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Janelle Leboutillier

PSYB64: Introduction to Physiological Psychology Lecture 8: Sleep and Waking (Chapter 11) Overview  Circadian rhythms  Stages of wakefulness & sleep  Sleep over the lifespan  Dreaming  Functions of sleep  Brain mechanisms of wakefulness & sleep  Biochemistry of wakefulness & sleep  Sleep disorders Circadian Rhythms  Biological cycles can vary in length o Sleep-wakefulness cycle, about 24 hours o The human menstrual cycle, about a month o SAD (seasonal affective disorder)  Ultradian = rhythms shorter than 24 hours  Infradian = rhythms longer than 24 hours Circadian Rhythms  Zeitgebers o Any external cue that synchronizes an organism’s internal clock  Variations in Sleep Patterns o Night owls versus larks  Melatonin drops at onset of puberty; younger people tend to favour being an owl; change as we age  Shift Work, Jet Lag, and Daylight Saving Time o Shift maladaptation syndrome o Easier to adjust to a phase-delay than a phase-advance Circadian Rhythms  Shift Work, Jet Lag, and Daylight Saving Time o Shift maladaptation syndrome: o Easier to adjust to a phase-delay than a phase-advance  Daylight saving time in spring requires a phase advance, and can produce symptoms similar to jet lag. The time change in fall is equivalent to a phase delay, and causes little disruption for most people. Jet Lag is Worse When Traveling East (Figure 11.3)  Traveling eastward is more disruptive than traveling westward.  The Los Angeles resident arriving in New York feels like he or she is going to bed three hours earlier than usual (7 p.m. Los Angeles time) and waking up in the middle of the night (3 a.m. Los Angeles time).  The New Yorker traveling to Los Angeles has to stay up a little later (1 a.m. New York time) but then can sleep later to compensate (9 a.m. New York time). Most people find the latter scenario much easier. Video: Beating Jet Lag (25 hours); no external cue; no light 24 Hour Cycle of Melatonin Production  Produced 12am-6am (high level)  Hits peak at 2-4 am Melatonin  Give melatonin at night = no effect  Give melatonin in the day = sedative effect  One proposal, melatonin produces a phase advance  Has been used in clinical treatment for jet lag The Suprachiasmatic Nucleus (Figure 11.4)  The SCN is well situated to serve as the body’s master internal clock  Its proximity to the optic nerves provides necessary information regarding environmental light  Its links to other parts of the hypothalamus and to the pituitary and pineal glands allow the SCN to influence  rhythmic behaviors by controlling the release of hormones o SCN close to optic nerves providing information on light and to pituitary and pineal glands to influence behaviour through release of hormones The SCN is Active During the Day  SCN perceives the difference between day and night but does not dictate whether an animal is nocturnal or diurnal in its behaviour Suprachiasmatic Nucleus is the Master Pacemaker 1. Lesions of suprachiasmatic nucleus abolish free- running rhythms 2. Activity in suprachiasmatic nucleus correlates with circadian rhythms 3. Isolated suprachiasmatic nucleus continues to cycle 4. Transplanted suprachiasmatic nucleus imparts rhythm of the donor Circadian Rhythms  The Cellular Basis of Circadian Rhythms o Per, Tim, and Clock (genes and their protein products) o Watch video  Biochemistry and Circadian Rhythms o Melatonin  SCN regulates and responds to this hormone secreted by pineal body o Cortisol  This hormone also fluctuates with patterns of waking and sleeping  Also secreted during times of stress  Stress-induced high cortisol levels during the night are correlated with poor sleep quality Video: Cellular Clock Cycles of Protein Production and Degradation Form the Basis of the Cellular Clock in Fruit Flies (Figure 11.6) Body Temperature and Hormone Secretions Follow Circadian Rhythms (Figure 11.7)  Over the course of two days, we can see that body temperature and alertness are positively correlated  Growth hormone is released primarily during Stages 3 and 4 of NREM, whereas cortisol levels are highest first thing in the morning and decrease during the day Circadian Rhythms  Seasonal Affective Disorder o Type of depression associated with reduction in daylight hours during winter months o Exact cause unknown but serotonin levels decrease during the winter and affected individuals may be more susceptible in this reduction o Might also be influenced by disruptions in melatonin o Treatment with UV light therapy, melatonin, antidepressants Waking Up Teens: Delayed Sleep Phase Syndrome Stages of Wakefulness and Sleep  Wakefulness o Alterations between Beta wave and alpha wave activity  Brain Activity During Sleep o Alternating periods of rapid-eye-movement (REM) sleep and Non-REM (NREM) sleep o Stage 1 NREM– theta waves o Stage 2 NREM– sleep spindles, K-complex o Stage 3 NREM– some delta waves o Stage 4 NREM– 50 % delta waves o REM Ultradian Rhythms Characterize Wakefulness in Humans (Figure 11.8)  Not only do our REM cycles appear approximately every 90 to 120 minutes during sleep, but brain activity levels also ebb and flow in 90- to 120-minute intervals during wakefulness  Ultradian cycles = regular recurrence in cycles of less than 24 hours Human Sleep Cycles (Figure 11.10)  This image illustrates EEG patterns characteristic of wakefulness, REM, and the four stages of NREM  (b) EEG recordings show the cycling of sleep stages over an eight-hour period.  The first four hours contain most of the Stage 3 and Stage 4 NREM, and the second four hours contain most of the REM sleep Human Sleep Cycles  Regular bouts of REM sleep  Most deep NREM sleep is early in the sleep period Sleep Throughout the Life Span  Amount and composition of sleep changes over the lifespan  Infancy o 14-16 hours a day, 50 % time in REM  Puberty o 20 % of time in REM and also a substantial decrease in Stage 3 and 4 NREM  Adulthood o Sleep declines in midlife o NREM sleep continues to decline o Around 50 total sleep time begins to decrease by about 27
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