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Lecture 2b.docx

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PSYC 2800
Amanda Helleman

Lecture 2b *final+ What Does Sleep Accomplish? Sleep As a Biological Adaptation • Sleep is an energy-conserving strategy – Gather food at optimal times and sleep to conserve energy the rest of the time. Conserve energy so can hunt for food at appropriate time – Animals with nutrient-rich diets spend less time foraging for food and more time sleeping • Animals that are predators sleep more than animals that are prey (can’t afford because may get attacked) • Nocturnal or diurnal animals will sleep during those times in which they cannot travel easily – Example: Humans can’t see well at night so active during daytime – Strangely possums sleep 19 hours a day but not carnivores • Sleep As a Biological Adaptation • Basic Rest-Activity Cycle (BRAC) – Recurring cycle of temporal packets, about 90 minute periods in humans, during which an animal’s level of arousal waxes and wanes – Activity and rest – Examples: School classes, work periods, meal times, NREM-REM cycles, all around 90 minutes – Cycles so fundamental that it cannot be turned off even at night, so the body is paralyzed during REM sleep to prevent interruptions throughout sleep – Actual circadian rhythms controlled by cortisol, which doesn’t have 90 minute cycle. Low= inactive. • Sleep As a Restorative Process • Sleep not adaptive but restorative • Possible Hypotheses – Chemical events that provide energy to cells may be reduced during waking and are replenished during sleep BUT – Fatigue and alertness may simply be aspects of the circadian rhythms and have nothing to do with wear and tear on the body - Evidence conflicting • Sleep Deprivation • Recuperative/restorative theories make specific predictions about sleep deprivation: – Long periods of wakefulness will produce physiological and behavioural disturbances – Disturbances will grow steadily worse as deprivation continues – After a period of deprivation has ended, much of missed sleep will be regained (rebound). Ex: Miss 2 nights sleep, third night sleep longer to make up for it • Case of Randy Gardner • 1965 Science Fair project • Stayed awake for 264 hours (about 11 days) – Long periods of wakefulness will produce physiological and behavioral disturbances • True. Cognitive capabilities in decline, ability to access info, short term memory, response times all affected – Disturbances will grow steadily worse as deprivation continues • True. – After a period of deprivation has ended, much of missed sleep will be regained • No. After 11 days, slept 8-10 hours and that’s all • Restorative theory not all together accurate • What are you own experiences? Most people who sleep irregularly or little, do so because they are under stress • N.B.: Shift workers/Jet lag  forced to do so (sleep deprivation), circadian rhythms altered. Can have significant impacts on health. • We also either under- or over-estimate the effects of sleep deprivation in ourselves. • Tend do overestimate how much sleep deprivation we have (enter stage 1 without realizing when toss and turn). • Short term sleep deprivation can alleviate depression. Disrupted cortisol in depression. • Sleep Deprivation: Studies • Usually self report, memory tasks, motor tasks • Measures: Sleepiness, mood, cognition, motor performance, physiological function (eyemovement, hormones, etc.) • Complete deprivation – 3 or 4 days max (more unethical) – Negative effects on mood, cognitive and perceptual-motor tasks – Engage in microsleeps because so deprived – Microsleeps : 2-3 sec; eyelids droop, less responsive to external stimuli • Sleep Deprivation: Studies • Partial deprivation or sleep restriction (e.g., 3-4 h/night) – Three consistent effects: • Increased sleepiness • Disturbances in mood • Perform poorly on tests of vigilance / impaired attention, reaction time, coordination, and decision making – Worse if subjects performing long-lasting, difficult, monotonous tasks; < 5h/night – Accidents: Three Mile Island (nuclear plant), Chernobyl, Exxon Valdez (oil spill) may be due to sleep deprivation – Sleep deprived surgeons, increasing error • REM-Sleep Deprivation • Little effect on daytime functioning! • Two consistent effects: – With each successive night of deprivation, greater tendency to initiate REM sequences; 17 v 67 times! – Rebound effect: Following REM deprivation, have more than usual amount of REM for 2-3 nights (not increased overall sleep but spend more time in REM) – Similar effects with Slow Wave Sleep • Suggests amount of REM regulated separately from slow-wave sleep • REM-Sleep Deprivation Studies • Appear to be no adverse e
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