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Chapter 6

Chapter 6 Reading Notes.pdf

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Camie Condon

READING NOTES Chapter 6: Wakefulness,Alertness, Sleep, and Dreams • Although steates of wakefulness and sleep are not so distinct, we cross an important line when we pass from one to the other: We lose consciousness – awareness of the external environment • Aloss of consciousness is fairly abrupt, although at times we seem to enter a detached intermediate state that might reflect what Vogel calls sleep-onset mentation Origins of Sleep: Evolutionary Considerations • Even though sleep has been linked to several psychological and psychological functions, we don't know why sleep evolved • If one of our main drives is to procreate, the fact that we sleep goes against the logic of natural selection • We conserve energy when we sleep and sleep prepares the brain for the next day by replenishing glycogen supplies in the brain • The two main themes that are associated with our ancestors were obtaining food and avoiding predators Wakefulness, Sleep, and EEGActivity Correlates of Sleep and Wakefulness • The best index of wakefulness, drowsiness, and sleep in humans is cortical activity • Atypical night of sleep consists of a gradual progress from state 0 (wakefulness) through stages 1, 2, 3, 4 and then backward through states 3, 2, and 2 into what is called stage 1-REM (rapid eye movement) • This cycle takes about 90 – 120 minutes and repeats itself • Aserinsky and Kletiman found that REM occurred in conjunction with low-voltage mixed-brain-wave frequencies and when people weer awakened, they regularly reported vivid dreams • REM occurs in conjunction with stage 1 sleep ◦ REM bursts occur about 90 minutes after we go to sleep and recur every 90 minutes on average ◦ It tends to lengthen as the night progresses Hobson's Model of Sleep and Dreams • Why we go back and forth between REM and NREM and why our mental processes in the REM state are so different from those in waking and the NREM state: ◦ Two main chemical systems of the brain: ▪ TheAminergic System • Comprises of the monoamine transmitters, norepinephrine, and serotonin • When we fall asleep, our our brain enters the NREM state ◦ Astate characterized by inactivity of the cerebral cortex and reduced activity of the aminergic system • The amines help us to decide how to make decisions when we are awake ◦ Amines allow us to determine what is real or not by assessing information by our past experiences • When secreted at a high level, inhibit cholinergic system ▪ The Cholinergic System • When we fall asleep, the aminergeic system plunges and the cholinergic system begins to activate the visual and motor cortex ◦ Eventually creating the dream state, REM ◦ The visual cortex is active and the individual experiences “hallucinations” ◦ The stream of images violates rules of time and place • During sleep, the prefrontal cortex is inhibited, especially during REM sleep ◦ This is consistent with the idea that our prefrontal cortex is the executive area of the brain Origins of REM and NREM • REM and NREM emerged: ◦ As an adaptation out of the need to process immediate sensory information (during the waking state) ◦ The need to create as well as maintain new memories of ongoing experiences (during the sleeping state) ▪ The essence of the argument is that when warm-blooded animals emerged, they had a limited capacity to deal with both of these demands simultaneously Why We Fall Asleep and Why We Wake Up • Hobson views the ebb and flow of NREM and REM as being due to the cyclical natures of different brain systems operating in a complementary and interdependent fashion • Three sets of factors determine when we fall asleep and when we wake up: ◦ Circadian Rhythm ▪ Circadian comes from Latin, circa diem meaning “about a day” ▪ The tendency to follow a 24-hour cycle appears largely to be the synchronizing effects of events in our environment The Monday-morning blues might be a direct result of letting ourselves shift to our natural 25-hour biological rhythm ▪ What produces this rhythm? • The time we fall asleep, the soundness of our sleep, and the length of time we sleep are linked to the output of epinephrine (adrenaline) by the adrenal glands • When epinephrine levels decline, we tend to fall asleep; when it rises, we tend to wake up • Ultimately, the circadian rhythm is caused by some rhythmical activity of the hypothalamus ◦ EnvironmentalArousal ▪ When we are under high stress, our bodies move into a state of arousal and we often find that we cannot go to sleep or stay asleep ▪ An exciting event often produces increases in arousal and tends to interfere with sleep onset and good sleep ◦ Sleep Deprivation ▪ When people are deprived of a night's sleep, they tend