Sleep_Student Upload_NoAudio.pptx

The Biological Psychology of Sleep, and Dreaming Biopsychology Lecture 8 Blair Saunders Sleeping seems to be important Outside of the work-place, sleep is probably the most timeconsuming human activity Humans sleep roughly 6-8 hours per day = 25-33% of our life sleeping. If you live to 78 years o...

The Biological Psychology of Sleep, and Dreaming Biopsychology Lecture 8 Blair Saunders Sleeping seems to be important Outside of the work-place, sleep is probably the most timeconsuming human activity Humans sleep roughly 6-8 hours per day = 25-33% of our life sleeping. If you live to 78 years old, you have spent 19-26 of those years sleeping !! Cats sleep through more than half of their lives! (50-67%) To take up so much time, sleep must be really important! How does UK sleep compare to other nations? 6 hrs = 360 mins; 7hrs = 420; 8hrs = 480 mins; 9hrs = 540 mins Today’s goals Overall objective: To understand the psychology and biology of sleep, and how sleep relates to health. Theme 1: Introduction to sleep Define Sleep Describe how sleep is studied in the lab. Differentiate the stages of sleep using EEG, EMG, and EOG Evaluate the claim that REM sleep is correlated with dreaming Theme 2: Sleep Deprivation Evaluate evidence that sleep deprivation is associated with cognitive impairments Discuss the effects of REM on non-REM sleep deprivation Evaluate evidence that sleep deprivation has longer-term detrimental consequences for health The Biological Psychology of Sleep, and Dreaming Biopsychology Lecture 8 Blair Saunders Part1: Introduction to the scientific study of sleep Circadian Rhythms Most organisms cycle between periods of alertness and inactivity that follows an approximately 24 hr cycle These are called circadian rhythms Circadian Rhythms (from the Latin circa, “about” and dies, “day”) Circadian Rhythms Patterns of alertness and inactivity are not driven directly by light, but by evolutionary niche adaptations Diurnal Rhythm: active most during the day Nocturnal Rhythm: active during dark periods Definition of sleep What does it mean to be asleep? Definition of sleep (Siegel, 2008) 1) Rapidly reversible state of immobility and greatly reduced sensory responsiveness 2) Sleep is homeostatically regulated (lost sleep  sleep rebound) Circadian patterns of alertness and inactivity do not always diagnose sleep! • • Bullfrogs show circadian patterns of activity and inactivity More reactive to external stimulation during inactive periods How is sleep studied in the lab? Key problems • Psychology studies of sleep are difficult because the participant is not responsive while they sleep • People normally sleep in the comfort of their own homes— sleeping is a very private activity Solution: Take a range of physiological measures using a range of sensors and have people sleep in a sleep lab Problems with these methods? Methods of the Sleep lab Electroencephalography (EEG). Measures electrical activity on the scalp arising from the synchronous activity of large populations of (mainly cortical) neurons Methods of the Sleep lab Electroencephalography (EEG). Measures electrical activity on the scalp arising from the synchronous activity of large populations of (mainly cortical) neurons Jackson & Bolger (2014), Psychophysiology Understanding continuous EEG Electroencephalography (EEG) Commonly defined by frequency (Hz), Amplitude (V) (>32 Hz) (16-31 Hz) (8-15 Hz) (4-8 Hz) (< 4 Hz) Electromyography and Electrooculography Electromyography (EMG) Measures electrical activity cause by muscle contractions Assesses changes in muscle activity as a proxy for tension and relaxation during sleep Electrooculography (EOG) Measures eye electrical activity associated with eye movements (e.g., blinks, lateral eye movements). Stages of stages and cycles Wakefulness Beta Activity (16-31 Hz) • • Rapid, low voltage, irregular oscillations Recorded above most brain locations Alpha Activity (8-15 Hz) • • • • Higher voltage and lower frequency than beta Observed primarily over posterior regions Modulated by eye-closing Relaxed and resting brain state? Wake EEG often oscillates between alpha and beta activity, while neither activity is observed much during sleep Stages 1 & 2 - 45-50% Stage 1 • • Lowering of EEG frequency Lowered heart rate and reduction of muscle tension Stage 2 • • • Similar to stage 1 with some additional features Sleep spindles (periodic 12-14 Hz bursts) K-complexes If awakened during initial stages 1-2 people will often deny that they are sleeping Slow-Wave Sleep (stages 3 & 4) – 15-20 % Slow wave sleep • • • • • Dominated by delta activity. EEG waveforms are slow and high amplitude Deepest form of sleep with lowest ability to generate arousal Reduced heartrate and respiration Muscle relaxation, but movement still occurs Increased parasympathetic nervous system activity (i.e., rest and digest) Is slow wave