WEEK 1 - 4 Flashcards

Question

Why do we sleep?

Answer 1

- sleep serves a similarly critical role in our health and well-being. - sleep makes us feel better - We feel more alert, more energetic, happier, and better able to function following a good night of sleep - Both eating and sleeping are regulated by powerful internal drives - going without sleep makes us feel overwhelmingly sleepy Inactivity Theory: aka adaptive or evolutionary theory - One of the earliest theories of sleep - suggests that animals that we're able to stay still and quiet during these periods of vulnerability had an advantage over other animals that remained active - Through natural selection, this behavioural strategy presumably evolved to become what we now recognize as sleep Counter-argument: - it is always safer to remain conscious in order to be able to react to an emergency (even if lying still in the dark at night) - there does not seem to be any advantage of being unconscious and asleep if safety is paramount Energy Conservation Theory: - one of the strongest factors in natural selection is competition for and effective utilization of energy resources - the primary function of sleep is to reduce an individual’s energy demand and expenditure during part of the day or night, especially at times when it is least efficient to search for food - energy metabolism is significantly reduced during sleep (by as much as 10 percent in humans and even more in other species) - both body temperature and caloric demand decrease during sleep, as compared to wakefulness - sleep is to help organisms conserve their energy resources Restorative Theories: - based on the long-held belief that sleep in some way serves to "restore" what is lost in the body while we are awake - Sleep provides an opportunity for the body to repair and rejuvenate itself - animals deprived entirely of sleep lose all immune function and die in just a matter of weeks - the major restorative functions in the body like muscle growth, tissue repair, protein synthesis, and growth hormone release occur mostly, or in some cases only, during sleep - Other rejuvenating aspects of sleep are specific to the brain and cognitive function - while we are awake, neurons in the brain produce adenosine, a by-product of the cells' activities - The build-up of adenosine in the brain is thought to be one factor that leads to our perception of being tired = this build-up of adenosine during wakefulness may promote the "drive to sleep." - As long as we are awake, adenosine accumulates and remains high - During sleep, the body has a chance to clear adenosine from the system, and, as a result, we feel more alert when we wake Brain Plasticity Theory: - One of the most recent and compelling explanations for why we sleep - brain plasticity = its connection to sleep has several critical implications - sleep plays a critical role in brain development in infants and young children - Infants spend about 13 to 14 hours per day sleeping, and about half of that time is spent in REM sleep, the stage in which most dreams occur - A link between sleep and brain plasticity is becoming clear in adults as well = This is seen in the effect that sleep and sleep deprivation have on people's ability to learn and perform a variety of tasks

Answer 2

- Sleep, or at least a daily period of rest, has likely been part of life since the beginning of evolutionary time - sleep patterns have changed over the centuries, even if our need for sleep has not - people have gone to great lengths to make sleep more comfortable and safer, or to incorporate sleep into their lives to a greater or lesser extent

Answer 3

- enter sleep by going into stage 1 - you progress into stage 2, 3, and 4 = deepest stages of sleep - in a young healthy sleeper, about 30-40 mins after they fall asleep they are in a very deep state - then you come up to a very brief REM sleep - overnight there is an alternation bwt deep NREM and lighter REM sleep - sometimes at the end of REM sleep there's a brief awakening, but ppl typically go back to sleep quickly - over the course of the night the REM periods become progressively longer and the dreams get more intense - usually by 7 or 8 am if you awaken spontaneously, you make awaken at the end of the REM sleep period, often recalling the dream you just had

Answer 4

False What is nocturnal lagophthalmos? - the inability to close the eyelids during sleep

Answer 5

True We continue to be aware of our surroundings in some stages of sleep, but the degree of awareness of our environment changes depending on what stage we are in

Answer 6

FALSE Humans are not all pre-disposed to sleep at night. Although most people are diurnal (i.e., they are awake during the day and asleep during the night), there are a few people who are genetically pre-disposed to sleep during the day and be awake at night. This is a circadian rhythm problem

Answer 7

- Sleep is a state of consciousness that differs from wakefulness in the capacity for attention and in physical responsiveness - there are many activities that occur during sleep which would suggest that it is not entirely a passive state ex. memory consolidation in REMS and tissue restoration in slow-wave sleep

Answer 8

- sleep occurs in stages; often they occur in a reliable sequence but it is not unusual to go from stage 2 sleep (N2) to REMS to N2 to stage 1 sleep (N1) in a given period of time - although sleep typically follows a pattern across the night (e.g., N1, N2, stage 3 sleep (N3), REMS), there is flexibility - Sleep is categorized mainly into rapid eye movement sleep (REMS) and non-REM Non-REM (NREM): - has three stages associated with it: N1, N2, and N3, also called delta sleep or slow wave sleep (SWS) because of the wave forms - NREM sleep is what most typically think of when they think of sleep - it is not uncommon for people to be in N1 or even N2 and deny they were asleep when woken up - In N2, people are able to be roused by loud, or personally relevant stimuli like their crying infant or someone saying their name - In N3, sleep is deep and it is difficult to be awoken REM: - used to be called paradoxical sleep because the brain activity looks more like wakefulness than sleep - During REMS the eyes dart back and forth under the eyelids, and muscles responsible for the control of movements are paralyzed - People most often associate this with the “dreaming” state, however dreaming occurs in other stages as well - Laypeople often mistakenly believe that REMS is responsible for feeling rested, but there is little evidence to support this notion

Answer 9

- increase in growth hormone release at night - Growth hormone restores tissues, and depriving the body of this hormone via sleep deprivation can produce myalgias (e.g., aches and pains) which suggests that sleep mitigates against “wear and tear” pain - we do not heal as well when we are sleep-deprived - there is some evidence against sleep having primarily a tissue regenerative function = One argument is the relative lack of physical damage in humans after several days of deprivation - although we see growth hormone release, we also see less protein synthesis during sleep = tissue restoration may be one function of sleep, but is not the sole function of sleep

Answer 10

- memory and learning processes continue after you fall asleep; more specifically, memories, including those formed as a result of learning, are consolidated during sleep - There is also a pruning away of unimportant information = “we may both sleep to remember and sleep to forget” (Moorcroft, p. 240). - advanced animals, including humans, sleep for cognitive purposes - sleep deprivation has a negative effect on memory - there are observable sleep-related changes (e.g., REMS becomes denser) following learning - animal studies that record brain activity during learning find that during sleep, the areas and patterns of brain activity during the learning task are “replayed” during sleep - there is mixed evidence for whether REMS or NREM is responsible for these processes - Some deprivation studies fail to show memory or learning deficits; and how can we explain why REMS is high in fetuses but decreases significantly after birth—a time in which one would expect learning is very important?

Answer 11

- we are most active during the daylight - Our senses are most optimal during the daylight and thus it is most advantageous to gather food at this time, and it may be most safe for us to sleep during the night - The opposite is true for nocturnal creatures - one could always argue that we are sleeping at a time in which we are most vulnerable, so this hypothesis may not be the whole story either

Answer 12

- The PSG integrates multiple indices to quantify physiologic processes during sleep - PSG is a gold standard method for measuring sleep objectively; that is, the same scoring criteria are applied for every patient It integrates brain wave activity from: - the electroencephalogram (EEG) the brain waves are characterized by irregular, fast waves such as beta During beta, the frequency is above 13 hertz (Hz) - muscle tone from the electromyogram (EMG) and EMG line has a thickness to it because the muscles are active - eye movements on the electro-oculogram (EOG) characterized by blinking - The electrical activity from these measures is displayed on the computer screen in 30-second segments and decisions about sleep stages are made on the basis of these 30-second segments, or “epochs.” - As people relax, the frequency of the brain waves fall to 8–13 Hz; called alpha - When people are falling asleep, their brain waves fall further to a frequency of 4–7 Hz - The person is thought to be “asleep” when over half of the 30-second epoch is characterized by theta waves = This is stage 1 sleep - Stage 2 sleep occurs when K-complexes and spindles appear - There are no longer eye movements in the EOG - The last type of non-rapid eye movement (NREM) sleep is delta sleep or N3 - During this deep stage of sleep, there are large, slow waves - The final stage of sleep is REM sleep - REM sleep is unusual because in many ways it resembles wakefulness - One notable difference is that the EMG becomes relatively silent. This is because there is muscle atonia (paralysis) of most muscle groups; one muscle group that is not paralyzed is the eye, and it is typical to see bursts of eye activity (hence the name of rapid eye movement sleep).

