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Chapter 3

CHAPTER 3 NOTES - Motivation

28 Pages

Course Code
PSYC 2230
Frank Marchese

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CHAPTER 3: PHYSICAL MECHANISMS OF AROUSAL INTRODUCTION • Numerous studies have been constructed that suggest a link between stress and illness • Stress is often conceptually located at the extreme end of a continuum of arousal • Levels of arousal: o If arousal levels are too low - we sleep, or may even be in a coma o At moderate levels of arousal - we are awake and alert o At the high end of the continuum - anxiety and stress appear • Motivation = emotion = arousal, since both motivation and emotion can be regarded as resulting from changes in arousal AROUSAL THEORY • The basic idea underlying arousal theory is that we can understand motivation by viewing it on a continuum of behavioral activation • This continuum ranges from low levels of arousal (coma/sleep) to very high levels (stress) • Arousal theory assumes that behaviour will change as we become more aroused • Some changes in arousal, as from sleep to alert wakefulness, will result in increased efficiency of performance, but other arousal changes, as from alert wakefulness to extreme arousal, will interfere with efficient responding • This reasoning suggests that an optimal level of arousal exists at which behaviour will be most efficient • Inverted U Function: (the curve in figure 3.2) indicates that increasing arousal improves performance only up to a point (the point of optimum arousal), after which continued increases arousal actually being to interfere with responding CHAPTER 3 page 1 • Yerkes-Dodson Law: the arousal-performance relationship • In order to study efficiently for an exam, we must be sufficiently aroused; on the other hand, if we become too aroused by the impending exam, the activation of the stress response may interfere with our studying to the point that we do not learn the material well • Hokanson (1969) noted that the proposed relationship between arousal and performance hold for some types of tasks but not for others o Ex. Freeman (1940) obtained an inverted U function between arousal (as measured by skin conductance) and reaction time, but Hokanson did not obtain inverted U functions for other tasks such as symbol matching or concept formation • Thus the relationship between arousal and behaviour is apparently more complex and task-specific than arousal theory has indicated • What is optimal for one task may not be optimal for some other task • Bremer (1937) has shown that if we cut through the brain stem of an animal between the medulla and the spinal cord (figure 3.3), an animal continues to go through its normal sleep-wake cycle, even though the body has been deprived of all its higher cortical brain tissue o Called the Ecephale Isole • On the other hand, if we cut higher up the brain stem at the level of the colliculi, the sleep-wake cycle is abolished and the animal sleeps constantly, showing no spontaneous waking o Called the Cerveau Isole • Bremer's two cut suggest that some brain structure(s) located between the two cuts control changes in the arousal level involved in moving from sleeping to waking - such a structure is located in the vicinity of the pons CHAPTER 3 page 2 THE RETICULAR ACTIVATING SYSTEM •Discovery by Moruzzi and Magoun (1949) of the role of the reticular activating system in arousal •Reticular Activating System (RAS): Is a group of neurons (nerve cells) located in the brain stem's central core, which runs from the level of the medulla through the thalamus •They found that electrical stimulation of the RAS led to changes in the electrical activity of the cortex(recorded by electrocenephalogram; EEG) that we indistinguishable from changes seen when the external stimuli (ex. Loud noise) were attended •An individual resting quietly shows a regular pattern of cortical electrical activity that can be measured by means of the EEG •The electrical activity of the cells in this relaxed state tends to occur around the same time (ex. They are synchronous) and leads to a pattern of electrical activity known as alpha waves •If we make a loud sound, the individual will open his or her eyes and look around in an alert manner, and the pattern of the EEG during this alert behaviour is very different •The cells of the cortex tend now to be active independently of one another (they are Desynchronized), which leads to a new EEG pattern called beta waves o Beta waves are associated with alert, attentive, and aroused individuals ready to deal with changes in their environment •Moruzzi and Magoun found that stimulation of the RAS led to