to go to sleep sooner and to stay asleep longer, regardless of environmentally induced arousal Individual Differences in Sleep Cycles • Extraversion is associated with higher body temperature and better performance in the evening • Introversion is associated with higher body temperature and better performance in the morning Other Sleep Rhythms • The Half-Day Rhythm ◦ When subjects are first deprived of sleep and then allowed to sleep for an extended period of time, there is a significant return of slow-wave sleep (SWS) ▪ People tend to become less alert and sleepy around noon • The Basic Rest.Activity Cycle ◦ Abasic rest/ activity (BRAC) cycle that lasts about 90 to 120 minutes has been found in in such waking activities as performance on various sensory tasks, vigilance, and fantasy tasks ▪ Falling asleep is easier when we are in the rest part of the cycle ◦ The regularity of REM every 90 minutes may be controlled by BRAC The Left Brain/ Right Brain Cycle • The right hemisphere tends to be involved in fantasy and intuitive though • The left hemisphere tends to be involved in verbal and intellectual thought ◦ We tend to swing bath between fantasy/ intuitive thought and verbal/intellectual thought ◦ REM tends to be more fantasy/ intuitive and NREM dreams tend to be more verbal/ intellectual Effect of Sleep Loss • Voluntary Sleep Reduction and Sleep States ◦ Studies of voluntary sleep reduction found that subjects were unable to reduce their sleep below 4.5 hours per night, suggests biological limits to sleep reduction ◦ Voluntary sleep reduction to 4.5 to 5.5 hours does not produce significant personality changes or reduce performance ◦ As sleep is reduce, there is no reduction in the amount of state 3 and 4 ▪ There is a significant reduction in REM and stage 2 sleep • Voluntary Sleep Reduction and Feelings of Sleepiness and Fatigue ◦ Sleep deprivation leads to an impaired immune response ◦ Sleep deprivation impairs the functioning of the prefrontal cortex ▪ An area of the brain that has been implicated in the planning and execution of behaviour • Environmental and Cultural Sleep Reduction and Deterioration in Performance ◦ Basic changes that occur as a result of sleep (tend to arise from 3AM to 5AM) ▪ Lapsing • Lapsing refers to the unevenness in performance with sleep deprivation • Sleep-deprived people are slower to respond to a signal or crisis ▪ Cognitive Slowing • There is a reduction in the number (speed) of their cognitive tasks in a self- paced task ◦ Thought to be caused by microsleeps – very short sleep episodes interjected into an otherwise wakeful sleep ◦ Microsleeps tend to increase as sleep deprivation increases ▪ Memory Problems • Areduction in immediate recall which could be caused by a combination of lapses and failure to encode information properly ▪ Vigilance Decrements and Habituation • Performance decrements caused by sleep might not be apparent at the start of the work day but will surface as the shift proceeds ▪ Optimum Response Shifts • In situations where there is limited time to respond with sustained attention to prevent some adverse consequence, sleep deprived people cannot rise to these occasions ◦ Feedback can improve performance, but it is unlikely to override the effects of sleep The Compensatory Model of Sleep Reduction • The compensatory model was developed to explain how people under stress react to complex or demanding tasks ◦ Under high performance demands, people who are sleep deprived attempt to compensate for their lack of ability to fully process information, focusing their attention on high-priority goals while neglecting low-priority goals ◦ According to the model, this requires greater effort, which leads to greater fatigue ◦ To compensate for this, sleep-deprived individuals shift to less complex information processing strategies that demand less dependence on attention/ executive processes Sleep Apnea and Fragmented Sleep • Some people suffer a form of sleep loss because they cannot breathe properly when they fall asleep – called sleep apnea • SWS and REM are critical for not only reducing or eliminating feelings of sleepiness and fatigue but also ensuring that people can perform at optimal levels Some Paradoxical Effects of Sleep Deprivation • Sleep deprivation reduces the high activity that has been linked to depression The Function of REM Sleep Paralysis During REM • In each period of REM sleep, the action of the spinal-cord motor neurons that cause skeletal muscles to contract is inhibited ◦ As a result, the muscles are atonic (without tone); they are paralyzed ◦ Some people experience narcolepsy, which causes them suddenly and unexpectedly to pass from wakefulness to REM sleep without losing consciousness The REM Rebound Effect • People deprives of REM sleep for one or more nights show a REM rebound