Answer 13

- Actigraphy is another objective method to assess sleep, but it is not considered a gold standard because it is an indirect measure—one based on movement rather than electrical brain and muscle activity - an unobtrusive technique used to assess people’s sleep outside the sleep lab - is a small, wrist-worn device (about the size of a wristwatch) that measures movement, detects movement and stores data for weeks at a time - The data is downloaded at the sleep lab; using computer software that accompanies the actigraphs, an algorithm is used to estimate sleep and wake time for each night the actigraph is worn - When you consider that PSGs cost thousands of dollars to conduct, actigraphs can be a good solution = LESS EXPENSIVE

Answer 14

- The sleep diary is the gold standard measure for insomnia - keep in mind that insomnia is a subjective disorder (i.e., you are diagnosed with insomnia on the basis of complaining about difficulties falling asleep) - When taken over the course of two weeks, people tend to make systematic errors in recording in both directions = they tend to underestimate their sleep by about twenty minutes each night - The diary is only valid if it is done prospectively (every day) and ideally, within an hour of rising The diary asks questions such as: - the time the patient entered bed - the time the patient attempted to fall asleep - the number of minutes it took to fall asleep - the number and length of awakenings during the night - the time of the final morning awakening - and the time of actually arising from bed

Answer 15

Ancient Greeks: - believed that blood filled the vessels of the brain, causing someone to fall asleep - Hypnos was the god of sleep who reportedly lived in a dark cave surrounded by poppies and other sleep-inducing plants - Somnus was the Roman god equivalent - Aristotle believed that sleep was induced after eating because the decomposing food produced vapours in the stomach - Leonardo da Vinci is reported (this is not actually confirmed) to have slept for very brief periods throughout the day and night (e.g., sleeping for fifteen minutes every two hours) = polyphasic sleep - The proponents of polyphasic sleep rely on distortions/poor understanding of scientific evidence and use the fallacious argument that people did it in the past, so we should do it now - Polyphasic sleep is unhealthy sleep, not sustainable over time, and with serious health consequences. - Many years after Aristotle, in 1584, Thomas Cogan writes about the magical sleep-inducing properties of milk, meat, and wine, and how these substances induce sleep via vapours - Modern-day sleep hygiene treatment retains some eating advice (e.g., eat cheese, milk), on the basis of high tryptophan foods, although the evidence for this is mixed hypnotoxin hypothesis: - In the twentieth century, the prevailing thought is that sleep occurs because of a build-up of neurotoxins, which are slowly eliminated over the course of the night - toxins build up over the course of a day, causing sleep; toxins are released during sleep - In 1924, Hans Berger uses the EEG to code sleep - Dr. Berger shows that the brain exhibits different patterns when asleep versus when awake and this could be achieved without disturbing the sleeping subject - This was the beginning of the gold standard tool for monitoring sleep: the electroencephalogram (EEG) Aserinsky and Kleitman (1953): - REM sleep is discovered! - Because the eyelids moved differently during certain periods of sleep, they decide to measure eye movement using an electro-oculogram (EOG) - these scientists began to wake up subjects during these periods and ask them to recall what was going on prior to being woken up - Those who were woken up during the periods when the rapid eye movements were not present were able to recall little and were groggy - those woken out of the rapid eye movement periods were able to recall dream content readily - The period associated with rapid eye movements was called rapid eye movement sleep (REMS) and became synonymous with the “dreaming” stage Vogel et al., 1975: - The antidepressant effects of REM-sleep deprivation are discovered - caught the attention of psychiatry—suddenly sleep was perhaps not just a symptom and was a mechanism through which mental disorders may be expressed or even treated Rechtschaffen et al., 1989: - Dr. Alan Rechtschaffen shows that totally depriving animals of sleep kills them - These studies provide some contrast to Kleitman’s famous sleep deprivation studies in the 1920s (described in Kleitman, 1939) wherein sleep deprivation was shown to have impairing effects in humans, but the impairment reaches a point of satiation around sixty hours and longer periods did not result in substantively greater levels of impairment - Rechtschaffen & Anthony Kales = well-known for their development of the EEG scoring criteria for sleep = R&K scoring The 1970s sees an explosion of discoveries in sleep, including: - discovery of the location of the circadian clock - development of our first objective test of sleepiness, the Multiple Sleep Latency Test (MSLT) - a test in which the person is asked to try and fall asleep every two hours for the first ten hours of wakefulness - The first sleep centre is established at Stanford University in California - The journal Sleep is established; it remains our top journal - The two-process model (Borbély, 1982) explains the roles of sleep homeostasis (Process S) and the circadian process (Process C) in sleep regulation - The Diagnostic and Statistical Manual for Mental Disorders, DSM5 (APA, 2013) renames the sleep disorder section "Sleep-Wake Disorders" to acknowledge that sleep problems are twenty-four-hour problems

Answer 16

- there are two different stages of sleep 1. REM: rapid eye movement sleep, dreaming sleep 2. NREM: non-rapid eye movement sleep, people sometimes have dreams, the body is much quieter, breathing is slower 4 stages of NREM sleep Stage 1: the lightest stage, not completely unconscious, may feel like they are slightly awake Stage 2: solidly asleep, we went most of the night in this stage Stage 3 & 4: the deepest stages, hard to arouse someone and get them to wake up, characterized by very slow activity in the cortex, broken into stage 3 or 4 based on the amount of slow-wave activity that the cortical neurons were expressing, there is a movement to combine stage 3 and 4 since the distinction isn't important between the two

Answer 17

- the depth of sleep changes as we age - slow wave/deep sleep in a young child is extremely deep = the higher brain centers are not very active, bascially controlled by the lower centers - deep sleep of an adolescent: not nearly so deep - newborns go right into dreaming when they fall asleep = REM sleep - changes at 3 months, when NREM is the first state we enter and continues for the rest of life

Answer 18

- Most of our research on this subject has been conducted in North America so the answer to this question may be most relevant for western culture - hard to define "normal" sleep - We will reserve the term “normal” to refer to “normative” sleep = parameters that describe over 68% of the population

Answer 19

“good sleep”: - sleep associated with normative sleep quality indices as well as positive functional or self-reported correlates - Begins and is sustained within ten and thirty minutes of attempting to sleep - Is preceded by sleepiness = if you do not feel sleepy before bed, you may either have insufficient drive for deep sleep or a variable bed or rise time - Is within the same “circadian” (definition to come) window each night - Is continuous through the night, e.g., not fragmented, containing no more than thirty minutes of wakefulness - Becomes lighter prior to the routine rise time—this is because the presence of melatonin has faded, sleep drive has been depleted from the homeostatic system, and alerting signals from the clock have begun - An hour or so after rising, there should be a sensation of feeling refreshed/rested - one often does not feel refreshed immediately upon rising for a myriad reasons that have no relation necessarily with whether or not sleep was optimal - Contains approximately 5% of N1, about 50% of N2, 20% of N3, and 25% of REM sleep

Answer 20

Sleep is regulated mainly by two systems: - Their interplay was most famously described by Borbély in his two-process model of sleep regulation (Borbély, 1982). 1. homeostatic system (Process S) - We have many homeostatic systems in the body - They are balancing systems that keep homeostasis - when the set-point is on the sleep side but the person remains awake, sleepy cues will be increased to make it difficult for the person to sustain wakefulness - The homeostat is always trying to balance between sleep and wakefulness - When you wake up and become active you build a drive for deep sleep; the longer you are awake and active, the greater the build-up of pressure for (deep) sleep - the less you are awake and active, the less the pressure for (deep) sleep - there is a point at which several days of deprivation looks similar to a week’s worth of deprivation - The build-up of homeostatic pressure is associated with several chemicals including a build-up of adenosine (a chemical by-product of energy expenditure in cells), and the release of the pressure upon sleeping is correlated with N3 - The next time you are having difficulty sleeping in on a weekend even though you would like to sleep in, it may be your homeostat and your circadian system sending you the message to get out of bed 2. the circadian system (Process C) - Circadian means “about a day,” and indeed our internal clock produces a cycle lasting just over twenty-four hours - The circadian system consists of many clocks in the body that receive input (muscles, stomach, and brain) - The master clock resides in the hypothalamus in the **suprachiasmatic nucleus** = receives massive innervations from the optic nerves (the eyes) and light, natural light in particular, is a very powerful cue to set the clock - although the rhythm of the clock is internally determined, it is regularly reset by cues including daylight, activity, and eating - The clock generates alerting signals that increase in magnitude as the day progresses and fade in intensity in the hours after darkness - the alerting signals begin increasing again a few hours before we naturally wake up - When our body temperature is at its lowest (i.e., the nadir or trough) we see the greatest amounts of REMS - When Process S (homeostatic system) is at a high level, it would be difficult to sleep when alerting signals were firing; however, these signals begin to fade hours earlier, with the offset of light and the release of melatonin—a sedating chemical secreted in the early evening and associated with sleep several hours later - The circadian system determines the timing of sleep stages. - If you only knew that someone’s core body temperature was at the lowest temperature in the twenty-four-hour period, which stage would they most likely be in? = REMS - If your hypothetical set-point in your homeostatic system is set at “sleep” but you are awake, which of the following is most likely to occur? = You will experience sleepy cues. - You injured your leg and have been spending a lot of time inactive and in bed. Do you think you would get: Less (deep) sleep

