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Chapter 14

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University of Guelph
PSYC 2410
Boyer Winters

Four areas in the brain involved in sleep  Two areas of the hypothalamus involved in sleep o The case of Constantin von Economo  WWI—viral infection of the brain: encephalitis lethargic  Victims slept almost continuously  Problems with exceissve sleep all had damage in the posterior hypothalamus and adjacent parts of the midbrain  Small group of victims of encephalitis lethargic who had teh opposite sleep-related problem: in constract, they had difficulty sleeping o Victims had damage in the anterior hypothalamus and adjacent parts of the basal forebrain  Conclusion:  Posterior hypothalamus  promotes wakefulness  Anterior hypothalamus  promotes sleep o Studies including lesions and recording brain activity confirmed  Reticular formation and sleep o Bremer severed brain stems of cats between their inferior colliculi and superior colliculi in order to disconnect their forebrains from ascending sensory input  Surgical prep is called: cerveau isolé preparation (literally: isolated forebrain) o Cortical EEG if the isolated cat forebrains was indicative of almost continuous slow-wave sleep o Only when strong visual/olfactory stimuli were presented could the continuous high- amplitude, slow-wave activity be changed to a desynchronized EEG—a low-amp, high frequency EEG o For comparison, Bremer transacted the brain stems of a different group of cats, in the caudal brain stem, disconnecting the brain from the rest of the nervous system  Preparation called: encéphale isolé preparation  Although cut most of the same sensory fibers as the cerveau, normal sleep EEG cycle was not disrupted  Suggests structure for maintaining wakefulness was located somewhere in the brain stem between the two transections  Two important findings suggest this wakefulness structure was the reticular formation  1) shown that partial transections at the cerveau isolé level disrupted normal sleep-wake cycles of cortical EEG only when they severed the reticular formation core of the brain stem o When the partial transections were restricted to more lateral areas, which contain the ascending sensory tracts, they had little effect on the cortical EEG  2) shown that electrical stimulation of the reticular formation of sleeping cats awakened them and produced a lengthy period of EEG desynchronization o Considered 4 findings together:  1) effects on cortical EEG of the cerveau isolé preparation  2) effects on cortical EEG of the encéphale isolé preparation  3) effects of reticular formation lesions and;  4) effects on sleep of stimulation of the reticular formation  Moruzzi and Magoun proposed that low levels of activity in the reticular formation produce sleep and that high levels produce wakefulness  Therefore reticular formation is commonly refered to as reticular activating system, even though maintaining wakefulness is only one of the functions of the many nuclei that it comprises  ReticulathREM-sleep nuclei o 4 area of brain that`s involved in sleep controls REM sleep and is included is part of the caudal reticular formation  Each site is responsible for controlling one of the major indices of REM sleep—a site for the reduction of core-muscle tone, a site for EEG desynchronization, a site for repid eye movements, etc  See Fig. 14.12 for approximate location in caudal brain stem of each of these REM sleep nuclei o Broad implications of various REM-sleep nuclei  People assume that evolutionary pressures have acted to shape the human brain according to our current language and theories  Weakness of assumption: o Brain is organized along different principles, and REM sleep occurs only when a network of independent sstructures becomes active together  Physiological changes that go together to define REM sleep sometimes break apart and go their separate ways—and the same is true of he changes that define slow-wave sleep o Example: during REM-sleep deprivation, penile erections, which normally occur during REM sleep, beging to occur during slow- wave sleep. And during total sleep deprivation, slow waves, which normally occur only during slow-wave sleep, begin to occur during wakefulness  Suggest that REM sleep, slow-wave sleep and wakefulness are not each controlled by a single mechanism  Each state seems to result from interactions of several mechanisms that are capable under certain conditions of operating independently of one another Drugs that affect sleep  Two classes o 1) hypnotic  Increase sleep o 2) antihypnotic  Reduce sleep o 3) those that influence its circadian rhythmicity; the main drug of this class is melatonin  Hypnotic drugs o Benzodiazepines (i.e. valium and Librium) increase drowsiness, decrease the time it takes to fall asleep, reduce the number of awakenings during a night`s sleep, increase total sleep time o 5 complications associated with chronic use as hypnotic drugs  1) tolerance develops to the hypnotic effects; patients gradually need more to maintain the effect  2) cessation of benzodiazepine therapy after chronic use causes insomnia  3) benzodiazepines distort the normal patter of sleep; increase stage 2, decrease stage 4  4) benzodiazepines lead to next-day drowsiness, and increase indicence of traffic accidents  5) benzodiazepines has been shown to reduce life expectancy o Evidence that the raphé nuclei, which are serotonergic, play a role in sleep suggested that serotonergic drugs might be effective hypnotics  Efforts focused on 5-hydroxytryptophan (5-HTP)—the precursor of serotonin— because 5-HTP, but not serotonin, readily passes through the BBB  Injections of 5-HTP rever insomnia producted in some animals but show no therapeutic benefit to human incsomnia  Antihypnotic drugs o 3 classes:  I) cocaine-derived sstimulants  II) amphetamine-derived stimulants  III) tricylclic antidepressants o (above 3 classes) Seem to promote wakefulness by boosting the activity of catecholamines (norepinephrine, epinephrine, and dopamine)—by:  increasing their release into synapses,  by blocking their reuptake from synapses,  or both o (unclassified) codeine and modafinil are less understood o Regular use is risky  Tend to produce a variety of adverse side effects, such as loss of appetite, anxiety, tremor, addiction, and disturbance of normal sleep patterns  May mask pathology that is causing the excessive sleepiness  Melatonin o Hormone synthesized from the neurotransmitter serotonin in the pineal gland  Pineal gland used to be thought of as the seat of the soul  Located on the midline of the brain just ventral to the rear portion of the corpus callosum o Pineal gland has important functions in birds/reptiles/amphibians/fish  Has inherent timing properties and regulates circadian rhym
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