effect ◦ That is, if allowed to sleep without interruption for a whole night, they spend more time in REM sleep than usual ◦ This indicates that lack of REM for a significant period will trigger some mechanism to override normal sleep schedules REM Deprivation in Animals • The main technique for REM sleep deprivation of small mammals is to place them on a small elevated platform above a tank of water • The rat becomes paralyzed in REM and falls into the water ◦ The experience of falling into the water provides powerful motivation for the rat to avoid REM sleep Motivational Theories of REM • Ellman's Motivation Theory of REM ◦ During both sleep and wakefulness, the positive reward system – also called the intracranial self-stimulation system (ICSS) – needs to be periodically fired ◦ The ICSS system is assumed to maintain motivation when we are not involved in behaviours such as eating, drinking, sex, and aggression, and is turned off when we are involved in these behaviours ◦ How is this related to the content of REM dreams? ▪ The environment is a rich source of stimulation that will periodically fire the ICSS ▪ In sleep, the body needs to generate similar stimulation that will future the ICSS ▪ If the ICSS is to be activated, this stimulation needs to be as vivid and compelling as the environment ▪ The net result is that REM dreams have a vivid and compelling quality, like that of the external environment, but can also have some strange organizational qualities ◦ Lack of REM sleep in infants could slow down the maturational process Neural Organization Theories of REM • REM Sleep, Learning, and the Formation of Memories ◦ REM sleep is deeply involved in learning and the formation of memories in humans and animals ◦ REM is involved in the active integration of complex information with previously learned information ◦ According to consolidation theory, it takes time for recently learned material to be transferred from immediate or short-term memory to long-term memory • REM Deprivation and Learning inAnimals ◦ REM deprivation interferes with learning and retention ◦ Rats are given shuttle box avoidance learning ▪ Put in a box where a tone is presented and half of the grid floor delivers a shock ▪ If animals are emotional when training takes place, REM deprivation disrupts learning • REM Deprivation and Learning in Humans ◦ REM Sleep and Memory ▪ REM deprivation literature shows consistent benefits from REM sleep on the learning and retention of more complex or emotionally loaded tasks ▪ In one study that demonstrated beneficial effects of REM sleep: (Q-sort) • 4 groups: ◦ Group 1:Awake night and day ◦ Group 2: Undisturbed sleep ◦ Group 3: Slept but REM disturbed ◦ Group 4: REM reduced by 25% • Results: REM deprived subjects recalled self-affirming items whereas REM helped facilitate normal-sleep subjects recall items related to personal dissatisfaction • An interpretation is that it takes more time or effort to process emotionally laden information ◦ If sleep deprivation reduces the ability to process information, it follows that people who are sleep deprived would have more difficulty processing views that were inconsistent with their self view but might still be able to process information that was consistent with their self- view • Timing of REM ◦ One recent study looked at declarative memory (paired-associate learning) and procedural memory (mirror-tracing learning) in relationship to the timing of REM sleep ◦ Results showed that although sleep (compared with no sleep) improved both types, early nocturnal sleep (contains 5 more SWS sleep) facilitated declarative learning more than did procedural memory ▪ Later nocturnal (contains twice as much REM as early nocturnal sleep) facilitated procedural memory more than did declarative memory ◦ Declarative memory depends on hippocampal mechanisms supporting consolidation REM Sleep and Stress • REM sleep can dissipate the emotion caused by a stressful or noxious stimulus • Hartmann suggested that during REM sleep, emotional content is reduced or dissipated ◦ The process is very different from how we normally conceptualize consolidation ◦ Instead of playing the same thing over and over, new connections are made ◦ The essence of this theory is when we are no longer under control of the aminergic system, the brain is free to make all kinds of connections ▪ As a result of forming new connections, the piece of information that gave rise to the emotion is shared and distributed throughout the brain REM Sleep and Divergent (Creative Thinking) • Lewin and Galubman have found that REM sleep is characterized by mental activity that is extremely flexible and divergent, rather than integrative and consolidating • Arecent study found that a night of sleep following
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