Answer 21

- Newborn sleep is polyphasic = there are multiple (i.e., equal distribution of sleep and wakefulness) bouts of sleep in a twenty-four-hour period, with the emergence of a more nocturnal sleep pattern somewhere between two to four months - the mean sleep duration is fourteen hours - Infants start sleeping through the night around six to nine months - babies and children continue to nap during the day - this may be because the drive for deep sleep (Process S) builds more quickly in young children, creating the need for a nap, but the drive for deep sleep is eliminated more quickly with sleep - REMS in newborns accounts for about half of their sleep, although true REMS appears around three months - REMS has been implicated in visual development and learning - NREM stages in their more adult form emerge over the course of the first year - N2 sleep spindles emerging around four-weeks-old and K complexes around six months - Sleep is deepest during infancy and early childhood, by puberty there is a significant decline in N3 - waking a small child up from N3 is difficult

Answer 22

- At one to three years old, children may take up to thirty minutes to fall asleep, but once they fall asleep, they tend to enter a deep stage relatively quickly - it is difficult to wake kids from this stage of sleep - The NREM-REM sleep sequence is closer to an hour, rather than the ninety-minute cycles that are more typical of older kids and adults - Function theories tend to focus on either a restoring brain metabolism function or one that focuses on consolidating memories and learning - there are also theories that sleep stimulates maturation in childhood - REM: stimulates brain to matrure CNS - NREM: remodelling neurons by repetitive activity in thalamocortical areas - By the time children become school-aged (three to five years) naps slowly disappear and sleep becomes monophasic (sleep occurs exclusively at night) - During the school years (six to twelve years old) the chronotype becomes evident - Chronotypes: refer to the extent to which someone is morning-like (early risers with early bedtimes) or evening-like (late bedtimes and late rise times) = an individual’s circadian propensity ex. morning-types have a shorter circadian cycle, have an advanced phase, become sleepier earlier and rise earlier as well An evening-type has a longer circadian cycle, have a delayed phase, become sleepier later and rise later as well - Chronotype has a genetic component but there are environmental factors and developmental factors as well. - Children exhibit an earlier chronotype and during puberty, there is a shift toward eveningness

Answer 23

- The sleep need of teens is a little over nine hours but there is variability in the needs of teens, and plenty of evidence that teens get much less and suffer as a result - teens tend to compensate for their sleep deprivation by napping and sleeping in on weekends; these would have a negative impact on Process C as well as Process S (Wolfson & Carskadon, 1998) - The net effect is negative because there is no regular input for the clock so that it creates jet lag symptoms and difficulties going to sleep when desired. - Napping also wipes out the accumulated drive for deep sleep so sleep can be lighter at night - One of the striking features of adolescence is the emergence of the delayed sleep phase, or a shift towards eveningness - teens tend to show a preference for going to bed later and getting up later - this can result in sleep deprivation during the week, as teens go to bed late but have to get up early to get to school - This can result in increased time in bed on the weekends to compensate - Although part of the shift is physiological and related to puberty, the social patterns of the teen’s friends, watching TV, or using the computer or gaming devices late at night could help shift teens later

Answer 24

- aging = poorer qaulity of sleep ex. increased use of medications, increased number of health conditions, stress, increased rates of sleep disordered breathing, irregular schedules post-retirement, or reduced activity post-retirement - After childhood there is often a substantial drop in N3, followed by an even bigger drop as adults reach their forties - the loss is replaced by light stages of sleep as well as wakefulness - the time spent in bed is similar even though the body is less capable of producing the same amount of total sleep time and the same amount of deep stages of sleep - In those aged thirty to sixty years old, we see that the rate of clinically significant apnea (i.e., an AHI of ten or more) is 10% of the population—15% in men and 5% in women (Young et al., 1997 - those above the age of sixty-five years old, we find that 62% have a troublesome AHI—70% of men and 56% of women (Ancoli-Israel et al., 1991) - apnea is linked to a number of other functionally impairing conditions including diabetes, stroke, heart attack, and death

Answer 25

- Falling asleep within ten to thirty minutes - Sleeping between six to nine hours - Experiencing sleepiness before bed and experiencing healthy energy after an hour or so of waking - Experiencing relatively consistent proportions of all four sleep stages throughout the night (including SWS (slow wave sleep) predominantly in the first half of the night and REMS predominantly in the second half of the night) - It is important to understand the two-process theory** = homeostatic and circadian system The homeostatic system - balances sleep and wakefulness - Upon awakening, a pressure for sleep builds across the day to ensure an adequate drive for deep sleep that night - When sleeping after an adequate build, slow-wave sleep occurs, growth hormone is secreted and there is tissue restoration The circadian system - keeps a rhythm inside of your body that is influenced by the outside world - Maintaining a regular rise and bedtime ensures the system runs healthily

Answer 26

- National transportation safety board that fatigue-related crashes are the leading cause of fatal the driver truck crashes - 1 out of 5 motor vehicle accidents are related to drivers who are too tired to drive - we spend less than a million dollars a year on education related to drowsy driving

Answer 27

- you don't notice the effects of sleep deprivation, hard to tell how impaired you are - a study showed that putting ppl into 6 hours of sleep a night for 2 weeks = at first they feel less alert, but after three or four days their perceived alertness levels off and they think they are doing fine - when they are tested = impairment in performance continues to get worse at the same rate for the entire two weeks even though ppl think they are fine

Answer 28

- The catastrophic oil spill of the Exxon Valdez, the Shuttle Challenger explosion, and the nuclear accidents at the Chornobyl facility and Three Mile Island = all linked to sleep deprivation (SD) - Sleep deprivation can be full (all night) or partial (part of the night) - SD is an epidemic problem - A decade ago a National Sleep Foundation poll in the US found that two-thirds of people reported getting less than eight hours per night of sleep - In a series of seminal studies conducted by Dr. Alan Rechtschaffen, animals were totally deprived of sleep and died within weeks - having too little or too much sleep was associated with increased mortality - disruptions to healthy sleep could be fatal - These studies provided some contrast to Kleitman’s famous sleep deprivation studies in the 1920s wherein sleep deprivation was shown to have impairing effects in humans but the impairment reaches a point of satiation around sixty hours wherein longer periods did not result in substantively greater levels of impairment - In 1966, a world record was set by Randy Gardner for the longest electrophysiologically monitored period of sleep deprivation - Randy Gardner was a student who attempted to break the previous record while being monitored with EEG and a sleep doctor, Dr. William Dement - was deprived of approximately eleven nights of sleep - he remained remarkably capable on a variety of tests - There were other deficits however, including short-term memory task deficits, mood disturbance, hallucinations, and paranoia - no other study used documentation such as the EEG to demonstrate that there were no microsleeps - Most humans are distressed by the idea of resisting sleep - The body has many ways, or unpleasant symptoms it produces, to motivate you to seek out a sleep opportunity - Sleep deprivation has been used to extract information in interrogations - your body has ways of temporarily compensating for periods in which you may be deprived of sleep

Answer 29

- Sleep deprivation refers to the avoidance of the typical sleep opportunity, but it can also refer to significantly reduced sleep or stages of sleep - When there is sleep deprivation a “sleep debt” is created and when such debt is incurred, there is increasing pressure to compensate for the loss