beta wave activity just as environmental stimuli do •RAS is also responsible for the activation of the organism •Support for this idea provided by: o The RAS receives sensory input from the external sensory systems as well as from the muscles and internal organs ; thus it has the necessary inputs to trigger arousal o Lindsley (1951) cut all the brain structures surrounding the RAS in experimental animals and found that the animals still displayed normal sleep-wake cycles; but when he cut the RAS, leaving everything else intact, the result was a permanently sleeping animal, just as in Bremer's cerveau isol preparation o RAS is known to send fibers diffusely to the whole cortex, therefore, the RAS is a part of the brain circuitry that serves to arouse the organism from sleep to CHAPTER 3 page 3 wakefulness and determine where on the arousal continuum we find ourselves and to what we pay attention Hebb's Theory • Hebb believed that sensory information serves two purposes: 1. To provide information (the cue function of a stimulus) 2. To arouse the individual (the arousal function) • If the individual's cortex is not aroused, the cue function of a stimulus will have no effect (we don’t react to the sound of a passing car when we are asleep because the cortex is not aroused by the RAS) • Sensory stimuli picked up by a person are sent to both the RAS and the cortex via the thalamus • Hebb believed that the stimulus effect at the RAS level is to activate or "tone up" the cortex so that the stimulus information coming from the thalamus can be processed by the cortex • Motivation, for Hebb, is the activation of the cortex by the RAS • It is also known that the cortex sends fibers down to the RAS 1. Thus, the cortex can also activate the RAS and keep arousal high even when external or internal stimulation is low • These downstream connections from the cortex to the RAS could provide a possible explanation for how thoughts might motivate behaviour 1. Ex. Lying in bed and thinking about tomorrow's exam would activate one's RAS, which in turn keeps the cortex aroused, and sleep becomes difficult • Thus, thoughts as well as external stimuli can lead to the arousal of an individual PSYCHOPHSYSIOLOGICAL MEASURES • Arousal theory is based on the assumption that one can measure arousal by monitoring the activity of the brain or changes in the autonomic nervous system and correlating these with changes in behaviour • The lack of substantial correlations between different indexes of arousal has created problems for arousal theory and led Lacey to propose that more than one type of arousal exists • Three arousals: 1. Arousal indicated by a responding organism 2. Autonomic arousal (as shown by changes in bodily functions) 3. Cortical arousal (as evidenced by desynchronizing, fast brain waves) • Lacey proposed that although these three arousals often occur together, they do not have to and are in fact independent 1. Ex. Certain chemicals (ex. Atropine) produce EEG activity akin to sleep in cats and dogs, which nevertheless respond behaviorally in a normal, awake manner 2. Other chemicals (ex. Physostigmine) produce EEG activity like that of an alert animal, but the animal behaves as if drowsy • Comatose patients sometimes show normal EEGs, and normal responding is sometimes observed in individuals with sleeplike EEGs • He also reported several studies indicating that sometimes there is little relationship between central nervous system activity and autonomic changes • As a result of these problems, he proposed that arousal is multidimensional CHAPTER 3 page 4 1. Different situations produce different patterns of somatic responses (ex. Heart rate) •Feedback form the periphery of the body is also important in Lacey's model of arousal 1. Ex. He reported research showing that distention of the carotid sinus (a mechanism in the carotid artery) causes EEG activity to change from alert, high- frequency activity to low-frequency activity generally associated with sleep 2. This change indicates that feedback from various systems of the body can directly influence the arousal system and suggests that bodily systems may also play a role in the length of arousal episodes •Research indicates physiological mechanisms in the midbrain that are involved with arousal of the organism, sleep-wake cycle, and alert attention to the environment PROBLEMS WITH AROUSAL THEORY Problem with arousal theory: 1. The lack of a strong relationship between measures of behavioural, cortical, and autonomic arousal 1. Specific to Lacey's theory, is that it assumes different patterns of bodily responses, yet clear differences remain to be shown o Some studies have indicated