Section 3 (Sleep) - Biological Rhythms Lecture Notes

Biological Rhythms
Lecture Notes
The Neural Control of Sleep and Wakefulness
Lesions:
Post mortem studies (sleep
sickness in WW2) suggested:
 Posterior hypothalamus =
excessive sleep
 Anterior hypothalamus =
sleeplessness
Brain stem control of sleep and
wakefulness:
 Study conducted in cats to
isolate areas of the brain
which may be involved in
sleep and wakefulness
(Bremner, 1937)
 Lesion at ‘A’ in the cat brain
between inferior and
superior colliculi, disconnects forebrain from most sensory input
 Produces a continuous sleep like state
 Sleep arises when there is a lack of sensory information coming into the brain
 Passive Sensory Theory (Bremer 1936): Sleep due to reduced sensory input
to forebrain
 A lesion at ‘B’ maintains sleep wake cycles – lesion studies in different cats
(Bremer 1937)
 The area between A and B includes a sleep centre (reticular formation
(RF)/reticular activating system (RAS)) which can actively rouse the cortex
independent of external stimuli
 This maintains the sleep-wake cycle