Answer 30

- The sleep pressure created by sleep deprivation is measured by the rebound of stages of sleep, or how quickly we enter the deprived stage of sleep and how dense the activity of that stage of sleep is during sleep - when we are deprived of sleep, we accumulate adenosine and the more it builds, the more densely we will produce deep, slow wave sleep (SWS), when we get an opportunity to sleep - If we are deprived of a particular stage of sleep, for example, REM sleep, greater amounts (longer or more dense periods) of REMS is produced - after the period of deprivation, the efficiency of sleep (i.e., the percentage of time spent asleep while in bed) increases to close to 100%, and both SWS and REMS increase dramatically - Thus the body increases the depth of sleep and also restores the density or amount of particular stages of sleep - Sleep rebound is a good index for sleep need; it is also a good index of the homeostatic system - As sleep accrues (that is, after the period of sleep deprivation) sleep decreases - This suggests that the homeostatic system is affected by the accumulation of sleep - The pressure for sleep lessens in response to the accumulation and provides feedback to balance between sleep and wakefulness - as sleep deprivation increases, sleep onset latency decreases = as sleep pressure increases, the more quickly one can fall asleep during recovery sleep - The lower the sleep pressure, the longer it takes to fall asleep - The homeostatic system is responsible for the recovery

Answer 31

- There are a number of studies to support the notion that animals die after prolonged SD ex. puppies dying after four to six days of sleep deprivation, adult dogs dying in nine to seventeen days, and after seven to thirty-one days, rabbits dying three problems occur in SD: 1. Metabolic changes in the animal that result in wasting even with ingestion of food 2. Increased vulnerabilities to infection 3. Suppressions of anabolic hormones - The result of these changes can be hypothermia and infection, although animals often tend to look healthy right up until the time they die

Answer 32

When humans are deprived of sleep they show: - increased appetite - decreased glucose utilization in subcortical areas - decreased body temperature - and an increased number of cells (phagocytes) that protect the body against infection and disease - there is no evidence that sleep deprivation leads to immediate death = It is unethical for us to do the types of studies necessary to prove this definitively - studies support that although there are many negative effects of sleep deprivation, these are reversed with recovery from sleep - once the sleep-deprived person has an opportunity to sleep, the deficits will no longer be present

Answer 33

Sleepiness: - defined as the propensity to sleep given an opportunity - the most pronounced effect of SD - objectively measured by a test called the MSLT or Multiple Sleep Latency Test - MSLT is done in the sleep lab MSLT: - The morning after sleep deprivation in the lab (normally an MSLT is done after an adequate night’s sleep), five nap opportunities are given spaced two hours apart - The quicker the person falls asleep, the sleepier the person is - Sleep onset latencies, that is, the time it takes to fall asleep should be shortest during the first sleep opportunity after the deprivation - If REM emerges at sleep onset or during the nap, this is indicative of REM deprivation/rebound - sleep deprivation is not immune from circadian effects - A study from Bonnet and colleagues (1995) showed us that as sleep deprivation increases, that is, as the number of hours without sleep increases, we see a decrease in sleep onset on the MSLT; people fall asleep faster and faster as they stay awake longer and longer - during the waking hours (Day 1 after the sleep deprivation) MSLT values do not steadily increase until that night (Night 2 of sleep deprivation) when the body’s clock is prepared for sleep - The next morning (Day 2 of sleep deprivation), when the body clock sends alerting signals, it again inhibits an increasingly faster time to fall asleep - The next night (Night 3 of sleep deprivation), MSLT values become very fast again and increasingly faster across the night

Answer 34

- In addition to changes seen on the EEG (a test that detects abnormalities in your brain waves, or in the electrical activity of your brain) in an MSLT test (The Multiple Sleep Latency Test) checks for excessive daytime sleepiness by measuring how quickly you fall asleep in a quiet environment during the day), we see cortical changes in the EEG and EOG (measures eye movement) - we see the slow eye-rolling movements indicative of the start of sleep and we see decreases in alpha wave activity and increases in theta and slow-wave activity (brain wave activity that occurs in sleep) - there is so much of this increased activity that we often encounter a problem of microsleeps, or falling asleep for very brief periods even if it does not look as though the person is sleeping

Answer 35

- During Randy Gardner’s record-setting SD feat, he was observed to have mood fluctuations and a short temper - Gardner also reportedly exhibited paranoia and some delusional beliefs reliable effects of SD: - sleepiness - fatigue - periods of confusion - mood fluctuations - delusions - and paranoia - These mood problems resolve with recovery

Answer 36

- Microsleeps (seconds of sleep potentially outside of awareness described above) interfere with task completion so it is important to have EEG monitoring during tasks, as we would not expect for people to be able to do tasks while asleep - Much of the tasks we use test attention and alertness - Sleep deprivation has a range of negative effects on cognition, most notably in prefrontal and parietal areas - SD negatively impacts tasks that involve short-term memory, executive functioning, timed tasks and tasks requiring accuracy ex. For example, a Psychomotor Vigilance Task (PVT) is commonly used to assess psychomotor performance loss because it does not rely on aptitude, or how good you are at learning tasks. the PVT requires sustained attention to detect stimuli much like the humorous sheep task from the link above - Fluctuations in the state of alertness produced by SD result in a loss of vigilance and increasing impaired performance over time - we can also use imaging studies to see corresponding changes in the areas associated with these abilities, namely the prefrontal cortex and the parietal areas

Answer 37

- The effects of acute sleep deprivation, or depriving someone totally of sleep in a laboratory setting, do not suggest that the autonomic system (more on this system in Module 5) is reliably or dramatically impaired - some studies show deficits but others do not, or the changes appear relatively minor - More chronic periods of partial SD include impaired use of glucose and insulin - Essentially people begin to look prediabetic; indeed, chronic partial sleep deprivation increases risk for diabetes - There are decreases in leptin (a chemical associated with satiety, or the sensation of being full after eating) and increases in ghrelin (a chemical associated with hunger cues) that may contribute to the risk for obesity and diabetes

Answer 38

- There is an increased fatality rate and accident severity in sleep deprivation-related vehicular accidents - Increased deficits, or “virtual” accidents on driving simulators, are seen in those deprived of three to six hours of sleep, but such deficits are underestimated by the drivers - Slow eye movements measured with the electro-oculogram are associated with lapses in attention and microsleeps = These slow, extended blinks are associated with accidents in the simulator - Thus people are unaware of the extent to which they are impaired when sleep-deprived - This may account for the driving while drowsy problem we have in society. - Workplace accidents also increase with SD and shift work

Answer 39

- Sleep deprivation is tricky research to do There are many methodological issues to overcome while carrying out this research. Here are a few of the issues: 1. Blinding: - When both the experimenter and the research participant know that SD is occurring, there is no blinding = there can be expectancy effects - An expectancy effect means that the effects may occur because of how the person expects the outcome to be ex. if you are given a pill in an insomnia study, there is likely an expectation that the pill should improve your sleep in some way, so if you are completing a rating of your sleep, you are more likely to report (consistent with your expectation) that your sleep improved ex. if you are an experimenter testing the same pill, you likely have a positive expectation that the drug will improve sleep in some way, so, if you are rating the participant’s sleep before and after the pill you will be more likely to rate improvement post-pill - Therefore, using animals (expectancy effects are not an issue with animals) and have blinded raters (those who do not know which animals were sleep-deprived) rate the animals on sleepiness 2. Harmful effects of the sleep deprivation paradigm: - The sleep deprivation paradigm for animal studies may produce some of the effects attributed to SD itself 3. Microsleeps: - If brain activity is not monitored continuously, we have no way of knowing if the person being deprived of sleep is not having brief periods of sleep - They may look as though they are awake, e.g., their eyes are open, but their brain may slip in and out of consciousness - Students are infamously sleep deprived and they are notorious for a phenomenon called microsleeps - Monitor with EEG. If we monitor the brain we can see brain waves characteristic of sleep and we can see the slow eye rolling movements characteristic of sleep onset 4. Ethical concerns: - Sleep deprivation can produce extreme distress in both humans and animals; in animals it even leads to death - it is important to demonstrate that steps have been taken to safeguard against risks and that the benefits of the research outweigh the risks