that the adrenal hormone norepinephrine may be related to anger or aggression and epinephrine to fear or anxiety o However, further work is needed to determine if Lacey's theory can account for different bodily response patterns o Study by Ekman, Levenson, and Friesen, indicating that changes in the autonomic activities are discernible for the emotions of disgust, anger, fear, and sadness when careful control procedures are employed  They suggest that the autonomic changes may be instigated by contraction of the facial muscles into the universal signals of emotion  Facial muscular patterns may even provide the different bodily response patterns that arousal theory dictates 1. Its general assumption that cortical arousal, as evidenced by EEG, indicates a motivated or emotional state o It is not presently clear that cortical arousal is equivalent to motivated behavior, but even if we were to make that assumption, it is also not clear how this arousal directs behaviour 1. The assumption that an understanding of arousal requires only an understanding of the underlying physiological mechanisms o This may be incorrect - a full understanding of arousal may also require a knowledge of environmental factors and the history of the organism SLEEP •Sleep is thought of as the absence of behaviour or as a low state of arousal •These two assumptions are overly simplified •After sleep deprivation, sleep can become an overpowering motive, easily overriding such motives as hunger and sex CHAPTER 3 page 5 •Carlson, points out that sleep is not a state, but a type of behaviour, one that in fact we engage in for about 1/3 of our lives o Additionally, during some aspects of our sleep process our brains are highly active, similar to when we are awake and alert •Webb found that going without sleep for approximately 48 hours led to problems of sustaining performance on a long, complex task requiring high levels of attention and cognitive processing o There were, however, no clear indications that accuracy of performance declined •Complete deprivation of sleep in rats, causes them to die, perhaps as the result of changes in the immune system GENERAL PROPERTIES OF SLEEP •While most people sleep 7-8 hours per night, others are able to get along with less •Dement reported his study of two individuals who regularly slept less than three hours per night without apparent ill effects •Common sense indicates that we sleep when we are fatigued •This can't be the entire problem, because people confined to bed 24 hours per day sleep approximately the same amount that they would have slept if they had been up and active •Dement suggested that we may sleep because we are at least efficient at certain times •Circadian Rhythms: our bodies go through cyclic changes that often approximate 24 hours in length o Many of these circadian rhythms operate in the lowest part of their cycle during sleep, and Dement proposed that sleep may protect us from engaging in behavior at a time when we are least efficient •Webb and Agnew similarly suggested that sleep is adaptable because it keeps organisms from responding at unnecessary and dangerous times •Meddis made a similar proposal based on an evolutionary perspective Sleep is controlled by at least two separate processes: 1. A homeostatic process that increases our likelihood of engaging in sleep the longer we are awake 2. A circadian process that determines when we wake up Animals and sleep • Different animals spend different amounts of time in sleep •The apparent universal need for sleep in animals is shown by the fact that even fruit flies appear to need sleep and that sleep in these flies is under generic control •Variation in sleep times seems to fit with Webb and Agnew's idea of the adaptiveness of sleep, because different animals would be expected to differ in the durations of time when responding would be disadvantageous to them •It's also suggested that amount of time spent asleep relates to the danger of attack: animals who are likely to be attacked (prey) while asleep generally sleep very little, while predators generally sleep much more •Whales and birds show a specialized form of sleep known as unihemispheric slow- wave sleep (USWS) where one half of the brain sleeps at one time o Whales also show little or no rapid eye movement sleep (REM) seen in other mammals CHAPTER 3 page 6 o The reason such mechanism might have evolved is probably involved sleeping and breathing while in the water, while for birds USWS is thought to serve antipredator function as one eye remains open during USWS Humans and sleep •In humans the length of time spent in sleep decreases with age o Infants (3 days old) sleep 14-16 