arousal (parts) Orexin Maintains wakefulness Dorsal raphe and pons Serotonin Interrupts REM sleep
  • 38. 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>
  • 39. 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>
  • 40. 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 basal forebrain to stimulate neurons responsible for wakefulness and arousal. </li></ul></ul><ul><ul><li>The basal forebrain is an area just anterior and dorsal to the hypothalamus </li></ul></ul>
  • 41. Stages of Sleep And Brain Mechanisms <ul><li>Functions of the inhibitory neurotransmitter GABA are also important: </li></ul><ul><ul><li>Decreasing the temperature and metabolic rate </li></ul></ul><ul><ul><li>Decreasing stimulation of neurons. </li></ul></ul>
  • 42. Stages of Sleep And Brain Mechanisms <ul><li>During REM sleep: </li></ul><ul><ul><li>Activity increases in the pons (triggers on set of REM sleep) and limbic system (emotional systems), parietal cortex and temporal cortex. </li></ul></ul><ul><ul><li>Activity in the pons triggers onset of REM sleep </li></ul></ul><ul><ul><li>Activity decreases in the primary visual cortex, the motor cortex, and the dorsolateral prefrontal cortex. </li></ul></ul>
  • 43. 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>
  • 44.  
  • 45. 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 REM. </li></ul></ul>
  • 46.  
  • 47. Stages of Sleep And Brain Mechanisms <ul><li>Insomnia is a sleep disorder associated with inadequate sleep. </li></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>
  • 48.  
  • 49. 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 may 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>
  • 50.  
  • 51. 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>
  • 52. 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>
  • 53. 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>
  • 54. 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>
  • 55. 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>
  • 56. 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>
  • 57. 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>
  • 58. 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>
  • 59.  
  • 60. Why Sleep? Why REM? Why Dreams? <ul><li>Sleep enables restorative processes: </li></ul><ul><ul><li>Proteins rebuilt in the brain </li></ul></ul><ul><ul><li>Energy supplies replenished </li></ul></ul><ul><li>Moderate sleep deprivation results in impaired concentration, irritability, hallucinations, tremors, unpleasant mood, and decreased immune system functioning. </li></ul><ul><li>Caffeine increases arousal by blocking the receptors for adenosine (accumulate during wakefulness and increase drowsiness) </li></ul>
  • 61. 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>
  • 62. 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>
  • 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.  
  • 65. 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>
  • 66. 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>
  • 67. 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>
  • 68. 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>
  • 69. 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>
  • 70. 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>
  • 71. 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>

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