Answer 40

- To a certain degree you can manage the effects of sleep deprivation with a variety of coping aids, but given that we know that chronic SD is associated with increased mortality, the best coping strategy is getting enough sleep We can compensate for sleep loss with naps: myth or fact? - Fact. Acute or partial SD can be aided with naps (sleep outside the normal sleep window), even with nap durations as short as fifteen minutes - we are essentially napping to help manage sleepiness, rather than napping to make-up for sleep loss - Napping has a negative effect on nighttime sleep, so we nap for sleepiness, not sleep We can compensate for sleep loss with exercise or increased physical activity: myth or fact? - Fact. Increasing activity can help increase alertness after sleep deprivation - In one study, asking participants to take a five-minute walk decreased the effect of partial (50%) sleep deprivation on the MSLT - There appears to be an eventual trade-off, in that exercise after substantially greater periods of deprivation loses its effects We can compensate for sleep loss with bright lights: myth or fact? - Fact. Bright lights have some positive effect in increasing alertness during periods of deprivation - It is unclear as to the mechanism of bright light - Bright light sends a cue to the circadian system that it is time for wakefulness, not time for sleep - When in dim light, the pineal gland secretes melatonin signaling sleep several hours earlier We can compensate for sleep loss with cold air: myth or fact? - This is more of a myth ex. You may have heard that when you are driving and you are sleepy, you should blast the air conditioner - Increasing colder temperatures may improve how someone views their level of alertness on a task such as a driving simulator after sleep deprivation but there is no real evidence to suggest that temperature reliably improves performance We can compensate for sleep loss with posture (e.g., staying upright): myth or fact? - Fact - Whether someone is sitting, standing, or lying down has some influence over alertness - those sitting up take longer to fall asleep than those lying down - sitting up instead of lying down activates the sympathetic branch of the autonomic system so this may explain the effect We can compensate for sleep loss with stimulant drugs, such as caffeine, modafinil, and amphetamine: myth or fact? - Fact - Stimulant drugs can help with alertness during periods of sleep deprivation but the withdrawal several hours later will increase fatigue and intensify the effects of sleep loss - Caffeine also interferes with deep sleep that night, so the net effect of caffeine is negative - Like naps, stimulants are mainly to increase alertness and mitigate sleepiness; they are not an effective replacement for sleep - Although nicotine is a stimulant, it reliably interferes with sleep, and does little to increase alertness and performance during SD

Answer 41

- Hibernation is a period of inactivity with mixed evidence for sleep occurring - Hibernation most often occurs in the winter when food sources are scarce - While in hibernation, body temperature, respiration, heart rate, and metabolic rates drop - Hibernators most often draw on their fat stores during this time to survive - Animals enter hibernation through NREM sleep - It is not accurate to conclude that hibernation is a type of sleep, although there is some evidence of some NREM and REM cycling occurring during hibernation - The fact that sleep rebound occurs after hibernation suggests that sleep deprivation may occur during hibernation - During this sleep we see a loss of SWS (slow wave sleep); this is a phenomena we see during recovery from extended time awake - There is also some evidence that some animals appear to wake up from hibernation in order to sleep - hibernation does not appear to be a mere sleep state and there is evidence that SD can occur in hibernation

Answer 42

- The brain waves and normal cycling of sleep stages are not preserved during anesthesia, and in some cases we see evidence of SD (i.e., rebound) after anesthesia - Likewise, prolonged sedation, as in induced comas, looks different from sleep and can be associated with rebound upon waking up - This issue is made complicated by what type of anesthesia, how long the administration, and the time of day at which it is administered - That said, there is little evidence that sleep truly can be replaced artificially with these methods

Answer 43

- Jackson died from complications of using Propofol as a sleep aid - Propofol is not a sleep aid; it is a form of anesthesia - there is little evidence that anesthesia is like sleep, although this varies widely depending on what type of anesthesia is used - Jackson was being administered this medication during a time in which sleep is not optimal (e.g., Jackson died around noon) because alerting signals would be emitting from the body clock - In the trial, the doctor administering the drug reported he gave Jackson nightly infusions - there is some evidence that the withdrawal effects the next day could delay rebound recovery of sleep - The half-life of this drug (the time at which half of the drug is out of the system) is between two and twenty-four hours - It appears that the medical team had little knowledge about sleep - Propofol depresses respiration and this is potentiated (i.e., worsened) in the presence of also taking benzodiazepine medications = Jackson also had benzodiazepines in his system

Answer 44

- sleep deprivation can cause many problems in humans and in animals—it can be fatal - Sleep debt occurs when we have an insufficient amount of sleep - There are methodological problems with how subjects are deprived of sleep in sleep deprivation research, which makes it difficult to know if the results are merely due to the stress incurred from the methods - There are a variety of ways to compensate for sleep loss (e.g., naps, bright lights, standing or sitting up, or taking stimulants) but none help sleep; the best cure is simply to go to sleep that night

Answer 45

- several parts of the brain regulate sleep 1. the circadian pacemaker - internal clock that consists of about 50,000 of the smallest cells in the human brain = very compact - similar to the heart's pacemaker that controls the cycling of the heart to occur about once every second - the circadian pacemaker controls many different bodily functions to occur about once every 24 hours 2. the homeostatic system - helps to regulate the timing of sleep and awake - system of increasing drive for sleep the longer we are awake = appetite for sleep goes up and up the longer we are awake - when we sleep, the appetite/drive for sleep declines - this system works together with the internal clock (the circadian pacemaker) to maintain a stable level of alertness during the daytime - as the drive for sleep is increasing, the internal clock in the brain sends out a stronger drive for waking = helps us maintain a level of alertness throughout the day?

Answer 46

- The Drosophila is a very important fly - The Drosophila has taught us quite a lot about sleep These flies are attractive to genetic researchers because they are: - easy to keep in the lab, - breed very quickly (gestation is about a week and a half) - and it is relatively easy to manipulate their genetic structure - In sleep, they are particularly useful because their sleep is under circadian and homeostatic control just like humans - Flies have taught us that gene alternations (even in one gene) can affect the homeostatic system as well as sleep length, and researchers have identified differing genes for homeostatic versus circadian factors

Answer 47

- The clock is a fascinating and important part of our sleep regulatory system - the cells in our body exhibit a rhythm; that is, they are like tiny clocks - Although there is a central oscillator that coordinates our rhythms, our cells can generate the rhythm independently because of circadian genes - There are four genes (CLOCK, BMAL1, PER, and CRY) that are the fundamental genes of the clock *** - Within each oscillation cell, the process of protein synthesis is responsible for the keeping of the twenty-four-hour rhythm - there is not one gene responsible for the clock but the workings of several positive and negative genes that form a feedback loop and work together for the expression of the clock - These clock genes are not just sleep genes, as the clock is responsible for multiple functions, not just sleep, and the genes are also implicated in other behaviours ex. CLOCK is implicated in emotional behaviour - Circadian preferences, that is, the extent to which someone is most alert during the morning or evening hours (e.g., an early bird or a night owl) has a genetic basis as well - Twin studies have shown us that genetics account for about 50% of these preferences - It is unclear if genes, or more precisely a gene (i.e., PROK2) is responsible for habitual sleep length (e.g., the extent to which one is a long or short sleeper) - Some studies suggest the heritability is between 17 and 40% - There are some clear genetic disorders such as fatal familial insomnia as well as sleep disorders with some genetic contribution ex. there appears to be some genetic contribution to restless legs syndrome, (isolated) sleep paralysis, and sleep disordered breathing - Concordance studies = studies in which we measure the rates of agreement on particular traits in twin pairs Monozygotic (MZ) twins: - siblings who share the same DNA Dyzygotic (DZ) twins: - those who share 50% of their DNA - First degree relatives of those with narcolepsy are twenty to forty times more likely to have the disease - However, the rate of concordance in narcolepsy is only about 30% for MZ twins which suggests that there must be other factors at play in narcolepsy as well - most famous genetic studies in sleep was conducted with a group of Doberman pinschers - These Dobermans were bred to select for a hypocretin receptor abnormality - Missing this gene, these Dobermans suffered from cataplexy = loss of muscle tone under emotional circumstances such as excitement or startle - Dobermans were bred based on the cataplexy (hypocretin/orexin 2 receptor) gene and when they become excited about a treat or wrestling with one another, they lose muscle tone and collapse

Answer 48

- I hate to disappoint, but it is statistically unlikely - You are most likely to die at 11 a.m.; a time at which most people are not asleep - This amusing but somewhat morbid fact is from genetic studies that examined the mean time of death and linked it to a circadian gene - It is particularly unlikely to die of a cardiac event during the night as there is a nadir of cardiac events; about 10 to 20% of major cardiac events such as heart attack or angina happen overnight - However, there is a peak of cardiac events that occur between 6 and 11 a.m - Also, it turns out that if you have a particular circadian clock gene variant, you are more likely to die around the dinner hour (e.g., 6 p.m.) than in the morning