hours/day o Five-year olds sleep 11 hours/day o 20 year olds sleep 6.5 - 7 hours/day •The most striking thing about sleep in older adults is its variability: o Some older people sleep more than they did when younger, while others considerably less •Ancoli-Isreal and Kripke note that older people report more awakenings during the night and more insomnia •Buysse found that healthy elderly subjects took more daytime naps and experienced shorter and more fragmented nighttime sleep when compared to young adults • He also found that older people went to sleep earlier in the evening •Spielman and Herrera report that older people still sleep approximately 7 hours per day but that sleep is broken up and often includes daytime naps •They also report that there is a decline in both stage 3 and 4 sleep with age and that this decline appears to be more severe in men than in women •The movement from waking to sleep is gradual transition that moves us from waking, though the stage 1 of sleep to stage 2 •If awakened just before entering stage 2 sleep, more than 50% of participants say that they are awake CHAPTER 3 page 7 STAGES OF SLEEP o The alpha wave activity that characterizes relaxed wakefulness occurs before stage 1 A. NREM SLEEP (slow-wave sleep) Stage 1: o The alpha wave activity is replaced by fast, irregular waves of low amplitude o The EEG pattern shows theta wave activity (3.5-7.5 Hz) o This stage lasts 10 to 15 minutes o 5% of total sleep in this stage Stage 2: o The EEG pattern starts to show brief periods of sleep spindles (14 Hz per second waves) and K-complexes o 50% of total sleep in this stage Stage 3: o The EEG pattern shows delta waves activity (<3.5 Hz) o These large slow waves occur during 20 to 50% of the sleep stage o 6% of total sleep in this stage Stage 4: o When the large slow waves now occur more than 50% of time o These slow, high-amplitude waves become dominant, will be reached approximately 30 to 45 minutes after initially falling asleep o After some time in stage 4, the EEG pattern begins to change again to stage 3, then to stage 2, and finally to stage 5 o 14% of total sleep in this stage A. REM SLEEP (paradoxical sleep) Stage 5: o The EEG pattern is a mix of theta, beta, and alpha waves o The individuals eyes begin moving rapidly under the lids o Muscle tone, as measured at the jaw muscle, is very slow o Stage of rapid eye movements and it is the time during sleep when most dreaming occurs o 25% of sleep in this stage REM and NREM Sleep NREM: • Stages 1 - 4 are called NREM sleep because eye movements are not evident during these stages • NREM sleep is also called "slow-wave sleep" to point out the predominance of the high- amplitude, slow delta waves in stages 3 and 4 • Researchers believe NREM sleep serves a restorative function, giving the body a chance to rebuild resources CHAPTER 3 page 8 •Stage 4 sleep decreases with age, showing a sharp decline after age 30 and in some individuals disappearing altogether by age 50 •Hayashi and Endo have also found large reductions in sleep stages 3 and 4 in healthy older persons •Their results indicate a forward shifting of REM toward earlier portions of the night, because of the reduction in stages 3 and 4 •Snoring (if it occurs) will occur in NREM sleep •A person awakened in NREM sleep usually does not report dreaming •Typically he or she reports random thoughts, usually of a nonemotional sort, similar to waking thoughts •Stage 4 and REM sleep have been studied most extensively •A greater proportion of stage 4 sleep occurs early in the night, while most REM sleep occurs later REM: •REM sleep was discovered by Aserinsky and Kleitman in 1955 •Dement noted that reports of dreaming from individuals awakened during REM sleep are approximately 80%, while reports of dreaming from individuals awakened from stage 4 are only about 7% •Some controversy exists concerning the percentage of dreams reported in REM and NREM sleep •Goodenough, concludes that dreaming can occur during NREM and that under some conditions REM sleep occurs when dreams are unlikely (such as in decorticate individuals) •Thus, the use of rapid eye movements as the only index of dreaming is not totally accurate •There may, however, be a difference between dreams reported in REM and NREM sleep o REM dreams are more often bizarre, emotionally loaded, or lifelike o NREM dreams are more nonemotional, random thoughts •The eye movement frequency during REM is related to the activity in REM dreams •Eye movement frequency also seems to be related to dream bizarreness, and in the intensity and emotionality of REM dreams •In REM sleep, there is also a loss of skeletal muscle tone CHAPTER 3 page 9 o This