sleep particularly restorative? Rapid Eye Movement (REM) Sleep – 20-25% Characteristics of REM sleep • • • Low amplitude, high frequency EEG activity (like wakefulness) Associated with fast rapid eye movements (Electrooculography) Loss of tone (i.e., relaxation) of core muscles Other correlates of REM sleep • • • • Brain activity (blood flow, neural firing) increases to waking levels. Increased variability in heart rate, blood pressure, breath rate Twitching of muscles at the extremities Penile erection in males, pelvic thrusting and uterine contractions in females REM sleep looks very different from other sleep stages? Looks like a state of high arousal/emotion. What might the function of REM be? REM sleep and dreaming The pseudoscience of dreaming The interpretation of dreams has a long and unscientific past in psychology Tell me about your dreams? Now, did those dreams happen during REM sleep? REM and Dreaming: Method Sleep-stages follow physiologically distinct physiological patterns of activity Tell me about your dreams? Tell me about your dreams? Tell me about your dreams? REM and Dreaming: Early Studies Is REM the physiological correlate of dreaming? Early evidence appeared to support this idea: • 80% of awakenings from REM sleep accompanied by dream re-call • Only 7% of non-REM sleep associated with dreams recall. • Non-REM sleep associated with more general feelings (e.g., falling) REM = Dreams: Counterevidence Non-dreamers • • Many people often recall no dreams after sleeping Yet, these people have normal REM sleep cycles How reliable is this evidence? It could be that REM sleep is necessary, but not sufficient for dreams Antidepressants suppress REM sleep • • Taking anti-depressants greatly reduces or abolishes REM sleep People taking antidepressants do not report reduced rates of dreaming REM = Dreams: Counterevidence REM and Dreaming depend on different brain areas • • • • REM sleep is generated largely in the pontine brainstem Lesions to this brain area typically abolish REM sleep Lesions to pontine brain stem do not abolish dreaming Loss of dreaming and preserved REM sleep is observed with lesions to PTJ and VM frontal lobes Theme 2: The function of sleep Recall that we spend almost a third of our lives sleeping. This is so much more time than almost any other survival-related activities We spend more time sleeping than: • Eating & Drinking • Having Sex • Exercising Given this time allocation, sleep must be important. Let’s think about the function of sleep… Theories of Sleep Recuperation Theory • • • • Being awake depletes energy resources in some way, and sleeps helps us to return to normal baseline levels (i.e., sleep maintains homeostasis). Explains why lack of sleep is often recovered after sleep deprivation Slow-wave sleep in particular activates the bodies “rest-and-digest” systems (reduced heart rate, respiration, increased digestion). Similar to set-point theory of hunger! Recuperation Theory: Mechanism Theories of Sleep Adaptation Theory • Evolutionary theory • Sleep is associated with reduced metabolic costs than being awake (sleep conserves energy) • Sleep can help to enforce evolutionary niche (nocturnal or diurnal?) Human example: Human’s are not well adapted to life in the dark We experience increased risk of predation and other mishaps at night. • Being awake and moving around burns energy (calories) Humans can get all the eating and procreating they need to do during the day, better to sleep at night to conserve resources. • No set-point in adaptation theories • • We are motivated to sleep, but we don’t need it to survive (EXTREME VIEW) Sleep schedules should be modifiable – we don’t need x amount of sleep given wakefulness Comparative Analysis of Sleep If sleep is driven more by evolutionary pressures than by restoration needs, then we should see great variation in sleeping patterns across species How do we define and measure sleep in non-human animals? Definition of sleep (Siegel, 2008) 1) Rapidly reversible state of immobility and greatly reduced sensory responsiveness 2) Sleep is homeostatically regulated (lost sleep  sleep rebound) Class exercise! Think ahead. Are there some evolutionary pressures that mean that certain animals can sleep a lot, and other can afford to sleep less? Comparative Analysis of Sleep 2-3 Hrs 15-18 Hrs ?? Hrs 0 Hrs 19-20 Hrs 6-8 Hrs 24 Hrs Sleep is hugely variable across (and sometimes within) species! Adaptation to environmental demands, rather than set time for recuperation? Break The Biological Psychology of Sleep, and Dreaming Biopsychology Lecture 8 Blair Saunders Part2: Sleep deprivation and health The Effects of Sleep Deprivation What can we learn from the scientific study of sleep deprivation? Animal Studies of Extreme Sleep Deprivation Carousel Apparatus: Used to deprive rats of sleep over long time periods Experimental rat when EEG signals sleep, platform