Answer 49

- Chemicals are the messenger system in the brain - Chemical messengers are sent and received at different areas of the brain and this is how the states of sleep and wakefulness are produced - there are environmental and behavioural inputs into these processes as well, but we will discuss these in the next section Ascending Reticular Activating System (ARAS) - a system that is comprised of many different connections in the brain central to wakefulness, and therefore essential to sleep - When the ARAS is activated, your brain is alert ** Wakefulness chemicals include excitatory chemicals such as - glutamate, - acetylcholine (Ach), - norepinephrine (NE) - orexin, - serotonin, - and dopamine - ARAS originates in the brain stem of the brain and projects up all the way to the cortex - The brain stem is a key area for sleep and alertness but damage further up the system, even in the cortex can have a negative impact on sleep - Damage to the brain stem can be catastrophic for sleep - There needs to be an inhibition of the brain stem, and more generally of ARAS, in order for sleep to occur - The excitatory chemicals mentioned above must decrease (inhibited by chemicals such as GABA) - there must be ample adenosine accumulation and secretion of the hormone melatonin from the pineal gland several hours before sleep Ventrolateral preoptic nucleus (VLPO) - a hotspot for sleep production = textbook refers to it as a sleep switch - is at the back of your hypothalamus - When the sleep switch is on, the VLPO is on and arousal areas switch off - When switched on, it sends “inhibitory messages” that can inhibit chemicals like orexin - Lesions to this area are very damaging to sleep - Also important in this process are changes in the thalamocortical areas - When measured activity in the cells of the VLPO are quiet, ARAS is active, orexin is released, and there is a state of wakefulness - REMS is more complex; that is, separate components of REM sleep are generated in different areas and with different chemicals - EMS occurs when ACh cell activity increases and both 5hT activity in dorsal raphe and NA activity in the locus coerulus decrease Sensory blockade - With the onset of sleep, less sensory information is transmitted via the thalamus up to the cortex—this means that we are less aware of sensory information in our environment - but it is inaccurate to say that sensory information such as sound or tactile information are entirely blocked—just greatly diminished - People can typically continue to respond to important information such as very loud noise, being shaken, or the sound of their name - When we see spindles or K-complexes in the EEG, these are orienting responses to sensory information in the thalamus that is blocked from being sent up to the cortex Suprachiasmatic nucleus (SCN) - It is the central pacemaker of the circadian timing system and regulates most circadian rhythms in the body - a bilateral structure located in the anterior part of the hypothalamus - If there is damage to this system, there is a loss in the timing of sleep, such that sleep can occur off and on throughout the twenty-four-hour period

Answer 50

- for sleep to occur, several events must occur - In addition to excitatory chemical inhibition, there must be ample adenosine accumulation and secretion of the hormone melatonin several hours before sleep - The latter two of these steps occur due largely to behavioural and environmental factors - the basics of the physiological mechanisms underlying sleep and wakefulness = the circadian and homeostatic systems - these regulatory systems exert influence over behaviour, but behaviour and the environment influence these processes as well Homeostatic system - sleep deprivation increases homeostatic pressure to sleep and also increases the density and proportion of slow wave sleep - the body has a set-point for how much sleep it requires and when there is too little or too much time spent in bed, the homeostatic system will attempt to “correct” the behavioural input - Consider a situation in which someone has lingered in bed in the morning attempting to sleep. - During this time, homeostatic pressure does not build as there is little energy expenditure and thus little buildup of adenosine. - That night, all things being equal, there would be less slow wave activity in the EEG = sleep is less deep and you can be more prone to wake-ups = can cause chronic insomnia - The homeostatic pressure is too low to produce adequate deep sleep and often, the person is unable to sustain continuous sleep - Sleeping in, getting into bed early or napping limits drive accumulation and prevents an adequate amount of drive to build - Sleep drive is diminished when compared to normal sleep drive - If someone spent the day under very low conditions of activity, such as lying on the couch, the sleep drive would be highly diminished relative to normal sleep drive Circadian system - The clock is longer than the twenty-four-hour period thus there is some drift that needs to be managed by setting the clock with environmental input every day - This is done most often with (natural) light - The eyes are the primary point of input and this photic information is transported via a chemical messenger to the suprachiasmatic nucleus (SCN) - Entrainment can also occur via endogenous input such as melatonin release (this occurs in response to light offset however) and core body temperature (although melatonin can also affect core body temperature) - Both melatonin and core body temperature rhythms are regulated by the suprachaismatic nucleus - Core body temperature is also a homeostatic system that balances heat loss and heat generation - One can visualize someone’s circadian cycle by plotting core body temperature across the twenty-four-hour period - there is a periodicity to body temperature such that body temperature begins to fall several hours before sleep and falls to its lowest point around 4 a.m., forming a nadir or trough, until body temperature rises again prior to waking up - Body temperatures continue to rise throughout the day and into the evening - Assuming that homeostatic pressure is optimal, the best bedtime tends to be the time at which there is the steepest rate of decline of core body temperature - Although cells keep time, there is not a perfect correspondence with the environment which is exactly twenty-four hours, so entrainment to the environment happens on a daily basis - One of the key ways this occurs is through the eye - At the back of the eye are the optic nerves which innervate the suprachiasmatic nuclei in the hypothalamus - This photic information can be transmitted even in those who are blind, although there are some exceptions - Individuals who are totally blind exhibit a “free-running” circadian rhythm—in other words they sleep at all different times in the twenty-four-hour period and there is little correspondence with conventional diurnal behavioural schedules - However, in some people who are blind, you can set their schedule including when they eat, get in and out of bed, etc., and it can entrain the circadian pacemaker

Answer 51

- Cells exhibit a rhythm because of circadian genes: CLOCK, BMAL1, PER, and CRY - Sleep occurs because of deactivation of ARAS - The timing of sleep is generated by signals from the suprachiasmatic nucleus but sleep initiation is linked to homeostatic pressure - Homeostatic pressure is the result of the accumulation of cell metabolites (e.g., the byproducts of cellular activity). Putative metabolites include adenosine and cytokines - The production of NREM is from the hypothalamus (in the preoptic area) by GABA-ergic cells - REM occurs when ACh cell activity increases and both 5hT activity in dorsal raphe and NA activity in the locus coerulus decrease

Answer 52

- the longer we are awake, the greater the intensity and/or duration of our subsequent sleep - It is thought that sleep drive is maintained between an upper threshold for initiating sleep and a lower threshold for terminating sleep - Above the upper threshold sleep is more compelling, and below the lower threshold sleep is more difficult to achieve - The intensity of slow-wave activity (SWA) in the brain during N3 is an indicator of the level of sleep drive - The intensity of SWA is proportional to the amount of prior wakefulness but also depends upon the type and intensity of the waking experience

Answer 53

- the longer we are awake, the greater our need to sleep - the amount of continuous time we are awake approaches 16 h, we are much more likely to become aware of the pressure to sleep - This occurs sooner if we are already sleep deprived - If our time awake goes well beyond 16 h, we feel the urge to sleep getting stronger and stronger - There is some evidence that the level of sleep drive plateaus after about 30–50 h without sleep, when we seem to be as sleepy as we can be There are three aspects of sleepiness: 1. Introspective - the self-assessment of your internal state - measured by asking people how sleepy they think they feel in certain kinds of situations or how sleepy they feel at the moment - This is most often and best done using standardized scales rather than casually asking people how they feel - However, these scales may not always be accurate because a person may not be aware of their true sleepiness or not wish to divulge it 2. Physiological - your body’s biological need to sleep - It can be viewed as similar to other drives such as hunger and thirst 3. Manifest - the behavioral component as shown in performance deficits, errors, inattention, and even being overcome by sleep - There are methods of measuring each of these kinds of sleepiness - they do not always correlate well with each other because factors like individual differences, motivation to remain awake, and being in a stimulating and distracting environment may affect each of them differently

Answer 54

Epworth Sleepiness Scale: - the most widely used the standardized subjective scales to assess introspective sleepiness - It asks questions about falling asleep in situations that typically promote sleep - It has been validated on populations of people complaining of a sleep problem Stanford Sleepiness Scale (SSS): - instructs a person to select one of seven items to describe the current state of alertness - While it has been shown that sleep deprivation does increase SSS scores, there are no norms available with which to compare responses Analog Scales: - developed on which a person indicates how they feel by placing a mark on a line of set width, usually 10 cm, between very alert at one end and very sleepy at the other

Answer 55

Multiple Sleep Latency Test: - The most commonly used assessment of physiological sleepiness is the multiple sleep latency test (MSLT) - For this test, a person is given a 20-min opportunity to fall asleep in a quiet, comfortable sleep lab room every 2 h during the day - They are instructed to try to fall asleep - An average of more than 10 min to get to sleep is considered acceptable sleepiness, while less than 5 min is considered pathological indicating a significant sleep problem - very good validity and reliability - some sleep specialists propose that measuring the theta wave activity in the brain when awake is a more direct way to assess physiological sleepiness - It is known that an increase in theta activity is associated with sleepiness - there is also a circadian component to levels of theta activity, and meditative states can increase theta waves showing that the MSLT is less than a pure indicator of the level of sleepiness