is caused by inhibition of motor neurons in the brain and actually amounts to a temporary paralysis o The loss of muscle tone is the best indicator of REM or "dream" sleep •REM sleep normally occurs about once every 90 minutes throughout the night •REM periods become longer throughout the night, so that by morning one may be in a REM period for as long as an hour •During REM sleep, the EEG activity of the cortex sometimes appears very similar to that of stage 1 sleep and is, in many aspects, similar to the EEG activity seen in a person who is awake and alert •REM produces a mixture of theta and beta wave activity •But even though the electrical activity of the cortex appears to be close to that of waking behaviour, the person is asleep and essentially parlyzed •For this reason, REM sleep has sometimes been called Paradoxical sleep •REM sleep like stage 4 sleep, tends to decline with age early in life; however, REM sleep stabilizes at about age 20 and drops only slightly in old age •According to Carlson, newborn infants spend as much as 70% of their sleep time in REM sleep, which then declines around 30% in older people •The sleep of kittens, puppies, and rat pups is 100% REM at birth •Dement has speculated that REM sleep may organize connections within the brain o He noted that guinea pigs, which are more mature than kitten at birth, show very little REM sleep •The fact that animals show REM sleep in a fashion similar to humans raises the question of whether animals dream o Our knowledge of evolutionary process, lends support to the possibility that some animals, such as primates, and perhaps dogs and cats, do dream DREAMS •Research shows that everyone dreams •This is shown by a "nondreamer" sleep for several nights while connected to an EEG apparatus and to equipment that measures eye movements and muscle tone o The adamant nondreamer falls asleep and eventually enters a period of REM activity o If awakened during this REM period, the nondreamer discovers to great amazement that he or she has been dreaming vividly • The avg. individual spends about 100 minutes per night dreaming o Most dreams are not recalled unless the person is awakened after the dream has occurred o The salience of a dream also appears to influence how likely it will be remembered •Research has shown that although most dreams are brief, they can sometimes last up to an hour •Usually dreams are not emotional, but when emotion is present in dreams, it tends to be negative (65% of emotional dreams are) •Dement noted that dreams early in the night tend to draw on the events of the previous day, while later dreams draw more from stored memories •Dreams also change with age •Herman and Shows, for example, found in a large sample of college graduates that younger persons recall their dreams more frequently than older persons CHAPTER 3 page 10 o They concluded that dream recall diminishes as one get older o They also noted that there were changes in dream content between young adult students and middle-aged adults  Middle-aged adults of both sexes showed significantly less aggressiveness, friendliness, and emotion in their dreams than did the students •REM sleep changes with age - time spend in REM is reduced with age, and REM is less stable - these changes in REM may be related to changes in the recall and content of dreams just noted •Domhoff has proposed a neurocognitive theory of dreams, dreaming is a developmental cognitive achievement that depends upon the maturation and maintenance of a specific network of forebrain structures o This network incorporates a continuity principle whereby personal concerns during the day also appear in one's dreams and a repetition principle whereby the same characters, settings, social interaction, and so forth show up again and again in an individual's dreams, sometimes across decades o He suggests that the continuity between waking thoughts and dreams implies that we are dealing with the same basic issues during both waking and dreaming and that these issues include our conception of ourselves and others •An alternative view of dreaming by Revonsuo proposes that functions to simulate threatening events (threat simulation theory) and allows one to rehearse behaviours associated with perceiving threats and avoiding them o It is proposed to be evolutionary ancient and evolved as a mechanism because it helped out distant ancestors survive and reproduce o It maintains that dreaming is an "off-line" representation of the world and various threats that would be important to the dreamer  Because it is offline, disbelief is suspended while the dreamer rehearses various solutions to the dreamed threat o Example of this