rotates and knocks animal into water Yoked control Rat subjected to same rotations as experimental, but not tied to this rat’s sleep Result Experimental rat dies after about 12 days So does sleep deprivation kill?? Stress confound Post-mortems reveal swollen adrenal glands, gastric ulcers, and internal bleeding. The rats died from stress, not lack of sleep It is very difficult to do sleep studies in animals for these reasons The Effects of Sleep Deprivation Logic: We can learn about the function of sleep by assessing the effects of sleep deprivation in humans Confounding Factors Stress We often lose sleep because of some other stressor • • • • Problems at work Relationship breakdown Illness Personal finances Ill-health attributed to sleeping may often be caused by the co-occurring stress Sleep Deprivation Studies in Humans Experimental studies: Participants are prevented from sleeping—ranges from reduced sleep schedules to total sleep deprivation. Next day assessment of sleepiness, mood, cognitive function, performance, physiology, and so forth. Reliable effects of sleep deprivation: 1) Increased self-reported sleepiness (people feel drowsy and desire sleep) 2) Increased Negative affect/ bad mood These findings are consistent with the idea that sleep has a replenishing effect between days. Sleep Deprivation in Humans Does poor sleep impair cognitive processing? • • If we don’t sleep properly, we sometimes feel like we can’t think straight. We might make some bad decisions when we are tired. Sleep Deprivation and Decision Making Iowa Gambling task: A test of risky decision making http:// www.psytoolkit.org/experiment-libra ry/igt.html Frontal lobe damage and IGT • • • Frontal brain damage—particularly in ventromedial prefrontal cortex—is often associated with the more persistent selection of “bad decks” Patients with vmPFC damage often show increased anger and frustration, and less empathy and compassion Sleep deprivation, it has been suggested, leads to reduced activity in vmPFC Killgore et al., 2006. Does sleep deprivation have a negative impact on decision making in the IGT? Study 48 participants who performed IGT at baseline and then again after experimenters kept them awake for 49 hours Better decision making  Sleep Deprivation and Decision Making Sleep Deprivation and Executive Function Executive Functioning: A range of mental processes that allow us to inhibit impulsive actions, switch between tasks, and update plans Executive Functions also depend on frontal brain regions, including the lateral and medial prefrontal cortex. Evidence also suggests that very long periods of total sleep deprivation are associated with impaired executive functioning. HOMEWORK EXERCISE The deprivation of specific sleep stages Question: Do specific sleep stages have specific functions? Can these functions be assessed by periodically waking people when they fall into a given sleep stage? Let’s explore this idea with: 1) REM sleep 2) Slow-wave sleep REM-Sleep Deprivation (recap) Characteristics of REM sleep • • • Low amplitude, high frequency EEG activity (like wakefulness) Associated with fast rapid eye movements (Electrooculography) Loss of tone (i.e., relaxation) of core muscles (Electromyography) Other correlates of REM sleep • • • • Brain activity (blood flow, neural firing) increases to waking levels. Increased variability in heart rate, blood pressure, breath rate Twitching of muscles at the extremities Penile erection in males, pelvic thrusting and uterine contractions in females Will selectively depriving people of REM sleep help us to learn more about this intriguing sleep stage? REM Rebound REM sleep is clearly important REM sleep is homeostatically regulated— we adapt our sleep to preserve it Does REM contribute to daytime alertness/sleepiness? Nykamp et al. (1998). Sleep lab study with 26 healthy volunteers who were tested in a sleep lab over 5 consecutive days. • • • • Night and Day 1: Screening Night and Day 2: Baseline Sleep Measures Nights 3&4, and Day 3&4: Deprivation of either REM sleep (experimental group) or non-REM sleep (control group) Night and day 5: Recovery Daytime sleepiness was measured using the Multiple Sleep Latency Test (MSLT). • • • People take 5 scheduled naps per day in the sleeping lab, separated by 2 hour blocks Participants are only allowed to sleep for max 15 minutes per nap. Latency to fall asleep is used as the dependent measure Do you think REM sleep deprivation will increase or decrease latency to nap? Does REM contribute to daytime sleepiness? Nykamp et al. (1998). Does REM contribute to daytime sleepiness? Nykamp et al. (1998). Default theory of REM sleep Theory: It is difficult/potentially dangerous to stay in slow-wave sleep (e.g., stages 3-4) for long periods of time. To ease this difficulty, body switches to easier sleep stages (e.g. REM) or wakefulness periodically “Return to wakefulness if