Answer 56

Maintenance of Wakefulness Test: - A variation of the MSLT - thought to measure manifest sleepiness - It is similar to MSLT except people are instructed to remain awake while being still in a semi-reclined position in a dimly lit, quiet room - it measures the ability to remain awake Psychomotor Vigilance Task: - Another way of measuring manifest sleepiness includes various performance measures - usually repetitive tasks such as number substitution or pressing one of several buttons in response to the nature of a light or sound pattern - scored for speed and accuracy = vigilance tests - A commonly used example is the psychomotor vigilance task (PVT) = measures button press response time to a visual display on a microcomputer - The display is presented randomly every 2–10 (or 5–12) s - These three ways of measuring sleepiness do not correlate well with one another because they may be measuring different aspects of sleepiness and be affected by other than the need for sleep, such as where the measurement is taken, differing test durations, and what the person taking the measurement expects it to show - Horne cautions that these tests, especially those done in the laboratory, may show small differences in sleepiness that are of no consequence in the more stimulating real-world environment

Answer 57

- Since the turn of the century, over 1,000 studies of sleep deprivation have been published The list of the effects of continuous sleep deprivation that have been reported is long and includes: - negative changes in emotions, - behaviors, - and mental processes as well as biological effects - the effects of sleep deprivation on mood appear to be greater than the effects on motor or cognitive performance - sleep deprivation increases manifest and physiological sleepiness but not always introspective sleepiness = people may not be aware of the severity of their sleep deprivation - Some of the effects of sleep deprivation are modulated by circadian arousal influences - only mildly diminished alertness may be experienced during the day, but considerably decreased alertness, slowed reactions, and errors are experienced during the night - while the number and intensity of effects generally increase as the degree of sleep deprivation increases, the manifest sleepiness can be strongly influenced by the situation - the psychomotor behaviors most affected are long, monotonous, externally paced, newly learned tasks requiring use of memory but without providing any performance feedback ex. driving