was common in hunter-gatherers •Aggression (either attacking or being attacked) is the most common form of behaviour reported in social interactions within dreams •When attacked in a dream, it is usually either by a male (in both men and women) or an animal •Such content would make sense in hunter-gatherer societies where large animals and aggressive males from rivals groups were constantly a threat •Revonsuo also noted that children dream more about animals much more than adults, and the animals they dream about are often not animals that they would come in contact with in their waking environment o About 1/2 of these dreams are about wild animals and in many of these dreams the child dreamer is the victim of the attack •Franklin and Zyphur have proposed an extension to Revonsuo's threat stimulation theory by suggesting that dreams function as "a more general virtual rehearsal mechanism" that is likely to play an important role in the development of human cognitive capacities •Thus, they suggest that dreaming may serve other cognitive processes in addition to simulations of threatening situations SLEEP DEPRIVATION CHAPTER 3 page 11 •The effects of sleep deprivation vary with the type of task •Short tasks performed under sufficient motivation often show only minor effects of sleep deprivation •Long, boring tasks requiring high motivation show deficits in sustaining attention •Sleep deprivation can sometimes have therapeutic properties for some depressed individuals •One complete night without sleep has an antidepressant effect on between 1/3 to 1/2 of depressed patients DREAM DEPRIVATION •Dement found that in order to deprive sleepers of REM sleep, it was necessary to awaken them more and more often •He noted that if was as if a REM pressure was building up that could be expressed only through REM sleep •When he let the subjects sleep normally, he discovered a phenomenon as REM rebound •When dream-deprived subjects were allowed to sleep, they dreamed much more than normal, as if the REM periods were rebounding from their imposed low level •REM deprivation in animals produces a shift in eating patterns relative to light-dark cycle but does not seem to change the amount of food eaten overall •REM deprivation also produces an increase in aggressiveness and sexual behaviours in animals, and REM deprivation rebound effects are reduced by interactional self-stimulation •Ellman proposes that there may be a link between neural structures underlying REM sleep processes and other neural structures subserving motivational processes •There is a link between neurotransmitter called hypocretin or orexin (which is also involved in feeding behaviour) and sleep •REM deprivation can sometimes occur from drug usage • Many drugs (particularly barbiturates, if taken beyond recommended levels) supress REM sleep •If the drugs are abruptly withdrawn, REM rebound occurs, the person shows increased dreaming with vivid nightmares •Amphetamines, which act on the reticular formation to maintain arousal and wakefulness, also supress REM when sleep finally occurs •Webb and Agnew noted that withdrawal of amphetamine leads to prolonged REM rebound, sometimes lasting up to 2 weeks, accompanied with vivid nightmares •Alcohol taken in sufficient doses leads to REM suppression •Vivid hallucinations sometimes experienced in alcohol withdrawal (delirium tremens [DTs]) may result from REM rebound intruding on waking behaviour PHYSIOLOGY OF SLEEP •The autonomic nervous system changes its activity during sleep •During NREM sleep, blood pressure, heart rate, and respiration decline and the veins and arteries dilate (vasodilation) •During REM sleep, blood pressure, heart rate, and respiration increase and become much more variable CHAPTER 3 page 12 • There is an increased flow of blood to the brain and penile erection occurs in males and vaginal secretion in females • In REM sleep, electrical activity of the cortex, changes from slow, high-amplitude delta waves to fast, low-amplitude waves similar to those present during waking • Forebrain areas also exert control over the sleep process BRAIN STEM MECHANISMS THAT PROMOTE AROUSAL • When the reticular system is activated by sensory information or other factors, it in turn arouses the cerebral cortex along two separate pathways 1. One pathway goes from the reticular formation to the thalamus and from there to the cerebral cortex 2. Second pathway goes from the reticular formation to the lateral hypothalamus, the basal ganglia, and the basal forebrain  Connections from the basal forebrain activate the cerebral cortex and the hippocampus • In addition to these structural connections, 5 separate neurotransmitters