Transcript reticular activating system theory of sleep.

THE PHYSIOLOGICAL AND
BEHAVIORAL CORRELATES
OF SLEEP AND DREAMING
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Outline
1. Three Psychophysiological Measures of Sleep
2. The Five Stages of Sleep EEG
3. REM Sleep and Dreaming
4. Why Sleep?
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5. Comparative Analysis of Sleep
6. Circadian Sleep Cycles
7. Effects of Sleep Reduction
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a. Recuperation Theories
b. Circadian Theories
a. Total Sleep Deprivation
b. REM Deprivation
8. Effects of Long-Term Sleep Reduction
9. Neural Mechanisms of Sleep
10. The Circadian Clock
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a. The Suprachiasmatic Nucleus
b. Mechanisms of Entrainment
Neural Mechanisms of
Sleep
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Bremer
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First major theory of sleep physiology
Proposed a passive theory of sleep
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Sleep occurs because of a reduction of sensory input to
the forebrain
Cut the brainstem between the superior and inferior
colliculi (cerveau isolé)
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produced a state of almost continuous slow-wave sleep
This theory was replaced by the reticular
activating system theory of sleep.
Reticular Activating System
Theory of Sleep
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Three findings contributed to this new theory:
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1) Cutting the brainstem at the caudal end
encephalé isolé) did not affect sleep,
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Damaged the same sensory pathways as the cerveau
isolé preparation
2) The cerveau isolé preparation also impaired
sleep when it transected only the reticular
activating system core of the brainstem – leaving
sensory pathways intact.
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3) Electrical stimulation of the reticular
activating system in sleeping cats
awakened them
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Suggests that slowing of the reticular
activating system leads to sleep.
Increasing the reticular activating system
leads to wakefulness
Three Brain Regions Thought
To Be Involved In Sleep
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1) the raphe nuclei
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A thin cluster of serotonin-releasing
nuclei that lie along the midline of the
caudal reticular formation
Lesions here produce insomnia
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80-90% destruction of raphe nuclei in cats
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Complete insomnia for 3-4 days
2.5 hours after that (all slow wave)
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2) The basal forebrain, including the
anterior hypothalamus
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Patients with small basal forebrain tumors
have difficulty sleeping
Lesions here reduce sleep duration
Single cell recordings have revealed
neurons that increase their activity here
during sleep.
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3) The caudal reticular formation
REM-sleep circuits
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Various sites in the brainstem control
different aspects of REM sleep
The Circadian Clock
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Sleep-wake cycles persist in the absence of
cues from the environment
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Lesions of the medial hypothalamus
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Must be an internal timing mechanism
Where is it?
More specifically the suprachiasmatic nuclei
(SCN), disrupts various circadian cycles
Cells in the SCN maintain circadian cycles
even when surgically cut off from the rest of
the brain
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Internal clock?
Mechanisms of
Entrainment
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Connections between the retina and the SCN
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Cut the optic nerves before they reach the optic chiasm
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Eliminated light and dark entrainment
Cut the optic nerves after they left the optic chiasm
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Light and dark entrainment remains
Led to the discovery of the retinohypothalamic tracts
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Nerve tract that leaves the optic chiasm and goes to the
suprachiasmatic nuclei
Rods and cones not necessary for entrainment.
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From transgenic mouse studies