Answer 58

``` COGNITIVE PROCESSES: Difficulty concentrating Invasive daydreaming while engaged in cognitive work errors of omission[errors of commission Disorientation Perceptual distortions and hallucinations Greater indecisiveness Slowing of mental processes such as reaction time Decrease in short-term memory Decrease in creativity and mental flexibility Decline in logical reasoning ability for complex problems Decreased attention Decreased information processing Interference with executive functionsa Decrease in integrative ability Lapses of consciousness Confusion Negative impact on mood Difficulty multitasking ``` ``` BEHAVIORS: Less spontaneous Over responsiveness Microsleeps Decrease in vigilance Decreased sense of humor Less able to deal effectively with unfamiliar situations Involuntary sleep attacks Less desire to socialize Decreased psychomotor performance Clumsiness Slurring of speech Harder to ‘‘find the right word’’ Increased motor vehicle accidents ``` ``` PHYSIOLOGICAL: Heart palpitations Fall in body temperature (about 0.8 F) Slow eyelid closures Droopy eyelids Itchy eye Tremor Weight gain Greater gag and deep tendon reflexes Increased SNS activity Hormonal changes Increased caloric intake Weight gain Decreased resistance to infection Increased ghrelin Decreased leptin Increased insulin resistance (decreased glucose tolerance) Increased hunger ``` ``` SUBJECTIVE: Lethargy Sense of partial loss of control Disorientation Irritability and negative moods Even paranoia in some individuals ```

Answer 59

- may cause brief absences of attention called lapses - These phenomena are equivalent to your flashlight suddenly going dark but only for several seconds - The frequency and duration of microsleeps increase with the degree of sleep deprivation - after about 40 continuous hours without sleep, they are unavoidable without sustained mental effort and strong external stimulation - Most sleepdeprived people also experience mild body complaints, anxiety, depression, and paranoia - Serious delusions, paranoid thoughts, and depersonalization may occur after four continuous nychthemerons without sleep, especially in persons of weak psychological stability - not everything appears to be affected by less severe sleep deprivation - Objective measurements show that sheer physical exertion and exercise not requiring much mental effort, such as weight lifting, running, or swimming, do not seem to be diminished by mild sleep deprivation - However, sleep-deprived people feel that they are doing worse or are exercising harder than they would if they had had adequate sleep - the exercise takes more effort as reflected in increased heart and respiration rates - sports that require more attention, thinking, and rapid changes in coordination, such as basketball, tennis, or soccer, are more likely to be negatively affected by sleep deprivation - Tasks involving logic are slowed but otherwise not affected - Many people believe sleep deprivation does not affect their performance - until the late 1950s, scientists were not able to demonstrate any performance deficits resulting from sleep deprivation - This was because the scientists were not looking at the right kinds of tasks - Only when they used tasks whose timing was not determined by the subject that went on for longer than 10 min and was rather boring and repetitive, did the effects of sleep deprivation become noticeable - sleep-deprived individuals gradually became slower and slower in their response times and even occasionally failed to respond

Answer 60

- masked by activity, bright light, noise, posture, stress, motivation, and some drugs - Masking occurs when extraneous influences override sleep propensity ex. in a 1985 experiment (Horne and Pettit 1985), volunteers doing a vigilance task involving monetary rewards for correct responses but fines for false alarms performed better than volunteers without such motivation for the first 36 h of sleep deprivation - during the next 24 h, the performance decreased in the incentive group but was still above that of the no incentive group - As sleep deprivation continued beyond this point, no difference occurred between the incentive and no incentive groups - In another study (Haslam 1983), soldiers without sleep for three days showed a performance drop of 55 % compared to their performance before the deprivation - But when they were simply told that the deprivation would end in a few hours, their performance jumped back to 85 % - not all performance is detrimentally affected by sleep deprivation - some kinds of performance are more affected than others - when the deficits are present, they may be quantitative, such as a general slowing down, or qualitative, such as committing errors - sleep-deprived subjects can compensate for short periods of time even on tasks that are affected if they apply extra effort, especially when motivated by being given an incentive or immediate feedback - the ability of people to 46 3 The Need to Sleep compensate by applying extra effort diminishes with greater sleep deprivation - external stimulation such as loud noise has been shown to impair the performance of non-sleep-deprived subjects but can result in small improvements in the performance of sleep-deprived subjects - The noise is distracting to the nondeprived subjects but arousing to the deprived ones - sleep-deprived people are both more easily distracted and more easily irritated by irrelevant stimuli - there are individual differences in both alertness and performance following sleep loss - extroverts and people who are sensitive to caffeine tend to be more sensitive to sleep loss - while people often believe they adjust to sleep loss, the truth is their performance becomes steadily worse - Older adults are less affected by sleep deprivation than younger adults - some people are greatly impaired by even moderate sleep loss; others are only impaired when sleep loss becomes severe The reason why there are so many mental and behavioral effects of sleep deprivation can be traced to changes in physiology: - decrements in brain functioning, - changes in the functioning of the autonomic nervous system, - biochemical changes, - increased sensitivity to pain, - and even how some genes are expressed - It is widely shown that recovery from sleep loss, even for as long as 10 nychthemerons, is quick—occurring within one to three nights of sleep - The reason is that recovery sleep is deeper, that is containing more SWA - during sleep deprivation, SWA intrudes into waking hours, which may replace the amount needed during recovery sleep - N3 sleep recovers first, typically on the first recovery night, and then REMS on the subsequent night or two

Answer 61

- More common than missing an entire night of sleep is getting some sleep but not enough, night after night - Most sleep experts maintain that sleep deprivation is a chronic and serious problem in the U.S. resulting in what has been called sleep debt - almost two-thirds of respondents aged 13–64 years said they do not get enough sleep on week nights to meet their needs - For the adults, rather than the seven and a half hours that enables them to feel their best, they get a bit less than seven on the average weeknight - The situation is even worse for the teenagers; they report averaging one and three quarters less sleep per night than the recommended nine hours and 15 min - some experts believe that people average less sleep than they did at the turn of the twentieth century - not sleeping enough results in chronic symptoms of sleep deprivation with potentially serious consequences - The effects of multiple nights of partial sleep deprivation accumulate - the effects are increasingly noticeable for most people when the amount of sleep per nychthemeron drops below 6 h night after night - Yet as time goes on, chronically sleep-deprived people become less aware of just how sleepy they are - As the sleep debt accumulates, alertness diminishes, resulting in increased risk of errors at work, injuries, motor vehicle accidents, conflicts with others, and health problems

Answer 62

- the effects of partial sleep deprivation are similar to those of total sleep deprivation - Sleep onset generally becomes quicker, and sleep is more efficient, which is beneficial - The most noticeable effect is a decline in mood, but there is also a noticeable decline in mental skills similar to those found with total sleep deprivation - partial sleep deprivation is somewhat akin to selective REMS deprivation, because it is the end of the night that is typically cut off - if you go to bed very late on a couple of short nights, then you might have a lot of REM sleep due to its rising circadian phase late in the morning - With successive nights of partial sleep, REM pressure (the number of times REMS is begun during a period of sleep) accumulates = tendency for more REMS to occur early in the night - the total amount of REMS is still diminished - N3 sleep is not totally spared either for there are elevations in SWA indicative of a greater pressure to achieve N3

Answer 63

- Sleep debt also has cognitive and physiological consequences - For most people, habitually sleeping less than seven hours per nychthemeron results in cognitive deficits that become increasingly worse over time - The greater the nightly deficit, the more rapid the rate of the cognitive decline - The deficits can accumulate to the point that they are equivalent to total sleep deprivation of 1–2 nychthemerons - For a long time, research showed that mild sleep deprivation has a small but measurable negative effect on the immune system Going without sleep for over a week also results in effects such as: - mild vibration of the eyeballs from side to side, - hand trembling, - some slurring of speech, - drooping eyelids, - greater gagging, - and increased sensitivity to pain, all of which quickly reverse with sleep

Answer 64

Today, it is agreed that REMS deprivation may result in any one of a number of temporary symptoms, including: - changes in emotions, - increased liveliness, - greater appetite, - more interest in sex, - and memory impairment - REMS deprivation can temporarily lessen the degree of depression in some depressed individuals, which is consistent with the fact that many antidepressant drugs reduce REMS

Answer 65

- if you awaken the subjects every time they initiate N3, the amounts of other sleep, especially REMS, are also greatly disrupted since NREMS normally is the doorway to REMS - Instead of awakening a sleeping person, a tone is sounded just loud enough to drive them out of N3 but not loud enough to awaken them - With this procedure, considerable REMS is still obtained, as are N1 and N2 - Overall, it is more difficult to eliminate N3 than to eliminate REMS = about 6 times as many sleep interruptions

Answer 66

- Only sleep can reverse the effects of lost sleep - Caffeine, exercise, stimulation, and the like can ameliorate the effects a bit for a period of time but not reverse the loss - makeup sleep does not have to equal hour for hour the time lost, since recovery sleep is of greater intensity and efficiency - Recovery sleep is more intense sleep in the sense that it is harder to awaken the sleeper - N3 intensity is shown by the percent and amplitude of the delta waves - Total recovery sleep time is somewhat longer if a person can sleep as long as desired - Recovery from sleep deprivation is relatively quick and complete - It typically takes 1 to possibly 3 nights—shorter if the recovery nights are extended - as the proportion of sleep loss goes up, the proportion of it that has to be recovered goes down - The early recovery sleep preferentially emphasizes N3, so much so that REMS may be less than normal while N3 recovers - Rate of recovery of N3 has been described as ‘‘a saturating exponential curve’’ = there is proportionally more recovery in the first few hours of N3 than the last few hours - It is only later in the night or even during the next night or two that REMS recovers - Its recovery seems to depend on increasing the amount of time in this stage more than increasing its intensity

Answer 67

- Extended sleep can contribute to recovery from sleep deprivation, but sometimes people extend their sleep even when not deprived - the extra sleep itself has a low efficiency and contains little, if any, N3 unless sleep is extended beyond 12 h, at which point, some N3 begins to reoccur - Instead of extra sleep making people super-alert and able to function at above normal levels, the opposite appears to be true - Too much sleep on one night has been described as making people under responsive, lethargic, and ‘‘thick headed.’’ - extended sleep results in emotional letdown and irritability plus deficits of performance - These effects may be an exaggeration of what is called sleep inertia = the transitional state between sleep and wake, marked by impaired performance, reduced vigilance, and a desire to return to sleep

Answer 68

- We humans tend to be most sleepy at night and, more often than not, sleep then. This pattern is an important example of the circadian rhythms of the body, near 24-h cycles of behavior and physiology Circadian rhythms influence sleep as well as our: - sensory processing, - short-term memory, - cognitive performance, - alertness, - and many other behaviors - our body temperature, which is important for sleep, hormones, urine production, and other biological processes also follow a circadian schedule - Our internal biological clock(s) enable us to be in synchrony with the 24-h external world - our circadian rhythms enable us to have an internal biological (subjective) day and night that usually enables us to mirror and prepare for the forthcoming change between external (objective) day and night

Answer 69

Entrained: - In the entrained 24-hour protocol, subjects live in a laboratory for a period of time - They are aware of the time of day but are on a rigid schedule of bedtime, wakeup time, meal time, and timed activities - Biological and/or behavioral measurements may be regularly taken to assess their 24-h rhythms under ‘‘normal’’ conditions - special sleep labs with no windows, clocks, radios, phones, or any other direct links with the outside world that could give an indication - one of three types of experiments can be undertaken: free-run, forced desynchrony, or constant routine Free-run: - Free-run experiments were the earliest conducted - The subjects are free to sleep whenever they feel like it - They have control over the lighting, when they eat meals, and engage in leisure activities - Their sleep and wake patterns are recorded - These studies typically go on for weeks, and without any time clues, the subjects rely on their own internal circadian clocks - Free-running subjects eventually have an average circadian period of slightly longer than 24 h Forced Desynchrony: - requires subjects to be on a sleep/wake cycle that is outside the bounds of what most people are capable of achieving - For one-third of every cycle, they are required to be in bed in the dark followed by 2/3 of the cycle out of bed in light - Typical cycles that are used are short, such as 20 or 90 min, or long, such as 28 h - on the 20-min cycle, the subject has to be in bed trying to sleep for 7 min - Then, they must get out of bed and be awake for 13 min before returning to bed - This might go on for anywhere from 24 to 48 h for the shorter cycles to days or weeks for the longer cycles - The amount of sleep obtained during each in-bed portion is measured - A forced desynchrony protocol causes the sleep/wake cycle to become desynchronized, that is, separated from the circadian temperature cycle, meaning that subjects will be sleeping and awake at different phases of their temperature cycle over the duration of the experiment Constant Routine: - the subject remains in a quiet environment in a semi-recumbent position, but continuously awake with the illumination low and constant - Small meals are eaten every hour - Constant routine studies are typically done for more than 24 h but less than 48 - During this protocol, changes in physiological indicators, such as melatonin and body temperature, and performance on psychometric tests, can be measured hourly to assess their circadian rhythms

Answer 70

- The sleep/wake cycle is dependent on the circadian clock, not vice versa - Left to its own devices, our internal sleep/wake cycle for 75–80 % of people would be close to but greater than 24 h Entrainment: - Most of us live successfully in a 24-h world because our internal rhythms are regularly reset, entrained, primarily by stimuli from outside the body acting as zeitgebers, German for ‘‘time giver’’ - Entrainment is like if you, the zeitgeber, were to daily reset your watch that runs a bit slow - The major zeitgeber for our sleep and wake cycle is the nychthemeral alternation of light and dark that occurs on the planet we inhabit - Things like exercise, social stimulation, mealtimes, room temperature, and knowledge of what time it is also help but are largely thought to play a minor role compared to that of light - The right amount of properly timed light can either phase advance (move to an earlier setting) or phase delay (move to a later setting) our circadian rhythm for sleep to any new setting in usually two to three nychthemerons - The brighter the light, the greater the entrainment effect - even room light, that is, generally about 20 times dimmer than outside light on a somewhat cloudy day, can also have some entrainment influence - Our circadian rhythm for sleep can be easily entrained to shorter, up to 22 h, or longer, up to 26 h periods—even longer or shorter if approached gradually

Answer 71

- shows the times when we are sensitive to a zeitgeber that is able to entrain the circadian clock as well as the direction and intensity of the change - It is called phase response because how our clock responds to light depends on what part, or phase, of the 24-h cycle it is in - Exposure to light for a few hours before and after our regular time of falling asleep will delay the clock, but exposure a few hours before and after our regular arising time will advance the clock - PRCs are related to our body time, not the real time, but since most people sleep when it is dark out, it has become common to describe the phases of the PRC in terms of subjective night, subjective dawn, subjective day, and subjective dusk CONT PG 60

WEEK 1 - 4 Flashcards

(99 cards)