I have immediate needs (e.g., eat, drink,… pee?” “REM = awake-like state that is less costly if I have no bodily needs Slow-wave Sleep Deprivation Recap Slow wave sleep • • • • • • Dominated by delta activity. EEG waveforms are slow and high amplitude Deepest form of sleep with lowest ability to generate arousal Reduced heartrate and respiration Muscle relaxation, but movement still occurs Increased parasympathetic nervous system activity (i.e., rest and digest) Xie et al. (2013)—removal of toxic waste from the brain tends to happen in slow-wave sleep Is slow wave sleep particularly restorative? Slow-Wave Sleep and sleep deprivation Slow-wave sleep is particularly protected when sleep duration is short Short sleepers—people who sleep < 6 hours per night—tend to get as much slow-wave sleep as people who sleep longer Reducing sleep time usually results in a reduction in sleep Stages 1&2, but not in slow wave sleep Daytime naps after a full nights sleep typically do not involve much slow-wave sleep Conclusion? Sleep deprivation  increased sleep efficiency, where slow-wave sleep is prioritised. Suggests that slow wave sleep might be particularly important/restorative Sleep and Health How much sleep do we need to be healthy? Is there a direct answer to this question? Sleep shows a high degree of plasticity. Plasticity in sleep efficiency means that people can adjust to some degree of sleep deprivation Natural variation in sleep duration, and long-term sleep reduction Acute sleep deprivation (sleeping less than you are used to) makes people feel tired and unhappy the next day Without this deliberate intervention, however, there is great variation in how much people sleep. Some people are long sleepers (e.g., sleeping >8 hours/night) Others are short sleepers (e.g., sleeping 6 or less hours/night) In humans, if longer sleep  better health, we would expect socalled short sleepers to experience worse overall health and wellbeing. Differences between long and short sleepers Fichten et al. (2004) Large sample of short and long sleepers (N = 239) Compared long (>8hrs) and short (<6hrs) sleepers on 48 dimensions: Daytime sleepiness Daytime naps Stress & Anxiety Busyness Overall life satisfaction And, screened participants with potentially confounding factors (e.g., illness, external stress) Result: Long and short sleepers did not differ on any measure of health and wellbeing Problems? Correlational design means that other unaccounted for factors might explain the preserved health in short sleepers. Experimental interventions are needed! Long-term reduction of nightly sleep Other studies have experimentally investigated the long-term effect of sleep reduction on health and cognitive function Volunteers (N=16) slept for 5.5 hours/night for 60 days, then completed extensive battery of mood, medical, and performance tests (Webb & Agnew, 1974) Only one slight deficit on a test of auditory vigilance Volunteers (N=8) reduced sleep over 9 weeks, then sustained a reduced sleep duration (4.5-5.5 hrs/night) over a year (Friedman et al., 1997) • • • Sleep efficiency increased over time in all participants (i.e., higher proportion of slow-wave sleep) No deficits emerged on medical, mood, or performance tests as a function of reduced sleep over time Consistent with the plasticity of sleep—sleep efficiency increases when less time is available to sleep Problems? Sample sizes might limit generalizability. Would people who can cope with reduced Effects of shorter sleep times on health “Ok, the USA is definitely not one of the healthiest countries!” Wait, Japan, Norway, and Sweden are not “unhealthy countries?” N! ! O I AT ! L E R G! R N O I C RN WA 6 hrs = 360 mins; 7hrs = 420; 8hrs = 480 mins; 9hrs = 540 mins Long-term epidemiological study of sleep and health Tamakoshi and Ohno (2004): Tracked 104, 010 volunteers over 10 years Started with healthy sample (excluded those with ill-health, depression, significant stress) Correlational  does not prove that sleeping > 8 hours is deadly. But does indicate that sleeping 6-7 hours is not a significant health risk Summary Define sleep and the various stages of sleep, with reference to the measures that are used to identify sleep stages in the lab (EEG, EOG, EMG). Compare and contrast the adaptive and recuperative view of sleep Critically evaluate the claim that REM sleep is the physiological correlate of dreaming Understand the relationship between deprivation sleep and human functioning. Is there an optimal amount of sleep that we should get? What do studies of sleep deprivation tell us about the function of various sleep stages? L5 Questions 1 Differentiate REM sleep from slow-wave sleep with explicit reference to EEG, EOG, and EMG methodologies. 2 Describe the influence of sleep deprivation on performance of the Iowa Gambling task, making comparison to participants with ventromedial prefrontal cortex lesions.