1. THE PHYSIOLOGICAL AND BEHAVIORAL CORRELATES OF SLEEP AND DREAMING
Outline
1. Three Psychophysiological Measures of Sleep
2. The Five Stages of Sleep EEG
3. REM Sleep and Dreaming
4. Why Sleep?
a. Recuperation Theories
b. Circadian Theories
5. Comparative Analysis of Sleep
6. Circadian Sleep Cycles
7. Effects of Sleep Reduction
a. Total Sleep Deprivation
b. REM Deprivation
8. Effects of Long-Term Sleep Reduction
9. Neural Mechanisms of Sleep
10. The Circadian Clock
a. The Suprachiasmatic Nucleus
b. Mechanisms of Entrainment

7. Neural Mechanisms of Sleep
Bremer
First major theory of sleep physiology
Proposed a passive theory of sleep
Sleep occurs because of a reduction of sensory input to the forebrain
Cut the brainstem between the superior and inferior colliculi (cerveau isolé)
produced a state of almost continuous slow-wave sleep
This theory was replaced by the reticular activating system theory of sleep.

8. Reticular Activating System Theory of Sleep
Three findings contributed to this new theory:
1) Cutting the brainstem at the caudal end encephalé isolé) did not affect sleep,
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.

9. 3) Electrical stimulation of the reticular activating system in sleeping cats awakened them
Suggests that slowing of the reticular activating system leads to sleep.
Increasing the reticular activating system leads to wakefulness

11. Three Brain Regions Thought To Be Involved In Sleep
1) the raphe nuclei
A thin cluster of serotonin-releasing nuclei that lie along the midline of the caudal reticular formation
Lesions here produce insomnia
80-90% destruction of raphe nuclei in cats
Complete insomnia for 3-4 days
2.5 hours after that (all slow wave)

13. 2) The basal forebrain, including the anterior hypothalamus
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.

15. 3) The caudal reticular formation REM-sleep circuits
Various sites in the brainstem control different aspects of REM sleep

17. The Circadian Clock
Sleep-wake cycles persist in the absence of cues from the environment
Must be an internal timing mechanism
Where is it?
Lesions of the medial hypothalamus
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
Internal clock?

18. Mechanisms of Entrainment
Connections between the retina and the SCN
Cut the optic nerves before they reach the optic chiasm
Eliminated light and dark entrainment
Cut the optic nerves after they left the optic chiasm
Light and dark entrainment remains
Led to the discovery of the retinohypothalamic tracts
Nerve tract that leaves the optic chiasm and goes to the suprachiasmatic nuclei
Rods and cones not necessary for entrainment.
From transgenic mouse studies