THE PHYSIOLOGICAL AND BEHAVIORAL CORRELATESOF 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

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.

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.

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

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)

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.

3) The caudal reticular formation REM-sleep circuits Various sites in the brainstem control

different aspects of REM sleep

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?

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