PSYC 2410 Chapter Notes - Chapter 14: Slow-Wave Sleep, Constantin Von Economo, Reticular Formation

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19 Apr 2012
Four areas in the brain involved in sleep
Two areas of the hypothalamus involved in sleep
o The case of Constantin von Economo
WWIviral 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
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
o Only when strong visual/olfactory stimuli were presented could the continuous high-
amplitude, slow-wave activity be changed to a desynchronized EEGa 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
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
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
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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
Reticular REM-sleep nuclei
o 4th 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 sleepa
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
waysand 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
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
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