appear to play a role in changes in arousal: acetylcholine, norepinephrine, serotonin, histamine, and orexin NEUROTRANSMITTERS THAT PROMOTE AROUSAL 1. Acetylcholine: o Acetylcholine-producing cells in the basal forebrain and the pons activate the cerebral cortex and lead to a desynchronized EEG when they are stimulated o Blocking acetylcholine reduces arousal levels o Procedures designed to increase acetylcholine production increases signs of arousal o Acetylcholine increases general arousal of the cortex 2. Norepinephrine: o Norepinephrine-producing cells in the locus coerulus of the pons activate many different areas of the brain including the cerebral cortex, hippocampus, thalamus, cerebellum, and the pons and medulla as well o Production of norepinephrine is high during waking and drops off during sleep - becoming almost zero during REM sleep o It is important for vigilance 3. Serotonin: o Serotonin-producing cells in the raphe nuclei of the pons and medulla also connect to a large number of brain regions including the cerebral cortex, hippocampus, thalamus, hypothalamus, and basal ganglia o These cells are active during waking and decrease during sleep o It facilitates automatic behaviours such as chewing, pacing, or grooming o Carlson believes it is involved with maintaining ongoing activities and suppressing sensory information that might interrupt those activities 4. Histamine: o The cells of the tuberomammilary nucleus of the hypothalamus produce histamine and are connected to many brain regions including the cerebral cortex, thalamus, hypothalamus, basal ganglia, and basal forebrain o Activity in these cells are high during waking and lower during sleep CHAPTER 3 page 13 o The connections of these histamine-producing neurons to the cortex increase arousal directly, while the connections to the basal forebrain indirectly increase arousal via the acetylcholine-producing cells o Histamine is related to attention to environmental stimuli o Incidentally, early anti-histamines used to treat allergies made one feel tired or sleepy because they blocked brain histamine receptors 5. Orexin: o Orexin produced by neurons in the lateral hypothalamus has been implicated in the arousal process o Orexin-producing cells respond primarily when rats were alert and actively engaged with the environment (experiment by Mileykovskiy, Kiyashchenko, and Siegel) BRAINSTEM REGIONS THAT PROMOTE NREM SLEEP • The ventrolateral preoptic area (VLPO) appears to be crucial for delta wave sleep • Destructions of this area in rats led to an absence of sleep and led to death in after 3 days • Simulation of these neurons produces drowsiness and sleep in cats • When animals are deprived of sleep, then allowed to sleep freely, VLPO neurons show an increase in firing rate • The locus coeruleus (LC) and raphe nuclei play a role in sleep: activity in these regions appears to inhibit REM sleep and as their activity drops of during NREM sleep, REM sleep becomes possible NEUROTRANSMITTERS THAT PROMOTE SLEEP • VLPO neurons produce GABA (gamma-aminobutyric acid) as he neurotransmitter • GABA is inhibitory in its action • VLPO, then, promotes sleep through GABA connections that inhibit the activity of several sites already discussed, specifically the locus coerulus, raphe, tuberomammillary nucleus, and the orexiogenic neurons in the later hypothalamus that have arousal properties • In light of the fact that these areas increase arousal levels, it makes sense that inhibition of these areas by VLPA neurons should promote sleep BRAINSTEM REGIONS THAT PROMOTE REM SLEEP • Several groups of cells responsible for REM sleep are located in the upper portion of the pons • Cell groups active during REM sleep: o Sublateralodorsal nucleus (SLD) o Precoeruleus region (PC) o Medial peribacterial nucleus • Cells in these regions secrete several different neurotransmitters, some of which are inhibitory, while others are excitatory • If cells within the peribacterial area are destroyed, REM sleep is greatly reduced • These cells are highly active during REM sleep CHAPTER 3 page 14 BRAINSTEM NEURAL FLIP-FLOPS • Several groups of cells within the brainstem work very much like an electrical flip-flop switch • When one system is active (ex. Waking) it actively inhibits the other system (ex.. Sleep) Figure 3.9 and 3.10 • Inputs from additional cell groups tip the action from one state to the other is relatively rapid once the tipping point is reached • A second independent flip-flop mechanism appears to control transitions from NREM to REM states accounting nicely for the cycling between NREM (stages 1-4) and REM (s
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